Symposium FI
Caloric and Multicaloric Materials and Effects: from Fundamentals to Applications
ABSTRACTS
Session FI-1 Theory, simulation and modeling of caloric materials
FI-1:IL01 Caloric Behaviour near Critical and Tricritical Points
A. PLANES, E. MENDIVE-TAPIA, Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona, Catalonia
We present a model for a magnetic material exhibiting magneto-volumic coupling, where the magnetic field serves as the primary field and hydrostatic pressure acts as the secondary field. The phase diagram of the model reveals the existence of a tricritical point for given values of the temperature, magnetic field and pressure. We first show that critical and tricritical behaviours of the isothermal entropy change that quantifies the magnetocaloric effect are different in both cases and we then study the cross-over from critical to tricritical behaviour induced by pressure changes. Next, we demonstrate that near the tricritical point, this entropy change behaves differently depending on the path taken: whether the magnetic field is varied at constant pressure, or the pressure is varied at constant magnetic field. Our results allow us to understand the disparity of exponents that have been reported near tricritical points in different materials, both magnetic and non-magnetic. Furthermore, we show that there is a good agreement with available experimental data reported for for La(FexSi1−x)13 and MnSi compounds.
FI-1:IL02 Fundamental Properties of Compositionally Complex Heusler-Based Compounds: Insights from DFT and XAS
O. MIROSHKINA1, B. EGGERT1, B. BECKMANN2, J. LILL1, D. KOCH2, F. SCHEIBEL2, K. OLLEFS1, W. DONNER2, O. GUTFLEISCH2, H. WENDE1, M.E. GRUNER1, 1University of Duisburg-Essen, Duisburg, NRW, Germany; 2Technical University of Darmstadt, Darmstadt, Hessen, Germany
Compositionally complex alloys (CCA) consisting of 5 or more elements provide a new route to tune mechanical stability and functional properties. Controlling the elemental proportions directly affects the electronic structure, which in turn governs the structural behavior. Here, we demonstrate how chemical and magnetic complexity can be exploited to tailor functionality of Ni(-Co)-Mn(-Fe)-based Heuslers and related CCA. We combine density functional theory (DFT) and x-ray absorption spectroscopy (XAS) to focus on the impact of particular p- and d-element substitutions on the electronic, magnetic, and structural subsystems. L-edge XAS reveals fingerprints of d-d hybridization and determines magnetic configurations. Magnetic order is governed by delicate balance of competing FM and AFM exchange between d-metals, but DFT shows it can be tuned by p-element [1]. K-edge XAS supported by phonon studies reveals partial disorder not only in all-d-metal Ni(-Co)-Mn-Ti but also in conventional Ni2MnSn [2]. Thus, we demonstrate the particular role of p- and d-elements in tailoring the properties of CCAs, paving the way for their rapid transition to functional applications.
[1] F. Cugini et al., Phys. Rev. B 105, 174434 (2022) [2] O. Miroshkina, B. Eggert et al., Phys. Rev. B 106, 214302 (2022).
FI-1:IL03 Searching for New Magnetocaloric Materials—A High-Throughput Approach
R. MARTINHO VIEIRA, Uppsala University, Uppsala, Sweden; T. BJÖRKMAN, Åbo Akademi, Åbo, Finland; O. ERIKSSON, H.C. HERPER, Uppsala University, Uppsala, Sweden
The increasing interest in magnetocaloric materials for magnetic cooling devices has spurred an intensive search for new compounds based on abundant and non-hazardous materials. High-throughput (HT) studies, based on ab initio calculations, spin-dynamics simulations, and existing databases, play a crucial role in identifying promising materials and guiding material optimization. To efficiently screen large bodies of data, careful selection of screening parameters that balance accuracy and computational cost is essential. Given their potential as magnetocaloric materials and their strong magnetism-lattice coupling, we focus our search on systems with potential magneto-structural transitions. A key parameter for evaluating these materials is the entropy change between magnetic phases. Drawing on insights from benchmark studies of magnetocaloric systems with distinct magnetic transitions—such as FeRh and Gd—we design a HT workflow and apply it to two well-established databases, the Materials Project and Alexandria. These databases already contain first-principles data, thus they enable accelerated candidate screening. Furthermore, we explore the use of machine-learning models to predict relevant properties, discussing their potential to expedite similar searches in the future.
FI-1:IL04 Stress-Induced Martensitic Transformation in Ni₂MnGa Single Crystals
L. RIGHI, Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parma, Italy
Ni-Mn-based Heusler alloys represent a leading class of multifunctional materials, being the martensitic transformation the key-factor for caloric effects. Recently Heusler alloys demonstrated interesting promising elastocaloric effects for solid-state cooling driven by stress-induced phase transitions, potentially involving the coupling between structural and magnetic degrees of freedom. The investigation of the martensitic transition under mechanical compression is therefore essential to gain knowledge required for the rational exploitation of the multicaloric effects. In this study, we probe the stress-induced martensitic transformation in single-crystal Ni₂MnGa by applying uniaxial compression along the <001> and <110> cubic directions. High-resolution neutron diffraction experiments conducted at the ISIS facility reveal that a compressive stress exceeding 250 MPa along the <001> axis triggers a transition from the cubic austenite to an incommensurate martensitic phase with a modulation vector q = (δ,0,0) and δ ~ 0.42. The compression along the <110> direction not only increases the martensitic transition temperature but also shrinks the stability region of the pre-martensitic phase. These findings provide essential insights into the stress-mediated phase evolution in Ni₂MnGa.
FI-1:L05 Modelling the Dynamics of the Martensitic Transformation in Ni₂MnGa with Machine-learning Force-fields
M.E. GRUNER, University of Duisburg-Essen, Duisburg, Germany; M.J. BRUCKHOFF, University of Duisburg-Essen, Duisburg, Germany
Functional ferroic properties of Ni-Mn-based Heusler alloys depend on the presence of hierarchically twinned, modulated structures in the martensitic phase. These structures can be interpreted as an adaptive, self-organized arrangement of [101]-aligned nanotwins consisting of non-modulated tetragonal building blocks, while density functional theory (DFT) suggests that these martensites can be accessed via a downhill transformation path from cubic austenite. This is supported by a reconstruction of the Fermi surface, which softens the [101] transversal acoustic phonons of the austenite. However, modeling phase free energy surfaces at finite temperatures or the dynamics of the martensitic transition as probed in recent ultrafast laser heating experiments [1] is out of reach for pure first-principles approaches. Machine-learning force fields (ML-FF) trained on DFT data offer a unique opportunity to model materials with such electronic instabilities in a classical atomistic simulation setup. At the example of Ni₂MnGa, we explore the perspective to overcome the limitations of DFT using ML-FF in classical molecular dynamics.
[1] Y. Ge, F. Ganss, D. Schmidt, D. Hensel, M. J. Bruckhoff, S. Sadashivaiah, B. Neumann, M. Brede, M. E. Gruner, P. Gaal, K. Lünser, S. Fähler, arXiv:2509.06513.
FI-1:IL06 Ab initio Understanding of Large Caloric Effects around First-order Magnetic Phase Transitions with Low Hysteresis
E. MENDIVE TAPIA, Universitat de Barcelona, Barcelona, Spain; D. BOLDRIN, University of Glasgow, UK; WEI LIU, K. SKOKOV, O. GUTFLEISCH, TU Darmstadt, Germany
Caloric effects in magnetic materials are particularly pronounced near first-order (discontinuous) magnetic phase transitions [1]. However, such transitions often exhibit undesirable hysteresis. While magnetovolume coupling is known to drive first-order behavior [2], purely electronic mechanisms remain less well understood. Using the disordered local moment (DLM) framework within density functional theory (DFT) [3–5], we calculate temperature-dependent magnetic and caloric properties to elucidate how electronic and magnetovolume interactions cooperate to produce first-order transitions. Results are presented for representative systems, including Mn₃AN antiferromagnets [5], Eu₂In [6], and van der Waals ferromagnets [7], along with new findings for non-hysteretic first-order ferromagnetic transitions quantified using DLM-DFT for the first time. Comparison with experimental data allows us to identify key factors linking the origin of first-order character of magnetic transitions to minimal thermal hysteresis.
[1] Phys. Rev. Lett. 78, 4494 (1997). [2] Phys. Rev. 126, 104 (1962). [3] J. Phys. F: Met. Phys. 15, 1337 (1985). [4] J. Appl. Phys. 127, 113903 (2020). [5] Phys. Rev. B 105, 064425 (2022). [6] Phys. Rev. B 101, 174437 (2020). [7] Appl. Mater. Today 44, 102749 (2025).
Session FI-2 Preparation and characterization of caloric materials
FI-2:IL07 Simultaneous Application of Pressure and Electric Field in Ferroelectric Materials
M. ZENG1, M. ROMANINI1, I. GORICAN2, S. DRNOVSEK2, H. URSIC2,3, A. SALVATORI1, M. BARRIO1, S. LOEHLE4, N. OBRECHT4, C. ESCORIHUELA-SAYALERO1, C. CAZORLA1, A. TORELLÓ1, P. LLOVERAS1, J.-L. TAMARIT1, 1Group of Characterization of Materials, Department of Physics and Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, Barcelona, Catalonia, Spain; 2Electronic Ceramics Department, Jozef Stefan Institute, Ljubljana, Slovenia; 3Jozef Stefan International Postgraduate School, Ljubljana, Slovenia; 4TotalEnergies OneTech, Solaize, France
Solid-state caloric effects for sustainable cooling and heating are promising alternative methods to conventional classical vapor-compression cycles of greenhouse gases and inefficient fuel-burning heaters. Among the panoply of caloric effects, barocaloric effects (BCE) driven by hydrostatic pressure, are particularly promising due to the large adiabatic temperature changes (10 K) and the isothermal entropy changes (1>00 J K-1 kg-1). Despite these hopeful values, BCE suffers from the ability to substantially modify the temperature range, mainly related to the sensitivity of the transition temperature with pressure, as well as the required large pressure shifts due to the irreversibility associated with the hysteresis of involved first-order phase transitions. In this communication we highlight the potential of ferroelectrics as multicaloric materials driven simultaneously by pressure (p) and electric (E) fields. We have analyzed the T-p-E as well as the S (entropy)-p-E 3D thermodynamic spaces for the archetypal lead scandium tantalate (PST) ceramics near the ferroelectric phase transition through new experimental systems. From them, the barocaloric and electrocaloric effects reveal the potential for enhanced caloric performance due to the additional cross-coupling contributions.
FI-2:IL08 Caloric Properties of Spin Crossover-Polymer Compounds
K. LÜNSER1,2,3, C. SALAZAR MEJÍA4, T. GOTTSCHALL4, E. KAVAK5, K. GÜRPINAR6, B. EMRE5, O. ATAKOL6, M. PORTA3, A. PLANES3, P. LLOVERAS7, J.-LL. TAMARIT7, E. STERN-TAULATS3, LL. MAÑOSA3, 1Institute for Energy and Materials Processes – Applied Quantum Materials, University Duisburg-Essen, Duisburg, Germany; 2Research Center Future Energy Materials and Systems (RC FEMS), University of Duisburg-Essen, Duisburg, Germany; 3Universitat de Barcelona, Barcelona, Catalonia, Spain; 4Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany; 5Department of Engineering Physics, Faculty of Engineering, Ankara University, Ankara, Turkey; 6Department of Chemistry, Faculty of Science, Ankara University, Ankara, Turkey; 7Universitat Politècnica de Catalunya, Barcelona, Catalonia, Spain
Spin crossover materials (SCO) can undergo a transition between low-spin and high-spin states, changing their magnetization, volume and optical properties during the transition. Many SCO transitions are first-order and involve a considerable latent heat, therefore, giant barocaloric effects as well as magnetocaloric effects have been reported for different SCO complexes in the past. However, their powder nature so far prevented their use as elastocaloric materials. Here, we report magneto-, baro- and elastocaloric effects in the spin crossover complex [Fe(L)2](BF4)2, [L = 2,6di(pyrazol-1-yl)pyridine], embedded into a polymeric matric of polyvinyl chloride (PVC). We demonstrate remarkable elastocaloric effects associated with the SCO transition: we measure isothermal entropy change of ΔS = 3.1 Jkg−1K−1 for stresses as low as σ = 8 MPa and very low strain values ε = 0.3%. The required stresses are one order of magnitude lower than those required for shape memory alloys, and strains are several orders of magnitude lower than those of elastomers. Therefore, SCO compounds are interesting candidates for elastocaloric-based cooling technologies, especially in applications requiring low applied stresses.
K. Lünser et.al., Nat. Comm. 15, 6171, 2024
FI-2:IL09 Microstructure Design in Magnetocaloric Materials
XUEFEI MIAO, YONG GONG, Nanjing University of Science and Technology, Nanjing, P.R. China; L. CARON, Bielefeld University, Bielefeld, Germany
The implementation of magnetocaloric effect is hindered by some challenges in the magnetocaloric materials, e.g., low thermal conductivity, poor mechanical property and large irreversibility of the magnetic transition. Here we present a few examples to illustrate that microstructural manipulation offers a potential solution to the aforementioned challenges. We employed finite-element simulations to design and optimize the microstructure of the (Mn,Fe)2(P,Si)/Cu magnetocaloric composites. The optimized microstructure is characterized by continuous Cu networks within the (Mn,Fe)2(P,Si) magnetocaloric matrix. This microstructure was experimentally realized by hot pressing (Mn,Fe)2(P,Si)/Cu core/shell powders that were synthesized by electroless Cu plating. The magnetocaloric composites with such a novel microstructure exhibit a high λ of 20.4 Wm-1K-1 and a large maximum compressive strength of 570 MPa, which are the best comprehensive properties for room-temperature magnetocaloric materials ever reported. We have also demonstrated that the construction of a textured microstructure can significantly improve the reversibility and mechanical stability for magnetocaloric materials showing a first-order magnetostructural transition (MST).
FI-2:IL10 Multifunctional High Entropy Alloys for Caloric Applications
V. FOURNÉE1, D. SIHOM KWEKAM1, G. LENGAIGNE1, J. LEDIEU1, J. VALENTIN1, P. BOULET1, S. MIGOT1, J. GHANBAJA1, S. SEMSARI PARAPARI2, S. ŠTURM2, S. FABBRICI3, F. CUGINI3,4, M. SOLZI3,4, F. ALBERTINI3, 1Institut Jean Lamour, CNRS-Université de Lorraine, Nancy, France; 2Jozef Stefan Institute, Department for Nanostructured Materials, Ljubljana, Slovenia; 3Institute of Materials for Electronics and Magnetism (IMEM), CNR, Parma, Italy; 4Department of Physics, University of Parma, Parma, Italy
High-entropy alloys (HEAs), in contrast to conventional alloys and intermetallics, mix five or more elements at equal or near-equal compositions. In principle, they form an ideal solid solution stabilized by a high entropy of mixing. The huge compositional space of HEAs offers opportunities to discover new functional materials with improved properties. Inspired by recent reports on rare-earth free HEAs, we present new results on the structure and magnetocaloric performances of some FeMnNiGeSi and FeMnNiCoGeSi HEAs. STEM indicates a perfect solid solution in the post-annealed samples, meaning that all atomic species randomly occupy all the crystallographic sites. We investigate the effect of Mn- and Co-doping, demonstrating the possibility to tune the transition temperature towards room temperature. The magnetization versus field M(H) curves reveal magnetic hysteresis at temperatures close to the transition reflecting a field induced first-order magnetostructural transition. The magnetocaloric effect is evaluated indirectly using the Maxwell relation and by direct adiabatic temperature change measurements. Isothermal entropy change as large as about 40 J.kg-1.K-1 is attained at 5 T, while the thermal hysteresis is also reduced down to 7 K upon stress relief.
FI-2:IL11 High Pressure Characterization of the Magnetoelastic Phase Transitions in Magnetocaloric Materials
L. CARON, Department of Physics, Bielefeld University, Bielefeld, Germany & Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
Magnetic refrigeration is considered one of the best alternatives to gas-compression based refrigeration due to its high efficiency and environmentally friendly materials. It relies on materials presenting strong magnetoelastic couplings which give rise to large magnetocaloric effects. In these materials the phase transition can be triggered not only by temperature and field but also by pressure. Since the exchange interaction is a function of the interatomic distance, pressure offers a clean way of probing the nature of the magnetoelastic coupling. In this work I will report high pressure measurements of the magnetic and structural properties in some promising and intriguing magnetocaloric materials systems such as Fe2P-based compounds, Fe2Hf-based compounds and NiMn-based Heusler alloys, and what we can learn from such experiments.
FI-2:IL12 Bulk Ceramics and Thick Films for Caloric Applications
H. URŠIČ1,2, M. D’ANGELO1, V. REGIS1,2, I. GORIČAN1,2, 1Electronic Ceramics Department, Jožef Stefan Institute, Ljubljana, Slovenia; 2Jožef Stefan International Postgraduate School, Ljubljana, Slovenia
Many activities in solid-state cooling research focus on one of the caloric effects - electrocaloric (EC), magnetocaloric (MC), or mechanocaloric. Among these, the EC effect is triggered by voltage, which is readily available. In this contribution, we will discuss the Pb(Sc0.5Ta0.5)O3 and Pb(Mg1/3Nb2/3)O3-based ceramics and thick films for electrocaloric applications. The ceramic powders were prepared by mechanochemical synthesis, and the ceramics exhibit a much higher EC temperature change than the columbite-derived counterpart. A detailed study of the microstructure revealed that the clear grain boundaries and the intragranular MgO inclusions resulted in an almost doubled electrical breakdown field of the mechanochemically synthesized ferroelectric 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 (PMN–10PT). We continue by describing the use of synthesized powders in various applications, such as in thick-film form for flexible electronics and in applications where the material is exposed to high neutron and γ irradiation, namely, medical accelerators, nuclear reactors, and space technologies. Further, we will discuss the preparation of caloric elements that exhibit both EC and MC effects, namely Pb(Fe0.5Nb0.5)O3–BiFeO3 ceramics, as well as the multicaloric composite thick film based on the EC PMN.
FI-2:L13 Development of Copper Based Shape Memory Alloy for Elastocaloric Cooling Applications
JUN CUI, Department of Materials Science and Engineering, Iowa State University, Ames, IA, USA
Copper-based shape memory alloys (SMA) display martensitic transformation over a wide range of temperatures. In addition to its low cost, Cu-SMA alloy is known for its low transformation stress with reasonable latent heat favoring elastocaloric applications. The current state-of-the-art alloy is NiTi alloy, which, unfortunately, is prohibitively expensive. The talk reports our progress in a high-throughput route in developing Cu-SMA compositions for improved elastocaloric applications. New combinatorial materials search methods have been developed, and past time-consuming steps have been adequately addressed. New alloy compositions were benchmarked with a large latent heat of 8.4 J/g and a low hysteresis of 18°C. On selected composition, the effect of alloying on the yield strength of the alloy and the application of thermomechanical processing to improve and stabilize the alloys’ mechanical properties will be discussed. Thermomechanical processing effectively tunes the transformation stress and strain, resulting in a Cu-SMA with 300 MPa critical transformation stress and at least 4% recovery strain.
FI-2:L14 Exploring the Elastocaloric Potential of NiMnTi Alloys
F. VILLA1,2, E. BESTETTI1, ZEJUN DENG2, L. RIGHI3, D. SALAZAR4, N. BENNATO1, F. PASSARETTI1, R. CASATI2, E. VILLA1, 1CNR ICMATE, Lecco Unit, Lecco, Italy; 2Politecnico di Milano, Milano, Italy; 3Università di Parma, Parma, Italy; 4BCMaterials, Leioa, Spain
The use of caloric materials for solid-state cooling applications presents a promising and sustainable alternative to traditional vapor compression-based refrigeration methods. Among elastocaloric materials, superelastic shape memory alloys (SMAs) stand out, owing to the reversible stress-induced martensitic transformation which involves a high latent heat. NiMnTi-based alloys show remarkable elastocaloric performance due to the large unit cell volume change during the martensitic transition and to their promising mechanical properties. In this work, polycrystalline NiMnTi alloys were produced by means of different casting methods and the correlation between the process conditions and the microstructural, thermal and mechanical properties was investigated. The mechanical characterization represented the core of the work: both isothermal and quasi adiabatic mechanical tests were carried out alongside strain recovery measurements, in order to determine the elastocaloric parameters of the NiMnTi alloys produced through different casting methods. The current study contributes to the expansion of the knowledge on polycrystalline NiMnTi alloy produced by means of cost-effective casting processes in order to lay the foundations for further development of effective elastocaloric alloys.
FI-2:L15 Revealing Complex Magnetic Interactions in Fe2P-based Compounds: A Study using Mössbauer Spectroscopy and Neutron Diffraction
K.K. THILAKAN, S. GHORAI, WEI LIU, L. HÄGGSTRÖM, F. LINDGREN, V. POMJAKUSHIN, P. BERAN, O. GUTFLEISCH, P. SVEDLINDH, J. CEDERVALL, Department of Chemistry - Ångström Laboratory, Uppsala University, Uppsala, Sweden Institute of Materials Science, Technical University of Darmstadt, Darmstadt, Germany; Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden; Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Villigen, Switzerland; European Spallation Source ESS ERIC, Lund, Sweden Nuclear Physics Institute, ASCR, Rez, Czech Republic; Department of Materials Science and Engineering, Uppsala University, Uppsala, Sweden
Developments in RT magnetic refrigeration started with the discovery of the giant magnetocaloric effect and can be used to achieve energy efficient cooling. One of the most promising materials, (Fe,Mn)2(P,Si), is based on the compound Fe2P. Fe2P is a hexagonal, ferromagnetic (FM) compound with two Fe and two P positions in its crystal structure. The different atomic positions make it possible to tune the physical properties by chemical substitutions, creating various compositions of (Fe,Mn)2(P,Si). A systematic study of the transition from Fe2P to FeMnP0.5Si0.5 – Fe2-2xMn2xP1-xSix – have been undertaken with magnetometry and Mössbauer spectroscopy to understand the magnetic changes during substitution. A dramatic change in the magnetism were detected close to Fe2P, i.e. low values of x, where the ferromagnetic ordering is lost in favour of an antiferromagnetic (AFM) structure. Further substitutions (higher values of x) retains the FM interactions and the magnetic cooling power increases. The AFM ordering have been studied with neutron diffraction and show a complex, incommensurate, sinusoidal AFM spin-wave with a propagation vector k = (~0.22(1) 0 0). I will describe how the AFM structure were resolved and the impact of our findings for magnetic cooling applications.
FI-2:IL16 Additive Manufacturing of Magnetocaloric and Thermomagnetic Materials via Polymer based Composite Filaments
V. FRANCO, Multidisciplinary Unit for Energy Science, University of Seville, Seville, Spain
While additive manufacturing (AM) is transforming materials design by enabling complex geometries of functional devices, two potential drawbacks might emerge, depending on the printing technology used. On the one hand, in the case of laser-based additive manufacturing, the active phases of the powder might be transformed and performance of the final part might be compromised. On the other hand, fused deposition modeling (FDM), with a much lower processing temperature, does not present this limitation, but achieving good homogeneity in the filaments is crucial to be able to obtain good printed parts. Our recently proposed methodology enables precise and homogeneous particle dispersion while overcoming polymer chemistry constraints, offering a versatile route to a broad range of functional magnetic filaments. Using this approach, we produced magnetic filaments, including magnetocaloric La(Fe,Si)13H, Ni2MnGa, etc., composites, which retain key properties required for solid-state magnetic refrigeration. These advances demonstrate the potential of FDM to integrate materials innovation with device functionality for future magnetocaloric systems.
FI-2:IL17 Thin Film Combinatorial Studies of Thermomagnetic Materials
N.M. DEMPSEY, A.A. BELEZA, T. PAKAM, W. RIGAUT, P. LE BERRE, H. JABALLAH, L. FINK, R. HAETTEL, L. RANNO, T. DEVILLERS, Univ. Grenoble Alpes, CNRS, Institut Néel, Grenoble, France
Combinatorial studies based on the preparation and characterisation of compositionally graded thin films are being used for the screening and optimization of a range of functional materials, including magnetic materials. When combined with Machine Learning (ML), such high-throughput film-based studies hold much potential to guide data driven design of new materials. In this talk I will outline our recent developments around high throughput characterisation as well as data handling and analysis. I will then present our on-going studies of the effect of element substitution and annealing conditions on both structural and magnetic properties of compositionally graded thin films of different families of magnetocaloric materials. I will finish up by briefly outlining the potential of combining high throughput experimentation and data analysis for the accelerated development of functional magnetic materials with enhanced performance and / or reduced dependence on critical elements.
This project has received funding from the European Union under grant agreements 101119852 (Heat4Energy) and 101161135 (MAGCCINE).
FI-2:IL18 Multi-caloric Cooling for Room Temperature and Cryo-applications
O. GUTFLEISCH, A. AUBERT, A. DÖRING, B. BECKMANN, F. SCHEIBEL, WEI LIU, S. GHORAI, K. SKOKOV, TU Darmstadt, Functional Materials, Darmstadt, Germany
Magnetic refrigeration with enhanced energy efficiency and environmental sustainability is emerging as a viable and sustainable alternative to conventional gas-compression refrigeration. We provide an overview of our recent advancements in developing and optimizing magnetocaloric materials for applications in refrigerators operating at ambient temperatures and for cryogenic conditions (hydrogen liquefaction). The talk also examines the trajectory from laboratory research to industrial implementation of the various classes of magnetocaloric materials (rare earth metals (R) and alloys, La(FeSi)13, Heusler alloys, RCo2, R2In, etc.). Key issues to be discussed include achieving maximum adiabatic temperature change and isothermal magnetic entropy change, reducing thermal hysteresis in materials first-order magneto-structural transitions, enhancing thermal conductivity, corrosion resistance, mechanical properties and improving durability and scalability. We focus further on multi-stimuli responsive caloric materials with a strong interplay between their structural, magnetic, and electronic degrees of freedom. Our work shows a new pathway to disentangle the subsystems to understand the driving forces of the first-order phase transition. For this, we introduce our original experimental setup for simultaneous measurement of macroscopic physical properties (magnetization, magnetostriction, resistivity, temperature change) in isothermal or adiabatic conditions as well as microscopic properties such as element-specific hysteresis at the ID12 beamline of the ESRF.
FI-2:L19 Fabrication of Pb(Sc0.5Ta0.5)O3 Thick Films by Powder Aerosol Deposition
M. D’ANGELO1, V. REGIS1,2, I. GORIČAN1,2, S. DRNOVŠEK1, H. URŠIČ1,2, 1Electronic Ceramics Department, Jožef Stefan Institute, Ljubljana, Slovenia; 2Jožef Stefan International Postgraduate School, Ljubljana, Slovenia
In recent years, electrocaloric (EC) cooling emerged as an environmentally friendly solid-state alternative to vapor-compression systems. The B-site ordered Pb(Sc0.5Ta0.5)O3 (PST) ceramic is one of the most studied inorganic EC materials, which exhibits a maximum EC temperature change of 3.7 K applying a field of 40 kV∙cm-1 at room temperature. The powder aerosol deposition (PAD) method enables the preparation of dense films onto various substrates, such as polymers, which opens up potential applications in microelectronics. In this work, we prepared PST thick films on gold-coated polyimide substrates using the PAD method. We prepared the B-site ordered PST pellets that were ground and milled to obtain the B-site ordered powder for PAD. The prepared films were highly dense, with the relative density of ~99%, and the B-site order parameter of 0.89 was maintained after deposition. The functional properties of the PST films will be discussed in this contribution. Furthermore, the preparation and characterization of lead-free PAD films based on Ba0.65Sr0.35TiO3 will also be addressed.
Session FI-3 Functional characterization of caloric materials
FI-3:IL20 New Versatile Instruments to Measure Element-specific and Macroscopic Hysteresis at ID12 of the ESRF
A. AUBERT, Functional Materials, TU Darmstadt, Darmstadt, Germany
In this presentation, I will introduce new instruments which have been implemented at the beamline ID12 of the European Synchrotron Radiation Facility (ESRF), in the framework of the “ULMAG” project. These instruments offer the ESRF users a unique possibility to measure under strictly the same experimental conditions the element-specific X-ray absorption spectroscopy (XAS)/ X-ray magnetic circular dichroism (XMCD), high-resolution XRD simultaneously with the measurement of various macroscopic properties (magnetization, volume changes, magnetocaloric properties, resistivity etc.), all as a function of magnetic field (up to 17 T) and temperature (5–325 K) [1,2]. To demonstrate the potential and features of these scientific instruments, we present two case studies: (1) FeRh, which has a first-order anti-ferromagnetic to ferromagnetic transition around room temperature and (2) HoCo2, which exhibits a first-order ferrimagnetic to paramagnetic transition. These two cases demonstrate new horizons for studying the physics of magnetic materials, where the interplay between the magnetic, structural, and electronic subsystems is essential.
[1] A. Aubert et al., IEEE Trans. Instrum. and Meas, 71, 1-9, 6002409 (2022). [2] A. Aubert et al, J. Synchrotron Rad. 32, 321–330 (2025).
FI-3:IL21 Recent Developments in Magnetocaloric Measurements
F. CUGINI1,2, G. GARULLI1, M. SOLZI1,2, 1University of Parma, Parma, Italy, 2IMEM-CNR Institute, Italy
Thermomagnetic (TM) energy conversion technologies, such as magnetic refrigeration and TM generation for waste heat recovery, are emerging as promising solutions with strong potential to contribute to the sustainable transition of our society. These systems operate through TM cycles, which rely on suitable magnetocaloric (MC) materials. The selection and optimization of these materials are mainly guided by their magnetic and thermodynamic properties. Critically, this process depends on accurate and reliable characterization of their MC behavior, which is essential for enhancing the performance of TM technologies. This contribution presents a comprehensive and critical review of methods used to characterize MC materials. Both direct and indirect methods for evaluating the MC effect and the potential magnetic work associated with TM cycles are discussed. A comparative analysis of the material requirements for magnetic refrigeration and TM energy generation is provided, highlighting the similarities and differences in their characterization approaches. Furthermore, the importance of assessing material performance under operating conditions is emphasized, as factors such as reversibility and degradation can significantly influence their effective functionality.
FI-3:L22 Mechanocaloric Effects in Spin Crossover Complexes subjected to Uniaxial Load and Hydrostatic Pressure
L. MAÑOSA, E. STERN-TAULATS, A. PLANES, M. PORTA, E. VIVES, Universitat de Barcelona, Barcelona, Catalonia; K. GURPINAR, S. BOZUKS, E. KAVAK, B. EMRE, O. ATAKOL, Ankara University. Ankara, Turkey; K. LÜNSER, Universität Duisburg-Essen, Duisburg, Germany; A. SALVATORI, P. LLOVERAS, J.L. TAMARIT, Universitat Politècnica de Catalunya, Barcelona, Catalonia
Materials undergoing a first-order phase transition with large entropy and volume changes often exhibit barocaloric effects (BCE). The strong sensitivity of these transitions to hydrostatic pressure enables giant isothermal entropy and adiabatic temperature changes. However, using BCE materials in cooling devices is challenging due to the complexity of applying hydrostatic pressure. Uniaxial loads, in contrast, are easier to implement. This raises the possibility of triggering similar giant effects in BCE materials via uniaxial stress. Thermodynamics shows that the volume change at the transition couples to other stress components, so the transition temperature is expected to shift under uniaxial load. In this work, we use a custom experimental setup to study the mechanocaloric response of a spin crossover complex under uniaxial compression. Large entropy and temperature changes are achieved at moderate stress. The mechanocaloric effect compares well with BCE in the same compound, demonstrating the feasibility of inducing giant caloric effects in BCE materials using uniaxial stress.
FI-3:L23 Dynamics of the Phase Transformation in a Giant Magnetocaloric Material along T- and B-scans
F. GUILLOU, F. VEILLON, V. HARDY, Normandie University, ENSICAEN, UNICAEN, CNRS, CRISMAT, France; B. HUHE, Inner Mongolia Normal University, China
The development of first-order transitions at small temporal and spatial scales remains a rich and stimulating field of study, with magneto-structural transformations in giant magnetocaloric materials of particular interest. The dynamics of these phase transformations leads to unconventional heat exchanges, which remain challenging to characterize and model. We investigated the time‐dependent heat exchange during the phase transformation of a benchmark magnetocaloric material. Starting from basic thermal equations, we derived and experimentally validated a unified thermal model that describes the Peltier DSC’s response under both temperature and field scans. This model captures all stages of the transformation (pre‑transition, transition, and post‑transition) and allows the determination of key thermal parameters. The relevance of the model is supported by several results such as the measured latent heat and post-transformation relaxation times. Our analysis revealed several noteworthy phenomena, such as a scaling law applicable to the variations in the scan rate of either T or B (below limiting values beyond which the transformation dynamics escape the model), several relaxation times of different nature, and qualitative differences between T and B scans.
FI-3:L24 Advancing Mechanocaloric Cooling Solutions through 3D Printing of Superelastic Lattice Structures
E. BESTETTI, F. VILLA, E. VILLA, CNR ICMATE, Lecco, Italy; E.M. SHIRKHARKOLAEI, S. DEHGAHI, D. JAFARI, University of Twente, Enschede, Netherlands
Cooling technologies based on solid-state phase-changing materials attract increasing interest as alternatives to traditional gas-based systems. Shape Memory Alloys (SMAs) are materials that undergo a first-order phase transformation upon mechanical deformation. The variation of latent heat associated with the Thermoelastic Martensitic Transformation (TMT) enables caloric effects that can be exploited in cooling applications. Laser powder bed fusion (LPBF), an additive manufacturing technique, allows the manufacturing of complex architectures with large exchange surface area. In particular, struts-based lattice structures not only enhance the heat exchange but also improve the stress-induced TMT while maintaining their structural integrity. Moreover, it is also possible to introduce compositional or microstructural gradients which can further enhance the mechanocaloric efficiency and the temperature window. In our work, we fabricated NiTi and/or NiMnTi lattice structures with LPBF. The mechanocaloric properties are investigated experimentally upon unidirectional compression and torsional deformation. Factors influencing the functional performances of the material are considered and eventually characterized. Moreover, the mechanical properties and cycling resistance were assessed.
FI-3:IL25 Multicaloric Materials in Pulsed Magnetic Fields
T. GOTTSCHALL, T. NIEHOFF, E. BYKOV, M. STRASSHEIM, C. SALAZAR-MEJIA, J. WOSNITZA, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
With the world's increasing population, there is the need for environmentally friendly cooling. Solid-state refrigeration by one or several of the caloric effects – electro-, magneto-, baro- or elastocaloric - where the material's temperature is forced to change under the application of an electrical, magnetic, or mechanical field is a promising alternative. At the Dresden High Magnetic Field Laboratory, we have a unique tool for investigating these materials, namely by using pulsed magnetic fields. Due to the short pulse duration, it is straightforward to determine adiabatic temperature changes in small but also high fields up 70 T. Heusler alloys are highly promising materials for energy-efficient solid-state refrigeration as large multicaloric effects can be achieved across their magnetostructural martensitic transformation. However, the large hysteresis that occurs during the martensitic transformation prevents cyclical operation in the classic AMR (active magnetic regenerator) process. Instead, when applying magnetic fields and uniaxial load in combination on a specimen with tuned properties, the exploiting hysteresis cycle can be performed. In this work, we show our recent achievements in the implementation of this multicaloric approach using pulsed magnetic fields.
FI-3:L26 NiMnGa-based Multicaloric Alloys: Experimental Investigation in Magneto-mechanical Coupling
E. VILLA, F. VILLA, E. BESTETTI, F. PASSARETTI, C. TOMASI, E. BASSANI, N. BENNATO, CNR ICMATE Lecco Unit, Lecco, Italy; CNR ICMATE Genova Unit, Genova, Italy
The Ferromagnetic Shape Memory Alloys (FeSMA) attracted increasing interest as multicaloric materials for solid state cooling. The most important field coupling corresponds to the magnetic and mechanical co-induction of thermoelastic martensitic transformation (TMT) to develop an elasto and magneto-caloric effect in the material. In our work we present an experimental investigation on NiMnGa-based polycrystalline alloys, using an experimental setup ad hoc developed for measuring stress-strain curves in isothermal conditions under a magnetic field. We carried out experimental measurements at different temperature above Af and under 4 values of magnetic field: 0.1, 0.26, 0.46 and 0.56 T. In this way we measured the elastocaloric and magnetocaloric effects at the same time. By elaboration with Maxwell equations, the entropy changes DS are evaluated, and the influence of magnetic field is discussed. The functional caloric parameters as DTad vs. magnetic field until 0.56 T are measured by thermocouples system with high frequency sampling device. The application of a magnetic field seems to act like an additional mechanical axial stress. The precise contribution of the magnetic field is considered and discussed starting from a magnetostrictive approach.
FI-3:L27 Beyond the Single-Phase Paradigm: Third-Generation High-Entropy Alloys with Enhanced Magnetocaloric Properties
JIA YAN LAW1, L. HAN2, D. RAABE2, O. GUTFLEISCH3, V. FRANCO1, 1Multidisciplinary Unit for Energy Science, University of Seville, Spain; 2Max Planck Institute for Sustainable Materials, Düsseldorf, Germany; 3Department of Materials Science, Technical University of Darmstadt, Darmstadt, Germany.
Third-generation high-entropy alloys (HEAs) are evolving from conventional simple equiatomic compositions to intentionally designed, high-performance functional materials. Exemplifying this transition, multiphase FeMnNiGeSi HEAs are designed for first-order thermomagnetic behavior and feature a multiphase microstructure that enhances, rather than limits, their magnetocaloric effect (MCE). Low-temperature annealing facilitates stress relaxation, which modifies the distribution of magnetic anisotropy and markedly increases the MCE to values comparable with benchmark materials, such as La(Fe,Si)13, Fe2P, and Gd5Si2Ge2. Temperature-dependent first-order reversal curve (TFORC) analysis, along with advanced microscopy techniques, are applied together for the first time to any HEA to map phase coexistence and the thermomagnetic behavior, elucidating the structure-thermomagnetic behavior relationship critical for optimizing caloric performance. The results challenge the conventional single-phase paradigm of HEAs and highlight that multiphase characteristics can yield superior caloric functionalities, thereby providing a framework for the rational design of next-generation magnetocaloric materials.
FI-3:L28 In-Operando Comparison of Tailored Full-Heuslers with First- and Second-Order Transitions for Low-Grade Waste Heat Harvesting
E. RUSCONI, L. GALLO, S. FABBRICI, G. TREVISI, F. ALBERTINI, IMEM-CNR, Parma, Italy; F. CUGINI, M. SOLZI, Department of mathematical, physical and computer sciences of the University of Parma, Parma, Italy
Thermomagnetic (TM) energy harvesting shows potential for low-grade waste heat (T<100 °C) conversion to electricity by making use of TM materials showing, among others, a high magnetic jump (∆M) at suitable T. So far, first-order transition materials have been scarcely investigated despite their high ∆M. Here, two full-Heusler systems, Ni2MnGa and Ni2MnSn, were respectively doped with copper (at Mn and Ga sites) and cobalt (at Ni sites) to obtain first-order, and second-order transitions, within 300K and 400K. Cu-doping raises the martensitic transition T and decreases the Curie T of the austenitic phase, leading to transition merging; Co doping in Ni2MnSn separates the Curie T of the martensite and the structural transition, thus enhancing the magnetic jump. Compositions with high ∆M and very narrow hysteresis were obtained at suitable T (Ni49.4Mn19.7Cu6.5Ga24.3: 30 A/m2kg, hysteresis: 4±1K; Ni44.1Co4.9Mn39.1Sn11.9: 74 A/m2kg, hysteresis: 7±1K). Samples were tested in a Curie wheel prototype to assess the effects of transition type, transition T, and hysteresis width on the mechanical and electrical power outputs.
This project has received funding from the European Union under grant agreement No101119852.
Session FI-4 Devices for solid state refrigeration, heat pumps and other energy related applications
FI-4:IL29 Electrocaloric Cooling Devices
E. DEFAY, Luxembourg Institute of Science and Technology, Esch sur Alzette, Luxembourg
Cooling with solid-state electrocaloric materials has been intensively studied in recent years. Despite these efforts, the cooling industry is still waiting for a convincing, competitive demonstrator that takes over the challenge. In this talk, I will introduce the electrocaloric effect and the best materials exhibiting this effect. The core of the presentation will be about cooling devices based on electrocaloric materials. More specifically, I will give details about fluid-based electrocaloric regenerators. These devices are subtle to design and use because one needs to combine materials science, thermodynamics and electrical engineering to have them running properly. Recent results obtained on electrocaloric regenerators using ceramic multilayer capacitors will be disclosed, showing that it is possible to reach temperature spans larger than 20 K at room temperature and cooling power of several watts with a few grams of active material.
FI-4:IL30 Digital Twin Driven Design and Modelling of Next-generation Thermomagnetic Generators with Optimized Efficiency
A. IZADI1,2, S. FÄHLER1, 1Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany; 2Faculty of Mechanical Science and Engineering, TUD Dresden University of Technology, Dresden, Germany
Although over 50% of total waste heat is low-grade, only limited technologies are available for its recovery, which also have low efficiency. Thermomagnetic generators (TMG) offer a theoretical exergy efficiency of 55% relative to Carnot, making this technology a promising candidate. Here we consider a TMG with Genus 3 topology that converts waste heat near room temperature to electricity. In this device, alternating cold and hot water on thermomagnetic plates reverses the magnetic flux, inducing voltage in a coil. This study aims to increase device efficiency by designing the next TMG generation. We first develop a digital twin by coupled time-dependent multiphysics modelling, validated by experiments. Our digital twin identifies inefficiencies in the previous design, heat leaks to passive parts, water mixing losses, inhomogeneous temperatures of the active material, and magnetic stray fields. Furthermore, we accelerate heat exchange to increase cycle frequency, required for higher output power. We address these issues by redesigning core parts of the device, including inlet/outlet water management and thermomagnetic plate channels.
This project has received funding from the European Union under grant agreement No 101119852 Heat4Energy.
FI-4:L31 Impact of Rotor Design on Heat Exchange Efficiency for Thermomagnetic Rotary Generators
L. GALLO, S. FABBRICI, F. ALBERTINI, IMEM-CNR, Parma, Italy; F. CUGINI, G. GARULLI, M. SOLZI, University of Parma, Parma, Italy; J.Y. LAW, V. FRANCO, University of Sevilla, Sevilla, Spain
Thermomagnetic (TM) generation offers a promising route to convert low-grade waste heat into mechanical and electrical energy by exploiting temperature induced variations of magnetization in a magnetic field gradient. The performance of Curie-wheel-type generators remains strongly limited by the thermal coupling between the active material and the heat reservoirs. In this work, a laboratory-scale TM generator prototype was exploited to investigate how rotor architecture affects the efficiency of energy conversion. Three different rotor types, based on the Ni₄₈Mn₃₆In₁₆ Heusler compound, were explored: (i) an epoxy-based composite with 87 wt% powder; (ii) a 3D-printed composite with reduced thickness to enhance surface-to-volume ratio; and (iii) a suction casted polymer-free metallic architecture. In-operando measurements under controlled thermal gradients (297–340 K) revealed that output power and rotational dynamics are dictated by the efficiency of heat exchange between the rotor and the thermal sources. The optimized configurations delivered power output values among the highest reported for Curie-wheel devices, highlighting the crucial role of rotor geometry and interfacial design in maximizing TM conversion and advancing TM energy harvesters.
FI-4:L32 Elastocaloric Microcooling
JINGYUAN XU1, N.S. AGHDAM1, YI-TING HSIAU1, KUN WANG1, L. BUMKE2, E. QUANDT2, M. KOHL1, 1Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany; 2Institute for Materials Science, Kiel University (CAU), Kiel, Germany
Elastocaloric cooling is an emerging solid-state cooling technology that offers environmentally friendly and energy-efficient alternatives to traditional vapor-compression systems. This talk presents recent advancements in elastocaloric microcooling devices at Karlsruhe Institute of Technology. At the miniature scale, we employ superelastic shape memory alloy (SMA) films that combine a high elastocaloric effect with efficient heat transfer due to their large surface-to-volume ratios. We report the development of an ultra-high-lifetime elastocaloric microcooling device utilizing ultra-low-fatigue TiNiCuCo films. These devices demonstrate exceptional durability, exceeding 10 million cycles, achieved through optimized film design, mechanical fixation, and adaptable loading mechanisms that collectively enhance system reliability and operational lifespan. Finally, we present our recent progress on a heat-driven elastocaloric cooling system employing SMA films, which enables cooling powered directly by thermal energy rather than electricity, representing a key step toward sustainable, electricity-free solid-state refrigeration.
FI-4:L33 Pyroelectric Energy Harvester Based on Commercial Lead-Free Multilayer Capacitors
A. HELT1,2, O. RAMÍREZ1, M. GERARD1, N. BOUSRI1, M. KHALIL1,2, E. DEFAY1,2, 1Luxembourg Institute of Science and Technology, Esch-sur-Alzette, Luxembourg; 2University of Luxembourg, Esch-sur-Alzette, Luxembourg
Using pyroelectric materials is one of the promising solutions in the development of sustainable energy harvesting techniques, thanks to their capability of transforming waste heat into electricity by exploiting temporal temperature changes. As an example, a harvested energy density of 3.14 J.cm-3 has already been obtained using lead scandium tantalate-based devices. Here, we study the pyroelectric potential of commercial lead-free multilayer capacitors that have the advantage of being relatively cheap and available in large quantities. First, the composition, structure and thermal characteristics of the materials are investigated using several characterization methods. Then, we show a harvester prototype able to deliver up to 1.6 J per Olsen cycle with a temperature span of 80°C and a voltage of 200 V, which corresponds to an energy density of 1.2 J.cm-3. Finally, several prototype configurations are compared using simulations, with the objective of increasing the efficiency of future devices.
FI-4:L34 Cost-Effective Elastocaloric Cooling by Rubber-Based Microchannel Regenerators
KUN WANG, M. KOHL, JINGYUAN XU, Institute of Microstructure Technology, Karlsruhe Institute of Technology, KIT, Eggenstein-Leopoldshafen, Germany
Rising global temperatures and urbanization are driving soaring cooling demand, amplifying energy use and emissions. Conventional vapor-compression systems consume nearly 40% of building electricity and rely on high–global warming potential refrigerants, underscoring the need for sustainable alternatives. Elastocaloric (eC) cooling, which exploits latent heat from stress-induced phase transitions, offers a solid-state, volatile refrigerant-free solution but remains limited by the high cost and large actuation forces (>30 kN) of shape-memory alloys (SMAs). Soft elastomers such as natural rubber (NR) provide a low-cost, renewable alternative, achieving ~12 K temperature changes under <100 N loads and potentially reducing system cost from ~6000 €/kW for SMA devices to <210 €/kW. This work introduces a one-dimensional numerical model for large-deformation polymeric elastocaloric regenerators (AERs) with dynamic spatial discretization, strain-dependent deformation factors, and a fluidic compensation mechanism. Validated using 3D-printed TPU regenerators, the model identifies the fluidic compensation as essential for maintaining cooling power and COP, guiding scalable, low-cost, and energy-efficient elastocaloric cooling systems based on soft polymers and natural rubber.
FI-4:IL35 Gradient Materials Architectures for Efficient and Scalable Elastocaloric Cooling Systems
ICHIRO TAKEUCHI, Department of Materials Science and Engineering, University of Maryland, College Park, MD, USA
I will discuss our latest work on development of elastocaloric cooling materials and devices. Key features of our systems include tube-bundle-based heat exchangers. We are actively designing and incorporating new materials in order to enhance the performance of elastocaloric regenerators. For one system, we have developed a gradient NiTi engineered to optimize the thermomechanical response across the active regenerator. The gradient design enables tailored phase transformation behavior across the length of long regenerator tubes, significantly suppressing strain maldistribution during cyclic operation, reducing localized fatigue and enhanced system durability. This has led to 25% improvement in the temperature span and 10% decrease in input work compared to a regenerator made of standard uniform (non-gradient) NiTi tubes. In another system, we have developed a three-stage cascade where three stages house NiTi with three different transformation temperatures. This has allowed us to achieve 38K in temperature span of the regenerator. I will also discuss the emerging trend in the development path of the caloric technologies.
This work is carried out in collaboration with Het Mevada, Boyang Liu, and Yunho Hwang, and is supported by NSF ERC EARTH.
FI-4:IL36 Thermal Management Opportunities for Caloric Technologies
A. KITANOVSKI, K. KLINAR, U. TOMC, D.A GACNIK, University of Ljubljana, Faculty of Mechanical Engineering, Ljubljana, Slovenia
Effective thermal management in caloric devices is crucial for achieving high energy efficiency and power density, both of which remain challenging in practical experimental devices compared to their theoretical potential. Additionally, low power density raises concerns related to the overall carbon footprint of caloric devices, which poses an additional barrier to their commercialization. Conventional heat transfer methods, even if optimized in the future, cannot support the sufficiently fast execution of thermodynamic cycles in caloric devices. This limitation affects not only heat pumping and cooling but also energy harvesting applications. These challenges necessitate opening new research directions focused on different types of thermal control devices, such as thermal diodes, thermal switches, and innovative solutions for heat regeneration. Although numerous studies have addressed thermal control devices to date, none have yet delivered truly groundbreaking results. This contribution explores various challenges and opportunities for the future development of caloric technologies that incorporate thermal control devices and innovative thermal engineering solutions.
FI-4:L37 Polymer-based Electrocaloric Regenerators with Large Temperature Spans
O. RAMÍREZ, N. SAURABH, Luxembourg Institute of Science and Technology, Esch-sur-Alzette, Luxembourg; F. DOMINGUES DOS SANTOS, ARKEMA FRANCE SA, Colombes, France; S. MÖNCH, University of Stuttgart, Stuttgart, Germany; V. ZERILLO, KEMET ELECTRONICS ITALIA S.R.L., Sasso Marconi, Italy; E. DEFAY, Luxembourg Institute of Science and Technology, Esch-sur-Alzette, Luxembourg. University of Luxembourg, Esch-sur-Alzette, Luxembourg
Electrocaloric regenerators (ERs) based on ceramic multilayer capacitors (MLCs) have demonstrated great potential as solid-state alternatives to conventional cooling, achieving temperature spans (ΔT) exceeding 20K[1]. Although polymer-based electrocaloric materials possess higher intrinsic cooling potential than ceramics, thanks to their larger adiabatic temperature change and specific heat capacity, their implementation in regenerators has so far yielded inferior performance. In this work, we demonstrate the implementation of PVDF-based multilayer capacitors into a regenerator prototype, which consists of the electroactive material and a dielectric fluid that transports heat along the device. During operation, a power supply provides the electric field, while a bidirectional pump displaces the fluid in synchrony with the charge-discharge cycles. Key parameters such as fluid slit thickness, number of MLCs, flow rate, and operating frequency strongly influence the heat exchange between the MLCs and the fluid, and thus the overall ΔT. After a prototype and system optimization, we achieved a temperature span of 15.8K at a potential difference of 250V, demonstrating the strong potential of polymer-based regenerators for efficient solid-state cooling.
[1] DOI:10.1126/science.adi5477.
FI-4:IL38 Thermomagnetic Energy Generation and Heat-Driven Elastocaloric Cooling at Miniature Scales
M. KOHL, Karlsruhe Institute of Technology, Karlsruhe, Germany
This presentation addresses recent developments of miniature-scale devices for conversion of waste heat into usable energy. Waste heat is an abundant energy resource particularly at temperatures below 100 °C. One type of devices are thermomagnetic (TM) power generators that have the potential to harness low-grade thermal energy with material’s efficiency up to 55% of the thermodynamic limit. Desired material properties are a steep magnetization change within a small temperature interval as well as low heat capacity and latent heat. Promising TM material candidates are Heusler alloys Ni-Mn-Ga, Gd and La(Fe,Si)-based intermetallic compounds. TM films are highly attractive, as their large surface-to-volume ratio enables rapid heat transfer. TM power generators utilize heat-induced resonant oscillation of a cantilever, which is converted into electricity using either induction or the piezoelectric effect. Another option for waste heat recovery is heat-driven actuation, which can be used for film-based elastocaloric cooling. SMA film actuators can generate large stroke and force required to stress-induce a martensitic phase transformation in NiTiFe and TiNiCuCo film refrigerants. The presentation covers the various engineering aspects from materials to systems characterization.
FI-4:IL39 From Lab to Life: Advancing Elastocaloric Heat Pumps for Real-World Sustainability
A. GRECO, Department of Industrial Engineering, University of Naples “Federico II”, Italy
The SMACool project aims to develop a new generation of heat pumps based on the elastocaloric effect, a solid-state cooling principle observed in Shape Memory Alloys (SMAs) like NiTi. When adiabatically loaded and unloaded by a mechanical field, these materials undergo reversible transformations that cause significant temperature and entropy changes—offering a promising, gas-free alternative to traditional vapor-compression systems. Within SMACool, the focus is on designing and optimizing a rotating elastocaloric heat pump, where the active material is arranged in a compact regenerator crossed by water as heat transfer fluid. Using advanced numerical modeling (COMSOL Multiphysics), different geometries and loading modes were studied to identify the most efficient configuration. While tension-based solutions showed limited performance at safe strain levels, compression-based regenerators with 3% strain proved more effective and durable for real-world applications. The project has delivered optimized designs capable of meaningful temperature spans and cooling power, confirming the potential of elastocaloric technology for sustainable heating and cooling. The current design is approaching TRL 4, with experimental validation of key components underway. By eliminating high-GWP refrigerants and enabling compact, electrically driven systems, SMACool offers a low-carbon alternative aligned with EU targets for climate-neutral buildings and green cooling technologies.
FI-4:IL40 Additive Manufacturing of Magnetocaloric Regenerator: Material, Design, Processing and Performance
F. SCHEIBEL, S. GHORAI, O. GUTFLEISCH, Institute for Functional Materials TU Darmstadt, Darmstadt, Germany; D. ZENTGRAF, Institute for Production Management TU Darmstadt, Darmstadt, Germany; J-P. ZWICK, D. BENKE, MAGNOTHERM Solutions GmbH, Darmstadt, Germany
Additive manufacturing (AM) enables the fabrication of magnetocaloric regenerators with complex geometries, thereby optimizing thermal exchange and pressure drop within devices. In addition, the AM methods, such as laser powder bed fusion (PBF-LB), can produce net-shape parts from materials that are difficult to process by other techniques. PBF-LB allows a quick adaptation of the microchannel design and outer dimensions across different prototypes, which is essential for rapid development from material to device. In our study, we present the entire processing chain from Gd-powder to net-shaped Gd-regenerators, along with their functional properties, including magnetocaloric effect, pressure drop analysis of the complex structure, temperature span, and performance in a real magnetocaloric refrigerator (POLARIS© from MAGNOTHERM Solutions). Compared with conventional powder bed regenerators, PBF-LB regenerators exhibit a 60% reduction in pressure drop. Tailoring the regenerator's inner structure yields a temperature span and cooling power comparable to those of the optimized powder-bed regenerator. In combination with reduced pressure drop, the AM regenerators would have a higher COP.
The work is funded by the DFG CRC/TRR 270 "HoMMage" and 52721505, and LOEWE 3 Project „OptiKal“.