Symposium CG
ABSTRACTS
Session CG-1 Process development and advanced manufacturing
CG-1:IL01 Polymer-Derived High Entropy Carbides-Based Nanocomposites: Synthesis, Microstructural Evolution and Properties
ZHAOJU YU, College of Materials, Xiamen University, Xiamen, China
Polymer-derived ceramics (PDCs) have been intensively studied for nearly 50 years due to their unique advantages to producing ceramic fibers, coatings, foams, nanocomposites and for additive manufacturing. In the present talk, high entropy carbides-based ceramic nanocomposites including SiC/(Ti0.25Zr0.25Hf0.25Ta0.25)C and SiC/(Hf0.25Ta0.25Zr0.25Nb0.25)C/C nanocomposites, are effectively synthesized via the PDC approach. The PDC route facilitates the in situ formation of a high-entropy phase within the ceramic matrix under low temperature pyrolysis conditions. The SiC/(Ti0.25Zr0.25Hf0.25Ta0.25)C nanocomposites exhibit excellent oxidation resistance between 1200 ◦C and 1500 ◦C due to the in situ generated continuous multiphase scales consisting of β-SiO2, HfTiO4, ZrSiO4, HfSiO4, and Ta2O5 that can be rapidly sintered during oxidation. Particularly, at 1200 ◦C, the parabolic oxidation rate constant (Kp) value is 1–2 orders of magnitude lower than that of similar SiC/HfC, SiC/ (Hf, Ta)C, SiC/(Hf, Ti)C and SiC/(Hf, Zr, Ti)C nanocomposites. A dense monolithic SiC/(Ti0.25Zr0.25Hf0.25Ta0.25)C nanocomposite possesses an open porosity of 0.41 vol%, nano-hardness of 27.47 ± 0.46 GPa, elastic modulus of 324.00 ± 13.60 GPa, and fracture toughness of 3.59 ± 0.24 MPa·m0.5, demonstrating excellent mechanical properties. Owing to their exceptional mechanical properties and oxidation resistance, these high-entropy ceramics-based nanocomposites are promising candidate materials for applications in harsh environments. The relationship between the obtained nano/microstructure of the synthesized high entropy carbides-based ceramic nanocomposites and their property features will be highlighted.
CG-1:L02 High Entropy Ceramic-metal Composites via Self-propagating High Temperature Synthesis
A.S. ROGACHEV, Merzhanov Institute of Structural Macrokinetics and Materials Science Russian Academy of Sciences (ISMAN), Chernogolovka, Moscow Region, Russia
High entropy ceramic-metal composites cover several types of materials, e.g., cermets composed of high-entrophy ceramic phase (HfTaZrNbTiC₅, VNbTaMoWC₅, etc.) with simple metal binder (Co, Ni, Fe); cermets composed of simple carbides (e.g. TiC) with high entropy alloy binder (Cantor alloys); combination of multi-principal component ceramic and binder phases. All these types of materials can be produced using the method of self-propagating high temperature synthesis (SHS). Thermodynamic and kinetic analyses show that exothermic reactions between the transition metals and carbon release amount of heat that is enough for melting up to 50 % of other metals that forms alloy binder. The thermodynamic analysis is confirmed by production of various cermets using SHS. Mechanical, thermal and electrical activation can be used for further expanding the composition limits of the materials produced via SHS. New results of Time-Resolved X-ray and Synchrotron-ray Diffraction study show that phase composition and crystal structure forms during a few seconds behind the combustion wave. Consolidation of the SHS-cermets using SPS, vacuum sintering and hot pressing, allow production of bulk cermets with outstanding properties.
This work is supported by Russian Science Foundation, grant 25-13-00040.
CG-1:L03 Synthesis and Characterization of (Hf₀.₂Zr₀.₂Ta₀.₂Nb₀.₂Ti₀.₂)B₂ Powders
H. BICER1, S. ALTUN1, M. TUNCER1, H. GOCMEZ1, S. TESLIA2, D. RIEZNIK2, I. SOLODKYI2, I. BOGOMOL2, 1Department of Metallurgy and Materials Engineering, Kütahya Dumlupınar University, Kütahya, Turkey; 2Department of High-Temperature Materials and Powder Metallurgy, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Kyiv, Ukraine
This work focuses on the synthesis and analysis of high-entropy boride (HEB) powders with the composition (Hf₀.₂Zr₀.₂Ta₀.₂Nb₀.₂Ti₀.₂)B₂. The powders were synthesized through both borothermal and carbothermal reduction techniques using oxide-based precursors (HfO₂, ZrO₂, Nb₂O₅, Ta₂O₅, TiO₂). In parallel, a zone melting method was applied to fabricate directionally solidified eutectic LaB₆–(Hf₀.₂Zr₀.₂Ta₀.₂Nb₀.₂Ti₀.₂)B₂ structures. For this, TiB₂, ZrB₂, HfB₂, NbB₂, TaB₂, and LaB₆ powders were processed using high-energy ball milling under controlled parameters. Subsequent nitric acid etching successfully removed the LaB₆ phase, resulting in HEB powders. Structural and microstructural analyses were performed on the samples obtained from both synthesis routes using X-ray diffraction (XRD), along with scanning electron microscopy (SEM).
CG-1:L04 Combustion Synthesis of High-entropy Ceramics for Multifunctional Applications
S. AYDINYAN, Laboratory of Macrokinetics of Solid State Reactions, Institute of Chemical Physics NAS of Armenia, Yerevan, Armenia; Department of Mechanical and Industrial Engineering, Tallinn University of Technology, Tallinn, Estonia; Instituto de Cerámica y Vidrio, CSIC, Madrid, Spain
High-entropy ceramics are promising candidates for multifunctional applications due to their unique physicochemical characteristics derived from configurational entropy stabilization. These materials consist of five or more principal elements in near-equiatomic proportions, leading to the formation of single-phase structures with enhanced stability and tunable properties. To synthesize these advanced materials, solution combustion synthesis (SCS) and self-propagating high-temperature synthesis (SHS) have been employed as efficient, energy-saving, and scalable routes. SCS utilizes aqueous solutions of metal precursors and fuels to initiate an exothermic combustion reaction, producing nanostructured high-entropy phases. SHS, driven by a self-sustaining exothermic reaction, allows the rapid formation of single-phase materials at elevated temperatures. Kinetic studies provided valuable insights into the reaction mechanisms and phase evolution during synthesis, enabling optimization of processing conditions. This study highlights the synthesis-structure-property relationships in some high-entropy ceramics and demonstrates their multifunctional potential across diverse advanced technological fields.
CG-1:L05 Effect of Carbon to Metal Ratio on Microstructure and Mechanical Properties of (MoTaTiVW)Cx High Entropy Carbide
K. KUMAR BEHERA, K.G. PRADEEP, S. RAO BAKSHI, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, India
In this study, novel (MoTaTiVW)Cx high entropy ceramics having different Metal to Carbon ratio (x) of 0.75-0.97 were prepared by reactive spark plasma sintering. The effect of ball milling time on particle size, phase evolution and carbon pick-up due to toluene decomposition were studied. Formation of single-phase high entropy carbide having FCC structure with equiaxed grains was confirmed XRD, EBSD, TEM, and SAED analysis. Transmission Kikuchi Diffraction and TEM revealed the presence of an intergranular phase at grain boundaries and triple junctions. 3D-Atom Probe Tomography studies showed uniform distribution of elements within the grains with some segregation of impurity elements Fe and Co to the grain boundaries indicating minor contribution of liquid phase sintering. A low sintering temperature and higher milling time resulted in finer grain size The microhardness was found to increase with milling time and C/M ratio. The highest microhardness and indentation fracture toughness was found to be 2732 ± 80 HV0.1 and 4.4 MPa.m1/2. Dry sliding wear tests against Al2O3 and WC counterbody at 15N and 30N load showed that (TiWTaMoV)C0.60 carbide had low specific wear rate of 2.0-6.0 x 10-7 mm3·N−1·m−1 making it a potential wear-resistant material.
Session CG-2 Properties, performance and applications
CG-2:IL06 Microstructure and Thermophysical Properties of Fully Dense Single-Phase (Cr,Mo,Ta,V,W)C1-δ High-Entropy Carbide Ceramics
G.E. HILMAS1, A. SARIKHANI2, Y.S. HOR3, W.G. FAHRENHOLTZ1, 1Department of Materials Science and Engineering Missouri University of Science and Technology, Rolla, MO, USA; 2Materials Research Center, Missouri University of Science and Technology, Rolla, MO, USA; 3Department of Physics, Missouri University of Science and Technology, Rolla, MO, USA
Developing materials capable of withstanding extreme thermal and mechanical stress is critical for advancing next-generation technologies such as hypersonic systems. For this purpose, high-entropy carbide (HEC) ceramics of composition (Cr,Mo,Ta,V,W)C1-δ were synthesized and densified by spark plasma sintering (SPS) at various temperatures, yielding fully dense, single-phase microstructures with uniformly distributed metal constituents. Increasing the temperature resulted in monotonic increases in both grain size and lattice parameter. Neutron diffraction analysis confirmed X-ray diffraction (XRD) findings and enabled identification of carbon vacancies and lattice-dissolved oxygen in conjunction with X-ray photoelectron spectroscopy (XPS). Thermoelectric and thermomagnetic properties were investigated at both ambient and cryogenic temperatures to explore correlations between carbon vacancy ordering and electronic contributions to thermal transport. High-temperature thermal transport was further characterized using laser flash analysis (LFA) as well as a thermoelectric apparatus under forward/reverse bias voltage. The combined structural and functional attributes position these HEC ceramics as promising candidates for high-performance applications in extreme thermal environments.
CG-2:IL07 A Highly Deficient Medium-Entropy Perovskite Ceramic for Electromagnetic Interference Shielding under Harsh Environment
YUCHI FAN, Donghua University, Shanghai, China
Materials that can provide reliable electromagnetic interference (EMI) shielding in highly oxidative atmosphere at elevated temperature are indispensable in the fast-developing aerospace field. However, most of conductor-type EMI shielding materials such as metals can hardly withstand the high-temperature oxidation, while the conventional dielectric-type materials cannot offer sufficient shielding efficiency in gigahertz (GHz) frequencies. Here, a highly deficient medium-entropy (ME) perovskite ceramic as an efficient EMI shielding material in harsh environment, is demonstrated. The synergistic effect of entropy stabilization and aliovalent substitution on A-site generate abnormally high concentration of Ti and O vacancies that are stable under high-temperature oxidation. Due to the clustering of vacancies, the highly deficient perovskite ceramic exhibits giant complex permittivity and polarization loss in GHz, leading to the specific EMI shielding effectiveness above 30 dB/mm in X-band even after 100 h of annealing at 1000 degrees C in air. Along with the low thermal conductivity, the aliovalent ME perovskite can serve as a bifunctional shielding material for applications in aircraft engines and reusable rockets.
CG-2:L08 Multicomponent Rare-Earth Zirconates as new Thermal Barrier Coating Material – Thermophysical Properties and Chemical Compatibility
M. SCHENKER1, P. HUTTERER2, J.J. PFLUG1, M. LEPPLE1, 1Justus Liebig University, Giessen, Hessen, Germany; 2DECHEMA-Forschungsinstitut, Frankfurt (Main), Hessen, Germany
In airplane turbines, yttria stabilized zirconia (YSZ) has been used since the 1980s as thermal barrier coating to insulate metallic components of the turbine blades. To improve the efficiency and lifetime of a turbine, new materials are needed to overcome the limitations of YSZ like phase transition and limited corrosion resistance. Derived from this material other zirconium oxides are investigated as potential substitutes. In combination with the concept of high-entropy materials, multicomponent rare-earth zirconates with the general formular A2Zr2O7 are investigated. The compositions contain five rare-earth cations in equimolar proportions on the A sublattice. The investigated materials show suitable properties for the application in airplane turbines like low thermal conductivity and matching coefficients of thermal expansion with the underling substrate. In addition, the chemical compatibility of the material and alumina at high temperatures was investigated since they are in contact with each other in a turbine system.
The work was supported by the German Federal Ministry of Education and Research (03XP00301).
CG-2:L09 Irradiation Performance of High-entropy Rare Earth Titanate Ceramics
XINGHUA SU, YANGLIU TIAN, CHENGGUANG LOU, School of Materials Science and Engineering, Chang'an University, Xi'an, China
High-entropy ceramics are interesting candidates for immobilization of high-level radioactive waste. However, the link between radiation resistance and configuration entropy is seldom studied. In this work, the irradiation performances of high-entropy ceramics (Ho1/8Dy1/8Er1/8Y1/8Sm1/8Eu1/8Gd1/8Yb1/8)2Ti2O7 (8HETC), and (Y1/5Sm1/5Eu1/5Gd1/5Yb1/5)2Ti2O7 (5HETC), as well as Gd2Ti2O7 ceramic (TC) under 800 keV Kr2+ ion irradiation at room temperature were studied. It was found that the resistance to radiation-induced amorphization was enhanced with the increase of configuration entropy. Accordingly, 8HETC with a high configuration entropy of 2.08R demonstrated the high irradiation resistance compared to 5HETC and TC. In addition, the irradiated 8HETC displayed the largest nanohardness and elastic modulus. The formation energies of cation antisite defects and anion Frenkel defects were decreased with the increase of the configuration entropy, which was suggested to account for the highest irradiation resistance of 8HETC with the largest configuration entropy. This study provides the insights into the relationship between configurational entropy and radiation resistance of high-entropy ceramics, which is helpful to design the advanced nuclear engineering materials.
CG-2:L10 Synthesis and Characterization of Magnetic High-Entropy MAX Phase
H. KIRAKOSYAN, KH. NAZARETYAN, A.B. Nalbandyan Institute of Chemical Physics, Yerevan, Armenia; A. QUESADA, Instituto de Cerámica y Vidrio, CSIC, Madrid, Spain; S. AYDINYAN, A.B. Nalbandyan Institute of Chemical Physics, Yerevan, Armenia and Tallinn University of Technology, Tallinn, Estonia
As is known, magnetic materials play an important role in modern technologies. In recent years, there has been increasing interest in high-entropy MAX phases as a new class of materials that combine the characteristic properties of high-entropy materials and MAX phases. However, the magnetic high-entropy MAX phases have not been obtained so far. Therefore, the aim of this work is to synthesize magnetic high-entropy MAX phases by selecting combinations of metals that include elements with high magnetic moments, together with other metals known to form binary MAX phases, such as (CrMn)₂AlC, (CrFe)₂AlC, (CrCo)₂AlC, (CrTi)₃AlC etc, that exhibit magnetic properties. The synthesis was carried out under conditions of rapid linear heating using a high-speed temperature scanner equipment (HSTS-3). The optimal conditions for the synthesis of the target magnetic material were determined depending on the heating rate and temperature. This study enables the synthesis of magnetic high-entropy MAX phases, offering potential for future functional and magnetic applications.
CG-2:IL11 Exceptional Oxidation Resistance of High-Entropy Carbides up to 3600 °C
YANHUI CHU, School of Materials Science and Engineering, South China University of Technology, Guangzhou, China
Achieving exceptional oxidation resistance at elevated temperatures has long been desirable for ultrahigh-temperature materials to be used in relevant applications such as hypersonic flights, re-entry vehicles, and propulsion systems. However, their practical service temperatures are typically limited to below 3000 °C. Here, we report the exploration of (Hf, Ta, Zr, W)C high-entropy carbides with exceptional oxidation resistance of 2.7 μm·s-1 up to 3600 °C through a high-entropy compositional engineering strategy. This impressive oxidation behavior arises from the formation of unique dual-structural oxide layers involving numerous high-melting-point W particles uniformly embedded within molten (Hf, Me)6(Ta, Me)2O17 (Me = metal element, Hf, Ta, Zr, and W) primary oxides. The developed (Hf, Ta, Zr, W)C demonstrates a significant breakthrough for ultrahigh-temperature applications up to 3600 °C, paving the way for further design of advanced ultrahigh-temperature materials capable of serving at higher service temperatures.
CG-2:IL12 Compositionally Complex Diborides - Effect of Competing Solubility during Sintering and Properties
L. SILVESTRONI, CNR-ISSMC, Faenza, Italy
An ultra-high temperature ceramic based on ZrB2, TiB2, and SiC was hot pressed to full density at 1850°C. Addition of 5 vol% of different metal-compounds, in the form of HfC, VC, NbC or CrB2, increased the densification temperature to 1910°C. The resulting compositionally complex ceramics had homogeneous microstructures with boride grains exhibiting core-shell features. The shell was a solid solution containing variable amounts of the three metals. Notably, TiB2 remained as a discrete phase in the reference material and in the presence of the V and Cr based additions, whilst it dissolved into the main ZrB2-based grains for other additives. Thermodynamic simulations and atomic size factors were exploited to explain the different solubility in the various systems. The compositionally complex diborides exhibited excellent properties at room temperature, with hardness up to 25 GPa and strength up to 800 MPa, which were preserved up to 1500°C. However, increasing the testing temperature to 1800°C resulted in plastic deformation owing to residual carbide phases. The observed overall properties improvements in compositionally complex borides pave the way way for tailored design of UHTC materials with multication non-equiatomic composition for applications in extreme environments.
CG-2:L13 From Single-component Reactivity to High-entropy Design: Rare-earth Chemistry-controlled CMAS Corrosion in Zirconate Ceramics
HAIRONG MAO, FUHAO CHENG, D.B. DINGWELL, WENJIA SONG, Beihang University, Hangzhou, China
Understanding how rare-earth chemistry governs the corrosion behavior of environmental silicate deposit is crucial for developing durable rare-earth zirconate (RE2Zr2O7) thermal barrier ceramics. Here, we bridge the intrinsic reactivity of single-component RE2Zr2O7 with the compositional design of high-entropy zirconates. Systematic investigation across the complete RE series (La–Lu, Y, Sc) reveals that progressive RE contraction drives a pyrochlore-to-fluorite transition accompanied by lattice densification and stabilization. High-temperature wetting and reaction experiments show that RE-dependent precursor film formation reflects intrinsic reactivity and governs interfacial phase evolution. Typically, heavier rare-earth elements stabilize the fluorite lattice, suppressing substrate dissolution but hindering protective RE/Ca-apatite formation, thus shifting the balance between dissolution- and precipitation-controlled degradation. Guided by these insights, high-entropy zirconates are designed to balance lattice stability with interfacial adaptability, achieving synergistic, multi-mechanism CMAS resistance. This study links single-component reactivity to the compositional design of high-entropy zirconates, guiding the development of next-generation CMAS-resistant ceramics.
CG-2:L14 High-Entropy A2B2O7-Type Oxide Ceramics for Extreme Environmental Applications
FEI LI, Suzhou National Laboratory, Suzhou, Jiangsu Province, China; G.J. ZHANG, Donghua University, Shanghai, China; H. ABE, the University of Osaka, Osaka, Japan
A2B2O7 type oxides, typically rare-earth transition metal compounds (e.g., rare earth zirconates), are promising for extreme environments due to their unique sets of properties. The high-entropy (HE) concept offers a framework to enhance these properties through multi-component synergies. This research systematically focuses on their design and performance. In synthesis science, we developed the liquid-phase polyol method, which can achieve atomic-level uniform mixing of multiple rare earth elements. The precursor can be converted into nanoparticles of HE A2B2O7 with average size of 3 nm after heating at only 300°C. Regarding applications, HE (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 demonstrated excellent thermal shock resistance, indicating a promising candidate for thermal barrier coating materials. Furthermore, HE (Eu1-xGdx)2(Ti0.2Zr0.2Hf0.2Nb0.2Ce0.2)2O7 exhibited superior leaching resistance and radio nuclide immobilization capacity, validating their feasibility as immobilizer for high-level radioactive wasteform. This study provides critical theoretical and experimental support for the application of high-entropy oxides in extreme environments.
CG-2:L15 Oxidation Behaviour of High-entropy Carbides and Carbonitrides
YICHEN WANG, XIANG XIONG, State Key Laboratory of Powder Metallurgy, Central South University, Changsha, China
The oxidation behaviour of the (Zr-Nb-Hf-Ta)CxN1–x, x = (1.0, 0.9, 0.8, and 0.7) powders at RT–1200°C was systematically investigated using TG-DSC analysis and compared with that of the component mono-nitride and mono-carbide powders. With the addition of nitrogen, the oxidation onset temperature (OOT) of the (Zr-Nb-Hf-Ta)CxN1–x powders increased from 761 to 794°C, and the HEC0.7N0.3 powder had a higher OOT than the component mono-carbide and mono-nitride powders. The same oxidation tests were performed on the HECxN1–x ceramics to further study the effect of diffusion and cracking on their oxidation resistance properties. The OOT of the (Zr-Nb-Hf-Ta)CxN1–x ceramics increased with increasing nitrogen content, similar to what happened with the powders. In comparison to the HEC ceramic, the HECN ceramics displayed improved oxidation resistance due to increased OOT, lower oxidation speed, fewer cracks, and an intact structure after oxidation. The oxidation process was accelerated by the development of cracks and pores, which had a significant negative effect on the oxidation resistance. Structural stability played an important role in the oxidation resistance of the HECxN1–x ceramics, which may be related to the high entropy effect.
CG-2:IL16 Design and Properties of High-entropy Ceramic Matrix Composites: from Structure to Functional Applications
DEWEI NI, YANG HU, SHAOMING DONG, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China
Continuous carbon fiber reinforced ultra-high temperature ceramic matrix composites (UHTCMCs) are endowed with excellent mechanical properties, ablation resistance at ultra-high temperatures, and furthermore, overcome the inherent brittleness and poor thermal shock resistance of bulk UHTCs. Therefore, these materials are considered as the most potential candidates for applications in thermal structures and anti-ablation components of hypersonic vehicles, such as sharp nose, leading edge, and combustor of solid rocket. The appearance of high-entropy ceramics brings new opportunities for the development of novel ultra-high temperature thermal protection materials. Due to the novel “high-entropy effects”, high-entropy ultra-high temperature ceramics (HECs) show superior mechanics and oxidation resistance compared with single component ceramics. Combining the concept of high-performance HECs ultra-high temperature ceramics with ceramic-matrix composites, high-entropy ceramic-matrix composites (Cf/HECs) are expected to become a new generation of highly reliable thermal structural materials. Based on compositional and structural design, Cf/HECs with outstanding load-bearing, ablation resistance, and electromagnetic shielding/absorption were obtained.
CG-2:IL17 Transition Metal Diborides and Solid Solution thereof for Future Space Missions
F. MONTEVERDE1, S. MUNGIGUERRA2, S. CASSESE2, R. SAVINO2, 1ISSMC-CNR, Faenza, Italy; 2DII-University of Naples Federico II, Naples, Italy
Atmospheric entry into Earth or planetary atmospheres (e.g. Mars) are characterized by extremely aggressive aero-thermo-chemical environments, requiring out-performing materials for spacecrafts thermal protection systems. Diborides and solid solutions thereof containing IV-V-VI group metals are actively investigated as material candidates. The high energy levels also trigger non-equilibrium reactive gas conditions and exothermic recombination reactions of the atoms on the exposed surfaces. The present contribution shows a range of activities using a ground entry simulator in environments representative of Earth (N2+O2) and Mars (N2+CO2). Optical emission spectroscopy and non-intrusive infrared diagnostics supported by CFD simulations were jointly used for a complete characterization of the non-equilibrium aero-thermo-dynamics of the flow, of non-catalytic and fully catalytic heat loads, as well as the high-temperature response of materials in representative flight conditions.
CG-2:IL18 Grain Growth and Its Inhibition in High-entropy Ceramics
JI-XUAN LIU, GUO-JUN ZHANG, State Key Laboratory of Advanced Fiber Materials, Institute of Functional Materials, Donghua University, China
Grain refinement is crucial for enhancing mechanical and functional properties in ceramics. High-entropy ceramics—emerging materials with multi-principal cations including borides (HEBs), carbides (HECs), and oxides (HEOs)—exhibit exceptional hardness, thermal stability, and low thermal conductivity. Controlling sintering-driven grain growth is essential to realize their potential. This work investigates grain-growth inhibition in HEBs, HECs, and HEOs via three strategies: (1) Adding SiC particles pins grain boundaries, refining HEB and HEC microstructures. (2) Incorporating Si in HECs forms a transient liquid phase, lowering sintering temperatures (reducing growth driving force), while in-situ generated SiC particles further inhibit growth via pinning. (3) Designing dual-phase ceramics (e.g., HEB/HEC composites; high-entropy zirconate/aluminates) enables mutual grain-boundary pinning between phases, yielding refined/stabilized microstructures versus single-phase materials. Collectively, extrinsic phases (SiC), in-situ phases (SiC from Si), and dual-phase architectures provide versatile routes to control grain size, enhance homogeneity, and unlock superior performance of high-entropy ceramics.
CG-2:L20 Material Design, Fabrication and Properties of High-entropy RE2Si2O7 Ceramics for Environmental Barrier Coatings
LUCHAO SUN, JINGYANG WANG, Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
Environmental barrier coatings (EBCs) have been developed to improve the durability of SiCf/SiC CMC components against harsh combustion environment. Among the most promising EBC candidates, rare-earth disilicates (RE2Si2O7) have been attracting attention due to their low thermal expansion coefficient, excellent high temperature water vapor resistance, and good thermal and chemical compatibility with silicon-based ceramics and composites. However, controlling the phase formation capability of RE2Si2O7 remains a crucial challenge, due to the complex polymorphic phase competitions and evolutions led by different RE3+ combinations. Guided by this descriptor, we successfully designed and fabricated several new RE₂Si₂O₇ silicate environmental barrier coatings (EBCs), which demonstrate outstanding high-temperature stability and corrosion resistance. The current research highlights the significant advantages of high-entropy engineering in developing advanced environmental barrier coatings (EBCs) for high-temperature applications, particularly demonstrating enhanced CMAS (Calcium-Magnesium-Alumino-Silicate) resistance in engine operational environments.
Session CG-3 Functional properties and applications
CG-3:IL21 The Intersection of Energy, Entropy, and Exploration: Data-Driven Discovery of High-Entropy Materials
C. OSES, Johns Hopkins University, Baltimore, MD, USA
High-entropy materials, including oxides and halides, are opening transformative possibilities for hydrogen generation, fuel cells, catalysis, energy storage, waste-heat recovery, radioactive waste immobilization, and radiation tolerance. However, the immense combinatorial complexity of these systems presents significant challenges for discovery and optimization. We employ data-driven approaches rooted in thermodynamics and chemistry to accelerate materials exploration, integrating high-throughput simulation, machine learning, and experimental feedback in a closed-loop workflow. This strategy efficiently guides exploration toward stable, high-performance compositions. Case studies demonstrate robust agreement with experimental results in mapping phase stability and uncovering functional materials. By advancing closed-loop discovery, we highlight scalable pathways to next-generation materials for critical energy applications.
CG-3:L22 High-entropy CeO2-δ·(RE,La,Sm,Y)2O3 [RE=Dy,Gd] Transparent ceramics: Structural and Optical Properties
A. CHAUHAN1, A. FRICKEL2, S. BEGAND2, H. MATHIAS3, D. GALUSEK1,4, 1Centre for Functional and Surface Functionalized Glass, Alexander Dubcek University of Trencin, Slovakia; 2Fraunhofer Institute for Ceramic Technologies and Systems, Hermsdorf, Germany; 3Fraunhofer Institute for Ceramic Technologies and Systems, Dresden Germany; 4Joint Glass Centre of the IIC SAS, TnUAD and FChPT STU, Trencin, Slovakia
A single-phase high-entropy ceramic rare earth phosphor with the composition of CeO2-δ·(RE,La,Sm,Y)2O3 [RE=Dy,Gd] with single phase bixbyite structure (Space group Ia-3) synthesized by reactive sintering. The initial mixture of oxides was milled to obtain optimal particle size which subsequently consolidated by reactive sintering for 2 h, 6 h and 10 h at 1600 °C. The phase composition and morphological feature of the sintered samples were examined by X-ray powder diffraction and scanning electron microscopy. The sintered high entropy ceramics achieved the relative density of 99% and exhibited translucence in the visible wavelength range. Hot isostatic pressing was employed at 1600 °C for 8 h with 185 Mpa pressure to eliminate the residual porosity at grain boundaries and to improve the optical transparency. The results of photoluminescence and UV-visible spectroscopy indicated the potential application of the prepared high-entropy ceramics as a multi-wavelength emission phosphor suitable for white light applications. The CIE diagram revealed that upon excitation at 302 nm, the high entropy oxides CeO2-δ·(RE,La,Sm,Y)2O3 [RE=Dy, Gd] emit within the white region of the CIE color space.
CG-3:L23 Exploring Composition-Property Relationships in Multicomponent Li-Garnets
B. ZIMMERMANN, T. FUCHS, J. JANEK, M. LEPPLE, Justus Liebig University Giessen, Giessen, Hesse, Germany
In recent years a lot of effort has been put into designing materials suited for the application in novel all-solid Li-batteries. Being able to replace liquid electrolytes comes with advantages such as increased safety and higher energy densities. Li-garnets as a material class are promising for the application as solid electrolyte. They exhibit various favorable properties such as good ionic conductivity, high electrochemical stability and compatibility with Li metal. With Li7La3Zr2O12 as the most famous representative, garnets also offer three distinct cation sublattices. This, and their compositional flexibility, also makes them well suited for the so-called “high-entropy” concept as adding multiple elements in different combinations can influence properties such as redox stability and ionic conductivity. However, this leads to many different factors potentially influencing these key properties and the challenge of how to best exploit them. The goal of this work was to synthesize sets of multicomponent Li-garnets with a variety of different cations such as Hf, Ta, Nb, Sn, Ti and Ce on the Zr sublattice. With this, singular characteristics such as lattice parameter or Li site occupation can be selectively changed and their effects on the material properties can be studied.
CG-3:L24 Crystal Structure, Thermal Properties and Sustainability in Novel High-Entropy Zirconates for Thermal Barrier Coating Applications
G. BIANCHI, M. LEPPLE, Justus Liebig University Giessen, Giessen, Hessen, Germany
Gas turbines are and will be required in the aerospace industry due to their high power density. Therefore, improving their efficiency – that means, increasing the operating temperature – is fundamental to reduce their environmental impact. In order to increase the temperature, however, new coatings need to be developed to prevent the melting of the metal alloy of the blades. The state-of-the-art material for these coatings is the 7 wt% yttria stabilised zirconia (7YSZ), but above 1200 °C it decomposes into its equilibrium phases, leading to the spallation of the coating. In this work, novel rare-earth high-entropy zirconates have been investigated to overcome the temperature limitations posed by the 7YSZ. Their crystalline phase (pyrochlore or defect fluorite) was correlated with the radii of the cations in the structure in order to predict the formation of a single-phase material and to ease the development of new compositions. These high-entropy zirconates showed also improved thermal properties with respect to 7YSZ (e.g. lower thermal conductivity), making them promising as thermal barrier coatings. Lastly, the sustainability of the coatings was also tackled via using the rare-earth ore composition as starting material and/or substituting one of the rare earths with iron.
CG-3:L26 High-entropy Oxides as an Electrocatalyst and a Potential Photo-electrocatalyst for H2 Production
M. HIMANSHU1, M. SLIM2, I. RAYANE2, A. MOLL1, D. BERARDAN1, N. DRAGOE1, D. ZIGAH2, C. GOMES DE MORAIS2, JUNSOO HAN3, E. GAUDRY4, T. COTTINEAU5, E. MAISONHAUTE6, 1SP2M, ICMMO, Univ Paris Saclay, CNRS, Orsay, France; 2IC2MP, Université de Poitiers, CNRS, Poitiers, France; 3LISE, CNRS, Sorbonne Université, Paris, France; 4Université de Lorraine, CNRS, IJL UMR 7198, Campus Artem, Cedex Nancy, France; 5ICPEES UMR7515─CNRS─Université de Strasbourg, Strasbourg, France; 6IPCM CNRS, Sorbonne Université, Paris, France
High-entropy oxides (HEOx) are a new class of multi-cationic materials where five or more metal cations form a single-phase crystalline lattice. Their compositional complexity enables tunable structural and electronic properties, making them promising for catalytic and energy applications. In this study, high-entropy tungstates and titanates were synthesized via a top-down approach, yielding a single-phase crystalline structure confirmed by XRD and Raman analyses. TEM and EDX revealed nanoparticles below 30 nm with uniform elemental distribution, while UV–visible spectroscopy indicated visible-light-responsive band gaps. BET analysis showed a high specific surface area beneficial for enhanced catalytic activity. The multifunctional performance of these HEOx materials was evaluated for both photo- and electrocatalytic applications. Electrochemical and photoelectrochemical studies indicated promising redox behaviour, efficient charge transfer, and strong photoresponse under illumination. The visible-light-driven photocatalytic activity further demonstrated their potential for pollutant degradation and hydrogen generation, highlighting HEOx materials as robust and sustainable candidates for integrated solar-driven energy conversion systems.
Session CG-4 Theoretical and computational studies
CG-4:IL27 Predicted Properties of Interfaces in High Entropy Ceramics
D.W. BRENNER, S. DAIGLE, T. MD ANAMUL HAQUE, M. MOU, Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC, USA
Interfaces in ceramics can have a major influence on their thermal, mechanical and chemical properties. With a large variety of possible compositions that may not match the bulk, predicting and understanding interface properties in high entropy ceramics is a difficult challenge. Using Density Functional Theory calculations and atomic simulations with Machine Learning Interatomic Potentials, we have been exploring the properties of stacking faults, grain boundaries, twins, partial dislocations and inter-phase regions in several high-entropy transition metal carbides and di-borides. We find that a combination of strain energy and chemistry via carbon vacancies can have a profound influence on interface composition and dislocation mobility, and that these in turn can influence mechanical properties. This talk will review these concepts and provide some recent examples of new insights from our computational studies.
CG-4:IL28 Design of Refractory High-entropy Materials for Extreme Environment by using CALPHAD
YUTARO ARAI, RYO INOUE, Tokyo University of Science, Tokyo, Japan
Components of hypersonic vehicles are exposed to temperatures exceeding 2000℃ in an oxidizing atmosphere due to aerodynamic heating during hypersonic cruising (Mach > 5). As candidate materials for such components, ultra-high-temperature ceramics (UHTCs)—including transition metal diborides, carbides, and nitrides with melting points above 3000℃—and ultra-high-temperature ceramic matrix composites (UHTCMCs) have attracted significant attention. In addition to these materials, refractory high-entropy ceramics (RHECs) and their composites have also been considered as potential candidates, and their fundamental properties have been evaluated. However, designing high-entropy materials solely through experimental approaches is extremely challenging because their design involves considering combinations of five or more constituent elements. The objective of this study is to develop design guidelines for refractory high-entropy ceramics and their composites as potential materials capable of suppressing oxidative degradation over a broad temperature range, by utilizing thermodynamic calculations and simulations. Several design methodologies will be introduced in this presentation.
CG-4:IL29 Compositionally Complex Ceramics
JIAN LUO, University of California San Diego, La Jolla, CA, USA
This talk will first review a series of our studies of high-entropy ceramics (HECs), including equimolar five-component MB2 [Sci. Rep. 2016], MB [Scripta 2020], M3B4 [JAC 2021], MB4 [JECS 2021] and MB6 [JECS 2021] borides, perovskite [Scripta 2018] and YSZ-like fluorite [JECS 2018] oxides, and MSi2 [J. Materiomics 2019] and M5Si3 [Scripta 2022] silicides, along with single-phase intermetallic compounds that bridge high-entropy alloys and ceramics [Sci. Bull. 2019]. In 2020, we further proposed extending the concept of HECs to “compositionally complex ceramics (CCCs)” [JECS 2020; JMS 2020], in which non-equimolar compositions and the presence of long- or short-range order reduce entropy while offering new opportunities to tailor and enhance properties, often beyond those of higher-entropy counterparts. We also reported the first dual-phase HECs/CCCs [JECS 2020]. We investigated long- and short-range orders, order-disorder transitions, and 10- to 21-component ultrahigh-entropy phases in fluorite-based CCCs [Acta 2021 & 2022; Scripta 2022; APM 2023; JECS 2024]. We studied compositionally complex perovskite oxides for solar thermochemical hydrogen generation [Chem. Mater. 2023] and as improved lithium-ion conductors via interfacial engineering [Matter 2023; JECS 2025; JAC 2025].
CG-4:L30 Lattice Distortion due to Oxygen Vacancies in MgO-based High Entropy Oxides from DFT
O. OPETUBO, TING SHEN, R. BORDIA, D. AIDHY, Department of Materials Science and Engineering, Clemson University, Clemson, SC, USA
High-entropy oxides (HEOs) consist of equi- or near-equimolar concentrations of multiple cations that are randomly distributed on a crystal lattice. The cations of different radii and electronegativities create intrinsic local lattice distortion. In addition, the presence of oxygen vacancies further contributes to the lattice distortion. Both distortions affect oxygen vacancy energetics, which is central to electrochemical properties in oxides. We investigate the intrinsic and oxygen-vacancy induced lattice distortion in Mg(CoNiCuZn)O using density functional theory (DFT). We elucidate that: (1) most of the intrinsic lattice distortion is induced by Cu, which is anchored in the Jahn-Teller distortion due to its d9 electronic structure, and (2) in the presence of oxygen vacancies, all cations except Cu move towards the vacancy, thereby reducing the vacancy volume, whereas the Cu atoms can move either way depending upon their initial intrinsic Jahn-Teller distortion. We characterize these distortions and show that they collectively affect the oxygen vacancy formation energies, validated by experiments, whereby the formation energies increase with the increase in the oxygen vacancy volume.This work advances the electronic level understanding of HEOs for electrochemical applications.