High-temperature Phase Stability Research Articles

Clarifying the effects of composition and phase stabilization on the oxidation resistance in AlCoCrFeNiTi series high-entropy alloys at 1100 °C

The application of high entropy alloys in thermal barrier coating (TBC) systems offers a viable solution for mitigating interfacial instability arising from the elevated-temperature interdiffusion within the bonding layer/matrix. Nevertheless, the elucidation of phase stability under elevated temperatures and the intricate interplay among thermal-mechanical-chemical factors in HEAs remain lacks clarity. Herein, a set of AlxCo10.5Cr10Fe25Ni(50-x)Ti4.5 HEAs featuring desirable high-temperature phase stability, oxidation resistance, and spalling resistance at 1100 °C were meticulously designed. And the effects of phase composition and thermodynamics on the evolution of surface oxides in these HEAs were investigated. Specifically, the formation of the unfavorable σ phase between 860-1200 °C is avoided through the composition adjustment. The oxidation resistance is governed by the presence of large-size columnar grains and the spalling resistance of the Al2O3 oxide film. The spalling resistance is mainly linked to the configuration sequence (Spinel→FeAlTiO5→TiO2) of the outer oxide layer and the phase transition of the matrix either to FCC or BCC. Meanwhile, the formation of FeAlTiO5 assumes a crucial role in the optimization of spalling (>770h) and oxidation resistance (2.6×10-12g·cm-2·s-1) within an Al20Co10.5Cr10Fe25Ni30Ti4.5 alloy. These findings provide guidance for the development of TBC systems endowed with exceptional properties tailored for engineering applications.

Phonon transport manipulation in TiSe2 via reversible charge density wave melting

Titanium diselenide (TiSe2) is a layered material that under a critical temperature of Tc ≈ 200 K features a periodic modulation of the electron density, known as charge density wave (CDW), which finds applications in quantum information and emerging electronic devices. Here, we present first-principles calculations showing the suppression of the CDW via photoexcitation and consequent stabilization of the undistorted high-temperature phase, in agreement with experimental observations. Interestingly, the unfolded CDW melting is accompanied by a sizable reduction in the thermal conductivity, κ, of up to 25% and a large entropy increase of ~10 J K−1 kg−1. The significant κ variation is almost entirely originated from photoinduced changes in the phonon–phonon scattering processes involving a high-symmetry soft phonon mode. Our results open new possibilities in the design of devices for thermal management and phonon-based logic, and suggest original applications in the of context solid-state cooling.

Investigations on the mechanical and thermal properties of multicomponent dual-phase rare-earth zirconate ceramics

In this work, a series of multicomponent rare-earth zirconate (RE2Zr2O7, RE=La, Nd, Sm, Eu, Gd or Yb) ceramics were synthesized using solid-state reaction method. The phase stability and key factors affecting the thermal conductivity and mechanical performances were investigated. These materials possess pyrochlore-fluorite dual-phase structure and show excellent high-temperature phase stability. (La1/2Yb1/2)2Zr2O7 displays a lower amorphous-like thermal conductivity (1.39–1.67 Wm−1K−1, 25–1000 °C), while other specimens present a 1/T-like dependence at low temperatures. (La1/5Nd1/5Sm1/5Gd1/5Yb1/5)2Zr2O7 exhibit higher hardness (11.37 ± 0.35 GPa) and fracture toughness (2.10 ± 0.11 MPa·m1/2) in comparison with others. Size disorder shows stronger correlations with the thermal conductivity of multicomponent dual-phase RE2Zr2O7 ceramics, while the influence of configurational entropy is more significant for mechanical properties. A synergistic increase in configurational entropy and size disorder is an effective strategy to enhance the comprehensive performance of multicomponent dual-phase rare-earth zirconates.

Effect of Ceria Doping on the Mechanical Properties and Phase Stability of Partially Samaria-Stabilized Zirconia Crystals

The effect of ceria doping of (ZrO2)1−x(Sm2O3)x crystals on their phase composition, microhardness and fracture toughness was studied. The (ZrO2)0.995−x(Sm2O3)x(CeO2)0.005 crystals (where x = 0.032, 0.037 and 0.04) were grown using directional melt crystallization in a cold crucible. The mechanical properties, such as microhardness and fracture toughness, were explored using Vickers indentation. It was shown that the (ZrO2)0.995−x(Sm2O3)x(CeO2)0.005 solid-solution crystals contained both Ce4+ and Ce3+ ions. Phase analysis data suggested that CeO2 doping increased the tetragonality degree of the transformable t phase and reduced the tetragonality degree of the non-transformable t’ phase as compared to the (ZrO2)1−x(Sm2O3)x crystals. As a result, the t→m phase transition triggered by the indentation-induced stress in the CeO2-doped crystals was more intense and covered greater regions. CeO2 doping of the solid solutions increased the fracture toughness of all the crystals studied, whereas the microhardness of the crystals changed only slightly. CeO2 doping of the (ZrO2)1−x(Sm2O3)x solid solutions in the experimental concentration range did not improve the high-temperature phase stability of the crystals and did not prevent high-temperature degradation of their fracture toughness.

Microstructure and high-temperature phase stability of Co-precipitation (Mg0.2Al0.2Ce0.2Y0.2Zr0.2)O1.6 high entropy ceramics powders

(Mg0.2Al0.2Ce0.2Y0.2Zr0.2)O1.6 high entropy ceramics powders have been prepared by co-precipitation method with two calcination temperatures (1000 °C and 1200 °C). The microstructure, phase composition and phase stability after repeated calcination at 1400 °C with various times of the powders have been investigated. The powder calcined at 1200 °C has the better crystallinity and the stronger diffraction peak of t-ZrO2 phase at room temperature. The existence of Ce4+ and Y3+ with large radius in the ZrO2 lattice can enhance the tetragonality of the powders. The Mg2+ and Al3+ with small radii can exist in the lattice gap of ZrO2 or replace the position of Zr4+, causing lattice contraction, offsetting the lattice expansion which caused by Ce4+ and Y3+, and reducing the negative effects induced by the large ion doping. Thus, (Mg0.2Al0.2Ce0.2Y0.2Zr0.2)O1.6 has a good phase stability after repeated calcination at 1400 °C for 80h.

High-Temperature Oxidation and Phase Stability of AlCrCoFeNi High Entropy Alloy: Insights from In Situ HT-XRD and Thermodynamic Calculations.

The high-temperature oxidation behaviour and phase stability of equi-atomic high entropy AlCrCoFeNi alloy (HEA) were studied using in situ high-temperature X-ray diffraction (HTXRD) combined with ThermoCalc thermodynamic calculation. HTXRD analyses reveal the formation of B2, BCC, Sigma and FCC, phases at different temperatures, with significant phase transitions observed at intermediate temperatures from 600 °C-100 °C. ThermoCalc predicted phase diagram closely matched with in situ HTXRD findings highlighting minor differences in phase transformation temperature. ThermoCalc predictions of oxides provide insights into the formation of stable oxide phases, predominantly spinel-type oxides, at high p(O2), while a lower volume of halite was predicted, and minor increase observed with increasing temperature. The oxidation behaviour was strongly dependent on the environment, with the vacuum condition favouring the formation of a thin, Al2O3 protective layer, while in atmospheric conditions a thick, double-layered oxide scale of Al2O3 and Cr2O3 formed. The formation of oxide scale was determined by selective oxidation of Al and Cr, as further confirmed by EDX analysis. The formation of thick oxide in air environment resulted in a thick layer of Al-depleted FFC phase. This comprehensive study explains the high-temperature phase stability and time-temperature-dependent oxidation mechanisms of AlCrCoFeNi HEA. The interplay between surface phase transformation beneath oxide scale and oxides is also detailed herein, contributing to further development and optimisation of HEA for high temperature applications.

Effects of Y doping on phase structure, mechanical properties and sintering behavior of (Yb1-xYx)2SiO5 environmental barrier coating materials

Yb2SiO5 is one of the most widely studied environmental barrier coating materials due to its excellent high-temperature phase stability and resistance to water oxygen corrosion. In this paper, a series of (Yb1-xYx)2SiO5 (x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were fabricated by high-temperature solid state sintering at 1550 °C. The effects of Y doping concentration on phase composition, mechanical properties, thermal conductivity and high-temperature sintering behavior of Yb2SiO5 ceramics were investigated in detail. The results show that all the (Yb1-xYx)2SiO5 ceramic specimens are composed of single X2-Yb2SiO5 phase with relative high compactness. The introduction of Y gives rise to the reduction of the thermal conductivity of Yb2SiO5 and the value of cell parameters and volume of (Yb1-xYx)2SiO5 is proportional to the Y3+ doping concentration. Among the five (Yb1-xYx)2SiO5 ceramics, (Yb0.9Y0.1)2SiO5 possesses the lowest brittleness index and its average fracture toughness is 2.85 MPa m1/2, which is about 10 % higher than pure Yb2SiO5. In addition, (Yb0.9Y0.1)2SiO5 has good high temperature phase stability from room temperature to 1450 °C and the grain size of (Yb0.9Y0.1)2SiO5 is basically unchanged after sintering at 1400 °C for 100 h. We believe that (Yb0.9Y0.1)2SiO5 is one of the most promising candidate materials for environmental barrier coatings.

Stable preparation of defective fluorite structure high entropy (Y0.2Sm0.2Eu0.2Er0.2Yb0.2)2Zr2O7 ceramic powders by molten salt synthesis

Rare earth zirconate ceramic has been considered as one of the potential thermal barrier coating materials to replace 6–8% YSZ material (6–8% yttrium oxide stabilized zirconia), because of its low thermal conductivity and good high temperature phase stability. However, there is a problem that the coefficient of thermal expansion does not match the matrix. In this paper, rare earth high entropy zirconate ceramic powder with defective fluorite structure was prepared by molten salt synthesis(MSS). The results show that the reaction temperature and the ratio of reactants to molten salt will affect the synthesis effects. With the action of the high entropy effect, the synthesized ceramic powder has low thermal conductivity, improved thermal expansion coefficient and high infrared reflectivity.

Suppressing the oxygen-ionic conductivity and promoting the phase stability of the high-entropy rare earth niobates via Ta substitution

Improving and optimizing the target properties of ceramics via the high entropy strategy has attracted significant attention. Rare earth niobate is a potential thermal barrier coating (TBCs) material, but its poor high-temperature phase stability limits its further application. In this work, four sets of TBCs high-entropy ceramics, (Sm1/5Dy1/5Ho1/5Er1/5Yb1/5)(Nb1/2Ta1/2)O4 (5NbTa), (Sm1/6Dy1/6Ho1/6Er1/6Yb1/6Lu1/6)(Nb1/2Ta1/2)O4 (6NbTa), (Sm1/7Gd1/7Dy1/7Ho1/7Er1/7Yb1/7Lu1/7)(Nb1/2Ta1/2)O4 (7NbTa), (Sm1/8Gd1/8Dy1/8Ho1/8Er1/8Tm1/8Yb1/8Lu1/8) (Nb1/2Ta1/2)O4 (8NbTa) are synthesized using a solid-state reaction method at 1650 °C for 6 h. Firstly, the X-ray diffractometer (XRD) patterns display that the samples are all single-phase solid solution structures (space group C2/c). Differential scanning calorimetry (DSC) and the high-temperature XRD of 8NbTa cross-check that the addition of Ta element in 8HERN increases the phase transition temperature above 1400 °C, which can be attributed to that the Ta/Nb co-doping at B site introduces the fluctuation of the bond strength of Ta-O and Nb-O. Secondly, compared to high-entropy rare-earth niobates, the introduction of Ta atoms at B site substantially reduce thermal conductivity (reduced by 44 %, 800 °C) with the seven components high entropy ceramic as an example. The low thermal conductivity means strong phonon scattering, which may originate from the softening acoustic mode and flattened phonon dispersion in 5–8 principal element high entropy rare earth niobium tantalates (5–8NbTa) revealed by the first-principles calculations. Thirdly, the Ta/Nb co-doping in 5–8NbTa systems can further optimize the insulation performance of oxygen ions. The oxygen-ion conductivity of 8NbTa (3.31 × 10−6 S cm−1, 900 °C) is about 5 times lower than that of 8HERN (15.8 × 10−6 S cm−1, 900 °C) because of the sluggish diffusion effect, providing better oxygen barrier capacity in 5–8NbTa systems to inhibit the overgrowth of the thermal growth oxide (TGO) of TBCs. In addition, influenced by lattice distortion and solid solution strengthening, the samples possess higher hardness (7.51–8.15 GPa) and TECs (9.78 × 10−6 K−1–10.78 × 10−6 K−1, 1500 °C) than the single rare-earth niobates and tantalates. Based on their excellent overall properties, it is considered that 5–8NbTa can be used as auspicious TBCs.

(Gd0.2Ho0.2Er0.2Yb0.2Lu0.2)2Si2O7 and (Sc0.2Ho0.2Er0.2Yb0.2Lu0.2)2Si2O7 high-entropy rare-earth disilicates as promising materials for environmental barrier coatings

The novel potential environmental barrier coating materials, two high-entropy rare earth disilicates (HEDs) (Gd0.2Ho0.2Er0.2Yb0.2Lu0.2)2Si2O7 and (Sc0.2Ho0.2Er0.2Yb0.2Lu0.2)2Si2O7 were prepared by the solid-phase method. Both the HEDs showed remarkable high-temperature phase stability and an appropriate thermal expansion coefficient (CTE) that matched that of SiCf/SiC. In addition, both the HEDs possessed above 20% lower thermal conductivity at 1000 °C (1.37 and 1.42 W·m−1·K−1, respectively) compared to traditional single-component rare earth disilicate material YbDS, and they also exhibited higher mechanical properties and good resistance to water vapour corrosion at 1300 °C. Moreover, the corresponding free-standing coatings obtained after deposition by atmospheric plasma spraying (APS) showed excellent resistance to CMAS corrosion, primarily because of the formation of an apatite layer.

Mechanical and thermal properties evaluation of Eu2O3-Gd2Zr2O7 ceramics served as potential neutron absorber rod

Rare earth compounds (RE2O3), typically Eu2O3 and Gd2O3, are considered as absorbing materials due to their long chain neutron absorbing ability and high efficiency of neutron absorption. In this paper, a specifically designed xEu2O3-(1-x)Gd2Zr2O7 (x = 0.6, 0.7, 0.8, 0.85) composite ceramics with excellent thermal properties were synthesized through direct thermal decomposition reactions followed a high-temperature sintering method under vacuum conditions. X-ray diffraction (XRD) and Raman spectroscopy analysis indicated that the obtained ceramics consisted of monoclinic Eu2O3 and fluorite Gd2Zr2O7 phases. The hardness of xEu2O3-(1-x)Gd2Zr2O7 ceramics (x = 0.8, 0.85) have no significantly changes in the test temperature range (25–350 °C). The thermal expansion coefficients (TECs) (7.3–10 ×10-6 K-1) are lower than Dy2TiO5 (9.3–10.4 ×10-6 K-1), and the thermal expansion rate changes linearly with the increase of temperature, which indicates that the xEu2O3-(1-x)Gd2Zr2O7 ceramics exhibit excellent high temperature phase stability. Furthermore, the range of thermal conductivities is from 0.96 W·m-1·K-1 to 2.02 W·m-1·K-1 (25–800 °C), which is higher than Dy2TiO5 (0.27–0.55 W/m·K, 220–650 °C). Compared with the state-of-art Dy2TiO5 ceramics, xEu2O3-(1-x)Gd2Zr2O7 have superior thermal properties and are therefore expected to be the next generational of neutron absorbent materials used in ash rod.

Microstructural, Phase, and Thermophysical Stability of CrMoNbV Refractory Multi-Principal Element Alloys

Structural survivability of refractory multi-principal element alloys (RMPEAs) at high temperatures hinges on a combination of microstructure, phase, and thermophysical stabilities. In this study, we investigate the high-temperature stability of three compositions from the CrMoNbV system: Cr7Mo18Nb35V40, Cr25Mo25Nb25V25, and Cr40Mo45Nb10V5. The microstructure, high-temperature phase stability, coefficient of thermal expansion (CTE), and yield strength were evaluated up to 1300oC. Results show that all three as-cast compositions have dendritic microstructures with an average grain size of ~100µm and no preferred texture. High-temperature analysis of phase stability shows that Cr7Mo18Nb35V40 maintains a single-phase BCC structure from room temperature up to 1300oC, while Cr25Mo25Nb25V25 forms an undesirable C15 Laves phase and Cr40Mo45Nb10V5 exhibits BCC phase separation. The CTE measured was 9.58, 9.52 and 8.80 ppm/oC, and the yield strength at 1250oC was 503, 629 and 628MPa for Cr7Mo18Nb35V40, Cr25Mo25Nb25V25 and Cr40Mo45Nb10V5, respectively. The low density, CTE and high-temperature yield strength of the three alloys sets the CrMoNbV system above current superalloys. More importantly, the microstructural, phase, and thermophysical stabilities of the Cr7Mo18Nb35V40 alloy over the equiatomic and Cr-rich alloys highlight the importance of high-temperature survivability over yield strength as an RMPEA design principle.

High-temperature phase stability of Y2O3 and SiO2 co-doped ZrO2 powder

High-temperature phase stability of Y2O3 and SiO2 co-doped ZrO2 powder

High-temperature phase stability and phase transformations of Niobium-Chromium Laves phase: Experimental and first-principles calculation studies

The high-temperature phase stability of the NbCr2 Laves phase has not yet been established beyond disagreement. The well accepted C14 phase field has been eliminated from the Nb-Cr phase diagram in a recent study that claimed that the NbCr2 alloy shows the C15 structure up to melting. The present study was conducted to address these ambiguities. The experimental investigations show the presence of C14, C15, and C36 structures in the as-cast alloy. Differential scanning calorimetry studies of the as-cast alloy show the transformation of the eutectic mixture of bcc + NbCr2 to single-phase NbCr2 at 1338 K. An in-situ X-ray diffraction (XRD) study of as-cast alloy shows a phase transformation of C36 → C14 below 1273 K. Density functional theory (DFT) calculations confirm two phase transformations: (a) a metastable transformation of C36 → C14 at 783 K and (b) an equilibrium transformation of C15 → C14 at 1971 K, which was validated by high temperature DTA and TEM studies. Further, extended DFT calculations on supercells with four compositions of NbCr1.9, NbCr2, NbCr2.1, and NbCr2.2 also corroborated the presence of the C14 phase, and consequently, the Nb-Cr phase diagram is modified. This finding resolves the controversy regarding the existence of an equilibrium C14 phase field before melting.

Efficient single-step Cool-SPS processing of Mn3O4 ceramics at 400 °C with persistent magnetodielectric coupling

Spinel type Mn3O4 oxide ceramics possess intriguing magnetodielectric properties, but traditional processing routes can be frustrated by limited high temperature phase stability. Using a low temperature (≤400 °C) electric field assisted processing route (Cool-SPS), a highly cohesive Mn3O4 ceramic is achieved. Reactive manganese oxide-hydroxide precursor powder is converted into the targeted Mn3O4 with a single step process under strategically selected conditions. Detailed X-ray diffraction studies, including variable temperature and atmosphere measurements, plus in-situ monitoring of processing parameters, have been combined to map and optimize SPS processing parameters. The microstructure evolution from precursor to ceramic was examined by electron microscopy, while extensive magnetic and dielectric measurements were performed to study the complex physical behavior of Mn3O4 at low temperature (<43 K). The efficacy of this Cool-SPS processing approach for Mn3O4 is demonstrated by the observed ceramic properties, including a hysteretic magnetic-field dependent dielectric response which supports the existence of a magnetoelectric coupling.

Effect of Gd doping on phase evolution, mechanical and thermal characteristics of 1La-xGd-2Yb-3.5YSZ solid solutions

Thermal barrier coatings (TBCs) are critical for the reliability and lifespan of aircraft engine turbine blades. In this study, a novel quaternary rare-earth oxide (La2O3, Gd2O3, Yb2O3, and Y2O3) co-doped ZrO2 solid solution, referred to as 1La-xGd-2Yb-3.5YSZ, was synthesized by varying the doping amount of Gd2O3 from 0 to 6 mol. %. The impact of co-doping-induced lattice distortion on the phase composition, high-temperature phase stability, sintering resistance, and mechanical and thermal properties of the solid solution has been explored. It is found that the addition of Gd2O3 stabilizer effectively increased the lattice distortion of the solid solution, which led to improved phase stability and sintering resistance, enhanced mechanical properties, and low thermal conductivity. Our findings highlight the promising properties of the 1La-xGd-2Yb-3.5YSZ solid solution, making it an attractive candidate for TBC materials.

Phase evolution, thermophysical and mechanical properties of high-entropy (Ce0.2Nd0.2Sm0.2Eu0.2Yb0.2)2Zr2O7 ceramic for advanced thermal barrier coatings

Single-phase high-entropy rare-earth zirconate (Ce0.2Nd0.2Sm0.2Eu0.2Yb0.2)2Zr2O7 with large thermal expansion coefficient (11.69 ×10−6 K−1, 25–1500 °C), low thermal conductivity (1.07 W m−1 K−1, 1500 °C), and high fracture toughness (1.84 ± 0.03 MPa m1/2, 25 °C) was successfully synthesized using reverse coprecipitation and high-temperature calcination. The underlying mechanism governing the observed results was analyzed by considering the ionic bond strength, crystal lattice energy, and bond length. X-ray diffraction and Raman spectroscopy results demonstrated that the pyrochlore structured sample has excellent high-temperature phase stability. Moreover, after being heated at 1600 °C for 10–30 h, the average grain size of this sample only increases from 0.95 µm to 1.47 µm, indicating a sluggish grain growth rate. The outstanding combination of thermophysical and mechanical properties of the (Ce0.2Nd0.2Sm0.2Eu0.2Yb0.2)2Zr2O7 emphasizes its enormous potential for next-generation thermal barrier coating applications.

Structure, thermal and mechanical properties of mid-entropy thermal barrier ceramic (Y0.3Gd0.3Yb0.4)4Hf3O12 prepared by ultrafast high-temperature sintering

Thermal barrier coatings (TBCs) have an important role to play in the development of aero engines. In this paper, mid-entropy rare-earth hafnate (Y0.3Gd0.3Yb0.4)4Hf3O12(YGYbH) ceramic material was designed based on rRE3+/rHf4+ and was successfully fabricated in only 7 min using an ultrafast high-temperature sintering (UHS) process. The YGYbH ceramic bulk exhibits a single homogeneous fluorite structure and excellent high temperature phase stability, which can remain phase constant for 80 h at 1500 °C due to its unique cation radius ratio and high-entropy effect. YGYbH possesses sluggish grain growth characteristics and great anti-sintering properties, and when annealing at 1500 °C for 30 h, its grain size only grows from the initial 1.19 μm–1.61 μm, which is conducive to stabilizing the mechanical properties of YGYbH at higher service temperature. YGYbH has a low thermal conductivity of 0.89 W/(m·k) at 1100 °C, which is much lower than that of 6%–8%Y2O3 partially stabilized ZrO2(YSZ) (∼2.5 W/(m·k)), while having a high coefficient of thermal expansion (CTE), from 8.8 × 10−6/K at room temperature to 11.0 × 10−6/K at 1500 °C which is nearly to that of the YSZ. Furthermore, YGYbH has a high hardness (11.94 GPa) and a low elastic modulus (147.4 GPa), but a slightly lower fracture toughness (1.26 MPa m½) than that of 8YSZ, exhibiting great overall mechanical properties. Based on the results of this work, YGYbH with excellent overall performance exhibits great potential as the next-generation TBC material.

Multiscale defect-mediated thermophysical properties of high-entropy ferroelastic rare-earth tantalates

The foremost objective of this work is to employ an entropy strategy to optimize the thermophysical properties of rare-earth (RE) tantalates. The stabilizing single-phase structure of seven-component rare-earth tantalates is verified by density functional theory calculations, and entropy-stabilized (7RE1/7)TaO4 with a defective structure is successfully synthesized via spark plasma sintering. (7RE1/7)TaO4 exhibits lower intrinsic thermal conductivity over the entire temperature range from 100 to 1200 °C. Furthermore, its intrinsic thermal conductivity (0.83–0.90 W m−1·K−1) is 39–51% and 68–71% lower compared to those of single-RE RETaO4 and 8YSZ at 1200 °C, respectively, and is even close to the limited thermal conductivity from the Cahill model. This is the result of multiscale phonon scattering by Umklapp phonon-phonon, point defect, dislocation, ferroelastic domain and distorted structures. Moreover, (7RE1/7)TaO4 exhibits superior high-temperature phase stability and excellent mechanical properties. Therefore, entropy-stabilized (7RE1/7)TaO4 compounds with ultralow thermal conductivity can be used as promising thermal insulating materials.

Potential thermal barrier coating material: High entropy ceramic (Ca0.5Sr0.5)(5RE)2O4 with enhanced thermophysical properties

Single-phase high entropy ceramic (Ca0.5Sr0.5)(5RE)2O4 (RE = Y, Sm, Gd, Dy, Yb) (CSHO) with anti-spinel structure was synthesized via solid-state reaction method. The CSHO has good high-temperature phase stability at 1600 °C for 10–50 h. In addition, the CSHO ceramics exhibit much lower thermal conductivity and higher thermal expansion coefficient than that of SrY2O4, towing to the intensified phonon-point defect scattering and the enhanced anharmonic vibrations of the lattice. The thermal conductivity of CSHO is 1.48–1.81 W∙m−1 K−1 (25–1500 °C), and the thermal expansion coefficient is 11.5–12.0 × 10−6 K−1 (1000–1500 °C). The obtained results suggest that CSHO has the potential to become the next-generation thermal barrier coating materials.