High-temperature Phase Stability Research Articles

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.

Type-1 Pentagonal Tiling Realized in 2D Penta-SrP2 Sheet.

According to the systematic classification of pentagon-based two-dimensional (2D) materials [ Phys. Rep. 2022, 964, 1], only type-2 and type-4 out of the 15 pentagonal tiling patterns have been realized in 2D materials so far. Here, we propose the first stable pentagon-based 2D material characterized by the type-1 pentagonal tiling pattern named penta-SrP2. We find that penta-SrP2 is not only thermally and mechanically stable but also dynamically stable when the temperature is above 200 K derived from the calculations by taking both phonon renormalization and thermal expansion into consideration. Moreover, the penta-SrP2 sheet is semiconducting with an indirect band gap of 0.96 eV. These findings expand the family of pentagon-based 2D materials in morphology and provide a new perspective to explore the dynamical stability of high-temperature phases.

Influence of various additions of Ti4+ substitution Ce4+ on high-temperature phase stability of co-precipitation Ti4+and Ce4+ co-doping YSZ powders

In this work, the Ce4+ and Ti4+ co-doped YSZ powders (Ce0.08-xTixY0.08Zr0.88O2.04) with various additions of Ti4+ substitution Ce4+ are prepared by the co-precipitation method. The microstructure, phase and chemical composition, phase transformation process, and phase stability after repeated calcination at 1300 °C of the powders have been investigated. The crystal structure of co-doping YSZ depends on the addition of Ti4+ substitution Ce4+ in the Ce0.08-xTixY0.08Zr0.88O2.04. When the doping molar ratio of Ce4+ to Ti4+ is 3:1 or 1:1, the ZrO2 can be stabilized to form the t′-phase and show better thermal stability, according to the TG-DSC and XRD results. Ti4+ enters the ZrO2 lattice in the form of substitution or interstitial. The oversized radius cation and undersized-radius cation co-stability can be induced by co-doping of Ti4+ and Ce4+. Thereby, the t′-ZrO2 is stabilized after repeated calcination at 1300 °C for 120 h. The co-doping of oversized radius cations and undersized-radius cations can further improve the t′-ZrO2 stability of YSZ, while the role of oversized radius cations is dominant.

Sc3+:Ce4+:Y3+ doped zirconia nanopowders (ScCeYSZ): Synthesis, thermal phase stability and hot corrosion behavior of spark plasma sintered body

This study aims to investigate the high-temperature phase stability and hot corrosion behavior of zirconia with triple doping of Sc3+, Ce4+ and Y3+ ions. FESEM result shows that the mean particle size of ScCeYSZ nanoparticles was 80–90 nm. Next, optimal samples regarding the highest high-temperature phase stability (1.9%Sc8.3%Ce1.8%YSZ, 1.1%Sc9.0%Ce1.8%YSZ and 0.5%Sc9.6%Ce1.8%YSZ) were consolidated at 1550 °C for 15 min via the spark plasma sintering (SPS) method. A hot corrosion test was done in the presence of 45%Na2SO4+%55V2O5 salts on three samples at 900 °C for 2 h. Also, the results of hot corrosion were compared with ceramic resulting from the nanostructured YSZ bulk sample (nanoYSZ).Based on the X-ray diffraction results, the formation of the non-transformable tetragonal phase is confirmed in the synthesized nanopowders. Also, the phase and microstructural results after hot corrosion of sintered samples show the formation of a monoclinic phase and destructive YVO4 crystals and quasi-cubic CeO2 crystals on the surface of sintered samples. The results indicated that the sample containing 1.8% scandia, 8.3% ceria, and 1.9% yttria had the highest phase stability and hot corrosion resistance (low monoclinic percentage and low leaching of stabilizer elements of Sc3+:Ce4+:Y3+ from zirconia lattice and low depth of molten salt).

Reciprocal space temperature-dependent phonons method from ab-initio dynamics

We present a robust reciprocal-space implementation of the temperature-dependent effective potential method, our implementation can scale easily to large cell and long sampling time. It is interoperable with standard ab-initio molecular dynamics and with Langevin dynamics. We prove that both sampling methods can be efficient and accurate if a thermostat is used to control temperature and dynamics parameters are used to optimize the sampling efficiency. By way of example, we apply it to study anharmonic phonon renormalization in weakly and strongly anharmonic materials, reproducing the temperature effect on phonon frequencies, crossing of phase transition, and stabilization of high-temperature phases.

Quantification of strain and its impact on the phase stabilization of all-inorganic cesium lead iodide perovskites

•CsPbI3 nanoplates are epitaxially grown on muscovite mica single-crystal substrates •Lattice strain is present and found to increase with decreasing nanoplate thickness •The strained epitaxy enhances the metastable perovskite high-T phase stability The high-temperature perovskite γ-phase of CsPbI3 readily undergoes phase transition at ambient conditions to a low-temperature non-perovskite δ-phase with a poorer optoelectronic performance, thus hindering commercialization of these materials in photovoltaics. Here, we present the epitaxial growth of CsPbI3 nanoplates on muscovite mica single-crystal substrates and demonstrate that the high-temperature phase stability of these nanoplates is enhanced by a strained interface. Strain is measured as a function of nanoplate thickness on a single-particle level through spatially resolved structural and optical characterizations and is found to increase with decreasing thickness. From quantitatively tracking the CsPbI3 phase transition for thin (<400 nm) and thick (>400 nm) nanoplates, we observe a larger fraction of thin nanoplates still maintaining their high-temperature phase after 1 month compared with their thick counterparts. These findings establish a relationship between strain and phase transition kinetics, which is critical for rational design of stable perovskite-based optoelectronic devices. The high-temperature perovskite γ-phase of CsPbI3 readily undergoes phase transition at ambient conditions to a low-temperature non-perovskite δ-phase with a poorer optoelectronic performance, thus hindering commercialization of these materials in photovoltaics. Here, we present the epitaxial growth of CsPbI3 nanoplates on muscovite mica single-crystal substrates and demonstrate that the high-temperature phase stability of these nanoplates is enhanced by a strained interface. Strain is measured as a function of nanoplate thickness on a single-particle level through spatially resolved structural and optical characterizations and is found to increase with decreasing thickness. From quantitatively tracking the CsPbI3 phase transition for thin (<400 nm) and thick (>400 nm) nanoplates, we observe a larger fraction of thin nanoplates still maintaining their high-temperature phase after 1 month compared with their thick counterparts. These findings establish a relationship between strain and phase transition kinetics, which is critical for rational design of stable perovskite-based optoelectronic devices.

Highly anti-sintering and toughened pyrochlore (Dy0.2Nd0.2Sm0.2Eu0.2Yb0.2)2Zr2O7 high-entropy ceramic for advanced thermal barrier coatings

Single-phase high-entropy rare-earth zirconate (Dy0.2Nd0.2Sm0.2Eu0.2Yb0.2)2Zr2O7 with excellent high-temperature phase stability at 1600 °C was designed and synthesized. After being heated at 1600 °C for 1 ∼ 50 h, the average grain size of the sample increases only from 0.74 μm to 2.22 μm, indicating a high anti-sintering ability. The fracture toughness is 2.07 ± 0.03 MPa m1/2 (25 °C), which is 50% higher than lanthanum zirconate. The local lattice distortions induced by the atomic interactions and atomic-size mismatch are considered to be responsible for the strong anti-sintering ability and improved fracture toughness. In addition, the thermal expansion coefficient and thermal conductivity of (Dy0.2Nd0.2Sm0.2Eu0.2Yb0.2)2Zr2O7 are 10.59 × 10-6 K-1 (25 ∼ 1500 °C) and 1.14 ± 0.09 W·m-1·K-1 (1500 °C), respectively. The outstanding combination of anti-sintering ability, mechanical behavior, and thermophysical properties of (Dy0.2Nd0.2Sm0.2Eu0.2Yb0.2)2Zr2O7 highlights its great potential for next-generation thermal barrier coating applications.

Fluorite-pyrochlore structured high-entropy oxides: Tuning the ratio of B-site cations for resistance to CMAS corrosion

As gas turbine inlet temperatures continue to rise, new thermal barrier coating (TBC) materials must be developed urgently. This work investigated molten silicate corrosion, thermal conductivity, and high-temperature phase stability of a new class of high-entropy oxides (HEO) as potential protective coating materials. With composition tuning, high-entropy RE2B2O7 (RE= Gd, Sm, Y, Pr, La; BCe, Zr) can be transformed from pyrochlore to fluorite structures. They all exhibited phase stability when annealed at 1600 ℃ for 10 h and very low thermal conductivity (1.21–1.39 W·m−1·K−1) compared to conventional materials with better thermal protection. In addition, the CMAS corrosion resistance behavior of all samples at 1300 °C and 1500 °C was investigated, and it was found that the infiltration thickness decreased with increasing Ce content (down to ∼10 µm for 5 h at 1500 °C). The RE2Ce2O7 had the most substantial CMAS resistance, forming a dense barrier layer composed of uniformly fine crystal grains during the reaction. The results of this study establish the foundation for future applications of RE2B2O7 in thermal protection systems.