A high-entropy cerate ceramic for thermal barrier coating and its preparation method

Abstract

This invention discloses a high-entropy cerate ceramic for thermal barrier coating and its preparation method. Specifically, this invention provides a high-entropy cerate ceramic whose chemical composition is represented by the following general formula: (A) 0.2 Pr 0.2 Eu 0.2 Gd 0.2 Yb 0.2 )2Ce2O7; wherein, A is selected from Y, Nd, and Sm. The high-entropy cerate ceramic material prepared by this invention has both low thermal conductivity and high coefficient of thermal expansion, which can meet the performance requirements of the thermal barrier coating of next-generation aero-engines.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature protective materials technology, and particularly relates to a high-entropy cerate ceramic for thermal barrier coating and its preparation method. Background Technology

[0002] While existing high-entropy cerates such as (LaNdSmEuGd)₂Ce₂O₇ exhibit low thermal conductivity at 1000℃, they still suffer from lattice distortion relaxation and oxygen vacancy ordering issues during long-term service above 1200℃, leading to a rebound in thermal conductivity and a decrease in the coefficient of thermal expansion. Furthermore, existing systems primarily utilize elements such as La and Yb; there are no reports of constructing high-entropy cerates using Pr, Eu, Gd, Yb, or Y / Nd / Sm synergies and systematically studying their thermo-structural stability above 1200℃. Summary of the Invention

[0003] The purpose of this invention is to provide a high-entropy cerate ceramic material for thermal barrier coatings that combines low thermal conductivity and high coefficient of thermal expansion, and to provide a reproducible synthesis method suitable for large-scale preparation, so as to meet the performance requirements of thermal barrier coatings for next-generation aero-engines.

[0004] Therefore, the present invention provides a high-entropy cerate ceramic for thermal barrier coating, wherein the chemical composition of the high-entropy cerate ceramic is represented by the following general formula: (A 0.2 Pr 0.2 Eu 0.2 Gd 0.2 Yb 0.2 )2Ce2O7; wherein A is selected from one of Y, Nd, and Sm, and the ceramic is a single-phase defect fluorite structure with a thermal conductivity of less than 1.40 W·m at 1200℃. -1 ·K -1 The coefficient of thermal expansion is higher than 12.5 × 10⁻⁶. -6 / K, and the phase structure remains unchanged after heat treatment in air at 1600℃ for 100 hours.

[0005] Another aspect of the present invention provides a method for preparing high-entropy cerate ceramics for thermal barrier coatings, comprising the following steps:

[0006] S1. Raw material pretreatment: Pretreatment of raw materials containing Ce2O3, Eu2O3, Yb2O3, Gd2O3, and Pr6O 11 All raw material powders, including oxides of element A, are pre-calcined. S2. Batching and mixing: Weigh each raw material powder after step S1 according to the stoichiometric ratio of the general formula described in claim 1, and mix it together with the ball milling media and dispersant to obtain a uniform slurry; S3. Drying and pre-firing: Drying and pre-firing: After drying the slurry, a mixed powder is obtained, and pre-firing is carried out at 1300℃ to 1400℃ to obtain high-entropy ceramic initial powder;

[0007] S4. Secondary processing: The high-entropy ceramic powder is subjected to secondary ball milling, drying, and sieving to obtain high-entropy ceramic powder; S5. Rapid hot pressing sintering: The high-entropy ceramic powder is heated to 1450-1550℃ within 10 minutes and held at 30-50 MPa pressure for 10-30 minutes to obtain high-entropy cerate ceramic bulk material.

[0008] Specifically, in step S2, the ball milling speed is 200 rpm to 300 rpm, and the ball milling time is 2 hours to 4 hours.

[0009] Specifically, in step S3, the heat preservation time for pre-sintering is 1 to 3 hours.

[0010] Principles and advantages

[0011] Compared with existing high-entropy cerates (such as La and Yb-containing systems), this application introduces Pr as a fixed component for the first time, utilizing its Pr 3+ / Pr 4+ The dynamic adjustment capability of valence state, combined with the medium-size buffering effect of Eu and Gd and the stabilizing effect of Yb's high electronegativity, significantly improves the high-temperature phase stability and the matching of thermal expansion coefficients while maintaining low thermal conductivity. In particular, the introduction of Pr solves the problem of existing high-entropy cerates under high-temperature reducing atmospheres for Ce. 4+ The bottleneck issue of easy restoration.

[0012] This application selects five trivalent rare earth ions to form a complete ionic radius spectrum covering large, medium, and small sizes, creating a strong size disorder effect. Among them, Nd (when the A-site is selected) and Pr are large-sized rare earth ions, while Yb is a typical small-sized rare earth ion. The extreme ionic size contrast between the two induces a high-intensity, widely distributed lattice strain field within the fluorite lattice, strongly scattering phonons and blocking phonon transport paths, thereby reducing lattice thermal conductivity at its source. Eu and Gd are medium-sized rare earth ions, acting as buffer cores. They can both enhance the distortion effect at intermediate scales, fill the radius distribution gaps, and make the ionic radius arrangement continuous and smooth, and buffer the lattice stress caused by extreme size differences, strictly controlling the degree of distortion within the solid solution tolerance of ±15% of the fluorite structure, preventing phase separation caused by excessive stress. The equimolar ratio of the five elements makes the system's size disorder parameter significantly higher than that of binary and ternary doped systems, maximizing the degree of lattice distortion, optimizing the phonon scattering effect, and bringing the lattice thermal conductivity close to the theoretical minimum value, achieving highly efficient thermal insulation. Meanwhile, the random arrangement of ions of various sizes breaks the periodicity of the crystal lattice, further weakens the mean free path of phonons, and enhances the low thermal conductivity.

[0013] This application leverages the electronegativity differences among five rare earth ions to construct a continuous electronegativity gradient, achieving both complementary electronic structures and dual valence state stability. Low electronegativity rare earth ions (Nd, Sm, Pr) can enhance the ionicity of the Ce-O bond, effectively suppressing Ce under high-temperature reducing atmospheres. 4+ To Ce 3+ The reduction transformation avoids structural collapse caused by abnormal fluctuations in Ce valence state; high electronegativity Yb 3+ It can significantly increase the lattice oxygen binding energy, enhance the chemical stability of the fluorite phase, and firmly lock in lattice oxygen under extreme environments of low oxygen partial pressure and high temperature, maintaining the integrity of the crystal structure. Neutral electronegative Gd 3+ Eu 3+ It acts as a charge balance hub, uniformly dispersing the system charge and avoiding cation segregation and ordering caused by local charge mismatch. Meanwhile, Pr 3+ / Pr 4+ It can achieve dynamic adjustment of valence state, further compensate for the charge imbalance of the system, stabilize the crystal structure and ionic valence state of solid solution in all aspects, and eliminate the problems of valence state abrupt change and structural instability at high temperature.

[0014] In this application, trivalent rare earth ions are substituted for Ce. 4+ Oxygen vacancies are spontaneously generated through charge compensation effects. The formation energies of oxygen vacancies differ significantly among different rare earth ions, allowing for precise control of defect concentration. Large-sized rare earth ions (Nd, Pr) have low oxygen vacancy formation energies, readily generating oxygen vacancies, which further reduce thermal conductivity through vacancy scattering; small-sized Yb... 3+ High oxygen vacancy formation energy can suppress the generation of excess vacancies; medium-sized Gd 3+ Eu 3+By coordinating and regulating the vacancy generation kinetics, the total oxygen vacancy concentration is strictly controlled below the critical threshold. This differentiated defect design can fully utilize the oxygen vacancy scattering effect to enhance the low thermal conductivity characteristics, while also suppressing vacancy aggregation, migration, and ordering at high temperatures. This avoids lattice relaxation, abnormal thermal expansion, and structural damage caused by excessive vacancy aggregation, ensuring long-term structural stability during high-temperature service.

[0015] By reverse pairing large and small rare earth ions, the coefficient of thermal expansion (CTE) of the system can be precisely controlled. Large ions (Nd, Pr) contribute high CTE, while small ions (Yb) contribute low CTE. 3+ Equimolar mixing, combined with medium-sized Eu and Gd buffers, adjusted the coefficient of thermal expansion of the system to 12.5-13.0 × 10⁻⁶. -6 / K, which is highly compatible with the thermal expansion properties of the high-temperature alloy substrate.

[0016] Meanwhile, the five-element high-entropy configuration brings a strong lattice anharmonic effect, which can slightly increase the coefficient of thermal expansion in the high-temperature range, further reduce the thermal expansion gap between the coating and the substrate, alleviate the thermal stress mismatch during heating and cooling, reduce the initiation of thermal fatigue cracks, and improve the coating's thermal shock resistance and service life.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. Through a high-entropy design using five rare earth elements (including Pr, Eu, Gd, Yb, and A) and Ce, while maintaining low thermal conductivity (<1.40 W·m), -1 ·K -1 While achieving a high coefficient of thermal expansion (>12.5×10 at 1200℃), it also obtained a high coefficient of thermal expansion (>12.5×10). -6 / K), which has better compatibility with high-temperature alloy substrates.

[0019] 2. It adopts the classic solid-state reaction method and ball milling process, the raw materials are readily available, the process parameters are wide-ranging, and it is easy to achieve precise control of composition and structure, making it suitable for large-scale production. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This refers to the change in thermal conductivity of Example 1 at different temperatures;

[0022] Figure 2 The coefficient of thermal expansion of the embodiment;

[0023] Figure 3 XRD patterns of the ceramic prepared in Example 1 before and after annealing at 1600°C for 100 hours. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The present invention provides a high-entropy cerate ceramic for thermal barrier coating, wherein the chemical composition of the high-entropy cerate ceramic is represented by the following general formula: (A) 0.2 Pr 0.2 Eu 0.2 Gd 0.2 Yb 0.2 )2Ce2O7; where,

[0026] A is selected from any one of Y, Nd, and Sm. The ceramic has a single-phase defect fluorite structure and a thermal conductivity of less than 1.40 W·m at 1200℃. -1 ·K -1 The coefficient of thermal expansion is higher than 12.5 × 10⁻⁶. -6 / K, and the phase structure remains unchanged after heat treatment in air at 1600℃ for 100 hours.

[0027] The raw materials for high-entropy cerate ceramics are Ce₂O₃, Eu₂O₃, Yb₂O₃, Gd₂O₃, and Pr₆O₃. 11 The rare earth oxides, one of Sm2O3, Y2O3, and Nd2O3 (purity ≥99%), are sintered at 1300℃ to 1400℃ under a pressure of 30-50 MPa for 10-30 minutes. The thermal conductivity and coefficient of thermal expansion of the resulting sintered body are then analyzed. This application achieves the initial formation and composition homogenization of a high-entropy solid solution through a first sintering process. After eliminating hard agglomerates through a second ball milling process, rapid hot pressing sintering is used to achieve densification in a short time, avoiding abnormal grain growth, thereby obtaining a dense ceramic block with both low thermal conductivity and high coefficient of thermal expansion.

[0028] The five rare earth elements selected in this invention—Pr, Yb, Eu, Gd, and A (Y / Nd / Sm)—form an irreplaceable complementary gradient in three key physicochemical parameters: ionic radius, electronegativity, and oxygen vacancy formation energy. The absence or substitution of any element will disrupt the integrity of the large-medium-small radius spectrum, electronegativity gradient, or oxygen vacancy formation energy gradient, preventing the material from simultaneously achieving the synergistic optimization of the three key properties: low thermal conductivity, high coefficient of thermal expansion, and high-temperature structural stability.

[0029] The irreplaceability of the key elements in this invention can be summarized in the following four dimensions. Each element plays a unique and synergistic role in the composition, and its replacement or absence will disrupt the synergistic optimization mechanism of low thermal conductivity, high coefficient of thermal expansion, and high-temperature stability of the material.

[0030] I. The Irreplaceability of Ionic Radius Dimension

[0031] Pr Large size (~1.13 Å) The combination of large-size ions at the A site to create extreme ion size contrast induces a high-intensity lattice strain field and enhances phonon scattering, which is one of the key sources for achieving ultra-low thermal conductivity. Yb Small size (~0.98 Å) It provides the other end with size contrast, forming the maximum radius difference with the smaller end, and at the same time stabilizes the lattice oxygen through high electronegativity, thus having the dual functions of structural stability and thermal conductivity regulation. Eu / Gd Medium size (~1.07 / 1.05 Å) It fills the gaps between large and small sizes, makes the ion radius distribution continuous and smooth, buffers the lattice stress caused by extreme size differences, and prevents phase separation. It is the "buffer core" that maintains the single-phase fluorite structure.

[0032] Irreplaceable core: If any size segment of ions is missing, a continuous radius spectrum of "large-medium-small" cannot be formed, and lattice distortion intensity and structural stability cannot be achieved simultaneously.

[0033] II. The Irreplaceability of Electronegativity and Valence Dimension

[0034] Pr <![CDATA[Low electronegativity, Pr 3+ / Pr 4+ Variable valence]]> <![CDATA[It has both low electronegativity (enhancing the ionic nature of the Ce-O bond) and the ability of valence state dynamic regulation, which can compensate for the charge imbalance in the system under a high-temperature reducing atmosphere and prevent the lattice instability caused by the reduction of Ce]] 4+ Other rare earths are difficult to have these two characteristics simultaneously.]]> Yb High electronegativity (~1.1) Significantly increasing the lattice oxygen binding energy, "locking in" lattice oxygen under low oxygen partial pressure and high temperature conditions, and maintaining structural integrity is key to improving chemical stability. Gd, Eu Electronegative (~1.2) It acts as a charge balance hub, uniformly dispersing the charge in the system and preventing cation segregation and ordering caused by local charge mismatch. A position (Y / Nd / Sm) low electronegativity <![CDATA[Synergistically enhance the ionic property of the Ce-O bond with Pr to inhibit the reduction of Ce 4+ Meanwhile, the thermal expansion coefficient and oxygen vacancy concentration can be finely tuned according to specific performance requirements.]]>

[0035] Irreplaceable core: Pr is the only rare earth element that combines low electronegativity with variable valence state, and Yb is one of the heavy rare earth elements with the highest electronegativity. Neither of them can be easily replaced by other elements in terms of electrochemical stability.

[0036] IV. The Irreplaceability of Matching Dimensions Based on the Coefficient of Thermal Expansion

[0037] Pr / Nd / Sm High contribution <![CDATA[Provide a source of high coefficient of thermal expansion to ensure that the overall coefficient of thermal expansion reaches 12.5×10 -6 / K or more, matching the superalloy substrate.]]> Yb low contribution When mixed in equal molar amounts, it has a "lowering" effect, precisely controlling the coefficient of thermal expansion and avoiding excessively high coefficients that could lead to thermal stress mismatch. Eu / Gd Buffer adjustment This ensures a smooth transition in the coefficient of thermal expansion between "large" and "small", avoiding localized differences in thermal expansion caused by uneven composition.

[0038] The irreplaceable core: It is difficult to achieve precise control of the coefficient of thermal expansion by simply mixing large and small-sized ions. The buffering effect of medium-sized ions is the key to achieving a "high and controllable" coefficient of thermal expansion.

[0039] Example 1

[0040] A high-entropy cerate ceramic, comprising Ce₂O₃, Eu₂O₃, Yb₂O₃, Gd₂O₃, and Pr₆O₃. 11 Sm₂O₃ powder was calcined at 1000℃ for 2 hours to remove adsorbed carbon dioxide, moisture, and other impurities. Ce₂O₃, Eu₂O₃, Yb₂O₃, Gd₂O₃, and Pr₆O₃ were weighed according to a molar ratio of 0.4:0.4:0.4:0.4:0.4:2. 11Sm2O3 powder was used to obtain powder raw materials.

[0041] Anhydrous ethanol and milling beads were added to the above powder raw material. The mass ratio of powder raw material, anhydrous ethanol and milling beads was 3:4:2. The milling beads were zirconium oxide. The rotation speed was 300 rpm / min and the milling time was 4 hours. The milled slurry was placed in a drying oven and dried at 100 °C for 10 hours. The dried powder was sintered at 1400 °C for 2 hours. Then, the same parameters were set and a second milling was performed. After the milling was completed, the powder was dried and passed through a 100-mesh sieve to obtain the powder.

[0042] Ceramic bulk samples were prepared using a rapid hot pressing sintering process. The temperature was raised to 1500 °C within 10 min, and sintering was completed under a pressure of 50 MPa for 30 min to obtain the ceramic bulk sample.

[0043] The thermal conductivity and coefficient of thermal expansion of the high-entropy ceramic were tested. The thermal conductivity of the high-entropy ceramic was as follows: Figure 1 As shown in the figure, the thermal conductivity test results indicate that the material of this invention has a much lower thermal conductivity than YSZ at high temperatures, demonstrating outstanding thermal insulation performance. It also possesses a high coefficient of thermal expansion (12.79 × 10⁻⁶). -6 / K) (e.g.) Figure 2 As shown in the figure, it is closely matched with the high-temperature alloy substrate.

[0044] The XRD pattern after annealing at 1600℃ for 100 hours is as follows: Figure 3 As shown, from Figure 3 It can be seen that the high-entropy cerate ceramic prepared in this embodiment did not change its phase after annealing at 1600℃ for 100 hours (maintaining a single-phase defect fluorite structure). This is because the five rare earth cations are highly disordered in the crystal lattice, resulting in high configurational entropy, which thermodynamically stabilizes the single cubic phase. At the same time, the difference in ionic radii causes significant lattice distortion, which greatly increases the energy barrier for atomic rearrangement required for phase transition. In addition, the ion diffusion rate is severely hindered at high temperatures, making it difficult for phase transition to occur kinetically. Furthermore, the Ce-O framework itself has high bond strength and stable structure, so it can still maintain its original crystal structure without phase transition at 1600℃.

[0045] Example 2

[0046] Unlike Example 1, a high-entropy cerate ceramic was prepared by the following method:

[0047] Take Ce₂O₃, Eu₂O₃, Yb₂O₃, Gd₂O₃, and Pr₆O₃ respectively. 11 Nd2O3 powder was calcined at 1000℃ for 2 hours to remove impurities such as carbon dioxide and moisture adsorbed in the powder.

[0048] Weigh out Ce₂O₃, Eu₂O₃, Yb₂O₃, Gd₂O₃, and Pr₆O₃ according to a molar ratio of 0.4:0.4:0.4:0.4:0.4:2. 11 Nd2O3 powder was used to obtain powdered raw materials.

[0049] Anhydrous ethanol and milling beads were added to the above powder raw material. The mass ratio of powder raw material, anhydrous ethanol and milling beads was 3:4:2. The milling beads were zirconium oxide. The rotation speed was 300 rpm / min and the milling time was 4 hours. The milled slurry was placed in a drying oven and dried at 100 °C for 10 hours. The dried powder was sintered at 1400 °C for 2 hours. Then, the same parameters were set and a second milling was performed. After the milling was completed, the powder was dried and passed through a 100-mesh sieve to obtain the powder.

[0050] Ceramic bulk samples were prepared using a rapid hot pressing sintering process. The temperature was raised to 1500 °C within 10 min, and sintering was completed under a pressure of 50 MPa for 30 min to obtain the ceramic bulk sample.

[0051] The thermal conductivity and coefficient of thermal expansion of the high-entropy ceramic were tested. The thermal conductivity of the high-entropy ceramic was as follows: Figure 1 As shown in the figure, the thermal conductivity test results indicate that the material of this invention has a much lower thermal conductivity than YSZ at high temperatures, demonstrating outstanding thermal insulation performance. It also possesses a high coefficient of thermal expansion (12.83 × 10⁻⁶). -6 / K) (e.g.) Figure 2 As shown, it is closely matched with the high-temperature alloy substrate. The high-entropy cerate ceramic prepared in this embodiment showed no phase change after annealing at 1600℃ for 100 hours (maintaining the single-phase defect fluorite structure).

[0052] Example 3

[0053] Unlike Example 1, a high-entropy cerate ceramic was prepared by the following method:

[0054] Take Ce₂O₃, Eu₂O₃, Yb₂O₃, Gd₂O₃, and Pr₆O₃ respectively. 11, Y2O3 powder was calcined at 1000℃ for 2 hours to remove impurities such as carbon dioxide and moisture adsorbed in the powder.

[0055] Weigh out Ce₂O₃, Eu₂O₃, Yb₂O₃, Gd₂O₃, and Pr₆O₃ according to a molar ratio of 0.4:0.4:0.4:0.4:0.4:2. 11, Y2O3 powder was used to obtain powder raw materials.

[0056] Anhydrous ethanol and milling beads were added to the above powder raw material. The mass ratio of powder raw material, anhydrous ethanol and milling beads was 3:4:2. The milling beads were zirconium oxide. The rotation speed was 300 rpm / min and the milling time was 4 hours. The milled slurry was placed in a drying oven and dried at 100 °C for 10 hours. The dried powder was sintered at 1400 °C for 2 hours. Then, the same parameters were set and a second milling was performed. After the milling was completed, the powder was dried and passed through a 100-mesh sieve to obtain the powder.

[0057] Ceramic bulk samples were prepared using a rapid hot pressing sintering process. The temperature was raised to 1500 °C within 10 min, and sintering was completed under a pressure of 50 MPa for 30 min to obtain the ceramic bulk sample.

[0058] The thermal conductivity and coefficient of thermal expansion of the high-entropy ceramic were tested. The thermal conductivity of the high-entropy ceramic was as follows: Figure 1 As shown in the figure, the thermal conductivity test results indicate that the material of this invention has a much lower thermal conductivity than YSZ at high temperatures, demonstrating outstanding thermal insulation performance. It also possesses a high coefficient of thermal expansion (12.55 × 10⁻⁶). -6 / K) (e.g.) Figure 2 As shown in the figure, it is closely matched with the high-temperature alloy substrate. The high-entropy cerate ceramic prepared in this embodiment also showed no phase change after annealing at 1600℃ for 100 hours (maintaining the single-phase defect fluorite structure).

[0059] Comparative Example 1

[0060] Unlike Example 1, a rapid hot-pressing sintering process was used to prepare the ceramic bulk sample. The temperature was raised to 1500 °C within 10 min, and sintering was completed under a pressure of 20 MPa for 30 min to obtain the ceramic bulk. The thermal conductivity and coefficient of thermal expansion of the obtained high-entropy cerate ceramic were tested, and the results are shown in Table 1. As can be seen from Table 1, the thermal conductivity of Comparative Example 1 decreased significantly, but the coefficient of thermal expansion also decreased. This is because the reduced pressure resulted in insufficient particle rearrangement, plastic flow, and mass migration, leading to a decrease in the density of the sintered body and an increase in internal porosity. Pores are phonon scattering centers, significantly increasing the phonon scattering probability and shortening the phonon mean free path. The thermal conductivity of the porous phase is much lower than that of the solid phase of the ceramic matrix. The higher the porosity, the lower the equivalent thermal conductivity. The ceramic matrix itself has inherent thermal expansion characteristics, but the internal pores "buffer" the volume expansion. During the heating process, the pores can undergo elastic deformation or even partially close, offsetting part of the expansion trend of the matrix. The lower the density, the larger the volume fraction of pores, and the smaller the macroscopically measured average linear expansion coefficient.

[0061] Comparative Example 2

[0062] Unlike Example 2, a rapid hot-pressing sintering process was used to prepare the ceramic bulk sample. The temperature was raised to 1300 °C within 10 min, and sintering was completed under a pressure of 50 MPa for 30 min to obtain the ceramic bulk. Its thermal conductivity and coefficient of thermal expansion are shown in Table 1. As can be seen from Table 1, the thermal conductivity and coefficient of thermal expansion of the material also decrease accordingly. This is similar to Comparative Example 1. The lower sintering temperature will cause the ceramic density to decrease, the porosity to increase, and the grains to become finer, thereby significantly reducing the thermal conductivity and slightly decreasing the coefficient of thermal expansion. The mechanism is that the material migration rate is slowed down at low temperatures, making it difficult for the particles to be fully densified. The increased porosity enhances phonon scattering and buffers thermal expansion. At the same time, the fine grains will further scatter phonons and reduce the thermal conductivity.

[0063] Comparative Example 3

[0064] Unlike Example 1, Pr was replaced with La, while everything else remained the same. The thermal conductivity and coefficient of thermal expansion of the ceramic prepared in this comparative example were tested, and the thermal conductivity at 1200℃ was found to be 1.43 W·m. -1 ·K -1 The coefficient of thermal expansion is 11.89 10. -6 / K. This is because replacing Pr with La results in a more uniform ion radius distribution, reduced lattice distortion, decreased phonon scattering efficiency, and increased thermal conductivity. Furthermore, the higher La-O bond energy and increased lattice rigidity weaken the lattice's thermal expansion capability, leading to a decrease in the coefficient of thermal expansion. Through the aforementioned comparative restraints, Pr in this application serves as a source of high thermal expansion, ensuring an overall coefficient of thermal expansion of 12.5 × 10⁻⁶. -6 / K and above are key elements that match the high-temperature alloy substrate and are irreplaceable.

[0065] Comparative Example 4

[0066] Unlike Example 1, Yb was replaced with Tm, while everything else remained the same. The thermal conductivity and coefficient of thermal expansion of the ceramic prepared in this comparative example were tested, and the thermal conductivity at 1200℃ was found to be 1.21 W·m. -1 ·K -1 The coefficient of thermal expansion is 11.26 × 10⁻⁶. -6 / K. This is because replacing Yb with Tm results in a larger mass difference, stronger lattice distortion, and enhanced phonon scattering, leading to a slight decrease in thermal conductivity; however, Tm 3+ Ionic radius < Yb 3+ The crystal lattice is more compact, and the difference in ionic radii is greater, resulting in stronger lattice distortion and tighter atomic bonding. At high temperatures, the lattice is less prone to expansion, leading to a significant decrease in the coefficient of thermal expansion.

[0067] Comparative Example 5

[0068] Unlike Example 1, Eu was omitted to form a quaternary system; all other aspects remained the same as in Example 1. The thermal conductivity and coefficient of thermal expansion of the ceramic prepared in this comparative example were tested, and the thermal conductivity at 1200℃ was found to be 1.67 W·m. -1 ·K -1 The coefficient of thermal expansion is 11.12 × 10⁻⁶. -6 / K. This is because removing Eu to form a quaternary system reduces the compositional entropy, weakens lattice disorder and distortion, reduces phonon scattering, and facilitates smoother phonon propagation, thus significantly increasing thermal conductivity; removing the larger radius Eu... 3+ Subsequently, the average ionic radius of the system decreases, the lattice becomes denser, the ion size distribution becomes more uniform, and the lattice rigidity is enhanced. At high temperatures, the thermal expansion of the lattice is effectively suppressed, thus reducing the coefficient of thermal expansion.

[0069] Table 1

[0070] Example 1 1.27 12.79 Example 2 1.46 12.83 Example 3 1.32 12.55 Comparative Example 1 1.13 12.07 Comparative Example 2 1.09 12.32 Comparative Example 3 1.43 11.89 Comparative Example 4 1.21 11.26 Comparative Example 5 1.67 11.12

[0071] As can be seen from Table 1, (A) prepared according to the method of the present invention 0.2 Pr 0.2 Eu 0.2 Gd 0.2 Yb 0.2 2Ce₂O₇; also possesses low thermal conductivity (less than 1.40 W·m⁻¹). -1 ·K -1 (1200℃) and a high coefficient of thermal expansion (greater than 12.50 10) -6 / K).

[0072] This invention achieves synergistic optimization in three dimensions—ionic radius, electronegativity, and oxygen vacancies—through a five-element rare-earth high-entropy strategy. It successfully overcomes the technical bottleneck of traditional cerate materials, which struggle to balance thermal conductivity and thermal expansion coefficient. This provides a novel candidate material for next-generation ultra-high temperature thermal barrier coatings that combines efficient thermal insulation, structural stability, and excellent thermal matching.

[0073] The technical solutions in the embodiments of the present invention have been clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A high-entropy cerate ceramic for thermal barrier coating, characterized in that: The chemical composition of the high-entropy cerate ceramic is represented by the following general formula: (A 0.2 Pr 0.2 Eu 0.2 Gd 0.2 Yb 0.2 )2Ce2O7; wherein A is selected from one of Y, Nd, and Sm, and the ceramic is a single-phase defect fluorite structure with a thermal conductivity of less than 1.40 W·m at 1200℃. -1 ·K -1 The coefficient of thermal expansion is higher than 12.5 × 10⁻⁶. -6 / K, and the phase structure remains unchanged after heat treatment in air at 1600℃ for 100 hours.

2. A method for preparing high-entropy cerate ceramic for thermal barrier coating as described in claim 1, characterized in that: Includes the following steps: S1. Raw material pretreatment: Pretreatment of raw materials containing Ce2O3, Eu2O3, Yb2O3, Gd2O3, and Pr6O 11 All raw material powders, including oxides of element A, are pre-calcined. S2. Ingredients and mixing: Weigh each raw material powder after step S1 according to the stoichiometric ratio of the general formula described in claim 1, and mix it together with the ball milling media and dispersant by ball milling to obtain a uniform slurry; S3. Drying and pre-firing: The slurry is dried to obtain a mixed powder, which is then pre-sintered at 1300℃ to 1400℃ to obtain high-entropy ceramic initial powder; S4. Secondary processing: The high-entropy ceramic powder is subjected to secondary ball milling, drying, and sieving to obtain high-entropy ceramic powder; S5. Rapid hot pressing sintering: The high-entropy ceramic powder is heated to 1450-1550℃ within 10 minutes and held at 30-50 MPa pressure for 10-30 minutes to obtain high-entropy cerate ceramic bulk material.

3. The preparation method according to claim 2, characterized in that: In step S2, the ball milling speed is 200 rpm to 300 rpm, and the ball milling time is 2 hours to 4 hours.

4. The preparation method according to claim 2, characterized in that: In step S3, the heat preservation time for pre-sintering is 1 hour to 3 hours.

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