Chemical components and synthesis method of B-site entropy stable pyrochlore structure thermal barrier ceramic material

Abstract

The invention provides chemical components and a synthesis method of a thermal barrier ceramic material with a B-site entropy stable pyrochlore structure. The chemical structural formula is Gd2 (Ti1 / 3Zr1 / 3Sn1 / 3) 2O7. The preparation method comprises the following steps: weighing four kinds of powder Gd2O3, TiO2, ZrO2 and SnO2 according to a molar ratio, carrying out ball-milling mixing, drying the mixture, and grinding to obtain fine powder; the preparation method comprises the following steps: preparing a to-be-sintered green body by adopting a cold isostatic pressing method, presintering at 1200-1300 DEG C and sintering at 1500-1600 DEG C by adopting a solid-phase reaction method, and finally cooling along with a furnace to realize synthesis of a ceramic block. The process flow is simple, the operation is convenient, and the finished product shows amorphous-like extremely low thermal conductivity (0.92-0.85 W.m <-1 >. K <-1 > (25-1100 DEG C)), excellent high-temperature phase stability and sintering resistance and excellent mechanical properties, and is suitable for a high-temperature thermal barrier environment.

Description

Technical Field

[0001] The present invention relates to a chemical composition and a synthesis method of a thermal barrier ceramic material A2B2O7 for an aeroengine, specifically to a chemical composition and a synthesis method of a B-site entropy-stabilized pyrochlore structure thermal barrier ceramic with an extremely low thermal conductivity of a quasi-amorphous material, and its chemical structural formula is Gd2(Ti 1 / 3 Zr 1 / 3 Sn 1 / 3 )2O7. The synthesized B-site entropy-stabilized pyrochlore structure ceramic material is used to prepare a new generation of thermal barrier coating materials with extremely low thermal conductivity, excellent thermal stability and good comprehensive mechanical properties. Background Art

[0002] Thermal barrier coatings (TBCs) are crucial for protecting high-temperature components in advanced aeroengines from harsh service environments. Generally, TBCs are required to have excellent thermophysical properties, mechanical properties, high-temperature phase stability properties, and good chemical compatibility properties with the thermally grown oxide layer (TGO). With the increasing demand for higher gas temperatures in aeroengines, traditional Y2O3-stabilized ZrO2 (YSZ) has disadvantages such as a fast sintering rate and poor phase stability at high temperatures, making it difficult to meet the long-term service requirements of future thermal barrier coatings. Therefore, the development of new ultra-high temperature, high heat insulation, and long-life thermal barrier coating materials has become a research hotspot in the international high-temperature protective coating field. In recent years, A2B2O7 pyrochlore-like structure ceramic materials have received extensive attention due to their high melting points, low thermal conductivities, and good phase stabilities (Z.L. Xue, H.B. Guo, S.K. Gong, H.B. Xu, Novel ceramic materials for thermal barrier coatings, J. Aeronaut. Mater., 38 (2018) 10-20.). Among them, although Gd2Ti2O7 and Gd2Zr2O7 as representative materials have excellent thermophysical properties, their fracture toughness is low, which limits further applications. In the pyrochlore crystal structure, each A2B2O7 molecular unit contains an oxygen vacancy, and the high concentration of oxygen vacancies makes phonon scattering very strong, which is beneficial to enhancing the heat insulation performance of the material. In addition, a large number of intrinsic oxygen vacancies enable A2B2O7-type oxides to accommodate the coexistence of multiple types of components. Therefore, A2B2O7 pyrochlore-like structure ceramic materials are important candidates for entropy-stabilized thermal barrier ceramic materials.

[0003] Entropy-stable ceramic materials have gradually been used in the design of thermal barrier ceramic materials in recent years due to their high configurational entropy, severe lattice distortion, sluggish diffusion, etc. Most studies have only focused on designing A2B2O7-type entropy-stable materials by selecting different A-site rare earth elements. However, for entropy stabilization, at least one pair of single-cation compounds should not have extensive solubility. Since rare earth elements have good solubility, this criterion is usually not met when introducing disorder at the A-site by mixing several rare earth cations. In addition, since the ionic radii of Re 3+ are similar, the mass difference is also small, and they all carry a trivalent positive charge, the resulting lattice distortion is not severe. However, the low thermal conductivity is mainly attributed to two factors: (1) A large number of oxygen vacancies act as phonon scattering points, increasing the intensity of phonon collisions and reducing the phonon propagation mean free path; (2) Additional phonon scattering caused by compositional disorder (including size disorder and mass disorder). Pyrochlore-structured materials often have low thermal conductivity due to a large number of intrinsic oxygen vacancies. The severe lattice distortion brought about by the compositional disorder of entropy-stable ceramic materials generates a large number of point defects, which combine with intrinsic oxygen vacancies to form stronger phonon scattering, further reducing the phonon propagation average free path and achieving the purpose of reducing thermal conductivity.

[0004] Patent CN 113023776 A reports a fluorite-structured high-entropy oxide powder for thermal barrier coatings. The ceramic powder has a fluorite structure, not a pyrochlore structure, and its chemical formula is RE2HE2O7, where RE is any one of the rare earth elements Y, Ho, Er, Yb, and Lu, and HE is at least three metal elements among Ce, Zr, Hf, Sn, and Ti. The relatively low thermal conductivity (0.98 - 1.5 W·m -1 ·K -1 ) makes it promising to be a potential thermal barrier coating material. However, other studies have shown that the target thermal conductivity of thermal barrier coating materials is below 1 W·m -1 ·K -1 . Only the composition Lu2(Ce 0.2 Zr 0.2 Hf 0.2 Sn 0.2 Ti 0.2 )2O7 (0.98 W·m -1 ·K -1 ) in Patent CN 113023776 A meets this requirement. Therefore, the thermal conductivity of this fluorite-structured high-entropy oxide powder still needs to be reduced. In addition, the low fracture toughness has always been a resistance restricting the practical application of thermal barrier coating materials. The highest fracture toughness of the materials reported in Patent CN 113023776A is 1.87 MPa·m 1 / 2 . The low fracture toughness limits its application. In summary, there is an urgent need to invent thermal barrier ceramic materials with low thermal conductivity and high fracture toughness. Summary of the Invention

[0005] In view of the deficiencies of the prior art, Ti selected in the present invention 4+ , Zr 4+ and Sn 4+ are used to design an entropy-stabilized pyrochlore-structured thermal barrier ceramic material, and its chemical structural formula is Gd2(Ti 1 / 3 Zr 1 / 3 Sn 1 / 3 )2O7. The relevant thermophysical and mechanical properties are successfully synthesized and tested by the solid-state reaction method. The results show that Gd2(Ti 1 / 3 Zr 1 / 3 Sn 1 / 3 )2O7 has excellent comprehensive properties and great potential as a next-generation TBCs material.

[0006] The present invention provides a chemical composition of an entropy-stabilized pyrochlore-structured thermal barrier ceramic material Gd2(Ti 1 / 3 Zr 1 / 3 Sn 1 / 3 )2O7 and successfully completes the preparation by the solid-state reaction method. The prepared ceramic exhibits extremely low thermal conductivity (0.92 - 0.85 W·m -1 ·K -1 (25 - 1100 °C)) similar to that of amorphous materials, excellent high-temperature phase stability and anti-sintering performance, and excellent comprehensive mechanical properties, and is suitable for high-temperature thermal barrier environments.

[0007] The technical solution of the present invention is as follows:

[0008] The chemical composition of an entropy-stabilized pyrochlore-structured thermal barrier ceramic material, and its chemical structural formula is Gd2(Ti 1 / 3Zr 1 / 3 Sn 1 / 3 )2O7.

[0009] The synthesis method of an entropy-stabilized pyrochlore-structured thermal barrier ceramic material of the present invention selects Ti 4+ , Zr 4+ and Sn 4+ , and synthesizes Gd2(Ti 1 / 3 Zr 1 / 3 Sn 1 / 3 )2O7 by the solid-state reaction method.

[0010] The synthesis method of the B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic material described above involves weighing and mixing four powders, namely Gd2O3, TiO2, ZrO2, and SnO2 powders, in a molar ratio of 3:2:2:2, and then adding anhydrous ethanol and ZrO2 milling beads for ball milling; drying and grinding the ball-milled slurry through a 200-mesh sieve to obtain a uniformly mixed fine powder; taking the powder for cold isostatic pressing to form a green body to be sintered, and sintering the green body using the solid-state reaction method.

[0011] The purity of the four powders, Gd2O3, TiO2, ZrO2, and SnO2 powders, is greater than 99%.

[0012] The ball milling speed is 300 - 500 rpm, and the ball milling time is 10 - 15 h.

[0013] The drying temperature of the slurry is 80 - 150 °C, and the drying time is 4 - 6 h.

[0014] The single mass of the sintered green body is 0.5 - 1.0 g.

[0015] The sintering process of the solid-state reaction method is as follows: First, pre-sinter at 1200 °C - 1300 °C for 10 - 30 h to fully ensure the solid-state reaction of the four powders during the subsequent sintering process; then sinter at 1500 °C - 1600 °C for 20 - 40 h to densify and synthesize the pre-sintered ceramic block at high temperature; finally, cool with the furnace to obtain a fine-grained microstructure for the ceramic.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The present invention selects Ti 4+ , Zr 4+ and Sn 4+ to achieve the synthesis of an entropy-stabilized single pyrochlore-phase thermal barrier ceramic material. Due to the large number of intrinsic oxygen vacancies in the pyrochlore-structured material, and the severe lattice distortion caused by B-site entropy stabilization, a large number of point defects are generated, forming a very strong scattering of phonons and point defects, greatly shortening the average free path of phonon propagation, so that the synthesized entropy-stabilized pyrochlore-structured material has an extremely low thermal conductivity of 0.92 - 0.85 W·m -1 ·K -1 (25 - 1100 °C), which is much lower than the thermal conductivity of the existing common YSZ material, 2.12 W·m -1 ·K -1 (1000 °C).

[0018] (2) A kind of entropy-stabilized pyrochlore-structured material synthesized by the present invention has extremely fine grain size (about 0.95 μm) due to the sluggish diffusion effect and severe lattice distortion effect brought about by the entropy stabilization at the B-site. The fine grain strengthening effect makes the synthesized entropy-stabilized component material have high hardness (10.9 GPa), excellent fracture toughness (2.63 MPa·m 1 / 2 ) and low Young's modulus (192 GPa). Its excellent comprehensive mechanical properties far exceed those of some single-component and high-entropy thermal barrier ceramic materials.

[0019] (3) The present invention adopts a stepped solid-state reaction method. In the first step, pre-sintering is carried out to fully ensure that the four powders undergo solid-state reactions during the subsequent sintering process. In the second step, the pre-sintered ceramic block is densified and synthesized at high temperature, and finally it is cooled in the furnace to make the ceramic obtain a fine-grained microstructure. The process is simple and easy to operate. Description of the Drawings

[0020] Figure 1 It is the XRD pattern of a B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic material Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7.

[0021] Figure 2 It is a schematic diagram of the microstructure of the sintered ceramic block. The grain boundaries are clear and obvious, the porosity is low, the grain size is fine (about 0.95 μm), and the distribution of each element is uniform.

[0022] Figure 3 It is the high-resolution TEM and selected area electron diffraction (SAED) images of the sintered ceramic block, further verifying that the Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 ceramic has a single pyrochlore structure and the element distribution is uniform at the nanoscale.

[0023] Figure 4 It is the XRD pattern of the sintered ceramic block after being treated at different temperatures for different times, indicating that the Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 ceramic has excellent high-temperature phase stability.

[0024] Figure 5 It is a comparison chart of the thermal conductivity performance between the Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 ceramic and other single-component ceramics, indicating that the Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 ceramic has the shortest phonon mean free path and the lowest thermal conductivity.

[0025] Figure 6 It is a comparison chart of the thermal expansion performance between the Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 ceramic and other single-component ceramics, indicating that the Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 ceramic has a thermal expansion coefficient matching that of the thermally grown oxide layer.

[0026] Figure 7 Schematic diagram of the mechanical properties of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 ceramics, indicating that Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 ceramics have excellent comprehensive mechanical properties.

[0027] Figure 8 XRD patterns of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 / Al2O3 mixed powder after heat treatment at different temperatures for 10 h, indicating that Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 ceramics have excellent chemical compatibility with the thermally grown oxide layer.

[0028] Figure 9 Schematic diagram of the synthesis process of a B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic material Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7. Detailed implementation mode

[0029] Example 1:

[0030] (1) According to the molar ratio in the molecular formula, 30.45 g, 4.41 g, 6.90 g and 8.44 g of dried Gd2O3, TiO2, ZrO2 and SnO2 powders were taken respectively;

[0031] (2) 40 ml of anhydrous ethanol and 50 g of ZrO2 milling beads were taken and put into the milling jar together with the weighed powders, and ball milling was carried out at a rotation speed of 300 rpm for 10 h;

[0032] (3) The obtained slurry was dried at 80 °C for 4 h, then ground and passed through a 200-mesh sieve to obtain a uniformly mixed fine powder;

[0033] (4) 0.5 g of the fine powder was taken for cold isostatic pressing to form a green body block to be sintered;

[0034] (5) Using a high-temperature muffle furnace, pre-sintering was first carried out at 1200 °C for 10 h; then it was kept at 1500 °C for 20 h to densify and synthesize the pre-sintered ceramic block at high temperature; finally, it was cooled with the furnace. The phase structure of the sintered block is as Figure 1 shown. It can be seen that except for the characteristic peaks of (222), (400), (440) and (622) of the pyrochlore structure, no characteristic peaks of other second phases or impurities were observed, indicating that the sintered Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 block has a single-phase pyrochlore structure with a space group of Fd3m. Thus, a B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 was successfully sintered and synthesized.

[0035] Example 2:

[0036] (1) According to the molar ratios in the molecular formula, 30.45 g, 4.41 g, 6.90 g, and 8.44 g of dried Gd2O3, TiO2, ZrO2, and SnO2 powders were taken respectively;

[0037] (2) 40 ml of anhydrous ethanol and 50 g of ZrO2 ball milling beads were taken and put into the ball milling tank together with the weighed powders, and ball milling was carried out at a rotation speed of 400 rpm for 12 h;

[0038] (3) The obtained slurry was dried at 120 °C for 5 h, then ground and passed through a 200-mesh sieve to obtain a uniformly mixed fine powder;

[0039] (4) 0.7 g of the fine powder was taken for cold isostatic pressing to form a green body block to be sintered;

[0040] (5) Using a high-temperature muffle furnace, pre-sintering was first carried out at 1250 °C for 10 h; then it was kept at 1500 °C for 30 h to make the pre-sintered ceramic block achieve densification and synthesis at high temperature; finally, it was cooled with the furnace. The schematic diagram of the microscopic morphology of the sintered block is as Figure 2 shown. It can be seen that the grain boundaries between the ceramic block grains are clear and obvious, the block porosity is low, the grain size is small (about 0.95 μm), and the distribution of each element is uniform. Thus, the B-site entropy-stabilized pyrochlore structure thermal barrier ceramic Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 with clear grain boundaries, low porosity, small grain size, and uniform distribution of each element was successfully sintered and synthesized.

[0041] Example 3:

[0042] (1) According to the molar ratios in the molecular formula, 30.45 g, 4.41 g, 6.90 g, and 8.44 g of dried Gd2O3, TiO2, ZrO2, and SnO2 powders were taken respectively;

[0043] (2) 40 ml of anhydrous ethanol and 50 g of ZrO2 ball milling beads were taken and put into the ball milling tank together with the weighed powders, and ball milling was carried out at a rotation speed of 400 rpm for 15 h;

[0044] (3) The obtained slurry was dried at 120 °C for 6 h, then ground and passed through a 200-mesh sieve to obtain a uniformly mixed fine powder;

[0045] (4) 0.8 g of the fine powder was taken for cold isostatic pressing to form a green body block to be sintered;

[0046] (5) Use a high-temperature muffle furnace to first perform pre-sintering at 1250 °C for 20 h; then hold at 1550 °C for 30 h to densify and synthesize the pre-sintered ceramic block at high temperature; finally, cool it down with the furnace. The high-resolution TEM and selected area electron diffraction (SAED) images of the sintered block are as Figure 3 shown, Figure 3 (a) The diffraction pattern along the [0 - 11] zone axis confirms that the ceramic block is a single-phase pyrochlore structure, Figure 3 (b) It can be seen that the ceramic block has a uniform elemental distribution at the nanoscale. Thus, a B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 with a uniform elemental distribution at the nanoscale is successfully sintered and synthesized.

[0047] Example 4:

[0048] (1) According to the molar ratios in the molecular formula, take 30.45 g, 4.41 g, 6.90 g, and 8.44 g of dried Gd2O3, TiO2, ZrO2, and SnO2 powders respectively;

[0049] (2) Take 40 ml of anhydrous ethanol and 50 g of ZrO2 milling beads and put them together with the weighed powders into a ball milling jar, and perform ball milling at a rotation speed of 500 rpm for 10 h;

[0050] (3) Dry the obtained slurry at 150 °C for 4 h, then grind it and pass it through a 200-mesh sieve to make a uniformly mixed fine powder;

[0051] (4) Take 0.8 g of the fine powder for cold isostatic pressing to make a green block for sintering;

[0052] (5) Use a high-temperature muffle furnace to first perform pre-sintering at 1250 °C for 30 h; then hold at 1550 °C for 40 h to densify and synthesize the pre-sintered ceramic block at high temperature; finally, cool it down with the furnace. The XRD patterns of the sintered block after being treated at different temperatures for different times are as Figure 4 shown, Figure 4 (a) The XRD patterns of the ceramic block after being heat-treated at 1500 °C for 10 h, 30 h, 60 h, and 100 h respectively show that, except for the characteristic peaks of the pyrochlore structure, no characteristic peaks of other second phases or impurities appear; Figure 4 (b) The XRD patterns of the ceramic block after being heat-treated at 1600 °C for 10 h, 30 h, 60 h, and 100 h respectively can be seen that, except for the characteristic peaks of the pyrochlore structure, no characteristic peaks of other second phases or impurities appear either. Thus, a B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 with excellent high-temperature phase stability is successfully sintered and synthesized.

[0053] Example 5:

[0054] (1) According to the molar ratios in the molecular formula, take 30.45 g, 4.41 g, 6.90 g, and 8.44 g of dried Gd2O3, TiO2, ZrO2, and SnO2 powders respectively;

[0055] (2) Take 40 ml of anhydrous ethanol and 50 g of ZrO2 ball milling beads, and put them together with the weighed powders into a ball milling tank, and carry out ball milling at a rotation speed of 500 rpm for 12 h;

[0056] (3) Dry the obtained slurry at 150 °C for 5 h, then grind it and pass through a 200-mesh sieve, and a uniformly mixed fine powder is made;

[0057] (4) Take 1.0 g of the fine powder for cold isostatic pressing to form a green compact block to be sintered;

[0058] (5) Use a high-temperature muffle furnace to first carry out pre-sintering at 1300 °C for 10 h; then keep it at 1600 °C for 20 h to densify and synthesize the pre-sintered ceramic block at high temperature; finally, cool it with the furnace. The comparison chart of the thermal conductivity performance of the sintered block and other single-component ceramics is as Figure 5 shown, Figure 5 (a) shows the change trend of the thermal diffusion rate of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 and single-component ceramics with the increase of temperature. It can be seen that the thermal diffusion rates of all component ceramic materials decrease with the increase of temperature. Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 has the lowest thermal diffusion rate compared with the single-component ceramics Gd2Ti2O7 (0.80 - 0.48 mm 2 / s, 25 - 900 °C) and Gd2Zr2O7 (0.81 - 0.46 mm 2 / s, 25 - 1100 °C), which is 0.58 - 0.39 mm 2 / s (25 - 1100 °C). Figure 5 (b) shows the change trend of the molar specific heat capacity of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 and single-component ceramics with the increase of temperature. It can be seen that the molar specific heat capacities of all component ceramic materials increase with the increase of temperature. Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 shows a medium-sized molar specific heat capacity compared with single-component ceramics. Figure 5 (c) shows the change trend of the thermal conductivity of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 and single-component ceramics with the increase of temperature. It can be seen that the thermal conductivity shows a downward trend with the increase of temperature. Among them, the thermal conductivity of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 is 0.92 - 0.85 W·m -1 ·K-1 (25 - 1100 °C), much lower than that of single-component ceramics Gd2Ti2O7 (2.25 - 1.75 W·m -1 ·K -1 , 25 - 900 °C), Gd2Zr2O7 (1.47 - 1.06 W·m -1 ·K -1 , 25 - 1100 °C) and Gd2Sn2O7 (4.34 - 2.18 W·m -1 ·K -1 , 200 - 1100 °C). And with the continuous increase of temperature, the thermal conductivity of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 shows the characteristic of being stable at high temperature similar to that of amorphous materials. Figure 5 (d) shows the variation trend of the average phonon mean free path of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 and single-component ceramics with the increase of temperature. It can be seen that the average phonon mean free path shows a downward trend with the increase of temperature, and Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 has the lowest average phonon mean free path. Thus, a B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 with extremely low thermal conductivity is successfully sintered and synthesized.

[0059] Example 6:

[0060] (1) According to the molar ratio in the molecular formula, take 60.90 g, 8.82 g, 13.80 g and 16.88 g of dried Gd2O3, TiO2, ZrO2 and SnO2 powders respectively;

[0061] (2) Take 80 ml of absolute ethanol and 100 g of ZrO2 milling beads and put them together with the weighed powders into a ball milling jar, and carry out ball milling at a rotation speed of 500 rpm for 15 h;

[0062] (3) Dry the obtained slurry at 150 °C for 6 h, then grind it and pass through a 200-mesh sieve to obtain a uniformly mixed fine powder;

[0063] (4) Take 1.0 g of the fine powder for cold pressing to form a green compact to be sintered;

[0064] (5) Use a high-temperature muffle furnace to first carry out pre-sintering at 1300 °C for 20 h; then keep it at 1600 °C for 30 h to make the pre-sintered ceramic block achieve densification and synthesis at high temperature; finally, cool it with the furnace. The comparison diagram of the thermal expansion performance of the sintered block and other single-component ceramics is as Figure 6 shown, Figure 6(a) shows the change trend of the linear expansion coefficient of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 and single-component ceramics with the increase of temperature. It can be seen that the linear expansion coefficient increases linearly with the increase of temperature, and there is no volume mutation point, indicating that no phase change occurs during the temperature rise from room temperature to 1200 °C. Figure 6 (b) shows the change trend of the thermal expansion coefficient of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 and single-component ceramics with the increase of temperature. It can be seen that the thermal expansion coefficient of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 is 10.05×10 -6 K -1 , slightly lower than that of Gd2Zr2O7 (10.7×10 -6 K -1 ), but higher than that of Gd2Ti2O7 (9.9×10 -6 K -1 ) and Gd2Sn2O7 (8.5×10 -6 K -1 ). It is worth noting that Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 has a thermal expansion coefficient close to that of the thermally grown oxide layer (9.0×10 -6 K -1 ). Thus, a B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 with a thermal expansion coefficient matching that of the thermally grown oxide layer has been successfully sintered and synthesized.

[0065] Example 7:

[0066] (1) According to the molar ratio in the molecular formula, 60.90 g, 8.82 g, 13.80 g, and 16.88 g of dried Gd2O3, TiO2, ZrO2, and SnO2 powders were taken respectively;

[0067] (2) 80 ml of absolute ethanol and 100 g of ZrO2 milling beads were taken and put into the milling jar together with the weighed powders, and ball milling was carried out at a rotation speed of 500 rpm for 15 h;

[0068] (3) The obtained slurry was dried at 150 °C for 6 h, then ground and passed through a 200-mesh sieve to obtain a uniformly mixed fine powder;

[0069] (4) 1.0 g of the fine powder was taken for cold pressing to form a green body block to be sintered;

[0070] (5) Using a high-temperature muffle furnace, pre-sintering was first carried out at 1300 °C for 30 h; then it was kept at 1600 °C for 40 h to densify and synthesize the pre-sintered ceramic block at high temperature; finally, it was cooled with the furnace. The mechanical properties of the sintered block are as Figure 7 shown.Figure 7 (a) is the microhardness indentation morphology diagram of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7. The Vickers hardness of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 is 10.9 GPa obtained by taking the average value through ten hardness tests, and its fracture toughness is calculated to be 2.63 MPa·m 1 / 2 。 Figure 7 (b) is the comparison diagram of the mechanical properties of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 and single-component ceramics. Higher hardness can resist the erosion of gas flow and particles at high temperatures and extend the service life of thermal barrier coatings. It can be seen that Gd2(Ti1 / 3Zr1 / 3Sn1 / 2)2O7 (10.9 GPa) has the highest hardness compared with Gd2Ti2O7 (9.13 GPa) and Gd2Zr2O7 (5.0 GPa). Excellent fracture toughness can often alleviate the problem of premature cracking during the service of the coating. Gd2(Ti1 / 2Zr1 / 3Sn1 / 2)2O7 (2.63 MPa·m 1 / 2 ) and Gd2Ti2O7 (1.43 MPa·m 1 / 2 ) and Gd2Zr2O7 (0.7 MPa·m 1 / 2 ) have the highest fracture toughness. In addition, a relatively low Young's modulus can improve the stress tolerance of the coating and delay the coating failure. Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 (192 GPa) has the lowest Young's modulus compared with Gd2Ti2O7 (215 GPa) and Gd2Zr2O7 (202 GPa). Thus, a B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 with excellent comprehensive mechanical properties is successfully sintered and synthesized.

[0071] Example 8:

[0072] (1) According to the molar ratios in the molecular formula, 60.90 g, 8.82 g, 13.80 g, and 16.88 g of dried Gd2O3, TiO2, ZrO2, and SnO2 powders are taken respectively;

[0073] (2) 80 ml of anhydrous ethanol and 100 g of ZrO2 milling beads are taken and put into a ball milling tank together with the weighed powders, and ball milling is carried out at a rotation speed of 500 rpm for 15 h;

[0074] (3) The obtained slurry is dried at 150 °C for 6 h, then ground and passed through a 200-mesh sieve to obtain a uniformly mixed fine powder;

[0075] (4) After synthesizing the powder by using a high-temperature muffle furnace and holding it at 1500 °C for 40 h followed by furnace cooling, mix Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 with dry Al2O3 powder at a mass ratio of 1:1; heat-treat the mixed powder at different temperatures for 10 h. The XRD patterns of the Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 / Al2O3 mixed powder after heat treatment at 1300 °C, 1400 °C, and 1500 °C for 10 h are as Figure 8 shown. It can be seen that except for the characteristic peaks of Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 and Al2O3, no characteristic peaks of other reaction products were observed. Thus, the B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 with excellent chemical compatibility with the thermally grown oxide layer was successfully sintered and synthesized. In these examples, a schematic diagram of the synthesis process of a B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic Gd2(Ti1 / 3Zr1 / 3Sn1 / 3)2O7 is as Figure 9 shown.

[0076] The present invention may also have many other embodiments. Without departing from the spirit and essence of the invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these should all fall within the protection scope of the claims of the present invention.

Claims

1. The chemical composition of a B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic material, characterized in that, The chemical structural formula is Gd2(Ti 1 / 3 Zr 1 / 3 Sn 1 / 3 )2O7.

2. The synthesis method of a B-site entropy-stabilized pyrochlore-structured thermal barrier ceramic material according to claim 1, characterized in that, Select Ti 4+ , Zr 4+ and Sn 4+ , and synthesize Gd2(Ti 1 / 3 Zr 1 / 3 Sn 1 / 3 )2O7 by the solid-state reaction method.

3. The synthesis method according to claim 2, characterized in that, Weigh and mix four kinds of powders, namely Gd2O3, TiO2, ZrO2 and SnO2 powders, according to the molar ratio of 3:2:2:2, and then add anhydrous ethanol and ZrO2 milling beads for ball milling; dry and grind the ball-milled slurry through a 200-mesh sieve to obtain a uniformly mixed fine powder; take the powder for cold isostatic pressing to form a green body to be sintered, and use the solid-state reaction method to sinter the green body.

4. The synthesis method according to claim 3, characterized in that, The purity of the four kinds of powders, Gd2O3, TiO2, ZrO2 and SnO2 powders, is greater than 99%.

5. The synthesis method according to claim 3, characterized in that, The ball milling speed is 300 - 500 rpm, and the ball milling time is 10 - 15 h.

6. The synthesis method according to claim 3, characterized in that, The drying temperature of the slurry is 80 - 150 °C, and the drying time is 4 - 6 h.

7. The synthesis method according to claim 3, characterized in that, The single mass of the sintered green body is 0.5 - 1.0 g.

8. The synthesis method according to claim 3, characterized in that, The solid-state reaction method sintering process is as follows: First, perform pre-sintering at 1200 °C - 1300 °C for 10 - 30 h to fully ensure that the four kinds of powders undergo solid-state reactions during the subsequent sintering process; then, at 1500 °C - 1600 °C for 20 - 40 h, make the pre-sintered ceramic block achieve densification and synthesis at high temperatures; finally, cool with the furnace to make the ceramic obtain a fine-grained microstructure.

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