CN110002871A - A kind of two-phase rare earth tantalate ceramics and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of thermal barrier coatings, and specifically discloses a two-phase rare earth tantalate ceramic, wherein the molar ratio of Sm:Sc:Ta in the ceramic is x:(1-x):1, wherein 0<x< 1, the ceramic is composed of SmTaO ₄ phase and ScTaO ₄ phase, and the density of the ceramic is greater than 98%; the preparation method of the ceramic is to take the molar ratio of Sm:Sc:Ta as x:(1-x):1 Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and Ta ₂ O ₅ powder, add solvent and mix, and use a ball mill for ball milling to obtain powder A; after drying powder A, sieve it for the first time to obtain powder B; After being placed in a mold and compacted, it is pre-sintered to form a block C; after the block C is cooled to room temperature, a grinder is used for grinding, and then a second sieve is performed to obtain powder D; the powder D is sintered to obtain a Two-phase rare earth tantalate ceramics. The two-phase rare earth tantalate ceramic obtained by adopting the technical solution in this patent has high density, low thermal conductivity at high temperature and high thermal expansion coefficient.

Description

A kind of two-phase rare earth tantalate ceramic and preparation method thereof

technical field

The invention relates to the technical field of thermal barrier coatings, in particular to two-phase rare earth tantalate ceramics and a preparation method thereof.

Background technique

Thermal barrier coatings are mainly used in the aero-engine industry, which mainly play the role of heat insulation, reducing the thermal mismatch between the coating and the alloy matrix, and effectively resisting particle impact to protect the parts and components in the high-temperature area of the aero-engine. It is required to have good thermodynamics. Properties such as low thermal conductivity, high thermal expansion coefficient, and high temperature stability.

At present, the widely used thermal barrier coatings mainly include yttria-stabilized zirconia (YSZ) and rare earth zirconate (RE ₂ Zr ₂ O ₇ ), etc., but they all have a certain degree of deficiencies: the use temperature of YSZ is low (≦1200℃) ), and the thermal conductivity is relatively high; while rare earth zirconate has the problem of low thermal expansion coefficient, which prompts researchers to look for thermal barrier coatings that can replace the above ceramic materials. In 2007, Professor Clarke's group at Harvard University Together with Professor Levi from the University of California, Santa Barbara, they proposed that yttrium tantalate (YTaO ₄ ) ferroelastomer is expected to be used as a new thermal barrier coating material, but the research on rare earth tantalate mainly focuses on its crystal structure and luminescent properties. In 2016, Wang et al. obtained the rare earth tantalate bulk material by the solid-phase reaction method, and came to the conclusion that the thermal conductivity is much lower than that of the YSZ material. The application in thermal barrier coatings provides a theoretical basis.

The current ceramic preparation methods (such as hydrothermal method, solid-state reaction method, etc.) cause certain defects in the crystal structure of rare earth tantalum/niobate powder, such as microcracks and pores, and the existence of defects will make the ceramic material in the When the thermal barrier coating is used, the thermal conductivity increases greatly at high temperature, and the thermal insulation effect of the coating decreases.

SUMMARY OF THE INVENTION

The invention provides a two-phase rare earth tantalate ceramic and a preparation method thereof, so as to solve the problem that the existing ceramic preparation method causes a large number of defects inside the ceramic material and makes its thermal conductivity high.

In order to achieve the above object, the basic scheme of the present invention is:

A two-phase rare earth tantalate ceramic, the ceramic is composed of ScTaO ₄ phase and SmTaO ₄ phase, the molar ratio of Sm:Sc:Ta in the ceramic is x:(1-x):1, wherein 0<x<1 , the ceramic is composed of SmTaO ₄ phase and ScTaO ₄ phase, and the density of this ceramic is greater than 98%.

The technical principle and effect of this basic scheme are as follows:

1. The density of a two-phase rare earth tantalate ceramic in this basic scheme is greater than 98%, that is, the content of defects (cracks and pores) in the two-phase rare earth tantalate is very small, which makes the thermal conductivity of the ceramic at high temperature. It solves the problem that the thermal conductivity increases greatly when used as a thermal barrier coating in the prior art, and the service life of the coating increases due to the low defect content during the thermal cycle as a thermal barrier coating.

2. In this basic scheme, due to the low defect content in the two-phase rare earth tantalate, it can be used as a thermal barrier coating in harsh environments. Magnesium, alumina and silicon oxide) cannot effectively penetrate into the interior of the ceramic after being melted at high temperature, preventing the penetration of the molten oxide and the reaction with the ceramic material.

3. The two-phase formation is due to the large difference in ionic radius between Sm (0.108nm) and Sc (0.075nm), and Sm cannot replace Sc to enter the corresponding atomic position to form a solid solution during the reaction, and SmTaO ₄ is monoclinic phase while ScTaO ₄ is a metastable monoclinic phase, there is no free transition between the two phases, so two phases are formed. Researchers in the field usually believe that different phases have large differences in internal composition and crystal structure, so during the formation process of different phases, the interface energy at the phase interface is high, and various point or line defects are easily formed. The researchers in this field usually avoid the formation of the second phase in order to reduce the defects in the ceramic crystal, but the inventors of this scheme found that since the SmTaO ₄ phase and the ScTaO ₄ phase have similar compositions and the same structure, the experiment found that the phase interface is The defect content is low.

4. The thermal conductivity of the ceramic material in this basic scheme is low. Taking x=0.8 as an example, the molar ratio of Sc:Sm is 0.2:0.8. After the sintering is completed, the ScTaO ₄ phase is much less than the SmTaO ₄ phase. During the process, due to the small content of ScTaO ₄ , the growth of its grains is squeezed by the grain growth in the SmTaO ₄ phase, so that the final ScTaO ₄ grains are distributed among the SmTaO ₄ grains in an irregular shape, which in turn makes the unit Within the crystal structure within the area, the amount of grain boundaries increases, which in turn increases the scattering of phonons by grain boundaries and reduces thermal conductivity.

Further, a preparation method of a two-phase rare earth tantalate ceramic, comprising the following steps:

Step (1): Weigh Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and Ta ₂ O ₅ powder whose molar ratio of Sm:Sc:Ta is x:(1-x):1, add solvent and mix, and use a ball mill Carry out ball milling to obtain powder A;

Step (2): the powder A obtained in step (1) is dried and sieved for the first time to obtain powder B;

Step (3): The powder B obtained in step (2) is placed in a mold for compaction, and pre-sintering is performed after maintaining the pressure to form a block C, wherein the pressure-holding pressure is 100-200MPa, and the pressure-holding time is 10-20min , the pre-sintering temperature is 1000～1200℃, and the pre-sintering time is 5～10h;

Step (4): After the block C in the step (3) is cooled to room temperature, the grinding machine is used for grinding, and then the second sieving is performed to obtain the powder D;

Step (5): sintering the powder D in step (4) to obtain a two-phase rare earth tantalate ceramic, wherein the sintering temperature is 1700-1800° C., and the sintering time is 3-5h.

Beneficial effects: ceramics composed of SmTaO ₄ phase and ScTaO ₄ phase are prepared by the method of step (1) to step (5). When the ceramic is used as a thermal barrier coating, the thermal conductivity is low at high temperature and has good The thermal insulation performance and high thermal expansion coefficient at high temperature reduce the thermal mismatch stress between thermal barrier coatings or with the matrix material during thermal cycling.

The purpose of step (1) is to mechanically mix Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and Ta ₂ O ₅ powder uniformly, and the addition of solvent is to reduce the amount of Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and Ta ₂ The surface activity of O ₅ powder reduces the adhesion between powders and reduces the adhesion between powders.

The purpose of the step (2) is to remove the solvent in the powder A, and at the same time sieve out the large particle powder that may be bonded together in the step (1), so as to ensure the compactness of the final sintered block.

The purpose of holding the powder B in step (3) is to discharge the gas in the powder B under the action of pressure, thereby reducing the pores in the crystal structure of the block C, and the purpose of pre-sintering is to consume a part of the internal energy in the powder , reduce the sintering activity of powder B, increase the reaction temperature of powder B, prevent it from reacting at a lower temperature to form a second phase, and also prevent it from generating impurities in the final high-temperature sintering. , so no chemical reaction occurs at this time.

In step (4), the block with reduced sintering activity in step (3) is ground and further sieved to obtain powder D with small particle size,

The purpose of this step is that the small particle size powder D plays a role in helping nucleation in the reaction between rare earth oxide and tantalum oxide, and during the reaction between rare earth oxide and tantalum oxide, multiple powders D can be used as crystal nuclei for nucleation at the same time. At the same time, due to the method of grinding and sieving in this step, the particle size distribution of powder D is very uniform, and the size distribution of crystal nuclei formed by rare earth oxides and tantalum oxide is also relatively uniform, and there will be no excess in the whole reaction process. Large or too small grains are formed, so that the particle size distribution of the finally obtained rare earth tantalate ceramic grains is uniform;

It should be noted that when excessively large grains are formed during the reaction (this is the case with large nuclei), these large grains will grow rapidly, extruding smaller grains, so that In the final crystal structure of the ceramic, the grain boundary energy between the large grains and the small grains is too high, which makes point defects (pores) or line defects (microcracks) prone to appear at the grain boundaries, resulting in the low melting point resistance of the ceramic. The performance of oxide corrosion is reduced.

In the prior art, in order to shorten the preparation time, the powder is usually directly subjected to high-temperature sintering treatment after the powder is ground and mixed, so as to obtain the final desired ceramic. The reason for the large number of micro-cracks and pores inside.

Step (5) sintering to obtain a two-phase rare earth tantalate ceramic with a density greater than 98%, which has few internal pores, uniform grain size distribution, and few internal microcracks. It should be noted that researchers in the field It is generally believed that due to the different internal compositions and crystal structures of different phases, extrusion phenomena will occur during the formation process of different phases, making the interfacial energy at the phase interface high, and various points or points are easily formed here. Therefore, the current ceramics used as thermal barrier coatings usually have a single-phase structure, but the inventors of the present application have found through research that the two-phase rare earth tantalate prepared by the above method has many defects at the phase interface in the crystal structure. Therefore, the rare earth tantalate prepared by this method has lower thermal conductivity and higher thermal expansion coefficient.

Further, in the step (1), the time of ball milling is 6-20 h, and the rotational speed of the ball mill is 200-500 r/min.

Beneficial effects: by using the ball milling speed and time in the solution, the Sm ₂ O ₃ powder, the Sc ₂ O ₃ powder and the Ta ₂ O ₅ powder can be fully mixed uniformly.

Further, in the step (2), the drying temperature is 100-300° C., and the drying time is 10-20 h.

Beneficial effect: by using the drying temperature and time in this solution, the solvent in the powder can be fully volatilized.

Further, the mesh of the first sieving in the step (1) is 100-300 mesh.

Beneficial effects: The mesh of the present technical solution is used for sieving, and the large-sized powder particles in the powder A that are bonded together during the ball milling process are sieved to obtain the powder A with a uniform powder particle size distribution.

Further, in the step (4), the mesh of the second sieving is 300-600 mesh.

Beneficial effects: the meshes in this technical solution are used for sieving, and the large-diameter powder particles that are not completely ground during the grinding process are sieved to obtain powder D with a uniform powder particle size distribution, thereby improving the sintering performance of the block. density.

Further, in the step (4), the rotational speed of the grinding machine is 1000-2000 r/min, and the grinding time is 20-48 h.

Beneficial effects: The block C is ground by the grinding parameters in this scheme, and the block C can be ground sufficiently, and the obtained powder D has a small particle size and a relatively uniform particle size distribution.

Further, the purity of the Sm ₂ O ₃ powder and the Ta ₂ O ₅ powder in the step (1) is not less than 99.9%.

Beneficial effects: adopting powder with higher purity reduces the content of introduced impurity elements, avoids the introduction of impurity elements into the crystal to form micro-cracks, and reduces the compactness of the final sintered block.

Further, the solvent in the step (1) is ethanol or distilled water.

Beneficial effect: Ethanol and distilled water have better dispersibility for Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and Ta ₂ O ₅ powder, so that Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and Ta ₂ O ₅ powder can be more Mix well.

Further, the molar ratio of the Sm ₂ O ₃ powder, the Sc ₂ O ₃ powder and the Ta ₂ O ₅ powder to the solvent in the step (1) is (3:1)˜(5:1).

Beneficial effects: The inventors have verified through experiments that when the ratio of Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and Ta ₂ O ₅ powder to the solvent is within this range, the obtained powder A is most fully mixed.

Description of drawings

Fig. 1 is the XRD pattern of the two-phase rare earth tantalate ((SmTaO ₄ ) _0.8 (ScTaO ₄ ) _0.2 ) ceramic prepared in Example 1 of the present invention;

2 is a SEM image of the two-phase rare earth tantalate ((SmTaO ₄ ) _0.6 (ScTaO ₄ ) _0.4 ) ceramic prepared in Example 2 of the present invention;

Fig. 3 is the curve diagram of the thermal conductivity of the two-phase rare earth tantalate ((SmTaO ₄ ) _0.8 (ScTaO ₄ ) _0.2 ) ceramic prepared in Example 1 of the present invention as a function of temperature;

FIG. 4 is a graph of the thermal expansion coefficient of the two-phase rare earth tantalate ((SmTaO ₄ ) _0.8 (ScTaO ₄ ) _0.2 ) ceramic prepared in Example 1 of the present invention as a function of temperature.

Detailed ways

The following is further described in detail by specific embodiments:

A two-phase rare earth tantalate ceramic, the molar ratio of Sm:Sc:Ta in the ceramic is x:(1-x):1, wherein 0<x<1, the ceramic is composed of SmTaO ₄ phase and ScTaO ₄ phase , the density of the ceramic is greater than 98%.

The preparation method of the above two-phase rare earth tantalate ceramics comprises the following steps:

Step (1): Weigh Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and Ta ₂ O ₅ powder whose molar ratio of Sm:Sc:Ta is x:(1-x):1, add distilled water or ethanol solvent to carry out Mixing, wherein the molar ratio of the above three powders (Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and Ta ₂ O ₅ powder) to the solvent is (3:1)～(5:1), and the ball mill is used for ball milling. After drying, powder A is obtained; wherein the ball mill adopts a variable frequency planetary ball mill, the model is XQM, the ball milling time is 6-20h, the rotation speed of the ball mill is 200-500r/min, and the raw materials Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and The purity of the Ta ₂ O ₅ powder is not less than 99.9%.

Step (2): the powder obtained in step (1) is dried and sieved for the first time to obtain powder B, wherein the drying temperature is 100-300° C., the drying time is 10-20 h, and the mesh size of the first sieving is 100 to 300 meshes.

Step (3): The powder B obtained in step (2) is placed in a mold for compaction, and pre-sintering is performed after maintaining the pressure to form a block C, wherein the pressure-holding pressure is 100-200MPa, and the pressure-holding time is 10-20min , the pre-sintering temperature is 1000-1200°C, the pre-sintering time is 5-10h, and the heating rate is 100°C/min.

Step (4): After the block C in step (3) is cooled to room temperature, the grinding machine is used for grinding, wherein the grinding machine adopts a vertical laboratory sand mill, the model is WT0.3, and the grinding speed is 1000～2000r/ min, the grinding time is 20-48h, and then the second sieving is performed to obtain powder D, and the mesh of the second sieving is 300-600 mesh.

Step (5): sintering the powder D in step (4) to obtain the above two-phase rare earth tantalate ceramic powder, the sintering temperature is 1700-1800°C, the heating rate is 50°C/min, and the sintering time is 3-5h .

When the performance of the ceramic needs to be tested, the block structure of the ceramic needs to be obtained, and the above step (5) is sintered and subjected to pressure treatment, wherein the tableting pressure is 200-300MPa, and the tableting time is 20-30min.

Two-phase rare earth tantalate ceramics composed of SmTaO ₄ phase and ScTaO ₄ phase were obtained by the above method. In order to fully illustrate the low thermal conductivity and high thermal expansion coefficient of the two-phase rare earth tantalate ceramics prepared by the above method, seven groups of examples are selected for description.

Table 1 is the concrete parameter of the embodiment of the present invention 1～7:

List two groups of comparative examples and the two-phase rare earth tantalate ceramics obtained in Examples 1 to 7 for comparative experiments:

Comparative Example 1: The difference from Example 1 is that the operations of the above steps (3) and (4) are not performed.

Comparative Example 2: The difference from Example 1 is that when step (5) is performed, the sintering temperature is 1200-1400°C.

The ceramic blocks obtained from Examples 1 to 7 and Comparative Examples 1 to 2 are now tested:

1. XRD characterization:

The ceramic blocks prepared in Examples 1-7 and Comparative Examples 1-2 were detected by X-ray diffractometer, and the rare earth tantalate ((SmTaO ₄ ) _0.8 (ScTaO ₄ ) _0.2 ) ceramic obtained in Example 1 was used as For example, the XRD pattern is shown in Figure 1. The diffraction peaks obtained from the test results correspond to the standard PDF cards PDF#24-1010 and PDF#24-1017 of SmTaO4 and ScTaO4, indicating that the sample contains both SmTaO4 and ScTaO4. phase, and there is no third phase diffraction peak. The crystal structure of SmTaO ₄ is a monoclinic phase with α=γ=90° and β=95.7°, and the density is 8.52 g/cm ₃ . The crystal structure of ScTaO4 is a metastable monoclinic phase, wherein α=γ=90° and β=91.6°, and the density is 6.92 g/cm ₃ .

2. SEM characterization:

The salt ceramic blocks prepared in Examples 1-7 and Comparative Examples 1-2 were detected by scanning electron microscope, and the rare earth tantalate ((SmTaO ₄ ) _0.6 (ScTaO ₄ ) _0.4 ) ceramic obtained in Example 2 was taken as an example , and its SEM pattern is shown in Figure 2. Under backscattering conditions, the atomic contrast of the element with the higher atomic number is lower, so the color is lighter. Therefore, the lighter area in Figure 2 is ScTaO4 and the rest of the grains are SmTaO4. It can be seen that the ScTaO4 grains are squeezed by the more SmTaO4 grains during the growth process, making their shape irregular. At the same time, according to Fig. 2, it is observed that the grain size of rare earth tantalate ((SmTaO ₄ ) _0.6 (ScTaO ₄ ) _0.4 ) ceramic block is between 1 and 10 microns, and the bonding between different grains is good, and there is no obvious crack or pores. , and the density reached 98.4% by testing.

While the ceramic blocks obtained in Comparative Example 1 and Comparative Example 2 contain more pores, especially the ceramic blocks obtained in Comparative Example 1, in addition to more pores, also contain certain inclusions (not completely sintered). Sm ₂ O ₃ , Sc ₂ O ₃ and Ta ₂ O ₅ ), resulting in more micro-cracks inside the crystal.

3. Density detection:

The ceramic blocks obtained in Examples 1-7 and Comparative Examples 1-2 were measured by the Archimedes drainage method. The measurement results are shown in Table 2. The results are that the ceramic blocks obtained in Examples 1-7 The density is more than 98%.

It can be seen from the above SEM characterization and density detection results that the two-phase rare earth tantalate ceramic block prepared by the above example has few microcracks and extremely low porosity, which makes the ceramic block high in density.

4. Thermal conductivity detection

The ceramic blocks prepared in Examples 1-7 and Comparative Examples 1-2 were ground into The thermal conductivity of each ceramic block at 800 ° C is shown in Table 2. The rare earth tantalate obtained in Example 1 ((SmTaO ₄ ) _0.8 ( Take ScTaO ₄ ) _0.2 ) ceramics as an example. The graph of the thermal conductivity of the ceramic block with temperature is shown in Figure 3. It can be seen that with the continuous increase of the temperature, the thermal conductivity of the ceramic block decreases sharply. When the temperature is 800 At ℃, the thermal conductivity of rare earth tantalate ((SmTaO ₄ ) _0.8 (ScTaO ₄ ) _0.2 ) ceramic block decreased to 1.5Wm ^-1 .K ^-1 , indicating that it has excellent thermal insulation ability in high temperature environment.

5. Thermal expansion coefficient detection

The ceramic blocks prepared in Examples 1 to 7 and Comparative Examples 1 to 2 were prepared into columnar samples with a size of 1 × 2 × 10 mm, which were detected by a thermomechanical analyzer (model TMA 402F3) from NETZSCH, Germany. The rate is 5 °C/min, and the thermal expansion coefficient of each sample is detected. The thermal expansion coefficient of each ceramic block at 1200 °C is shown in Table 2 below. The rare earth tantalate obtained in Example 1 ((SmTaO ₄ ) _0.8 (ScTaO ₄ ) _0.2 ) ceramics as an example, the curve diagram of the thermal expansion coefficient of the ceramic block with temperature is obtained, as shown in Figure 4, it can be seen that with the continuous increase of the temperature, the thermal expansion coefficient of the ceramic block continues to increase, and when the temperature is 1200 ℃ When , the thermal expansion coefficient of the rare earth tantalate ((SmTaO ₄ ) _0.8 (ScTaO ₄ ) _0.2 ) ceramic block increases to 8.9×10 ^-6 K ^-1 , indicating that the ceramic block has excellent thermal insulation ability under high temperature environment .

Table 2

In summary, the two-phase rare earth salt ceramics prepared in Examples 1 to 7 have very few cracks and pores in the crystal structure, so that their density is high, all above 98%. When the powder is used as a thermal barrier coating, it has The low thermal conductivity shows good thermal insulation performance, and at the same time, it has a high thermal expansion coefficient at high temperature, which reduces the thermal mismatch stress between coatings or between the substrate material.

The above descriptions are only embodiments of the present invention, and common knowledge such as well-known specific structures and characteristics in the solution are not described too much here. It should be pointed out that for those skilled in the art, some modifications and improvements can be made without departing from the structure of the present invention. These should also be regarded as the protection scope of the present invention, and these will not affect the implementation of the present invention. Effectiveness and utility of patents. The scope of protection claimed in this application shall be based on the content of the claims, and the descriptions of the specific implementation manners in the description can be used to interpret the content of the claims.

Claims (10)

1. a two-phase rare earth tantalate ceramic is characterized in that: this ceramic is made up of ScTaO ₄ phase and SmTaO ₄ phase, and the mol ratio of Sm:Sc:Ta in this ceramic is x:(1-x):1, Where 0<x<1, the density of the ceramic is greater than 98%. 2. the preparation method of a kind of two-phase rare earth tantalate ceramics according to claim 1, is characterized in that: comprises the following steps: Step (1): Weigh Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and Ta ₂ O ₅ powder whose molar ratio of Sm:Sc:Ta is x:(1-x):1, add solvent and mix, and use a ball mill Carry out ball milling to obtain powder A; Step (2): the powder A obtained in step (1) is dried and sieved for the first time to obtain powder B; Step (3): The powder B obtained in step (2) is placed in a mold for compaction, and pre-sintering is performed after maintaining the pressure to form a block C, wherein the pressure-holding pressure is 100-200MPa, and the pressure-holding time is 10-20min , the pre-sintering temperature is 1000～1200℃, and the pre-sintering time is 5～10h; Step (4): After the block C in the step (3) is cooled to room temperature, the grinding machine is used for grinding, and then the second sieving is performed to obtain the powder D; Step (5): sintering the powder D in step (4) to obtain a two-phase rare earth tantalate ceramic, wherein the sintering temperature is 1700-1800° C., and the sintering time is 3-5h. 3. The preparation method of a two-phase rare earth tantalate ceramic according to claim 2, characterized in that: in the step (1), the time of ball milling is 6～20h, and the rotating speed of the ball mill is 200～500r/min . 4 . The method for preparing a two-phase rare earth tantalate ceramic according to claim 2 , wherein in the step (2), the drying temperature is 100-300° C., and the drying time is 10-20 h. 5 . 5 . The method for preparing a two-phase rare earth tantalate ceramic according to claim 2 , wherein the mesh of the first sieving in the step (2) is 100-300 meshes. 6 . 6 . The method for preparing a two-phase rare earth tantalate ceramic according to claim 2 , wherein the mesh of the second sieving in the step (4) is 300-600 mesh. 7 . 7 . The method for preparing a two-phase rare earth tantalate ceramic according to claim 2 , wherein in the step (4), the rotating speed of the grinding machine is 1000～2000r/min, and the grinding time is 20～48h. 8 . . 8 . The method for preparing a two-phase rare earth tantalate ceramic according to claim 2 , wherein: in the step (1), Sm ₂ O ₃ powder, Sc ₂ O ₃ powder and Ta ₂ O ₅ powder The purity is not less than 99.9%. 9 . The method for preparing a two-phase rare earth tantalate ceramic according to claim 2 , wherein the solvent in the step (1) is ethanol or distilled water. 10 . 10 . The method for preparing a two-phase rare earth tantalate ceramic according to claim 2 , wherein the Sm ₂ O ₃ powder and the Sc ₂ O ₃ powder in the step (1) are: 11 . The molar ratio of Ta ₂ O ₅ powder and solvent is (3:1)～(5:1).