RARE EARTH TANTALATE CERAMIC RESISTING CORROSION OF LOW MELTING POINT OXIDE AND PREPARATION METHOD THEREFOR

Abstract

The present disclosure discloses a rare earth tantalate ceramic resisting corrosion of a low melting point oxide. A general chemical formula of the ceramic is RETaO.sub.4. A method for preparing the ceramic includes: weighing RE.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder and adding to a solvent to mix, and ball milling the mixed solution with a ball mill to obtain powder A; drying the powder A, and sieving the powder A for a first time to obtain powder B; placing the powder B in a mold for compaction, pre-sintering the powder B to form a block C, cooling the block C to room temperature, grounding the block C with a grinder, and sieving the block C for a second time to obtain powder D; and sintering the powder D to obtain the rare earth tantalate ceramic. The ceramic has high density and strong corrosion resistance to low melting point oxides.

Claims

1. A rare earth tantalate ceramic resisting corrosion of a low melting point oxide, wherein a general chemical formula of the ceramic is RETaO.sub.4, a crystal structure of the ceramic has a monoclinic phase, a lattice space group of the ceramic is l2(5), and a density of the ceramic is greater than 98%.

2. The rare earth tantalate ceramic resisting corrosion of the low melting point oxide according to claim 1, wherein RE is one or a combination of Sm, Eu, Gd, Dy, Ho, and Er.

3. A method for preparing a rare earth tantalate ceramic resisting corrosion of a low melting point oxide, wherein a general chemical formula of the ceramic is RETaO.sub.4, a crystal structure of the ceramic has a monoclinic phase, a lattice space group of the ceramic is l2(5), and a density of the ceramic is greater than 98%; wherein the method comprising: operation (1): weighing RE.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder with a molar ratio of RE:Ta of 1:1 and adding to a solvent to mix, and ball milling the mixed solution with a ball mill to obtain powder A; operation (2): drying the powder A obtained in operation (1), and sieving the powder A for a first time to obtain powder B; operation (3): placing the powder B obtained in operation (2) in a mold for compaction, holding a pressure, and pre-sintering the powder B to form a block C, wherein a holding pressure ranges from 200 to 300 MPa, a holding-pressure time ranges from 1 to 10 min, a pre-sintering temperature ranges from 800 to 1200° C., and a pre-sintering time ranges from 10 to 20 h; operation (4): cooling the block C in operation (3) to room temperature, grounding the block C with a grinder, and sieving the block C for a second time to obtain powder D; and operation (5): sintering the powder D in operation (4) to obtain the rare earth tantalate ceramic resisting corrosion of the low melting point oxide, wherein a sintering temperature ranges from 1500 to 1800° C., and a pressure sintering time ranges from 5 to 30 min.

4. The method for preparing the rare earth tantalate ceramic resisting corrosion of the low melting point oxide according to claim 3, wherein in operation (1), a time of ball milling ranges from 10 to 24 h, and a rotation speed of the ball mill ranges from 300 to 600 r/min.

5. The method for preparing the rare earth tantalate ceramic resisting corrosion of the low melting point oxide according to claim 3, wherein in operation (2), a drying temperature ranges from 60 to 100° C., and a drying time ranges from 5 to 15 h.

6. The method for preparing the rare earth tantalate ceramic resisting corrosion of the low melting point oxide according to claim 3, wherein meshes for the first sieving in operation (2) range from 100 to 300 meshes, and meshes for the second sieving in operation (4) range from 300 to 600 meshes.

7. The method for preparing the rare earth tantalate ceramic resisting corrosion of the low melting point oxide according to claim 3, wherein in operation (4), a rotation speed of the grinder ranges from 1000 to 2000 r/min, and a grinding time ranges from 20 to 48 h.

8. The method for preparing the rare earth tantalate ceramic resisting corrosion of the low melting point oxide according to claim 7, wherein a purity of the RE.sub.2O.sub.3 powder and the Ta.sub.2O.sub.5 powder in operation (1) is not less than 99.9%.

9. The method for preparing the rare earth tantalate ceramic resisting corrosion of the low melting point oxide according to claim 3, wherein the solvent in operation (1) is ethanol or distilled water.

10. The method for preparing the rare earth tantalate ceramic resisting corrosion of the low melting point oxide according to claim 3, wherein a molar ratio of the RE.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder to the solvent in operation (1) ranges from 3:1 to 5:1.

11. A rare earth ytterbium tantalate ceramic resisting corrosion of a low melting point oxide, wherein the ceramic is sintered from Yb.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder, a general chemical formula of the ceramic is YbTaO.sub.4 or Yb.sub.3TaO.sub.7, a crystal structure of the ceramic has a single phase, and a density of the ceramic is greater than 97%.

12. A method for preparing the rare earth ytterbium tantalate ceramic resisting corrosion of the low melting point oxide according to claim 11, comprising: operation (1): weighing Yb.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder with a molar ratio of Yb:Ta of 1:1 and adding to a solvent to mix, and ball milling the mixed solution with a ball mill to obtain powder A; operation (2): drying the powder A obtained in operation (1), and sieving the powder A for a first time to obtain powder B; operation (3): placing the powder B obtained in operation (2) in a mold for compaction, holding a pressure, and pre-sintering the powder B to form a block C, wherein a holding pressure ranges from 100 to 200 MPa, a holding-pressure time ranges from 10 to 20 min, a pre-sintering temperature ranges from 1000 to 1200° C., and a pre-sintering time ranges from 10 to 20 h; operation (4): cooling the block C in operation (3) to room temperature, grounding the block C with a grinder, and sieving the block C for a second time to obtain powder D; and operation (5): sintering the powder D in operation (4) to obtain the rare earth ytterbium tantalate ceramic resisting corrosion of the low melting point oxide, wherein a sintering temperature ranges from 1700 to 1800° C., and a pressure sintering time ranges from 5 to 10 h.

13. The method for preparing the rare earth ytterbium tantalate ceramic resisting corrosion of the low melting point oxide according to claim 12, wherein a time of ball milling in operation (1) ranges from 10 to 24 h, and a rotation speed of the ball mill ranges from 300 to 500 r/min.

14. The method for preparing the rare earth ytterbium tantalate ceramic resisting corrosion of the low melting point oxide according to claim 12, wherein a drying temperature in operation (2) ranges from 50 to 200° C., and a drying time ranges from 8 to 24 h.

15. The method for preparing the rare earth ytterbium tantalate ceramic resisting corrosion of the low melting point oxide according to claim 12, wherein meshes for the first sieving in operation (2) range from 100 to 300 meshes.

16. The method for preparing the rare earth ytterbium tantalate ceramic resisting corrosion of the low melting point oxide according to claim 12, wherein meshes for the second sieving in operation (4) range from 300 to 600 meshes.

17. The method for preparing the rare earth ytterbium tantalate ceramic resisting corrosion of the low melting point oxide according to claim 12, wherein in operation (4), a rotation speed of the grinder ranges from 1000 to 2000 r/min, and a grinding time ranges from 20 to 48 h.

18. The method for preparing the rare earth ytterbium tantalate ceramic resisting corrosion of the low melting point oxide according to claim 12, wherein a purity of the Yb.sub.2O.sub.3 powder and the Ta.sub.2O.sub.5 powder in operation (1) is not less than 99.9%.

19. The method for preparing the rare earth ytterbium tantalate ceramic resisting corrosion of the low melting point oxide according to claim 12, wherein the solvent in operation (1) is ethanol or distilled water.

20. The method for preparing the rare earth ytterbium tantalate ceramic resisting corrosion of the low melting point oxide according to claim 12, wherein a molar ratio of the Yb.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder to the solvent in operation (1) ranges from 3:1 to 5:1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIG. 1 shows an XRD diagram of a rare earth tantalate (HoTaO.sub.4) ceramic prepared in Example 5 according to the present disclosure.

[0073] FIG. 2 shows an SEM diagram of a rare earth tantalate (HoTaO.sub.4) ceramic prepared in Example 5 according to the present disclosure.

[0074] FIG. 3 shows a diagram of a rare earth tantalate (HoTaO.sub.4) ceramic prepared in Example 5 after a CMAS high temperature corrosion resistance test according to the present disclosure.

[0075] FIG. 4 shows a diagram of a rare earth tantalate (ErTaO.sub.4) ceramic prepared in Example 6 after a CMAS high temperature corrosion resistance test according to the present disclosure.

[0076] FIG. 5 shows an XRD diagram of a rare earth tantalate (RETaO.sub.4) ceramic prepared in Examples 1 to 6 after a CMAS high temperature corrosion resistance test according to the present disclosure.

[0077] FIG. 6 shows an XRD diagram of a Ytterbium tantalate (YbTaO.sub.4) ceramic prepared in Example 13 according to the present disclosure.

[0078] FIG. 7 shows an SEM diagram of a Ytterbium tantalate (YbTaO.sub.4) ceramic prepared in Example 13 according to the present disclosure.

[0079] FIG. 8 shows a diagram of a Ytterbium tantalate (YbTaO.sub.4) ceramic prepared in Example 13 after a CMAS high temperature corrosion resistance test at 1300° C. for 10 hours according to the present disclosure.

[0080] FIG. 9 shows an XRD diagram of a Ytterbium tantalate (YbTaO.sub.4) ceramic prepared in Example 13 for alumina compatibility detection according to the present disclosure.

DETAILED DESCRIPTION

[0081] The embodiments of the present disclosure will be described in further detail below.

[0082] The present disclosure provides a rare earth tantalate ceramic resisting corrosion of a low melting point oxide. A general chemical formula of the ceramic is RETaO.sub.4. RE is one or a combination of Sm, Eu, Gd, Dy, Ho, and Er. A crystal structure of the ceramic has a monoclinic phase, a lattice space group of the ceramic is l2(5), and a density of the ceramic is greater than 98%.

[0083] The present disclosure provides a method for preparing the rare earth tantalate ceramic resisting corrosion of the low melting point oxide. The method includes the following operations:

[0084] Operation (1): weighing RE.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder with a molar ratio of RE:Ta being 1:1 and adding to a distilled water or ethanol solvent to mix, where a molar ratio of the RE.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder to solvent ranges from 3:1 to 5:1, ball milling the mixed solution with a ball mill, and drying the mixed solution to obtain powder A. The ball mill may be a frequency conversion planetary ball mill, and the model of the ball mill may be XQM. A ball milling time ranges from 10 to 24 h, a rotation speed of the ball mill ranges from 300 to 600 r/min, and a purity of the raw materials, that is, the RE.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder, is not less than 99.9%.

[0085] Operation (2): drying the powder A obtained in operation (1), and sieving the powder A for a first time to obtain powder B, where a drying temperature ranges from 60 to 100° C., a drying time ranges from 5 to 15 h, and meshes for the first sieving ranges 100 to 300 meshes.

[0086] Operation (3): placing the powder B obtained in operation (2) in a mold for compaction, holding a pressure, and pre-sintering the powder B to form a block C, where a holding pressure ranges from 200 to 300 MPa, a holding-pressure time ranges from 1 to 10 min, a pre-sintering temperature ranges from 800 to 1200° C., a pre-sintering time ranges from 10 to 20 h, and a heating rate is 100° C./min.

[0087] Operation (4): cooling the block C in operation (3) to room temperature; grounding the block C with a grinder, where the grinder may be a vertical laboratory sand mill, the model of the grinder may be WT0.3, a grinding speed ranges from 1000 to 2000 r/min, and a grinding time ranges from 20 to 48 h; and sieving the block C for a second time to obtain powder D, where meshes for the second sieving range from 300 to 600 meshes.

[0088] Operation (5): sintering the powder D in operation (4) to obtain the above rare earth tantalate ceramic resisting corrosion of the low melting point oxide, where a sintering temperature ranges from 1500 to 1800° C., a heating rate is 50° C./min, and a sintering time ranges from 5 to 30 h. The obtained powder material can be used for spraying to form a thermal barrier coating after granulation.

[0089] When the performance of the ceramic needs to be tested, a bulk structure of the ceramic needs to be obtained, and a pressure treatment is carried out during the sintering in the above operation (5), where a pressure ranges from 40 to 100 MPa, and a pressuring time ranges from 5 to 30 min. In this way, a ceramic bulk material with the same composition and crystal structure as the powder is formed.

[0090] A RETaO.sub.4 ceramic with a density greater than 98% is obtained using the above method. 12 sets of examples are selected to fully illustrate the compactness of the RETaO.sub.4 ceramic prepared by the above method.

[0091] Table 1 shows the specific parameters of Examples 1 to 6 of the present disclosure:

TABLE-US-00001 Examples 1 2 3 4 5 6 RE.sub.2O.sub.3 (g) Sm.sub.2O.sub.3 5.0000 Eu.sub.2O.sub.3 7.6566 Gd.sub.2O.sub.3 7.8872 Dy.sub.2O.sub.3 8.1134 Ho.sub.2O.sub.3 5.0000 Er.sub.2O.sub.3 6.6578 Ta.sub.2O.sub.5 (g) 6.331 9.6100 9.6100 9.6100 5.8470 7.6880 Ball milling Rotation speed (r/min) 300 420 300 300 350 400 Time (h) 12 10 24 12 13 15 Drying Temperature (° C.) 70 92 75 100 80 90 Time (h) 12 8 12 5 11 9 First sieving Meshes 300 200 300 300 200 200 First Holding pressure (MPa) 200 260 280 290 220 250 compaction Holding pressure time 5 9 10 10 3 2 (min) Pre-sintering Sintering temperature 1000 1200 1000 1150 1100 1050 (° C.) Sintering time (h) 12 10 12 11 11 10 Grinding Rotation speed (r/min) 2000 1500 1300 1000 1300 1800 Time (h) 20 30 40 48 40 25 Second sieving Meshes 600 500 500 600 300 400 Powder Sintering temperature 1300 1500 1450 1800 1400 1500 sintering (° C.) Sintering time (h) 30 15 17 5 20 15 Block sintering Pressure (MPa) 100 50 40 60 70 50 Pressuring time (min) 5 20 30 12 8 20

[0092] Table 2 shows the specific parameters of Examples 7 to 12 of the present disclosure:

TABLE-US-00002 Examples 7 8 9 10 11 12 RE.sub.2O.sub.3 (g) Sm.sub.2O.sub.3 6.7840 6.6970 Eu.sub.2O.sub.3 6.3220 Gd.sub.2O.sub.3 6.8240 6.6970 6.1990 Dy.sub.2O.sub.3 6.8240 7.0090 6.3220 Ho.sub.2O.sub.3 6.3220 6.1990 Er.sub.2O.sub.3 6.7840 7.0090 Ta.sub.2O.sub.5 (g) 8.2000 8.2000 8.2000 8.2000 7.6000 7.4000 Ball milling Rotation speed 400 420 500 500 600 550 (r/min) Time (h) 12 24 12 12 10 15 Drying Temperature (° C.) 60 70 70 100 80 90 Time (h) 15 13 13 6 10 8 First sieving Meshes 300 100 300 300 200 200 First Holding pressure 200 260 300 290 220 250 compaction (MPa) Holding pressure 5 9 1 10 5 6 time (min) Pre-sintering Sintering 800 1200 1000 900 1100 1150 temperature (° C.) Sintering time (h) 20 10 15 16 10 13 Grinding Rotation speed 2000 1500 1300 1000 1300 1800 (r/min) Time (h) 20 30 40 48 40 25 Second Meshes 600 500 500 600 400 400 sieving Powder Sintering 1300 1500 1450 1800 1400 1500 sintering temperature (° C.) Sintering time (h) 30 15 17 5 20 15 Block sintering Pressure (MPa) 100 50 40 60 70 50 Pressuring time 5 20 30 12 8 20 (min)

[0093] Two sets of control examples are listed and compared with the rare earth tantalate ceramics obtained in Examples 1-12:

[0094] Control example 1: The difference from Example 1 is that the above operations (3) and (4) are not performed in control example 1.

[0095] Control example 2: The difference from Example 1 is that the sintering temperature in operation (5) ranges from 1100 to 1300° C., and the sintering time ranges from 3 to 5 hours in control example 2.

[0096] The ceramic blocks obtained in Examples 1 to 12 and control examples 1 to 2 are now tested:

[0097] 1. XRD Characterization:

[0098] An X-ray diffractometer was used to test the ceramic blocks prepared in Examples 1-12 and control examples 1-2. Take the rare earth tantalate (HoTaO.sub.4) ceramic block obtained in Example 5 as an example, the XRD pattern is shown in FIG. 1. The diffraction peaks in the XRD test results of the HoTaO.sub.4 ceramic sample in FIG. 1 correspond to the standard peaks of the standard PDF card #24-0478, and there is no second-phase diffraction peak, indicating that the prepared sample is a single-phase HoTaO.sub.4 ceramic, its crystal structure has a monoclinic phase, where α=γ=90° and β=95.5°, the density is 9.71 g/cm3, and the lattice space group is l2(5). In the meantime, XRD detection shows that the rare earth tantalic (HoTaO.sub.4) ceramic block has no other impurities.

[0099] 2. SEM Characterization:

[0100] The ceramic blocks prepared in Examples 1 to 12 and control examples 1 to 2 were detected by a scanning electron microscopy (SEM). Take the rare earth tantalate (HoTaO.sub.4) ceramic block prepared in Example 5 as an example. The SEM spectrum is shown in FIG. 2. The SEM spectrum in FIG. 2 shows that the HoTaO.sub.4 ceramic sample has good crystallization, uniform crystal grain size, and clear grain boundaries, and no second phase is seen within a crystal grain or between the crystal grains, which is consistent with the XRD results. FIG. 2 shows that there are very few cracks and pores in the rare earth tantalate (HoTaO.sub.4) ceramic block, indicating that the ceramic does not generate excessive pressure and stress during the sintering process, and a density reaches 99.1%.

[0101] The ceramic blocks obtained in control example 1 and control example 2 contain many pores. In particular, the ceramic block obtained in control example 1 contains a certain amount of inclusions (not fully sintered RE.sub.2O.sub.3 and Ta.sub.2O.sub.5 powders) in addition to many pores, making more microcracks appear inside the crystal.

[0102] 3. Density Detection:

[0103] The ceramic blocks prepared in Examples 1 to 12 and control examples 1 to 2 were measured using an Archimedes drainage method. The measurement results are shown in Table 3. It can be seen that the densities of ceramic blocks obtained in Examples 1 to 12 are greater than 98%.

[0104] Table 3 shows the densities measured in Examples 1 to 12 and control examples 1 to 2.

TABLE-US-00003 Example Example Example Example1 Example2 3 4 5 Example6 Example7 Density 99.2 99.14 99.25 99.15 99.1 98.2 98.9 (%) Example Example Example control control Example8 Example9 10 11 12 example 1 example 2 Density 98.5 98.1 98.7 98.4 98.3 76.2 81.2 (%)

[0105] 3. High Temperature Resistance CMAS Corrosion Test:

[0106] 3.1 CMAS Preparation

[0107] After mixing aluminum oxide (Al.sub.2O.sub.3), magnesium oxide (MgO), calcium oxide (CaO) and silicon oxide (SiO.sub.2) in a molar ratio of 15:19:22:44, the mixed oxides were added to distilled water, and ground and mixed in a grinder to obtain a uniform and fine powder, where the speed of the grinder was 1000 r/min, and the grinding time was 20 h. The ground powder was dried at 100° C. for 10 hours and pre-sintered at 1000° C. for 5 hours to obtain a block, and then the block was ground and sieved by a 300-mesh sieve to obtain a uniform CMAS powder.

[0108] The CMAS powder prepared by the above method shows the proportion of CMAS components in the front inlet of the engine turbine when the aero engine works in a harsh environment.

[0109] 3.2 Corrosion Test

[0110] The above CMAS powder was laid on the surface of the rare earth tantalate ceramic (RETaO.sub.4) blocks prepared in Examples 1-12, where the amount of CMAS powder was 15 mg/cm2, and then high-temperature sintering was performed at a sintering temperature of 1200-1500° C., a holding-temperature time ranges from 5 to 20 h.

[0111] Take Examples 1 to 6 as an example, FIG. 3 shows a diagram of the rare earth tantalate (HoTaO.sub.4) ceramic prepared in Example 5 after being sintered at 1300° C. for 6 hours in the CMAS high temperature corrosion resistance test. FIG. 4 shows a diagram of the rare earth tantalate (ErTaO.sub.4) ceramic prepared in Example 6 after being sintered at 1500° C. for 13 hours in the CMAS high temperature corrosion resistance test. The blocks with a pie shape in FIGS. 3-4 are the sintered ceramic blocks, and the particles on the surface of the blocks are CMAS powder. In the meanwhile, XRD detection was performed on the rare earth tantalate (RETaO.sub.4) blocks obtained in Examples 1 to 6, and the XRD pattern is shown in FIG. 5.

[0112] Referring to FIGS. 3-5, it can be seen that there is still a large amount of CMAS powder on the surface of each ceramic sample. The melting point of the CMAS powder is lower than 1200° C. After holding temperature for several hours at high temperature (greater than 1200° C.), it shows that the molten CMAS liquid has not reacted with the ceramic material, and it is difficult to penetrate the ceramic material, only a small amount of MgO is detected in the rare earth tantalate (ErTaO.sub.4) ceramic obtained in Example 8, indicating that CMAS is difficult to react with the rare earth tantalate ceramic material at this temperature, which proves the excellent CMAS corrosion resistance characteristics of ceramic materials. Normally, after other ceramic materials that are not resistant to CMAS corrosion, such as YSZ, are kept at a high temperature for several hours, the molten CMAS liquid reacts with YSZ and penetrates the ceramic, leaving no CMAS powder remaining on the surface.

[0113] In summary, the rare earth tantalate (RETaO.sub.4) ceramics prepared in Examples 1 to 12 have very few microcracks and pores in the crystal structure, resulting in high density, which is above 98%. The ceramics have good corrosion resistance to low melting point oxides. When the temperature reaches 1200-1500° C., the rare earth tantalate (RETaO.sub.4) ceramic block hardly reacts with the CMAS powder, and its high temperature CMAS corrosion resistance is much greater than that of YSZ.

[0114] The present disclosure further provides a rare earth ytterbium tantalate ceramic resisting corrosion of a low melting point oxide. A general chemical formula of the ceramic is YbTaO.sub.4 or Yb.sub.3TaO.sub.7. A crystal structure of the YbTaO.sub.4 ceramic has a monoclinic phase, a lattice space group of the YbTaO.sub.4 ceramic is l2(5). A crystal structure of the Yb.sub.3TaO.sub.7 ceramic has a cubic phase, a lattice space group of the Yb.sub.3TaO.sub.7 ceramic is Fm-3 m. The densities of the above two ceramics are both greater than 97%.

[0115] The present disclosure provides a method for preparing the rare earth tantalate ceramic resisting corrosion of the low melting point oxide. The method includes the following operations:

[0116] Operation (1): weighing Yb.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder with a molar ratio of Yb:Ta being 1:1 and adding to a distilled water or ethanol solvent to mix, where a molar ratio of the Yb.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder to solvent ranges from 3:1 to 5:1, ball milling the mixed solution with a ball mill, and drying the mixed solution to obtain powder A. The ball mill may be a frequency conversion planetary ball mill, and the model of the ball mill may be XQM. A ball milling time ranges from 10 to 24 h, a rotation speed of the ball mill ranges from 300 to 500 r/min, and a purity of the raw materials, that is, the Yb.sub.2O.sub.3 powder and Ta.sub.2O.sub.5 powder, is not less than 99.9%.

[0117] Operation (2): drying the powder A obtained in operation (1), and sieving the powder A for a first time to obtain powder B, where a drying temperature ranges from 50 to 200° C., a drying time ranges from 8 to 24 h, and meshes for the first sieving ranges 100 to 300 meshes.

[0118] Operation (3): placing the powder B obtained in operation (2) in a mold for compaction, holding a pressure, and pre-sintering the powder B to form a block C, where a holding pressure ranges from 100 to 200 MPa, a holding-pressure time ranges from 10 to 20 min, a pre-sintering temperature ranges from 1000 to 1200° C., a pre-sintering time ranges from 10 to 20 h, and a heating rate is 100° C./min.

[0119] Operation (4): cooling the block C in operation (3) to room temperature; grounding the block C with a grinder, where the grinder may be a vertical laboratory sand mill, the model of the grinder may be WT0.3, a grinding speed ranges from 1000 to 2000 r/min, and a grinding time ranges from 20 to 48 h; and sieving the block C for a second time to obtain powder D, where meshes for the second sieving range from 300 to 600 meshes.

[0120] Operation (5): sintering the powder D in operation (4) to obtain the above rare earth ytterbium tantalate ceramic powder with different stoichiometric ratios and resisting corrosion of the low melting point oxide, where a sintering temperature ranges from 1700 to 1800° C., a heating rate is 50° C./min, and a sintering time ranges from 5 to 10 h. The obtained powder material can be directly used for spraying to form a thermal barrier coating after granulation.

[0121] When the performance of the ceramic needs to be tested, a bulk structure of the ceramic needs to be obtained, and a pressure treatment is carried out during the sintering in the above operation (5), where a pressure ranges from 200 to 300 MPa, and a pressuring time ranges from 20 to 30 min.

[0122] A ytterbium tantalate ceramic (YbTaO.sub.4 or Yb.sub.3TaO.sub.7) with a density greater than 97% is obtained using the above method. 6 sets of examples are selected to fully illustrate the compactness of the ytterbium tantalate ceramic prepared by the above method.

[0123] Table 4 shows the specific parameters of Examples 13 to 18 of the present disclosure:

TABLE-US-00004 Examples 13 14 15 16 17 18 Yb.sub.2O.sub.3(g) 3.5672 10.7016 3.5672 10.7016 3.5672 10.7016 Ta.sub.2O.sub.5(g) 4.000 4.000 4.000 4.000 4.000 4.000 Ball milling Rotation speed 500 400 300 500 400 450 (r/min) Time (h) 10 20 24 10 20 15 Drying Temperature (° C.) 120 90 50 150 200 100 Time (h) 10 10 24 15 8 18 First sieving Meshes 300 200 300 300 100 200 First Holding pressure 100 200 150 200 100 200 compaction (MPa) Holding pressure 10 12 16 10 20 10 time (min) Pre-sintering Sintering 1000 1100 1200 1150 1200 1100 temperature (° C.) Sintering time (h) 20 15 10 12 10 20 Grinding Rotation speed 2000 1500 1300 1000 1300 1800 (r/min) Time (h) 20 30 40 48 40 25 Second Meshes 600 500 500 600 300 500 sieving Powder Sintering 1800 1700 1750 1780 1790 1700 sintering temperature (° C.) Sintering time (h) 5 10 8 6 6 9 Block Molding pressure 300 300 200 250 200 300 sintering (MPa) Compression time 20 20 30 25 30 20 (min)

[0124] Two sets of control examples are listed and compared with the ytterbium tantalate ceramics obtained in Examples 13-18:

[0125] Control example 3: The difference from Example 13 is that the above operations (3) and (4) are not performed in control example 3.

[0126] Control example 4: The difference from Example 13 is that the sintering temperature in operation (5) ranges from 1200 to 1400° C. in control example 4.

[0127] The ceramic blocks obtained in Examples 13 to 18 and control examples 3 to 4 are now tested:

[0128] 1. XRD Characterization:

[0129] An X-ray diffractometer was used to test the ceramic blocks prepared in Examples 13-18 and control examples 3-4. Take the ytterbium tantalate (YbTaO.sub.4) ceramic block obtained in Example 13 as an example, its XRD pattern is shown in FIG. 6. The diffraction peaks of the ytterbium tantalate (YbTaO.sub.4) ceramic block in FIG. 6 correspond to the standard peaks of the standard PDF card #24-1010, and there is no second-phase diffraction peak, indicating that the prepared sample is a single-phase ytterbium tantalate (YbTaO.sub.4) ceramic, its crystal structure has a monoclinic phase, where α=γ=90° and β=95.7°, and the lattice space group is l2(5). In the meantime, XRD detection shows that the ytterbium tantalate (YbTaO.sub.4) ceramic block has no other impurities.

[0130] 2. SEM Characterization:

[0131] The ceramic blocks prepared in Examples 13 to 18 and control examples 3 to 4 were detected by a scanning electron microscopy. Take the ytterbium tantalate (YbTaO.sub.4) ceramic block prepared in Example 13 as an example, its SEM spectrum is shown in FIG. 7. The SEM spectrum in FIG. 7 shows that the ytterbium tantalate (YbTaO.sub.4) ceramic sample has good crystallization, uniform crystal grain size, and clear grain boundaries, and no second phase is seen within or between the crystal grains, which is consistent with the XRD results. FIG. 7 shows that there are very few cracks and pores in the ytterbium tantalate (YbTaO.sub.4) ceramic block, indicating that the ceramic does not generate excessive pressure and stress during the sintering process, and a density reaches 98.1%.

[0132] The ceramic blocks obtained in control example 3 and control example 4 contain many pores. In particular, the ceramic block obtained in control example 3 contains a certain amount of inclusions (not fully sintered Y.sub.2O.sub.3 and Ta.sub.2O.sub.5 powders) in addition to many pores, making more microcracks appear inside the crystal.

[0133] 3. Density Detection:

[0134] The ceramic blocks prepared in Examples 13 to 18 and control examples 3 to 4 were measured using the Archimedes drainage method. The measurement results are shown in Table 2. It can be seen that the densities of ceramic blocks obtained in Examples 13 to 18 are greater than 97%.

[0135] Table 5 shows the densities of the ceramic blocks prepared in Examples 13 to 18 and control examples 3 to 4.

TABLE-US-00005 Examples Control examples 13 14 15 16 17 18 3 4 Den- 98.1 97.7 97.1 97.4 97.1 97.6 61.3 72.1 sity (%)

[0136] 4. High Temperature Resistance CMAS Corrosion Test:

[0137] 4.1 CMAS Preparation

[0138] After mixing aluminum oxide (Al.sub.2O.sub.3), magnesium oxide (MgO), calcium oxide (CaO), and silicon oxide (SiO.sub.2) in a molar ratio of 15:19:22:44, the mixed oxides were added to distilled water, and ground and mixed in a grinder to obtain a uniform and fine powder, where the speed of the grinder ranges from 1000 to 2000 r/min, and the grinding time ranges from 20 to 48 h. The ground powder was dried at 100-200° C. for 10-20 hours and pre-sintered at 1000-1400° C. for 5-10 hours to obtain a block, and then the block was ground and sieved by a sieve with 300-600 meshes to obtain a uniform CMAS powder.

[0139] The CMAS powder prepared by the above method shows the proportion of CMAS components in the front inlet of the engine turbine when the aero engine works in a harsh environment.

[0140] 4.2 Corrosion Test

[0141] The above CMAS powder was laid on the surface of the ytterbium tantalate ceramic blocks prepared in Examples 13-18, where the amount of CMAS powder was 35 mg/cm2, and then high-temperature sintering was performed at a sintering temperature of 1200-1500° C., a holding-temperature time ranges from 5 to 20 h.

[0142] Take Example 13 as an example, FIG. 8 shows a diagram of the ytterbium tantalate (YbTaO.sub.4) ceramic prepared in Example 13 after holding temperature at 1300° C. for 10 hours in the CMAS high temperature corrosion resistance test. The block with a pie shape in FIG. 8 is the sintered ceramic block, and the particles on the surface of the block are CMAS powder. It can be seen that there is still a large amount of CMAS powder on the surface of each ceramic sample. The melting point of the CMAS powder is lower than 1200° C. After holding temperature for several hours at high temperature (greater than 1200° C.), it shows that the molten CMAS liquid has not reacted with the ceramic material, and it is difficult to penetrate the ceramic material, indicating that CMAS is difficult to react with the rare earth tantalate ceramic material at this temperature, which proves the excellent CMAS corrosion resistance characteristics of ceramic materials. Normally, after other ceramic materials that are not resistant to CMAS corrosion, such as YSZ, are kept at a high temperature for several hours, the molten CMAS liquid reacts with YSZ and penetrates the ceramic, leaving no CMAS powder remaining on the surface.

[0143] 5. Alumina Compatibility

[0144] When a ceramic material is used as a thermal barrier coating on a substrate, it usually needs to be combined with the substrate through an adhesive layer, and the adhesive layer usually contains Al.sub.2O.sub.3. In the present disclosure, the ytterbium tantalate ceramic blocks obtained in Examples 13-18 were mixed with alumina powder and kept at 1200-1500° C. for 7 hours. The obtained ceramic was subjected to XRD detection. Take the ytterbium tantalate (YbTaO.sub.4) ceramic prepared in Example 13 as an example, and its XRD pattern is shown in FIG. 9. It shows that the alumina and ytterbium tantalate did not react, but existed as single-phase alumina and single-phase ytterbium tantalate, respectively. It can be proved that when ytterbium tantalate is used as a thermal barrier coating, it will not react with the alumina in the bonding layer, and has good alumina compatibility and high temperature chemical stability.

[0145] In summary, the ytterbium tantalate (YbTaO.sub.4 or Yb.sub.3TaO.sub.7) ceramics prepared in Examples 13 to 18 have very few microcracks and pores in the crystal structure, resulting in high density, which is above 97%. The ceramics have good corrosion resistance to low melting point oxides. When the temperature reaches 1200-1500° C., the ytterbium tantalate ceramic block hardly reacts with the CMAS powder, and its high temperature CMAS corrosion resistance is much greater than that of YSZ. Besides, when the powder is used as a thermal barrier coating, it will not react with alumina in the bonding layer, and has good alumina compatibility and high temperature chemical stability.

[0146] What has been described above is only an embodiment of the present disclosure, and common knowledge such as specific structures and characteristics that are well-known in the technical solutions are not described here. For those skilled in the art, several modifications and improvements can be made without departing from the structure of the present disclosure. These should also be regarded as the protection scope of the present disclosure, and these will not affect the effects of the implementation and unity of the present disclosure. The protection scope claimed in this application shall be subject to the content of the claims, and the embodiments in the specification can be used to interpret the contents of the claims.