A rare earth orthophosphate ceramic powder, a preparation method and application thereof

Abstract

The application provides a rare earth orthophosphate ceramic powder, a preparation method and application thereof, and belongs to the technical field of ceramic materials. The preparation method of the rare earth orthophosphate ceramic powder comprises the following steps: mixing a rare earth salt solution, a barium salt / strontium salt solution, a phosphorus source solution, a complexing agent and an inorganic solvent to perform a complexing reaction to obtain a sol; drying the sol to obtain a dry gel; and calcining the dry gel to obtain the rare earth orthophosphate ceramic powder. The precursors (the rare earth salt solution, the barium salt / strontium salt solution and the phosphorus source solution) in the form of solutions can be uniformly dispersed at a molecular level, so that the ceramic powder is uniform in size; the sol-gel method is adopted, and the particle size is always kept at the nanometer scale during the sol-gel process, so that the ceramic powder is small in particle size and uniform in distribution.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic materials, and particularly relates to a rare earth orthophosphate ceramic powder and a preparation method and application thereof. BACKGROUND

[0002] Thermal barrier coatings have important and extensive application values in the fields of aerospace, large ships and large thermal power generation. With the continuous increase of the working temperature of engines, the development of new thermal barrier coating materials has become a key issue for the research and development of high-performance aero-engines.

[0003] The rare earth orthophosphate REM3P3O 12 (RE: rare earth element, M: Ba or Sr) has excellent high-temperature stability and extremely low thermal conductivity. In particular, the material of this system has a high thermal expansion coefficient, can realize good thermal matching with a nickel-based alloy, and can greatly relieve the stress generated due to the mismatch of the thermal expansion coefficients of the base material and the ceramic layer, and is considered as a potential candidate material for thermal barrier coatings. However, the rare earth orthophosphate powder is currently mainly synthesized by a solid phase reaction method, which has the disadvantages that the reactivity of each raw material is low, the migration speed is slow, uniform mixing of each raw material at the atomic level cannot be achieved, and the particle size of the synthesized REM3P3O 12 powder is large, resulting in low ceramic density. SUMMARY

[0004] The application aims to provide a rare earth orthophosphate ceramic powder and a preparation method and application thereof. The rare earth orthophosphate ceramic powder prepared by the preparation method provided by the application has small particle size and uniform distribution.

[0005] In order to achieve the above-mentioned application purposes, the application provides the following technical solutions.

[0006] The application provides a preparation method of a rare earth orthophosphate ceramic powder, which comprises the following steps:

[0007] (1) mixing a rare earth salt solution, a barium salt / strontium salt solution, a phosphorus source solution, a complexing agent and an inorganic solvent to perform a complexing reaction, and obtaining a sol;

[0008] (2) drying the sol obtained in the step (1) to obtain a dry gel;

[0009] (3) calcining the dry gel obtained in the step (2) to obtain a rare earth orthophosphate ceramic powder.

[0010] Preferably, the rare earth salt in the step (1) comprises a rare earth chloride salt or a rare earth nitrate salt.

[0011] Preferably, the barium salt in the step (1) comprises barium chloride, barium nitrate or barium acetate; and the strontium salt comprises strontium chloride, strontium nitrate or strontium acetate.

[0012] Preferably, the phosphorus source in the step (1) comprises (NH4)2HPO4 or NH4H2PO4.

[0013] Preferably, the complexing agent in the step (1) is citric acid.

[0014] Preferably, the molar ratio of the rare earth salt, the barium salt / strontium salt, the phosphorus source and the complexing agent in the step (1) is 1:3:3:(3.5-8).

[0015] Preferably, the temperature of the complexing reaction in the step (1) is 80-90℃, and the time of the complexing reaction is 2-8h.

[0016] Preferably, the drying in the step (2) comprises one-stage drying and two-stage drying performed in sequence.

[0017] The present application also provides the rare earth orthophosphate ceramic powder prepared by the preparation method.

[0018] The present application also provides the application of the rare earth orthophosphate ceramic powder in thermal protection coating.

[0019] The present application provides a preparation method of a rare earth orthophosphate ceramic powder, comprising the following steps: mixing a rare earth salt solution, a barium salt / strontium salt solution, a phosphorus source solution, a complexing agent and an inorganic solvent to perform a complexing reaction, so as to obtain a sol; drying the sol to obtain a dry gel; and calcining the dry gel to obtain the rare earth orthophosphate ceramic powder. The present application uses the solution form of the precursors (rare earth salt solution, barium salt / strontium salt solution, phosphorus source solution) to uniformly disperse at the molecular level, so that the ceramic powder size is uniform; and the sol-gel method is adopted, so that the particle size is always kept at the nanometer scale in the sol-gel process, thereby obtaining the ceramic powder with small particle size and uniform distribution. The experimental results show that the average grain size of the rare earth orthophosphate ceramic powder prepared by the preparation method is 13.062-20.357μm. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The XRD graph of the rare earth orthophosphate ceramic powder prepared for Examples 1-7;

[0021] Figure 2 The particle size distribution graph of the rare earth orthophosphate ceramic powder prepared for Example 1;

[0022] Figure 3 The particle size distribution graph of the rare earth orthophosphate ceramic powder prepared for Example 2

[0023] Figure 4 Particle size distribution graph of the rare earth orthophosphate ceramic powder prepared for Example 3;

[0024] Figure 5 Particle size distribution graph of the rare earth orthophosphate ceramic powder prepared for Example 4;

[0025] Figure 6 Particle size distribution graph of the rare earth orthophosphate ceramic powder prepared for Example 5;

[0026] Figure 7 Particle size distribution graph of the rare earth orthophosphate ceramic powder prepared for Example 6;

[0027] Figure 8 Particle size distribution graph of the rare earth orthophosphate ceramic powder prepared for Example 7;

[0028] Figure 9 XRD graph of the rare earth orthophosphate ceramic powder prepared for Comparative Examples 1 to 4. DETAILED DESCRIPTION

[0029] The present application provides a preparation method of a rare earth orthophosphate ceramic powder, comprising the following steps:

[0030] (1) mixing a rare earth salt solution, a barium salt / strontium salt solution, a phosphorus source solution, a complexing agent and an inorganic solvent to perform a complexing reaction, to obtain a sol;

[0031] (2) drying the sol obtained in the step (1) to obtain a xerogel;

[0032] (3) calcining the xerogel obtained in the step (2) to obtain a rare earth orthophosphate ceramic powder.

[0033] The present application does not have special limitation on the source of each raw material, and commercially available products known to those skilled in the art can be used.

[0034] The present application mixes a rare earth salt solution, a barium salt / strontium salt solution, a phosphorus source solution, a complexing agent and an inorganic solvent to perform a complexing reaction, to obtain a sol.

[0035] In the present application, the rare earth salt preferably includes a rare earth chloride or a rare earth nitrate; and the solvent of the rare earth salt solution is preferably deionized water. The present application does not have special limitation on the type of the rare earth, and a rare earth known to those skilled in the art can be used. The present application does not have special limitation on the concentration of the rare earth salt solution, and only a uniform solution is prepared.

[0036] In one embodiment of the present application, the rare earth is yttrium, neodymium, samarium, gadolinium, holmium, erbium or thulium.

[0037] In the present application, the barium salt preferably includes barium chloride, barium nitrate or barium acetate; the strontium salt preferably includes strontium chloride, strontium nitrate or strontium acetate; and the solvent of the barium salt / strontium salt solution is preferably deionized water. The present application does not have a special limitation on the concentration of the barium salt / strontium salt solution, as long as it is prepared into a uniform solution.

[0038] In the present application, the phosphorus source preferably includes (NH4)2HPO4 or NH4H2PO4; and the solvent of the phosphorus source solution is preferably deionized water. The present application does not have a special limitation on the concentration of the phosphorus source solution, as long as it is prepared into a uniform solution.

[0039] In the present application, the complexing agent is preferably citric acid. The present application uses citric acid as the complexing agent, and the use of the citric acid sol-gel method can further reduce the particle size of the ceramic powder.

[0040] In the present application, the inorganic solvent is preferably water, and more preferably deionized water. The present application does not have a special limitation on the amount of the inorganic solvent, as long as the raw materials are dissolved.

[0041] In the present application, the molar ratio of the rare earth salt, the barium salt / strontium salt, the phosphorus source and the complexing agent is preferably 1:3:3:(3.5-8), and more preferably 1:3:3:4, 1:3:3:6 or 1:3:3:8. The present application limits the amount-of-substance ratio of the rare earth salt, the barium salt / strontium salt, the phosphorus source and the complexing agent to the above range, which can improve the degree of complexation reaction.

[0042] In the present application, the mixing of the rare earth salt solution, the barium salt / strontium salt solution, the phosphorus source solution, the complexing agent and the inorganic solvent is preferably as follows:

[0043] 1) mixing the complexing agent with the inorganic solvent to obtain a complexing agent solution;

[0044] 2) simultaneously dropping the rare earth salt solution, the barium salt / strontium salt solution and the phosphorus source solution into the complexing agent solution obtained in step 1).

[0045] The present application preferably mixes the complexing agent with the inorganic solvent to obtain a complexing agent solution. The operation of mixing the complexing agent with the inorganic solvent in the present application does not have a special limitation, and a technical solution for preparing a mixture known to those skilled in the art can be used.

[0046] After obtaining the complexing agent solution, the present application preferably simultaneously drops the rare earth salt solution, the barium salt / strontium salt solution and the phosphorus source solution into the complexing agent solution. The present application uses the dropping method to control the concentration of the solution, prevent the precipitation or agglomeration from causing the phase separation between different components and thus causing the non-uniformity of the microstructure.

[0047] In the present application, the rate of the dropping is preferably 3-5 mL / min, more preferably 4-5 mL / min. The present application limits the rate of the dropping within the above range to further improve the uniformity of the particle size.

[0048] In the present application, the dropping is preferably performed under stirring. The present application does not have a special limitation on the operation of the stirring, and a conventional stirring known to those skilled in the art can be used.

[0049] In the present application, the temperature of the complexing reaction is preferably 80-90°C, and the time of the complexing reaction is preferably 2-8 h. In the present application, the metal cation is subjected to the complexing reaction with the complexing agent, and the temperature and the time of the complexing reaction are limited within the above range to improve the degree of the complexing reaction.

[0050] In the present application, the complexing reaction is preferably performed under stirring. The present application does not have a special limitation on the operation of the stirring, and a conventional stirring known to those skilled in the art can be used.

[0051] After obtaining the sol, the present application dries the sol to obtain a xerogel.

[0052] In the present application, the drying preferably includes one-stage drying and two-stage drying performed in sequence. The temperature of the one-stage drying is preferably 80-90°C, more preferably 80-85°C, the time of the one-stage drying is preferably 20-30 h, more preferably 24-28 h, the temperature of the two-stage drying is preferably 110-130°C, more preferably 120-125°C, and the time of the two-stage drying is preferably 10-20 h, more preferably 15-20 h. The present application uses the way of the two-stage drying, the one-stage drying can remove the residual solvent in the sol, and the two-stage drying can dry the sol into a loose and porous xerogel to prevent the collapse of the gel caused by the excessively high temperature in one-stage heating, and the temperature and the time of the one-stage drying and the two-stage drying are limited within the above range to prevent the structure from being damaged by the serious volume shrinkage of the gel.

[0053] The present application does not have a special limitation on the rate of the temperature increase of the one-stage drying to the temperature of the two-stage drying, and the adjustment can be made as required.

[0054] After obtaining the xerogel, the present application calcines the xerogel to obtain a rare earth orthophosphate ceramic powder.

[0055] In the present application, the xerogel is preferably ground before use. The present application does not have a special limitation on the operation of the grinding, and the loose and porous xerogel can be conventionally ground into a powder using a common mortar.

[0056] In the present application, the calcination temperature is preferably 1000-1200℃, further preferably 1150-1190℃, more preferably 1160-1180℃, and most preferably 1170-1175℃; and the calcination time is preferably 10-20h, and more preferably 15-18h. The present application limits the calcination temperature and time within the above range to ensure the purity of the ceramic powder.

[0057] In the present application, the temperature rising mechanism to the calcination temperature is preferably rising the temperature to 400-500℃ first, and then rising the temperature to the calcination temperature. The present application uses the way of rising the temperature in stages to remove the excessive organic matter in the xerogel.

[0058] In the present application, the rising rate to 400-500℃ is preferably 1-2℃ / min, and more preferably 1℃ / min; and the rising rate to the calcination temperature is preferably 3-5℃ / min, and more preferably 4-5℃ / min. The present application limits the rising rate within the above range to further remove the excessive organic matter in the xerogel.

[0059] After the calcination is completed, the present application preferably cools the product obtained by the calcination to obtain the rare earth orthophosphate ceramic powder.

[0060] The present application does not have special limitation on the cooling operation, and the operation of lowering to room temperature known to those skilled in the art can be used.

[0061] The prior art uses the solid phase reaction method for synthesis, which contains multiple processes of raw material pre-burning, grinding, ball milling and drying, and the preparation process is complicated, which leads to the reduction of purity, and the synthesis needs to be calcined at a high temperature, which requires harsh equipment and has high energy consumption; the preparation method provided by the present application can prepare the REM3P3O 12 The ceramic powder has small particle size and uniform distribution, and the synthesis temperature is relatively low, the operation is simple, easy to control, has small energy consumption, and is easy to mass produce.

[0062] The present application also provides the rare earth orthophosphate ceramic powder prepared by the preparation method of the above technical solution.

[0063] In the present application, the particle size of the rare earth orthophosphate ceramic powder is preferably 10-25μm, and more preferably 13.062-20.357μm; and the particle size distribution is preferably 0.1-150μm, and more preferably 1-100μm. The rare earth orthophosphate REM3P3O 12 The ceramic powder has small particle size and uniform distribution.

[0064] The present application also provides the application of the rare earth orthophosphate ceramic powder of the above technical solution in the thermal protection coating.

[0065] The application has no special limitation on the operation of the rare earth orthophosphate ceramic powder in the application of thermal protection coating, and the application operation known by those skilled in the art can be used.

[0066] The technical solutions in the application will be clearly and completely described below in combination with the embodiments in the application. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0067] Embodiment 1

[0068] The rare earth orthophosphate YBa3P3O 12 The preparation method of the ceramic powder is as follows:

[0069] (1) The raw materials of yttrium nitrate, barium nitrate, ammonium dihydrogen phosphate and citric acid are weighed according to the molar ratio of 1:3:3:4, and then dissolved in deionized water respectively to obtain clear yttrium nitrate solution, barium nitrate solution, ammonium dihydrogen phosphate solution and citric acid solution. Then the yttrium nitrate solution, barium nitrate solution and ammonium dihydrogen phosphate solution are simultaneously added to the citric acid solution at a speed of 3 mL / min, and the complexing reaction is carried out at 80℃ for 5h under stirring to obtain a sol;

[0070] (2) The sol obtained in step (1) is placed in an oven with a temperature of 80℃, and the temperature is kept for 24h, and then the temperature is increased to 120℃, and the temperature is kept for 20h for sufficient drying to obtain a dry gel containing a large number of micropores;

[0071] (3) The dry gel obtained in step (2) is ground into powder, and then placed in a muffle furnace, and the temperature is increased to 400℃ at a rate of 1℃ / min, and the temperature is increased to 1150℃ at a rate of 4℃ / min, and the temperature is kept for 15h for calcination, and then the temperature is decreased to room temperature to obtain YBa3P3O 12 ceramic powder.

[0072] The rare earth orthophosphate ceramic powder prepared in Embodiment 1 is subjected to microscopic detection, and the results are shown in Figure 1 , Figure 1 which is the XRD graph of the rare earth orthophosphate ceramic powder prepared in Embodiment 1.

[0073] It can be seen from Figure 1 that the synthesized ceramic powder is pure YBa3P3O 12 ceramic powder.

[0074] The rare earth orthophosphate ceramic powder prepared in Embodiment 1 is subjected to particle size test analysis, and the results are shown in Figure 2 , Figure 2The particle size distribution diagram of the rare earth orthophosphate ceramic powder prepared in Example 1 is shown in Figure 1.

[0075] From Figure 2 It can be seen that the rare earth orthophosphate ceramic powder prepared in Example 1 has a uniform grain distribution, and the average grain size is calculated to be 15.344 μm.

[0076] Example 2

[0077] The rare earth orthophosphate NdBa3P3O 12 The preparation method of the ceramic powder is as follows:

[0078] (1) The raw materials of neodymium chloride, barium chloride, ammonium dihydrogen phosphate and citric acid are weighed according to the molar ratio of 1:3:3:4, and then dissolved in deionized water respectively to obtain clear neodymium chloride solution, barium chloride solution, ammonium dihydrogen phosphate solution and citric acid solution. Then the neodymium chloride solution, barium chloride solution and ammonium dihydrogen phosphate solution are simultaneously added to the citric acid solution at a speed of 5 mL / min, and a complexing reaction is carried out at 80°C for 5h to obtain a sol;

[0079] (2) The sol obtained in step (1) is placed in an 80°C oven, and heat treated for 24h, and then heated to 125°C and heat treated for 15h for sufficient drying to obtain a dry gel with a porous structure;

[0080] (3) The dry gel obtained in step (2) is ground into powder and placed in a muffle furnace, and heated to 500°C at a rate of 1°C / min and then heated to 1160°C at a rate of 3°C / min, and heat treated for 15h, and then cooled to room temperature to obtain a NdBa3P3O 12 ceramic powder.

[0081] The rare earth orthophosphate ceramic powder prepared in Example 2 is subjected to microscopic detection, and the results are shown in Figure 2. Figure 1 Figure 1 The XRD diagram of the rare earth orthophosphate ceramic powder prepared in Example 2 is shown in Figure 3.

[0082] From Figure 1 It can be seen that the synthesized ceramic powder is a pure phase of NdBa3P3O 12 ceramic powder.

[0083] The rare earth orthophosphate ceramic powder prepared in Example 2 is subjected to particle size test analysis, and the results are shown in Figure 4. Figure 3 Figure 3 The particle size distribution diagram of the rare earth orthophosphate ceramic powder prepared in Example 2 is shown in Figure 5.

[0084] From Figure 3 ​​It can be seen that the rare earth orthophosphate ceramic powder prepared in Example 2 has uniform grain distribution, and the average grain size is calculated to be 13.062 μm.

[0085] Example 3

[0086] The rare earth orthophosphate SmBa3P3O 12 The preparation method of the ceramic powder is as follows:

[0087] (1) The raw materials of samarium chloride, barium chloride, ammonium dihydrogen phosphate and citric acid are weighed according to the molar ratio of 1:3:3:4, and then dissolved in deionized water respectively to obtain clear samarium chloride solution, barium chloride solution, ammonium dihydrogen phosphate solution and citric acid solution. Then the samarium chloride solution, barium chloride solution and ammonium dihydrogen phosphate solution are simultaneously added to the citric acid solution at a speed of 5 mL / min, and a complexing reaction is carried out at 85°C for 3h to obtain a sol;

[0088] (2) The sol obtained in step (1) is placed in an 80°C oven for 24h, and then dried by increasing the temperature to 130°C for 20h to obtain a dry gel with a porous structure;

[0089] (3) The dry gel obtained in step (2) is ground into powder and placed in a muffle furnace, and then heated to 400°C at a rate of 1°C / min and to 1175°C at a rate of 4°C / min, and then kept for 20h to calcine, and then cooled to room temperature to obtain SmBa3P3O 12 ceramic powder.

[0090] The rare earth orthophosphate ceramic powder prepared in Example 3 is subjected to microscopic detection, and the results are shown in Figure 1 , which is the XRD pattern of the rare earth orthophosphate ceramic powder prepared in Example 3. Figure 1 It can be seen from

[0091] that the synthesized ceramic powder is pure SmBa3P3O 12 ceramic powder. Figure 1 The rare earth orthophosphate ceramic powder prepared in Example 3 is subjected to particle size test analysis, and the results are shown in

[0092] , which is the particle size distribution graph of the rare earth orthophosphate ceramic powder prepared in Example 3. Figure 4 Figure 4 It can be seen from that the rare earth orthophosphate ceramic powder prepared in Example 3 has uniform grain distribution, and the average grain size is calculated to be 13.343 μm.

[0093] Figure 4 Example 4

[0094] Example 3

[0095] ​A rare earth orthophosphate GdBa3P3O 12 The preparation method of the ceramic powder comprises the following steps:

[0096] (1) The raw materials of gadolinium chloride, barium nitrate, ammonium dihydrogen phosphate and citric acid are weighed according to the molar ratio of 1:3:3:8, and then dissolved in deionized water respectively to obtain clear gadolinium chloride solution, barium nitrate solution, ammonium dihydrogen phosphate solution and citric acid solution; the gadolinium chloride solution, the barium nitrate solution and the ammonium dihydrogen phosphate solution are simultaneously added into the citric acid solution at a speed of 5 mL / min to perform complexation reaction at 90℃ for 2h to obtain a sol;

[0097] (2) The sol obtained in step (1) is placed into an oven at 80℃ for 24h, and then heated to 130℃ for 15h to perform sufficient drying to obtain a dry gel with a porous structure;

[0098] (3) The dry gel obtained in step (2) is ground into powder, and then heated to 500℃ at a speed of 1℃ / min and to 1160℃ at a speed of 5℃ / min in a muffle furnace, and then kept for 20h to perform calcination, and then cooled to room temperature to obtain a rare earth orthophosphate GdBa3P3O 12 ceramic powder.

[0099] The rare earth orthophosphate ceramic powder prepared in Example 4 is subjected to microscopic detection, and the result is shown in Figure 1 , wherein Figure 1 is an XRD graph of the rare earth orthophosphate ceramic powder prepared in Example 4.

[0100] It can be seen from Figure 1 that the synthesized ceramic powder is a pure-phase GdBa3P3O 12 ceramic powder.

[0101] The rare earth orthophosphate ceramic powder prepared in Example 4 is subjected to particle size test analysis, and the result is shown in Figure 5 , wherein Figure 5 is a particle size distribution graph of the rare earth orthophosphate ceramic powder prepared in Example 4.

[0102] It can be seen from Figure 5 that the rare earth orthophosphate ceramic powder prepared in Example 4 has uniform crystal grain distribution, and the average size of the crystal grains is calculated to be 13.951μm.

[0103] Example 5

[0104] A rare earth orthophosphate HoBa3P3O 12 The preparation method of the ceramic powder comprises the following steps:

[0105] (1) HoCl3, Ba (CH3COO) 2, NH4H2PO4 and citric acid were weighed according to the molar ratio of 1:3:3:6, and then dissolved in deionized water respectively to obtain clear HoCl3 solution, Ba (CH3COO) 2 solution, NH4H2PO4 solution and citric acid solution. Then the HoCl3 solution, Ba (CH3COO) 2 solution and NH4H2PO4 solution were simultaneously added into the citric acid solution at a speed of 5 mL / min, and a complexation reaction was carried out at 90℃ for 3h under stirring to obtain a sol;

[0106] (2) The sol obtained in step (1) was placed in an oven at 80℃ for 24h, and then dried at 120℃ for 10h to obtain a xerogel with a porous structure;

[0107] (3) The xerogel obtained in step (2) was ground into powder, and then calcined in a muffle furnace at a temperature increasing rate of 1℃ / min to 400℃ and then 5℃ / min to 1180℃, and then kept at 1180℃ for 10h. After that, the temperature was decreased to room temperature to obtain HoBa3P3O 12 ceramic powder.

[0108] The rare earth orthophosphate ceramic powder prepared in Example 5 was subjected to microscopic detection, and the results are shown in Figure 1 , wherein Figure 1 is the XRD pattern of the rare earth orthophosphate ceramic powder prepared in Example 5.

[0109] It can be seen from Figure 5 that the synthesized ceramic powder is pure HoBa3P3O 12 ceramic powder.

[0110] The rare earth orthophosphate ceramic powder prepared in Example 5 was subjected to particle size test analysis, and the results are shown in Figure 6 , wherein Figure 6 is the particle size distribution graph of the rare earth orthophosphate ceramic powder prepared in Example 5.

[0111] It can be seen from Figure 6 that the rare earth orthophosphate ceramic powder prepared in Example 5 has uniform crystal grain distribution, and the average crystal grain size is calculated to be 17.434μm.

[0112] Example 6

[0113] A preparation method of a rare earth orthophosphate ErBa3P3O 12 ceramic powder is as follows:

[0114] (1) The raw materials were weighed according to the molar ratio of 1:3:3:4 of erbium chloride, barium chloride, ammonium dihydrogen phosphate and citric acid, and then dissolved in deionized water respectively to obtain clear solutions of erbium chloride, barium chloride, ammonium dihydrogen phosphate and citric acid. The solutions of erbium chloride, barium chloride and ammonium dihydrogen phosphate were simultaneously added to the citric acid solution at a speed of 5 mL / min, and a complexation reaction was carried out at 85℃ for 3h under stirring to obtain a sol;

[0115] (2) The sol obtained in step (1) was placed in an oven at 80℃ for 24h, and then dried at 120℃ for 15h to obtain a xerogel with a porous structure;

[0116] (3) The xerogel obtained in step (2) was ground into powder, and then calcined in a muffle furnace at a temperature rising rate of 1℃ / min to 400℃ and 5℃ / min to 1170℃, and then kept at 1170℃ for 15h. After cooling to room temperature, an ErBa3P3O 12 ceramic powder.

[0117] The rare earth orthophosphate ceramic powder prepared in Example 6 was subjected to microscopic detection, and the results are shown in Figure 1 , Figure 1 which is the XRD pattern of the rare earth orthophosphate ceramic powder prepared in Example 6.

[0118] It can be seen from Figure 1 that the synthesized ceramic powder is pure phase ErBa3P3O 12 ceramic powder.

[0119] The rare earth orthophosphate ceramic powder prepared in Example 6 was subjected to particle size test analysis, and the results are shown in Figure 7 , Figure 7 which is the particle size distribution graph of the rare earth orthophosphate ceramic powder prepared in Example 6.

[0120] It can be seen from Figure 7 that the rare earth orthophosphate ceramic powder prepared in Example 6 has uniform crystal grain distribution, and the average crystal grain size is calculated to be 20.357μm.

[0121] Example 7

[0122] A preparation method of a rare earth orthophosphate TmBa3P3O 12 ceramic powder is as follows:

[0123] (1) The raw materials were weighed according to the molar ratio of thulium chloride, barium acetate, ammonium dihydrogen phosphate and citric acid as 1:3:3:4, and then dissolved in deionized water respectively to obtain clear thulium chloride solution, barium acetate solution, ammonium dihydrogen phosphate solution and citric acid solution. Then the thulium chloride solution, barium acetate solution and ammonium dihydrogen phosphate solution were simultaneously added to the citric acid solution at a speed of 5 mL / min, and a complexing reaction was carried out at 85°C for 4h to obtain a sol;

[0124] (2) The sol obtained in step (1) was placed in an oven at 80°C and kept for 24h, and then the temperature was raised to 120°C and kept for 20h for sufficient drying to obtain a dry gel with a porous structure;

[0125] (3) The dry gel obtained in step (2) was ground into powder and placed in a muffle furnace, and the temperature was raised to 400°C at a rate of 1°C / min and then to 1190°C at a rate of 5°C / min, and kept for 20h for calcination, and then the temperature was lowered to room temperature to obtain TmBa3P3O 12 ceramic powder.

[0126] The rare earth orthophosphate ceramic powder prepared in Example 7 was subjected to microscopic detection, and the results are shown in Figure 1 , wherein Figure 1 is the XRD pattern of the rare earth orthophosphate ceramic powder prepared in Example 7.

[0127] It can be seen from Figure 1 that the synthesized ceramic powder is pure-phase TmBa3P3O 12 ceramic powder.

[0128] The rare earth orthophosphate ceramic powder prepared in Example 7 was subjected to particle size test analysis, and the results are shown in Figure 8 , wherein Figure 8 is the particle size distribution graph of the rare earth orthophosphate ceramic powder prepared in Example 7.

[0129] It can be seen from Figure 8 that the rare earth orthophosphate ceramic powder prepared in Example 7 has uniform crystal grain distribution, and the average crystal grain size is calculated to be 20.037μm.

[0130] Comparative Example 1

[0131] The calcination condition of step (3) in Example 1 was changed to keeping at 800°C for 20h, and other conditions remained unchanged to obtain YBa3P3O 12 ceramic powder.

[0132] The rare earth orthophosphate ceramic powder prepared in Comparative Example 1 was subjected to microscopic detection, and the results are shown in Figure 9 , wherein Figure 9 is the XRD pattern of the rare earth orthophosphate ceramic powder prepared in Comparative Example 1.

[0133] From Figure 9 it can be seen that pure phase of YBa3P3O 12 is not obtained under this calcination condition.

[0134] Comparative Example 2

[0135] The calcination condition of step (3) in Example 2 was changed to heat preservation at 850℃ for 20h, and other conditions were unchanged, to obtain NdBa3P3O 12 ceramic powder.

[0136] The rare earth orthophosphate ceramic powder prepared in Comparative Example 2 was subjected to microscopic detection, and the results are shown in Figure 9 , and Figure 9 is the XRD pattern of the rare earth orthophosphate ceramic powder prepared in Comparative Example 2.

[0137] From Figure 9 it can be seen that pure phase of NdBa3P3O 12 is not obtained under this calcination condition.

[0138] Comparative Example 3

[0139] The calcination condition of step (3) in Example 3 was changed to heat preservation at 900℃ for 20h, and other conditions were unchanged, to obtain SmBa3P3O 12 ceramic powder.

[0140] The rare earth orthophosphate ceramic powder prepared in Comparative Example 3 was subjected to microscopic detection, and the results are shown in Figure 9 , and Figure 9 is the XRD pattern of the rare earth orthophosphate ceramic powder prepared in Comparative Example 3.

[0141] From Figure 9 it can be seen that pure phase of SmBa3P3O 12 is not obtained under this calcination condition.

[0142] Comparative Example 4

[0143] The calcination condition of step (3) in Example 4 was changed to heat preservation at 950℃ for 20h, and other conditions were unchanged, to obtain GdBa3P3O 12 ceramic powder.

[0144] The rare earth orthophosphate ceramic powder prepared in Comparative Example 4 was subjected to microscopic detection, and the results are shown in Figure 9 , and Figure 9 is the XRD pattern of the rare earth orthophosphate ceramic powder prepared in Comparative Example 4.

[0145] From Figure 9 it can be seen that pure phase of GdBa3P3O12 Phase.

[0146] From the above examples and comparative examples, it can be seen that the rare earth orthophosphate ceramic powder provided by the present application has small particle size and uniform distribution.

[0147] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing rare earth orthophosphate ceramic powder, comprising the following steps: (1) Mix rare earth salt solution, barium salt / strontium salt solution, phosphorus source solution, complexing agent and inorganic solvent, and carry out complexation reaction to obtain sol; (2) The sol obtained in step (1) is dried to obtain a dry gel; (3) The dry gel obtained in step (2) is calcined to obtain rare earth orthophosphate ceramic powder; the calcination temperature is 1000~1200℃; the calcination time is 10~20h; The complexing agent in step (1) is citric acid; In step (1), the molar ratio of rare earth salt, barium salt / strontium salt, phosphorus source and complexing agent is 1:3:3:(3.5~8). The drying in step (2) includes a first-stage drying and a second-stage drying performed sequentially; The temperature of the first drying stage is 80~90℃; the drying time of the first drying stage is 20~30h; The temperature of the two-stage drying is 110~130℃; the drying time of the two-stage drying is 10~20h.

2. The preparation method according to claim 1, characterized in that, The rare earth salts in step (1) include rare earth chlorides or rare earth nitrates.

3. The preparation method according to claim 1, characterized in that, The barium salt in step (1) includes barium chloride, barium nitrate, or barium acetate; the strontium salt includes strontium chloride, strontium nitrate, or strontium acetate.

4. The preparation method according to claim 1, characterized in that, The phosphorus source in step (1) includes (NH4)2HPO4 or NH4H2PO4.

5. The preparation method according to claim 1, characterized in that, The temperature of the complexation reaction in step (1) is 80~90℃, and the time of the complexation reaction is 2~8h.

6. Rare earth orthophosphate ceramic powder prepared by the preparation method according to any one of claims 1 to 5.

7. The application of the rare earth orthophosphate ceramic powder of claim 6 in thermal protective coatings.

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