Preparation method of monazite structure high-entropy phosphate ceramic powder

Abstract

The application relates to a preparation method of a xenotime-structure high-entropy phosphate ceramic powder, and belongs to the technical field of high-entropy phosphate ceramic preparation. The xenotime-structure high-entropy phosphate ceramic powder prepared by the method has good high-temperature phase stability, the preparation method is simple and efficient, the cost is low, the safety is good, the purity is high, can be used as a candidate system of high-temperature protection materials for more severe service environments, the particle size of the oxide raw material is reduced through the high-energy ball milling mode, the overall surface energy is increased, sintering densification is promoted, and the preparation cost is reduced, so that the material preparation period is greatly shortened.

Description

Technical Field

[0001] This invention relates to the field of high-entropy phosphate ceramics preparation technology, specifically to a method for preparing high-entropy phosphate ceramic powder with a xenotime structure. Background Technology

[0002] Currently, research findings on high-entropy ceramics have greatly contributed to the performance regulation and application of inorganic solid solution materials. On the one hand, compared with the simple FCC, BCC, and HCP structures of metallic materials, the crystal structures of high-entropy ceramics are more diverse and complex; on the other hand, the diverse structures of high-entropy ceramics, combined with different chemical bonds in metallic materials, endow high-entropy ceramic materials with unique properties.

[0003] Currently, most methods for preparing multi-component high-entropy ceramics (high-entropy phosphates) employ liquid-phase co-precipitation. However, due to variations in the precipitant, the prepared powders often exhibit problems such as excessively large particle size, uneven particle size distribution, and difficulty in grinding after drying due to agglomeration. Furthermore, the preparation cost is too high, and the stoichiometric ratio deviates from the original proportions, failing to meet the uniformity, accuracy, and repeatability requirements for high-entropy ceramic preparation. The complex preparation process, hazardous raw materials and reagents, difficulty in controlling byproduct impurities, difficulty in controlling the morphology of the product powder, and high reagent costs limit its application to the preparation of simple-component phosphates. In terms of performance, the thermal conductivity of traditional single-component rare-earth xenotime phosphates at high temperatures is typically between 4 and 10 W·m. -1 ·K -1 It has poor heat insulation performance.

[0004] The existing high-entropy design approach involves introducing other ions with significantly different sizes, causing ion mismatch and resulting in lattice distortion. Under thermal conditions, when heat-transferring phonons are conducted in a solid solution with lattice distortion, the scattering rate increases significantly, but the thermal conductivity decreases significantly. Summary of the Invention

[0005] In view of the above problems, the present invention provides a method for preparing high-entropy phosphate ceramic powder with xenotime structure. The present invention uses accurately weighed rare earth oxides to directly react with phosphoric acid to prepare phosphate powder, which greatly simplifies the process steps, allows for the preparation of a large number of samples in one go, and produces powder with small and uniform particle size, good dispersion, and no consolidation. This solves the problems of high cost, poor uniformity, and poor powder morphology of existing preparation methods. Furthermore, the prepared high-entropy ceramic powder has relatively low thermal conductivity, which is beneficial for its application in the field of high-temperature protection.

[0006] This invention provides a method for preparing high-entropy phosphate ceramic powder with a xenotime structure, comprising:

[0007] S1. Weigh and mix various rare earth oxide raw materials to obtain rare earth oxide mixed raw materials. Remove the moisture and impurities from the rare earth oxide mixed raw materials to obtain rare earth oxide mixed powder.

[0008] S2. The rare earth oxide mixed powder is dried and refined, and then mixed to obtain the treated rare earth oxide mixed powder.

[0009] S3. Prepare a phosphoric acid stabilizer, and disperse the phosphoric acid stabilizer with the treated rare earth oxide mixed powder to obtain a dispersed rare earth oxide mixed powder.

[0010] S4. The dispersed rare earth oxide mixed powder is washed and dried to obtain raw material;

[0011] S5. The raw material is subjected to heat treatment and atmospheric pressure sintering to obtain a high-entropy phosphate ceramic material with a xenotime structure.

[0012] Preferably, all of the rare earth oxide raw materials are rare earth oxide raw materials with a yttrium phosphate structure.

[0013] Preferably, in step S1, the rare earth oxide mixture is calcined to remove moisture and impurities; the calcination temperature is 850℃~950℃, and the calcination holding time is 2h~4h.

[0014] Preferably, the rare earth oxide raw materials mentioned in step S1 include five rare earth oxide raw materials, including any four or more of Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Y2O3 and Lu2O3 in raw material one;

[0015] La2O3 and Pr6O in raw material 2 11 At most one of Nd2O3, Sm2O3, Eu2O3 and Gd2O3;

[0016] The difference between the ionic radii of rare earth elements in raw material two is greater than the difference between the ionic radii of rare earth elements in raw material one.

[0017] Furthermore, the five rare earth oxide raw materials include any four of the following from raw material one: Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Y2O3, or Lu2O3.

[0018] La2O3 and Pr6O in raw material 2 11 Nd₂O₃, Sm₂O₃, Eu₂O₃ and Gd₂O 32 Any one of them.

[0019] Preferably, the molar mass ratio of rare earth elements in the five rare earth oxide raw materials is 1:1:

[0020] 1:1:1.

[0021] This invention uses at least four rare earth oxide raw materials to prepare high-entropy phosphate powder with a single-phase structure of xenotime, ensuring that the high-entropy structure can be formed in the form of a solid solution. Five rare earth oxides with xenotime structure are used as the structural framework. The structural framework obtained by this invention has a high configurational entropy value, and the product of its value and temperature offsets the increase in enthalpy. At the same time, the Gibbs free energy is negative, realizing spontaneous reaction. When the temperature is very high, the high-entropy material can actually have good phase stability.

[0022] The preparation method of this invention increases the variety of rare earth oxide raw materials and weighs the raw materials in an equimolar ratio, which ensures the phase purity of the product, realizes the controllability of the composition, and avoids the deviation of the composition ratio when weighing raw materials in the prior art.

[0023] Preferably, the specific steps of refining in step S2 are as follows: the mixed powder is subjected to high-energy ball milling to refine the powder in the mixed powder to submicron or nano-sized particles;

[0024] The high-energy ball milling uses agate balls as the grinding medium; ethanol or deionized water is used as the dispersant; and a planetary ball mill is used for ball milling.

[0025] The planetary ball mill has a ball-to-material ratio of (8-10):1, and the grinding balls are divided into three sizes: 1mm diameter, 2mm diameter, and 4mm diameter. The three sizes of grinding balls are mixed in a ratio of 5:3:2.

[0026] Furthermore, the high-energy ball mill has a rotation speed of 350-450 r / min and an effective ball milling time of 16-24 h. The planetary ball mill stops for 10 minutes every 20 minutes of grinding and then continues to work in the opposite direction.

[0027] Preferably, the drying environment in step S2 is: atmospheric pressure drying temperature of 60-80℃, and drying time of at least 12 hours.

[0028] Preferably, the preparation of the phosphoric acid stabilizer in step S3 specifically includes the following steps:

[0029] Taking rare earth oxide raw material RE2O3 as an example, according to the molar mass ratio of phosphoric acid to rare earth oxide (RE2O3) of H3PO4:RE2O3=(2.5~3.5):1, the phosphoric acid is weighed.

[0030] The weighed phosphoric acid was diluted with deionized water to obtain a phosphoric acid stabilizer.

[0031] The volume ratio of the weighed phosphoric acid to deionized water is 1:(4-7).

[0032] The phosphoric acid stabilizer prepared in this invention uses diluted phosphoric acid, which further increases the liquid volume, allowing the treated rare earth oxide powder to be fully dispersed by magnetic stirring after being added to the phosphoric acid stabilizer.

[0033] Preferably, the dispersion reaction in step S3 is as follows: the phosphoric acid stabilizer is thoroughly mixed with the treated rare earth oxide mixed powder and stirred continuously at a constant temperature;

[0034] Specifically, the treated rare earth oxide mixed powder is added to the phosphoric acid stabilizer at a rate of 0.05 to 0.2 g / s, and the temperature of the constant temperature magnetic stirring is 40℃ to 80℃; the speed of magnetic stirring is 400 to 600 r / min; and the stirring time is 12h to 24h to obtain the dispersed rare earth oxide mixed powder.

[0035] This invention involves a phosphoric acid stabilizer reacting with treated rare earth oxide powder to increase the overall configuration entropy of the solid solution in the obtained structural framework.

[0036] The structural framework contains multiple elements with differences in ionic radii. These differences exist at equivalent cation sites. The lattice distortion effect is used to reconcile these differences, causing distortion in the lengths and angles of the interconnected chemical bonds. This results in a high-entropy effect, which significantly reduces the chemical diffusion rate. Consequently, the phase transition requires overcoming a greater energy barrier, thereby enhancing the system's high-temperature stability.

[0037] The present invention uses a liquid phase + solid phase raw material preparation method to ensure that the rare earth oxides are fully and uniformly dispersed during the reaction process, and the resulting powder has uniform composition and small particle size.

[0038] Preferably, the washing and drying in step S4 involves centrifuging the dispersed rare earth oxide mixed powder with deionized water and ethanol, and then drying it thoroughly in a forced-air drying oven under normal pressure to obtain raw material;

[0039] Furthermore, the washing steps include:

[0040] S41. The treated rare earth oxide mixed powder is centrifuged for the first time using deionized water and ethanol. After separation, all liquid is poured out. Deionized water is added to the centrifuged powder. The centrifuged powder is stirred evenly and dispersed in the deionized water. The pH value of the mixture is tested.

[0041] S42. Centrifuge the mixture a second time, test the pH value of the supernatant after separation, and pour out all the supernatant. Add deionized water to the powder after the second centrifugation, stir the powder evenly and disperse it in the deionized water to obtain a secondary mixture, and test the pH value of the secondary mixture.

[0042] S43. Repeat step S42 for N centrifugation until the pH of the supernatant after the Nth centrifugation is neutral. When the pH of the supernatant after the Nth centrifugation is neutral, pour out all the supernatant and add anhydrous ethanol. Stir the powder after the Nth centrifugation evenly and disperse it in anhydrous ethanol to obtain the Nth mixture.

[0043] S44. Centrifuge the Nth mixture for the N+1th time. After separation, pour out all the liquid and add anhydrous ethanol. Stir the powder after the N+1th centrifugation evenly and disperse it in anhydrous ethanol. Place it in a beaker and dry it to obtain raw material. The drying environment is the same as in step S2.

[0044] Preferably, the heat treatment time in step S5 is 2 to 5 hours, and the heat treatment temperature is 850°C to 1050°C; the heat treatment removes free water, crystal water and impurities.

[0045] Preferably, in step S5, sintering is carried out according to the heating and cooling regimes of sintering; sintering is carried out at 1400℃~1600℃ and then held for 4~10 hours before cooling.

[0046] Furthermore, the sintering temperature rise regime is as follows:

[0047] The temperature was increased at a rate of 5℃ / min in the range of room temperature to 1200℃.

[0048] The temperature range of 1200℃ to 1500℃ is increased at a rate of 2℃ / min;

[0049] The temperature range of 1500℃ to 1600℃ is increased at a rate of 2℃ / min.

[0050] The cooling process for sintering is as follows:

[0051] The temperature range of 1500℃ to 1600℃ is reduced at a rate of 2℃ / min.

[0052] The temperature range of 1200℃ to 1500℃ is reduced at a rate of 2℃ / min.

[0053] For the 500℃~1200℃ range, the temperature is reduced at a rate of 5℃ / min;

[0054] It is cooled along with the furnace when the temperature drops to 500℃.

[0055] This invention establishes a heating and cooling regime for sintering. The temperature is increased at a relatively rapid rate before reaching 1200 degrees Celsius; in the intermediate temperature range of 1200 to 1500 degrees Celsius, the ceramic sample shrinks slowly, accompanied by the removal of impurities, and the heating rate is moderate; in the stage of 1500-1600 degrees Celsius, the ceramic block undergoes significant shrinkage during sintering, hence the heating rate is slower. This heating regime saves time and provides sufficient energy for each stage of ceramic block sintering, which is beneficial for the removal of pores and the densification of the block. Compared with the prior art, this invention has at least the following beneficial effects:

[0056] (1) The high-entropy phosphate ceramic powder with yttrium phosphate structure prepared by the technical solution of the present invention has good high-temperature phase stability. At the same time, the preparation method is simple and efficient, with low cost, good safety and high purity. Compared with low-entropy materials, the lattice distortion effect and high-entropy value effect of the high-entropy system enable the solid solution to maintain a single-phase structure at high temperature, which has good phase stability. Furthermore, due to the scattering of phonons by the lattice distortion effect, the thermal conductivity is further reduced.

[0057] (2) The present invention uses high-energy ball milling to fully mix various oxide raw materials and further reduce the particle size. During the solution reaction process, the product powder also has the characteristics of uniform mixing of multiple elements and small particle size, which increases the overall surface energy, thereby promoting sintering densification and reducing the preparation cost, and greatly shortening the material preparation cycle.

[0058] (3) The high-entropy phosphate ceramic material prepared by the present invention has high phase purity and uniform element distribution. It can maintain phase stability after heat treatment at high temperature (1500℃) and can be used as a candidate system for high-temperature protection materials for more severe service environments. Attached Figure Description

[0059] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0060] Figure 1 This is a schematic diagram comparing the X-ray diffraction pattern of the high-entropy phosphate ceramic with xenotime structure of Embodiment 1 of the present invention with a standard PDF card.

[0061] Figure 2 This is a scanning electron microscope image of the high-entropy phosphate ceramic powder with a xenotime structure according to Example 1 of the present invention, and a schematic diagram of the corresponding region's energy dispersive spectroscopy (EDS) elemental surface analysis results.

[0062] Figure 3 This is a schematic diagram of the simultaneous thermal analysis curve of the high-entropy phosphate ceramic with a xenotime structure according to Example 1 of the present invention. Detailed Implementation

[0063] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0064] A specific embodiment of the present invention, such as Figure 1-3 This invention discloses a method for preparing high-entropy phosphate powder with a xenotime structure. To illustrate the effectiveness of the method proposed in this invention, a specific embodiment is provided below for detailed explanation of the above-mentioned technical solution. The specific implementation steps are as follows:

[0065] Example 1:

[0066] (Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 The preparation method of high-entropy phosphate powder with xenotime structure (PO4) includes the following steps:

[0067] (1) Impurity removal: The required Dy2O3, Ho2O3, Er2O3, Tm2O3 and Yb2O3 powders were calcined in a muffle furnace at 850℃ to remove moisture and impurities;

[0068] (2) Weighing raw materials: Weigh 0.9325g of Dy2O3, 0.9447g of Ho2O3, 0.9574g of Er2O3, 0.9646g of Tm2O3, and 0.9850g of Yb2O3 powder according to the molar ratio of rare earth ions 1:1:1:1:1, for a total of 4.7842g of powder. Weigh 0.7349g of liquid phosphoric acid according to the molar ratio of H3PO4:RE2O3 = 3:1 and dilute it in a beaker. Mix it with deionized water at a volume ratio of H3PO4:deionized water = 1:4 to obtain a phosphoric acid solution.

[0069] (3) Mixing and refining: The accurately weighed Dy2O3, Ho2O3, Er2O3, Tm2O3, and Yb2O3 powders were mixed and then subjected to high-energy ball milling. Agate balls were used as the grinding medium and ethanol was used as the dispersant. The ball-to-powder ratio was 8:1, and the grinding balls were divided into three sizes: 1 mm, 2 mm, and 4 mm in diameter. The three sizes of grinding balls were mixed in a ratio of 5:3:2. In addition, the ball mill speed was 350 r / min, and the effective ball milling time was 16 h. The planetary ball mill stopped for 10 min every 20 min of grinding, and then continued to work in the opposite direction. After repeated grinding, the machine was stopped to obtain a slurry in which all components were mixed evenly. The mixed slurry was transferred into a beaker and placed in a forced-air drying oven to dry at 60 °C for 16 h.

[0070] (4) Dispersion reaction: The diluted phosphoric acid solution and rare earth oxide powder are thoroughly mixed and continuously stirred at a constant temperature; the dried mixed oxide powder is added to the prepared phosphoric acid solution at a rate of 0.1 g / s, the temperature of the magnetic stirring is 40℃, the speed of the magnetic stirring is 500 r / min, and the stirring time is 16 h.

[0071] (5) Washing and drying: After the reaction is completed, the powder is separated from the acid by centrifugation. The washing steps are as follows: After the first centrifugation, all liquid is poured out and deionized water is added. The powder is stirred and dispersed evenly in the deionized water. The pH of the mixture is tested to be approximately 1. After the second centrifugation, the pH of the supernatant is tested to be approximately 2. All acidic liquid is poured out and deionized water is added. The powder is stirred and dispersed evenly in the deionized water. This step is repeated twice until the pH is neutral. After the fifth centrifugation, the pH of the supernatant is still neutral. All liquid is poured out and anhydrous ethanol is added to the same volume. The powder is stirred and dispersed evenly in the anhydrous ethanol and centrifuged again. After the sixth centrifugation, all liquid is poured out and anhydrous ethanol is added. The powder is stirred and dispersed evenly in the anhydrous ethanol, placed in a beaker and dried. The drying temperature is 60℃ and the drying time is 16h.

[0072] (6) Heat treatment and sintering: The raw material after step S5 is heat treated and sintered at atmospheric pressure to obtain a high-entropy phosphate ceramic material with a xenotime structure; the heat treatment time of the powder after reaction is 2 hours and the heat treatment temperature is 850℃ to remove free water, crystal water and impurities; the heat-treated powder sample is placed in a high-temperature furnace for sintering to further densify and improve crystallinity. The sintering temperature of the powder ceramic is selected as 1400℃ and held for 4 hours; the sintering heating regime is as follows: heating at 5℃ / min in the range of room temperature to 1200℃; heating at 2℃ / min in the range of 1200℃ to 1400℃; the sintering cooling regime is as follows: cooling at 2℃ / min in the range of 1200℃ to 1400℃; cooling at 5℃ / min in the range of 500℃ to 1200℃; and cooling with the furnace when the temperature drops to 500℃.

[0073] Figure 1 For (Dy) after heat treatment at 850℃ 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 The XRD results of the high-entropy phosphate powder of PO4 showed that its crystal structure was consistent with that of YPO4 with xenotime mineral structure. No second-phase diffraction peaks or diffraction peaks of impurities or oxide raw materials were found, which reflects that the phase purity of the high-entropy phosphate powder prepared in this embodiment is good. In this embodiment, any number of the five rare earth oxide components can also be replaced by any number of the corresponding components of Tb4O7, Y2O3, and Lu2O3.

[0074] Figure 2 (Dy) after heat treatment at 850℃ 0.2 Ho 0.2 Er 0.2 Tm 0.2 Yb 0.2 The microstructure of the high-entropy phosphate powder and the corresponding EDS elemental analysis results are shown. The powder particles are spherical and composed of nanoscale plate-like particles. The five rare earth elements, as well as phosphorus and oxygen, are evenly distributed in the powder without elemental segregation. This indicates that the high-entropy phosphate powder prepared in this example has a small particle size, a large specific surface area, and uniform dispersion of the rare earth elements, forming a single-phase high-entropy ceramic solid solution.

[0075] Example 2:

[0076] (Gd 0.2 Dy 0.2 Ho 0.2 Er 0.2 Tm 0.2 The preparation method of high-entropy phosphate powder with xenotime structure (PO4) includes the following steps:

[0077] (1) Impurity removal: The required Gd2O3, Dy2O3, Ho2O3, Er2O3 and Tm2O3 powders were calcined in a muffle furnace at 900℃ to remove moisture and impurities;

[0078] (2) Weighing raw materials: Weigh 0.9050g of Gd2O3, 0.9325g of Dy2O3, 0.9447g of Ho2O3, 0.9574g of Er2O3, and 0.9646g of Tm2O3 powder according to the molar ratio of rare earth ions 1:1:1:1:1, for a total of 4.7369g of powder. Weigh 0.8574g of liquid phosphoric acid according to the molar ratio of H3PO4:RE2O3 = 3.5:1 and dilute it in a beaker. Mix it with deionized water at a volume ratio of H3PO4:deionized water = 1:6 to obtain a phosphoric acid solution.

[0079] (3) Mixing and refining: The accurately weighed Gd2O3, Dy2O3, Ho2O3, Er2O3, and Tm2O3 powders were mixed and then subjected to high-energy ball milling. Agate balls were used as the grinding medium and ethanol was used as the dispersant. The ball-to-material ratio was 9:1, and the grinding balls were divided into three sizes: 1 mm, 2 mm, and 4 mm in diameter. The three sizes of grinding balls were mixed in a ratio of 5:3:2. In addition, the ball mill speed was 400 r / min, and the effective ball milling time was 20 h. The planetary ball mill stopped for 10 min every 20 min of grinding and then continued to work in the opposite direction. After repeated grinding, the machine was stopped to obtain a slurry in which all components were mixed evenly. The mixed slurry was transferred into a beaker and placed in a forced-air drying oven to dry at 70 °C for 12 h.

[0080] (4) Dispersion reaction: The diluted phosphoric acid solution and rare earth oxide powder are thoroughly mixed and continuously stirred at a constant temperature; the dried mixed oxide powder is added to the prepared phosphoric acid solution at a rate of 0.05 g / s, the temperature of the magnetic stirring is 50℃, the speed of the magnetic stirring is 600 r / min, and the stirring time is 12 h.

[0081] (5) Washing and drying: After the reaction is completed, the powder is separated from the acid by centrifugation. The washing steps are as follows: After the first centrifugation, all liquids are poured out and deionized water is added. The powder is stirred and dispersed evenly in the deionized water. The pH of the mixture is tested to be approximately 1. After the second centrifugation, the pH of the supernatant is tested to be approximately 1.5. All acidic liquids are poured out and deionized water is added. The powder is stirred and dispersed evenly in the deionized water. This step is repeated 3 times until the pH is neutral. After the sixth centrifugation, the pH of the supernatant is still neutral. All liquids are poured out and anhydrous ethanol is added to the same volume. The powder is stirred and dispersed evenly in the anhydrous ethanol and centrifuged again. After the seventh centrifugation, all liquids are poured out and anhydrous ethanol is added. The powder is stirred and dispersed evenly in the anhydrous ethanol, placed in a beaker and dried. The drying temperature is 60℃ and the drying time is 16h.

[0082] (6) Heat treatment and sintering: The raw material from step S5 was subjected to heat treatment and atmospheric pressure sintering to obtain a high-entropy phosphate ceramic material with a xenotime structure. The heat treatment time of the powder after reaction was 4 hours, and the heat treatment temperature was 1000℃ to remove free water, crystal water and impurities. The heat-treated powder sample was placed in a high-temperature furnace for sintering to further densify and improve crystallinity. The sintering temperature of the powder ceramic was selected as 1500℃ and held for 4 hours. The sintering heating regime was as follows: 5℃ / min for the room temperature to 1200℃ range; 2℃ / min for the 1200℃ to 1500℃ range. The sintering cooling regime was as follows: 2℃ / min for the 1200℃ to 1500℃ range; 5℃ / min for the 500℃ to 1200℃ range; and the material was cooled with the furnace when it reached 500℃.

[0083] Example 3:

[0084] (Eu 0.2 Lu 0.2 Ho 0.2 Er 0.2 Yb 0.2 The preparation method of high-entropy phosphate powder with xenotime structure (PO4) includes the following steps:

[0085] (1) Impurity removal: The required Eu2O3, Lu2O3, Ho2O3, Er2O3, and Yb2O3 powders were calcined in a muffle furnace at 950°C to remove moisture and impurities;

[0086] (2) Weighing raw materials: Weigh 0.8798g of HfO2, 0.9948g of Lu2O3, 0.9447g of Ho2O3, 0.9574g of Er2O3, and 0.9850g of Yb2O3 powder according to the molar ratio of rare earth ions 1:1:1:1:1, for a total of 4.4081g of powder. Weigh 0.8574g of liquid phosphoric acid according to the molar ratio of H3PO4:RE2O3 = 3.5:1 and dilute it in a beaker. Mix it with deionized water at a volume ratio of H3PO4:deionized water = 1:6 to obtain a phosphoric acid solution.

[0087] (3) Mixing and refining: Accurately weighed Eu2O3, Lu2O3, Ho2O3, Er2O3, and Yb2O3 powders are mixed and then subjected to high-energy ball milling. Agate balls are used as the grinding medium and ethanol is used as the dispersant. The ball-to-powder ratio is 10:1, and the grinding balls are divided into three sizes: 1 mm, 2 mm, and 4 mm in diameter. The three sizes of grinding balls are mixed in a ratio of 5:3:2. In addition, the ball mill speed is 450 r / min, and the effective ball milling time is 24 h. The planetary ball mill stops for 10 min every 20 min of grinding, and then continues to work in the opposite direction. After repeated grinding, the machine is stopped to obtain a slurry in which all components are mixed evenly. The mixed slurry is transferred into a beaker and placed in a forced-air drying oven to dry at 80 °C for 20 h.

[0088] (4) Dispersion reaction: The diluted phosphoric acid solution and rare earth oxide powder were thoroughly mixed and continuously stirred at a constant temperature; the dried mixed oxide powder was added to the prepared phosphoric acid solution at a rate of 0.2 g / s, the temperature of the magnetic stirring was 70℃, the speed of the magnetic stirring was 550 r / min, and the stirring time was 18 h.

[0089] (5) Washing and drying: After the reaction is completed, the powder is separated from the acid by centrifugation. The washing steps are as follows: After the first centrifugation, all liquid is poured out and deionized water is added. The powder is stirred and dispersed evenly in the deionized water. The pH of the mixture is tested to be approximately 1. After the second centrifugation, the pH of the supernatant is tested to be approximately 1.5. All acidic liquid is poured out and deionized water is added. The powder is stirred and dispersed evenly in the deionized water. This step is repeated twice until the pH is neutral. After the fifth centrifugation, the pH of the supernatant is still neutral. All liquid is poured out and anhydrous ethanol is added to the same volume. The powder is stirred and dispersed evenly in the anhydrous ethanol and centrifuged again. After the sixth centrifugation, all liquid is poured out and anhydrous ethanol is added. The powder is stirred and dispersed evenly in the anhydrous ethanol, placed in a beaker and dried. The drying temperature is 80℃ and the drying time is 20h.

[0090] (6) Heat treatment and sintering: The raw material from step S5 was subjected to heat treatment and atmospheric pressure sintering to obtain a high-entropy phosphate ceramic material with a xenotime structure. The heat treatment time of the powder after reaction was 2 hours, and the heat treatment temperature was 950℃ to remove free water, crystal water and impurities. The heat-treated powder sample was placed in a high-temperature furnace for sintering to further densify and improve crystallinity. The sintering temperature of the powder ceramic was selected as 1600℃ and held for 8 hours. The sintering heating regime was as follows: 5℃ / min for the range of room temperature to 1200℃; 2℃ / min for the range of 1200℃ to 1500℃; and 1℃ / min for the range of 1500℃ to 1600℃. The sintering cooling regime is as follows: the temperature drops at 1℃ / min in the 1500℃~1600℃ range; at 2℃ / min in the 1200℃~1500℃ range; and at 5℃ / min in the 500℃~1200℃ range. The furnace is then cooled at 500℃.

[0091] Performance testing

[0092] The high-entropy ceramic powder obtained in Example 1 was subjected to the following tests: The weight loss and endothermic and exothermic stages arising from crystal transformation, decomposition, etc., during the heat exchange process of the annealed sample powder were verified using simultaneous thermal analysis (see attached). Figure 3 To determine its high-temperature phase stability.

[0093] The high-entropy ceramic powders obtained in Examples 1, 2, and 3 were pressed into bulk materials and sintered. Their thermal conductivity was then tested at 1000°C using a laser thermal conductivity meter. Table 1 shows the thermal conductivity values ​​of the corresponding xenotime high-entropy ceramic phosphate components at 1000°C. It can be seen that the thermal conductivity of the component with added oxides from raw material 2 was reduced, attributed to the increased difference in ion size and the intensified lattice distortion.

[0094] Table 1. Weight and heat flow changes obtained from simultaneous thermal analysis data in Example 1.

[0095]

[0096] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a monazite-structured high-entropy phosphate ceramic powder, characterized in that, The application relates to a preparation method of a phosphorite ceramic material with a monazite structure and high entropy, which comprises the following steps: S1, a plurality of rare earth oxide raw materials are weighed and mixed to obtain a rare earth oxide mixed raw material, and a rare earth oxide mixed powder is further obtained; S2, the rare earth oxide mixed powder is subjected to a drying and refining treatment to obtain a rare earth oxide mixed powder; the refining treatment is specifically: the rare earth oxide mixed powder is subjected to high-energy ball milling, so that the powder in the rare earth oxide mixed powder is refined to a submicron or nanometer particle size; S3, the phosphoric acid is weighed according to a molar ratio relationship of 2.5-3.5:1 between the phosphoric acid and the rare earth oxide raw material, and the weighed phosphoric acid is diluted with deionized water to obtain a phosphoric acid stabilizer; The phosphoric acid stabilizer and the rare earth oxide mixed powder are subjected to a dispersion reaction to obtain a dispersed rare earth oxide mixed powder; the dispersed rare earth oxide mixed powder is a phosphorite powder; S4, the dispersed rare earth oxide mixed powder is washed and dried to obtain a raw material; S5, the raw material is subjected to heat treatment and normal-pressure sintering to obtain a phosphorite ceramic material with a monazite structure and high entropy.

2. The production method according to claim 1, characterized by, The plurality of rare earth oxide raw materials in step S1 are five rare earth oxide raw materials.

3. The production method according to claim 2, characterized by, The five rare earth oxide raw materials comprise a raw material one and a raw material two; The raw material one is any four or more than four of Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Y2O3 and Lu2O3; The second raw material is at most one of La2O3, Pr6O 11 Nd2O3, Sm2O3, Eu2O3, and Gd2O3.

4. The production method according to claim 3, characterized by, The five rare earth oxide raw materials comprise any four of Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Y2O3 and Lu2O3 in the raw material one; Any one of La2O3, Pr6O 11 , Nd2O3, Sm2O3, Eu2O3, and Gd2O3 5. The preparation method according to claim 4, characterized in that, The ion molar ratio of the rare earth elements in the five rare earth oxide raw materials is 1:1:1:1:

1.

6. The method of claim 1, wherein, The volume ratio of the weighed phosphoric acid to the deionized water is 1:4-7.

7. The preparation method according to claim 1, characterized in that, The dispersion reaction in step S3 is that the phosphoric acid stabilizer and the rare earth oxide mixed powder are fully mixed and continuously stirred at a constant temperature; The washing and drying in step S4 are centrifugal washing with deionized water and ethanol, and full drying under normal pressure in a blast drying oven to obtain a raw material.

8. The method of claim 1, wherein, The sintering in step S5 comprises a heating schedule and a cooling schedule, and the sintering is performed according to the heating schedule and the cooling schedule; The heating schedule of the sintering is as follows: The temperature is raised at 5 DEG C / min in the room temperature-1200 DEG C section; The temperature is raised at 2 DEG C / min in the 1200 DEG C-1500 DEG C section; The temperature is raised at 2 DEG C / min in the 1500 DEG C-1600 DEG C section; The cooling schedule of the sintering is as follows: The temperature is lowered at 2 DEG C / min in the 1500 DEG C-1600 DEG C section; The temperature is lowered at 2 DEG C / min in the 1200 DEG C-1500 DEG C section; The temperature is lowered at 5 DEG C / min in the 500 DEG C-1200 DEG C section; The temperature is lowered to 500 DEG C and the furnace is cooled.

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