Preparation method of ytterbium oxide with specific particle size and specific surface area

Abstract

The invention relates to a preparation method of ytterbium oxide with specific granularity and specific surface area, and belongs to the technical field of rare earth oxide preparation. The preparation method comprises the following steps: preparing oxalic acid into an oxalic acid solution with the mass fraction of 5-15wt%; preparing ytterbium chloride into an ytterbium chloride solution with the concentration of 0.2-1.0 mol / L; a polyvinyl alcohol dispersing agent solution with the mass fraction of 0.8-1.5 wt% is added into the ytterbium chloride solution, the adding amount of the polyvinyl alcohol dispersing agent solution is 2-4% of the mass of the ytterbium chloride solution, and ytterbium chloride mixed liquid is obtained; warm water is added into a reaction kettle, the ytterbium chloride mixed solution is continuously added along with stirring operation, and then the oxalic acid solution is continuously added; and directly carrying out vacuum filtration without aging, collecting a filter cake, and calcining to obtain a finished product. By optimizing the using amount of the dispersing agent and the precipitation process and accurately controlling process parameters, the obtained product is stable in performance, uniform in particle size distribution, small in specific surface area deviation and good in reproducibility.

Description

Technical Field

[0001] This invention belongs to the technical field of rare earth oxide preparation, and more specifically, relates to a method for preparing ytterbium oxide with a specific particle size and specific surface area. Background Technology

[0002] Ytterbium oxide, as an important rare earth oxide, is widely used in the manufacture of permanent magnet materials, optical glass, ceramic colorants, laser materials, catalysts, and other fields. With the development of science and technology, the demand for ytterbium oxide in high-end applications such as thermal spray coatings, sputtering targets, and vacuum coating is increasing, and people are putting forward more precise requirements for the particle size and specific surface area of ​​ytterbium oxide.

[0003] In existing technologies, ytterbium oxide powder generally suffers from problems such as uneven particle size distribution and unstable specific surface area. Currently, ytterbium oxide is mainly prepared using extraction, oxalic acid precipitation, or carbonate precipitation methods. Traditional methods produce ytterbium oxide with a wide particle size distribution, typically D50 in the range of 2-12 μm, and a small specific surface area. Due to the imprecise control of particle size and specific surface area, product performance fluctuates greatly, failing to meet the performance requirements of high-end applications. Furthermore, conventional precipitation methods usually require an aging process, leading to a wider particle size distribution and difficulty in precisely controlling the specific surface area. Although some methods for preparing nanoscale ytterbium oxide exist, these methods often suffer from complex processes, demanding process conditions, high equipment requirements, high production costs, wide particle size distribution, and imprecise control of specific surface area. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing ytterbium oxide with a specific particle size and specific surface area, which has the characteristics of narrow particle size distribution and small specific surface area deviation.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing ytterbium oxide with a specific particle size and specific surface area includes the following steps: S1. Add oxalic acid to pure water, and the amount of oxalic acid is 1.2-1.5 times the theoretical weight of ytterbium oxide obtained by precipitation. Prepare an oxalic acid solution with a mass fraction of 5-15 wt% and keep it at 30-60℃. S2. Prepare a ytterbium chloride solution with a concentration of 0.2-1.0 mol / L; S3. Add a polyvinyl alcohol dispersant solution with a mass fraction of 0.8-1.5 wt% to the ytterbium chloride solution, the amount added being 2-4% of the mass of the ytterbium chloride solution. After dispersion, keep warm at 30-60℃ to obtain a ytterbium chloride mixture. S4. Add warm water at 30-60℃ to the reactor as bottom water. While stirring, first continuously add the ytterbium chloride mixture, then continuously add the oxalic acid solution. S5. Vacuum filter directly without aging, collect the filter cake, and wash it with hot water at 80-100℃ until no chloride ions are detected to obtain ytterbium oxalate. S6. Calcine ytterbium oxalate at 800-900℃ for 3-5 hours to obtain the finished product.

[0006] Furthermore, the mass ratio of oxalic acid to ytterbium chloride is (0.6-1.1):1.

[0007] Further, in step S2, the ytterbium chloride is ytterbium chloride hexahydrate or anhydrous ytterbium chloride. When the ytterbium chloride is ytterbium chloride hexahydrate, the mass ratio of oxalic acid to ytterbium chloride is (0.6-0.8):1; when the ytterbium chloride is anhydrous ytterbium chloride, the mass ratio of oxalic acid to ytterbium chloride is (0.81-1.1):1.

[0008] The method for calculating the mass ratio of oxalic acid to ytterbium chloride is as follows: Ytterbium chloride reacts with oxalic acid to form ytterbium oxalate precipitate. The reaction formula is as follows: 2YbCl3+ 3H2C2O4→ Yb2(C2O4)3↓ + 6HCl; Ytterbium oxalate precipitate undergoes an oxidation reaction during calcination to form ytterbium oxide. The reaction formula is as follows: Yb2(C2O4)3+O2→ Yb2O3+ 5CO2↑+CO↑; When the ytterbium chloride is ytterbium chloride hexahydrate, since the molecular weight of ytterbium chloride hexahydrate (YbCl3·6H2O) is 387.49 g / mol and the molecular weight of ytterbium oxide (Yb2O3) is 394.08 g / mol, the number of moles of ytterbium added = the mass of ytterbium chloride hexahydrate added / the molecular weight of ytterbium chloride hexahydrate. Due to the two ytterbium ions (Yb 3+ Each mole of ytterbium ions forms one ytterbium oxide (Yb₂O₃) molecule, meaning that every 2 moles of ytterbium ions generate 1 mole of ytterbium oxide. Therefore, the relationship between the number of moles of ytterbium and the number of moles of ytterbium oxide is: number of moles of ytterbium oxide = number of moles of ytterbium / 2. Therefore, the theoretical mass of ytterbium oxide = number of moles of ytterbium oxide × molecular weight of ytterbium oxide = (number of moles of ytterbium / 2) × molecular weight of ytterbium oxide = [(mass of ytterbium chloride hexahydrate added / molecular weight of ytterbium chloride hexahydrate) / 2] × molecular weight of ytterbium oxide = [(mass of ytterbium chloride hexahydrate added / 387.49) / 2] × 394.08 = mass of ytterbium chloride hexahydrate added × 0.51; Since the amount of oxalic acid used is 1.2-1.5 times the theoretical weight of ytterbium oxide obtained by precipitation, that is, the amount of oxalic acid used = theoretical mass of ytterbium oxide × (1.2-1.5); the ratio of oxalic acid used to the mass of ytterbium chloride hexahydrate is 0.51 × (1.2-1.5):1 = (0.6-0.8):1.

[0009] Correspondingly, when the ytterbium chloride is anhydrous ytterbium chloride, since the molecular weight of anhydrous ytterbium chloride (YbCl3) is 279.39 g / mol, the number of moles of ytterbium element added = the mass of anhydrous ytterbium chloride added / the molecular weight of anhydrous ytterbium chloride; Theoretical ytterbium oxide mass = number of ytterbium oxide moles × molecular weight of ytterbium oxide = (number of ytterbium moles / 2) × molecular weight of ytterbium oxide = [(mass of anhydrous ytterbium chloride input / molecular weight of anhydrous ytterbium chloride) / 2] × molecular weight of ytterbium oxide = [(mass of anhydrous ytterbium chloride input / 279.39) / 2] × 394.08 = mass of anhydrous ytterbium chloride input × 0.71; Since the amount of oxalic acid used is 1.2-1.5 times the theoretical weight of ytterbium oxide obtained by precipitation, that is, the amount of oxalic acid used = theoretical ytterbium oxide mass × (1.2-1.5); the ratio of oxalic acid used to anhydrous ytterbium chloride mass = 0.71 × (1.2-1.5):1 = (0.85-1.1):1.

[0010] Further, in step S3, the molecular weight of polyvinyl alcohol is 20,000-40,000, and the dispersion refers to stirring at a speed of 400-600 rpm for 15-30 minutes.

[0011] Further, in step S4, the volume of the bottom water accounts for 35-45% of the total volume of the final reaction mixture; the stirring speed is 150-300 rpm; the ytterbium chloride mixture is added at a time of 40-50 minutes, and the oxalic acid solution is added at a time of 50-65 minutes.

[0012] Furthermore, in step S4, the pH value of the reaction system in the reactor is controlled to be 1.5-2.2.

[0013] Furthermore, in step S5, the vacuum degree of the vacuum filtration is -0.085 to -0.095 MPa; the amount of water used for each washing is 3 to 5 times the volume of the filter cake.

[0014] Traditional processes typically require aging to improve product performance. However, this new technology, under controlled parameters such as raw material dosage, bottom water ratio, and temperature, achieves the formation of ytterbium oxalate precipitates with ideal particle size and morphology without aging. In contrast, the Ostwald ripening process that occurs during traditional aging can negatively impact particle growth, leading to a wider particle size distribution and consequently, poorer product performance. Furthermore, this technology utilizes high-temperature hot water (80-100℃) to wash the product, effectively removing impurity ions while maintaining particle surface characteristics and controlling the specific surface area of ​​the final product.

[0015] Further, in step S6, before calcining ytterbium oxalate, it is pre-dried at 110-120℃ for 2-3 hours; during calcination, a stepped heating calcination process is adopted, with the heating rate controlled at 3-4℃ / min; after calcination, it is cooled to 150-200℃ at a cooling rate of 2-3℃ / min; then it is placed in a dry environment to cool to room temperature to obtain the finished product.

[0016] The use of a stepped heating and calcination process helps to make the decomposition process of ytterbium oxalate gradual, avoiding the bursting and over-sintering of particles during rapid heating, and maintaining ideal particle size distribution and specific surface area.

[0017] More preferably, in step S1, the oxalic acid solution has a mass fraction of 9-13 wt% and the holding temperature is 40-50℃; in step S2, the ytterbium chloride solution has a concentration of 0.4-0.8 mol / L; in step S3, the holding temperature is 40-50℃; in step S4, the bottom water temperature is 45-55℃; in step S5, the hot water temperature is 85-95℃; and in step S6, the calcination temperature is 830-870℃ and the calcination time is 3.5-4.5 hours.

[0018] A ytterbium oxide with a specific particle size and specific surface area is prepared using the aforementioned method for preparing ytterbium oxide with specific particle size and specific surface area. The ytterbium oxide has a particle size D50 of 2-2.5 μm and a specific surface area of ​​6-7 m². 2 / g.

[0019] The beneficial effects of this invention are: (1) This invention optimizes the dosage of dispersant and the precipitation process, using polyvinyl alcohol with a molecular weight of 20,000-40,000 as the dispersant, and controlling its addition amount to 2-4% of the mass of the ytterbium chloride solution. This effectively inhibits non-uniform particle growth and agglomeration, resulting in a narrow particle size distribution, more uniform particles, and smaller specific surface area deviation. Simultaneously, it completely decomposes during calcination, without introducing impurities. Washing with high-temperature hot water at 80-100℃ helps remove impurity ions, prevents secondary particle agglomeration, and controls particle surface characteristics, ensuring the final product's specific surface area remains stable at 6.5±0.5m². 2 Within the range of / g; by calcining ytterbium oxalate at a high temperature of 800-900℃ for 3-5 hours, it is beneficial to achieve complete decomposition of ytterbium oxalate into ytterbium oxide, while effectively controlling particle size and specific surface area.

[0020] (2) The present invention adopts conventional chemical precipitation method, which is simple, requires no special equipment and raw materials, has low production cost, and is easy to industrialize; and the present invention does not require aging, which can avoid the Ostwald ripening phenomenon caused by traditional aging process, thereby obtaining a more uniform particle size distribution; by precisely controlling process parameters, the product performance is stable, the particle size distribution is uniform, the specific surface area deviation is small, and the reproducibility is good. Detailed Implementation

[0021] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0022] Example 1 A method for preparing ytterbium oxide with a specific particle size and specific surface area includes the following steps: S1: Weigh 328g of refined oxalic acid and add it to 2092g of pure water to prepare a 13.6% oxalic acid solution. Stir until uniform at 45℃ and keep warm at 45℃. S2: Dissolve 478g of ytterbium chloride hexahydrate (purity 99.99%) in an appropriate amount of pure water, add water to make up to 1500mL, and prepare a 0.823mol / L solution; S3: Add 50g of a 1.2wt% polyvinyl alcohol (molecular weight of 30,000) solution to the solution obtained in step S2, stir at 500rpm for 20 minutes, and keep warm at 45℃. S4: Add 2610 mL of pure water to the reactor as the base water. At a temperature of 50°C, add the ytterbium chloride mixed solution and oxalic acid solution sequentially and continuously while stirring at 200 rpm. Monitor the pH of the reaction system using an online pH meter and control the pH value within the range of 1.7-1.9. Simultaneously, control the addition of the ytterbium chloride mixed solution to be completed within 40-50 minutes and the addition of the oxalic acid solution to be completed within 50-65 minutes. S5: After the reaction is complete, do not age the filter cake. Instead, perform vacuum filtration at a vacuum of -0.09 MPa, collect the filter cake, and wash it multiple times with 90°C hot water in a countercurrent manner, using 4 times the volume of the filter cake each time. Stop washing when the washing water solution does not show any white turbidity when tested with 0.1 mol / L silver nitrate. S6: Spread the washed ytterbium oxalate filter cake evenly in a ceramic crucible, with a material layer thickness not exceeding 2cm. Pre-dry at 115℃ for 3 hours, then place it in a pusher kiln and heat it to 850℃ at 3.5℃ / min in an air atmosphere. Hold it at that temperature for 4.5 hours. After calcination, cool it to 180℃ at a cooling rate of 2.5℃ / min and then cool it to room temperature in a dry environment to obtain the finished product.

[0023] Example 2 A method for preparing ytterbium oxide with a specific particle size and specific surface area includes the following steps: S1: Weigh 231g of refined oxalic acid and add it to 2079mL of pure water to prepare a 10% oxalic acid solution. Stir at 40℃ until uniform and keep warm at 40℃. S2: Dissolve 350g of ytterbium chloride hexahydrate (purity 99.99%) in an appropriate amount of pure water, add water to make up to 1400mL, and prepare a 0.65mol / L solution; S3: Add 42g of a 1.0wt% polyvinyl alcohol (molecular weight 30,000) solution, stir at 450rpm for 20 minutes, and keep warm at 40℃; S4: Add 1540 mL of pure water to the reactor as the base water. At a temperature of 45°C, add the ytterbium chloride mixed solution and oxalic acid solution sequentially and continuously while stirring at 180 rpm. Monitor the pH of the reaction system using an online pH meter and control the pH value within the range of 1.7-1.9. The ytterbium chloride mixed solution should be added over 40-50 minutes, and the oxalic acid solution over 50-65 minutes. S5: After the reaction is complete, do not age the filter cake. Directly perform vacuum filtration under a vacuum of -0.09MPa. Wash the filter cake multiple times with 85℃ hot water in a countercurrent manner, using 4 times the volume of water each time. Stop washing when the washing water solution does not show any white turbidity when tested with 0.1mol / L silver nitrate. S6: Spread the washed ytterbium oxalate filter cake evenly in a ceramic crucible, with a material layer thickness not exceeding 2cm. Pre-dry at 110℃ for 2.5 hours, then place it in a pusher kiln and heat it to 830℃ at 3.0℃ / min in an air atmosphere. Hold it at that temperature for 4 hours. After calcination, cool it to 180℃ at a cooling rate of 2.0℃ / min and then cool it to room temperature in a dry environment to obtain the finished product.

[0024] Example 3 A method for preparing ytterbium oxide with a specific particle size and specific surface area includes the following steps: S1: Weigh 213g of refined oxalic acid and add it to 2162g of pure water to prepare a 9% oxalic acid solution. Stir at 42℃ until uniform and keep warm at 42℃. S2: Dissolve 300g of ytterbium chloride hexahydrate (purity 99.99%) in an appropriate amount of pure water, add water to make up to 1600mL, and prepare a 0.55mol / L solution; S3: Add 36g of a 1.3wt% polyvinyl alcohol (molecular weight 25,000) solution to the solution obtained in step S2, stir at 480rpm for 25 minutes, and keep warm at 42℃. S4: Add 912 mL of pure water to the reactor as the base water. At a temperature of 48°C, add the ytterbium chloride mixed solution and oxalic acid solution sequentially and continuously while stirring at 190 rpm. Monitor the pH of the reaction system using an online pH meter and control the pH value within the range of 1.7-1.9. Simultaneously, control the addition of the ytterbium chloride mixed solution to be completed within 40-50 minutes and the addition of the oxalic acid solution to be completed within 50-65 minutes. S5: After the reaction is complete, do not age the filter cake. Instead, perform vacuum filtration at a vacuum of -0.09 MPa, collect the filter cake, and wash it multiple times with 90°C hot water in a countercurrent manner, using 4 times the volume of the filter cake each time. Stop washing when the washing water solution does not show any white turbidity when tested with 0.1 mol / L silver nitrate. S6: Spread the washed ytterbium oxalate filter cake evenly in a ceramic crucible, with a material layer thickness not exceeding 2cm. Pre-dry at 115℃ for 2 hours, then place it in a pusher kiln and heat it to 820℃ at 4℃ / min in an air atmosphere. Hold it at that temperature for 3.5 hours. After calcination, cool it to 180℃ at a cooling rate of 3℃ / min and then cool it to room temperature in a dry environment to obtain the finished product.

[0025] Example 4 A method for preparing ytterbium oxide with a specific particle size and specific surface area includes the following steps: S1: Weigh 328g of refined oxalic acid and add it to 2147g of pure water to prepare a 13.3% oxalic acid solution. Stir at 45℃ until uniform and keep warm at 45℃. S2: Add 345g of anhydrous ytterbium chloride (purity 99.99%) in portions to about 1000mL of pure water at 30℃. After it is completely dissolved and cooled to room temperature, add water to make up to 1500mL to prepare a 0.823mol / L solution. S3: Add 50g of a 1.2wt% polyvinyl alcohol (molecular weight of 30,000) solution to the solution obtained in step S2, stir at 500rpm for 20 minutes, and keep warm at 45℃. S4: Add 2610 mL of pure water as the base water to the reactor at 50°C, and continuously add the ytterbium chloride mixed solution and oxalic acid solution sequentially while stirring at 200 rpm; monitor the pH of the reaction system using an online pH meter to control the pH value within the range of 1.6-1.8; simultaneously control the addition of the ytterbium chloride mixed solution to be completed within 40-50 minutes, and the addition of the oxalic acid solution to be completed within 50-65 minutes; S5: After the reaction is complete, do not age the filter cake. Instead, perform vacuum filtration at a vacuum of -0.09 MPa, collect the filter cake, and wash it multiple times with 90°C hot water in a countercurrent manner, using 4 times the volume of the filter cake each time. Stop washing when the washing water solution does not show any white turbidity when tested with 0.1 mol / L silver nitrate. S6: Spread the washed ytterbium oxalate filter cake evenly in a ceramic crucible, with a material layer thickness not exceeding 2cm. Pre-dry at 115℃ for 3 hours, then place it in a pusher kiln and heat it to 850℃ at 3.5℃ / min in an air atmosphere. Hold it at that temperature for 4.5 hours. After calcination, cool it to 180℃ at a cooling rate of 2.5℃ / min and then cool it to room temperature in a dry environment to obtain the finished product.

[0026] Comparative Example 1 Compared with Example 1, the difference in this comparative example is that step S1 of this comparative example is as follows: 242g of refined oxalic acid is weighed and added to 2100g of pure water to prepare a 10.3% oxalic acid solution, which is stirred at 45°C until uniform and kept at 45°C; the remaining components, preparation steps and parameters are the same.

[0027] Comparative Example 2 Compared with Example 1, the difference in this comparative example is that step S3 of this comparative example is: adding 15g of a 0.5wt% polyvinyl alcohol (molecular weight of 12,000) solution to the solution obtained in step S2, stirring at 500rpm for 20 minutes, and keeping it at 45°C; the remaining components, preparation steps and parameters are the same.

[0028] Comparative Example 3 Compared with Example 1, this comparative example differs in that step S6 is as follows: the washed ytterbium oxalate filter cake is evenly spread in a ceramic crucible with a layer thickness not exceeding 2 cm, pre-dried at 115°C for 3 hours, then placed in a pusher kiln, heated to 950°C at 3.5°C / min in air atmosphere, held at that temperature for 2 hours, and after calcination, cooled to 180°C at a cooling rate of 2.5°C / min, and then cooled to room temperature in a dry environment to obtain the finished product. All other components, preparation steps, and parameters are the same.

[0029] Comparative Example 4 Compared with Example 1, the difference in this comparative example is that step S5 of this comparative example is as follows: After the reaction is completed, the mixture is kept at a constant temperature of 50°C and stirred at a low speed of 50 rpm in the reaction vessel for 4 hours. Then, it is vacuum filtered under a vacuum of -0.09 MPa to collect the filter cake. The filter cake is washed multiple times countercurrently with 90°C hot water, with the water volume being 4 times that of the filter cake each time. The washing is stopped when the washing water solution shows no white turbidity when tested with 0.1 mol / L silver nitrate. The remaining components, preparation steps, and parameters are the same.

[0030] Product verification: The particle size distribution of the samples prepared in the above examples and comparative examples was determined by laser particle size analyzer, the specific surface area was determined by BET nitrogen adsorption method, and the purity was determined by ICP-OES (inductively coupled plasma optical emission spectrometry).

[0031] The characteristic test results of the samples prepared in the above embodiments and comparative examples are shown in Table 1.

[0032] Table 1 As shown in Table 1, compared with Comparative Examples 1-4, the ytterbium oxide samples prepared in Examples 1-4 have particle size D50 and specific surface area within a reasonable range, and a lower particle size distribution span value, indicating a more uniform particle size distribution. In terms of particle morphology, all examples yielded relatively uniform spherical samples with good dispersibility. The results of Comparative Examples 1-4 were inferior to those of Examples 1-4, indicating that parameters such as the amount of oxalic acid, the amount and mass fraction of polyvinyl alcohol, the calcination temperature, and whether aging was used have a significant impact on this technical solution. Therefore, this technical solution significantly improves the performance of the prepared ytterbium oxide samples by precisely controlling the amount of oxalic acid, the concentration and amount of PVA, the calcination process, and discarding the aging process, thereby obtaining high-quality ytterbium oxide powder.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for the preparation of a particular particle size and specific surface area of ytterbium oxide, characterized in that, The method comprises the following steps: S1, adding oxalic acid into pure water, and the amount of oxalic acid is 1.2-1.5 times of the theoretical weight of the precipitated ytterbium oxide, preparing a 5-15wt% oxalic acid solution, and keeping the temperature at 30-60℃; S2, preparing a ytterbium chloride solution with a concentration of 0.2-1.0mol / L; S3, adding a 0.8-1.5wt% polyvinyl alcohol dispersant solution into the ytterbium chloride solution, and the amount of the polyvinyl alcohol dispersant solution is 2-4% of the mass of the ytterbium chloride solution, and keeping the temperature at 30-60℃ after dispersion; S4, adding warm water with a temperature of 30-60℃ as the bottom water in a reaction kettle, continuously adding the ytterbium chloride mixture and then continuously adding the oxalic acid solution with stirring; S5, directly vacuum filtering without aging, collecting the filter cake, and washing the filter cake with hot water with a temperature of 80-100℃ until no chloride ion is detected, to obtain ytterbium oxalate; S6, calcining the ytterbium oxalate at 800-900℃ for 3-5 hours to obtain the finished product.

2. The method of claim 1, wherein the method is characterized by, The mass ratio of the oxalic acid to the ytterbium chloride is (0.6-1.1):

1.

3. The method of claim 2, wherein the method is characterized by, In step S2, the ytterbium chloride is ytterbium chloride hexahydrate or anhydrous ytterbium chloride, when the ytterbium chloride is ytterbium chloride hexahydrate, the mass ratio of the oxalic acid to the ytterbium chloride is (0.6-0.8):1; when the ytterbium chloride is anhydrous ytterbium chloride, the mass ratio of the oxalic acid to the ytterbium chloride is (0.81-1.1):

1.

4. The method of claim 1, wherein the method is characterized by, In step S3, the molecular weight of the polyvinyl alcohol is 20-40 thousand, and the dispersion refers to stirring at a speed of 400-600rpm for 15-30 minutes.

5. The method of claim 1, wherein the method is characterized by: In step S4, the volume ratio of the bottom water to the total volume of the final reaction mixture is 35-45%, the stirring speed is 150-300rpm, the ytterbium chloride mixture is added for 40-50 minutes, and the oxalic acid solution is added for 50-65 minutes.

6. The method of claim 1, wherein the method is characterized by: In step S4, the pH value of the reaction system in the reaction kettle is controlled to be 1.5-2.

2.

7. The method of claim 1, wherein the method is characterized by, In step S5, the vacuum degree of the vacuum filtration is -0.085 to -0.095MPa, and the amount of water used for each washing is 3-5 times of the volume of the filter cake.

8. The method of claim 1, wherein the method is characterized by: In step S6, the ytterbium oxalate is pre-dried at 110-120℃ for 2-3 hours before calcination, a stepwise temperature rising calcination process is adopted during calcination, the temperature rising rate is controlled to be 3-4℃ / min, after calcination, the temperature is reduced to 150-200℃ at a cooling rate of 2-3℃ / min, and then the product is cooled to room temperature in a dry environment.

9. The method of claim 1, wherein the method is characterized by, In step S1, the mass fraction of the oxalic acid solution is 9-13wt%, and the temperature during keeping is 40-50℃; in step S2, the concentration of the ytterbium chloride solution is 0.4-0.8mol / L; in step S3, the temperature during keeping is 40-50℃; in step S4, the temperature of the bottom water is 45-55℃; in step S5, the temperature of the hot water is 85-95℃; in step S6, the calcination temperature is 830-870℃, and the calcination time is 3.5-4.5 hours.

10. Ytterbium oxide of a specific particle size and specific surface area, obtainable by the process according to any one of claims 1 to 9, characterized in that The ytterbium oxide has a particle size D50 of 2-2.5 pm and a specific surface area of 6-7 m 2 / g.

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