A method for preparing rectangular yttrium oxide with low chlorine content
By saponification reaction, back-extraction and ultrasonic treatment during the preparation of yttrium oxide, combined with high temperature calcination, the problems of high chlorine content and irregular particle shape of existing yttrium oxide products have been successfully solved, and the efficiency of rectangular yttrium oxide with low chlorine content has been achieved. Preparation meets high purity and shape requirements.
Patent Information
- Application Number
- CN202411087629.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-09
- Publication Date
- 2025-02-07
- Estimated Expiration
- 2044-08-09
AI Technical Summary
The existing yttrium oxide products have high chlorine content and irregular particle shapes, which are difficult to meet customers' demand for rectangular yttrium oxide with low chlorine content.
A preparation method is adopted, including saponification reaction in a reaction vessel, adding high-purity yttrium chloride solution and stirring, followed by a mixture of acetic acid and adipic acid, and then reacting and filtration under ultrasonic action, and finally passing through high temperature Calcination gives a rectangular yttrium oxide with low chlorine content.
A high-purity yttrium oxide with a chlorine content of less than 30ppm, a purity of more than 99.99%, and a rectangular particle shape, meeting the customer's high purity and shape requirements.
Abstract
Description
Technical Field
[0001] This invention relates to the field of yttrium oxide preparation, and more specifically to a method for preparing rectangular yttrium oxide with low chlorine content. Background Technology
[0002] Yttrium oxide (Y₂O₃) is an important inorganic compound, belonging to the rare earth oxides. It is a white powder with a melting point of approximately 2410℃, exhibiting high heat resistance and good chemical stability. In its natural state, it exists as the mineral yttrium ore. As an alkaline earth metal oxide, yttrium oxide is basic and can react with strong acids to form salts and water. It can react directly with many nonmetals at high temperatures. Yttrium oxide is mainly used in the following areas:
[0003] 1. Luminescent materials: Yttrium oxide can be used as a matrix material to form phosphors with other rare earth elements (such as europium and neodymium), which are widely used in the lighting field, such as phosphors for LED lights, televisions and computer screens.
[0004] 2. Ceramic materials: Due to its excellent thermal stability and mechanical properties, yttrium oxide is used as an additive in advanced ceramics, especially in the production of high-performance ceramic capacitors, oxygen sensors and high-temperature resistant ceramic parts.
[0005] 3. Optical applications: Yttrium oxide crystals have excellent optical properties and can be used as laser materials, such as the active medium in yttrium aluminum garnet (YAG) lasers.
[0006] 4. Catalysts: In the chemical industry, yttrium oxide is used as a catalyst or catalyst support in processes such as petroleum refining and organic synthesis to improve catalytic efficiency and selectivity.
[0007] 5. Medical applications: Some yttrium compounds, such as yttrium-stabilized zirconium oxide, are used to make artificial joints and dental implants due to their good biocompatibility.
[0008] 6. Nuclear Energy Applications: Yttrium oxide can be doped into uranium dioxide fuel to form yttrium-stabilized uranium dioxide (YSU), which can improve the performance and safety of nuclear fuel.
[0009] Ordinary yttrium oxide products contain approximately 100–200 ppm of chlorine, and the particles appear as random amorphous shapes in scanning electron microscopy (SEM) images. Some customers require high-purity yttrium oxide with a chlorine content of less than 30 ppm and rectangular particle shapes. This low-chlorine-content rectangular yttrium oxide is mainly used in the electronics industry, including consumer electronics, telecommunications, and computers. As a novel rare earth material, researching a method for preparing low-chlorine-content rectangular yttrium oxide has practical significance for production applications. Summary of the Invention
[0010] To address the shortcomings of existing technologies, this invention provides a method for preparing rectangular yttrium oxide with low chlorine content.
[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0012] A method for preparing rectangular yttrium oxide with low chlorine content includes the following steps:
[0013] S1: Add naphthenic acid solution to the reaction vessel, then add liquid alkali to carry out the saponification reaction. After the liquid alkali is added, continue the reaction for 5 minutes to obtain the reaction solution.
[0014] S2: Add the high-purity yttrium chloride solution to the reaction solution obtained in step S1, stir for 20 min, release the aqueous phase, and wash the naphthenic acid with pure water until the water discharge conductivity is less than 30 S / m;
[0015] S3: Add the prepared acetic acid and adipic acid mixed solution to the naphthenic acid washed in step S2, turn on the stirrer and back-extract the naphthenic acid for 30 min, and back-extract to separate yttrium acetate and yttrium adipic acid solutions. The molar concentration of yttrium acetate is 0.2-0.4 mol / L, the molar concentration of yttrium adipic acid is 0-0.03 mol / L, and the chlorine content is less than 30 ppm.
[0016] S4: Add oxalic acid aqueous solution to ammonia water and stir continuously until the pH value of the solution is 6-8, and then filter to obtain a mixed solution;
[0017] S5: Add the mixture obtained in step S4 to the ultrasonic synthesis device, and then add it to the yttrium acetate and yttrium adipic acid solution obtained in step S3. Stir under ultrasonic action for 40-80 minutes at a stirring speed of 140-200 r / min. After the yttrium acetate and yttrium adipic acid solution are added, the reaction is complete. Filter the solution with filter paper, and check whether the mother liquor after filtration is completely precipitated with saturated oxalic acid aqueous solution.
[0018] S6: Pour the slurry obtained in step S5 into a small centrifuge for solid-liquid separation. After the mother liquor is dried, add deionized water and turn on the centrifuge for water washing. Stop water washing when the conductivity of the water spun out of the centrifuge is less than 200 S / m. Turn on the centrifuge to dry it thoroughly. After drying, yttrium oxalate is obtained.
[0019] S7: The yttrium oxalate obtained in step S6 is placed into a crucible, which is then placed in a muffle furnace. The muffle furnace is heated from room temperature to 850℃~920℃ for 90~120min and held for 100~150min. After natural cooling, yttrium oxide powder is obtained. It is then sieved through a 120-mesh standard sieve to obtain high-purity yttrium oxide with a chlorine content of less than 30ppm, a purity of greater than 99.99%, and a rectangular particle shape.
[0020] Further, in step S1, the naphthenic acid solution is a mixed solution of naphthenic acid, kerosene, and 2-octanol, with a volume ratio of naphthenic acid, kerosene, and 2-octanol of 1:1:3.5, a concentration of liquid alkali of 10.8 mol / L, and a volume ratio of liquid alkali to naphthenic acid solution of 325:12.
[0021] Furthermore, the addition of the high-purity yttrium chloride solution in step S2, the addition of the liquid alkali solution in step S1, and the addition of the washed naphthenic acid in step S3 are all done by mist spraying. The mist spraying method can improve the back-extraction and reaction efficiency, and the effect is obvious.
[0022] Furthermore, in step S2, the concentration of the high-purity yttrium chloride solution is 0.5 mol / L, and the volume ratio of the high-purity yttrium chloride solution to the naphthenic acid solution in step S1 is 1:3.8.
[0023] Furthermore, in step S4, the concentration of oxalic acid is 5-8 wt%, the concentration of ammonia is 12.0-14.0 mol / L, and the number of moles of oxalic acid is 3.2 times that of yttrium chloride in step S2.
[0024] Furthermore, in step S3, the concentration of acetic acid in the mixed solution of acetic acid and adipic acid is 1-1.5 mol / L, and the concentration of adipic acid is 0-0.2 mol / L. Adding adipic acid to acetic acid is beneficial because adipic acid has a longer carbon chain and greater polarity, making it easier to enter the naphthenic acid solution, resulting in better back-extraction and less loss of yttrium.
[0025] Furthermore, in step S3, the volume ratio of the washed naphthenic acid to the mixed solution of acetic acid and adipic acid is 3:1.
[0026] Furthermore, in step S5, the ultrasonic frequency is 28 kHz.
[0027] Furthermore, in step S7, after the muffle furnace is heated to 500°C, pure oxygen is introduced for calcination, resulting in yttrium oxide with better purity and better rectangularity.
[0028] The preparation process of this invention has low energy consumption and is easy to operate. No other pollutants are introduced during the preparation process. The prepared yttrium chloride has a content of less than 30 ppm, a purity of more than 99.99%, high rectangularity, and wide application. Detailed Implementation
[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0030] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0031] Example 1
[0032] A method for preparing rectangular yttrium oxide with low chlorine content includes the following steps:
[0033] S1: Add 6.5L of naphthenic acid solution to the reaction vessel, then add 240ml of 10.8mol / L liquid alkali (sodium hydroxide solution) to carry out the saponification reaction. After the liquid alkali is added, continue the reaction for 5min to obtain the reaction solution.
[0034] S2: Add 1.7 L of 0.5 mol / L high-purity yttrium chloride solution to the reaction solution obtained in step S1, stir for 20 min, release the aqueous phase, and wash the naphthenic acid with pure water until the water conductivity is less than 30 S / m;
[0035] S3: Add 2.17 L of a mixed solution of acetic acid and adipic acid to the naphthenic acid washed in step S2, turn on the stirrer and back-extract the naphthenic acid for 30 min, and back-extract to separate yttrium acetate and yttrium adipic acid solutions. The molar concentration of yttrium acetate is 0.37 mol / L, the molar concentration of yttrium adipic acid is 0.01 mol / L, and the chlorine content is less than 30 ppm. The concentration of acetic acid in the mixed solution of acetic acid and adipic acid is 1.2 mol / L, and the concentration of adipic acid is 0.02 mol / L.
[0036] S4: Add the oxalic acid aqueous solution to the ammonia water and stir continuously until the pH value of the solution is 6-8, and then filter to obtain a mixed solution. The concentration of oxalic acid is 6wt%, the concentration of ammonia water is 14mol / L, and the number of moles of oxalic acid is 3.2 times that of yttrium chloride in step S2.
[0037] S5: Add the mixture obtained in step S4 to the ultrasonic synthesis device, and then add it to the yttrium acetate and yttrium adipic acid solution obtained in step S3. Stir under ultrasonic action for 40-80 min at a stirring speed of 140-200 r / min. After adding the yttrium acetate and yttrium adipic acid solution, the reaction is complete. Filter the solution with filter paper. Check the mother liquor after filtration with saturated oxalic acid aqueous solution to see if the precipitation is complete. The ultrasonic frequency is 28 kHz.
[0038] S6: Pour the slurry obtained in step S5 into a small centrifuge for solid-liquid separation. After the mother liquor is dried, add deionized water and turn on the centrifuge for water washing. Stop water washing when the conductivity of the water spun out of the centrifuge is less than 200 S / m. Turn on the centrifuge to dry it thoroughly. After drying, yttrium oxalate is obtained.
[0039] S7: The yttrium oxalate obtained in step S6 is placed into a crucible, which is then placed in a muffle furnace. The muffle furnace is heated from room temperature to 850℃~920℃ for 90~120min, and held for 100~150min. After natural cooling, yttrium oxide powder is obtained. It is then sieved through a 120-mesh standard sieve to obtain high-purity yttrium oxide with a chlorine content of 26ppm, a purity of 99.998%, and a rectangular particle shape. Pure oxygen is introduced into the muffle furnace after it is heated to 500℃ for calcination.
[0040] The high-purity yttrium chloride solution is added in step S2, the liquid alkali solution is added in step S1, and the washed naphthenic acid is added in step S3 by mist spraying.
[0041] In step S1, the naphthenic acid solution is a mixed solution of naphthenic acid, kerosene, and 2-octanol, with a volume ratio of 1:1:3.5.
[0042] Example 2
[0043] A method for preparing rectangular yttrium oxide with low chlorine content includes the following steps:
[0044] S1: Add 6.5L of naphthenic acid solution to the reaction vessel, then add 240ml of 10.8mol / L liquid alkali (sodium hydroxide solution) to carry out the saponification reaction. After the liquid alkali is added, continue the reaction for 5min to obtain the reaction solution.
[0045] S2: Add 1.7 L of 0.5 mol / L high-purity yttrium chloride solution to the reaction solution obtained in step S1, stir for 20 min, release the aqueous phase, and wash the naphthenic acid with pure water until the water conductivity is less than 30 S / m;
[0046] S3: Add 2.17 L of acetic acid solution to the naphthenic acid washed in step S2, turn on the stirrer and back-extract the naphthenic acid for 30 min, and back-extract the yttrium acetate solution. The yttrium acetate molar concentration is 0.35 mol / L, the chlorine content is less than 30 ppm, and the acetic acid concentration is 1.2 mol / L.
[0047] S4: Add the oxalic acid aqueous solution to the ammonia water and stir continuously until the pH value of the solution is 6-8, and then filter to obtain a mixed solution. The concentration of oxalic acid is 6wt%, the concentration of ammonia water is 14mol / L, and the number of moles of oxalic acid is 3.2 times that of yttrium chloride in step S2.
[0048] S5: Add the mixture obtained in step S4 to the ultrasonic synthesis device, and then add it to the yttrium acetate and yttrium adipic acid solution obtained in step S3. Stir under ultrasonic action for 40-80 min at a stirring speed of 140-200 r / min. After adding the yttrium acetate and yttrium adipic acid solution, the reaction is complete. Filter the solution with filter paper. Check the mother liquor after filtration with saturated oxalic acid aqueous solution to see if the precipitation is complete. The ultrasonic frequency is 28 kHz.
[0049] S6: Pour the slurry obtained in step S5 into a small centrifuge for solid-liquid separation. After the mother liquor is dried, add deionized water and turn on the centrifuge for water washing. Stop water washing when the conductivity of the water spun out of the centrifuge is less than 200 S / m. Turn on the centrifuge to dry it thoroughly. After drying, yttrium oxalate is obtained.
[0050] S7: The yttrium oxalate obtained in step S6 is placed into a crucible, which is then placed in a muffle furnace. The muffle furnace is heated from room temperature to 850℃~920℃ for 90~120min, and held for 100~150min. After natural cooling, yttrium oxide powder is obtained. It is then sieved through a 120-mesh standard sieve to obtain high-purity yttrium oxide with a chlorine content of 28ppm, a purity of 99.996%, and a rectangular particle shape. After the muffle furnace is heated to 500℃, pure oxygen is introduced for calcination.
[0051] The high-purity yttrium chloride solution is added in step S2, the liquid alkali solution is added in step S1, and the washed naphthenic acid is added in step S3 by mist spraying.
[0052] In step S1, the naphthenic acid solution is a mixed solution of naphthenic acid, kerosene, and 2-octanol, with a volume ratio of 1:1:3.5.
[0053] Comparative Example 1
[0054] A method for preparing rectangular yttrium oxide with low chlorine content includes the following steps:
[0055] S1: Add 6.5L of naphthenic acid solution to the reaction vessel, then add 240ml of 10.8mol / L liquid alkali (sodium hydroxide solution) to carry out the saponification reaction. After the liquid alkali is added, continue the reaction for 5min to obtain the reaction solution.
[0056] S2: Add 1.7 L of 0.5 mol / L high-purity yttrium chloride solution to the reaction solution obtained in step S1, stir for 20 min, release the aqueous phase, and wash the naphthenic acid with pure water until the water conductivity is less than 30 S / m;
[0057] S3: Add 2.17 L of acetic acid solution to the naphthenic acid washed in step S2, turn on the stirrer and back-extract the naphthenic acid for 30 min, and back-extract the yttrium acetate solution. The yttrium acetate molar concentration is 0.35 mol / L, the chlorine content is less than 30 ppm, and the acetic acid concentration is 1.2 mol / L.
[0058] S4: Add the oxalic acid aqueous solution to the ammonia water and stir continuously until the pH value of the solution is 6-8, and then filter to obtain a mixed solution. The concentration of oxalic acid is 6wt%, the concentration of ammonia water is 14mol / L, and the number of moles of oxalic acid is 3.2 times that of yttrium chloride in step S2.
[0059] S5: Add the mixture obtained in step S4 to the ultrasonic synthesis device, and then add it to the yttrium acetate and yttrium adipic acid solution obtained in step S3. Stir under ultrasonic action for 40-80 min at a stirring speed of 140-200 r / min. After adding the yttrium acetate and yttrium adipic acid solution, the reaction is complete. Filter the solution with filter paper. Check the mother liquor after filtration with saturated oxalic acid aqueous solution to see if the precipitation is complete. The ultrasonic frequency is 28 kHz.
[0060] S6: Pour the slurry obtained in step S5 into a small centrifuge for solid-liquid separation. After the mother liquor is dried, add deionized water and turn on the centrifuge for water washing. Stop water washing when the conductivity of the water spun out of the centrifuge is less than 200 S / m. Turn on the centrifuge to dry it thoroughly. After drying, yttrium oxalate is obtained.
[0061] S7: The yttrium oxalate obtained in step S6 is placed into a crucible, which is then placed in a muffle furnace. The muffle furnace is heated from room temperature to 850℃~920℃ for 90~120min and held for 100~150min. After natural cooling, yttrium oxide powder is obtained. After sieving through a 120-mesh standard sieve, high-purity yttrium oxide with a chlorine content of 31ppm, a purity of 99.991%, and a rectangular particle shape is obtained.
[0062] The high-purity yttrium chloride solution is added in step S2, the liquid alkali solution is added in step S1, and the washed naphthenic acid is added in step S3 by mist spraying.
[0063] In step S1, the naphthenic acid solution is a mixed solution of naphthenic acid, kerosene, and 2-octanol, with a volume ratio of 1:1:3.5.
[0064] Comparative Example 2
[0065] A method for preparing rectangular yttrium oxide with low chlorine content includes the following steps:
[0066] S1: Add 6.5L of naphthenic acid solution to the reaction vessel, then add 240ml of 10.8mol / L liquid alkali (sodium hydroxide solution) to carry out the saponification reaction. After the liquid alkali is added, continue the reaction for 5min to obtain the reaction solution.
[0067] S2: Add 1.7 L of 0.5 mol / L high-purity yttrium chloride solution to the reaction solution obtained in step S1, stir for 20 min, release the aqueous phase, and wash the naphthenic acid with pure water until the water conductivity is less than 30 S / m;
[0068] S3: Add 2.17 L of acetic acid solution to the naphthenic acid washed in step S2, turn on the stirrer and back-extract the naphthenic acid for 30 min, and back-extract the yttrium acetate solution. The yttrium acetate molar concentration is 0.35 mol / L, the chlorine content is less than 30 ppm, and the acetic acid concentration is 1.2 mol / L.
[0069] S4: Add the oxalic acid aqueous solution to the ammonia water and stir continuously until the pH value of the solution is 6-8, and filter to obtain a mixed solution with an oxalic acid concentration of 6wt% and an ammonia water concentration of 14mol / L. The number of moles of oxalic acid is 3.2 times that of yttrium chloride in step S2.
[0070] S5: Add the mixture obtained in step S4 to the ultrasonic synthesis device, and then add it to the yttrium acetate and yttrium adipic acid solution obtained in step S3. Stir under ultrasonic action for 40-80 min at a stirring speed of 140-200 r / min. After adding the yttrium acetate and yttrium adipic acid solution, the reaction is complete. Filter the solution with filter paper. Check the mother liquor after filtration with saturated oxalic acid aqueous solution to see if the precipitation is complete. The ultrasonic frequency is 28 kHz.
[0071] S6: Pour the slurry obtained in step S5 into a small centrifuge for solid-liquid separation. After the mother liquor is dried, add deionized water and turn on the centrifuge for water washing. Stop water washing when the conductivity of the water spun out of the centrifuge is less than 200 S / m. Turn on the centrifuge to dry it thoroughly. After drying, yttrium oxalate is obtained.
[0072] S7: The yttrium oxalate obtained in step S6 is placed into a crucible, which is then placed in a muffle furnace. The muffle furnace is heated from room temperature to 850℃~920℃ for 90~120min, and held for 100~150min. After natural cooling, yttrium oxide powder is obtained. It is then sieved through a 120-mesh standard sieve to obtain high-purity yttrium oxide with a chlorine content of 32ppm, a purity of 99.89%, and a rectangular particle shape. After the muffle furnace is heated to 500℃, pure oxygen is introduced for calcination.
[0073] The high-purity yttrium chloride solution in step S2, the liquid alkali solution in step S1, and the washed naphthenic acid in step S3 are all added directly, without spraying.
[0074] In step S1, the naphthenic acid solution is a mixed solution of naphthenic acid, kerosene, and 2-octanol, with a volume ratio of 1:1:3.5.
[0075] The experimental data above show that the rectangular high-purity yttrium chloride prepared in Examples 1 and 2 of this invention has a content of less than 30 ppm and a purity greater than 99.99%. In step S3 of Example 1, the use of a mixed solution of acetic acid and adipic acid resulted in better performance, higher product purity, and lower chlorine content. In Comparative Example 1, step S7 did not use pure oxygen calcination, leading to a decrease in product quality. In Comparative Example 2, the addition of the high-purity yttrium chloride solution in step S2, the addition of the liquid alkali solution in step S1, and the addition of the washed naphthenic acid in step S3 were all direct additions without spraying, resulting in a decrease in product quality.
Claims
1. A method for preparing rectangular yttrium oxide with low chlorine content, characterized in that: The following steps are involved: S1: adding a mixed solution of cyclohexane acid, kerosene and octanol into a reaction container, and then adding liquid alkali to carry out saponification reaction. After the addition of the liquid alkali, the reaction is continued for 5 minutes to obtain a reaction solution, wherein the volume ratio of the cyclohexane acid, kerosene and octanol is 1:1:3.5, the concentration of the liquid alkali is 10.8 mol / L, and the volume ratio of the liquid alkali to the mixed solution is 325:12; S2: adding high-purity yttrium chloride solution to the reaction solution obtained in step S1, stirring for 20 minutes, releasing the aqueous phase, and washing the cyclopentane acid with pure water until the drainage conductivity is less than 30 S / m; S3: adding the prepared mixed solution of acetic acid and adipic acid to the cyclohexane acid washed in step S2, stirring, and stripping for 30 minutes to separate yttrium acetate and yttrium adipate solutions, wherein the molar concentration of yttrium acetate is 0.2-0.4 mol / L, the molar concentration of yttrium adipate is 0.01-0.03 mol / L, and the chlorine content is less than 30 ppm; S4: adding the oxalic acid aqueous solution to the ammonia water, stirring continuously until the pH value of the solution is 6-8, and filtering to obtain a mixed solution; S5: adding the mixed solution obtained in step S4 to an ultrasonic synthesis device, and then adding the yttrium acetate and yttrium adipate solutions obtained in step S3, stirring for 40 to 80 minutes under the action of ultrasound, and the stirring speed is 140 to 200 r / min. After the yttrium acetate and yttrium adipate solutions are added, the reaction is complete, and the mixture is filtered with filter paper. The mother liquor after filtration is checked with a saturated oxalic acid aqueous solution to see if it is completely precipitated; S6: pouring the slurry obtained by the reaction in step S5 into a small centrifuge for solid-liquid separation, adding deionized water after drying the mother liquor, turning on the centrifuge for water washing, and stopping the water washing until the conductivity of the water thrown out by the centrifuge is less than 200 S / m, turning on the centrifuge for sufficient drying, and obtaining yttrium oxalate after drying; S7: the yttrium oxalate obtained in step S6 is loaded into a crucible, the crucible is placed in a muffle furnace, the muffle furnace is heated from room temperature to 850°C-920°C, the heating time is 90-120 min, the heat preservation time is 100-150 min, and the yttrium oxide powder is obtained after natural cooling, and the powder is sieved through a 120-mesh standard sieve to obtain a high-purity yttrium oxide with a chlorine content of less than 30 ppm, a purity of more than 99.99%, and a rectangular particle shape; The method of adding the high-purity yttrium chloride solution in step S2, the method of adding the liquid alkali solution in step S1 and the method of adding the washed cyclopentane acid in step S3 are all mist spray addition; In step S7, after the muffle furnace is heated to 500° C., pure oxygen is introduced for calcination; In the step S3, the concentration of acetic acid in the mixed solution of acetic acid and adipic acid is 1-1.5 mol / L, and the concentration of adipic acid is 0.02-0.2 mol / L.
2. The method for preparing rectangular yttrium oxide with low chlorine content according to claim 1, characterized in that: The concentration of the high-purity yttrium chloride solution in step S2 is 0.5 mol / L, and the volume ratio of the high-purity yttrium chloride solution to the mixed solution of cyclohexane acid, kerosene and octanol in step S1 is 1:3.
8.
3. The method for preparing rectangular yttrium oxide with low chlorine content according to claim 1, characterized in that: In step S4, the concentration of oxalic acid is 5-8 wt %, the concentration of ammonia water is 12.0-14.0 mol / L, and the molar number of oxalic acid is 3.2 times that of yttrium chloride in step S2.
4. The method for preparing rectangular yttrium oxide with low chlorine content according to claim 1, characterized in that: The volume ratio of the washed cyclohexane acid to the mixed solution of acetic acid and adipic acid in step S3 is 3:
1.
5. The method for preparing rectangular yttrium oxide with low chlorine content according to claim 1, characterized in that: The ultrasonic frequency in step S5 is 28 kHz.