Lanthanum cerium oxyfluoride polishing powder, precision polishing cerium-based rare earth polishing solution and preparation method of precision polishing cerium-based rare earth polishing solution

Abstract

The invention discloses cerium lanthanum oxyfluoride polishing powder, a precision polishing cerium-based rare earth polishing solution and a preparation method thereof, and relates to the field of polishing materials. The preparation method of the polishing powder comprises the following steps: preparing lanthanum chloride cerium blending liquid, and regulating and controlling the concentration and proportion of lanthanum chloride and cerium chloride; after dilution, adding a composite precipitant, stirring and precipitating, wherein the composite precipitant comprises sodium fluoride, sodium phosphate, sodium carbonate and water; and then carrying out firing treatment to obtain the lanthanum cerium oxyfluoride. According to the preparation method, the concentration and proportion of lanthanum chloride and cerium chloride in a precursor are adjusted, meanwhile, a lanthanum cerium fluorocarbonate filter cake is added as a seed crystal, and a composite precipitator is added for precipitation and fluorination, so that the crystal structure of the polishing powder is microcosmically changed, an acute octahedron or a cube is converted into a truncated octahedron, and the initial grain size is reduced; due to the arrangement of a firing curve, coarse grains can be avoided, particles are uniformly distributed, and scratches and roughness of a polished sample can be reduced when a subsequent polishing solution is applied to polishing of an STN or ITO material.

Description

Technical Field

[0001] The present invention relates to the field of polishing materials, and particularly to a lanthanum cerium oxyfluoride polishing powder, a precision polishing cerium-based rare earth polishing liquid, and a preparation method thereof. Background Art

[0002] STN (Super Twisted Nematic) liquid crystal displays and ITO (Indium Tin Oxide) transparent conductive films are important materials in the field of electronic displays. STN liquid crystal glass substrates need to undergo high-precision chemical mechanical polishing (CMP) treatment to ensure surface flatness, smoothness, and transparency; ITO films are usually deposited on glass or flexible substrates through processes such as magnetron sputtering, and their surface quality directly affects the electrical and optical properties of the devices. The substrate glass needs to undergo high-precision polishing treatment to ensure high-quality deposition of the ITO film. As a precursor of rare earth polishing powder, lanthanum cerium carbonate can be converted into high-performance polishing powder through specific processes such as fluorination, calcination, and classification treatment, which can be used for polishing STN, ITO, etc., and can improve surface flatness and optical properties.

[0003] The main manufacturer of lanthanum cerium carbonate is China National Rare Earths High-Tech Co., Ltd., and its products meet the requirements of the national standard GB / T 16479-2020. There are no specific requirements for the morphology and particle size of lanthanum cerium carbonate in the national standard. At present, the production process of lanthanum cerium carbonate is extensive, the initial grain size is large, and the macroscopic particle morphology is uneven. If the lanthanum cerium carbonate with a large size and uneven morphology is directly used as a raw material to produce polishing powder, the produced polishing powder particles are uneven and prone to scratching during the polishing of STN and ITO.

[0004] In addition, the main production process of polishing powder in China at present is to add water to the purchased lanthanum cerium carbonate to make a slurry, and after precipitation with a precipitant, it is fluorinated with hydrofluoric acid. In this fluorination process, it is a solid-liquid reaction, the reaction is uneven, and the crystal form and morphology are not controlled during the production process. Therefore, the produced polishing powder has uneven particles, large differences in morphology, and composition segregation, and can only be applied to the rough polishing of the edges of ordinary glass, and is not suitable for fine polishing or ultra-fine polishing of STN and ITO. Summary of the Invention

[0005] The present invention provides a lanthanum cerium oxyfluoride polishing powder, a precision polishing cerium-based rare earth polishing liquid, and a preparation method thereof to improve the crystal morphology of the polishing powder, make the surface of the polishing powder particles smooth, and the particle size smaller, which can reduce scratches on the sample during the polishing process.

[0006] To solve the above technical problems, one of the objectives of the present invention is to provide a preparation method of a lanthanum cerium oxyfluoride polishing powder, including the following steps:

[0007] (1) Mix the lanthanum chloride solution and the cerium chloride solution to prepare a lanthanum cerium chloride blending solution, and control the La2O3 / REO in the lanthanum cerium chloride blending solution to be 29%-31%, and Ce2O3 / REO to be 69%-71%.

[0008] (2) Add water and the lanthanum cerium chloride blending solution to a reaction kettle, stir and heat to 60-80°C, add the lanthanum cerium fluorocarbonate filter cake produced in the previous cycle batch, and the proportion of the lanthanum cerium fluorocarbonate filter cake in the system is 2wt%-10wt%. Control the total concentration of lanthanum chloride and cerium chloride in the system solution to be 50-200g / L, then add a composite precipitant and stir for aging. Monitor the pH of the solution in real time. When the pH of the solution remains at 6-8, stop adding the composite precipitant, wash and filter to obtain the lanthanum cerium fluorocarbonate filter cake.

[0009] The composite precipitant includes sodium fluoride with a mass fraction of 1wt%-3wt%, sodium phosphate with a mass fraction of 0.5wt%-2wt%, sodium carbonate with a mass fraction of 5wt%-10wt% and the balance of water.

[0010] (3) Calcinate the lanthanum cerium fluorocarbonate filter cake, raise the temperature to 490-510°C and keep it warm for 3-8h, then raise the temperature to 940-960°C and keep it warm for 1-5h, and obtain lanthanum cerium oxyfluoride after cooling.

[0011] In the production process of polishing powder in this application, the crystal morphology is controlled. The concentration and ratio of lanthanum chloride and cerium chloride are adjusted by using the lanthanum chloride and cerium chloride solutions after activation by chlorination treatment. At the same time, the lanthanum cerium fluorocarbonate filter cake is added as a seed crystal, and a composite precipitant is added for liquid-liquid reaction, improving the fluorination synthesis method, enhancing the particle uniformity, and facilitating the control of the fluorination process. Microscopically, the crystal structure of the polishing powder is changed from an acute octahedron or cube to a truncated octahedron, reducing the initial grain size. A calcination temperature curve is formulated, and the calcination process is carried out according to the setting of dehydration (crystal water and free water), carbonate decomposition, and oxide crystallization, which can avoid coarse grains. Macroscopically, the particle distribution is uniform. When it is applied to the preparation of STN and ITO polishing solutions, the scratches on the polished samples can be controlled within an acceptable range.

[0012] As a preferred solution, in step (1), the preparation methods of the lanthanum chloride solution and the cerium chloride solution are as follows: Dissolve and mix lanthanum carbonate and cerium carbonate with hydrochloric acid with a concentration of 1-5mol / L, filter through a 300-500 mesh sieve, and control the pH of the solution to be 0.5-4.5.

[0013] As a preferred solution, in step (1), the concentration of the solute in the lanthanum chloride solution and the cerium chloride solution is 200-400g / L.

[0014] As a preferred solution, in step (2), the lanthanum cerium fluorocarbonate filter cake produced in the previous cycle batch is specifically the lanthanum cerium fluorocarbonate filter cake obtained in step (2) of the previous cycle batch. The lanthanum cerium fluorocarbonate filter cake produced in the first batch is directly used in the second batch process, and lanthanum cerium oxyfluoride is prepared starting from the second batch.

[0015] As a preferred solution, in step (2), the addition rate of the composite precipitant is 3 - 8 mL / min, and the stirring and aging time is 1 - 3 h.

[0016] As a preferred solution, in step (2), when the solution maintains a pH of 6 - 8 for 5 - 15 min, the addition of the composite precipitant is stopped.

[0017] As a preferred solution, in step (2), the washing is carried out by stirring and washing with pure water for 1 - 3 h, then standing for 2 - 5 h, separating the supernatant, and repeating the washing 3 - 6 times.

[0018] As a preferred solution, in step (2), the filtration is carried out by suction filtration using filter paper.

[0019] As a preferred solution, in step (3), the heating rate of the lanthanum cerium fluorocarbonate filter cake when heated to 490 - 510 °C is 4 - 6 °C / min, and the cooling rate when heated to 940 - 960 °C is 2 - 3 °C / min.

[0020] To solve the above technical problems, the second object of the present invention is to provide a lanthanum cerium oxyfluoride polishing powder.

[0021] To solve the above technical problems, the third object of the present invention provides a precision polishing cerium-based polishing liquid, comprising lanthanum cerium oxyfluoride polishing powder, sodium polyacrylate, sodium hexametaphosphate, rheology aid, bactericide, pH regulator, and the balance of water.

[0022] As a preferred solution, the particle size D50 of the lanthanum cerium oxyfluoride polishing powder is 5 - 8 μm.

[0023] As a preferred solution, the sodium polyacrylate is 1 wt% - 4 wt% of the mass fraction of the lanthanum cerium oxyfluoride polishing powder.

[0024] As a preferred solution, the sodium hexametaphosphate is 0.3 wt% - 0.8 wt% of the mass fraction of the lanthanum cerium oxyfluoride polishing powder.

[0025] As a preferred solution, the rheology aid is 0.5 wt% - 2 wt% of the mass fraction of the lanthanum cerium oxyfluoride polishing powder.

[0026] As a preferred solution, the bactericide is 0.1 wt% - 0.3 wt% of the mass fraction of the lanthanum cerium oxyfluoride polishing powder.

[0027] As a preferred embodiment, the mass fraction concentration of the lanthanum cerium oxyfluoride polishing powder in the polishing liquid is 5wt%-50wt%.

[0028] As a preferred embodiment, the pH regulator adjusts the pH of the polishing liquid to 10-14.

[0029] As a preferred embodiment, the pH regulator is K2HPO4 and / or KOH.

[0030] As a preferred embodiment, the pH regulator comprises K2HPO4 and KOH with a mass ratio of 10:(1-2).

[0031] As a preferred embodiment, the bactericide is an isothiazolinone compound.

[0032] To solve the above technical problems, a fourth object of the present invention is to provide a method for preparing a precision polishing cerium-based polishing liquid, comprising the following steps:

[0033] (1) Mix lanthanum cerium oxyfluoride, water and sodium polyacrylate and perform wet grinding treatment. At this time, the sodium polyacrylate is 0.5wt%-2wt% of the mass fraction of lanthanum cerium oxyfluoride, and the mass ratio of lanthanum cerium oxyfluoride to water is 1:(1-2). Grind until the particle size D50 of the slurry is less than 0.16μm and the particle size D100 is less than 0.5μm, and filter through a sieve after grinding;

[0034] (2) Add the remaining sodium polyacrylate, sodium hexametaphosphate, rheological aid and bactericide to the slurry in sequence, dilute with water, stir evenly, add a pH regulator to adjust the pH to 10-14, stir evenly and then filter to obtain the polishing liquid.

[0035] As a preferred embodiment, in step (1), filter with a 400-600 mesh sieve.

[0036] As a preferred embodiment, in step (2), filter with a 0.5μm PALL filter bag.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] In the production process of the polishing powder of the present application, the concentration and ratio of lanthanum chloride and cerium chloride in the precursor are adjusted by using the lanthanum chloride and cerium chloride solutions activated by chlorination treatment. At the same time, lanthanum cerium fluorocarbonate is added as a seed crystal, and a composite precipitant is added for liquid-liquid reaction to improve the fluorination synthesis method and control the fluorination process. It can microscopically change the crystal structure of the polishing powder from an acute octahedron or cube to a truncated octahedron, reduce the initial grain size; the formulated calcination temperature curve can avoid coarse grains and the particle distribution is uniform. After being prepared into a polishing liquid subsequently, it can be applied to the fine polishing of STN and ITO materials, and significantly reduce the scratches and roughness of the polished samples. Description of the Drawings

[0039] Figure 1 : XRD pattern of lanthanum cerium oxyfluoride prepared in step (6) of Example 1 of the present invention;

[0040] Figure 2 : SEM image of lanthanum cerium oxyfluoride prepared in step (6) of Example 1 of the present invention;

[0041] Figure 3 : SEM image of lanthanum cerium oxyfluoride prepared in step (6) of Comparative Example 1 of the present invention;

[0042] Figure 4 : SEM image of lanthanum cerium oxyfluoride prepared in step (6) of Comparative Example 2 of the present invention;

[0043] Figure 5 : SEM image of lanthanum cerium oxyfluoride prepared in step (6) of Comparative Example 3 of the present invention;

[0044] Figure 6 : SEM image of lanthanum cerium oxyfluoride prepared in step (6) of Comparative Example 4 of the present invention;

[0045] Figure 7 : Results of detecting the surface roughness of the sample after the polishing test of the polishing liquid prepared in Example 1 of the present invention. Detailed Description of the Invention

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0048] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0049] To further illustrate the present invention, the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention. The following Table 1 shows the sources of raw materials used in the examples and comparative examples of this application. Unless otherwise specified, the raw materials used can be obtained commercially, and the same raw materials are used in parallel experiments.

[0050] Table 1 - Information of Raw Materials Used in Examples and Comparative Examples of This Application

[0051]

[0052] Example 1

[0053] A preparation method of a precision polishing cerium-based rare earth polishing liquid, comprising the following steps:

[0054] (1) Place lanthanum carbonate and cerium carbonate in two beakers respectively, slowly add a hydrochloric acid aqueous solution with a concentration of 3 mol / L. After the carbonates are completely dissolved, obtain a lanthanum chloride solution and a cerium chloride solution respectively. Control the concentrations of lanthanum chloride and cerium chloride generated in the solution to be 300 g / L. Test the pH with a pH test paper to be about 1.5. Filter the above two chlorides through a 400-mesh sieve respectively, and then mix the lanthanum chloride solution and the cerium chloride solution to prepare a lanthanum cerium chloride blending solution. Control the total concentration of lanthanum chloride and cerium chloride in the lanthanum cerium chloride blending solution to be 300 g / L, and La2O3 / REO = 30% ± 1%, Ce2O3 / REO = 70% ± 1%;

[0055] (2) Add 3125 mL of pure water to a jacketed reactor, turn on the stirrer and the water bath circulation heater, control the temperature to reach and maintain at 72 ± 1 °C, add 62.5 g of sodium fluoride and 46.9 g of sodium phosphate, stir for 1 h, then add 312.5 g of sodium carbonate, stir for 1 h, add pure water to make up to 4060 mL, and filter through a 200-mesh filter to obtain a composite precipitant;

[0056] (3) Add 300 mL of pure water to the glass reactor, start stirring, add 50 g of the cerium lanthanum fluorocarbon filter cake produced in the previous batch of cyclic production as seeds, start the water bath circulation heater, control the temperature to be maintained at 72 ± 1 °C, add 656 mL of cerium lanthanum chloride preparation solution, and add pure water to dilute until the total concentration of cerium lanthanum chloride is 100 g / L ± 5 g / L. Insert a pH meter probe of model InPro4800 / 120 / PT1000 into the glass reactor, and add a composite precipitant to the glass reactor by a peristaltic pump. The flow rate of the composite precipitant is 5 mL / min. When the pH meter detects that the solution in the glass reactor maintains a pH of 6 within 10 min, turn off the addition of the composite precipitant in the peristaltic pump, continue stirring for 1 h, and then let it stand and clarify for 3 h;

[0057] (4) Siphon the supernatant in the glass reactor, add 3500 mL of pure water, start stirring and the water bath circulation heater, control the temperature to reach and be maintained at 72 ± 1 °C, stir for 2 h, let it stand and clarify for 3 h, and repeat this step four times;

[0058] (5) Start stirring for 0.5 h, filter the slurry in the glass reactor through filter paper in a Buchner funnel, with a vacuum degree of < 0.05 MPa, and filter for 6 h to obtain the cerium lanthanum fluorocarbon filter cake. Detect its particle size D(50) to be 5 - 8 μm, which can enter the next process, and its validity period is two weeks;

[0059] (6) Put 500 g of the cerium lanthanum fluorocarbon filter cake into a porcelain dish, place it in a muffle furnace for calcination. Heat it from room temperature to 500 °C in 1.5 h, hold for 5 h, heat it to 950 °C in 2 h, hold for 3.5 h, and cool it to room temperature along with the furnace cooling in 5.5 h to obtain cerium lanthanum oxyfluoride (REOF);

[0060] (7) Mix cerium lanthanum oxyfluoride and pure water in a mass ratio of 1:1.5, stir for 4 h, then filter through a 100 - mesh sieve, add an aqueous solution of sodium polyacrylate (PAAS) with a concentration of 30 wt%, and the sodium polyacrylate is 1.67% of the mass fraction of REOF, and stir for 2 h to obtain a slurry;

[0061] (8) Wet - grind the slurry, load grinding beads into the sand mill, with the sand mill frequency at 45 Hz. After grinding, filter through a 500 - mesh sieve. The particle size D(50) of the slurry after grinding is less than 0.16 μm, and the particle size D(100) is less than 0.5 μm;

[0062] (9)Dilute the slurry by adding lanthanum cerium oxyfluoride at a ratio of 30 wt%, start stirring, and add a polyacrylate sodium (PAAS) solution with a concentration of 30 wt%. At this time, the added polyacrylate sodium is 1.11% of the mass fraction of REOF. Stir for 0.5 h, add sodium hexametaphosphate (HMP) at 0.5% of the mass fraction of REOF, stir for 0.5 h, add Laponite-RD rheological aid at 1% of the mass fraction of REOF, stir for 1 h, add SA++ fungicide at 0.17% of the mass fraction of REOF, stir for 0.5 h, add a mixed solution of K2HPO4 and potassium hydroxide with a mass ratio of 10:1 to adjust the pH to 12, stir for 1 h, filter with a 1 μm sieve, and then filter with a 0.5 μm PALL filter bag to obtain the polishing liquid.

[0063] Among them, the lanthanum cerium fluorocarbonate filter cake produced in the previous cycle batch in step (3) is specifically the lanthanum cerium fluorocarbonate filter cake obtained in step (5) of the previous cycle batch. The lanthanum cerium fluorocarbonate filter cake produced in the first batch is directly used in the second batch process, and lanthanum cerium oxyfluoride is prepared starting from the second batch.

[0064] Comparative Example 1

[0065] A preparation method of a precision polishing cerium-based rare earth polishing liquid, where each step, the reagents, equipment, and process parameters used in each step are the same as those in Example 1. The difference lies in that in step (3), 50 g of the lanthanum cerium fluorocarbonate filter cake produced in the previous batch cycle is replaced with 50 mL of a lanthanum cerium chloride preparation liquid with a concentration of 300 g / L in an equal amount.

[0066] Comparative Example 2

[0067] A preparation method of a precision polishing cerium-based rare earth polishing liquid, where each step, the reagents, equipment, and process parameters used in each step are the same as those in Example 1. The difference lies in that in step (1), lanthanum carbonate and cerium carbonate are placed in two beakers respectively, and a hydrochloric acid aqueous solution with a concentration of 3 mol / L is slowly added. After the carbonates are completely dissolved, a lanthanum chloride solution and a cerium chloride solution are obtained respectively. Control the concentrations of lanthanum chloride and cerium chloride generated in the solution to be 300 g / L. Use a pH test paper to test the pH to be about 1.5. Filter the above two chlorides with a 400-mesh sieve respectively, and then mix the lanthanum chloride solution and the cerium chloride solution to prepare a lanthanum cerium chloride preparation liquid. Control the total concentration of lanthanum chloride and cerium chloride in the lanthanum cerium chloride preparation liquid to be 300 g / L, and La2O3 / REO = 40% ± 1%, Ce2O3 / REO = 60% ± 1%.

[0068] Comparative Example 3

[0069] A preparation method of a precision polishing cerium-based rare earth polishing liquid, where each step, the reagents, equipment, and process parameters used in each step are the same as those in Example 1. The difference lies in that in step (6), 500 g of lanthanum cerium fluorocarbonate filter cake is dried and then placed in a porcelain dish, which is then placed in a muffle furnace and calcined. It is heated from room temperature to 950 °C in 3 h, maintained for 3.5 h, and cooled to room temperature with the furnace cooling in 5.5 h to obtain lanthanum cerium oxyfluoride.

[0070] Comparative Example 4

[0071] A preparation method of a precision polishing cerium-based rare earth polishing liquid, where each step, the reagents, equipment, and process parameters used in each step are the same as those in Example 1. The difference lies in that in step (2), sodium phosphate is replaced with an equal amount of sodium carbonate.

[0072] Performance detection test

[0073] 1. The lanthanum cerium oxyfluoride prepared after calcination in step (6) of the examples and comparative examples was observed by scanning electron microscope. The SEM image of lanthanum cerium oxyfluoride in Example 1 is as shown in the appendix Figure 2 shown. The particle morphology is approximately a truncated octahedron, the particles are uniform and have a small particle size, and the dispersibility is good. The SEM image of lanthanum cerium oxyfluoride in Comparative Example 1 is as shown in the appendix Figure 3 shown. The particle morphology of lanthanum cerium oxyfluoride varies greatly, the particles are uneven, and it is easy to cause scratches during the polishing process. The SEM image of lanthanum cerium oxyfluoride in Comparative Example 2 is as shown in the appendix Figure 4 shown. The agglomeration is serious, and it is easy to cause scratches during the polishing process. The SEM image of lanthanum cerium oxyfluoride in Comparative Example 3 is as shown in the appendix Figure 5 shown. The initial crystal grains are large, and the morphology is approximately a cube. The SEM image of lanthanum cerium oxyfluoride in Comparative Example 4 is as shown in the appendix Figure 6 shown. The particles are agglomerated, and the morphology is flaky.

[0074] 2. Using a laser particle size analyzer, the particle size D(50) of the lanthanum cerium oxyfluoride prepared in step (6) of the examples and comparative examples was tested, and the test results are shown in Table 2.

[0075] 3. The polishing liquids prepared in the examples and comparative examples were used to polish STN glass with a UNIPOL-1203 type polishing machine, and the roughness was tested using an atomic force microscope. The test results are as shown in the appendix Figure 7 and Table 2.

[0076] Among them, the polishing conditions are specifically: glass model: STN, polishing pad: LP66, lower disk rotation speed: 150 rpm, swing arm speed: 10 gears, axial stroke of the sample carrier: 8 mm, pressure of the sample carrier: 0.15 kg, feeding flow rate: 20 ml / min.

[0077] Table 2 - Roughness results obtained from the polishing tests of the polishing fluids in the examples and comparative examples

[0078] Test item Lanthanum cerium oxyfluoride D(50) Roughness Ra Example 1 6.92μm 0.484 Comparative example 1 10.83μm 0.586 Comparative example 2 13.11μm 0.591 Comparative example 3 8.59μm 0.576 Comparative example 4 14.38μm 0.608

[0079] In Example 1 of the present application, lanthanum carbonate and cerium carbonate were pre - treated by chlorination for activation. Subsequently, the concentrations and ratios of lanthanum chloride and cerium chloride were adjusted. Meanwhile, lanthanum cerium fluorocarbonate filter cake was added as a seed crystal, which could carry out liquid - liquid reaction with the composite precipitant and age. By improving the fluorination synthesis method, it was beneficial to control the fluorination process, improve the uniformity of particles, and microscopically change the crystal morphology of the polishing powder from an acute - angled octahedron or cube to a truncated octahedron, reducing the initial grain size. Subsequently, it was calcined according to the formulated temperature curve, and the calcination process was carried out according to the settings of dehydration, carbonate decomposition, and oxide crystallization, which could avoid the coarsening of grains and macroscopically ensure the uniform particle distribution. It could be applied to the preparation of STN and ITO polishing fluids, reducing the roughness of the polishing interface.

[0080] As shown in Table 2 and Figure 3 as shown, compared with Example 1, in Comparative Example 1, the lanthanum cerium fluorocarbonate filter cake as the seed crystal was replaced by a lanthanum cerium chloride preparation solution. Due to the absence of a seed crystal, the initial grains of the generated polishing powder increased, and the particles were uneven, which easily scratched the polishing interface of the sample during the polishing process, resulting in a higher roughness of the polishing interface of the STN sample.

[0081] As shown in Table 2 and Figure 4 as shown, compared with Example 1, in Comparative Example 2, the ratio of lanthanum chloride to cerium chloride in the lanthanum cerium chloride preparation solution was 4:6, and the proportion of lanthanum chloride was too high, resulting in serious agglomeration of the polishing powder and uneven particles, which easily scratched the polishing interface of the sample during the polishing process, leading to a higher roughness of the polishing interface.

[0082] As shown in Table 2 and Figure 5 as shown, compared with Example 1, in Comparative Example 3, lanthanum cerium fluorocarbonate was calcined directly at 950 °C for 3.5 h, and the calcination process did not follow the order of dehydration, carbonate decomposition, and oxide crystallization. The calcination process led to coarsened grains, a morphology similar to a cube, and uneven particle distribution, affecting the subsequent polishing of STN glass and resulting in a higher roughness of the polishing interface.

[0083] As shown in Table 2 and Figure 6 as shown, sodium phosphate was added to the composite precipitant in Example 1, and the phosphorus element could further refine the grains during the precipitation process. Compared with Example 1, in Comparative Example 4, sodium carbonate was used to replace sodium phosphate in the composite precipitant, and no phosphorus element was introduced. Therefore, the initial grain edges and corners were distinct during growth, which easily scratched the polishing interface of the sample during the polishing process, resulting in a higher roughness of the polishing interface.

[0084] The specific embodiments described above further elaborate on the object, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. In particular, for those skilled in the art, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of lanthanum cerium oxyfluoride polishing powder, characterized in that, It includes the following steps: (1) Mix a lanthanum chloride solution and a cerium chloride solution to prepare a lanthanum cerium chloride blending solution, controlling La2O3 / REO = 29% - 31% and Ce2O3 / REO = 69% - 71% in the lanthanum cerium chloride blending solution; (2) Add water and the lanthanum cerium chloride blending solution to a reaction kettle, stir and heat to 60 - 80 °C, add the lanthanum cerium fluorocarbonate filter cake produced in the previous cycle batch, with the proportion of the lanthanum cerium fluorocarbonate filter cake in the system being 2wt% - 10wt%, control the total concentration of lanthanum chloride and cerium chloride in the system solution to be 50 - 200 g / L, then add a composite precipitant and stir for precipitation and aging. Monitor the pH of the solution in real time. When the solution maintains a pH of 6 - 8, stop adding the composite precipitant, wash and filter to obtain a lanthanum cerium fluorocarbonate filter cake; The composite precipitant includes sodium fluoride with a mass fraction of 1wt% - 3wt%, sodium phosphate with a mass fraction of 0.5wt% - 2wt%, sodium carbonate with a mass fraction of 5wt% - 10wt% and the balance of water; (3) Calcinate the lanthanum cerium fluorocarbonate filter cake, heat up to 490 - 510 °C and hold for 3 - 8 h, heat up to 940 - 960 °C and hold for 1 - 5 h, and obtain lanthanum cerium oxyfluoride after cooling.

2. The preparation method of the cerium lanthanum fluoride oxide polishing powder according to claim 1, characterized in that, In step (1), the preparation methods of the lanthanum chloride solution and the cerium chloride solution are as follows: Dissolve and mix lanthanum carbonate and cerium carbonate with hydrochloric acid with a concentration of 1 - 5 mol / L respectively, filter through a sieve, and control the pH of the solution to be 0.5 - 4.

5.

3. The preparation method of the lanthanum cerium fluoroxide polishing powder according to claim 1, characterized in that, In step (2), the addition rate of the composite precipitant is 3 - 8 mL / min, and the stirring precipitation and aging time is 1 - 3 h; And / or, in step (2), the washing is to stir and wash with pure water for 1 - 3 h, then let it stand for 2 - 5 h, separate the supernatant, and repeat the washing 3 - 6 times; And / or, in step (2), the filtration is by suction filtration using filter paper.

4. The preparation method of the lanthanum cerium fluoroxide polishing powder according to claim 1, characterized in that, In step (3), the heating rate of the lanthanum cerium fluorocarbonate filter cake when heating up to 500 °C is 4 - 6 °C / min, and the cooling rate when heating up to 950 °C is 2 - 3 °C / min.

5. A lanthanum cerium oxyfluoride polishing powder prepared by the preparation method of the lanthanum cerium oxyfluoride polishing powder according to any one of claims 1 - 4.

6. A precision polishing cerium-based polishing liquid, characterized in that, Using the lanthanum cerium oxyfluoride polishing powder according to claim 5, it includes lanthanum cerium oxyfluoride polishing powder, sodium polyacrylate, sodium hexametaphosphate, a rheology aid, a bactericide, a pH regulator and the balance of water.

7. The precision polishing cerium-based polishing liquid according to claim 6, wherein The particle size D50 of the lanthanum cerium oxyfluoride polishing powder is 5 - 8 μm.

8. The precision polishing cerium-based polishing liquid according to claim 6, wherein, The sodium polyacrylate is 1wt% - 4wt% of the mass fraction of the lanthanum cerium oxyfluoride polishing powder; And / or, the sodium hexametaphosphate is 0.3wt% - 0.8wt% of the mass fraction of the lanthanum cerium oxyfluoride polishing powder; And / or, the rheology aid is 0.5wt% - 2wt% of the mass fraction of the lanthanum cerium oxyfluoride polishing powder; And / or, the bactericide is 0.1wt% - 0.3wt% of the mass fraction of the lanthanum cerium oxyfluoride polishing powder; And / or, the mass fraction concentration of the lanthanum cerium oxyfluoride polishing powder in the polishing liquid is 5wt% - 50wt%.

9. The precision polishing cerium-based polishing liquid according to claim 6, wherein The pH regulator adjusts the pH of the polishing liquid to 10 - 14; And / or, the pH regulator is K2HPO4 and / or KOH.

10. A method for preparing a precision polishing cerium-based polishing liquid according to any one of claims 6-9, characterized in that, It includes the following steps: (1) Mix lanthanum cerium oxyfluoride, water and sodium polyacrylate and then conduct wet grinding treatment. At this time, the sodium polyacrylate is 0.5wt%-2wt% of the mass fraction of lanthanum cerium oxyfluoride. The mass ratio of lanthanum cerium oxyfluoride to water is 1:(1-2). Grind until the particle size D50 of the slurry is less than 0.16μm and the particle size D100 is less than 0.5μm. After grinding, filter with a 400-600 mesh sieve; (2) Add the remaining sodium polyacrylate, sodium hexametaphosphate, rheology aid and bactericide to the slurry, dilute with water, stir evenly, add a pH regulator to adjust the pH to 10-14, stir evenly and then filter to obtain the polishing liquid.

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