Oxalate barium titanate powder with high purity and a preparation method thereof

Abstract

The present application relates to a kind of oxalate high-purity barium titanate powder and its preparation method, which comprises six steps of titanium salt stabilizing liquid preparation, barium salt solution preparation, dispersant modification liquid preparation, dispersant synergistic homogeneous precipitation reaction, microwave drying purification and microwave gradient calcination.The purity of barium titanate powder prepared by the present application is ≥99.9%, the average particle size is 30-60nm, the agglomerate content is ≤1.5%, and the dielectric performance is excellent.The present application can be widely applied to high-end electronic components such as multilayer ceramic capacitor, and the process is stable and controllable, easy to industrial production.

Description

A high-purity barium titanate oxalate powder and its preparation method Technical Field

[0001] This invention belongs to the field of electronic ceramic materials technology, specifically relating to a high-purity barium titanate oxalate powder and its preparation method. Background Technology

[0002] Barium titanate, a typical perovskite-structured ferroelectric material, possesses excellent dielectric, piezoelectric, and ferroelectric properties, making it an indispensable basic functional material in the electronics and information industry. It is widely used in MLCCs, thermistors, piezoelectric ceramics, and other fields. With the miniaturization and high integration of electronic devices, higher performance requirements are being placed on barium titanate powder. It not only needs extremely high purity (impurity content below 100 ppm) but also requires fine particle size (≤100 nm), excellent dispersibility, and complete crystal structure.

[0003] Currently, the main methods for preparing barium titanate powder include solid-state method, sol-gel method, hydrothermal method, and oxalate method. Among them, the oxalate method has become one of the commonly used methods in industrial production due to its advantages such as low raw material cost, easy scaling up of the process, and high product purity. Its core principle is to react barium salt and titanium salt in solution to generate barium titanate precursor—barium oxalate oxytitanium—which is then calcined and decomposed to obtain barium titanate powder.

[0004] However, the traditional oxalate method still faces many bottlenecks in practical applications: First, during the precursor preparation process, titanium salts are prone to hydrolysis, generating impurities that reduce product purity and affect subsequent dielectric properties. Second, uneven ion diffusion in the reaction system easily leads to the formation of precursor particles with wide particle size distribution and severe agglomeration, making it difficult to obtain finely dispersed barium titanate powder after calcination. Third, traditional drying methods (such as hot air drying) suffer from uneven heat conduction, causing the surface of precursor particles to harden first while internal moisture slowly seeps out, leading to particle adhesion and agglomeration. Fourth, if the temperature is not properly controlled during calcination, abnormal grain growth or crystal distortion can easily occur, and traditional calcination is inefficient and energy-intensive.

[0005] To address the aforementioned issues, a barium titanate preparation process using specific dispersants and microwave technology was developed. This process constructs a synergistic polymerization control system throughout the entire process, enabling the efficient preparation of barium titanate powder with fine particle size, high dispersibility, and high purity. This has significant industrial value and application prospects. Summary of the Invention

[0006] This invention provides a high-purity barium titanate powder made from oxalate and its preparation method, addressing the problems of difficult-to-eliminate initial precursor agglomeration, poor dispersant compatibility, high agglomerate content in the product, and difficulty in balancing process efficiency and energy consumption in existing oxalate-based barium titanate powder preparation methods. This method employs a synergistic controlled agglomeration process involving titanium salt stabilization, dispersant-assisted homogeneous reaction, microwave drying, and microwave gradient calcination. By introducing a dispersant with a specific structure, particle agglomeration is suppressed at its source, ultimately yielding high-performance barium titanate powder with a purity ≥99.9%, an average particle size of 30-60 nm, a particle size distribution index (PDI) ≤0.12, and an agglomerate content ≤1.5%. Simultaneously, it significantly shortens the process cycle and reduces energy consumption.

[0007] In a first aspect, the present invention relates to a method for preparing high-purity barium titanate powder of oxalate, comprising the following steps: (1) preparation of titanium salt stabilizing solution: adding a titanium source to a composite stabilizer and stirring at 40-60°C for 30-60 min; the composite stabilizer is composed of citric acid, ethylene glycol and deionized water in a mass ratio of 1:(2-3):(5-8), and the mass ratio of titanium source to composite stabilizer is 1:(3-5); (2) preparation of barium salt solution: dissolving a barium source in deionized water and adding 5-10% by mass of disodium EDTA solution. (2) Stir the dispersant in deionized water at room temperature for 20-40 min; the mass ratio of the disodium EDTA to the barium source is 1:(10-15), and the concentration of the barium salt solution is 0.5-1.0 mol / L; (3) Dissolve the dispersant in deionized water and stir at 30-50℃ for 15-30 min until completely dissolved to obtain the dispersant modified solution; the dispersant is a polyethylene glycol-polyacrylic acid block copolymer with a number average molecular weight of 2000-5000, and the concentration of the dispersant modified solution is 0.05-0.15 mol / L; (4) Stir the titanium salt stabilizer and barium salt in water. The solution and dispersant modified solution were simultaneously pumped into the oxalic acid solution at a Ba to Ti molar ratio of 1:(1.02-1.05) and a dispersant to titanium source mass ratio of 1:(15-25). The reaction temperature was controlled at 60-80℃, the stirring speed at 500-800r / min, and the pH value was adjusted to 4.5-5.5. After reacting for 60-90 min, the solution was kept warm and aged for 2-4 h to obtain the barium oxalate precursor suspension; (5) Microwave drying and purification: The barium oxalate precursor suspension was centrifuged to separate the precipitate, and washed with deionized water and anhydrous ethanol. After washing, place it in a microwave drying device, first dry it with 200-300W power for 15-25min, then dry it with 400-500W power for 10-20min to obtain the purified barium oxalate precursor; (6) Microwave gradient calcination: put the purified precursor into a microwave calcination furnace, first raise it to 300-400℃ at 10-15℃ / min and keep it at 30-60min, then raise it to 700-800℃ at 5-8℃ / min and keep it at 60-120min, cool it with the furnace and then crush and sieve it to obtain high-purity barium titanate powder.

[0008] Preferably, the titanium source in step (1) is titanium tetrachloride or titanium oxysulfate.

[0009] Preferably, the barium source in step (1) is barium nitrate or barium chloride.

[0010] Preferably, the concentration of the oxalic acid solution in step (4) is 1.0-1.5 mol / L, and the molar ratio of titanium salt to oxalic acid is 1:(2.0-2.2).

[0011] Secondly, this invention relates to a high-purity barium titanate oxalate powder prepared by the above method, wherein the powder purity is ≥99.9%, the average particle size is 30-60 nm, the agglomerate content is ≤1.5%, and the dielectric constant at 1 kHz is ≥2000. The powder contains Sr, Ca, and Fe impurities ≤10 ppm, and the particle size distribution index (PDI) is ≤0.12.

[0012] The beneficial effects of this invention are as follows: the polyethylene glycol-polyacrylic acid block copolymer dispersant inhibits precursor particle agglomeration at the source, and combined with the subsequent polymerization control effects of microwave drying and gradient calcination, it completely solves the agglomeration problem in the preparation of barium titanate by the oxalate method. The polyethylene glycol-polyacrylic acid block copolymer dispersant requires a small dosage and is completely decomposed, leaving no impurities or residues, eliminating the need for additional purification steps and significantly reducing production costs.

[0013] By using microwave drying and microwave gradient calcination, the total drying and calcination time is reduced to 2-3.5 hours, and the production efficiency is increased by 2-3 times. At the same time, the introduction of dispersant reduces the number of subsequent washings by 1-2 times, further shortening the process cycle and making it suitable for industrial continuous production.

[0014] The prepared barium titanate powder has extremely high purity, with a total impurity content of ≤100ppm, including harmful impurities such as Sr, Ca, and Fe, each with a content of ≤10ppm. The average particle size is 30-60nm, the particle size distribution index (PDI) is ≤0.12, the agglomerate content is ≤1.5%, and the dispersion performance is excellent. It can be directly used for the preparation of high-end slurries. The dielectric constant (1kHz) is ≥2000, which is far superior to the products of traditional processes and microwave-optimized processes without the addition of specific dispersants. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 is a schematic diagram of the preparation process of high-purity barium titanate oxalate powder disclosed in an embodiment of the present invention. Detailed Implementation

[0017] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0018] The existing oxalate method still faces several bottlenecks in practical applications: First, during precursor preparation, titanium salts are prone to hydrolysis, generating impurities that reduce product purity and affect subsequent dielectric properties. Second, uneven ion diffusion in the reaction system easily leads to the formation of precursor particles with wide particle size distribution and severe agglomeration, making it difficult to obtain finely dispersed barium titanate powder after calcination. Third, traditional drying methods (such as hot air drying) suffer from uneven heat conduction, causing the surface of precursor particles to harden first while internal moisture slowly seeps out, leading to particle adhesion and agglomeration. Fourth, improper temperature control during calcination can easily result in abnormal grain growth or crystal distortion, and traditional calcination is inefficient and energy-intensive.

[0019] To address the aforementioned technical problems, as shown in Figure 1, this invention provides a method for preparing high-purity barium titanate oxalate powder, comprising the following steps: (1) Preparation of titanium salt stabilizing solution: adding a titanium source to a composite stabilizer and stirring at 40-60°C for 30-60 min; the composite stabilizer is composed of citric acid, ethylene glycol, and deionized water in a mass ratio of 1:(2-3):(5-8), and the mass ratio of titanium source to composite stabilizer is 1:(3-5); (2) Preparation of barium salt solution: dissolving a barium source in deionized water and adding a solution with a mass fraction of 5- 10% EDTA disodium solution, stirred at room temperature for 20-40 min; the mass ratio of EDTA disodium to barium source is 1:(10-15), and the concentration of barium salt solution is 0.5-1.0 mol / L; (3) Dissolve the dispersant in deionized water, and stir at 30-50℃ for 15-30 min until completely dissolved to obtain a dispersant modified solution; the dispersant is polyethylene glycol-polyacrylic acid block copolymer, with a number average molecular weight of 2000-5000, and the concentration of dispersant modified solution is 0.05-0.15 mol / L; (4) Titanium salt stabilizer, barium salt solution and dispersant modified solution were simultaneously pumped into oxalic acid solution at a Ba to Ti molar ratio of 1:(1.02-1.05) and a dispersant to titanium source mass ratio of 1:(15-25). The reaction temperature was controlled at 60-80℃, the stirring speed at 500-800r / min, and the pH value was adjusted to 4.5-5.5. After reacting for 60-90 min, the mixture was kept warm and aged for 2-4 h to obtain a barium oxalate precursor suspension; (5) Microwave drying and purification: The barium oxalate precursor suspension was centrifuged to separate the precipitate, and then purified by deionized water and water-free water. After washing with water and ethanol, place it in a microwave drying device, first dry it with 200-300W power for 15-25min, then dry it with 400-500W power for 10-20min to obtain the purified barium oxalate precursor; (6) Microwave gradient calcination: put the purified precursor into a microwave calcination furnace, first raise it to 300-400℃ at 10-15℃ / min and keep it at 30-60min, then raise it to 700-800℃ at 5-8℃ / min and keep it at 60-120min, cool it with the furnace and then crush and sieve it to obtain high-purity barium titanate powder.

[0020] In one embodiment, the titanium source in step (1) is titanium tetrachloride or titanium oxysulfate.

[0021] In one embodiment, the barium source in step (1) is barium nitrate or barium chloride.

[0022] In one embodiment, the concentration of the oxalic acid solution in step (4) is 1.0-1.5 mol / L, and the molar ratio of titanium salt to oxalic acid is 1:(2.0-2.2).

[0023] This composite stabilizer overcomes the limitations of traditional single stabilizers by employing a citric acid-ethylene glycol composite stabilizer. Citric acid reacts with Ti... 4+ Forming stable chelates effectively inhibits Ti 4+ Hydrolysis; ethylene glycol, as a stabilizer, not only enhances the reaction between citric acid and Ti. 4+ The coordination effect of the compound also helps to form a well-dispersed sol environment during the reaction, preventing particle aggregation. Compared with the single citric acid or ammonia stabilizers used in the prior art, the composite system of the present invention extends the stability time of titanium salt to more than 12 hours and reduces the hydrolysis rate to below 0.5%.

[0024] A polyethylene glycol-polyacrylic acid block copolymer (PEG-PAA) was introduced as a dedicated dispersant in the oxalate method for preparing barium titanate. The PEG segments of this block copolymer exhibit good hydrophilicity and steric hindrance, forming a three-dimensional barrier on the surface of the resulting precursor particles, hindering particle proximity and adhesion. The PAA segments can interact with metal ions (Ba) on the particle surface via their carboxyl groups. 2+ Ti 4+ The PAA chain forms a coordination effect, further enhancing the adsorption stability of the dispersant on the particle surface. Simultaneously, the dissociation characteristics of the PAA segments impart a negative charge to the particle surface, further inhibiting aggregation through electrostatic repulsion. Compared to traditional dispersants (such as polyethylene glycol and sodium dodecylbenzenesulfonate), PEG-PAA dispersant exhibits 4-6 times improved dispersion stability and can be completely decomposed and volatilized during subsequent microwave calcination, leaving no impurities.

[0025] Titanium salt stabilizing solution, barium salt solution, and dispersant-modified solution are simultaneously introduced into the reaction system to ensure that the dispersant can be adsorbed onto the particle surface at the initial stage of precursor particle formation, thus inhibiting particle agglomeration from the source. Meanwhile, disodium EDTA modifies the reaction of Ba... 2+ Chelation slows down Ba 2+ The release rate, combined with the composite stabilizer for Ti 4+ The stabilizing effect of Ti 4+ with Ba 2+ Achieving synchronous and uniform contact in oxalic acid solution, combined with the steric hindrance and electrostatic repulsion of the dispersant, completely solves the core problem of excessively high local concentrations, rapid particle growth, and agglomeration in traditional processes. Furthermore, precisely controlling the reaction pH to 4.5-5.5 ensures sufficient precipitation of barium titanium oxalate while preventing the formation of other impurity phases, and simultaneously guarantees optimal dissociation and adsorption of the dispersant. A dispersant-to-titanium source mass ratio of 1:(15-25) is the optimal ratio for achieving good dispersion; ratios above or below this range significantly reduce dispersion effectiveness and result in noticeable agglomeration.

[0026] Microwave drying technology is employed, where microwave heating achieves simultaneous heating of the precursor particles both inside and out, resulting in rapid and uniform evaporation of moisture. This avoids the agglomeration path of "surface hardening - internal moisture seepage - particle adhesion" common in traditional drying methods. Simultaneously, a segmented power mode is used: low power initially slowly removes surface adsorbed water, while high power rapidly removes internal crystalline water, further reducing hydrogen bonding and particle aggregation. Compared to traditional hot air drying, the drying time is significantly shortened.

[0027] The microwave gradient calcination process combines the rapid and uniform heating characteristics of microwaves with gradient temperature rise. In the low-temperature degreasing stage, the rapid heating by microwaves causes organic impurities (citric acid, EDTA, oxalate) and dispersants in the precursor to decompose and volatilize quickly, avoiding the carbonization residue caused by localized high temperatures in traditional calcination. In the high-temperature crystallization stage, the uniform heating field of the microwaves ensures synchronous nucleation and uniform growth of barium titanate grains, while simultaneously reducing the calcination temperature (50-100℃ lower than traditional processes) and shortening the holding time, effectively inhibiting abnormal grain growth. Furthermore, the energy consumption of microwave calcination is 40-50% lower than that of traditional muffle furnace calcination.

[0028] This invention discloses a high-purity barium titanate oxalate powder prepared by the above method. The powder has a purity ≥99.9%, an average particle size of 30-60 nm, an agglomerate content ≤1.5%, and a dielectric constant ≥2000 at 1 kHz. The powder contains Sr, Ca, and Fe impurities ≤10 ppm, and has a particle size distribution index (PDI) ≤0.12.

[0029] The following describes the embodiments of the present invention in detail. Embodiment 1: A method for preparing high-purity barium titanate oxalate powder, comprising the following steps: (1) Preparation of titanium salt stabilizing solution: 100g of titanium tetrachloride is added to a composite stabilizer composed of 30g of citric acid, 90g of ethylene glycol and 240g of deionized water, and stirred at 50°C for 45min to obtain titanium salt stabilizing solution; (2) Preparation of barium salt solution: 170g of barium nitrate is dissolved in deionized water, and 17g of 8% EDTA disodium solution is added. (2) Stir at room temperature for 30 min to prepare a barium salt solution with a concentration of 0.8 mol / L; (3) Dissolve 6 g of polyethylene glycol-polyacrylic acid block copolymer (number average molecular weight 3000) in 100 mL of deionized water and stir at 40 °C for 20 min until completely dissolved to obtain a dispersant modified solution with a concentration of 0.08 mol / L; (4) Mix the titanium salt stabilizer, barium salt solution and dispersant modified solution in a ratio of Ba to Ti molar ratio of 1:1.03 and the dispersant to titanium source mass ratio of 1:16.7. Meanwhile, it was pumped into a reaction vessel containing 300g of 1.2mol / L oxalic acid solution at a rate of 20mL / min, the reaction temperature was controlled at 70℃, the stirring speed was 600r / min, and ammonia water was added dropwise to adjust the pH value to 5.0. After reacting for 75min, it was kept warm and aged for 3h to obtain a suspension of barium oxalate precursor; (5) Microwave drying and purification: the suspension of barium oxalate precursor was centrifuged at 5000r / min, the precipitate was collected, washed 3 times with deionized water, and anhydrous ethyl acetate was removed. Wash once with alcohol; place the precipitate in a microwave drying oven and dry at 250W power for 20min, then dry at 450W power for 15min, with the drying temperature controlled at 90℃, to obtain the purified barium oxalate precursor; (6) Microwave gradient calcination: place the purified precursor in a microwave calcination furnace, raise it to 350℃ at a rate of 12℃ / min, keep it at 45min, then raise it to 750℃ at a rate of 6℃ / min, keep it at 90min, cool it with the furnace, then crush and sieve to obtain high-purity barium titanate powder.

[0030] The barium titanate powder prepared in Example 1 was tested and found to have a purity of 99.96%, an average particle size of 48 nm, a PDI of 0.11, an agglomerate content of 1.0%, and a dielectric constant (1 kHz) of 2050.

[0031] Example 2: A method for preparing high-purity barium titanate oxalate powder, comprising the following steps: (1) Preparation of titanium salt stabilizer: 120g of titanium oxysulfate is added to a composite stabilizer composed of 40g of citric acid, 80g of ethylene glycol and 320g of deionized water, and stirred at 45°C for 60min to obtain titanium salt stabilizer; (2) Preparation of barium salt solution: 150g of barium chloride is dissolved in deionized water, and 12g of 10% EDTA disodium solution is added, and stirred at room temperature for 25 minutes. min, prepare a barium salt solution with a concentration of 0.6 mol / L; (3) dissolve 6 g of polyethylene glycol-polyacrylic acid block copolymer (number average molecular weight 4000) in 100 mL of deionized water, stir at 35 °C for 25 min until completely dissolved, and obtain a dispersant modified solution with a concentration of 0.06 mol / L; (4) mix the titanium salt stabilized solution, barium salt solution and dispersant modified solution at a ratio of Ba to Ti molar ratio of 1:1.02 and a dispersant to titanium source mass ratio of 1:20, and simultaneously Pumped at a rate of 15 mL / min into a reaction vessel containing 280 g of 1.0 mol / L oxalic acid solution, the reaction temperature was controlled at 65 °C and the stirring speed at 550 r / min. Ammonia was added dropwise to adjust the pH value to 4.8. After reacting for 90 min, the mixture was kept warm and aged for 2.5 h to obtain a suspension of barium oxalate precursor; (5) Microwave drying and purification: The suspension was centrifuged at 4500 r / min, the precipitate was collected, and washed 4 times with deionized water and 2 times with anhydrous ethanol. ; The precipitate was placed in a microwave drying oven and dried at 200W power for 25 minutes, and then dried at 400W power for 20 minutes. The drying temperature was controlled at 85℃ to obtain the purified barium oxalate precursor; (6) Microwave gradient calcination: The precursor was placed in a microwave calcination furnace and heated to 300℃ at a rate of 10℃ / min, held for 60 minutes, and then heated to 700℃ at a rate of 5℃ / min, held for 120 minutes. After cooling in the furnace, it was crushed and sieved to obtain high-purity barium titanate powder.

[0032] The barium titanate powder prepared in Example 2 was tested and found to have a purity of 99.94%, an average particle size of 42 nm, a PDI of 0.10, an agglomerate content of 0.9%, and a dielectric constant (1 kHz) of 2020.

[0033] Comparative Example 1: Except for the absence of ethylene glycol and dispersant in the composite stabilizer, the other process parameters were the same as in Example 1. The obtained barium titanate powder was tested and found to have a purity of 99.5%, an average particle size of 190 nm, an agglomerate content of 16%, and a dielectric constant of only 850.

[0034] Comparative Example 2: Preparation of Titanium Salt Stabilizing Solution: 100g of titanium tetrachloride was added to a composite stabilizer composed of 30g citric acid, 30g ethylene glycol, and 200g deionized water. The mixture was stirred at 50°C for 45 minutes to obtain a titanium salt stabilizing solution. The remaining process parameters were the same as in Example 1. The obtained barium titanate powder had a purity of 99.2%, an average particle size of 90nm, an agglomerate content of 7%, and a dielectric constant of only 1550.

[0035] Comparative Example 3: Except for conventional hot air drying (90℃, 5h) and one-time calcination in a muffle furnace (750℃, 1.5h), the other process parameters were the same as in Example 1. The obtained barium titanate powder had an average particle size of 75nm, an agglomerate content of 4.2%, and a dielectric constant of 1591, but its dispersion and dielectric properties were significantly inferior to those of Example 1.

[0036] Comparative Example 4: Except for replacing the dispersant with an equal amount of polyethylene glycol (number average molecular weight 3000), the other process parameters were the same as in Example 1. The obtained barium titanate powder had an average particle size of 68 nm, an agglomerate content of 3.5%, and a dielectric constant of 1653. Because traditional dispersants can only provide a single steric hindrance effect, their dispersion effect is far inferior to that of the specific block copolymer of this invention.

[0037] Comparative Example 5: Except for changing the mass ratio of dispersant to titanium source to 1:30, the other process parameters were the same as in Example 1. The obtained barium titanate powder had an average particle size of 65 nm, an agglomerate content of 3.1%, and a dielectric constant of 1730. Comparative Example 5 increased the proportion of dispersant, but failed to achieve the expected dispersion effect, resulting in an increased agglomerate content.

[0038] Comparative Example 6: Except for changing the mass ratio of dispersant to titanium source to 1:10, the other process parameters were the same as in Example 1. The obtained barium titanate powder had an average particle size of 67 nm, an agglomerate content of 3.8%, and a dielectric constant of 1787. Comparative Example 6 reduced the proportion of dispersant added, but still failed to achieve the expected dispersion effect, and the agglomerate content increased.

[0039] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A method for preparing high-purity barium titanate oxalate powder, characterized in that, Includes the following steps: ( 1) Preparation of titanium salt stabilized solution: Add titanium source to composite stabilizer and stir at 40-60℃ for 30-60min; the composite stabilizer is composed of citric acid, ethylene glycol and deionized water in a mass ratio of 1:(2-3):(5-8), and the mass ratio of titanium source to composite stabilizer is 1:(3-5); the titanium source is titanium tetrachloride or titanium oxysulfate; (2) Preparation of barium salt solution: Dissolve barium source in deionized water, add 5-10% EDTA disodium solution, and stir at room temperature for 20-40min; the mass ratio of EDTA disodium to barium source is 1:(10-15), and the concentration of barium salt solution is 0.5-1.0mol / L; the barium source is barium nitrate or barium chloride; (3) Dissolve dispersant in deionized water and stir at 30-50℃ for 15-30min until completely dissolved to obtain dispersant modified solution; the dispersant is polyethylene glycol-polyacrylic acid block copolymer, which is evenly distributed The molecular weight is 2000-5000, and the concentration of the dispersant modified solution is 0.05-0.15 mol / L; (4) The titanium salt stabilizer, barium salt solution and dispersant modified solution are simultaneously pumped into the oxalic acid solution at a ratio of Ba to Ti molar ratio of 1:(1.02-1.05) and a dispersant to titanium source mass ratio of 1:(16.7-25). The reaction temperature is controlled at 60-80℃, the stirring speed is 500-800 r / min, and the pH value is adjusted to 4.

5. -5.5, react for 60-90 min and then keep warm and age for 2-4 h to obtain barium oxalate precursor suspension; (5) Microwave drying and purification: centrifuge the barium oxalate precursor suspension to separate the precipitate, wash it with deionized water and anhydrous ethanol, and place it in a microwave drying device. First dry it with 200-300W power for 15-25 min, and then dry it with 400-500W power for 10-20 min to obtain purified barium oxalate precursor; (6) Microwave gradient calcination: The purified precursor is placed in a microwave calcination furnace, first heated to 300-400℃ at 10-15℃ / min and held for 30-60min, then heated to 700-800℃ at 5-8℃ / min and held for 60-120min. After cooling in the furnace, it is crushed and sieved to obtain high-purity barium titanate powder.

2. The method for preparing high-purity barium titanate oxalate powder according to claim 1, characterized in that, The concentration of the oxalic acid solution in step (4) is 1.0-1.5 mol / L, and the molar ratio of titanium salt to oxalic acid is 1:(2.0-2.2).

Images