Preparation method of nano-barium titanate for electronic ceramics

Abstract

The application discloses a preparation method of nano barium titanate for electronic ceramics, and comprises the following steps: adding a dispersing agent into an oxalic acid solution, starting a stirring device and heating; adding barium chloride solution and titanium tetrachloride solution into the oxalic acid solution in parallel flow at a uniform speed, and controlling the pH value of the reaction system to be 2.0-4.0; filtering and washing the mixture after reaction, drying and roasting the filter cake, and obtaining nano barium titanate. By introducing the dispersing agent into the reaction system, adding the reactants in parallel flow at a uniform speed, and making the reaction proceed under high-speed stirring, the application reduces the particle agglomeration in the reaction and roasting processes, and can prepare tetragonal phase nano barium titanate with small particles and high dispersion.

Description

Technical Field

[0001] This invention belongs to the field of nano-inorganic material preparation technology, specifically relating to a method for preparing nano-barium titanate for electronic ceramics. Background Technology

[0002] Barium titanate, due to its excellent piezoelectric, ferroelectric, voltage-resistant, and insulating properties, is widely used in functional ceramics, positive temperature coefficient thermistors, multilayer ceramic capacitors, and biomedicine. Ideal ceramic powder raw materials require high purity, fine particles, and a dispersed state. Conventional methods for preparing barium titanate include solid-state synthesis, hydrothermal synthesis, co-precipitation, and sol-gel methods. Solid-state synthesis uses titanium dioxide and barium carbonate as raw materials, which are mixed and calcined at 1400-1500℃. The resulting barium titanate has an uneven chemical composition, large particles, and is prone to impurities. Hydrothermal synthesis uses metatitanic acid and barium hydroxide as raw materials, controlling the pH to be alkaline, and reacting in a high-pressure hydrothermal environment to produce barium titanate. The prepared nano-barium titanate has many crystal defects, low ceramic density, easy retention of micropores, poor dielectric properties, and excessive dielectric loss. Both the coprecipitation method and the sol-gel method involve first preparing a precursor, such as hydroxide or oxalate, and then calcining it at high temperature to generate barium titanate. The reaction conditions are difficult to control, and the nanoparticles are prone to agglomeration and sintering.

[0003] In summary, barium titanate products prepared by conventional methods all suffer from severe particle agglomeration and are difficult to disperse, which greatly weakens the dielectric properties of barium titanate. Summary of the Invention

[0004] To address the shortcomings of the prior art, the present invention aims to provide a method for preparing nano-barium titanate for electronic ceramics, which can prepare small-particle, highly dispersed tetragonal phase nano-barium titanate.

[0005] To achieve the above-mentioned objective, this invention provides a method for preparing nano-barium titanate for electronic ceramics, the method comprising the following steps:

[0006] ① Add the dispersant to the oxalic acid solution, start the stirring device and heating;

[0007] ② Add 0.2-1.0 mol / L barium chloride solution and 0.2-1.0 mol / L titanium tetrachloride solution in parallel stream to the oxalic acid solution, and control the pH of the reaction system to be 2.0-4.0;

[0008] ③ The mixture after the above reaction was filtered, washed, and the filter cake was dried and calcined to obtain nano barium titanate.

[0009] In the above technical solution, the dispersant in step ① is at least one of sodium polycarboxylate, ammonium polyacrylate, P123, F127, JFCS, fatty alcohol polyoxyethylene ether, sucrose fatty acid ester, sodium stearoyl lactylate, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide. The amount of dispersant added is 3.0%-10% of the mass of titanium tetrachloride contained in the titanium tetrachloride solution in step ②. The dispersant is used to reduce particle agglomeration during the reaction and calcination process.

[0010] Furthermore, when the molar concentration of the titanium tetrachloride solution in step ② is 0.2-0.6 mol / L, a single type of dispersant is selected; when the molar concentration of the titanium tetrachloride solution in step ② is greater than 0.6 mol / L, in addition to selecting any one of P123, F127 and fatty alcohol polyoxyethylene ether, at least one of sodium polycarboxylate, ammonium polyacrylate, JFCS, sucrose fatty acid ester, sodium stearoyl lactylate, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide is used in combination.

[0011] Furthermore, the molar concentration ratio of the oxalic acid solution in step ① to the titanium tetrachloride solution in step ② is (3-10):1, and the volume ratio of the oxalic acid solution in step ① to the titanium tetrachloride solution in step ② is (1-3):1.

[0012] Furthermore, the stirring device mentioned in step ① is a high-speed disperser with a controlled rotation speed of 1000-2000 r / min.

[0013] Furthermore, in step ①, the oxalic acid solution needs to be heated to 40-70℃.

[0014] Furthermore, in step ②, the time for adding barium chloride solution and titanium tetrachloride solution in parallel flow is 30-90 min, and the Ba / Ti molar ratio of barium chloride solution to titanium tetrachloride solution in step ② is (1.0-1.1):1.

[0015] Furthermore, the amount of washing water used in step ③ is 30-50 times the mass of titanium tetrachloride contained in the titanium tetrachloride solution in step ②.

[0016] Furthermore, in step ③, the drying process is carried out at 70-110℃ for 12-24 hours; the roasting process is carried out at 700-1000℃ with oxygen enrichment for 1-4 hours, with a heating rate of 5-10℃ / min. Before roasting, the dried material needs to be ground for 30-60 minutes.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] This invention reduces particle agglomeration during the reaction and calcination processes by introducing a dispersant into the reaction system, adding reactants at a uniform rate in a co-current manner, and carrying out the reaction under high-speed stirring. This results in the preparation of tetragonal phase barium titanate nanoparticles with small size and high dispersion. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments, but this does not limit the invention in any way. To avoid redundancy, unless otherwise specified, the raw materials used in the following embodiments are all commercially available products, and the methods used are all conventional methods unless otherwise specified.

[0020] Example 1

[0021] The preparation method of nano-barium titanate for electronic ceramics includes the following specific steps:

[0022] 200 mL of 0.6 mol / L oxalic acid solution was added to a 1 L beaker. The stirring device was started and the speed was set to 1000 r / min. Then, 0.23 g of P123 dispersant was added, and the solution temperature was heated and maintained at 40 °C. After 30 min, 200 mL of 0.2 mol / L barium chloride solution and 200 mL of 0.2 mol / L titanium tetrachloride solution were added to the oxalic acid solution in a parallel stream, and the pH of the reaction system was controlled to be 2.0-4.0. The mixture after reaction was filtered and washed with 250 mL of deionized water. The filter cake was dried at 70 °C for 24 h and ground for 30 min. The ground material was then calcined at 700 °C with oxygen enrichment for 4 h at a heating rate of 10 °C / min to obtain nano-barium titanate. The nano-barium titanate prepared in Example 1 was subjected to XRD, SEM and chemical analysis, and the results are shown in Table 1.

[0023] Example 2

[0024] The preparation method of nano-barium titanate for electronic ceramics includes the following specific steps:

[0025] 200 mL of oxalic acid solution with a molar concentration of 2.0 mol / L was added to a 1 L beaker. The stirring device was started and the speed was set to 1500 r / min. Then, 1.2 g of F127 dispersant was added, and the solution temperature was heated and maintained at 50 °C. After 60 min, 204 mL of barium chloride solution with a molar concentration of 0.5 mol / L and 200 mL of titanium tetrachloride solution with a molar concentration of 0.5 mol / L were added to the oxalic acid solution in a parallel stream, and the pH of the reaction system was controlled to be 2.0-4.0. The mixture after reaction was filtered and washed with 800 mL of deionized water. The filter cake was dried at 90 °C for 16 h and ground for 40 min. The ground material was then calcined at 800 °C with oxygen enrichment for 3 h at a heating rate of 7 °C / min to obtain nano-barium titanate. The nano-barium titanate prepared in Example 2 was subjected to XRD, SEM and chemical analysis, and the results are shown in Table 1.

[0026] Example 3

[0027] The preparation method of nano-barium titanate for electronic ceramics includes the following specific steps:

[0028] 200 mL of oxalic acid solution with a molar concentration of 6.0 mol / L was added to a 1 L beaker. The stirring device was started and the speed was set to 2000 r / min. Then, 1.5 g of ammonium polyacrylate and 2.0 g of fatty alcohol polyoxyethylene ether dispersant were added. The solution temperature was heated and maintained at 70 °C. After 90 min, 220 mL of barium chloride solution with a molar concentration of 1.0 mol / L and 200 mL of titanium tetrachloride solution with a molar concentration of 1.0 mol / L were added to the oxalic acid solution in a parallel stream, and the pH of the reaction system was controlled to be 2.0-4.0. The mixture after reaction was filtered and washed with 1500 mL of deionized water. The filter cake was dried at 110 °C for 12 h and ground for 60 min. The ground material was then calcined at 900 °C with oxygen enrichment for 2 h at a heating rate of 5 °C / min to obtain nano-barium titanate. The nano-barium titanate prepared in Example 3 above was subjected to XRD, SEM and chemical analysis. The results are shown in Table 1.

[0029] Table 1. XRD, SEM, and chemical analysis results of the nano-barium titanate prepared in the examples.

[0030]

[0031] As shown in Table 1, the nano-barium titanate prepared by the preparation method of electronic ceramics provided by the present invention has a tetragonal crystal phase, c / a>1.0095, a particle size between 95-105 nm, and a Ba / Ti molar ratio between 0.995-1.005, which meets the requirements of GB / T 36595-2018.

[0032] Therefore, by introducing a dispersant into the reaction system, adding the reactants at a uniform rate in a co-current manner, and carrying out the reaction under high-speed stirring, the present invention reduces particle agglomeration during the reaction and calcination process, and can prepare tetragonal phase barium titanate nanoparticles with small particles and high dispersion.

[0033] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A method for preparing nano-barium titanate for electronic ceramics, characterized in that, The method includes the following steps: ① Add the dispersant to the oxalic acid solution, start the stirring device and heating; The dispersant is at least one of sodium polycarboxylate, ammonium polyacrylate, P123, F127, fatty alcohol polyoxyethylene ether, sucrose fatty acid ester, sodium stearoyl lactylate, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide; the amount of dispersant added is 3.0%-10% of the mass of titanium tetrachloride contained in the titanium tetrachloride solution in step ②. The stirring device is a high-speed disperser, with a controlled rotation speed of 1000-2000 r / min; the oxalic acid solution is heated to 40℃-70℃; ② Add 0.2-1.0 mol / L barium chloride solution and 0.2-1.0 mol / L titanium tetrachloride solution in parallel stream to the oxalic acid solution, and control the pH of the reaction system to be 2.0-4.0; When the molar concentration of the titanium tetrachloride solution in step ② is 0.2-0.6 mol / L, a single type of dispersant is selected; when the molar concentration of the titanium tetrachloride solution in step ② is greater than 0.6 mol / L, in addition to selecting any one of P123, F127 and fatty alcohol polyoxyethylene ether, at least one of sodium polycarboxylate, ammonium polyacrylate, sucrose fatty acid ester, sodium stearoyl lactylate, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide is used in combination. The molar ratio of the oxalic acid solution to the titanium tetrachloride solution is (3-10):1, and the volume ratio of the oxalic acid solution to the titanium tetrachloride solution is (1-3):

1. The barium chloride solution and titanium tetrachloride solution are added to the oxalic acid solution in a co-current manner for 30-90 minutes, and the Ba / Ti molar ratio of the barium chloride solution to the titanium tetrachloride solution is (1.0-1.1):

1. ③ The mixture after the above reaction was filtered, washed, and the filter cake was dried and calcined to obtain nano barium titanate; The washing process uses 30-50 times the mass of titanium tetrachloride in the titanium tetrachloride solution; the drying process is 70℃-110℃ for 12-24 hours; the calcination process is 700℃-1000℃ oxygen-enriched calcination for 1-4 hours, with a heating rate of 5-10℃ / min. Before calcination, the dried material is ground for 30-60 minutes. The obtained nano-barium titanate has a tetragonal crystal phase, c / a>1.0095, a particle size between 95-105 nm, and a Ba / Ti molar ratio of 0.995-1.005.

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