CN1417162A - Wet process of preparing high-purity barium titanate superfine powder as electronic functional material - Google Patents

Abstract

The present invention relates to an electronic ceramic material titanate and aims at providing the wet process of preparing superfine high-purity barium titanate powder as electronic functional material. The said process includes raw material purification; preparing water solution of barium salt, water solution of titanium salt and oxalic acid solution; mixing, coprecipitation, separation, washing, eliminating impurity, drying and heat treatment to obtain barium titanate powder. The product has purity over 99.95 wt%, Ba/Ti ratio of 1.000 with error within 0.002, granularity controlled in 0.1-0.7 micron and tetragonal crystal structure.

Description

Wet process for preparing high-purity barium titanate superfine powder as electronic functional material

The invention relates to electronic ceramic material titanate, in particular to wet preparation of high-purity barium titanate ultrafine powder.

In the background art, the development of titanate began in the 40 th century, and the barium titanate powder was successfully prepared in western countries by a solid phase method, and in the late sixties, some countries began to research and prepare barium titanate powder by a liquid phase method, and high-purity and fine titanate powder was taken as a key research. Some enterprises in China adopt a solid phase method for small-scale preparation, and some enterprises still get by imports. The existing production method of barium titanate powder mainly comprises the following steps: high temperature solid phase sintering method, salt melting cultivation method, liquid phase method, gas phase method, etc., wherein the traditional high temperature solid phase method is BaCO₃、TiO₂Mixing and grinding the raw materials according to a metering ratio, and sintering at 1000-1350 ℃ to obtain BaTiO₃The sintering process needs to be repeated grinding, and the method has the advantages of simple process, low cost and the like, but has the defects of difficult uniform mixing of the components, difficult control of Ti/Ba ratio, high energy consumption, large product particles, pure product and the likeLow degree, low yield and the like. In the traditional liquid phase method, soluble titanium salt and soluble barium salt react in aqueous solution to form a barium titanate precursor, and then the barium titanate precursor is subjected to low-temperature heat treatment to prepare barium titanate powder. Because titanium and barium are mixed and reacted in the solution, the mixture is uniform, the granularity can be controlled in the initial stage of the reaction, and the superfine barium titanate powder can be prepared by low-temperature heat treatment. The methods all prepare cubic phase crystal structures, and the purity is low.

The invention aims to develop a wet preparation method of high-purity barium titanate ultrafine powder serving as an electronic functional material, which is characterized in that according to the requirements on the application and indexes of products and in consideration of the source and production cost of raw materials, a chemical coprecipitation method of oxalate is used as a basis, and auxiliary materials are added to improve the preparation process so as to reduce impurities to the minimum level, thereby preparing barium titanate BaTiO with a tetragonal crystal structure, purity of more than 99.95 percent, titanium-barium ratio of 1 +/-0.002 and granularity of 0.1-0.7 mu m, which can be controlled according to the requirements of users₃And (3) powder.

The technical scheme for realizing the aim is as follows:

the process method comprises the following steps:

1. impurity removal and purification preparation of raw materials: namely, the barium salt aqueous solution and the oxalic acid H are prepared by purification₂C₂O₄Solution: at normal pressure, pure barium chloride BaCl is added₂And oxalic acid H₂C₂O₄Respectively mixing the raw materials in a proportioning tank with high-purity water with the water quality of less than 0.2 mu s/cm to prepare a saturated solution at the temperature of 95-100 ℃, filtering, cooling, crystallizing,Separating, and preparing the crystal into purified barium salt water solution and refined purified oxalic acid solution with the concentrations of 0.2-0.3M and 1-2M respectively by using high-purity water;

2. impurity removal and purification preparation of raw materials: namely purifying and preparing the titanium salt aqueous solution: titanium tetrachloride TiCl is added into a batching tank under normal pressure₄Adding dichlorobenziodic acid at 70-90 ℃ for treatment, adding copper wire or copper powder for treatment, distilling in a condenser with a rectifying device, and collecting 136 +/-5 ℃ fractions to obtain high-purity TiCl₄(ii) a Subjecting the high-purity TiCl to reaction₄High speed stirringSimultaneously adding a nonionic surfactant and high-purity water with the water quality of less than 0.2 mu s/cm to prepare a purified titanium salt water solution with the concentration of 0.4-0.5M;

3. mixing-coprecipitation reaction: under normal pressure, mixing the refined high-purity barium salt aqueous solution and titanium salt aqueous solution uniformly in a stirrer and a reaction kettle, adding the refined oxalic acid solution for coprecipitation reaction, wherein the weight ratio of the refined high-purity barium salt aqueous solution to the refined oxalic acid solution is TiCl₄∶BaCl₂∶H₂C₂O₄1: 1.02-1.3: 2.1, the ratio of the titanium and barium ions is Ti⁴⁺∶Ba²⁺The reaction temperature is 70-80 ℃, the pressure is normal pressure for 100-150 minutes, and finally the precipitate BaTiO (C) is formed₂O₄)₂·4H₂O；

4. Separation, washing and impurity removal: at normal pressure, the precipitate of the mixing-coprecipitation reaction is filtered or centrifuged to separate, and washed with high-purity water in flowing water until no Cl is formed^-Ion detection, or repeatedly soaking the separated precipitate with small amount of high purity water, separating, soaking and separating until reaching Cl^-Detecting ions, and discharging the used wastewater after treatment;

5. drying and heat treatment: under normal pressure, firstly separated and washed BaTiO (C)₂O₄)₂Drying the precipitate in a drying oven at 100-130 ℃, removing water, performing sintering heat treatment, and performing thermal decomposition at 700-1000 ℃ for 100-150 minutes to obtain the purified superfine tetragonal phase BaTiO₃The powder has the weight ratio of Ba to Ti of 1 +/-0.002, the purity of 99.95 percent, the granularity of 0.1-0.7 mu m according to the requirement of a user, the yield of more than 96 percent, and the finished product is packaged after inspection.

The invention has the following advantages and effects:

(1) because the oxalate chemical coprecipitation method is used as the basis and the improved preparation process of adding auxiliary materials is adopted, the BaTiO product is realized₃In which the Ba/Ti ratio is 1 + -0.002, BaTiO₃The purity reaches 99.95 percent, the granularity is between 0.1 and 0.7 mu m and can be controlled according to the requirements of users, the phase is tetragonal phase and full ofHigh-tech requirements on high purity and superfine barium titanate are met.

(2) The barium titanate powder produced by the process has the characteristics of simple process, low cost and high quality, completely meets the requirements of the production of the conventional electronic ceramic components, and provides high-quality and stable barium titanate powder for electronic ceramic manufacturers.

The attached drawing of the invention is a process flow chart.

The following examples are given: referring to the process flow diagram of the invention, the impurity removal and purification preparation of the raw materials in the first step: preparing barium salt aqueous solution, refined oxalic acid solution and titanium salt aqueous solution; wherein the first two are prepared by reacting BaCl₂、H₂C₂O₄Respectively preparing saturated solutions with high purity water at 95-100 deg.C, filtering the hot saturated solution to obtain high purity water with concentration of 0.2 μ s/cm or less, cooling, crystallizing, separating, recycling mother liquor, respectively preparing high purity water with concentration of 0.2, 0.25 or 0.3M, optionally selecting concentration of 0.2-0.3M, and BaCl with concentration of 1, 1.5 or 2M, optionally selecting concentration of 1-2M₂And H₂C₂O₄An aqueous solution. For the preparation of the purified aqueous titanium salt solution: in a batching tank, titanium tetrachloride TiCl₄Heating to 70, 75, 80, 85 or 90 ℃, selectively adding dichlorobenziodic acid into the mixture at the temperature of 70-90 ℃, then adding copper wires or copper powder for treatment, distilling the mixture in a condenser with a rectifying device, and collecting 136 +/-5 ℃ fractions to obtain high-purity TiCl₄Then stirring at high speed in a stirrer to increase the heat and mass transfer rate, and optionally adding nonionic surfactant at normal temperature and pressure to form TiOCl₂Directionally producing purified TiCl₄An aqueous solution.

The second step is that: mixing and coprecipitation reaction: mixing the refined and purified barium salt solution and titanium salt solution, stirring, adding refined and purified oxalic acid solution, mixing and coprecipitatingAnd (3) performing precipitation reaction, wherein the weight ratio of each component is as follows: TiCl (titanium dioxide)₄∶BaCl₂∶H₂C₂O₄1: 1.02-1.03: 2.1, wherein the ion content: ti⁴⁺∶Ba²⁺1: 1.02-1.03, selecting reaction parameters of normal pressure, 70, 75 ℃ or 80 ℃, optionally selecting the reaction parameters between 70 ℃ and 80 ℃, the reaction parameters within 100 minutes to 150 minutes, and optionally selecting the reaction parameters within 100 minutes to 150 minutes to finally obtain a purified precipitate BaTiO (C)₂O₄)₂·4H₂O。

The third step: separation, washing and impurity removal: the precipitation separation is carried out by adopting a suction filtration or centrifugation mode, and is washed by high-purity water in a running water mode until no Cl is generated^-Ion detection, or repeated soaking, separating, soaking and separating with small amount of high purity water to remove impurities. The residual waste water of the working procedure is discharged after being treated.

The fourth step: drying and heat treatment: separating, washing and removing impurity BaTiO (C)₂O₄)₂Precipitating at 100,110. Drying at 120 deg.C or 130 deg.C (optionally selected within 100-130 deg.C), removing water, heat treating, and sintering to obtain BaTiO (C)₂O₄)₂Decompose to form BaTiO₃The technological parameters are as follows: the temperature is 700, 750, 800, 850, 900, 950 ℃ or 1000 ℃ (can be randomly selected in the range of 700-1000 ℃), the thermal decomposition time is 100, 110, 120, 130, 140 minutes or 150 minutes (can be randomly selected in the range of 100-150 minutes), and finally the purified superfine tetragonal phase BaTiO with the weight ratio of Ba/Ti being 1 +/-0.002, the purity of 99.95 percent, the granularity of 0.1-0.7 mu m, the granularity of which can be controlled according to the process parameters required by a user and the yield of more than 96 percent is obtained₃And (5) inspecting the powder, and packaging and warehousing for sale.

The main reactions are as follows:

Claims (1)

1. the wet process of preparing high purity barium titanate superfine powder as electronic functional material features that:

① impurity removal and purification preparation of raw materials, namely, purification preparation of barium salt water solution and oxalic acid H₂C₂O₄Solution: at normal pressure, pure barium chloride BaCl is added₂And oxalic acid H₂C₂O₄Respectively mixing high-purity water with the water quality of less than 0.2 mu s/cm in a proportioning tank to prepare a saturated solution with the temperature of 95-100 ℃, filtering, cooling, crystallizing, separating, and respectively preparing the crystals into a purified barium salt aqueous solution and a purified oxalic acid solution with the concentrations of 0.2-0.3M and 1-2M by using the high-purity water;

② impurity removal and purification preparation of raw material, namely purifying and preparing titanium salt water solution, namely preparing titanium tetrachloride TiCl in a batching tank under normal pressure₄Adding dichlorobenziodic acid at 70-90 ℃ for treatment, adding copper wire or copper powder for treatment, distilling in a condenser with a rectifying device, and collecting 136 +/-5 ℃ fractions to obtain high-purity TiCl₄(ii) a Subjecting the high-purity TiCl to reaction₄Stirring at high speed, adding nonionic surfactant, adding high-purity water with water quality of below 0.2 μ s/cm, and making into 0.4-0.5M purified titanium salt water solution;

③ mixing and coprecipitation reaction, wherein the refined high-purity barium salt solution and titanium salt solution are mixed uniformly in a stirrer and a reaction kettle under normal pressure, and refined oxalic acid solution is added for coprecipitation reaction, wherein the weight ratio of the refined high-purity barium salt solution to the titaniumsalt solution is TiCl₄∶BaCl₂∶H₂C₂O₄1: 1.02-1.3: 2.1, the ratio of the titanium and barium ions is Ti⁴⁺∶Ba²⁺The reaction temperature is 70-80 ℃, the pressure is normal pressure for 100-150 minutes, and finally the precipitate BaTiO (C) is formed₂O₄)₂·4H₂O；

④ separating, washing, removing impurities, mixing under normal pressure, coprecipitating and reactingThe precipitate is separated by suction filtration or centrifugation, washed with high-purity water in flowing water until no Cl is formed^-Ion detection, or repeatedly soaking the separated precipitate with small amount of high purity water, separating, soaking and separating until reaching Cl^-Detecting ions, and discharging the used wastewater after treatment;

⑤ drying and heat treating, wherein the separated and washed BaTiO (C) is firstly treated under normal pressure₂O₄)₂Drying the precipitate in a drying oven at 100-130 ℃, removing water, performing sintering heat treatment, and performing thermal decomposition at 700-1000 ℃ for 100-150 minutes to obtain the purified superfine tetragonal phase BaTiO₃The powder has the weight ratio of Ba to Ti of 1 +/-0.002, the purity of 99.95 percent, the granularity of 0.1-0.7 mu m according to the requirement of a user, the yield of more than 96 percent, and the finished product is packaged after inspection.