用粉体颗粒表面改性技术制备高致密高硬度BaTiO_3基陶瓷的研究

Study of BaTiO_3-based Ceramics with High Density and High Hardness Prepared by Particle Surface Treatment Technique

选取用草酞酸钡共沉淀法生产的BaTiO_3粉料为基体原料,加入5(wt)％MgO进行粉体颗粒表面改性。对粉体的表征及X-射线结构分析结果表明,Mg与基体表面充分反应,生成MgTiO_3新相,无游离MgO存在,一次颗粒形貌为球状,粒度均在100～300nm范围内,但颗粒团聚情况仍存在。用获得的粉料进行成瓷试验,制得细晶(1.00～300nm),高致密,而显微硬度与耐电场击穿强度都较一般的BaTiO_3基陶瓷高的试样。结果表明,加镁改性有阻止晶粒生长、提高致密度、扩大烧成温度范围和提高硬度的作用。

BaTiO_3 powder prepared by coprecipitation of barium oxalic titanate was chosen as matrix material and a magnesic organic salt solution containing 5wt% MgO was added for coating MgO on particle surface of the powder. Magnesic organic salt solution was synthesized by MgCO_3.The solution was completely dispersed in BaTiO_3 matrix in proportion by ball milling or high-speed stirring or ultrasonic dispersing. As a result, magnesic organic salt solution was uniformly coated on particle surface of the powder. The coated powder was sprayed and completely dried in vacuum oven at low temperature,then the white and loose precursor was obtained. After calcining at 800℃, BaTiO_3 superfire powder coated by MgO was obtained. Its average particle size is of 0.48μm(D_(50)) and 0.17μm (D_(?)), respectively. By characterizing the matrix, MgTiO_3 phase is formed and MgO nonexisted. The morphology of particles is spheroidal. The particle size is within 1000～3000A, but, a part of particles of the prepared powder is agglomerated. The ceramic material sintered by this kind of powder possesses finer grain (0.1 ～0.3μm), higher density and hardness as well as breaking voltage in compared with those prepared by conventional methods. It has also indicated that it is beneficial to prevent grain growth, enhance density and hardness of the sintered material and enlarge its sintering temperature range.