高压烧结的BaTiO3陶瓷的介电性能

用两种高压法烧结得到致密的细晶BaTiO3陶瓷。由压力辅助烧结得到的陶瓷晶粒没有过分长大,晶粒尺寸保持在纳米尺度内;用高压成型常压烧结法得到的陶瓷晶粒明显长大。当BaTiO3陶瓷的晶粒尺寸从400 nm减小到50 nm时,相应的介电常数从3 000减小到1 900。介电常数的减小可由晶粒尺寸的减小而导致四方度的降低和非铁电低介电常数的晶界层解释。且铁电-顺电转变由一个尖锐峰变成一个宽的区域,宽的转变区域表现出扩散相变的特征。

Dielectric Properties of BaTiO3 Ceramics Sintered by High-pressure Approaches

Dense BaTiO3 ceramics were prepared using two high-pressure approaches.The grains did not excessively grow sintering by the high-pressure assisted sintering,and the grains still retained in the range of nanometer size.The sintering temperature obviously decreased when the raw powders were consolidated under high pressure and then sintered at ambient pressure.With grain size reducing from 400 nm to 50 nm,the dielectric constant decreased from 3 000 to 1 900,which could be explained by the tetragonality decreasing and the existence of a low-permittivity,nonferroelectric grain boundary layer in dense BaTiO3 ceramics.In addition,with reducing the grain size,the character of the ferroelectric-paraelectric phase transition transformed from a sharp peak to abroad area.The broad areas exhibited the characteristic of diffuse phase transitions at the transition regions.