BiNbO_4掺杂对BaTiO_3基陶瓷的改性效应研究

Investigation of the modulation effects of BiNbO_4 doping on BaTiO_3-based ceramics

对三元系统BaTiO3（BT）-Bi0.5Na0.5TiO3（BNT）-BiNb04的微结构和介电性能进行了研究。1％（摩尔分数）BNT掺杂使BT的居里温度由127℃大幅提高到140℃。BiNbO4掺杂显著降低了高温端的电容温度变化率，相反低温端的电容温度变化率升高。掺杂3％～4％（摩尔分数）BiNbO4的BT陶瓷满足X8R特性。烧结温度过高时，居里峰明显被抑制，居里温度向低温移动，而低温介电峰向高温移动。SEM结果表明，1％（摩尔分数）BiNbO4掺杂时，陶瓷晶粒细小且尺寸均匀。BiNbO4含量增大，陶瓷内部出现异常生长的第二相晶粒，且第二相比例随BiNbO4含量增加而增大。XRD分析表明，基质晶粒为BaTiO3,第二相包括Ba2TiO4、NaBiTi2O6及BaTiNb4O13。

In this paper, the microstructure and dielectric properties of ternary system BaTiO3 （BT）-Bi0.5Na0.5 TiO3 （BNT）-BiNbO4 were investigated. In the case of 1mol% BNT addition, the Curie point of BT ceramic is increased from 127-140℃. The temperature coefficient of capacitance at high temperature is markedly decreased with the addition of BiNbO4, whereas an enhancement in the temperature coefficient of capacitance at low temperature is observed. The EIA X8R specification is satisfied in the samples doped with 3%-4mol% BiNbO4. The dielectric peak at Curie point is suppressed evidently due to over-high sintering temperature. Moreover, the Curie point moves towards lower temperatures with the increase of sintering temperature. Simultaneously, the dielectric peak at low temperature is shifted towards higher temperatures. SEM indicates that fine and homogeneous grains are observed with 1mol% BiNbO4 addition. However, secondary phase grains appear with increasing BiNbO4 content, which are identified as Ba2TiO4,NaBiTi2O6 and BaTiNb4O13 by XRD. Moreover, the proportion of the secondary phase grains increases as the amount of BiNbO4 increases.