Ba_(0.7)Sr_(0.3)TiO_3及其含Pb弥散相铁电体介电性能的研究

Dielectric properties of Ba_(0.7)Sr_(0.3)TiO_3 and Ba_(0.7-x)Pb_xSr_(0.3)TiO_3 ferroelectric ceramics with diffuse phase transition

用固相反应法制备了Ba0.7Sr0.3TiO3及其含Pb钛酸锶钡(BPST)陶瓷,运用修正的Smolenski的成分起伏理论和居里外斯定律,结合介电常数温度谱,研究了钙钛矿结构的BST及铅取代的钛酸锶铅钡(BPST)的弥散相,对其相变行为进行了分析,得出了的一些铁电模型参数。结果表明,该系列样品在弥散相变区的弥散指数α为1.29～1.88,相变区间为13.4～22.8℃;在顺电相其居里常量为1.25×105～1.47×105K数量级。当Pb含量为0.1(即Ba0.6Pb0.1TiO3)时,居里峰较宽,弥散相明显,故具有较高的调谐温度稳定性。另外铅的加入提高了铁电体的相变温度,从44℃上升到175℃。

Ba0.7Sr0.3TiO3 （BST） and Ba0.6-xPbxSr0.3TiO3 （BPST） ceramics derived from different amount of initial PbO excess were prepared by conventional solid-state method. Both permittivity and dielectric loss of all samples were measured in a temperature range. The substitution of Pb for Ba in BST system has revealed to raise the Cu- rie temperature from 44-175℃, and exhibited a diffused phase transition（DPT）, expecially for the ceramic Ba0.5 Pb0.1TiO3 which can improve the temperature stability of tunability for phase shifter than others. Moreover, some ferroelectric model parameters were calculated to interpret the DPT by adopting Smolenski＇s theory and Curie-Wise law. For example,values of diffuseness exponent a,Curie constant and transition region have varied from 1.29-1.88,from 1.25X 105-1.47×10^5K,and from 13.4- 22.8℃ ,respectively.