Bi4-xLaxTi3O12-SrBi4Ti4O15,共生结构铁电材料拉曼光谱研究

在常温下，对La掺杂共生结构铁电陶瓷Bi_4-xLa_xTi_3O_12-SrBi_4-yLayTi_4O_15［BLT-SBLT(x+y),x+y= 0.00, 0.25,0.50,0.75,1.00,1.25,1.50］进行了拉曼光谱研究.结果表明，在掺杂量低于0.50时，La只取代类钙钛矿层中的Bi，当掺杂 量高于0.50后，部分La开始进入(Bi_2O_2)^2+层. La取代(Bi_2O_2)^2+层中的部分Bi以后，(Bi_2O_2)^2+层结构发生变化 ，原有的绝缘层和空间电荷库的作用减弱，导致材料剩余极化下降. La掺杂量增至1.50时，样品出现弛豫铁电性，这与30cm^-1以下模的软化相对应，说明La掺杂可引起材料 的结构相变. 关键词： Bi4-xLaxTi3O12-SrBi4Ti4O15 La掺杂 声子模 拉曼频移

Study on Raman spectra of Bi_4-xLa_xTi_3O_12-SrBi_4-yLayTi_4O_15 intergrowth ferroelectrics

The Raman spectra of lanthanum-doped intergrowt h ferroelectric ceramics Bi_4-xLa_xTi_3O_12-SrBi_4-yLayTi_4O_15［BLT-SBLT(x+y),x+y= 0.00, 0.25,0.50,0.75,1.00,1.25,1.50］achieved at room temperature were inve stiga ted. The results show that La was substituted the Bi ions in the pseudo-perovski te blocks when La content is lower than 0.50 When La content is higher than 0.50, so me of La ions are incorporated into the (Bi_2O_2)^2+ blocks. The inco rporation of La ions into the (Bi_2O_2)^2+ layers would change th e structure of (Bi_2O_2)^2+ and destroy its functions as the insu lating layers and the space charge storage, which leads to the decrease of the remnant polarization. The relaxation characteristics observed in BLT-SBLT(1.50) are consistent with the softening of the mode lower than 30 cm^-1. This in dicates that La-doping may bring about the structural phase transition.