La掺杂Ba_(0.67)Sr_(0.33)TiO_3陶瓷高介电常数机制探讨

Study of high dielectric constant mechanism of La doped Ba_(0.67)Sr_(0.33)TiO_3 ceramics

添加稀土元素是提高Ba_(0.67)Sr_(0.33)TiO_3陶瓷材料介电性能的一种最常用有效的方法。本文着重研究了La掺杂诱发Ba_(0.67)Sr_(0.33)TiO_3高介电常数机制。研究表明:适量的稀土La掺杂(0.2≤x≤0.7)使陶瓷介电常数显著提高,显著改善了介电温度稳定性。根据电流-电压(J-V)特性可知,适量La掺杂可使陶瓷达到最佳半导化,掺量太少或太多时陶瓷具有良好绝缘性。通过肖特基(Schottky)势垒模型及电学微观结构模型分析发现表面或晶界势垒高度、耗尽层厚度和晶粒尺寸是影响材料介电常数的主要因素。

It is a common and effective method to enhance the dielectric properties of BST ceramics by adding rare-earth elements. In this paper, it is important to analyze the mechanism of the high dielectric constant behavior of La doped BST ceramics. The results show that proper rare earth La dopant ( 0.2≤ x ≤0.7) may greatly increase the dielectric constant of BST ceramics, also flatted the dielectric peak and improve the temperature stability evidently. According to the current-voltage ( J-V) characteristics, the proper La doped BST ceramics may reach the better semi-conductivity. When the less and more La doping, the ceramics are insulators. By the Schottky barrier model and electric microstructure model to find that the surface or grain boundary potential barrier height, the width of depletion layer and grain size do play an important role in impacting dielectric constant. Proper La doping improves the carrier concentration reducing the depletion layer thickness and finally does a great contribution to the high permittivity of BST ceramics.