MnO_2掺杂钛酸钡基PTC陶瓷的电子结构及其电性能研究  

Studies of electronic structures and electrical properties of BaTiO_3-based PTC ceramics doped with MnO_2

作　　者：周江[1,2] 方志杰[2] 邓文[1] 

机构地区：[1]广西大学物理科学与工程技术学院,广西南宁530004 [2]广西科技大学理学院,广西柳州545006

出　　处：《广西大学学报（自然科学版）》2015年第3期673-679,共7页Journal of Guangxi University（Natural Science Edition）

基　　金：国家自然科学基金资助项目(11265002;11464003);广西自然科学重点基金(2010GXNSFD013036)

摘　　要：为提高钛酸钡基PTC陶瓷的升阻比(ρmax/ρmin),采用固相反应法制备了以Y2O3为施主杂质,不同含量的Mn O2作为受主杂质的钛酸钡基PTC陶瓷样品;应用第一性原理方法计算了样品的能带结构、电子结构和Mn掺杂的形成能;测量了样品的正电子湮没寿命谱和电性能。计算结果表明:钛酸钡材料的价带顶和导带底分别位于特殊K点中X(0,0.5,0)点和Γ(0,0,0)点,属间接带隙,禁带宽度为1.59 e V;从形成能结果来看,Mn进入钛酸钡基陶瓷结构后会取代Ti位置。实验结果显示,随着Mn O2掺杂量的增加,样品晶粒内部的自由电子密度增大,陶瓷的晶界缺陷浓度增加,室温电阻率增大。Mn O2含量为0.03%mol的样品的升阻比最大,达到1.1×105,即掺入少量的Mn O2可明显改善钛酸钡基PTC陶瓷的升阻比。In order to increase the values ofρmax/ρmin for the BaTiO3-based PTC ceramics, a series of BaTiO3-based PTC ceramics were prepared by solid state reaction method. The PTC ceramics with Y2 O3 as their donor dopants were doped with different contents of MnO2 as acceptor. The band struc-tures, electronic structures, and the formation energies of the BaTiO3 ceramic samples were calculat-ed by the first-principle method. The positron lifetime spectra and electrical properties of the sam-ples were also measured. The calculation results show that the bottom of valence-band and the top of conduction-band in BaTiO3 are at X（0, 0. 5, 0）point and Г（0, 0, 0） point, respectively; Thus, the BaTiO3 has an indirect gap with the value of 1. 59 eV. The formation energies of the samples＆amp;nbsp;indicate that Ti is replaced by Mn in BaTiO3 . The experimental results show that with the increase of MnO2 content, the electron density in the grain, the concentration of defect of grain boundaries, andρ25 of the ceramics also increase. The ratio ofρmax/ρmin reaches a maximum value （1. 1×105） for the sample doped with 0. 03%mol MnO2 , that is, the ratio ofρmax/ρmin of the BaTiO3-based PTC ce-ramics can be improved by doping small content of MnO2 .

关 键 词：钛酸钡基PTC陶瓷 第一性原理 电子结构 微观缺陷 电性能 

分 类 号：TN373[电子电信—物理电子学]