Ca^(2+)离子对Na扩散(Sr,Ca)TiO_3系电容-压敏陶瓷结构与性能的影响

EFFECTS OF Ca^(2+) ON STRUCTURE AND PROPERTIES OF Na-DIFFUSION (Sr,Ca)TiO_3 BASED CAPACITIVE-NONOHMIC CERAMICS

研究了Ca^(2+)离子(<50mol%)对Na扩散(Sr,Ca)TiO_3系电容-压敏陶瓷结构与性能的影响.XRD及IR吸收谱的实验结果表明,Ca^(2+)离子的加入,使立方钙铁矿结构发生畸变.这些结构上的变化,使得当Ca^(2+)离子含量增加时.晶粒电阻率上升,晶粒尺寸减小;在Ca^(2+)离子的含量约小于30mol%时,随Ca^(2+)离子含量的增加,经Na扩散热处理后陶瓷的视在介电系数增加,压敏电压降低.尤其是Ca^(2+)离子含量在10～30mol%时,ρ=6～9×10^(-2)(Ω·cm),ε_(eff)=9～13×10~4,V_(imA)<10V/mm,α>5.论文还对该陶瓷的结构与性能的关系进行了理论分析.

Effects of Ca^(2+) on structure and properties of Na-diffusion (Sr,Ca)TiO3 based capacitive- nonohmic ceramics have been investigated. XRD patters and IR spectra of samples comfirm that Ca^(2+) leads to the deformation of cubic perovskite structure of SrTiO_3, As a consequence,the grain resistivity increases and the grain size decreases with increasing Ca^(2+) content. In the range of less than 30mol% of Ca^(2+) ,with increasing Ca^(2+) content the apparent permissivity (ε_(eff)) increases and the threshold voltage(V_(lmA)) decreases for Na-diffused ceramics,which reveal low grain resistivity (ρ<10^(-2)Ω. cm), highly apparent permissivity(>100 000),lower threshold voltage(<10V/mm) and appropriately non-ohmic exponent (α> 5). Furthermore, the relationship between structure and properties is discussed.