Effects of Ta~(5+) doping on microstructure evolution, dielectric properties and electrical response in CaCu_3Ti_4O_(12) ceramics

摘要

The effects of Ta~(5+) substitution on the microstructure, electrical response of grain boundary, and dielectric properties of CaCu_3Ti_4O_(12) ceramics were investigated. The mean grain size decreased with increasing Ta~(5+) concentration, which was ascribed to the ability of Ta~(5+) doping to inhibit grain boundary mobility. This can decrease dielectric constant values. Grain boundary resistance and potential barrier height of CaCu_3Ti_4O_(12) ceramics were reduced by doping with Ta~(5+). This results in enhancement of dc conductivity and the related loss tangent. Influence of charge compensations on microstructure and intrinsic electrical properties of grain boundaries resulting from the effects of replacing Ti~(4+) with Ta~(5+) are discussed. The experimental data and variation caused by the substitution of Ta~(5+) can be described well by the internal barrier layer capacitor model based on space charge polarization at the grain boundaries.