Influences of Sr(2+) Doping on Microstructure, Giant Dielectric Behavior, and Non-Ohmic Properties of CaCu(3)Ti(4)O(12)/CaTiO(3) Ceramic Composites

The microstructure, dielectric response, and nonlinear current-voltage properties of Sr(2+)-doped CaCu(3)Ti(4)O(12)/CaTiO(3) (CCTO/CTO) ceramic composites, which were prepared by a solid-state reaction method using a single step from the starting nominal composition of CCTO/CTO/xSrO, were investigated. The CCTO and CTO phases were detected in the X-ray diffraction patterns. The lattice parameter increased with increasing Sr(2+) doping concentration. The phase compositions of CCTO and CTO were confirmed by energy-dispersive X-ray spectroscopy with elemental mapping in the sintered ceramics. It can be confirmed that most of the Sr(2+) ions substituted into the CTO phase, while some minor portion substituted into the CCTO phase. Furthermore, small segregation of Cu-rich was observed along the grain boundaries. The dielectric permittivity of the CCTO/CTO composite slightly decreased by doping with Sr(2+), while the loss tangent was greatly reduced. Furthermore, the dielectric properties in a high-temperature range of the Sr(2+)-doped CCTO/CTO ceramic composites can be improved. Interestingly, the nonlinear electrical properties of the Sr(2+)-doped CCTO/CTO ceramic composites were significantly enhanced. The improved dielectric and nonlinear electrical properties of the Sr(2+)-doped CCTO/CTO ceramic composites were explained by the enhancement of the electrical properties of the internal interfaces.