Influences of Sr Doping on Microstructure, Giant Dielectric Behavior, and Non-Ohmic Properties of CaCuTiO/CaTiO Ceramic Composites.

The microstructure, dielectric response, and nonlinear current-voltage properties of Sr-doped CaCuTiO/CaTiO (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 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 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, while the loss tangent was greatly reduced. Furthermore, the dielectric properties in a high-temperature range of the Sr-doped CCTO/CTO ceramic composites can be improved. Interestingly, the nonlinear electrical properties of the Sr-doped CCTO/CTO ceramic composites were significantly enhanced. The improved dielectric and nonlinear electrical properties of the Sr-doped CCTO/CTO ceramic composites were explained by the enhancement of the electrical properties of the internal interfaces.