Microstructure, morphology, and dielectric properties of in situ synthesized CCTO/CTO/TiO2 composite ceramics

CaCu3Ti4O12/CaTiO3/TiO2 (CCTO/CTO/TiO2) composite ceramics were fabricated by an in situ route and sintered at 1040 degrees C for 8 h. The micrographs of FESEM show that the ceramics are dense and delicate, with an average particle size of about 0.9-1.4 mu m. XPS found the existence of Cu+ and Ti3+, which was caused by the charge compensation reaction derived from part of Ti4+ ions entering the V"(Cu) to form the donor Ti''(Cu). The impedance analysis shows that excessive CTO and TiO 2 significantly reduce the grain boundary resistance of CCTO/CTO/TiO2 ceramics. Furthermore, it can be found that due to excessive CTO, TiO2 reacts with segregated CuO to form CCTO again and reduce the CuO concentration at the grain boundaries. Therefore, this significantly reduces the grain boundary width, resulting in a colossal dielectric constant of 9.0 x 10(5) at 30 Hz.