Effect of excess TiO2 addition on the PTC properties of Ba0.99Y0.01TiO3-0.001MnO based ceramics

BaTiO3 is a typical ceramic with a positive temperature coefficient of resistivity (PTC). The grain conductivity of BaTiO3 is associated with doping, and the grain boundary plays an important role in the PTC effect. In this study, Ba0.99Y0.01TiO3-0.001MnO-xTiO2 (x=0.01-0.07) ceramics were synthesized by the conventional solid-state reaction method in air atmosphere. The influence of excess TiO2 on the crystal structure, microstructure, binding energy and the PTC characteristics were investigated by XRD, SEM, EDS, XPS and impedance spectroscopy, respectively. The results showed that excellent room-temperature resistivity and resistance jump ratio (Rmax/Rmin) up to 84 Ω cm and 1.6×105 could be obtained possibly associated with the two different roles played by Ti ions at the grain boundaries.