Effect of reoxidation annealing on the PTCR behaviour of multilayer Nb5+-doped BaTiO3 ceramics with a Ni internal electrode

Abstract

The effects of reoxidation annealing on the electrical properties and the positive temperature coefficient of resistance (PTCR) effects of multilayer Ba1.005(Ti1−x Nbx)O3 (BTN) ceramics sintered at different temperatures from 1100 to 1160 °C for 2 h in a reducing atmosphere and reoxidized at various temperatures in the range 500–900 °C were investigated. The results indicated that the room-temperature (RT) resistance of the BTN ceramics reoxidized at different temperatures first increased slowly and then quickly with the increase in the reoxidation temperature. Meanwhile, the resistance jump of the samples increased first and then decreased with the increase in the reoxidation temperature. In addition, the PTCR effect could be improved by prolonging the reoxidation time. Finally, the samples reoxidized at a low temperature of 600 °C after sintering at 1160 °C in a reducing atmosphere exhibited a significant PTCR effect, with a resistance jump of 3.5 orders of magnitude, along with a low RT resistance of 0.38 Ω. Additionally, the influences of the reoxidation temperature and time on the grain resistance and grain-boundary resistance were investigated using complex-impedance spectroscopy.