The role of SiO2 in semiconducting BaTiO3-based ceramics: Extension of the Jonker model and effect on the electrical properties

Abstract

BaTiO3-based ceramics with positive temperature coefficient of resistance (PTCR) recently gained in significance due to their application as cabin heaters in electrical vehicles. Although used as a sintering aid in BaTiO3 ceramics for decades, the effect of SiO2 on the electrical properties as well as the underlying physical mechanisms have not been investigated in detail. Here, we systematically study the influence of SiO2 on PTCR properties, but also on the resistance development at temperatures below the PTC regime, which has hardly been given attention to so far. Using capacitance-voltage measurements, we determine temperature dependent grain boundary potential barrier parameters. By combining these results with x-ray diffraction measurements and resistance-temperature properties, we propose a model describing the resistance evolution throughout the whole temperature range from room-temperature up to the PTCR regime. Further, we show that electrical field strength increases with higher SiO2 content, accompanied by a reduced voltage sensitivity of resistance.