Experimental study on the mechanism of BaTiO3-based PTC–CO gas sensor

The n-type semiconducting BaTiO3-based positive temperature coefficient of resistivity (PTCR) ceramics is a potential CO gas sensing material with its high temperature NTCR region. The impedance spectroscopy was employed to analyze the resistance evolution of grain and grain boundary in atmospheres for the PTCR ceramics with various Curie point. The XPS studies were carried out at the temperatures from room temperature to 340 °C to understand the sensing characterization of BaTiO3-based PTCR ceramics. It is indicated that the sensing mechanism for the PTC–CO gas sensor is due to oxygen desorption at the grain boundary or an increase in charge carrier density and related chemical defects, which are based on the fluctuation of the potential barrier of the grain boundary.