Effects of glass-additives on the properties of Ni/ceramic PTC composites

The effects of glass additives on the sintering and properties of Ni/(Ba0.92Sr0.08)TiO3 composites were investigated. Due to the addition of glass additives, Ni/cerarnic composites with low room-temperature resistivity and obvious PTC effect were obtained at a low sintering temperature. It was shown that glass-additives could form liquid phase that aided the solution and diffusion of solid atoms, acting as sintering aids to accelerate the sintering and lower the sintering temperature. The room-temperature resistivity decreased first and increased later with the increasing content of glass-additives, which was explained by two functions of glass-additives, decreasing interface contact resistance as sintering aids and adding volume resistance as insulators. Moreover, a suitable amount of glass-additives could enhance the PTC effect unexpectedly, which was attributed to the decrease of the contact resistance existing at the ceramic/ceramic interface.