Preparation and properties of the Ni/PTC ceramic composite
Ni/PTC陶瓷复合材料的制备和性能

In order to decrease the room-temperature resistivity of PTC materials, Ni/BaTiO$_{3}$ composite was synthesized by decomposition of NiC$_{2}$O$_{4}\cdot$2H$_{2}$O/BaTiO$_{3}$ precursor, which was prepared by precipitating nickel oxalate into BaTiO$_{3}$ suspension. Structure and property of the composite were investigated. The results showed that the composite has a porous and uniform structure. Nickel was dispersed in grain boundary and cavity in the form of fine particles. Oxidation of nickel would induce high room--temperature resisitivity and spoil PTC effect. It can be avoided by protection of graphite during sintering. The sintered composite has a very low room--temperature resistivity and little PTC effect. With the absorption of oxygen in grain boundary, PTC effect of the Ni/BaTiO$_{3}$ composite can be effectively renewed by heat--treatment in air. The porose structure and the fine dispersal of nickel were in favor of the renewing of PTC effect.