Study On Ni/Al/BaTiO₃-based PTC Composites Ceramics

BaTiO3 is a kind of good insulated material, whose room temperature resistance can reach 1010~1012??cm.Since PTCR ceramics of BaTiO3 was found,many scientist deeply researched in principle,property and application of it to make it development quickly but the reason why it was not used widely is the higher room-temperature resistivity.In this article, the method of lowering the room-temperature resistivity is introduced by Ni/Al/BaTiO3 composites. In this work, the traditional high temperature solid phase reaction process was used to prepare PTCR ceramics of BaTiO3. Ni/Al/BaTiO3 composites were fabricated by adding Ni and Al into BaTiO3 calcined powder. To achieve low room-temperature resistivity, the samples were sintered at reducing atmosphere. To achieve better PTC effect, the samples needed heat treatment which was in air atmosphere.In this article, the effects of the Ni content, Al content on the electric properties and PTC effect of the Ni/Al/BaTiO3 composites were discussed, and the influences of technology crafts on the composites were analyzed. By analyzing the data of the experiments, the parameters of the processing condition were manipulated.Through the experiment the conclusion is obtained. The BaTiO3 with doping Ni can reduce the r.t. resistivity but the Rmax/Rmin is also redeced. Because of the effect of compensation when Al2O3 by oxygenated Al go into the lattice, the r.t. resistivity is first low then high and Rmax/Rmin is first high then low.With doping Ni and Al,1300oC is the best sinter temperature. The best temperature of heat treatment is 800oC. In this condition, r.t. resistivity can be reduced to2??cm, the Rmax/Rmin can hold on 70 .