VARIED ATMOSPHERE COMPENSATION - EXPLORING THE ROLES OF BARIUM AND BISMUTH IN (BA,BI,NB)-DOPED TIO2 VARISTORS

A novel (Ba,Bi,Nb)-doped TiO2 ceramic was previously proved to be pote ntially useful as a varistor material. The present work attempts to cl arify the roles of the dopants, Ba and Bi. Varied atmosphere compensat ion is an effective method to achieve the goal. The results show that varied atmosphere compensation had only a little influence on grain gr owth and microstructures in the interior of the sintered samples, wher eas the varistor properties were affected greatly. Samples compensatin g with Ba are more beneficial to the boundary barrier than samples com pensating with Bi only. Furthermore, samples compensating with both Ba and Bi are better than those compensating with Ba only. This is induc ed by different degrees of Bi evaporation and Ba diffusion from sinter ed compacts when sintering proceeds at high temperature.