Influence of lanthanum on the nonlinear I-V characteristics of SnO2: Co, Nb

Small quantities of rare earth element such as La or Y were incorporated into the SnO2-based primitive varistor compositions. This leads to increase in nonlinear coefficient, alpha from 9 to 30 and the breakdown voltage increases from 120 to 220 V/mm. The enhancement in alpha was expected to arise from the possible segregation of lanthanide ion due to its larger ionic radius to the grain boundaries, thereby modifying its electrical characteristics. Furthermore, the dopants such as La may help in adsorption of O' and O" at the grain boundaries [J. Appl. Phys. 84 (1998) 3700], thereby improving grain boundary barrier characteristics. (C) 2002 Elsevier Science B.V. All rights reserved.