Varistors based on Ta-doped TIO_2

摘要

The nonlinear current (I)-voltage (V) characteristics of titanium dioxide are examined when doped with small quantities (0.0,5-0.5 at. percent) of tantalum pentaoxide. For optimum compositions, the nonlinear coefficients are found to be in the range of 25-30 and the breakdown field strength (E_B) is ~4000 V/cm. The obtained a- and E_B-values are higher than the previously reported values for TiO_2 ceramics. The acceptor like surface states at the grain boundary adsorb oxygen during sintering and cooling, leading to formation of grain boundary barrier. The grain boundary barrier height (