EFFECT OF LEAD-OXIDE ON NIOBIUM-DOPED TITANIA VARISTORS

The effect of PbO on Nb-doped TiO2 varistors was investigated. It was found that the PbO dopant had significant effect on the varistor properties of Nb-doped TiO2 ceramics. There existed an optimal range of PbO starting from 0.25 to 1 mol% for the nonlinear I-V characteristics of the 0.25 at.% Nb-doped TiO2 ceramics. Within this PbO range, an effective boundary energy barrier of about 0.70 eV was created which yielded nonlinear I-V characteristics with alpha = 7.6. In contrast, alpha values of the samples containing PbO dopant outside this optimal range are only about 2 to 3. The effect of PbO on TiO2 varistors was analyzed by impedance spectroscopy, C-V and dielectric measurements, and X-ray diffraction, as well as scanning electron microscopy. The results are discussed in the text.