Varistor behavior of the system SnO2•CoO•Ta2O5•Cr2O3

In this work the system (98.95 - x)% SnO2 + 1% CoO + 0.05% Ta2O5 + x% Cr2O3 (mol %) was studied, with x = 0.05 and 0.10, prepared by the conventional method of oxides mixture, and sintered at 1300 and 1350 degreesC for 2 h. The non-linear J versus E electrical characteristics (alpha = 25) were obtained in the Ta2O5 and Cr2O3-CoO doped highly densified SnO2 ceramics. X-ray diffraction analysis showed that these ceramics are apparently single phase. Electrical properties and microstructure are highly dependent on the Cr2O3 concentration and on the sintering temperature. Excess of Cr2O3 leads to porous ceramics destroying the electrical characteristics of the material. Dopant solid solution formation in the SnO2 may be responsible for the formation of electrical barriers in the grain boundaries. (C) 2002 Kluwer Academic Publishers.