Low voltage TiO2 varistors dopped with Ta2O5 and Cr2O3

Ta-Mn-Cr-doped TiO2 varistors were investigated with the purpose to clarify the roles of the dopants over the electric properties. The structural and electrical properties were studied by using scanning electron microscopy (SEM), I - V measurements and x-ray diffraction (XRD). The varistors; sintered at 1400 degreesC for 2h in air presented density values about 95% of the theoretical density. From the experimental results, it was observed that an optimum addition of Ta2O5 (> 0,05 mol %) leads to an improvement of the electrical characteristics, presenting a low breakdown voltage (0,15 - 0,3 V per grain boundary). The non - linearity coefficient increased from 2,6 to 8 as Cr2O3 was added and a low voltage (0,16 V per grain boundary) was observed. X-ray diffraction analyses showed the crystalline TiO2 rutile phase without no other phases. Therefore, low voltage Ta-Mn-Cr doped TiO2 varistors can be produced after adequate addition of Ta2O5 and Cr2O3 with excellent varsitors, properties.