Studying the Electrical properties and microstructure of the SnO2-Co3O4-Nb2O5 varistor doped with Lanthanum oxide (La2O3)

Abstract

SnO₂-Co₃O₄-Nb₂O₅-La₂O₃ varistor samples were prepared using standard ceramic technique by adding a definite rates of  Co₃O₄ and Nb₂O₅ to SnO₂ with different percentages of La₂O₃ from 0.050 to 0.200. It found that the addition of La₂O₃ decreases the samples density, and it showed no change in the phase structure of the samples. Also the addition of La₂O₃ to the samples decreased their average grain size. The electrical properties of the samples at different temperatures (10, 30, 60, 90, 120^oC) had studied. It was found that the all samples had varistor behavior. It also showed that, the breakdown electric field ( E_r) and non-linear coefficient (α)  were depended on the temperatures and the Lanthanum oxide concentration of the system. It had found that the best values of α and E_r appeared at the concentration of 0.050 La₂O₃.