Saturation Effect of Al(NO3)3 Dopant on Residual Voltages of ZnO Based Varistor Ceramics
The additive of Al(NO3)3 was doped into ZnO varistors in order to reduce their residual voltages. Some of doped Al3+ enter the ZnO grains and infill into the vacancies of Zn2+ ions in the crystal lattice. Then, the resistances of ZnO grains decrease, which finally results in lower residual voltages of varistor samples. However, when most of Zn2+ vacancies inside the ZnO crystal lattice are filled with Al3+, redundant Al3+ ions inside ZnO grains will increase the grains’ resistances contrarily. In this paper, ZnO and Al(NO3)3 binary ceramics sintered at 1300 °C for 2, 4 and 8 hours were studied. The J-E curves of the investigated samples exhibit weak non-linear characteristics which may be due to the formation of grain boundary. Moreover, The resistivity dependence of ZnO ceramics on Al addition behaves as a U-type curve and the lowest resistivity of ZnO ceramics is obtained with doping 0.25mol% Al3+.
Wei Pan and Jianghong Gong
W. C. Long et al., "Saturation Effect of Al(NO3)3 Dopant on Residual Voltages of ZnO Based Varistor Ceramics", Advanced Materials Research, Vols. 105-106, pp. 310-313, 2010