Title :
Electrical properties of ZnO/Bi2O3 two-layer composites
Author :
Ieda, Mirai ; Suzuoki, Y. ; Nakagawa, M. ; Mizutani, T.
Author_Institution :
Dept. of Electr. Eng., Nagoya Univ., Japan
fDate :
6/1/1990 12:00:00 AM
Abstract :
A ZnO/Bi2O3 two-layer composite formed by RF sputtering is studied as a model of a single-grain boundary in a ceramic ZnO varistor to clarify the mechanisms of degradation and nonlinear conduction and to realize a thin-film varistor. The current-voltage characteristics and the thermally stimulated currents (TSC) are measured. The composite under a reverse bias shows highly nonlinear conduction comparable to that in an actual ceramic varistor. The breakdown voltage of ZnO/Bi2O3 two-layer specimens increases with the thickness of the Bi2O3 layer and thus can be controlled by changing this layer. This is explained in terms of enhancement of the electric field at the ZnO/Bi2O 3 interface by space-charge accumulation in the Bi2O3 layer and at the interface. TSC for reverse-bias poling voltage flows in the direction of polarization at temperatures >120°C. This is explained by the space-charge accumulation in the Bi2O3 bulk and at the interface
Keywords :
bismuth compounds; ceramics; composite materials; sputtered coatings; thermally stimulated currents; varistors; zinc compounds; RF sputtering; ZnO-Bi2O3; breakdown voltage; current-voltage characteristics; degradation; electric field; nonlinear conduction; reverse-bias poling voltage flows; single-grain boundary; space-charge accumulation; thermally stimulated currents; thin-film varistor; two-layer composites; varistor; Bismuth; Ceramics; Current measurement; Current-voltage characteristics; Radio frequency; Sputtering; Thermal degradation; Varistors; Voltage control; Zinc oxide;
Journal_Title :
Electrical Insulation, IEEE Transactions on
