Non-Ohmic conduction in In2O3-Bi2O3 ceramics

The semiconductor In2O3-Bi2O3 ceramics exhibit unusual behaviour: The current quasi-saturation (current limiting) in dc current-voltage characteristic is accompanied by low-frequency (∼1 Hz) current oscillations. In this paper some electrical properties of In2O3-Bi2O3 ceramics are studied and a mechanism of non-Ohmic conduction in this material is suggested. The electrical conduction is controlled by the grain-boundary potential barriers. Assuming that the barrier heights at different grain boundaries in a sample are not identical, the current quasi-saturation is explained qualitatively by capture of electrons at the interface states and respective increase in the height of key barriers. A mechanism of current oscillations is related to the current quasi-saturation. An increase in the height of key barriers leads to a raise of the voltage drop at these barriers and to Joule heating of barrier regions followed by decrease in the barrier height. The suggested mechanism of non-Ohmic conduction is confirmed by the obtained experimental data.