Current limiting and negative differential resistance in indium oxide based ceramics

Indium oxide based ceramics with bismuth oxide addition were sintered in air in the temperature range 800–1300 °C. Current–voltage characteristics of In2O3–Bi2O3 ceramics sintered at different temperatures are weakly nonlinear. After an additional heat treatment in air at about 200 °C samples sintered at a temperature within the narrow range of about 1050–1100 °C exhibit a current limiting effect accompanied by low-frequency current oscillations. It is shown that the observed electrical properties are controlled by the grain-boundary barriers and the heat treatment in air at 200 °C leads to the decrease in the barrier height. Electrical measurements, scanning electron microscopy and X-ray photoelectron spectroscopy results suggest that the current limiting effect observed in In2O3–Bi2O3 may be explained in terms of a modified barrier model; the observed current limiting effect is the result of an increase of barrier height with increasing electric field, due to additional oxygen absorption. It is found that In2O3–Bi2O3–Co3O4–Cr2O3 ceramic exhibits current–voltage characteristics with negative differential resistance due to Joule microheating.