Grain boundary electrical barriers in positive temperature coefficient thermistors

Resistance-temperature, current-voltage, and capacitance-voltage characteristics have been measured in niobium-doped barium titanate bicrystals. The analysis by device simulation reveals that potential barrier with a semiconductor-insulator-semiconductor structure can consistently interpret the observed characteristics rather than the double Schottky barrier. Absence of sub-ohmic behavior in the current-voltage characteristics and excess low-frequency capacitance at zero bias are caused by the spatially distributed traps at the insulating layer. (C) 1999 American Institute of Physics. [S0021-8979(99)03617-8].