Properties of Semiconductive Barium Titanates

The resistivity of barium titanate which is usually of the order of 10 9 ∼10 12 ohm-cm, may be remarkably reduced with suitable control in valency. The valency-controlled barium titanate, whose resistivity is of the order of 10∼10 4 ohm-cm at room temperature, shows anomalous positive character in the temperature dependency of the resistivity. For example, the resistivity of barium titanate containing 0.1 mol. percent of cerium abruptly changes by 10 4 between 120°C and 150°C. Some semiconductive properties and their relations to the crystal transition and the composition of the materials are reviewed, for the valency-controlled barium titanates, and assumptions are proposed for the role of additives on the reduction of the resistivity of the barium titanates.