Anomaly in temperature dependence of current voltage characteristics of BaTiO₃ ferroelectric frozen phase

The dielectric and the current conduction properties of BaTiO₃ epitaxial films that posses Schottky contacts at one surface and a quasi-ohmic contacts at the other surface are measured. The dielectric constant is found to increase monotonically up to, at least, 200 °C. An increase of resistance or a constant resistance is found near T_C only in the reverse bias current, which would correspond to the positive temperature coefficient of resistance (PTCR) effect in ceramics. The heterostructures used in the present suggest the PTCR effect as the contribution of the reverse bias conduction.