Diffusion potentials in BaTiO3 and the theory of ptc materials

Abstract

We present two methods for calculating the potential profiles of depletion layers in ferroelectric materials. The simplified method is valid for materials possessing a high permittivity and with the electric field parallel to the polarization. The second method is valid for low permittivity materials as well and can be adapted to any orientation. We applied these methods to a study of the 001-001 interfacial barrier on semiconducting BaTiO3. Below the Curie point the calculations are in agreement with the resistivity-temperature behavior of doped, air-sintered ceramics. The theory does not predict a large resistance discontinuity at the Curie point. We discuss several refinements which may account for this discrepancy. The most plausible seems to be the piezoelectric charge compensation resulting from lattice distortion and grain boundary clamping.