Abstract
R‐T and I‐V characteristics of single grains and grain boundaries in large‐grained BaTiO3 PTC ceramics were studied with a two‐probe technique using a micromanipulator and fine Al wire. The PTC originates in the grain boundary only and behaves differently in each boundary. Even below Tc, the ceramic resistance depends almost entirely on the boundary. I‐V characteristics in the boundary follow Ohm's law and conduction by a space‐charge‐limited current with a trap, using different applied voltages. The PTC anomaly relates to activation of the trap in the boundary, not to barrier height. A band model in the intergranular layer, with dielectric BaTiO3 and the trap, is proposed.