Grain boundary character dependence of potential barrier in barium titanate

Positive temperature coefficient of resistivity (PTCR) effect is directly measured in bicrystal specimens of Nb-doped BaTiO₃ to examine its grain boundary character dependence and to clarify the nature of the potential barrier formed at grain boundaries. The coherency of grain boundaries is evaluated from a geometric method based on the coincidence of reciprocal lattice points (CRLP). Larger PTCR effects were obtained for random grain boundaries rather than coherent boundaries. The formation of the potential barrier is discussed from an analysis of the resistance-temperature characteristics.