DIRECT OBSERVATION OF THE DOUBLE SCHOTTKY-BARRIER IN NIOBIUM-DOPED BARIUM-TITANATE BY THE CHARGE-COLLECTION CURRENT METHOD

Charge-collection (CC) current was measured at a single grain boundary , which exhibited positive temperature coefficient of resistivity (PTC R) effects, in 0.1-mol%-Nb-doped BaTiO3. The CC current systematically reversed across the grain boundary above the Curie point, which indic ated the presence of a double Schottky barrier (DSB) at the grain boun dary. In contrast, the CC current was constant across the grain bounda ry below the Curie temperature. The result obtained from the CC curren t measurement agrees with the classical DSB model in donor-doped BaTiO 3, indicating the PTCR effects.