Semiconducting barium titanate ceramics prepared by using yttrium hexaboride as sintering aid

Nb-doped BaTiO3 semiconducting ceramics have been prepared at 1150 °C by employing YB6 as the sintering aid. The low-temperature sintered samples exhibit a positive temperature coefficient of resistivity (PTCR) effect. The room-temperature resistivity and the magnitude of PTCR effect depend on the amount of YB6 added, the Nb2O5 content and the sintering conditions. At 1 mol% of YB6, the sample has a low room-temperature resistivity and a resistivity jump of about 104. Transmission electron microscope studies revealed that the intergranular region between the crystalline BaTiO3 grains has an amorphous structure. Y, Ba and Ti are present in the intergranular region but no Y is detectable in the crystalline grains. A liquid phase is believed to be present during sintering and it helps to facilitate the densification process and to enhance the PTCR effect.