Grain boundaries of semiconducting SrTiO3 and BaTiO3 ceramics synthesized from surface-coated powders

The chemical and electrical features of the grain boundaries in polycrystal line SrTi0.99Nb0.01O3 (ST) and BaTiO3 (BT) ceramics, which were synthesized by hot-press sintering Na- and Mn-coated semiconducting ST and BT powders, respectively, were investigated. Because of the excess negative electric c harges formed near grain boundaries, electrostatic potential barriers were formed near the grain boundaries. The electrical features of the grain boun daries in ceramics are very sensitive to the amount of the coating material . When the amount of the coating material was increased from 0 to 5 wt%, th e threshold voltage of the ST ceramics and the resistivity jump ratio of th e BT ceramics increased from 0.7 to 81.0 V/cm and from 1.0 to 2.0 x 10(3), respectively. The electrical features of the grain boundaries are related t o their chemical characteristics.