Effect of Rare‐Earth Ions on Electrical Conductivity of BaTiO 3 Ceramics

Lattice constants, grain size, electrical conductivity, and luminescence were measured for sintered BaTiO 3 ceramics doped with 0 to 1.2 at.% rare‐earth ions. BaTiO 3 doped with low levels of rare‐earth ions contains grains 10 μm in size and has lattice constants nearly equal to those of undoped ceramics. In this case, rare‐earth ions occupy Ba 2+ sites and yield donors. When grain growth is inhibited by high doping levels or by insufficient sintering, the lattice constants change, the rare‐earth ions occupy both Ba 2+ and Ti 4+ sites, and, consequently, BaTiO 3 becomes insulative because of charge compensation.