Mechanism of the giant permittivity in Sm modified SrTiO 3 sintered at different atmospheres

The pure and Sm modified SrTiO 3 ceramics have been fabricated by solid state reaction method at different atmospheres, including ambient, reduced and oxidized conditions. All studied ceramics are in single cubic perovskite phase with high bulk density, where Sm doped ceramics possess decreased grain size. The room temperature permittivities of Sr 0.97 Sm 0.02 TiO 3 and Sr 0.98 Sm 0.02 TiO 3 sintered in N 2 were found to be on the order of 25120 and 13370 at 1 kHz with dielectric loss being 0.044 and 0.008. The giant permittivities were associated with the increase of Ti 3+ ions, which were due to the combination of Ti 4+ ions and electrons. With increasing Ti 3+ ions, the concentration of Ti 4+ ions, Ti 3+ ions and V_O^·· reach the balance where the defect dipoles [ Ti^4+·e - V_O^·· - Ti^4+·e ] were created, responsible for the low dielectric loss.