Dense Sm and Mn Co-Doped BaTiO₃ Ceramics with High Permittivity

The structure, valence state, and dielectric properties of (Ba_1-Sm)(Ti_0.99Mn_0.01)O₃ (BSTM) (x = 0.02‒0.07) ceramics prepared via a high temperature (1400 °C/12 h) solid state reaction were investigated. A homogeneous and dense microstructure was observed in all samples. With increasing Sm content, the crystal structure changed from tetragonal (x ≤ 0.06) to cubic (x = 0.07) and unit cell volume (V₀) decreased continuously, which was mainly due to the substitution of Ba²⁺ ions by smaller Sm³⁺ ions in the perovskite lattice. Electron paramagnetic resonance investigation revealed that Mn ions were reduced from high valence to low valence under the role of Sm³⁺ donor, and only Mn²⁺ ions were observed at x = 0.07. The Curie temperature (T_c) moved to lower values, from 105.5 down to 20.4 °C, and the x = 0.07 sample satisfied Y5V specification with high permittivity (ε'_RT > 13,000) and low loss (tan δ < 0.03).