Investigation of microstructure and dielectric properties of LaMnO₃ doped BaTiO₃ ceramics

The microstructure and dielectric properties of LaMnO₃ (LM) doped BaTiO₃ (BT) ceramics have been investigated. By adding LM, (1–x)BT-xLM (x = 0–0.5) ceramics keep in a single-phase solid-solution state, but gradually transform from tetragonal structure to pseudocubic one, and much denser microstructure is obtained. As for dielectric properties, when x ≤ 0.1, the Curie temperature of BT-LM shifts to a lower temperature and the permittivity maximum is lowered with the increase of LM content, which are attributed to the introduction of La₂O₃ and the degradation of tetragonality, respectively. When x > 0.1, BT–LM presents a typical relaxation behavior. Colossal permittivity appears as x reaches 0.4, which is related to large number of giant electron-pinned defect-dipoles (${\text{Mn}}^{4+}\cdot 2e-V_{\text{O}}^{\cdot \cdot }$) and existence of grain-boundary segregation. Detailed analyses show that 0.5BT–0.5LM possesses the highest permittivity maximum (41,683) and widest temperature range (– 42 to 300 °C) with permittivity larger than pure BT at 100 kHz. Therefore, 0.5BT–0.5LM can be a very promising candidate as colossal permittivity material.