Structural and dielectric properties in (1-x) BaTiO ₃-x Bi (Mg _1/2 Ti _1/2) O ₃ ceramics (0.1 ≤ x ≤ 0.5) and potential for high-voltage multilayer capacitors

Structural and dielectric properties of (1-x)BaTiO₃-xBi(Mg _1/2Ti_1/2)O₃ (x = 0.1-0.5) were investigated to understand the binary system and utilize it for high-voltage, high energy density capacitors. The solubility limit for Bi(Mg_1/2Ti _1/2)O₃ in a BaTiO₃ perovskite was between x = 0.4 and x = 0.5. A phase with pseudocubic symmetry was formed for x = 0.1-0.4; a secondary phase developed at x = 0.5. Dielectric measurements showed highly diffusive and dispersive relaxor-like characteristics from 10 to 40 mol% of Bi(Mg_1/2Ti_1/2)O₃. These compositions also showed high relative permittivity with low-temperature coefficients of permittivity over a wide range of temperatures -100°C-600°C. Relaxation behavior was quantitatively investigated using the Vogel-Fulcher model, which revealed the activation energy of 0.17-0.22 eV. Prototyped multilayer capacitors of 18 mm × 17 mm × 4 mm dimensions with a capacitance of 12.5 nF at 1 kHz were successfully constructed and demonstrated multiple charge-discharge characteristics up to 10 kV.