Internal Barrier Layer Capacitance Effect in Hexagonal Perovskite Ba₄YMn₃O_11.5 Ceramics

Ba 4 YMn 3 O 11.5, a 12R hexagonal perovskite that consists of face-sharing Mn 3 O 12 trimers isolated by single YO 6 octahedral layers, is presented. The presence of locally 5- and 6-coordinated Y 3+ and Mn 4+ cations is observed in this structure. A high dielectric permittivity (ε r ≈ 1 × 10 4 ), which is almost frequency independent over the ∼1 × 10 2 to 1 × 10 5 Hz range from room temperature to 120 °C, has been observed in ceramics of this material. AC impedance spectroscopy indicates that the internal barrier layer capacitance effect arising from the differing electrical properties of the grains and grain boundaries is responsible for the high dielectric permittivity of this non-ferroelectric material.