Internal barrier layer capacitance effect in hexagonal perovskite Ba4YMn3O11.5 ceramics

Ba4YMn3O11.5, a 12R hexagonal perovskite that consists of face-sharing Mn3O12 trimers isolated by single YO6 octahedral layers, is presented. The presence of locally 5- and 6-coordinated Y3+ and Mn4+ cations is observed in this structure. A high dielectric permittivity (epsilon(r) approximate to 1 x 10(4)), which is almost frequency independent over the similar to 1 x 10(2) to 1 x 10(5) Hz range from room temperature to 120 degrees 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.