Effect of temperature on the dielectric and ferroelectric properties of a nanocrystalline hexagonal Ba4YMn3O11.5−δ ceramic synthesized by a chemical route

Abstract

A Ba₄YMn₃O_11.5−δ (BYMO) nano-crystalline powder was prepared by a novel wet chemical method using metal nitrates and glycine as starting materials. The as-synthesized powder was characterized by thermo-gravimetric analysis (TGA), phase formation and the crystalline nature was confirmed by X-ray diffraction (XRD), morphology and elemental composition are determined by field emission scanning electron microscopy (FE-SEM) and energy-dispersive spectroscopy (EDS), the particle size observed by transmission electron microscopy (TEM) is found to be 45 ± 10 nm. The BYMO material has a high dielectric constant which increases with temperature and decreases with frequency. The PE hysteresis loop indicates that the material displayed a temperature dependent ferroelectric property. The variable oxidation state of manganese (Mn^3+/4+) creates electronic heterogeneity which maintains the oxygen concentration, conductivity and polarization of the material. Impedance spectroscopic data reveals that the resistance of a grain boundary is relatively higher than that of grains and these resistances decrease rapidly on increasing temperature. The electrical properties of the BYMO ceramic support the internal barrier layer capacitor (IBLC) model of a Schottky barrier between grains and grain boundaries which also explains the high dielectric permittivity of the ceramic.