Enhancement of dielectric properties by optimization of sintering condition in tungsten–bronze structured Ba₅SmTi₃Nb₇O₃₀ ferroelectric ceramics

Abstract

In this work, polycrystalline Ba₅SmTi₃Nb₇O₃₀ tungsten–bronze structured ferroelectric ceramics were synthesized by solid-state reaction technique at different sintering temperatures and durations. The X-ray diffractograms reveal the formation of the compounds in orthorhombic crystal system. The density of the compound is observed to increase with increase in sintering temperature and duration. Scanning electron microscopy (SEM) has been used for the microstructural investigation. Detailed dielectric properties of the compounds have been studied as a function of frequency and temperature. The variations of dielectric constant $\left( {\varepsilon \prime _r } \right)$ with temperature show that the compounds undergo a diffuse type ferro-paraelectric phase transition. The dielectric constant is found to increase with the increasing sintering temperature and duration. In all the samples, the variation of dielectric loss (tan δ) with temperature is observed to be almost constant initially but it increases as temperature is increased and a peak is observed only when the material is sintered at higher temperature for longer duration. The frequency dependence of dielectric constant and loss shows a decreasing trend up to nearly 10 kHz and beyond this frequency there is almost no variation. Also, the diffusivities of the samples have been calculated and it is found to increase with increasing sintering temperature and duration.