Abnormal Grain Growth Free Strontium Barium Niobate by Microwave Assisted Sintering

Abstract

Strontium barium niobate (SBN) with the general formula SrxBa1-xNb2O6 having tetragonal tungsten bronze (TTB) structure is an exceptional and promising lead free ferroelectric material among the family of ferroelectrics. SBN exhibits ferroelectricity in a wide compositional range x = 0.32 – 0.82, compared to perovskite materials such as barium strontium titanate (BST) and barium titanate (BT), which exhibit ferroelectric phase in only one particular composition. Consequently, desired applications can be reached by tuning the Curie temperature (Tc). However, a serious problem encountered in densified SBN was the presence of an abnormal grain growth (AGG), associated duplex microstructure and pores. In the present work, these problems were successfully overcome by microwave assisted sintering. Structure, pure TTB phase analysis and lattice parameters of SBN were confirmed by X-Ray diffraction. AGG, associated duplex microstructure and pore free morphology of SBN were confirmed using scanning electron microscopy. The density of the microwave sintered SBN was found to be ∼94% of theoretical density which is higher than the reported value of conventionally sintered SBN. Dielectric studies of SBN were carried out to tune the Tc for all SBN compositions.