Off-stoichiometry, structural-polar disorder and piezoelectricity enhancement in pre-MPB lead-free Na_0.5Bi_0.5TiO₃-BaTiO₃ piezoceramic

Abstract

With increasing industrial acceptance of Na_0.5Bi_0.5TiO₃ (NBT)-based lead-free piezoceramics, there is a need to develop insights into the way different factors influence the microstructural–structural–piezoelectric property correlations. In this work, we have examined the role of structural disorder on the piezoelectric response of the pre-MPB composition x = 0.03 of the well-known solid solution series (1-x)Na_0.5Bi_0.5TiO₃-(x)BaTiO₃. Using off-stoichiometry on the A-site as a tuning parameter to vary the structural disorder, which we characterize in terms of the fraction of the “cubiclike phase” or variation in the thermal parameter of the A-site cation, it is shown that the piezo response maximizes for the composition, which retains an optimum degree of disorder after poling. Our study confirms the important role of structural disorder in enhancing piezoelectric response in ferroelectric ceramics