Structure and dielectric properties of Lu-doped SrBi2Ta2O9 synthesized by the molten salt method

Abstract

Lu-doped SrBi2Ta2O9 (SrBi2-xLuxTa2O9 where x = 0, 0.025, 0.05, 0.75 and 0.1) powders were synthesized by combination of molten salt method and solid-state route. FTIR, Raman and XRD techniques were performed to follow the transformation of reactants into the desired products. Characterization of all samples shows pure and single-phase orthorhombic structured materials obtained with plate-like morphology that is composed of fine and coarse-grained particles. The prepared powders were pressed and sintered at different temperatures up to 1200?C. Microstructure of the sintered samples is also likely to be affected by doping. The first study of dielectric measurements describes the effect of the application of DC bias, at roomtemperature, on the undoped and Lu-doped ceramics and shows that there is little or no effect of DC bias. The sample SrBi1.95Lu0.05Ta2O9 had maximal dielectric constant (??) and minimal dielectric loss (tan?). In the second part of this work, the temperature dependence of ?? and tan_ was considered. It was concluded that Lu-doping not only reduces the Curie temperature, but also brings a diffused phase transition, showing a crossover between displacive and diffusive behaviour.