Phase transition and electrical studies of wolframium doped SrBi2Ta2O9 ferroelectric ceramics

In this study, crystalline structure, dielectric and impedance properties of SrBi2Ta2O9 (SBT) - based ferroelectric ceramics have been investigated with the substitution of wolframium/tungsten (W) onto the tantalum site. Wolframium doped SrBi2(WxTa1-x)(2)O-9 (0.0 <= x <= 0.20) ceramics were synthesized by solid state reaction method. The X-ray diffractogram analysis revealed that the substitution formed a single phase layered perovskite structure for the doping content up to x <= 0.05. The dielectric measurements as a function of temperature show an increase in Curie temperature (T-c ) over the composition range of x = 0.05 to 0.20. The W6+ substitution in perovskite-like units results in a sharp dielectric anomaly at the ferroelectric phase transition. Furthermore, the dielectric constant at their respective Curie temperature increases with wolframium doping. Both enhanced Curie temperatures and dielectric constants at the Curie points indicate an increase in polarizability, which could be attributed to the increased "rattling space" due to the incorporation of the smaller tungsten cations. The dielectric loss reduces significantly with tungsten addition. AC impedance properties vis-a-vis wolframium content has also been studied.