Wolframium Doped SrBi2Ta2O9—Effect on Microstructural, Dielectric and Ferroelectric Properties

Abstract

The structural, dielectric and ferroelectric studies of SrBi 2 Ta 2 O 9 (SBT) ferroelectric ceramics, partially substituted with wolframium (W) for tantalum (Ta), are reported in this paper. Polycrystalline samples of wolframium substituted SBT ceramics of compositions SrBi 2 (W x Ta 1 − x ) 2 O 9 (SBWT); x = 0.0–0.20 were synthesized by solid state reaction method. X-ray analysis confirm that the single phase layered perovskite structure is maintained up to x = 0.05. The microstructural studies reveal that the average grain size increases with the increase in W- content. Dielectric properties studied as a function of temperature at 100 kHz show an increase in Curie temperature over the composition range of x = 0.025 to 0.20. The dielectric loss reduces significantly with wolframium addition. The temperature dependence of dc conductivity of the samples vis-à-vis wolframium content exhibits the typical negative temperature coefficient of resistance (NTCR) and a decrease in conductivity by as much as two to three orders of magnitude is observed. The ferroelectric properties improved with W-doping and the maximum value of remanent polarization was observed for composition with x = 0.075. The observed results have been discussed in terms of contribution from the cation vacancies which are introduced into the lattice structure so as to compensate the charge imbalance due to donor doping.