Relaxor behavior of K0.5La0.5Bi2Ta2O9 ceramics

Potassium lanthanum bismuth tantalate (K0.5La0.5Bi2Ta2O9), a new relaxor ferroelectric was synthesized via the solid-state reaction route. X-ray structural studies along with Rietveld refinement confirmed it to be an n=2n=2 member of the Aurivillius family of oxides and the refined lattice parameters are a=5.512(2)nm, b=5.504(2)nm and c=25.072(4)nm. The appearance of 1/2{h00}1/2{h00} and 1/2{hk0}1/2{hk0} type superlattice reflections in the electron diffraction patterns reflected the presence of ordered polar regions. A broad dielectric peak associated with frequency dependent dielectric maximum temperature was observed. The value of the diffuseness parameter γ=1.93γ=1.93, obtained from the fit of a modified Curie–Weiss law established the relaxor nature of the title compound. The dielectric relaxation obeyed the Vogel–Fulcher relation wherein Ea=0.06eV and Tvf=396K. The relaxor behavior was attributed to the local polar ordering on A-sites.