Abstract :
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 = 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 { h 00 } and 1 / 2 { h k 0 } 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 = 1.93 , 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 E a = 0.06 eV and T v f = 396 K . The relaxor behavior was attributed to the local polar ordering on A-sites.
