Relaxor behavior of K0.5La0.5Bi2Nb2O9 ceramics

K0.5La0.5Bi2Nb2O9, a relaxor, was synthesized and the structural studies confirmed it to be an n=2 member of the Aurivillius oxides. The 1/2{h00} and 1/2{hk0} types of superlattice reflections in the electron diffraction patterns reflected the presence of ordered polar regions. A broad dielectric peak with frequency dependent dielectric maximum temperature was observed. The dielectric relaxation obeyed the Vogel-Fulcher relation wherein E-a=0.04 eV, T-f=428 K,and omega(o)=10(10) Hz. The diffuseness parameter gamma=2.003 established the relaxor nature and it was attributed to the A-site cationic disorder. The piezoelectric d(31) coefficient was 0.5 pC/N at 300 K and 2 pC/N at 480 K. (c) 2006 American Institute of Physics.