Cationic ordering in lead samarium magnesium niobate

Abstract

Pyrochlore-free Sm2O3-doped/undoped Pb(Mg1/3Nb2/3)O-3 ceramics were fabricated and their cationic ordering structures were investigated by XRD and TEM. In the X-ray diffraction patterns, only fundamental diffraction peaks were observed for the undoped Pb(Mg1/3Nb2/3)O-3, while the (h+1/2 k+1/2 1+1/2) superlattice reflections were also observed for the Sm2O3-doped Pb(Mg(1/3)nTb(2/3))O-3 In the SAED patterns, the (h+1/2 k+1/2 1+1/2) superlattice reflections as well as the fundamental diffraction spots were observed for both of the undoped and the Sm2O3-doped Pb(Mg1/3Nb2/3)O-3, but the intensities of the superlattice reflections were stronger for the Sm2O3-doped Pb(Mg1/3Nb2/3)O-3. In the centered dark-field images, ordered domains of > 50 nm were observed only for the Sm2O3-doped Pb(Mg1/3Nb2/3)O-3 It has been therefore experimentally assured that the Sm2O3-doping enhances the 1:1 ordering of Mg2+ and Nb5+ ions in Pb(Mg1/3Nb2/3)O-3. These experimental results are discussed on the basis of charge compensation mechanism.