Raman scattering on the B-site order controlled by A-site substitution in relaxor Perovskite ferroelectrics

The control of the B-site order of Pb(Mg1/3Nb2/3)O-3 was studied by the par tial substitution at the A site by both donor La3+/Bi3+ and acceptor K+1. D ifferent A-site cations and their concentrations were chosen to modify the chemical order at the B site. The Raman scattering results over a wide temp erature range (-190-300 degrees C) confirm that the first order scattering is dominant in phonon bands resulting from both ordered regions and disorde red matrix. The degree of the B-site order is estimated by the full width a t half maximum of the phonon bands associated with the ordered regions, spe cifically, the highest frequency breath-type A(1g) mode of the BO6. It is c oncluded that the order is enhanced with the donor La3+/Bi3+ doping, while with the acceptor K+1 doping, the order is suppressed. The effect of A-site substitution on the B-site order has thus been elucidated. (C) 2000 Americ an Institute of Physics. [S0021-8979(00)05419-0].