Effect of Ti on the stability of phases in the (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 solid solution

Occurrence of the M-B-type monoclinic phase induced by the lattice distortion of the rhombohedral structure was evidenced by means of high-resolution x-ray powder diffraction, simplified integrate-breadth analysis and Rietveld refinement in the (1 - x)-Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) (PMN-xPT) ceramics with 15% less than or equal to x less than or equal to 30%. The obvious distortion of lattice along [h]c was observed in the composition range 23% less than or equal to x less than or equal to 30%, and increased with the Ti content. Rietveld refinements indicate that the MB-type monoclinic phase exists in the composition range 23% less than or equal to x less than or equal to 25%, and coexists, as a majority phase, with the M-C-type monoclinic phase for 26% less than or equal to x less than or equal to 30%. The rhombohedral (R) phase is stable in the composition range of 15% less than or equal to x < 23%. The effect of Ti on the lattice distortion and phase stability in the PMN-PT solid solution is discussed based on the model of competition between rhombohedral and tetragonal polar orders.