Evidence for MB and MC phases in the morphotropic phase boundary region of (1-x)[Pb(Mg1/3Nb2/3)O3]-xPbTiO3:: A Rietveld study -: art. no. 064102

We present here the results of the room-temperature dielectric measurements and Rietveld analysis of the powder x-ray diffraction data on (1-x)[Pb(Mg1/3Nb2/3)O-3]-xPbTiO(3)(PMN-xPT) in the composition range 0.20less than or equal toxless than or equal to0.45 to show that the morphotropic phase boundary region contains two monoclinic phases with space groups Cm (or M-B type) and Pm (or M-C type) stable in the composition ranges 0.27less than or equal toxless than or equal to0.30 and 0.31less than or equal toxless than or equal to0.34, respectively. The structure of PMN-xPT in the composition ranges 0less than or equal toxless than or equal to0.26 and 0.35less than or equal toxless than or equal to1 is found to be rhombohedral (R3m) and tetragonal (P4mm), respectively. These results are compared with the predictions of Vanderbilt & Cohen's theory.