Raman Scattering in (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3

Single crystals and ceramics of (1- x )PMN– x PT were synthesized in the whole concentration range from x =0 to x =1, and the temperature-concentration phase diagram of the system was determined from the dielectric measurement. The temperature dependences of the Raman spectra in the mixed crystals were measured. Raman active modes were observed even in the high temperature cubic phase above the ferroelectric transition point up to x =0.8. With the electron diffraction result that the superlattice reflections could not be observed above the morphotropic phase boundary ( x =0.35) [C. A. Randall, A. S. Bhalla, T. R. Shrout and L. E. Cross: J. Mater. Res. 5 (1990) 829], the present result indicates that the Raman active modes in the high temperature phase cannot be explained by the superstructure with the Fm 3 m symmetry due to the zone folding.