Raman scattering in relaxor Pb(Zn1/3Nb2/3)O3

The raman spectra of relaxer ferroelectrics in the single crystal Pb(Zn1/3Nb2/3)O-3 (PZN) have been measured with the 90 degrees scattering geometry over a wide temperature range between 100 K and 773 K and over a frequency range up to 1000 cm(-1) The Raman-active modes exist well above the diffuse transition temperature of about 413 K (the cubic phase) implying that the space group of the cubic phase in PZN is not Pm (3) over bar m. It is found that far above room temperature, the Raman spectra in the X(ZZ)Y and X(ZX)Y geometries are different, whereas below room temperature they are almost the same.