A Raman scattering study of the antiferroelectric phase transition in (Sr0.70Ca0.30)TiO3 - art. no. 092302

The Raman scattering measurements on ceramic pellets of Sr0.70Ca0.30TiO3 (S CT 30) have been carried Out as a function of temperature from 290 K to 8 K . It is shown that below (236 +/-5 K), two additional lines appear around 7 9 and 128 cm(-1). Further, there is enhancement in the intensity of the mod es near 170 and 541 cm(-1) below (236 +/-5 K). The temperature at which the se changes occur in the Raman spectra of SCT 30 correlates very well with t he temperature at which the antiferroelectric superlattice reflections appe ar in the x-ray diffraction patterns. We propose that the additional modes are due to q not equal0 phonons that have become Raman active due to the fo lding of the corresponding special points into the zone center below the ce ll-doubling antiferroelectric phase-transition temperature.