Dielectric and polarized Raman spectroscopic studies on 0.85Pb(Zn1/3Nb2/3)O3-0.15PbTiO3 single crystal

Abstract

Tetragonal-cubic phase transition has been investigated in relaxor-ferroelectric 0.85Pb(Zn1/3Nb2/3)O3-0.15PbTiO3 single crystal using dielectric and Raman spectroscopy. A detailed analysis of the dielectric data suggests that the transition is of second order. In the tetragonal phase (P4mm), all the modes predicted by group theory were found in the Raman spectra and were assigned based on the symmetry and polarization configuration. Frequencies of several modes were found to disappear while a few modes exhibited discontinuous change across the phase transition temperature TC ∼473 K. While in the high temperature cubic phase (Pm3¯m) no first order Raman spectrum is expected, the presence of several Raman peaks at elevated temperature suggests substitutional disorder causing the appearance of symmetry-forbidden Raman bands. The line-width of A1(TO) mode at 273 cm−1 shows anomalies across TC and the intermediate temperature T*. Furthermore, based on the temperature dependence of total integrated intensities of all the modes in the polarized and depolarized spectra, the Burns temperature TB, T*, and TC are identified at 650, 525, and 473 K, respectively.