Phase transformation in relaxor-ferroelectric single crystal [Pb(Sc1/2Nb1/2)O3]0.58-[PbTiO3]0.42

The structure and phase transition behavior of monoclinic phase of the morphotropic phase boundary composition Pb(Sc1/2Nb1/2)O3]0.58-[PbTiO3]0.42 (PSN-42PT) in lead scandium niobate-lead titanate (PSN-PT) system have been investigated by in situ high-temperature polarized light microscopy (PLM) and x-ray diffraction (XRD) studies. Temperature-dependent powder XRD studies of PSN-42PT indicated monoclinic structure at 25 °C and cubic structure at 400 °C. It is observed that the room temperature monoclinic structure transforms to cubic structure through an intermediate tetragonal structure. The temperature-induced domain changes at the phase transition are investigated on (001) face of unpoled PSN-42PT crystal while heating as well as cooling the crystal on hot stage of the PLM. Under crossed polar condition, the striplike polar domains observed at lower temperature vanish gradually with increasing temperature. In the vicinity of ferroelectric transition temperature, the mesosize domains that appeared in the variable temperature PLM images are in accordance with the monoclinic-tetragonal-cubic transition sequence concluded by in situ high-temperature XRD studies. The domain rotation corresponding to the structural transformation sequence is concluded for the first time in the PSN-42PT.