Local properties and phase transitions in Sn doped antiferroelectric PbHfO3 single crystal.

Pb(Hf1-xSnx)O3 single crystals with x= 0.23 were characterized using single-crystal X-ray diffraction in the wide temperature range. The information on the structure of two intermediate phases, situated between low temperature antiferroelectric and high temperature paraelectric phases has been obtained. The lower-temperature intermediate AFE2 phase is characterized by incommensurate displacive modulations in the Pb sublattice. The higher temperature intermediate IM phase is characterized by rotations of oxygen octahedra, primarily in the form of anti-phase tilts, which are also present in the lower-temperature AFE2 phase. For the same crystal, 119Sn Mossbauer effect in the temperature range from 300 K to 600 K has been used to study phase transitions mechanism. Two kinds of quadruple splitting have been found. It implies that two different environments of the central Sn ion exist. The observed two kinds of quadruple splitting do not disappear in the whole investigated temperature range which confirm that even far above TC the structure of paraelectric phase is locally non-centrosymmetric.