Antiferrodistortive Phase Transition in Pseudorhombohedral (Pb0.94Sr0.06)(Zr0.550Ti0.450)O3 : A Combined Synchrotron x-ray and Neutron Powder Diffraction Study

摘要

The controversies about the structure of the true ground state ofpseudorhombohedral compositions of Pb(ZrxTi1-x)O3 (PZT) are addressed using a6% Sr2+ substituted sample with x=0.550. Sound velocity measurements reveal aphase transition at Tc~279K. The temperature dependence of FWHM of (h00)pcpeaks and the unit cell volume also show anomalies around 279K even thoughthere is no indication of any change of space group in the synchrotron X-raypowder diffraction (SXRD) patterns. The neutron powder diffraction patternsreveal appearance of superlattice peaks below Tc~279K confirming the existenceof an antiferrodistortive phase transition. The Rietveld analysis of the roomtemperature and low temperature SXRD data below Tc shows that the structurecorresponds to single monoclinic phase in the Cm space group while the analysisof neutron powder diffraction data reveals that the structure of the groundstate phase below Tc corresponds to the Cc space group. Our analysis shows thatthe structural models for the ground state phase based on R3c space group withor without the coexistence of the room temperature monoclinic phase in the Cmspace group can be rejected.