X-ray and Neutron Diffraction Investigations of the Structural Phase Transformation Sequence under Electric Field in 0.7Pb(Mg1/3Nb2/3)-0.3PbTiO3 Crystals

摘要

The structural phase transformations of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3(PMN-30%PT) have been studied using x-ray diffraction (XRD) and neutronscattering as a function of temperature and electric field. We observe thephase transformational sequence (i) cubic (C)-> tetragonal (T)-> rhombohedral(R) in the zero-field-cooled (or ZFC) condition; (ii) C->T-> monoclinic (MC)->monoclinic (MA) in the field-cooled (or FC) condition; and (iii) R->MA->MC->Twith increasing field at fixed temperature beginning from the ZFC condition.Upon removal of the field, the MA phase is stable at room temperature in the FCcondition, and also in the ZFC condition with increasing field. Severalsubtleties of our findings are discussed based on results from thermalexpansion and dielectric measurements, including (i) the stability of the MAphase; (ii) a difference in lattice parameters between inside bulk and outsidelayer regions; and (iii) the diffuse nature of the MA and MC phase transition.