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

TL;DR

This study investigates the complex sequence of structural phase transformations in 0.7Pb(Mg1/3Nb2/3)-0.3PbTiO3 crystals under electric fields using X-ray and neutron diffraction, revealing multiple phases and their stability conditions.

Contribution

It provides detailed insights into the phase transformation pathways and stability of various phases in PMN-30%PT crystals under electric fields, using combined XRD and neutron scattering techniques.

Findings

Identified phase sequences under different conditions

Observed stability of the monoclinic MA phase at room temperature

Discovered differences in lattice parameters between bulk and surface regions

Abstract

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 neutron scattering as a function of temperature and electric field. We observe the phase 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->T with 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 FC condition, and also in the ZFC condition with increasing field. Several subtleties of our findings are discussed based on results from thermal expansion and dielectric measurements, including (i) the stability of the MA phase; (ii) a difference in lattice parameters between inside bulk and outside layer regions; and (iii) the diffuse nature of the MA and MC phase transition.