Investigation of complex phase transitions of relaxor ferroelectric PMN-28PT under combined electric field and temperature stimuli

Relaxor ferroelectrics are an important class of functional materials because of the highly tunable dielectric permittivity, excellent temperature stability and low coercive field. However, the phase transition behaviors in relaxor ferroelectrics are very complex near the morphotropic phase boundary (MPB), especially under multiple fields of electric field and temperature. This study investigates the complex phase evolution of Pb(Mg 1/3 Nb 2/3 )O3-28%PbTiO 3 (PMN-28PT) single crystals near the MPB under thermal and electric field stimuli. Through comprehensive temperature-dependent characterization of the dielectric response, we observe the broad dielectric relaxation, which is attributed to the polar nanoregions (PNRs), as directly visualized via scanning transmission electron microscopy (STEM). The temperature-dependent P-E loops and S-E loops reveal the reduction in polarization magnitude and coercive field, increasing loop symmetry with temperature. Apart from that, a comparative study with conventional ferroelectric BaTiO 3 (BTO) reveals that PMN-28PT maintains thermal polarization retention. These findings provide new insights into the structure-property relationships governing relaxor behavior near MPB compositions.