Nanoscale investigation on electric field induced ferroelectric phase transitions in the rhombohedral PMN-PT single crystal

The excellent piezoelectric property of Pb(Mg1/3Nb2/3)O₃-PbTiO₃ (PMN-PT) single crystals has attracted increasing attentions for their application in electromechanical devices. Generally, the electric field induced phase transition is an important contribution to the piezoelectric response. Understanding the pathway of electric field induced phase transition is essential for the practical application of PMN-PT crystals. Here, evolution of the domain structure and surface screening charges during phase transitions in the (001) oriented 0.72PMN-0.28PT crystal were studied at nanoscale via piezo-response force microscopy (PFM) and Kelvin probe force microscopy (KPFM). In combination with confocal polarized Raman spectroscopy, electric field induced phase transitions were locally studied. PFM tip bias poling in 0.72PMN-0.28PT single crystal results in a rhombohedral to monoclinic phase transition. And the monoclinic phase relaxes back to the rhombohedral at elevated temperatures. Our work provides nanoscale investigations on the electric field induced phase transition, and will be instructive for the practical application of PMN-PT single crystals.