Phase structure and quasi-single-domain mechanism in Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals near morphotropic phase boundary

Based on the domain configuration analysis, we demonstrate that orthorhombic (O) phase is a structural bridge between the rhombohedral (R) and tetragonal (T) phase in Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) crystals near the morphotropic phase boundary (MPB), as illustrated in the composition-temperature phase diagram. After poling along the polar direction, domain patterns in PMN-0.30PT, PMN-0.33PT, and PMN-0.37PT single crystals are found to accord with quasisingle-domain configurations (1R*, 1O*, and 1T*) after removal of the electric field. Furthermore, by the thermodynamic theory analysis, the quasisingle-domain states present one dominant domain and other adjacent domains owing to partial depolarization. Our results provide a reliable and nondestructive method to identify the phase structures near the MPB region in the PMN-xPT and other similar relaxor-ferroelectric single crystals.