Multi-scale domain structure observation and piezoelectric responses for [001]-oriented PMN-33PT single crystal

Multiple phase coexistence contributes to the extraordinary piezoelectric behavior of (1-x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃ (PMN–xPT) near the morphotropic phase boundaries (MPBs). By incorporating an optical path of crossed polarized light (PLM) into the commercialized Piezoelectric Force Microscope (PFM) (named as PLM-PFM system), in situ domain structure observation from micro- to nanoscale, as well as measurement of the piezoelectric behavior for individual domains can be realized. For 001]-oriented single crystal of 67Pb(Mg_1/3Nb_2/3)O₃-33PbTiO₃ (PMN-33PT), fine domain boundary structures of rhombohedral (R), tetragonal (T), and monoclinic (M) phases are revealed. Measurements of the electric field-induced displacement as a function of the applied DC electric field (V_DC) are performed for domains with different polarization vectors. Values for the electric field-induced displacement are in descending order for c-domains of the M, R, and T phases. For an individual phase of T or M, the displacement increases when the angle between the polarization vector and the applied electric field decreases. The multi-scale perspective of the domain structures and the corresponding piezoelectric response helps in understanding the ultra-high piezoelectric performance for PMN-PT single crystals near MPB.