Electric-field-induced phase transitions of (1-x)PbMg(1/3)Nb(2/3)O(3)-xPbTiO(3) crystals studied by optical methods.

The phase transitions of as-grown (1-x)PbMg(1/3)Nb(2/3)O(3)-xPbTiO(3) (PMN-xPT) crystals with PT compositions of x = 0.31 and 0.38 under a dc electric field were observed in a polarization microscope. The optical transmissions of the crystals under dc electric fields were measured in the wavelength region around their optical absorption edges. The band gaps of the orthorhombic and tetragonal phases under the applied electric field were obtained. By combining both of the optical methods, the phase transition from the tetragonal to the orthorhombic phase was observed in PMN-0.38PT crystals when the electric field along the 110 direction reaches up to 300 V mm(-1). Whereas the PMN-0.31PT crystals undergo the pseudo-phase-transition under a dc electric field along the 110 direction. The pseudo-phase-transition possibly stems from the reorientation and growth of microdomains in PMN-0.31PT crystals.