Phase transitional behavior and piezoelectric properties of the orthorhombic phase of Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

We report on the observation of an orthorhombic ferroelectric phase in 0.67Pb(Mg1/3Nb2/3)O-3-0.33PbTiO(3) single crystals, whose polarization is along [011] direction and stability can be altered by poling conditions. We studied the piezoelectric properties on poled [011] crystals, in both monodomain and polydomain states, and found that the piezoelectric d(32) coefficient, which is the piezoelectric response in perpendicular to the poling direction, is positive in both cases. Based on the phenomenological theory, we show that this is possible in a crystal with the electrostrictive coefficients Q(11)>Q(44)-Q(12). (C) 2001 American Institute of Physics.