Dielectric properties and phase transitions of [001], [110], and [111] oriented Pb(Zn1/3Nb2/3)O3-6%PbTiO3 single crystals

Phase transformations of [001], [110], and [111] oriented Pb(Zn1/3Nb2/3)O3-6%PbTiO3 (PZN-6%PT) single crystals have been investigated by means of dielectric permittivity and loss, x-ray diffraction and depolarization current as function of temperature (from 250 to 500 K). The unpoled samples undergo R-T-C phase transition sequence during zero field heating (ZFH), where R, T, and C are rhombohedral, tetragonal, and cubic phases, respectively. Under electric field (0.5 kV/cm), an intermediate orthorhombic (O) phase is induced between the T and R phases in the field cooling (FC) process. This phase reappears during subsequent zero field heating of the poled sample (zero field heating after field cooling: ZFHaFC). The existence range of this O phase depends on both the crystal orientation and the measurement conditions (FC or ZFHaFC). Finally, for the [001] direction, it was found that the piezoelectric activity of the intermediate phase is the highest.