Growth of Pb((Zn1/3Nb2/3)0.91Ti0.09)O3 single crystals using an allomeric seed crystal and their electrical properties

Single crystals of Pb((Zn1/3Nb2/3)(0.91)Ti-0.09)O-3 (PZNT 91/9), 28 mm in diameter and 30 mm in length, have been successfully grown using a modified Bridgman technique with an allomeric seed crystal. X-ray fluorescence analysis (XRFA) measurement confirms that the effect of segregation is not serious. The segregation coefficient k for PbTiO3 content during crystal growth is 0.99, which causes some fluctuation in the composition along the growth direction. The fluctuation of composition and the complicated domain structure cause a variation of electric properties. Dielectric measurement indicates that PZNT 91/9 crystals exhibit an almost normal ferroelectric phase transition at similar to183 degreesC from the tetragonal phase to the cubic phase. In addition, a weak frequency-dependent ferroelectric-ferroelectric phase transition is observed at similar to85 degreesC, which is attributed to partial conversion of the rhombohedral phase to a tetragonal phase. The dielectric thermal hysteresis behavior and the existence of polarization above the Curie temperature verify that the phase transitions at similar to85degrees and 183 degreesC are first order with a slight diffuse character and first order, respectively. It is demonstrated that the effects of segregation can be decreased and the homogeneity of the obtained PZNT 91/9 single crystals can be improved by optimizing growth parameters.