(1−x)Pb(Ni1/3Ta2/3)O3−xPbTiO3 (x=0.00-0.80) ceramics were prepared by the columbite/wolframite method. The phase stabilitywas studiedby XRD analysis. No perovskite phase was formed for x=0.00. As PT content increases in the solid solution, the perovskite phase becomesdominant at room temperature. When x≥0.60, a pure perovskite phase was obtained. The temperature dependence of the dielectric propertieswas evaluated. A maximum of the dielectric constant of about 28,000 is observed for x=0.60 ceramics.

The phase structure and dielectric properties of (1−x)Pb(Zn1/3Ta2/3)O3-xBaTiO3 (x=0.00-0.40) ceramics were investigated. Pure perovskiteis obtained when x≥0.24.With increasing BT content, the diffuse phase transition and frequency dissipation of the dielectric constant increase andthe dielectric maxima temperature decreases. It is related to the existing of Ba (Zn1/3Ta2/3)O3 paraelectric microregions and the incomplete solidsolution reaction between Pb (Zn1/3Ta2/3)O3 and BaTiO3.

The temperature dependences of dielectric properties for [001] PMN-0.32PT single crystal and PMN-0.32PT ceramics under different dcelectric field (E) have been investigated. A new monoclinic phase can be induced by electric field with E=1.5-4.0 kV/cm, while heating, in [001] PMN-0.32PT single crystal. The phase transition process of single crystal is from rhombohedral to monoclinic, then from monoclinicto tetragonal, finally from tetragonal to cubic. With increasing electric field, all of the phase transition temperatures increased in the singlecrystal. Comparing with single crystal, no new phase is induced by electric field and temperature field in PMN-0.32PT ceramics. Similar tosingle crystal, the phase transition temperatures of PMN-0.32PT ceramics increased with increasing electric field. The difference of dielectricresponse under dc electric field between two materials is discussed. The formation of new monoclinic phase results from polarization rotationfrom [111] to [001] direction under electric field in single crystal.

PMN-PT crystals have been of considerable interest in recent years due to their excellent ferroelectric, piezoelectric, photoelectric propertiesand promising applications in various electric and electric-optical devices. However, the crucible leakage is usually a fetal limitation duringpreparation of the crystal. In this work, the PMN-PT crystals were prepared by Bridgman-accelerated crucible rotation technique (ACRT)method. The morphologies of the bottom surface of the PMN-PT crystal and the inner surface of the platinum crucible, in which the crystalgrew, were examined by scanning electronic microscope (JSM-840). The local composition was analyzed by EDAX spectrometer attachedto the scanning unit. Investigated results indicated that there are evident reaction between the platinum crucible and PbO-MgO-Nb2O5-TiO2melt during PMN-PT crystal growth, which is the main cause of crucible leakage. Another cause of the crucible leakage is due to the unequallydistorted platinum grain boundary.