关键词: 弛豫, 铁电晶体, 介电常数, 电畴结构, 晶体生长, 钛酸铅

Sinle crystals of 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3(PZNT91/9) with a maximum size of φ30×25mm^3 were grown by a modified Bridgman technique with a PbO-based flux using an allomeric seed crystal. The obtained typical (001) plane crystal without macroscopic defects was 20×15 mm^2 in size. The crystal structure was determined by X-ray diffraction (XRD) measurement. The electrical properties and the domain structure of PZNT single crystals were studied using a precision LCR meter and a polarized light microscope respectively after the crystal orientation was determined by Laue X-ray diffraction measurement. The results showed that the dielectric constant before poling of PZNT91/9 single crystal was high (about 2500～5000 within a wafer at room temperature). Increasing temperature led to a phase transition from the tetragonal ferroelectric phase to the cubic paraelectric phase with the transition temperature (Curie temperature tc) being about 190℃. Dielectric constants dependence on the temperature showed apparent frequency chromatic dispersion and the temperature of maximum dielectric constant (tm) decreased with the increase of frequency. The heterogeneity of domain structure and the twin electric domains were also observed. These results confirm that the modified Bridgman method is useful for the mass production of large crystals of PZNT91/9.

Key words: RELAXATION, FERROELECTRIC CRYSTALS, DIELECTRIC CONSTANT, CRYSTAL GROWTH