弛豫基铁电单晶0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3的制备与 性能研究

用改进的Bridgman法，在加入助熔剂的条件下，生长出最大尺寸为φ30×25mm^3的铌锌酸铅-钛酸铅固溶体单晶0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3]。无宏观缺陷的晶片的典型尺寸为20×15mm^2。晶体的单晶性及其结构用X射线衍射法加以研究。所得晶体用Laue衍射法定向，取(001)晶片进行性能表征。研究了材料的介电性能，并用偏光显微镜观察了(001)晶片的电畴结构。结果表明，室温下材料的介电常数较大，为2500～5000。随着温度的升高，材料发生四方铁电相—立方顺电相的相变，相变温度为190℃左右。单晶的介电温谱呈现明显的频率色钐现象，同时，介电常数最大值的温度tm随着频率的升高而降低，观察到了电畴结构的不均匀与孪生现象。

Study on crystal growth and electrical properties of relaxor-based ferroelectric single crystal 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3

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.