铽改性铌酸锶钡晶体的介电谱研究

A DIELECTRIC SPECTROSCOPIC STUDY OF TERBIUM-MODIFIED SBN CRYSTALS

在5×10~2Hz 到5×10~8Hz 频率范围内测量了 Tb 改性的铌酸锶钡(SBN)晶体的室温介电常数,并以1×10~4Hz 的频率测量了这些介电常数从室温至居里温度以上的变化。对于 c 轴和 a 轴介电常数,都观测到了介电弛豫,但 c 轴介电弛豫频率明显低于 a 轴介电弛豫频率。对于不同的组份来说,介电弛豫频率随居里温度降低而降低。这些晶体的铁电—顺电相变是弥散性的,弥散程度随Tb 含量的增加而增高。

Dielectric constants of the Tb-modified SBN crystals were measured at roomtemperature in the frequency range from 5×10~2 to 5×10~8 Hz and at 1×10~4Hzfrom room temperature to above their Curie temperatures.Dielectric relaxationwas observed for both the dielectric constant along the c-axis and the a-axisbut the relaxation frequency for the c-axis is lower than that for the a-axis.For crystals with different compositions,the dielectric relaxationfrequencies d(?)rease with decreasing Curie temperature.The ferro-paraelectricphase transition in these crystals are diffusive,and the diffuseness increaseswith increasing the Tb-content.