介电谱在镥铝石榴石晶体中的应用

Application of dielectric spectroscopy in lutetium aluminum garnet crystal

为研究提拉法生长的镥铝石榴石单晶中的缺陷,采用波长为254 nm、功率为36 W的4根低压汞灯灯管,室温下在距离镥铝石榴石单晶样品15 cm远处对其进行紫外光辐照24 h,之后在样品上下两个7 mm×7 mm表面镀上电极,置于一夹具内,夹具内部由机械泵维持真空环境,外部由液氮控制温度,利用HP4194A阻抗分析仪对紫外光辐照前后的镥铝石榴石单晶进行介电谱测试。实验结果表明:紫外光辐照后的镥铝石榴石单晶的介电损耗峰出现弛豫,由该弛豫峰对频率的依赖关系表明这种介电弛豫行为是属于偶极子取向极化的弛豫型响应,由此根据偶极子的弛豫机理推断在镥铝石榴石单晶的晶格中可能存在一定数量的缺陷。

To study the defects in lutetium aluminum garnet crystal grown by Czochraski method,samples are irradiated under ultraviolet light（UV） by 4 low pressure mercury lamps（254 nmwavelength,36 W） placed 15 cm from the samples for 24 h at room temperature. Later,the 7 mm×7 mm surface of these samples is coated with silver films and then placed inside an evacuated cylindrical chamber,the exterior of which is submerged in liquid nitrogen during the experiment.Then, dielectric spectroscopy measurement is performed on both the irradiated and the original samples with a HP4194 A impedance analyzer. The results show that the dielectric loss peaks of the irradiated samples appear relaxation effects. The dependency of these relaxation peaks on frequency indicates that the dielectric relaxation behavior is a response to the orientation polarization of a permanent dipole. It therefore can be inferred, according to the relaxation mechanism of the dipole, a certain number of defects may exist in lutetium aluminum garnet crystal.