ZnO压敏陶瓷中缺陷的介电谱研究

Study of intrinsic defects in ZnO varistor ceramics by dielectric spectroscopy

从理论上证明了介电松弛过程在介电谱上等效于电子松弛过程,认为室温下105Hz处特征损耗峰起源于耗尽层处本征缺陷所形成的电子陷阱.在-130—20℃范围内测量了三种配方ZnO陶瓷的介电频谱,发现ZnO压敏陶瓷室温下105Hz处的特征损耗峰在低温下分裂为两个特征峰,认为它们起源于耗尽层中的本征缺陷(锌填隙或/和氧空位)的电子松弛过程.发现ZnO-Bi2O3二元系陶瓷特征峰仅仅由锌填隙引起,而ZnO-Bi2O3六元系压敏陶瓷特征峰则由锌填隙和氧空位共同引起.分析了热处理温度和气氛对试样介电谱的影响,发现锌填隙浓度对热处理温度更敏感,而氧空位浓度对热处理气氛更敏感.

In this paper defect structure was investigated by dielectric response of pure ZnO ceramics,binary and multi-element ZnO-Bi_2O_3 based varistor ceramics with the help of broad band dielectric spectroscopy.It is found that no loss peak appears at room temperature in pure ZnO ceramics,while there is one and two loss peaks in the binary and multi-element ZnO-Bi_2O_3 based varistor ceramics,respectively.According to relaxation polarization theory and electronic relaxation theory,it is obtained that electronic relaxation process is equivalent to relaxation polarization in dielectric spectroscopy and the characteristic peak near 105Hz at room temperature arises from relaxation process of electrons trapped by oxygen vacancies and zinc interstitials.Based on the difference in the dependence of the two loss peaks on the temperature and the atmosphere of heat treatment,aging mechanism is explained as the desorption of oxygen.