α-LiIO3的导电和介电特性的理论分析

本文考虑到α-LiIO₃电导的强烈各向异性,利用一维Debye-Hückel方程和泊松方程,导出了表观直流电导率,解释了文献[1]中有关α-LiIO₃的各种静态电导特性。推导中假设晶体界面处的电流由速率过程决定,并考虑了晶体两端的不对称性(电极性)。并援引文献[2]中有关动态介电常数的结果,部分解释了文献[1]中有关α-LiIO₃在加直流偏压场和不加偏压场的介电行为。文中指出,文献[3]中提到的联结α-LiIO₃晶体两极性面观察到持续不变的微弱电流,以及我们实验室观察到成极的铁电晶体铌酸锶钡也有同样现象,均来源于晶体极性电动势。这一电动势与晶体的自发极化P_s同时存在。

THEORETICAL ANALYSIS OF THE ELECTRICAL CONDUCTION AND DIELECTRIC BEHAVIOR OF α-LiIO3 SINGLE CRYSTALS

By using the Debye-Hückel equation and the Poisson equation, the almost one-dimensional ionic conductive behaviors of α-LiIO₃ have been analysed theoretically. The current across the boundaries between the crystal and metallic electrodes is con-sidered to be limited by rate processes. The asymmetry of the ± c-directions due to spontaneous polarization of the crystal has been taken into consideration. The explicit expression derived for the apparent DC conductivity is satisfactory in explaining the characteristic behavior of α-LiIO₃, e.g., the dependence of conductivity on applied voltage, as shown experimentally in [1]. The functional relationship between the AC dielectric constant and the bias field (cf. [1]) is interpreted partially by following the approach given in [2]. It is also pointed out that the weak current constantly flowing through the wire connecting the end surfaces of opposite polarity of an α-LiIO₃ single crystal (cf. [3]), as well as similar phenomena observed in our own laboratory on poled ferroelectrics such as Ba_xSr_1-xNb₂O₆(x～1/3), are caused by the crystal-line polarity EMF. This EMF coexists with the spontaneous, polarization P_s.