Mechanisms of electroconductivity in Na0.5Bi0.5TiO3 single crystals

Abstract

The complex impedance spectra Z*(w) of Na_0.5Bi_0.5TiO₃ single crystals were studied in the temperature interval 600-900 K and in the frequency range 5-5∙10⁵ Hz. Experimental data are presented as diagrams in the complex (Z'-Z") plane and discussed on the basis of the of equivalent circuits approach. In the studied temperature-frequency diapason the hodographs consist of two arcs and are described by using an equivalent circuit, containing two serially connected parallel RC circuits. Shift of the arcs centers downward from Z' axis, caused by distribution of the impedance relaxation times t, is accounted by substitution of usual capacities for generalized ones. The high-frequency arc on the hodographs is associated with conductivity in the bulk of the sample. The low-frequency arc reflects the charge transfer in the near electrode regions.