Impedance spectroscopy of СaCu3Ti4O12

N.A. Sekushin, L.A. Koksharova, N.A. Zhuk show affiliations and emails
Received 27 September 2019; Accepted 06 December 2019;
This paper is written in Russian
Citation: N.A. Sekushin, L.A. Koksharova, N.A. Zhuk. Impedance spectroscopy of СaCu3Ti4O12. Lett. Mater., 2020, 10(1) 72-77
BibTex   https://doi.org/10.22226/2410-3535-2020-1-72-77

Abstract

The structure of CaCu3Ti4O12 equivalent circuit reveals three processes possible within the material – reach-through conductivity and two overlapping polarization processes – electronic and dipole relaxation ones. Temperature dependencies of specific conductivity in the Arrhenius scale for CaCu3Ti4O12 samples of different thicknesses are linear and characterized by activation energy of 1.05 eV. Temperature dependencies of electric parameters of samples are at their minimums at T = 350 C, which can be explained by the changed polarization mechanism.Nowadays, due to an increased demand for miniaturization of electronic devices, electrotechnical ceramics exhibiting giant permeability, in particular, calcium copper titanate СаСu3Ti4O12 (CCTO), gain a considerable scientific interest of researchers around the world. Even though this is not a ferroelectric material, the compound demonstrates very high dielectric permeability (ε ~104 –105) within wide temperature (100 – 600 К) and frequency (20 Hz –1 MHz) ranges. Notwithstanding intensive studies on СаСu3Ti4O12, some of problems related to the effect of structural inhomogeneities of ceramics microstructure on electric properties of the compound remain open. As one can see from the experimental data, the traditionally analyzed electrical parameters of materials, such as the loss tangent of dielectric or permeability, show not only a dependence on the temperature or frequency of the electromagnetic field, but also on the geometrical parameters of samples due to the microstructure inhomogeneity of compound. As a result, on an example of СаСu3Ti4O12, integral parameters of media obtained through impedance spectroscopy are proposed for the use. The parameters under study have a clear physical meaning and do not depend on the geometry of the samples. The study proposes an equivalent circuit adequately describing electric properties of calcium copper titanate. The structure of the CaCu3Ti4O12 equivalent circuit reveals three processes possible within the material — through-thickness conductivity and two overlapping polarization processes — electronic and dipole relaxation. The temperature dependencies of the specific conductivity in the Arrhenius scale for CaCu3Ti4O12 samples of different thicknesses are linear and are characterized by an activation energy of 1.05 eV. The temperature dependencies of electric parameters of the samples exhibit minima at T = 350°C, which can be explained by the change in the polarization mechanism. It has been hypothesized that bipolar ionic conductivity created by oppositely charged ions occurs. The formation of electrically neutral associates of such ions cause the extremum of the electric parameters of the samples.

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