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https://doi.org/10.3938/NPSM.68.46
Impedance and Modulus Spectroscopy Characterizations of CuO-Added K$_{0.5}$Na$_{0.5}$NbO$_3$ Single Crystals
New Phys.: Sae Mulli 2018; 68: 46~54
Published online January 31, 2018;  https://doi.org/10.3938/NPSM.68.46
© 2018 New Physics: Sae Mulli.

Chan-Ku LEE*

Division of Mathematics, Science, and Computers, Kyungnam University, Changwon 51767, Korea
Correspondence to: ferrolee@kyungnam.ac.kr
Received August 10, 2017; Revised October 31, 2017; Accepted November 21, 2017.
cc This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Lead-free piezoelectric single crystals of K$_{0.5}$Na$_{0.5}$NbO$_3$(KNN)-$x$CuO ($x$ = 0.01, 0.02, 0.03, 0.04) were grown by using the Czochralski method. In the present study, the effect of the added CuO on the electrical behavior (impedance, modules, and conductivity relaxation mechanisms) of the KNN single crystals were carried out by using a complex impedance spectroscopy technique in the frequency range from 100 Hz to 5 MHz at temperatures from 30 to 650$^\circ$C. The Cole-Cole plots exhibited two impedance semicircles, one associated with the bulk and the other with the twin boundaries in the crystalline layers, and confirmed the presence of non-Debye-type relaxation. The scaling behavior of modulus ($M^{\prime\prime}$) spectrum confirmed that the relaxation dynamics was independent of both the dopant and the temperature. The relaxation nature of the modulus was governed by the hopping of oxygen-ion vacancies in electrical transport processes. The frequency dependence of the ac conductivity data followed a power law $\sigma_{ac}$ = $A\omega^s$ with $0.06 \leq s \leq 1$. The thermal activation energies ($E_a$) for the conduction of charge carriers in the cubic phase were calculated as 0.91 eV for $x$ = 0.01 and 0.84 eV for $x$ = 0.04.
PACS numbers: 82.45.Un, 77.22.Gm, 77.84.-s
Keywords: Single crystals, Impedance, Modules, Conductivity


January 2018, 68 (1)
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