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Dielectric Relaxation and ac Conductivity of Na/K Excess (Na$ _{0.53}$K$ _{0.47}$)(Nb$ _{0.55}$Ta$ _{0.45}$)O$ _{3}$ Piezoelectric Ceramics
New Phys.: Sae Mulli 2020; 70: 1~6
Published online January 31, 2020;
© 2020 New Physics: Sae Mulli.

Jin Soo KIM, Ho Sueb LEE*

Department of Physics, Changwon National University, Gyeongnam 51140, Korea
Correspondence to:
Received October 2, 2019; Revised December 2, 2019; Accepted December 9, 2019.
cc This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
We have prepared lead-free (Na$ _{0.53+x}$K$ _{0.47+x}$)(Nb$ _{0.55}$Ta$ _{0.45}$)O$ _{3}$ (NKNT) ceramics with Na/K excess by using a solid-state reaction method. To enhance the piezoelectric and dielectric properties of NKN based system, it is necessary to excess Na and K ions in A-sites. The dielectric and the piezoelectric properties were enhanced for $x$ = 0.005. We investigated the temperature and the frequency dependences of the dielectric response and the electrical conductivity. Cubic-tetragonal ($T_{c}$) and tetragonal-orthorhombic ($T_{O-T}$) phase transition were found at 148 $ ^{\circ}$C and 40 $ ^{\circ}$C, respectively. Especially, the piezoelectric-improved NKNT ceramic had a low-frequency dielectric dispersion and low electrical conductivity. We investigate the frequency and the temperature dependences of the complex dielectric response and the electrical conductivity for NKNT ceramics with an optimum Na/K excess.
PACS numbers: 77.22.-d, 77.84.Ek, 77.84.-s
Keywords: (Na$_{0.5}$K$_{0.5}$)NbO$_3$, NKN, Lead-free, Dielectric, Piezoelectric, Phase transition, Ta ion addition

May 2020, 70 (5)
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