Relaxor Phase Evolution of (Bi<sub>0.5</sub>Na<sub>0.5-<i>x</i></sub>K<i><sub>x</sub></i>)TiO<sub>3</sub> Ceramics due to K Ion Substitution and Their Corresponding Electrical Properties
Sam Yeon Cho,
Eun-Young Kim,
Sun Yong Kim,
Thuy Linh Pham,
Jin Kyu Han,
Da Som Song,
Ha-Kyun Jung,
Jong-Sook Lee,
Ki-Seok An,
Jongsun Lim,
Sang Don Bu
Affiliations
Sam Yeon Cho
Department of Physics, Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju 54896, Korea
Eun-Young Kim
Department of Physics, Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju 54896, Korea
Sun Yong Kim
Department of Physics, Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju 54896, Korea
Thuy Linh Pham
School of Materials Science and Engineering, Chonnam National University, Gwangju 61186, Korea
Jin Kyu Han
Thin Film Materials Research Center, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea
Da Som Song
Thin Film Materials Research Center, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea
Ha-Kyun Jung
Thin Film Materials Research Center, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea
Jong-Sook Lee
School of Materials Science and Engineering, Chonnam National University, Gwangju 61186, Korea
Ki-Seok An
Thin Film Materials Research Center, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea
Jongsun Lim
Thin Film Materials Research Center, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea
Sang Don Bu
Department of Physics, Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju 54896, Korea
We synthesized lead-free piezoelectric (Bi0.5Na0.5-xKx)TiO3 (BNKT) ceramics using a conventional solid-state reaction method. We have investigated the structural and electrical properties of the materials with x = 0.05 to 0.40. The X-ray diffraction (XRD) analysis suggests that the BNKT ceramics show the transition from rhombohedral to tetragonal structure. The ratio of the tetragonal structure increased continuously in accordance with the increasing composition of x. The sample of x = 0.10 showed a similar ratio between the tetragonal and rhombohedral structures. Frequency-dependent dielectric measurements showed a sort of relaxor properties emerged with increasing x composition, this effect may be interpreted in terms of the formation of polar nano-regions (PNRs) in samples. The value of remnant polarization (Pr) decreases rapidly as x increases beyond the point of x = 0.10 from 25.3 μC/cm2 to 5.9 μC/cm2. On the contrary, as for inverse piezoelectric coefficient (d33*), a higher value of d33* (336 pm/V) at x = 0.10, was observed when compared with x = 0.05 (d33* = 51 pm/V). These results can be explained by the formation of PNRs and their variations with the external applied field. We here propose a possible mechanism showing the effects of dipolar defects, which can be resulted from the K ion substitution on (Bi,Na)TiO3 (BNT) ceramics.
