pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Physics: Sae Mulli 2015; 65: 657-663

Published online July 31, 2015 https://doi.org/10.3938/NPSM.65.657

## Effects of Neodymium Substitution on the Structural and the Electrical Properties of Bi$_{4}$Ti$_{3}$O$_{12}$ Ceramics

Gi Ppeum CHOI1, Sam Yeon CHO1, Do Hyun JEON1, Sang Don BU*1, Gyoung Ja LEE2, Min Ku LEE2

1 Department of Physics, Chonbuk National University, Jeonju 561-756, Korea
2 Nuclear Materials Development Division, Korea Atomic Energy Research Institute, Daejeon 305-535, Korea

Correspondence to:sbu@jbnu.ac.kr

Received: June 26, 2015; Revised: June 30, 2015; Accepted: June 30, 2015

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

Bismuth-layer-structured ferroelectric/piezoelectric Bi$_{4-x}$Nd$_{x}$Ti$_{3}$O$_{12}$ (BNdT) ceramics in which the Nd substitution was controlled from $x$ = 0.25 to 1.00 were prepared by using the conventional solid-state-reaction method. Structural analysis by using X-ray diffraction (XRD) showed that all the BNdT ceramics had a polycrystalline structure without second phases, which was consistent with the data for Bi$_{4}$Ti$_{3}$O$_{12}$ (JCPDS No.~35-0795). We found that the BNdT ceramics had grains with elongated shapes. The change in the orientation ratio of $a-b$ plane in the grains with increasing Nd substitution was found to be similar to the changes in their electrical properties. In particular, a notable improvement in the electrical properties was observed in the $x$ = 0.75 - 0.90 composition ratio of the BNdT ceramics. For the Bi$_{3.1}$Nd$_{0.9}$Ti$_{3}$O$_{12}$ ($x$ = 0.90) ceramics, the values of the dielectric constant and the piezoelectric coefficients exhibited maximum values of about 209 and 15 pC/N, respectively. On the other hand, with increasing Nd concentration, the phase transition temperature ($T_{c}$) continuously decreased from 613 $^\circ$C (Bi$_{3.75}$Nd$_{0.25}$Ti$_{3}$O$_{12}$, $x$ = 0.25) to 218 $^\circ$C (Bi$_{3.00}$Nd$_{1.00}$Ti$_{3}$O$_{12}$, $x$ = 1.00). These results suggest that controlling the Nd substitution in BNdT ceramics is essential for changing the dielectric constant and piezoelectric coefficients of bismuth-layer-structured piezoelectric materials.

Keywords: Bismuth-layer-structured ferroelectrics, Nd substitution, Ferroelectrics, Piezoelectrics, Curie temperature