Effect of Fe 3þ substitution on structural, optical and magnetic properties of barium titanate ceramics

Effect of Fe3þ substitution on structural, optical and magnetic

properties of barium titanate ceramics

N.V. Dang a

, N.T. Dung a

, P.T. Phong b,c,n

, In-Ja Lee c,nn

a Department of Physics and Technology, Thai Nguyen University of Science, Thai Nguyen City, Vietnam

b Department of Natural Sciences, Nha Trang Pedagogic College, 1- Nguyen Chanh Street, Nha Trang City, Khanh Hoa Province, Vietnam

c Department of Advanced Materials Chemistry, Dongguk University-Gyeongju, 707 Suckjang-dong, Gyeongju-Si, Gyeongbuk 780-714, South Korea

article info

Article history:

Received 18 August 2014

Received in revised form

27 September 2014

Accepted 30 September 2014

Available online 7 October 2014

Keywords:

Multiferroics

Solid state reaction

BaTiO3

Photoluminescence spectra

abstract

Multiferroic BaTi1xFexO3 (0rxr0.12) materials were synthesized using the solid-state reaction

method. The influence of Fe on the crystalline structure, the electronic structure, the optical properties

and the magnetic property of BaTi1xFexO3 samples were investigated. The obtained X-ray diffraction

patterns, Raman and UV–vis spectra showed that the structure of the material sensitively depends on Fe

dopant content, x, and transforms gradually from the tetragonal (P4mm) phase to the hexagonal

(P63/mmc) one with increasing x. The photoluminescence emission of BaTi1xFexO3 was attributed to

structural disorder. All of the samples exhibit both ferroelectricity and ferromagnetism at room

temperature. The relaxor like behavior was observed for all samples. The magnetization at a magnetic

field of 1 T abnormally depends on x, increases up to 0.1 then decreases monotonously afterward. This

anomaly in the magnetic behavior can be explained in terms of the changes in the oxidation state of ions

such as the Fe3þ-to-Fe4þ and/or Ti4þ-to-Ti3þ change induced by oxygen vacancies. The substitution of

Fe into Ti sites also causes the changes in the conductivity of the material and impurity (acceptor) levels

in the band gap, which can be evident from the absorption spectra, and time-dependent leakage current

measured at room temperature.

& 2014 Elsevier B.V. All rights reserved.

1. Introduction

BaTiO3 (BTO) has been well known for its ferroelectricity at

room temperature, high permittivity, wide band gap, and numer￾ous dielectric-based applications. It has also attracted great atten￾tion of basic research due to its different polymorphs, which exist

at various temperature ranges: rhombohedral (To 90 °C),

orthorhombic (90 °CoTo5 °C), tetragonal (0 °CoTo130 °C),

cubic (130 °CoTo1460 °C), and hexagonal (T41460 °C). Never￾theless, partial substitution of Fe, Mn or Ni with high content for

Ti, for instance, may stabilize the hexagonal polymorph at room

temperature [1–5]. Moreover, Ren [6] reported the presence of

giant electrostrain effect (about 0.75% at 200 V/mm) in Fe-doped

BaTiO3 single crystals resulting from a symmetry-conforming

property of the symmetry of point defects, in which defect dipole

moments yield internal storing forces for recovering the

reversibility of domain switching. Increasing attention has been

also paid to studying the Fe-doped BaTiO3 material because of its

interesting magneto-optical properties [7,8]. Most importantly, the

Fe-doped BaTiO3 material is currently addressed to be investigated

as a multiferroic material, in which magnetism and ferroelectricity

coexist in a structurally-single phase system at room temperature

[1,2,9], which is of importance in the development of multi￾functional materials for spintronic devices [8–12].

In this work, we prepared Fe-doped BTO bulk samples using

the conventional solid state reaction method. The crystal structure,

optical properties, magnetic property, and electronic structure of

the BaTi1xFexO3 (0rxr0.12) systems were investigated in detail

via the measurements of X-ray diffraction (XRD) pattern, vibrating

sample magnetometer (VSM), leakage current measurements, Ra￾man, UV–vis and Photoluminescence (PL) spectra. Most impor￾tantly, we report an abnormal behavior of the magnetization with

respect to the doping content of Fe ions.

2. Experimental

Ceramic BaTi1xFexO3 samples with various x values in the

range of x¼0.0–0.12 were prepared using conventional solid-state

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journal homepage: www.elsevier.com/locate/physb

Physica B

http://dx.doi.org/10.1016/j.physb.2014.09.046

0921-4526/& 2014 Elsevier B.V. All rights reserved.

n Corresponding author at: Department of Advanced Materials Chemistry, Dong￾guk University-Gyeongju, 707 Suckjang-dong, Gyeongju-Si, Gyeongbuk 780-714,

South Korea. nn Corresponding author. Fax: þ82 54 770 2220.

E-mail addresses: [email protected] (P.T. Phong),

[email protected] (I.-J. Lee).

Physica B 457 (2015) 103–107