Structural, Dielectric And Conductivity Properties Of Ba2+ doped (Bi0.5Na0.5)TiO3 ceramic 

Smart Materials Research Laboratory, Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667, India

Adv. Mater. Lett., 2012, Current Issue, 3 (4), pp 286-292

DOI: 10.5185/amlett.2012.2322

Publication Date (Web): Jul 22, 2012

Copyright © IAAM-VBRI Press

E-mail: klyadav35@yahoo.com

Abstract

Polycrystalline (Bi_0.5Na_0.5)_1-xBa_xTiO₃ [here after BNBT], x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1 ceramics have been synthesized by conventional solid state reaction process and were characterized by X-ray diffraction technique, which indicates that on substitution of Ba²⁺ in Bi_0.5Na_0.5TiO₃ (BNT) ceramic there is splitting of the (2 0 0) peak for x ≥ 0.06. This splitting in the peak position reveals that the composition BNBT-0.06 is well in Morphotropic Phase Boundary (MPB) region where rhombohedral and tetragonal phase co-exist. Scanning electron micrograph shows decrease in grain size from 0.66 to 0.53 μm with increasing concentration of Ba²⁺; and the dielectric constant of Ba²⁺ doped BNT ceramics increased with decreasing grain sizes and a maximum value was attained at size of 0.54 ~ 0.56 μm. Doped BNT ceramic also exhibit diffuse phase transition and are characterised by a strong temperature and frequency dispersion of the permittivity which would be connected with the cation disorder in A-site of perovskite unit cell. Complex impedance spectroscopy is used to analyze the electrical behaviour of BNBT, which indicates the presence of grain effect and the composition exhibits Negative Temperature coefficient of resistance (NTCR) behaviour. The compounds exhibit Arrhenius type of electrical conductivity and the presence of non-Debye type of relaxation has been confirmed from impedance analysis.

Keywords

Ceramics, X-ray diffraction, grain size, complex impedance spectroscopy, NTCR behavior.