Correlation between orthorhombic distortion with relaxation and Conduction mechanism of Gd3+ modified SrBi4Ti4O15 ceramics

Abstract

Aurivillius single-phase ceramics of Gd3+ substituted SrBi4Ti4O15 with nominal formula of Sr1-xGd2×/3Bi4Ti4O15 (where x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.1) herein denoted as SGBT-x have been prepared by using mixed oxide technique. The primary structural analysis from XRD study confirms that orthorhombic distortion to increase with increase in Gd-content, which was strongly supported by Raman spectroscopy. Two of the relaxation mechanisms were clearly identified from cole-cole plot and modulus spectroscopy analysis, which could be discerned to both grain and grain boundary contributions effect. The kinetic study of frequency dependent AC conductivity at various temperature was investigated by using Jonscher's power law equation, σtot(ω)=A(T) ωs + σDC(T); where 0 < s < 1. Close resemblance of obtained activation energy from relaxation mechanism, DC conductivity as well as hopping conduction below transition temperature (TC) suggested that the transport behavior is to originate from oxygen vacancy related hopping mechanism in SGBT-0.08 specimen. In order to further confirm the possible conduction mechanisms in the system the 's' exponent has also been analyzed detail at different temperature regions. Overall we examine that CBH (correlated barrier hopping) and NSPT (non-overlapping small polaron) are two of the appropriate models for conduction process in ferroelectric and paraelectric region respectively. Also the orthorhombic distortion (b/a) of SGBT system plays a major role in the conduction and relaxation process.