Effect of Gd on structural, dielectric and electrical transport properties of multiferroic ceramic composite BiFeO3–NaNbO3

Abstract

The multiferroics composite of (1- x)(BiFe1-yGdyO3)– xNaNbO3 (BFGNNO) with x = 0.25, 0.45 and y = 0.10, 0.20 were prepared by a high-temperature solid-state reaction technique. Structural characterization was performed by X-ray diffraction which confirms the formation of the ceramic and the materials show rhombohedral structure at room temperature. Frequency and temperature dependence of dielectric constant (εr) and dielectric loss (tanδ) of samples were measured in wide range of frequency (100 Hz to 1 MHz) and temperature (25 °C to 450 °C) using an LCR meter. The analysis of the study shows that the εr and tanδ decreases with increasing frequency in the given range for all the samples which can be explained through the occurrence of dipole relaxation process. There is enhancement of dielectric constant observed with increasing the Gadolinium (Gd) concentration. The dielectric anomalies are observed in the studied sample at about 390 °C which found to be shifting towards higher temperature side on increasing the frequency. The frequency variation of ac conductivity shows that the compound obeys Jonscher's universal power law. The variation of ac conductivity with inverse temperature found to obey the Arrhenius equation and the materials show negative temperature coefficient of resistance (NTCR) behavior.