Raman Spectroscopy and Low Temperature Dielectric Properties of (Bi0.5Na0.5)TiO3 Ceramics

Abstract

In the present study, lead-free Bi0.5Na0.5TiO3 (BNT) ceramics were prepared by solid state reaction route and the structural, microstructural and dielectric properties have been reported. The Rietveld refinement method and Raman spectroscopy were used to analyze the structural properties of BNT ceramics. The Rietveld refinement analysis of all the sintered samples revealed the rhombohedral crystal symmetry with R3c space group. The sintered (1100 ºC) BNT ceramics exhibited homogeneous grain distribution with an average grain size of 1.40 µm. The dielectric properties of BNT ceramics were investigated over the frequency range of 1 MHz-100 MHz in the temperature range of 133K – 653K. The obtained values of dielectric constant (ϵr), dielectric loss (tanδ) and Curie temperature (TC) of the ceramics are 525, 0.067 and 603K respectively, as measured at 1 MHz. The temperature dependent AC-conductivity (σac) of the BNT ceramics was analyzed using Arrhenius law and the activation energies (EA) were estimated in different regimes. The obtained EA values are in the range of 12.37 – 23.99 meV in the temperature regime 1 ( R1: 133K – 278K), whereas in regime 2 (R2: 320K – 603K) in the range 51.5 – 126.2 meV. The frequency (1 MHz – 100 MHz) dependent σac measured at different temperatures was analyzed using Jonscher’s power law and super linear power law (SLPL). The obtained results indicate the BNT ceramics have potential applications in high frequency tunable devices.