Structural, optical and impedance spectroscopic studies of lead-free 0.2(K0.5Bi0.5TiO3)–0.8(NaNbO3) solid solution

Abstract

Polycrystalline, lead free ceramic, 0.2(K0.5Bi0.5TiO3)–0.8(NaNbO3) is prepared by high temperature mixed oxide method. Experimental studies reveal the structural and vibrational and ferroelectric properties of the ceramic. The micro structural study exhibits that small grains are distributed uniformly throughout the surface with well-defined grain boundaries and few pores. The structural analysis illustrates that the compound is formed exhibiting the structure as orthorhombic at room temperature with space group Pmc21. While adding the NaNbO3(NN) on K0.5Bi0.5TiO3 (KBT), the vibrational phonon modes undergoes a notable change, as envisaged from the FTIR spectra. From the diffuse absorbance spectra, the optical band gap is found as 3.14 eV and useful for photo catalytic application. Raman spectra exhibit different vibrational modes in the frequency ranging from 130 to 900 cm−1. Polarization study confirms the presence of ferroelectricity. Dielectric analysis infers that phase transition temperature from ferroelectric to paraelectric is observed around 500 °C. The electrical parameters related to microstructure are reflected from impedance analysis. The frequency dependent ac conductivity depends upon frequency validating Jonscher’s power law. While increasing temperature, ac conductivity increases which represents the semiconducting nature of the sample. The bulk conductivity is found to be driven by thermally activated process following Arrhenius relation.