Structural, electrical, magnetic and narrow band gap-correlated optical characteristics of multiferroic [Pb(Fe0.5Nb0.5)O3]0.5−[(Ba0.8Sr0.2)TiO3]0.5

The research article reports the various functional properties of barium strontium titanate [(Ba0.8Sr0.2)TiO3]-modified lead iron niobate [Pb(Fe0.5Nb0.5)O3] ceramic oxide synthesized by the solid-state method. Rietveld and POWD studies proved that the composition crystallizes in tetragonal structure as the primary phase. Ti–O perovskite vibrations were studied by Fourier transform infrared (FTIR) analysis. The TiO6 octahedral stretching, O–Ti–O vibrations and Nb–O–Fe stretching vibrations of PFN were studied by Raman spectroscopy. The broadening of Raman modes was analysed in the framework of Heisenberg’s uncertainty principle using phonon confinement model. Field emission gun-scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS) studies revealed the dense grain distributions, grain growth and purity. UV–visible analysis was done to study the narrow band gap and Urbach energy. The effect of structural distortions and electronegativity on band gap were analysed. The photocatalytic response was studied by estimating the band edge levels using Mulliken’s model. The evaluated conduction band minimum level is sufficiently negative with respect to the H+/H2 (0 eV) level, which strongly signifies the possible occurrence of the photocatalytic hydrogen emission reaction. A detailed electrical analysis was done to study the dielectric properties, relaxation, negative temperature coefficient of resistance (NTCR)-type response and DC conductivity. AC conductivity studies revealed the presence of overlapping large polaron tunnelling (OLPT) model. The effect of oxygen vacancies on relaxation and its correlation with activation energy were discussed. Multiferroic nature was confirmed from room temperature studies of P–E and M–H hysteresis loops. Fe3+ ↔ Fe3+ (F centre) exchange and Fe3+ ↔ Fe2+ double exchange mechanisms were discussed. A magnetic improvement was noticed on reduction of temperature to 50 K. The simultaneous existence of weak ferroelectricity and ferromagnetism is one of the interesting outcomes of the present study, which may provide a new multiferroic material for advanced electro-optical applications.