Structural, Electrical, and Optical Properties of Lead-Free TB Compound: Ba₄(La_2-xBi_x)Fe₂Nb₈O₃₀ (x = 0, 0.05, 0.1, 0.15, 0.2, and 0.25)

A series of novel lead free tungsten bronze (T-B) structured Ba₄(La_2-xBi_x)Fe₂Nb₈O₃₀(x = 0, 0.05, 0.1, 0.15, 0.2, and 0.25) were formulated by traditional high temperature solid-state method and calcined at 1200 °C. The structural property was investigated by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Tetragonal structure was confirmed from Rietveld analysis. The scanning electron micrograph (SEM) shows uniform distribution of rod-shaped grains with less porosity. The UV–vis analysis shows that the materials have band gaps in the range 2.17–2.29 eV which makes them useful for photocatalytic applications. The dielectric measurement of the samples was carried out in a broad range of frequency as well as temperature. The impedance of the materials falling off with the rise in temperature showing their negative temperature coefficient (NTCR) behavior. The variation of polarization with electric field confirms the ferroelectric nature of the samples.