Exploring structural, vibrational, optical and photoluminescence characteristic of tetragonal-tungsten bronze Ba4Bi2Fe2Nb8O30 compound

In this study, we successfully synthesized the multifunctional Tetragonal-Tungsten Bronze (TTB) compound, Ba4Bi2Fe2Nb8O30 (BBFNO), using a planetary ball-milling approach. Our investigation comprehensively spanned structural, vibrational, ferroelectric, optical, and photoluminescence characteristics. Phase purity was rigorously confirmed through Rietveld-fitted X-ray powder diffraction and Fourier-transform infrared spectroscopy (FTIR), unveiling single-phase crystals within a tetragonal structure in the P4bm space group. Notably, electron density plots revealed concentrated charges on the heavier atoms. Moreover, employing the Williamson-Hall method, we established the average crystallite size as 171.53 nm. Vibrational aspects were explored through Raman spectroscopy, while a dedicated polarization study validated the presence of ferroelectric properties. UV-Vis spectroscopy allowed us to pinpoint an optical bandgap of 3.07 eV using Tauc's plot. Further analysis of photoluminescence exposed the role of oxygen vacancies in influencing energy band gap shifts towards the visible spectrum, thereby affecting electronic transitions. Importantly, the CIE (Commission Internationale de l'e'clairage) chromaticity coordinates of BBFNO fell within the bluish-violet range, suggesting potential applications in optical and display technologies. The remarkable multi-functionality of BBFNO underscores its substantial promise for diverse technological applications.