Spectroscopic studies on vitreous and polycrystalline heavy metal gallium–bismuthates

Local order changes determined by Fe2O3 (0–20 mol%) addition to Bi2O3–Ga2O3 matrix in glass and vitroceramic samples were investigated by X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) spectroscopies. Glass samples were prepared using the melt-quench technique. The vitroceramic samples were obtained by crystallization, as a result of the heat treatment applied on glass samples. The glass network mainly consists of [BiO6] octahedral units. After heat treatment induced crystallization, [BiO3] pyramidal units are predominant in samples. As evidenced by electron spin resonance, the Fe3+ ions surrounding is characterized by low crystal fields, excepting the vitreous sample with the lowest Fe2O3 content, wherein the Fe3+ ions occupy sites of low symmetry, characterized by high crystal fields.