Thermal characterization of novel magnesium oxyhalide bismo-borate glass doped with VO2+ ions

Abstract

In the present report, physical and thermal characterizations of magnesium oxyhalide bismuth borate glasses in the composition range of $$ x{\text{Mg}}X_{2} \left( {X = {\text{F}},\,{\text{Br}}} \right) \, \cdot \, \left( {30 - x} \right){\text{MgO }}\cdot \, 50{\text{B}}_{2} {\text{O}}_{3} \cdot \, 20{\text{Bi}}_{2} {\text{O}}_{3} $$ (x = 0, 2, 5, 7 and 10) containing 2 mol% of V2O5 prepared by standard melt-quench technique have been discussed. The non-crystalline nature of prepared glasses has been identified through peak free X-ray diffraction profiles. Density (D), molar volume (V m) and oxygen packing density have been measured/calculated, and varying trends are discussed by relating with physical changes governed in prepared glass structures on increasing/changing the halogen (fluoride/bromide) ions. The differential thermal analysis (DTA) and thermogravimetry have been carried out in the temperature range of 200–900 °C. Glass transition temperature (T g) and melting temperature (T m) are determined from the DTA thermographs. The glass stability parameter, T g/T m is calculated from the obtained values of characteristic temperatures and a sudden decrease in stability at x = 5.0 is observed in both series which reflects that halide ions (F−/Br−) modify the glass structure at low concentrations (up to 5.0 mol%) and contribute to glass network formation at high concentrations (>5.0 mol%). Infrared absorption spectra have been recorded in the mid-IR range and evaluated to report the possible cause of band vibrations present in the spectra.