Effects of Nd3+ Doping and Heat Treatment on Bismuth Niobium Tellurite Transparent Glass-ceramics

Tellurite glass and anti-glass samples of two systems: 12.5Bi₂O₃–12.5Nb₂O₅–(75-x)TeO₂–xNd₂O₃ and 7.5Bi₂O₃–7.5Nb₂O₅–(85-x)TeO₂–xNd₂O₃; x = 0 and 1 mol% are prepared by melt–quenching. Transparent glass-ceramics (TGCs) containing anti-glass inclusions co-existing with the glass are prepared by heat–treatment 26 °C above their respective glass transition temperatures. Heating at a higher temperature of 510 °C formed opaque crystalline samples. The effects of Nd³⁺ doping and heat treatment on the samples are studied by X–ray diffraction (XRD), density measurements, Differential scanning calorimetry (DSC), micro-Raman, and UV–visible spectroscopy. The growth of inclusions of anti-glass phases in the TGCs is confirmed by optical microscopy. XRD studies showed sharp peaks of orthorhombic BiNbTe₂O₈ and TeO₂ phases in TGC samples. DSC studies found that the addition of Nd³⁺ enhances the glass transition temperature. Micro-Raman studies found very similar spectra in both anti-glass inclusions and glass matrix confirming that the anti-glass inclusions have vibrational disorder. The size of inclusions is found to be higher in Nd³⁺ doped sample containing lower concentration of Bi₂O₃ and Nb₂O₅ (7.5 mol%). The Nd³⁺ doped samples exhibit broad near-infrared emission bands on excitation with 785 nm laser light.