Effect of doping of Nd3+ ions in BaO–TeO2–B2O3 glasses: A vibrational and optical study

• Transformation of BO4 to BO3 structural units with the increase in Nd2O3 concentration.
• Optical energy band gap decreases with the increase in Nd2O3 content.
• The optical absorption show good agreement with the hydrogenic excitonic model.

Nd3+ ions doped Barium–Tellurite–Borate glasses with compositions xNd2O3 − (100 − x)[0.1BaO–0.4TeO2–0.5B2O3]; x = 0.0, 0.5, 1.0, 1.5 and 2.0 have been prepared by melt-quench technique. The amorphous nature of as-prepared glasses has been confirmed by X-ray diffraction patterns. The density, molar volume and equivalent crystalline volume of the glass samples have been found to increase with the increase in concentration of Nd2O3. FTIR and Raman spectra of the prepared glasses indicate that Nd2O3 acts as glass modifier and as the content of Nd2O3 increases, BO4 structural units are converted into BO3 structural units. The values of optical band gap have been estimated from the fitting of Mott and Davis’s model with the experimentally observed absorption spectra. The experimentally observed spectra of absorption coefficient also show good agreement with the hydrogenic excitonic model and the values of different parameters like optical band gap, excitonic binding energy, line width of m = 1 state and line width of continuum have been estimated from theoretical fitting of this model. The values of optical band gap are observed to decrease with increase in concentration of Nd2O3.