Optical, structural and thermal properties of sodium metaphosphate glasses containing Bi₂O₃ with interactions of...

Sodium metaphosphate glasses with successive increasing added Bi₂O₃ contents (5-40%) were prepared to improve their chemical stability and increase their optical and thermal properties through the additional building BiO₆ and BiO₃ units. The optical spectrum of the base metaphosphate glass reveals strong UV absorption due to the presence of trace iron (Fe³⁺) ions present as impurities. Glasses containing additional 5, 7.5 and 10% Bi₂O₃ show further band around 406nm which can be related to absorption of Bi³⁺ ions. With increasing the Bi₂O₃ content, this near visible band is observed to disappear indicating peculiar behavior needing further work. Gamma irradiation causes only minor changes in the position of the strong UV peaks but an obvious induced visible broad band centered at 452-460nm in the base and Bi₂O₃ containing glasses. This induced band is related to the generation of phosphorus oxygen hole center or non bridging oxygen hole center as revealed by various authors. FTIR results reveal characteristic vibrational bands due to phosphate groups and with the addition of Bi₂O₃, some interference of BiO vibrational units are expected. Gamma irradiation causes limited changes in the IR spectra due to suggested shielding effect of the heavy metal oxide Bi₂O₃.