Properties and structural investigations of UV-transmitting vitreous strontium zinc metaphosphate

Strontium zinc metaphosphate glasses, xSrO–(50 − x)ZnO–50P2O5 with x = 0–50 mol% were prepared and studied. The substitution of SrO for ZnO increases density and glass transition temperature (Tg), and enhances the chemical durability of the glasses. The UV–vis spectra of glasses were examined. The optical band gap energies lie in the range of 3.85–4.75 eV and are found to decrease with increasing SrO content. UV transmittance of the glasses at 250 nm is above 70% as SrO content of the glass is lowered to 30 mol%. The structural changes with the glass compositions were examined by FTIR and 31P MAS-NMR spectroscopies. FTIR and 31P MAS-NMR spectra indicate that the length of phosphate chain increases with increasing SrO content in the xSrO–(50 − x)ZnO–50P2O5 glass system, thus raising Tg and enhancing chemical durability of the glasses.