Relationship on UV transmission and structure of lithium aluminum silicate-phosphate glasses

Ultraviolet (UV) transparency and local structural environment of alumina-silicate-phosphate glasses in the Li-Al-Si-P system are studied by changing lithium content at expense of P₂O₅, by UV-vis Recording Spectrophotometer (UVPC), Fourier transform infrared spectroscopy (FT-IR) in company with ²⁹Si, ²⁷Al and ³¹P magic angle spinning (MAS) nuclear magnetic resonance (NMR). The structure of glasses is changed with the substitution of Li₂O for P₂O₅. According to ²⁹Si and ³¹P MAS-NMR spectra, silicate and phosphate are all located to the high coordination states, but aluminate appears three coordinate circumstances (four-, five- and six-coordinated). The average of Al coordination numbers decrease with using Li₂O to replace P₂O₅, which indicates that the Al as the modifier becomes the network-former. Meanwhile, the result of FTIR indicates that the bonds of Si-O-Al and P-O-Al are gradually increased. Hence, the bonds formed by Al-O-T(T=Si, P) become the bridging oxygen, improving the UV transmittance simultaneously.