Preparation and NMR Analysis of BAP System Glasses Doped with Rare Earths

The glass-forming region of BaO-Al₂O₃-P₂O₅(BAP) glass doped with high Sm₂O₅ content was studied by two-step melt method. With increasing Sm₂O₃ of content, the forming range of BAPS glasses would shrink and tend to close ellipse, above 20% of Sm₂O₃ content in either case resulted in the partial devitrification of glass. The ³¹P and ²⁷Al MAS NMR spectra were measured and analyzed for BAP glasses that contain distinct compositions, different heat history and Sm₂O₃ content. The NMR spectra results showed that Q² type [PO₄] tetrahedron was the dominant P sites, and the aluminum ions present in BAP glasses were [AlO₄] and [AlO₆]. The influence was not significant from glasses composition, heat history and the Sm₂O₃ content on the phosphorus structural units, contrarily, increase of the P/Al ratio led to the conversion of [AlO₆] to [AlO₄] units. As well as heat treatment and increase of Sm₂O₃ content resulted in the conversion of [AlO₆] to [AlO₄] units.