Effect of Al(PO3)3, NaF, and SrF2 on structure and properties of fluorophosphate glass

•The fluorophosphate glass-forming regions were studied by changing the composition.•The optimal doping amount of Al(PO3)3 was investigated.•31P NMR showed that Al(PO3)3 would lead to the increase of homonuclear phosphate.•Al(PO3)3 and NaF were beneficial to enhance the structural stability of glass.•The thermal stability was best when alkali and alkaline earth metals was similar. The thermal stability and structural evolution of (55-x-y)Al(PO3)3-xNaF-8MgF2-10CaF2-ySrF2-17BaF2-10LiF (mol%) glasses were investigated. The thermal stability of the fluorophosphate glass system was characterized by DSC. As the content of metaphosphate increased, the thermal stability was strengthened. Besides, the thermal stability reached the strongest at alkaline metal and alkaline earth metal fluoride contents converged. On the one hand, according to Raman and FT-IR spectra, it was demonstrated that the intensity of OPO vibration in the glass structure was strengthened with the increase of Al (PO3)3 and NaF. On the other hand, 31P NMR results indicated that the POP bond was also enhancing when the Al (PO3)3 content increased. In summary, OPO and POP bonds were components of [PO4] units, and their increase signified that the structural stability of glass was enhanced. During the process of expanding the content of Al(PO3)3, deconvolution of O 1s and F 1s in XPS spectrum revealed that the increase of PO and FP bond content resulted in the structural distortion of polyhedral P[O, F]4 in glass structure and enhanced the disorder of glass.