Ca–Si–Al–O–N–F glass formation regions have been mapped on 6Ca2+–3Si4+–4Al3+ ternary diagrams at fixed O:N:F of 79:20:1 and 75:20:5 (in eq%). For both fluorine contents, glass formation regions extend toward more Ca‐rich compositions at 1650°C compared with the Ca–Si–Al–O–N system at 1700°C. Ca–Si–Al–O–N–F melting temperatures are 150°–800°C lower than equivalent Ca–Si–Al–O compositions due to fluorine incorporation into the melt. Si‐rich compositions, with both 1 and 5 eq% F, form porous glasses due to loss of SiF4.
Reaction mechanisms were studied by firing two compositions (0 or 5 eq% F) with identical cation ratios in the range of 900°–1650°C at 100°C intervals and following phase development using X‐ray diffraction. For Ca–Si–Al–O–N compositions, initial liquid formation occurs at >1200°C with complete dissolution of Si3N4 at 1300°C. For Ca–Si–Al–O–N–F compositions, reactions occur at lower temperatures with Si3N4 dissolution at 1200°C. At 20 eq% N, glasses with maximum fluorine content of ∼7 eq% were obtained. At 5 eq% F, the solubility limit for N is ∼25 eq%. At 1 eq% F, the maximum nitrogen content can be substantially increased to 40 eq% N. Incorporation of both nitrogen and fluorine in Ca–Si–Al–O glasses extends glass formation regions through combinations of lower melting temperatures (fluorine) and higher viscosities (nitrogen).