Novel Glass Formation in the Ca-Si-Al-O-N-F System

Reaction mechanisms were studied by firing two compositions (0 or 5 eq% F) with identical cation ratios in the range of 900 degrees-1650 degrees C at 100 degrees C intervals and following phase development using X-ray diffraction. For Ca-Si-Al-O-N compositions, initial liquid formation occurs at > 1200 degrees C with complete dissolution of Si3N4 at 1300 degrees C. For Ca-Si-Al-O-N-F compositions, reactions occur at lower temperatures with Si3N4 dissolution at 1200 degrees C. At 20 eq% N, glasses with maximum fluorine content of similar to 7 eq% were obtained. At 5 eq% F, the solubility limit for N is similar to 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).