Oxycarbide glasses in the Y-Si-Al-O-C system were successfully prepared at 1500℃ by melt solidification techniques while glasses prepared at 1600 1700℃ foamed resulting in a spongy material. For a fixed cation composition (16.5Y: 56Si: 27.5A1 in eq.) varying O:C ratios corresponding to carbon contents of 1,2, 2.5, 5 and 10 eq. were chosen to determine the solubility limit of carbon in this system. Properties such as density, microhardness, elastic modulus and glass transition temperature were measured for glasses made at 1500℃ and found to increase up to 2 eq. addition of carbon. X-ray diffraction analysis carried out on all these glasses revealed the existence of SiC peaks except for the 1 and 2 eq. carbon containing composition. 2 eq. carbon appears to be the solid solubility limit for carbon in these yttrium alumino-silicate liquids at 1500℃. The devitrification studies carried out using differential thermal analysis (DTA) and tube furnace heat treatment indicated heterogeneous nucleation mechanism with yttrium disilicate and mullite being the predominant phases formed.
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