Compatibility Relations of A1203 in the System Zr02‐Al203‐Si02‐CaO

Compatibility relations of Al203 in the quaternary system Zr02-Al203-Si02-CaO were studied by firing and quenching followed by microscopy and energy-dispersive X-ray examination. A projection of the boundary surface of the primary crystallization volume of Al203 was constructed in terms of the CaO, Si02, and Zr02 contents of the mixtures recalculated to 100 wt%. Two invariant points, where four solids coexist with a liquid phase, are defined, and the positions of the isotherms were established.