Ceramics-Silikáty 30, (2) 97 - 102 (1986)

Calculation was carried out of a part of the phase diagram of the system CaO-Al₂O₃-SiO₂ in the region of primary crystallization of wollastonite, anorthite, gehlenite and dicalcium silicate (xCaO/xAl₂O₃ ≥ 1). A satisfactory agreement with the experimentally determined phase diagram was obtained on the assumption that only one half of the Al^III atoms present is tetrahedrally coordinated and the remaining half shows a higher coordination, behaves as a modifier of the tetrahedral network, and thus does not contribute to the cross-linking of the polyanions. The behaviour of Al^III atoms in silicate melts is similar to that of Fe^III atoms.