Subsoliclus phase equilibria in the system CaO-Al2O3-CoO and the crystal structure of novel Ca3CoAl4O10

The subsolidus phase diagram, CaO-Al2O3-CoO, and its phase relations below 1300degreesC have been studied in air. The stability regions of nine subsolidus compatibility triangles were established and a new ternary phase was found. The structure of this compound, Ca3CoAl4O10 (orthorhombic, space group Pbc2(1), a = 5.1452(2) Angstrom, b = 16.7731(5) A, c = 10.7055(3) Angstrom), was determined from X-ray diffraction data and found to be isostructural with Ca3ZnAl4O10. This is an open framework compound with three crystallographically different channels, each wit a diameter of similar to3.5 Angstrom. The two end members of the binary CoO-CaO system are surrounded by small regions of solid solutions. Lab color parameters were measured in several compositions. No ternary phases were found when Co was substituted by other divalent cations such as Sr, Ba, Mn, Ni, Cu, Cd, Sn and Pb. (C) 2002 Elsevier Science (USA).