Ternary System Al 2 O 3 ‐MgO‐CaO: I, Primary Phase Field of Crystallization of Spinel in the Subsystem MgAl 2 O 4 ‐CaAl 4 O 7 ‐CaO‐MgO

Using a novel experimental procedure in the field of ceramics/materials science that is based on the precise microanalysis (scanning electron microscopy, coupled with wavelength‐dispersive spectroscopy) of the phases that are present in equilibrated specimens, the solid‐state compatibility relations in the subsystem MgAl 2 O 4 ‐CaAl 4 O 7 ‐CaO‐MgO and the melting relationships in the subsystems MgAl 2 O 4 ‐CaAl 2 O 4 ‐MgO and MgAl 2 O 4 ‐CaAl 2 O 4 ‐CaAl 4 O 7 were established. The primary phase field of crystallization of spinel in the above‐mentioned subsystem, MgAl 2 O 4 ‐CaAl 4 O 7 ‐CaO‐MgO, was determined subsequently. The temperature, composition, and character of the ternary invariant points of the subsystem were established, and the ranges of the solid solutions in periclase, spinel, monocalcium aluminate, and dicalcium aluminate also were studied and determined, up to 1725°C.