Compounds in the Binary System CaO-Fe2O3 and their Chemical Action on Magnesia

There are many papers published concerning the mineralizers used to drop the sintering temperature of MgO, for example, to around 1500°C.In order to carry out the studies along these lines the authors concentrated their attension to the compounds CaO⋅Fe2O3 and 2CaO⋅Fe2O3 existing in the system CaO-Fe2O3. The mixtures, x CaO+Fe2O3, where x=1, 1.25, 1.5 and 1.75, where heated and the X-ray patterns of the compounds as well as their hydrates were studied.It was confirmed that d=2.533 A belongs to CaO⋅Fe2O3, and d=2.71 and d=2.80 A to 2CaO⋅Fe2O3, MgO prepared by calcining Mg(OH)2 at 800°C for 3 hours showed the growth of periclase crystals to 0.03mm by the addition of 3% by weight of calcium ferrites. In this case X-ray analysis disclosed that Fe2O3 of calcium ferrites reacted with MgO to form MgO⋅Fe2O3, while microphotograph showed that CaO was occluded in periclase crystals.The mixtures 2CaCO3+MgO+Fe2O3, and CaCO3+MgO+Fe2O3 were heated at 1000°-1300°C for 5 hours. From the results of X-ray analysis it has been found that the compound 2CaO⋅MgO⋅Fe2O3, reported by Hansen, is the mixture of CaO⋅Fe2O3, 2CaO⋅Fe2O3, and MgO⋅Fe2O3. Also the authors consider that CaO⋅MgO⋅Fe2O3 does not exist.