Phase Equilibrium Studies in the System Iron Oxide‐Al 2 O 3 ‐Cr 2 O 3

Subsolidus phase relations in the system iron oride‐Al 2 O 2 ‐Cr 2 O 3 in air and at 1 atm. O 2 pressure have been studied in the. temperature interval 1250° to 1500°C. At temperatures below 1318° C. only sesquioxides with hexagonal corundum structure are present as equilibrium phases. In the temperature interval 1318° to 1410°C. in air and 1318° to 1495° C. at 1 atm. O 2 , pressure the monoclinic phase Fe 2 O 3 . Al 2 O 3 with some Cr 2 O 3 in solid solution is present in the phase assemblage of certain mixtures. At temperatures above 1380°C. in air and above 1445°C. at 1 atm. O 2 pressure a complex spinel solid solution is one of the phases present in appropriate composition areas of the system. X‐ray data relating d‐ spacing to composition of solid solution phases are given.