Effect of the addition of iron oxide on the microstructure of ye'elimite.

This article is devoted to the description of the microstructure of ye'elimite, calcium aluminates and ferritic phase when iron oxide is present and when the synthesis is carried out at 1300 °C for 3 h. The incorporation of iron in ye'elimite structure (general formula: Ca 4 Al (6-2x) Fe 2x SO 16 with x = 0.00 to 1.13) is complete when x < 0.12. Beyond this composition, the ferritic phase (CaO) 2 (Al 2 O 3 ,Fe 2 O 3) appears as a minor phase which can develop two forms: needle-like morphology and melt morphology. The presence of iron favors the formation of an iron-rich liquid phase which leads to the growth of ye'elimite grains by material diffusion mechanisms and increases the conversion rate of alumina and calcium aluminates in ye'elimite phase. Also a clear distinction between calcium aluminate and ye'elimite grains is presented. • Complete and detailed description of microstructure of ye'elimite containing iron; general formula: Ca 4 Al (6-2x) Fe 2x SO 16 with x = 0.00 to 1.13 • The incorporation of iron is complete when x < 0.12. • Beyond this composition, the ferritic phase (CaO) 2 (Al 2 O 3 ,Fe 2 O 3) appears as a minor phase which can develop two forms: dendritic morphologies and melt morphology. • A clear distinction between CA and ye'elimite grains has been reported for the first time. • The presence of iron favors the formation of an iron-rich liquid phase, which leads to the formation of larger ye'elimite grains, through a liquid phase reactive sintering. [ABSTRACT FROM AUTHOR]