Effect of synthesis conditions, Zn doping and Al/Fe ratio on calcium [alumino] ferrite structure

The use of steel waste for clinker production is a promising solution to reduce the environmental impact of Portland cement. While it is known that clinker produced from steel slag shows some advantageous properties e.g., lower burning temperature and reduced use of limestone, it is necessary to understand the formation and stability of iron-rich clinkers doped with the minor elements commonly found in steel wastes. In this study, pure ferrite phases were synthesized with varying Al/Fe ratios, burning temperature, cooling regimes, and in the presence of Zn as a minor element at various dosages. The phase assemblage and microstructure of the obtained ferrites were characterised by XRD/Rietveld and BSE-SEM/EDX. The results show that Zn is partially incorporated into the ferrite structure and partially replaces Al to form a Ca-Al-Zn phase. The Zn-incorporated ferrite leads to increased lattice parameter due to the bigger ionic radius of the dopant with respect to the substituted ions, and to increased crystallinity due to the increased ion mobility brought by ZnO which acts like a flux.