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Synthesis experiments in the system CaO–SiO2–Al2O3–Fe2O3–MgO resulting in the formation of SFCA-III are reported. SFCA-III is a new n = 2 member of a polysomatic series of M 14+6nO20+8n compounds based on pyroxene-spinel modules which are of relevance to iron-ore sintering. Single-crystal diffraction studies using synchrotron radiation revealed that the compound occurs in two polytypes representing maximum degree of order structures which explains the observed allotwinning of the sample.

During the iron ore sintering process, two types of particles are present in the sinter bed: (1) fines, which are actively taking part in melting and the formation of secondary phases, and (2) coarse ores, which are partially interacting with the surrounding melt. The quality of the final sinter is particularly determined by the secondary phases and their bonding ability. Due to chemical differences between the fines and coarse particles, knowing the overall chemical composition of the sintering blend is not sufficient to estimate the final sinter microstructure. In this study, different ore types were used to prepare iron-rich, high-alumina, and high-silica blends, which were sintered in a laboratory sinter pot to investigate the behavior of fine as well as coarse particles. As a result, very different sinter matrices formed depending on the useful basicity in each sinter. The density, mineral nature, and the gangue of the ore affected coarse ore assimilation.

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