Fragmentary analysis of crystal structures of the Al,Ca-ferrite phase (Fe,Ca)4(Fe,Al)2CaFe(Al,Fe)2O14

The crystal structure of a somatic compound, Ca_7.12Fe_24.7Al_8.18O₅₆, is investigated by isolating spinel (Fe₃O₄) and pyroxene Ca(Fe, Ca)(Al, Si)₂O₆] parent structures (fragments) from the homogeneous region of the Al, Ca-ferrite (CFA) phase. Crystal chemical factors leading to formation of these fragments and conditions for their conjugation are revealed. Polytypic modifications and structural homologs of the CFA phase are considered. It is suggested that somatic (fragmentary) structures be analyzed by determining an n-dimensional periodic fragment of the parent structure, isolating a subset of fragmentary structures from modular ones, and establishing common features of parent structure fragments in derivative fragmentary structures. Admissible chemical compositions of the CFA phase are analyzed; the role of the Si impurity in stabilizing structural homologs of the CFA phase is discussed. Baikov Institute of Metallurgy, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 5, pp. 84–96, September–October, 1994. Translated by L. Smolina