STATE ANALYSIS AND RELATIONSHIP BETWEEN LATTICE-CONSTANTS AND COMPOSITIONS INCLUDING MINOR ELEMENTS OF SYNTHETIC MAGNETITE AND MAGHEMITE

Chemical formulae were constructed after the determination of the comp ositions including the minor elements in commercially available synthe tic magnetite and maghemite, which gave similar x-ray diffraction patt erns with close diffraction lines. The contents of FeO in reagent grad e magnetite and high-purity magnetite powders were about 8 mol% less a nd that in a needle-shaped magnetite powder was about 24 mol% less tha n the 50 mol% in the expected composition (FeO . Fe2O3) of magnetite. They were solid solutions of magnetite-maghemite (gamma-Fe2O3) includi ng minor elements in the lattice. A linear relationship was found betw een the total mole percentage of divalent iron, manganese and zinc oxi des and their lattice constants a(c) corrected by increments of the la ttice constant based on the replacement of divalent iron with manganes e and zinc atoms. The possibility of a non-destructive total analysis of the same iron oxide samples by an x-ray method is discussed. It was found that magnetite was considerably oxidized in air even at 110-deg rees-C to form a solid solution, but not to form any separated compoun d.