The Structural Features of Cobalt Oxides: <SUP>57</SUP>Fe Mössbauer Spectroscopy, TEM, and Static Magnetic Susceptibility Measurements

⁵⁷Fe Mössbauer spectroscopy data obtained between 4.2 and 298 K, TEM, and magnetic measurements were used to study details of the real structure of cobalt oxides, CoO and Co₃O₄. In Co₃O₄ samples synthesized at low temperatures the tracer is nonuniformly distributed. It exists in the form of α-Fe₂O₃ inclusions generating stacking faults as well as in the form of Fe³⁺ ions in octahedral positions of the spinel matrix. An excess of oxygen in Co₃O₄ was found to generate cation vacancies in the octahedra. The two-phase CoO-Co₃O₄ system displays a dislocation network broadening the resonance lines and increasing the quadrupole splitting. For monophasic CoO an excess of oxygen leads to the formation of microclusters of Co₃O₄. A periodic array of shear type extended defects found in modified CoO was proposed to be generated by ordering of Fe impurities in some planes of the cubic structure. Copyright 1993, 1999 Academic Press