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

✍ Scribed by V.I. Kuznetsov; V.A. Sadykov; V.A. Razdobarov; A.G. Klimenko

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 491 KB
• Volume: 104
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1177

✦ Synopsis

({ }^{57} \mathrm{Fe}) Mössbauer spectroscopy data obtained between 4.2 and (298 \mathrm{~K}), TEM, and magnetic measurements were used to study details of the real structure of cobalt oxides, (\mathrm{CoO}) and (\mathrm{Co}{3} \mathrm{O}{4}). In (\mathrm{Co}{3} \mathrm{O}{4}) samples synthesized at low temperatures the tracer is nonuniformly distributed. It exists in the form of (\alpha) (\mathrm{Fe}{2} \mathrm{O}{3}) inclusions generating stacking faults as well as in the form of (\mathrm{Fe}^{3+}) ions in octahedral positions of the spinel matrix. An excess of oxygen in (\mathrm{Co}{4} \mathrm{O}{4}) was found to generate cation vacancies in the octahedra. The 1 wo-phase (\mathrm{CoO}-\mathrm{CO}{3} \mathrm{O}{4}) system displays a dislocation network broadening the resonance lines and increasing the quadrupole splitting. For monophasic (\mathrm{CoO}) an excess of oxygen leads to the formation of microclusters of (\mathrm{CO}{3} \mathrm{O}{4}). A periodic array of shear type extended defects found in modified (\mathrm{CoO}) was proposed to be generated by ordering of (\mathrm{Fe}) impurities in some planes of the cubic structure. (3) 1993 Academic Press, Inc.