An electron and X-ray powder diffraction study of the defect fluorite structure of Mn{sub 0.6}Ta{sub 0.4}O{sub 1.65}
- Stockholm Univ. (Sweden). Dept. of Inorganic Chemistry
The oxide Mn{sub 0.6}Ta{sub 0.4}O{sub 1.65} has been synthesized in air by rapidly cooling a melt from 1,400 C, and it has been studied by X-ray powder diffraction (XRPD), selected-area electron diffraction (SAED), high-resolution electron microscopy (HREM), thermal analysis, and measurements of magnetic susceptibility and electrical conductivity. The average structure is that of a cubic fluorite with a = 4.9826(3) {angstrom} and 18% vacancies on the O atom sites. Prominent diffuse scattering is present in its electron diffraction patterns (EDPs) and a structural model for this scattering is proposed. It is based on ca. 10 {angstrom} large microdomains with a pyrochlore type structure which are separated by antiphase boundaries. The magnetic susceptibility shows an antiferromagnetic interaction between the Mn{sup 2+} ions and an effective number of Bohr magnetons that increases with temperature. When heated in air at 500 C, the compound is oxidized to the composition Mn{sub 0.6}Ta{sub 0.4}O{sub 1.75}, while retaining a cubic fluorite structure with a = 4.8380(4) {angstrom}. This latter phase is a semiconductor with an activation energy of 0.64 eV. 36 refs., 10 figs.
- OSTI ID:
- 679217
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 145; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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