An Electron and X-Ray Powder Diffraction Study of the Defect Fluorite Structure of Mn0.6Ta0.4O1.65

✍ Scribed by S. Esmaeilzadeh; J. Grins; A.-K. Larsson

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 952 KB
• Volume: 145
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8198

✦ Synopsis

The oxide Mn 0.6 Ta 0.4 O 1.65 has been synthesized in air by rapidly cooling a melt from 14003C, and it has been studied by X-ray powder di4raction (XRPD), selected-area electron di4raction (SAED), high-resolution electron microscopy (HREM), thermal analysis, and measurements of magnetic susceptibility and electrical conductivity. The average structure is that of a cubic 6uorite with a ‫؍‬ 4.9826(3) A > and 18% vacancies on the O atom sites. Prominent di4use scattering is present in its electron di4raction patterns (EDP:s) and a structural model for this scattering is proposed. It is based on ca. 10 A > large microdomains with a pyrochlore type structure which are separated by antiphase boundaries. The magnetic susceptibility shows an antiferromagnetic interaction between the Mn 2؉ ions and an e4ective number of Bohr magnetons that increases with temperature. When heated in air at 5003C, the compound is oxidized to the composition Mn 0.6 Ta 0.4 O 1.75 , while retaining a cubic 6uorite structure with a ‫؍‬ 4.8380(4) A > . This latter phase is a semiconductor with an activation energy of 0.64 eV.