Ferrimagnetic spinels in hydrothermal and thermal treatment of MnxFe2-2x(OH)6-4x

Authors:

• W. Wolski,
• E. Wolska,
• J. Kaczmarek,
• Paweł Piszora

Abstract

Products of hydrothermal treatment of the initial amorphous system Mn_xFe_2-2x(OH)_6-4x for 0≤x≤1 in 0.1 x intervals, and products of their further thermal treatment, were examined by chemical analysis, X-ray, IR, and DTA techniques supported by magnetic measurements. After hydrothermal growth for low x, hematite and goethite phases occurred. Although the goethite phase was still identifiable at x=0.6, formation of a solid solution with the isostructural groutite was not found. The ferrimagnetic spinel phase, which resists heating up to 400°C, was present at 0.5≤x≤0.9. At higher temperatures, it transformed into the rhombohedral hematite type phase or into the cubic bixbyite phase. At T≥900°C, a ferrimagnetic spinel structure reappeared up to x=0.8. For x=0.9, the low- and high-temperature forms of the hausmannite phase occurred, for x=1 passing from one form into another through Mn₅O₈ and partritgeite. For a primary mixture Mn_0.5Fe(OH)₄, corresponding to the manganese ferrite structure, the lattice parameter of which passes from 8.43 Å through 8.33 Å to 8.50 Å, the probable crystallochemical formula was suggested. © 1997 Akadémiai Kiadó.