Mössbauer Study of β‐ and δ‐FeOOH and their Disintegration Products

Abstract

β‐FeOOH and δ‐FeOOH are studied by Mössbauer effect measurements. The Néel point of β‐FeOOH is TN = (295 ± 4) °K. Above this temperature the material is paramagnetic with quadrupole splitting and it decomposes to α‐Fe2O3 at 670 °K. The transition at this temperature takes 12 hours. The two internal magnetic fields observed in δ‐FeOOH are found to correspond to Fe3+ ions in octahedral and tetrahedral positions. δ‐FeOOH decomposes to intermediate products at 370 °K below its Curie Temperature and it disintegrates to α‐Fe2O3 at approximately 510 °K.

The secondary iron oxidehydroxide mineralogy of some deep-sea and fossil manganese nodules: A Moessbauer and X-ray study.

“…These values are, however, close to those quoted by previous workers i.e. A = 0.072 ± 0.007mm.s-', S = 0.015 ± 0.007mm.s-' (DEzsI et al , 1967); A = 0.72 ±0.010, S = 0.16±0.04 (HERZENBERG and Toms, 1966); A = 0.70, 6 = 0.14 (HowE and GALLAGHER, 1975), and also to the 2 peak fits for all the nodules except that for the Timor sample (Table 3).…”

Depth-resolved Conversion Electron Mössbauer Study of Solid Surfaces at Low Temperatures with an Electron Spectrometer

“…In View of the experimental conditions for oxidizing the iron foil and the difference between the spectra at 293 K and at 195 K, it is likely that the paramagnetic Fe3+ formed on the top surface of the layered sample mainly consisted of |3-FeOOH. It is known that the Mössbauer Spectrum of l3-FeOOH shows a paramagnetic doublet not only above but also below its Neel temperature (295 K) due to the paramagnetic relaxation effect, and the relative peak area of its antiferromagnetic sextet is more enhanced at lower temperatures [22]. Accordingly, the temperaturedependent behavior of the paramagnetic Fe^"^ formed in the top surface of the layered sample in conversion electron Mössbauer spectra was consistent with the reported behavior of/J-FeOOH.…”

Mössbauer Study of Transformations Induced in Clay by Firing

“…The two magnetic components are identified as small particles of ~-Fe20 3 and /3-FeOOH through their hyperfine parameters listed in Table 1 by comparison with previously reported values for these oxides. The value of the effective magnetic field for /3-FeOOH reported by Dezsi et al (1967) was measured at 77~ These authors report also a value of 300~ for the Neel temperature of this oxide which is the temperature at which antiferromagnetic order occurs. Using this value, the effective magnetic field at 4"2~ may be estimated at 490 kG in good agreement with .the effective magnetic field of the second magnetic component $2.…”

“…To substantiate this assignment, values of hyperfine parameters for small particles of these oxides calculated from data by Ktindig et at. (1966), Voznyuk and Dubinin (1973) and Dezsi et al (1967) are included in Table 1. This will be discussed in detail later.…”