Ferrorosemaryite, NaFe2+Fe3+Al(PO4)3, a new phosphate mineral from the Rubindi pegmatite, Rwanda

Conference (2004)

Crystal chemistry of the Na2(Mn1-xFe2+x)2Fe3+(PO4)3 alluaudite-type solid solution

in Lithos (2004), 73(1-2), 48

Etude, par spectrométrie Mössbauer des alluaudites synthétiques Na2Mn2-xFe1+x(PO4)3, où x = 0, 0.5, 1, 1.5 et 2

Poster (2003)

An X-ray Rietveld, infrared, and Mossbauer spectral study of the NaMn(Fe1-xInx)(2)(PO4)(3) alluaudite-type solid solution

in American Mineralogist (2003), 88(1), 211-222

Several compounds of the NaMn(Fe1-xInx)(2)(PO4)(3) solid solution were synthesized by solid state reaction in air; pure alluaudite-like compounds were obtained for x = 0.00 to 1.00. X-ray Rietveld ... [more ▼]

Several compounds of the NaMn(Fe1-xInx)(2)(PO4)(3) solid solution were synthesized by solid state reaction in air; pure alluaudite-like compounds were obtained for x = 0.00 to 1.00. X-ray Rietveld refinements indicate the presence of Na+ at the A1 and A2' sites, Mn2+ at the M1 site, and Fe2+, Fe3+, and In3+ at the M2 site. The presence of small amounts of In3+ at the M I site, and Mn2+ at the M2 site, indicates a partially disordered distribution between these cations. A good correlation was also established between the M1-M2 bond distance and the beta angle of the alluaudite-like compounds. The disordered distribution of Fe2+, Fe3+, and In3+ at the M2 site is confirmed by the broadness of the infrared absorption bands. The Mossbauer spectra, measured between 90 and 295 K, were analyzed in terms of a model that takes into account the next-nearest neighbor interactions around the M2 crystallographic site. In all cases these spectra reveal the unexpected presence of small amounts of Fe2+ at the M2 site, an amount that decreases as the In3+ content increases. The Fe2+ and Fe3+ isomer shifts are typical of the alluaudite structure and vary with temperature, as expected from a second-order Doppler shift. The derived iron vibrating masses and Mossbauer lattice temperatures are within the expected range of values for iron cations in an octahedral environment. The Fe2+ and Fe3+ quadrupole splittings are also typical of the alluaudite structure and the temperature dependence of the Fe2+ quadrupole splitting was fit with the model of Ingalls (1964), which yielded a ground state orbital splitting of ca. 380 to 570 cm(-1) for the Fe2+ sites. [less ▲]

Mossbauer spectral evidence for next-nearest neighbor interactions within the alluaudite structure of Na1-xLixMnFe2(PO4)(3)

in Solid State Sciences (2002), 4(4), 507-513

The Mossbauer spectra of the Na1-xLixMnFe2(PO4)(3) compounds, with x = 0,00, 0.25, 0.50, and 0.75, have been measured between 90 and 295 K and analyzed in terms of a model which takes into account the ... [more ▼]

The Mossbauer spectra of the Na1-xLixMnFe2(PO4)(3) compounds, with x = 0,00, 0.25, 0.50, and 0.75, have been measured between 90 and 295 K and analyzed in terms of a model which takes into account the next-nearest neighbor interactions within the alluaudite structure. Surprisingly, the spectra reveal an unexpected presence of iron(II) in these compounds; the amount of iron(II) is observed to decrease from 19 to 15 atomic percent of the total iron content with increasing x. The temperature dependence of the Fe2+ and Fe3+ isomer shifts agrees with that expected from a second-order Doppler shift and the resulting iron vibrating masses and Mossbauer lattice temperatures are within the expected range of values for iron cations in an octahedral environment. The temperature dependence of the Fe2+ quadrupole splitting has been fit with the Ingalls' model and the results yield a ground state orbital splitting of ca. 500 cm(-1) for the iron(II) sites. The compositional dependence of the isomer shifts and Fe2+ content can be understood in terms of a decrease in the unit-cell volume with increasing substitution of sodium by lithium, a substitution which does not influence the observed quadrupole splittings. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved. [less ▲]

Stability of the alluaudite + triphylite paragenesis in granitic pegmatites

Poster (2002)

Mossbauer spectral evidence for next-nearest neighbor interactions within the alluaudite structure of Na1-xLixMnFe2(PO4)(3)

in Solid State Sciences (2002), 4(4), 507-513

The Mossbauer spectra of the Na1-xLixMnFe2(PO4)(3) compounds, with x = 0,00, 0.25, 0.50, and 0.75, have been measured between 90 and 295 K and analyzed in terms of a model which takes into account the ... [more ▼]

The Mossbauer spectra of the Na1-xLixMnFe2(PO4)(3) compounds, with x = 0,00, 0.25, 0.50, and 0.75, have been measured between 90 and 295 K and analyzed in terms of a model which takes into account the next-nearest neighbor interactions within the alluaudite structure. Surprisingly, the spectra reveal an unexpected presence of iron(II) in these compounds; the amount of iron(II) is observed to decrease from 19 to 15 atomic percent of the total iron content with increasing x. The temperature dependence of the Fe2+ and Fe3+ isomer shifts agrees with that expected from a second-order Doppler shift and the resulting iron vibrating masses and Mossbauer lattice temperatures are within the expected range of values for iron cations in an octahedral environment. The temperature dependence of the Fe2+ quadrupole splitting has been fit with the Ingalls' model and the results yield a ground state orbital splitting of ca. 500 cm(-1) for the iron(II) sites. The compositional dependence of the isomer shifts and Fe2+ content can be understood in terms of a decrease in the unit-cell volume with increasing substitution of sodium by lithium, a substitution which does not influence the observed quadrupole splittings. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved. [less ▲]

An Iron-57 Mössbauer Spectral Study of Na1-xLixMnFe2(PO4)3

Poster (2001)

First experimental evidence of alluaudite-like phosphates with high Li-content: the (Na1-xLix)MnFe2(PO4)3 series (x = 0 to 1).

in European Journal of Mineralogy (2000), 12

Les minéraux secondaires en relation avec les sulfures de la région de Vielsalm, Belgique

in Bulletin de la Société Royale des Sciences de Liège (1998), 67