An X-ray Rietveld, infrared, and Mössbauer spectral study of the NaMn(FeIn)(PO)alluaudite-type solid solution
- Citation data:
American Mineralogist, ISSN: 0003-004X, Vol: 88, Issue: 1, Page: 211-222
- Publication Year:
- Repository URL:
- http://scholarsmine.mst.edu/chem_facwork/878; https://works.bepress.com/gary-long/97
- Earth and Planetary Sciences; Alluaudite; Mössbauer Spectroscopy; Pegmatite; Rietveld Analysis; Solid Solution; Alluaudite; Mössbauer Spectroscopy; Pegmatite; Rietveld Analysis; Solid Solution; Chemistry
Several compounds of the NaMn(FeIn)(PO)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 Naat the A1 and A2′ sites, Mnat the M1 site, and Fe, Fe, and Inat the M2 site. The presence of small amounts of Inat the M1 site, and Mnat 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 β angle of the alluaudite-like compounds. The disordered distribution of Fe, Fe, and Inat the M2 site is confirmed by the broadness of the infrared absorption bands. The Mössbauer 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 Feat the M2 site, an amount that decreases as the Incontent increases. The Feand Feisomer 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 Mössbauer lattice temperatures are within the expected range of values for iron cations in an octahedral environment. The Feand Fequadrupole splittings are also typical of the alluaudite structure and the temperature dependence of the Fequadrupole splitting was fit with the model of Ingalls (1964), which yielded a ground state orbital splitting of ca. 380 to 570 cmfor the Fesites.