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Title: Spectroscopic characterization of transition metal impurities in natural montebrasite/amblygonite.
Authors: Dias, Lorena Nunes
Pinheiro, Mauricio Veloso Brant
Moreira, Roberto Luiz
Krambrock, Klaus Wilhelm Heinrich
Guedes, Kassílio José
Menezes Filho, Luiz Alberto Dias
Karfunkel, Joachim
Schnellrath, Jurgen
Cipriano, Ricardo Augusto Scholz
Keywords: Montebrasite
Issue Date: 2010
Citation: DIAS, L. N. et al. Spectroscopic characterization of transition metal impurities in natural montebrasite/amblygonite. The American Mineralogist, v. 96, p. 42-52, 2010. Disponível em: <>. Acesso em: 20 de jun. 2017.
Abstract: Natural single-crystal specimens of the montebrasite/amblygonite series from Brazil, with general formula LiAlPO4(F,OH), were investigated by electron microprobe, Raman spectroscopy, X-ray diffraction, and infrared absorption. Since little is known about impurities and their local symmetries, electron paramagnetic resonance (EPR) was applied. Six different paramagnetic impurities and radiation defects were detected by EPR. Three of them, all substituting for Al3+ ions, namely, iron (Fe3+), vanadium (V4+), and niobium (Nb4+) impurities were characterized in this work. The Fe3+ (3d5)-related EPR spectra and angular dependencies show occupation of low-symmetry sites that are revealed in the high asymmetry parameter of the electronic fine structure, E/D = 0.27. Vanadium and niobium impurities are identified through their typical strong hyperfine interactions. Both form interesting examples for which the properties of 3d1 ion (V4+) and 4d1 ion (Nb4+) in the same host matrix can be compared. It is shown that both ions form complex defects of type VO2+ (vanadyl) and NbO2+ (niobyl), showing superhyperfine interaction with two equivalent hydrogen ions and not to fluorine. The EPR rotation patterns are analyzed in detail for three mutually perpendicular crystal planes. Spin Hamiltonian parameters are calculated and discussed.
ISSN: 1945-3027
Appears in Collections:DEGEO - Artigos publicados em periódicos

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