title: A vibrational spectroscopic study of the phosphate mineral lulzacite Sr(2)Fe(2+)(Fe(2+),Mg)(2)Al(4)(PO(4))(4)(OH)(10).
abstract: The mineral lulzacite from Saint-Aubin des Chateaux mine, France, with theoretical formula Sr(2)Fe(2+)(Fe(2+),Mg)(2)Al(4)(PO(4))(4)(OH)(10) has been studied using a combination of electron microscopy with EDX and vibrational spectroscopic techniques. Chemical analysis shows a Sr, Fe, Al phosphate with minor amounts of Ga, Ba and Mg. Raman spectroscopy identifies an intense band at 990cm(-1) with an additional band at 1011cm(-1). These bands are attributed to the PO4(3-)ν1 symmetric stretching mode. The ν3 antisymmetric stretching modes are observed by a large number of Raman bands. The Raman bands at 1034, 1051, 1058, 1069 and 1084 together with the Raman bands at 1098, 1116, 1133, 1155 and 1174cm(-1) are assigned to the ν3 antisymmetric stretching vibrations of PO4(3-) and the HOPO3(2-) units. The observation of these multiple Raman bands in the symmetric and antisymmetric stretching region gives credence to the concept that both phosphate and hydrogen phosphate units exist in the structure of lulzacite. The series of Raman bands at 567, 582, 601, 644, 661, 673 and 687cm(-1) are assigned to the PO4(3-)ν2 bending modes. The series of Raman bands at 437, 468, 478, 491, 503cm(-1) are attributed to the PO4(3-) and HOPO3(2-)ν4 bending modes. No Raman bands of lulzacite which could be attributed to the hydroxyl stretching unit were observed. Infrared bands at 3511 and 3359cm(-1) are ascribed to the OH stretching vibration of the OH units. Very broad bands at 3022 and 3299cm(-1) are attributed to the OH stretching vibrations of water. Vibrational spectroscopy offers insights into the molecular structure of the phosphate mineral lulzacite.
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia. Electronic address: r.frost@qut.edu.au.
authors.forename: Ray L
authors.initials: RL
authors.lastname: Frost
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
authors.forename: Andrés
authors.initials: A
authors.lastname: López
authors.affiliation: Federal University of Itajubá, Campus Itabira, Itabira, MG, Brazil.
authors.forename: Fernanda M
authors.initials: FM
authors.lastname: Belotti
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Xi
authors.affiliation: Geology Department, School of Mines, Federal University of Ouro Preto, Campus Morro do Cruzeiro, Ouro Preto, MG 35400-00, Brazil.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Scholz
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D017616:Magnesium Compounds / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D013057:Spectrum Analysis; D013324:Strontium / Q000737:chemistry*
chemical_list: D017607:Aluminum Compounds; D005296:Ferrous Compounds; D017616:Magnesium Compounds; D008903:Minerals; D010710:Phosphates; C030781:magnesium phosphate; C052774:strontium phosphate; C518753:ferrous phosphate; C012714:aluminum phosphate; D013324:Strontium
keywords: Lulzacite; Phosphate; Raman spectroscopy; Strontium