title: Arsenate substitution in lead hydroxyl apatites: A Raman spectroscopic study.
abstract: A total of seven compounds of the hydroxylpyromorphite Pb10(PO4)6(OH)2 - hydroxylmimetite Pb10(AsO4)6(OH)2 (HPY-HMI) solid solution series were synthesized at 80°C from aqueous solutions and characterized using Raman spectroscopy. The positions of the bands in all spectra of the series depend on the content of arsenates and phosphates shifting to lower wavenumbers with substitution of (AsO4)(3-) for (PO4)(3-). This shift results from the decreasing bond strength of X-O (where X=P, As) and higher atomic mass of As than P. The position and intensity of major (PO4)(3-) and (AsO4)(3-) bands in Raman spectra exhibit linear correlation with As content, while the ratio of the intensities of these peaks shows exponential correlation. This results due to different polarizability of (PO4)(3-) and (AsO4)(3-) molecules. A small carbonate band develops with increasing As content indicating that hydroxyl lead apatites adopt the (CO3)(2-) ions, particularly at the arsenate end of the series.
authors.affiliation: Institute of Geological Sciences, Polish Academy of Sciences INGPAN, ul. Senacka 1, 31-002 Kraków, Poland.
authors.forename: Alicja
authors.initials: A
authors.lastname: Giera
authors.affiliation: Department of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland. Electronic address: gpmmanec@cyf-kr.edu.pl.
authors.forename: Maciej
authors.initials: M
authors.lastname: Manecki
authors.affiliation: Department of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Bajda
authors.affiliation: Department of Geology and Environmental Earth Science, Miami University, 114 Shideler Hall, Oxford, OH 45056, USA.
authors.forename: John
authors.initials: J
authors.lastname: Rakovan
authors.affiliation: Department of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.
authors.forename: Monika
authors.initials: M
authors.lastname: Kwaśniak-Kominek
authors.affiliation: Department of Geology and Environmental Earth Science, Miami University, 114 Shideler Hall, Oxford, OH 45056, USA.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Marchlewski
keywords: Carbonate in apatites; Lead apatite; Mimetite; Pyromorphite; Raman band shift; Solid solution