Site preference of rare earth elements in fluorapatite

Abstract

Other| April 01, 1995 Site preference of rare earth elements in fluorapatite Michael E. Fleet; Michael E. Fleet University of Western Ontario, Department of Earth Sciences, London, ON, Canada Search for other works by this author on: GSW Google Scholar Yuanming Pan Yuanming Pan University of Saskatchewan, Canada Search for other works by this author on: GSW Google Scholar American Mineralogist (1995) 80 (3-4): 329–335. https://doi.org/10.2138/am-1995-3-414 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Michael E. Fleet, Yuanming Pan; Site preference of rare earth elements in fluorapatite. American Mineralogist 1995;; 80 (3-4): 329–335. doi: https://doi.org/10.2138/am-1995-3-414 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Crystals of La-, Gd-, and Dy-bearing fluorapatite [La-FAp, Gd-FAp, Dy-FAp; Ca10–x–2yNayREEx+y (P1–xSixO4)6A2, with x = 0.24–0.29, y = 0.32–0.36; P63/m] have been synthesized hydrothermally, and their structures refined at room temperature with single-crystal X-ray intensities to R = 0.015–0.018. Na is essentially restricted to the Ca1 position in La-FAp, Gd-FAp, and Dy-FAp, in contrast to Nd-FAp, which was synthesized under slightly different conditions and has appreciable Na in Ca2 as well. Site occupancies for REE in Cal and Ca2, respectively, are 0.023(1) and 0.093(1) in LaFAp, 0.038(1) and 0.111(1) in Nd-FAp, 0.038(0) and 0.077(0) in Gd-FAp, and 0.039(1) and 0.060(1) in Dy-FAp. The REE site occupancy ratio (REE-Ca2 to REE-Ca1) appears to decrease mono-tonically for REE3+ cations through the 4f transition-metal series. With this assumption, site occupancy ratios (REE-Ca2 to REE-Ca1) for some other REE in natural apatite are estimated to be: La 4.04, Ce 3.67, Pr 3.30, Nd 2.92, Sm 2.47, Eu 2.25, Gd 2.03, Dy 1.54, Y 1.29, Er 1.05. These single-REE site occupancy ratios may not be transferrable to natural apatite.The Ca1 and Ca2 site occupancies are generally consistent with site preferences deduced from bond-valence calculations, which show that the substitutions for Ca lead to equalization of Ca1 and Ca2 bond valences. Also, the REE site occupancy ratio correlates inversely with F bond valence. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.