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Energetics of lanthanide-doped calcium phosphate apatite

Mahboobeh Hosseini, Seyedeh and Drouet, Christophe and Al-Kattan, Ahmed and Navrotsky, Alexandra Energetics of lanthanide-doped calcium phosphate apatite. (2014) American Mineralogist, 99 (11-12). 2320-2327. ISSN 0003-004X

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Official URL: http://dx.doi.org/10.2138/am-2014-4930

Abstract

Lanthanides “Ln” (rare earths) are critical elements found in natural minerals such as calcium phosphate apatites, in sedimentary and igneous settings as well as in skeletal diagenesis. From a medical point of view, nanoparticles of lanthanide-doped apatites can be produced for conferring luminescence properties of interest in cancer cells detection. However, the impact of the substitution of Ln for Ca on the stability and solubility of related apatite phases is still essentially unknown. To investigate the thermochemical effects of such lanthanide substitution for calcium in apatite, we prepared and analyzed four series of apatites with up to 10% lanthanide substitution for calcium. After thorough physicochemical characterization via complementary techniques (XRD, FTIR, TG/DSC, and IPC-AES), high-temperature oxide melt solution calorimetry in molten sodium molybdate at 973 K was performed to determine their enthalpies of formation from constituent oxides and from the elements, at 298 K. Our results indicate that although enthalpies of formation are strongly exothermic in all cases, Ln-doping has a destabilizing effect, which increases with dopant concentration and with the size of the incorporated Ln3+ ion. After estimating standard entropies, Gibbs free energies of formation and equilibrium constants for Ca2+/Ln3+ exchange reactions in apatite were then evaluated, for the first time allowing access to quantitative thermodynamic data that may be used in various fields for stability calculations or partitioning estimates between fluids and solids.

Item Type:Article
Additional Information:Thanks to Mineralogical Society of America editor. The definitive version is available at http://www.sciencedirect.com The original PDF of the article can be found at American mineralogist website : http://ammin.geoscienceworld.org/content/99/11-12/2320
HAL Id:hal-01194786
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Other partners > University of California - UC Davis (USA)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
Laboratory name:
Funders:
International Center of Materials Research (ICMR) - National Polytechnical Institute of Toulouse (INPT) - France- Berkeley Fund (2008 call)
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Deposited By: cirimat webmestre
Deposited On:07 Sep 2015 13:24

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