XAFS characterization of the structural site of Yb in synthetic pyrope and grossular garnets |
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Authors: | S Quartieri G Antonioli C A Geiger G Artioli P P Lottici |
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Institution: | (1) Dipartimento di Scienze della Terra, Via S. Eufemia 19, I-41100 Modena, Italy E-mail: quartieri@unimo.it Phone: +39-59-417239 Fax: +39-59-417399, IT;(2) INFM and Dipartimento di Fisica, Viale delle Scienze, I-43100 Parma, Italy, IT;(3) Mineralogisch-Petrographisches Institut, Olshausenstr 40, D-24098 Kiel, Germany, DE;(4) Dipartimento di Scienze della Terra, Via Botticelli 23, I-20133 Milano, Italy, IT |
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Abstract: | The incorporation and site preference of minor amounts (about 1 wt%) of Yb3+ in synthetic pyrope (Mg3Al2Si3O12) and grossular (Ca3Al2Si3O12) garnet were studied by X-ray Absorption Fine-Structure (XAFS) Spectroscopy. The measurements, performed in the temperature
range 77–343 K at both Yb LI- and LIII-edges, demonstrate that Yb3+ enters the garnet structure and is located in the dodecahedral site in both samples. The coordination environment of Yb3+ in the two samples was compared to that of the X-site cation in end-member synthetic pyrope and grossular and in Yb3Al5O12 as determined by single-crystal X-ray diffraction. The local geometry around Yb3+ is different from that of Mg and Ca in the bulk of the garnet, and also from that of Yb3+ in Yb3Al5O12.
Τhe XAFS results indicate that, (1) structural relaxation occurs around Yb3+ in the garnet structure; (2) the host garnet matrix exerts a major structural control on the incorporation of Yb3+, and (3) minor amounts of Yb3+ in garnet are located in structural sites and not in ill-defined defects.
Received: 15 January 1998/ Revised, accepted: 21 July 1998 |
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Keywords: | XAFS Ytterbium Garnet Pyrope Grossular |
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