ZrO2 addition in soda-lime aluminoborosilicate glasses containing rare earths: Impact on rare earths environment and crystallization

Abstract : The effect of adding increasing ZrO 2 content on the environment of Nd 3þ ions in a glass belonging to the SiO 2-B 2 O 3-Al 2 O 3-Na 2 O-CaO system was investigated both by optical absorption spectroscopy and Nd-EXAFS (L III-edge). In agreement with the evolution of the structure of the glassy network and more particularly of the distribution of Na þ and Ca 2þ ions with ZrO 2 addition put in evidence in a previous study, it is shown here that the average NdeO distance continuously increases whereas the bond covalency decreases with zirconium content. This result can be explained both by the decrease of the amount of non-bridging oxygen atoms (NBOs) and by the increase of the proportion of Ca 2þ ions acting as charge compensators in the neighborhood of neodymium polyhedra in the depolymerized regions of the glass structure. This evolution is due to a competition in favor of zirconium between Zr and Nd for Na þ cations charge compensators. The local structural evolution around neodymium is probably responsible for the evolution of the crystallization tendency-increase of Nd-rich apatite (Ca 2 N-d 8 (SiO 4) 6 O 2) crystallization in the bulk-observed in this work both during melt cooling and glass heating by increasing ZrO 2 content. It is proposed that the nucleating effect of ZrO 2 on apatite crystallization put in evidence here is mainly due to the changes that are indirectly induced by zirconium in the neighborhood of Nd 3þ ions (destabilization) rather than to the formation of Zr-rich crystals that would then act as nucleating phase for apatite.
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https://hal-cea.archives-ouvertes.fr/cea-01528328
Contributeur : Serge Palacin <>
Soumis le : lundi 29 mai 2017 - 07:51:54
Dernière modification le : jeudi 15 mars 2018 - 15:06:15

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Arnaud Quintas, Daniel Caurant, Odile Majérus, Pascal Loiseau, Thibault Charpentier, et al.. ZrO2 addition in soda-lime aluminoborosilicate glasses containing rare earths: Impact on rare earths environment and crystallization. Journal of Alloys and Compounds, Elsevier, 2017, 719, pp.383-391. 〈http://www.sciencedirect.com/science/article/pii/S0925838817318285〉. 〈10.1016/j.jallcom.2017.05.211〉. 〈cea-01528328〉

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