Structural role of Zr4+ as a nucleating agent in a MgO-Al2O3-SiO2 glass-ceramics: A combined XAS and HRTEM approach | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Structural role of Zr4+ as a nucleating agent in a MgO-Al2O3-SiO2 glass-ceramics: A combined XAS and HRTEM approach

Type de publication:

Journal Article

Source:

Journal of Non-Crystalline Solids, Volume 356, Ticket 52-54, p.2928-2934 (2010)

ISBN:

0022-3093

Numéro d'accès:

ISI:000285951700006

URL:

http://www.sciencedirect.com/science/article/pii/S0022309310005740

Mots-clés:

UMR 7154 ; Minéralogie ; Nucleation; 81.05.Kf=glasses; 61.43.Fs=glass; EXAFS; HRTEM; Glass structure; Vitroceramics

Résumé:

The environment around Zr4+ is studied at the Zr K-edge in a MgO-Al2O3-SiO2 glass-ceramics heat treated along its very first crystallization steps. The heat treatments were calibrated by differential scanning calorimetry. ZrO2 acts as a nucleating agent, adding a nucleation/crystallization event around 920 degrees C, less than 100 degrees C above the glass transition temperature (830 degrees C) and below the massive crystallization of the parent-glass (similar to 1015 degrees C). It also lowers crystallization temperatures of the matrix as compared with a Zr-free sample. High-resolution transmission electron microscopy imaging allows an unambiguous attribution to tetragonal ZrO2 for, at least, some of the very first detectable crystallites. Zr K-edge extended X ray absorption fine structure analysis shows a peculiar surrounding around Zr4+ in the parent glass, composed of Si (Mg,Al) and Zr sites linked by edge sharing. This indicates direct linkages between Zr sites, pre-existing in the glass structure that play a key role for promoting nucleation. This analysis is in agreement with only a small part of Zr4+ evolving during the first steps of nucleation toward the formation of few nano-crystals of tetragonal (ZrO2). (C) 2010 Elsevier B.V. All rights reserved.

Notes:

Dargaud, Olivier Cormier, Laurent Menguy, Nicolas Galoisy, Laurence Calas, Georges Papin, Sophie Querel, Gilles Olivi, Luca 9th International Symposium on Crystallization in Glasses and Liquids SEP 10-13, 2009 Foz do Iguacu, BRAZIL Sp. Iss. SI