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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Effect of Bromine on NaF Crystallization in Photo-Thermo-Refractive Glass

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Autor(es):
Souza, G. P. [1] ; Fokin, V. M. [2] ; Baptista, C. A. [1] ; Zanotto, E. D. [1] ; Lumeau, J. [3] ; Glebova, L. [3] ; Glebov, L. B. [3]
Número total de Autores: 7
Afiliação do(s) autor(es):
[1] Univ Fed Sao Carlos, Dept Mat Engn DEMa, Vitreous Mat Lab LaMaV, BR-13565905 Sao Carlos, SP - Brazil
[2] Vavilov State Opt Inst, St Petersburg 193171 - Russia
[3] Univ Cent Florida, Coll Opt & Photon, CREOL, Orlando, FL 32816 - USA
Número total de Afiliações: 3
Tipo de documento: Artigo Científico
Fonte: Journal of the American Ceramic Society; v. 94, n. 9, p. 2906-2911, SEP 2011.
Citações Web of Science: 9
Resumo

Photo-thermo-refractive (PTR) glass is a Na(2)O-K(2)O-ZnO-Al(2)O(3)-SiO(2) silicate optical glass which also contains fluorine, a small amount of bromine, and dopants that yield photo-sensitivity in the UV range. PTR glass undergoes crystallization of NaF nanocrystals after UV-exposure followed by thermal treatment, resulting in permanent refractive index change. In this study, where we explore only the thermally activated transformations in the UV-unexposed glass, we show that bromine decreases the solubility of NaF, i.e., increases the super-saturation of NaF thus increasing the thermodynamic driving force for crystallization. This feature causes a decrease in the maximum volume fraction of crystallized NaF with decreasing bromine content in the parent glass. The evolution of the glass transition temperature, T(g), with increasing isothermal treatment time revealed a minimum resulted from interplay between two concurring processes, liquid-liquid phase separation that led to decrease in T(g), and Br-controlled NaF crystallization that acted in the opposite direction. In glasses with lower bromine content, fewer and larger crystals appeared and a surface-initiated crystallization was dominant. A surface layer of F-depleted glass imprinted residual macro-stresses, which were not alleviated by annealing. (AU)

Processo FAPESP: 08/00475-0 - Vladimir Mikhailovich Fokin | S.I. Vavilov State Optical Institute - Rússia
Beneficiário:Edgar Dutra Zanotto
Linha de fomento: Auxílio à Pesquisa - Pesquisador Visitante - Internacional
Processo FAPESP: 07/08179-9 - Processos cinéticos em vidros e vitrocerâmicas
Beneficiário:Edgar Dutra Zanotto
Linha de fomento: Auxílio à Pesquisa - Temático
Processo FAPESP: 08/02645-0 - Comportamento térmico e evolução microestrutural de vidro foto-termo-refrativo durante cristalização
Beneficiário:Guilherme Parente Souza
Linha de fomento: Bolsas no Brasil - Pós-Doutorado