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Formation of ε-Co nanocrystals in borosilicate and aluminosilicate glasses

: Briese, L.C.; Selle, S.; Deubener, J.; Höche, T.


Journal of non-crystalline solids 535 (2020), Art. 119961
ISSN: 0022-3093
Journal Article
Fraunhofer IMWS ()

Formation of cobalt nanocrystals in durable borosilicate and aluminosilicate glass matrices is studied. Using a hydrogen gas flow treatment, ε-Co nanocrystals precipitate primarily in these glasses. This rare Co allotrope, which so far has mainly been synthetized by organometallic routes is found for the first time in a glass. XRD and TEM results indicate that ε-Co is present in glasses ≥ 500 °C and that it successively transforms into the more stable α- and β-Co allotropes. Primary formation of the ε-Co in glasses is in agreement with the Ostwald-Volmer rule of stage as it yields the lowest density change with respect to the parent glass among the three Co allotropes.