Bertoluzza, Fagnano, Monti: Spettri Raman di materiali vetrosi del sistema Li2O-B2O3

Bertoluzza, Alessandro and Fagnano, Concezio and Monti, Patrizia:
Spettri Raman di materiali vetrosi del sistema Li₂O-B₂O₃
Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Serie 8 55 (1973), fasc. n.5, p. 506-514, (Italian)
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Raman spectra of materials of binary molar composition B₂O₃/Li₂O variable between 9 and 1 in the glassy system B₂O₃-Li₂O are discussed relatively to the "boric anomaly" phenomenon presented by these glasses and relatively to the measures of diamagnetic anisotropy and nuclear magnetic resonance made by other Authors. In analogy to these latest measures the presence of structural centers consisting of boroxol groups B₃O₃(O)₃ is made evident in the glasses richest in B₂O₃ up to the composition 3B₂O₃-Li₂O. Moreover it is possible to reveal the diminution of boroxol groups number in this interval of compositions when the Li₂O percentage rises. The presence of these centers is deduced from Raman spectra, particularly from the typical band at 808 cm^-1. The addition of Li₂O to B₂O₃ up to the glass of composition B₂O₃/Li₂O = 3 allows the gradual boron transformation from a trigonal to a tetrahedral coordination, according to the measures of diamagnetic anisotropy and nuclear magnetic resonance. Only by successive addition of Li₂O, is a demolition of the $\sigma$-bonds structure in the glassy material and the reformation of boron trigonal centers also possible. The probable mechanism of this reformation is assigned. Particularly, the Raman spectrum of the glass of composition B₂O₃/Li₂O = 1 agrees with that of melted $LiKO \cdot B_{2}O_{3}$ made by other Authors and is analogously interpretable on the basis of the presence, in the material, of boron trigonal atoms.

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Referenze Bibliografiche