Spettri Raman di materiali vetrosi del sistema Li2O-B2O3

Bertoluzza, Alessandro ; Fagnano, Concezio ; Monti, Patrizia

Atti della Accademia nazionale dei Lincei. Rendiconti della Classe di scienze fisiche, matematiche e naturali, Série 8, Tome 55 (1973) no. 5, pp. 506-514

Résumé

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.