Acoustic Spectra of Glasses in the System Na2O-B2O3
The subject of the structure of vitreous B2O3 and Na2O-B2O3 glasses has been a controversial one for many years. Initially Warren(l) proposed a theory, based mainly on x-ray studies, that vitreous B2O3 is composed of BO3 triangles, with each oxygen shared between two borons. The addition of Na2O up to 15 mole % introduces extra oxygen into the network, converting some of these triangles to BO4 tetrahedra. The extra oxygens are doubly-bonded to boron and thereby strengthen the network. At Na2O contents greater than 15%, no more tetrahedra are formed, rather singly-bonded oxygens are produced in the same manner as they are in Na2O-SiO2 glasses. This results in broken B-O-B linkages with a consequent weakening of the network. On the basis of NMR investigations, however, it appears that BO4 tetrahedra are produced continuously up to about 30–35 mole % Na2O. An extension of these concepts is made through the work and theory of Krogh-Moe(3) which states that the BO3 triangles and BO4 tetrahedra are not merely joined at corners in a random network, but that the structure contains well-defined borate groups randomly distributed.
KeywordsBorate Glass Sodium Borate Acoustic Spectrum Boric Oxide Soda Glass
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