Vibrational investigation of lithium metaborate-metaaluminate glasses and crystals

• Published in: Journal of non-crystalline solids 1997-09, Vol.217 (2), p.278-290
• Main Authors: Chryssikos, G.D., Bitsis, M.S., Kapoutsis, J.A., Kamitsos, E.I.
• Format: Article
• Language: English
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/S0022-3093(97)00224-X

Lithium metaborate-metaaluminate glasses xLiAlO 2·(1− x)LiBO 2, (0≤ x ≤0.42), and crystals (Li 3B 2AlO 6, Li 2BAlO 4) have been prepared and studied by infrared and Raman spectroscopies. The two crystalline compounds have similar networks made of AlØ 4 − and BØ 2O − units (Ø, O: bridging and terminal oxygen atoms, respectively) in arrangements which maximize the number of BOAl linkages. Both compounds decompose at high temperatures into α-LiBO 2 and γ-LiAlO 2. Increasing x in glass induces the isomerization of BØ 4 − tetrahedra to BØ 2O − triangles, while aluminum forms AlØ 4 − units. This structural scheme is sufficient to account for the minimum in the glass transition temperature observed for x ≈ 0.25. There is no vibrational evidence for the presence of AlO 5 or AlO 6 polyhedra in glass, although their presence in small amounts cannot be excluded. Glasses and crystals of the same stoichiometry ( x = 0.33) are differentiated by an excess of kinetically arrested BOB and AlOAl linkages in the former.