Structural approach of sialon glasses: MSiAlON

Abstract

Glass samples with the formular composition: M II 0.37 Si 0.53 A 0.10 O 1.58 − 3x 2 N x′ (M II = Mg, Ca or Ba) and M I 0.46 Si 0.46 Al 0.08 O 1.27 − 3x 2 N x (M I = Li) have been studied by infra-red absorption spectroscopy. The nitrogen-free alkaline-earth glass structure is built up with SiO 4 and AlO 4 linked units as in the metasilicate glasses. The M II cations are network modifiers, except Mg, which participate in the formative network inducing a certain part of the A 3+ cations in six-fold co-ordination which play the role of network modifiers. The lithium glass presents a silicate layer structure formed with (Si 2O 5) − units and Al 3+ ions in four and/or five-fold co-ordination; the Li + cations are located between the layers. The presence of nitrogen leads to very high cross-linkage of aluminosilicate chain or layer. The M II cations are inserted into increasingly large sites (Mg- to Ba- glasses). The structural change could be correlated with the physical properties: the network rigidity increases from Ba- to Mg- glasses and with the amount of nitrogen, and the disorder was emphasized with an increasing amount of nitrogen, but especially from Mg- to Ba- glasses. These effects are less perceptible for the lithium glasses with a layer structure.