Yttrium SiAlON glasses: Structure and mechanical properties - Elasticity and viscosity

Two series of oxynitride glasses in the YSiAlON system, with varying ratios of Al/Si and Al/Y, were studied from both structural and mechanical point of view. A Raman scattering study showed that by changing the Al content, at constant Y cationic equivalent concentration (e/o), aluminum substitutes for silicon without affecting the degree of polymerisation (cross-linking) of the glass network, whereas at constant Si e/o, replacement of yttrium by aluminum results in a higher polymerisation degree. The effect of glass composition on the hardness, Young's modulus, the thermal expansion coefficient and the glass transition temperature range are discussed in light of the corresponding structural changes.