The diffusivity in 2 glasses from this system was studied. Both samples had the same Al:Y:Si atom ratio, 1:1.36:2.32, but one of them contained 8.09at%N. The diffusivities were found by using the residual activity method and radio-isotopes. The composition of the oxynitride glass was similar to that which formed at the grain boundaries of Si3N4 ceramics which were sintered with Y2O3 and Al2O3 as additives. It was found that the Na and Fe diffusivities were always greater in the N-free glass than in the N-containing glass. The values of the other diffusion parameters did not follow any general trend. The diffusivities, at temperatures ranging from 690 to 920C, could be described by:

DNa (cm2/s) = 3.39 x 10-11 exp[-52.9(kJ)/RT]

and

DFe (cm2/s) = 4.17 x 102 exp[-356.7(kJ)/RT]

in the case of the oxynitride glass. In the case of the oxide glass, the equivalent values were:

DNa (cm2/s) = 1.0 x 10-8 exp[-91(kJ)/RT]

and

DFe (cm2/s) = 2.5 x 10-8 exp[-123(kJ)/RT]

It appeared that the diffusion of both Na and Fe occurred via interstitials in the case of the oxide glass. In the case of the oxynitride glass, there was a change to a vacancy mechanism for Fe.

T.Das, A.S.Sanyal, J.Mukerji: Physics and Chemistry of Glasses, 1995, 36[4], 191-3