Two compounds have been studied: an oxide glass from the Y-Si-Al-O system and an oxynitride glass from the Y-Si-Al-O-N system, both bombarded with Sn-ions (975 MeV, fluences ranging from 10(12) to 2.7 x 10(13) Sn/cm(2)). The changes in the environment of the silicon and the aluminium were investigated using NMR spectroscopy. Irradiation by Sn ions leads to a loss of nitrogen in the silicon and probably the aluminium environments. Part of the aluminium changes from a network former coordination to a network modifier coordination while the oxide silicate network exhibits a higher cross-linking due to an increase of the population of bridging oxygen. Part of the aluminium in five-fold coordination is formed at the expense of aluminium in six-fold coordination in the case of the oxynitride glass and the changes in the silicon environment occur at lower fluences than for the oxide glass. (c) 2006 Published by Elsevier B.V.