Structure and rheological properties of the RE-Si-Mg-O-N (RE = Sc, Y, La, Nd, Sm, Gd, Yb and Lu) glasses

Structure, viscosity, glass transition temperature, Littleton
temperature and elastic moduli were investigated by MAS-NMR
spectroscopy, compressive creep, dilatometry and ultrasound velocity
experiments, in order to reveal the effects of rare earth elements and
nitrogen on the behavior of RE-Si-Mg-O-N glasses (RE = Sc, Y, La, Nd,
Sm, Gd, Yb and L) with different nitrogen contents. NMR showed that
nitrogen modifies the glass structure depending on RE type via
increasing content of SiO3N(+Q(1)) units at the expense of Q(2) units
and Lu seems to be more effective in their formation than La. Despite
that, the effects of rare-earth modifiers and nitrogen as network
former are independent, additive and a synergy effect was not observed.
Approximately linear dependencies of most properties on molar volume
(and ionic radii) suggest that glass network is tightened
proportionally to ionic radius of corresponding modifier and
cross-linking is proportional to nitrogen content. However, the
mechanism involved in lanthanide effect is different from that of Sc
and Y additives, although they result in properties similar to those of
... mehrLu-containing glasses. Irregularities found for Yb and Sm additives at
elevated temperatures may be related to the change of valence state.