Indentation moduli and microhardness of RE–Si–Mg–O–N glasses (RE=Sc, Y, La, Sm, Yb and Lu) with different nitrogen content

The indentation moduli and microhardness of RE–Si–Mg–O–N glasses (RE=Y, Sc and lanthanides La, Sm, Yb and Lu) containing 20–24 eq.% of nitrogen were found to depend on RE type and nitrogen content as well. The Lu-containing glasses were approximately 15–28% harder than La-glasses with the same nitrogen content and 4% increase in nitrogen content results in 1 to ∼10% increase of microhardness. The effectiveness of the RE elements with regard to their ability to increase selected mechanical properties of the oxynitride glasses rises from La, Y/Sc/Sm to Yb and Lu. The properties studied increase approximately linearly with cationic field strength (CFS) of the corresponding lanthanide cation in the glass network. The properties of Y- and Sc-containing glasses do not follow this dependence. These changes cannot be explained in terms of CFS and additional effects have to be considered to characterize relationships between composition, structure, and properties in the glasses containing non-lanthanide elements.