On the relations between ISE and structure in some RE(Mg)SiAlO(N) glasses

Six oxide and oxynitride glasses were synthesized in theY–Mg–Si–Al–O–N, Nd–Mg–Si–Al–O–Nand La–Mg– Si–Al–O–N systems. As already known, nitrogen introduction increases the Tg, packing factor and mechanical properties of the glasses. Cationic substitution also has an influence on the glasses’ behavior, particularly in terms of sensitivity to indentation load/size effect (ISE). The structure of the yttrium-containing glasses was investigated bymean of 27Al and 29Si MAS-NMR. Al is found to occur for 2/3 as a network former and for 1/3 as a modifier. The oxide glass mainly contains Q2 and Q3 silicate units and SiO3N and SiO2N2 units are created when nitrogen is introduced into the glass network.The average number of rigid bonds per network former hni was calculated from the glasses’ composition. A discrepancy betweenhniand the Raman spectra of the glasses suggests that parts of the magnesium behaves as a former in the network. hni seems to be a key parameter governing hardness and sensitivity to ISE and can be linked to normal/ abnormal behavior of glasses regarding indentation.