Structure and ionic conductivity of nitrated lithium disilicate (LiSiON) glasses

Lithium disilicate is a critical glass forming composition as it is the basis of some glass-ceramics and it is also a model glass for the study of homogeneous and heterogeneous crystal nucleation. Incorporation of nitrogen in this glass significantly changes its structure and affects different properties. In this paper, nitrided lithium disilicate glasses were prepared by partial substitution of oxygen up to 6 atm % N/ (N + O). The modification of the silicate glass structure with nitrogen has been confirmed by Fourier transform infrared reflection (FTIR) spectroscopy. Si-29 NMR and Li-7 NMR have also been used to investigate the structural changes due to nitrogen incorporation. Substitution of oxygen by nitrogen with a higher coordination number (three) increases the connectivity of the glass. In fact, our NMR results indicate that nitrogen incorporation changes the Q(n) distribution (n = average number of bridging oxygens to silicon) of the silicate structural units: SiNO3, SiN(2)O(2 )and SiN3O, whereas there is no detectable change in the Li environment. We measured the ionic (Li+) conductivity by impedance spectroscopy and found that the incorporation of nitrogen leads to a decrease in the activation energy for conduction, resulting in an increase of up to four-fold in the ionic conductivity of the most nitrided glass. We explained this high conductivity by the Anderson and Stuart model. This work provides renewed interest in improving and understanding the ionic conductivity in oxynitride glasses. (C) 2018 Elsevier B.V. All rights reserved.