Inhomogeneous distribution of Na+ in alkali silicate glasses

Abstract

We investigated the Na+ environment in sodium silicate glasses and mixed alkali silicate glasses using 23Na multiple-quantum magic-angle spinning (MQMAS) NMR spectroscopy, ab initio molecular orbital (MO) calculations, and Na+ elution analysis. The 23Na MQMAS NMR spectra of Na2OxSiO2 and (1 - y)Na2OyM 2O2SiO2 (M = Li, K) glasses showed an inhomogeneous distribution of local structures around Na+, even though spectral deconvolution was impossible. The quantum chemical calculations indicated that the alkali silicate glasses contained both aggregated and isolated Na+ sites. The elution behavior also supported the local structure distribution described above. These results indicated that a cation with a high cation field strength tends to aggregate in mixed silicate glasses. © 2011 The Ceramic Society of Japan.