MAS NMR study of soda-lime-silicate glasses with variable degree of polymerisation

²⁹Si and ²³Na magic angle spinning (MAS) NMR has been used as an atomic probe for structural characterisation of soda-lime-silicate glasses. The glasses studied are based on the composition (CaO)_x(Na₂Si₃O₇), where x is varied from x = 0 to x = 1, (increasing CaO from 0 to 20 mol%) finally matching the Na₂O fraction. The glass network becomes increasingly depolymerised by increasing CaO, and shows a changing distribution of Qⁿ species. Two Q species have been observed co-existing for compositions, where x = 0, 0.2 and 1, while for compositions, where x = 0.4 and x = 0.8, Q², Q³ and Q⁴ are present. Progressive changes in chemical shifts of Q² and Q³ species, and changes in FWHM of all detected Qⁿ species accompany the addition of CaO. The addition of CaO introduces a greater distortion into the structure, and there is evidence to suggest preferential arrangement of Ca in the vicinity of Q² species rather than Q³.