Strontium environment transition in tin silicate glasses by neutron and X-ray diffraction

The effect of Sr modifier atoms on the structure of stannosilicate glasses of composition (Sr0) x (SnO) 0.5− x (SiO 2) 0.5, with 0 ⩽ x ⩽ 0.15, has been studied using Mössbauer spectroscopy and neutron and X-ray diffraction. The tin is mostly in the Sn 2+ state. The Sr–O bond length undergoes a step decrease from (2.640 ± 0.005) Å to (2.585 ± 0.005) Å as x increases from 0.10 to 0.15, indicating a decrease in co-ordination number from 8 to 7. A Sn–Sn distance of 3.507 ± 0.005 Å is revealed by a first-order difference calculation from the x = 0 sample. This is too short to be consistent with significant edge sharing of [SnO 3] trigonal pyramids.