Structural study of Ca–Mg and K–Mg mixing in silicate glasses by neutron diffraction

Neutron diffraction has been used to study the structure in two series of xCaO.(2 − x)MgO.2SiO2 and xK2O.(2 − x)MgO.4SiO2 glasses and the effect of Ca–Mg and K–Mg mixing, showing a different chemical dependence of the structure of these mixed glasses. The data are consistent with a random mixing of CaSiO3 and MgSiO3 structures for the Ca/Mg substitution. The coordination of Ca and Mg remains constant in Ca–Mg silicate glasses but a decrease of Mg coordination is observed in the K–Mg silicate glasses with the addition of K2O. In these latter glasses, the medium range order is also significantly affected by the K/Mg substitution, due to the distinct structural role played by K and Mg in these glasses.