Question

Would you expect the composition 2Na2O• B2O3•4SiO2to be a good glass-former, based on Zachariasen’s rules? Explain your reasoning.

Answer 1

SiO2, B2O3, GeO2, P2O5 the above oxides will form glasses and other oxides like MgO, Al2O3, Na2O, CaO will not glasses according to Zachariasen’s rule.

Zachariasen’s rule is No oxygen atom may be linked to more than two cations 2. The cation coordination number is small: 3 or 4. 3. Oxygen polyhedra share corners, not edges or faces. 4. For 3D networks, at least three corners must be shared

From the above we can expect that  2Na2O• B2O3•4SiO2 will not be a good glass-former since it contains Na2O