Effect of composition on ionic transport in SiO2–B2O3–Na2O glasses

Ionic diffusion was investigated in the SiO2–B2O3–Na2O glass system over a wide composition range by impedance spectroscopy measurements. The Na+ cation transport mechanism was described by an interstitial pair migration model based on Frenkel defects in ionic crystals. The activation energy of the static electrical conductivity is shown to be correlated with the boron coordination number in these glasses. Published 11B NMR results were used to calculate the activation energies of sodium cations acting as charge compensators for the [BO4/2]− tetrahedron and of sodium cations bonded to non-bridging oxygen atoms. These values are in agreement with the activation energies of the Na2O–B2O3 and Na2O–SiO2 binary systems, respectively.