Influence of the network on conductivity in ternary CaO–Al2O3–SiO2 glasses and melts

The electrical conductivity of ternary CaO–Al2O3–SiO2 compositions has been studied both in the solid and the liquid states. Below Tg, calcium migration, described well by an Arrhenius law, is highly influenced by the non-bridging oxygen (NBO) content. A fast enhancement of the conductivity occurs for glasses containing a content of NBO higher than 30–35% which corresponds to a percolation threshold. Above Tg, the temperature dependence of the conductivity is better described by a Vogel–Tammann–Fulcher (VTF) law and the NBO content is no more the pertinent parameter. In the melt state, the network characterised by the silica content, becomes the main parameter that governs the temperature dependence of the conductivity.