Ionic Conductivity in Glasses and Melts (Up to 1950K): Application to the CaO–SiO2 System

The electrical properties of the CaO–SiO2 system have been investigated in a wide temperature range (up to 1950 K) using a specific device developed in this laboratory. Conductivity data were obtained in the liquid, undercooled-liquid, and glassy states for two different compositions. In the solid state, the conductivity is determined by the jump of the Ca2+ cations along the non-bridging oxygens. This mechanism is thermally activated with a high activation energy value. A second regime was observed in the molten state where the conductivity follows the phenomenological Vogel–Tammann–Fulcher (VTF) law. In this regime, the conductivity is enhanced because the softening and the deformation of the network facilitate the migration of the alkaline-earth cations.