Characterisation of the Electrical Properties of Wastes Vitrified from Canarian Island Basaltic Quarries: Original Glasses and Glass-Ceramics

We obtained original glasses and glass-ceramics through the controlled melting and recrystallisation of basalt rocks extracted from several quarries in the Canary Islands. The electrical measurements of the resulting glasses and glass-ceramics were conducted in a complex impedance at temperatures in the 250–700 °C range. These electrical determinations made it possible to follow the nucleation and crystal growth processes. The main crystalline phases were pyroxenes, feldspar (anorthite) and magnetite, which decorate the dendritic crystallisation of pyroxenes. The magnetite is present as nanocrystals, being the component chiefly responsible for the electrical conduction properties of these glass-ceramics. Electrical conduction is facilitated by the presence of magnetite nanocrystals on the axes of dendrites of pyroxene crystals, enabling polar electron conduction in these materials. Thus, the Fe2+/Fe3+ ratio was related to the total Fe2+/Fe, which made it possible to express an electronic conduction model.