Electrical conduction in ion-exchanged glass fibres containing aluminium dispersoids

Abstract

Glass fibres containing ultrafine aluminium particles of diameters of a few hundred angstroms have been made. The electrical resistivity of these fibres at temperatures below approximately 400 K arises due to an electron tunnelling mechanism between the metal islands. Fibres, on being subjected to a sodium to or from silver ion-exchange treatment exhibit an increase in conductivity and a decrease in activation energy as compared to those of the virgin fibres. On application of a critical field of the order of 20 V cm-1 at temperatures around 500 K a high conductivity state is induced in the ion-exchanged fibres. This arises due to the connectivity brought about in the disjointed silver-rich phase as a consequence of the applied electrical field. The activation energy values in this state encompass a wide range namely, 0.03 to 0.36 eV. This is believed to arise due to the significant differences in composition and structure of the silver-rich phases in ion-exchanged samples prepared with different amounts of aluminium metal powder in the starting batch.