Electro-conducting glass-ceramics produced by ion-exchange and reduction treatments

Abstract

The crystallization characteristics of some bismuth-containing soda-lime-silica glasses have been studied. The addition of bismuth reduces the glass transition temperature as well as the crystallization temperatures of these glasses. Electrically conducting layers have been induced in such glass-ceramics by subjecting them to a Na⁺ ⇔Ag⁺ ionexchange reaction followed by a reduction treatment in hydrogen. Resistances of the surfaces vary from 0.08 Ω/square to 14.76 Ω/square depending on the glass composition as well as the reduction parameters. Induced surface conductance tends to rise with the increase of volume of the crystalline phase in the parent glass. The TCR values range between 400 and 2300 p.p.m. K^-1. The thicknesses of these layers are about 130 μm. The high surface conductivity arises from the percolation of the silver metallic phase in the glass-crystal boundary region. The glass-crystal interface is believed to act as heterogeneous nucleation sites.