Abstract
In order to obtain unambiguous results, the surface conductivity measurements were carried out on intentionally leached specimens of a sodium-aluminium silicate glass. The surface conductivity of rod shaped samples was determined at 25°C at various humidities and was interpreted on the basis of the sodium ion distribution in the surface layer. The surface conductivity increases with humidity only in highly wet atmosphere; in the lower part of the humidity range, however, it is constant. The constant value has been attributed to an interior stratum which is clearly not exposed to the direct influence of the atmosphere. The excess of the surface conductivity above this level may be due to a moisture surface film, which vanishes in less humid atmosphere, or to a very thin gel layer. On specimens of glass electrode type, the contribution of the surface layer to the resistance of the electrode wall was determined and a highly resisting surface layer fraction was detected. Both high maximum and deep minimum in conductivity were established within the leached layer. The differences in (volume) conductivity between the subsequent strata are estimated to be in the range of orders of magnitude. Some hypotheses concerning the conduction mechanism are presented.
Published Version
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