ELECTRICAL CONDUCTIVITY OF SOME SOLIDS AT AND BELOW ROOM TEMPERATURE

Abstract

Gray Iron samples alloyed with tin in small proportions have been studied for their electrical resistivity properties. The Tin content were varied in steps of 0.05% within a total range of 0.00-0.35% Tin. Three independent sets of samples were prepared. Measurements were made on each set of samples in the temperature range from 85-1173K. In general each sample shows positive value of dP /dT over a very wide temperature range, from 85 to 773K(measurements below 85K have not yet been done). The numerical values of dP /dT for the different samples of the same series of alloy, however, differ substantially. A graphical plot of dP /dT against % of Tin shows a significant inflexion at about 0.1% Tin for each of the three sets of samples. This is suggestive of some ordering effect in the composition range of 0.1-0.15% Tin. Interestingly The British cast and Iron Research Association has also reported a definite magnetic transition in similar alloys at a composition of about 0.1% Tin.For an understanding of the Physics of this transition, a good deal of further investigations would be required. Magnetoresistance measurements of these materials were also undertaken at room temperature. These are very preliminary measurements, and are only significant in so far as that they do indicate significant magnetoresistance effects. These measurements need to he followed up further, and one may expect to observe some significant effect in the composition range of 0.1-0.15% Tin.There is very little information available in literature on this material, and so the present study is useful in its own right.