GRAIN-BOUNDARY CONTRIBUTION TO ELECTRICAL RESISTIVITY OF IRON

The electrical resistivity of irons containing different levels of impurity have been measured at 77°and 293°K for a range of grain sizes. The resistivity of a given iron is found to vary with the grain diameter (d mm) as ρ = A+B log(1/d). A and B are both temperature dependent, increasing with increasing temperature. With increasing impurity content, the parameter A increases and B decreases. Thus the purer iron shows a larger variation of resistivity with grain size than the less pure material. The observed relationship can only be explained in terms of a grain-boundary scattering process if the effective width of the boundaries is much greater than is usually believed. © 1969 The American Institute of Physics.