Measurements of Electrical Conductivity and Magnetoresistance of Gray Tin Filaments

A method for the preparation of gray tin filaments suitable for electrical measurements is described. Results of measurements of the temperature dependence of the electrical conductivity and of the magnetoresistance on pure gray tin and on alloys containing various amounts of Sb, As, In, Al, and Zn are reported. For 99.998 percent pure tin the activation energy is 0.082 ev and the conductivity at 0°C is 2090 ${\mathrm{ohm}}^{-1\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$. Addition of impurities results in an increase in the "intrinsic" activation energy and a decrease in the absolute value of the conductivity in the "intrinsic" range. Samples doped with $n$-type impurities exhibit a positive temperature coefficient of resistance at low temperatures whereas the low-temperature conductivity of $p$-type samples becomes temperature-independent at high impurity concentrations. The three $p$-type impurities In, Zn, and Al show marked differences in their effectiveness in producing $p$-type conductivity, In being 40 times more effective than Al. The magnetoresistance coefficient in the lattice-scattering region shows a stronger temperature dependence than is predicted by the simple theory. Impurity scattering appears to be relatively more important in $p$-type than in $n$-type material.