Electrical Measurements on Natural Galena at Low Temperatures

The Hall effect and resistivity of n-type single crystals of natural galena containing from 6 × 10 15 to 10 19 extrinsic electrons per cm 3 have been measured from room temperature down to liquid helium temperatures. No appreciable change in the number of extrinsic electrons has been observed down to 4°K in any crystal. While the mobility is proportional to T -5/2 down to a temperature of about 70°K, the low temperature mobility varies with the number of extrinsic electrons in a manner which cannot be explained by current theories of scattering. It is estimated that at room temperature a purely intrinsic crystal of PbS would contain 2 × 10 15 conduction electrons per cm 3 .