Electrical and optical properties of natural iron pyrite (FeS2)

The optical and transport properties of naturally occurring mineral pyrite (FeS2) are measured with a view to determine Eg, the energy gap of this semiconductor and to determine the scattering mechanism in the low temperature region (80 and 270 K). Analysis of the optical absorption studies indicate pyrite to be an indirect band gap semiconductor in which a single phonon makes an important contribution in assisting this transition. Conductivity and Hall effect data in the intrinsic range yield a value of 0.92 eV at room temperature for the energy gap, in close agreement with the value obtained by optical absorption studies. The analysis of the conductivity and Hall effect data in the low temperature region for all the n-type samples indicates acoustic mode scattering to be an important scattering mechanism. The thermo-power measurements in this temperature region also independently suggest acoustic mode scattering to be operative in a majority of samples. The general behaviour of p-type samples of pyrite by the measurements or those in the literature points to complicated transport properties.