A Diffuse Reflectance Study of Synthetic Acanthite, Stibnite and Bournonite

Acanthite (Ag₂S), Stibnite (Sb₂S₃) and Boumonite (CuPbSbS₃) were synthesized by the evacuated silica tube method under dry conditions. Boumonite was synthesized both from its elemental composition and from the component sulfides. All the products were characterized by the optical and XRD methods and were found to be pure, homogeneous and direct semiconductors.

Diffuse reflectance studies were undertaken on these synthetic mineral phases. The forbidden energy gap (E_g) was calculated by α² vs. hν plots and linear extrapolation to α² = zero. E_g was also deduced by calculating the Kubelka - Munk remission function, and plotting it against the photon energy. The E_g values obtained were: acanthite 0.98, 1.0 eV; stibnite 1.50, 1.55 eV and boumonite 1.15, 1.23 eV. Possible industrial application of these syntheti∼ semiconducting mineral phases are discussed.