Diffusion of Selenium-75 in Lead Chalcogenides

The diffusion of Se‐75 has been studied in crystals of PbS, PbSe, and PbTe annealed under argon at 700°C. The relative diffusivities were $\mathrm{D(}\mathrm{PbS}\mathrm{)\approx D(}\mathrm{PbSe}\mathrm{)⪝D(}\mathrm{PbTe})$ . Adding bismuth to PbSe yields a higher diffusivity than in undoped crystals of PbSe while additions of silver do not change the diffusivity. At 700°C the diffusivity of selenium in PbSe was studied as a function of selenium partial pressure. For 10⁻⁴ ≤ pSe₂ ≤ 80 Torr, D ∝ pSe₂^1/4 while for pSe₂ > 80 Torr, D ∝ pSe₂^1/2. For pSe₂ < 10⁻⁴ Torr, the diffusivity was not a function of selenium pressure.