Self Diffusion of Sulfur-35 in Single Crystals of Lead Sulfide
Abstract
The diffusion of radioactive sulfur (S35) into single crystals of lead sulfide has been studied as a function of deviation from stoichiometry and defect concentration introduced by doping, in the temperature range 773 degK to 1023 degK, in order to determine the predominant mechanism by which the anion diffuses in this compound. Measurements have been made using crystals whose composition varied from 3 x 10 (exp 18) excess sulfur atoms per cc. to 5 x 10 (exp 18) excess lead atoms per cc. The sulfur excess specimens showed the highest diffusivities in this temperature range, whereas lowest diffusion coefficients were obtained in the lead excess specimens. Diffusion measurements have also been performed on specimens doped with 0.5 or 0.05 mole percent Ag2S or Bi2S3 which were annealed under the same conditions as those required to obtain undoped stoichiometric PbS crystals. Results indicate that the nature of the bonding forces between the components of PbS may be the most important single factor in determining the process by which diffusion occurs in partially polar compounds. The data is consistent with Jumps of divalent, negatively charged sulfur ions into anion vacancies as a mode of diffusion only in PbS containing a large excess of lead. In lead sulfide containing excess of sulfur, or small excess lead concentrations, sulfur is believed to diffuse primarily as a small, positively charged species, by jumps into vacancies in the cation sublattice, or by sole interstitial mechanism.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 22, 1961
- Accession Number
- AD0268251
Entities
People
- J. B. Wagner Jr.
- Martin S. Seltzer
Organizations
- Yale University