SELF-DIFFUSION OF LEAD AND TELLURIUM IN LEAD TELLURIDE.
LOCKHEED MISSILES AND SPACE CO SUNNYVALE CALIF
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The defect structure of PbTe was investigated by studying the self-diffusion of Pb and Te as a function of deviation from stoichiometry and temperature. Microlapping and radioactive tracer techniques were used to determine the diffusion coefficients from concentration vs. penetration profiles corresponding to the Van Ostrand-Dewey solution of Ficks second law. The self-siffusion of Pb-210 can be explained by assuming that two mechanisms operate, one at high Te concentrations with an activation energy of 61 Kcal per mole and one at low Te concentrations and excess Pb with an activation energy equal to 24 Kcal per mole. The diffusion coefficient D sub pb exhibited a minimum at all temperatures and at compositions close to stoichiometry, on the Te side. The Te self-diffusion coefficient decreases with decreasing Te concentration and has an activation energy equal to 24 Kcal per mole. From the dependence of the diffusivities upon concentration and temperature it has been concluded that Frenkel defects are present in the Pb sublattice and that interstitial Te is the predominant anion defect. Author