Diffusion and Exchange of Zinc in Crystalline Zinc Sulfide

The diffusion and exchange of zinc vapor with crystals of zinc sulfide has been measured from 925 to 1075°C. The measured exchange rate was observed to be controlled by the diffusion of Zn in ZnS. A critical examination of the log D versus 1/T plot reveals that three distinct diffusion processes are operative in the temperature range studied. At 1 atmos zinc pressure, the diffusion coefficients were calculated as D=3×10−4exp(−35 kcal/RT) cm2 sec−1below 940°C, D=1.5×104exp(−75 kcal/RT) cm2 sec—1 between 940° and 1030°C, and D=1×1016exp(−150 kcal/RT) cm2sec−1above 1030°C. Variation of zinc pressure from 0.25 to 2.0 atmos showed that D varies as PZn1.5. Values of D were observed to increase with increasing penetration of Zn into the ZnS crystals. The kinetic and structural interpretations of these results are discussed.