Measurement of Tracer Diffusion Coefficient of Sulfur in Solid Calcium Sulfide by IMA

Abstract

In order to identify the electric charge carrier in an ion-conductive calcium sulfide, tracer diffusion coefficients of sulfur have been measured by IMA (Ion Micro-Analyzer). Stable isotope ³⁴S diffused by a gas-solid reaction was analyzed in depth by continuous sputtering of the sample. The tracer diffusion coefficient determined from the in-depth profile of ³⁴S was expressed for a temperature range from 1053 to 1483 K by;
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Using the measured diffusion coefficient and the Nernst-Einstein relation, the electrical conductivity by S ion was estimated. The estimated conductivity was 10 to 100 times smaller than the reported measured value. The activation energy for sulfur tracer diffusion was 1.5 times greater than that for electrical conduction. These results confirm the deduction that the electric charge carrier in CaS is predominantly Ca²⁺.