Polycrystalline samples of Cr203 with an average grain size of about 6.5 ~m and with negligible residual porosity were prepared from ultrapure Cr203 powder sintered at 1873 K under purified argon. Monocrystalline, as well as the polycrystalline samples, were sectioned into small parallelepipeds, polished and exposed to 3~S at Pso2 = 10 -2 atm and Po2 --0.8-1.0 atm in a sealed quartz tube at temperatures from 1173 to 1373 K. The sulfur penetration was determined by measuring the activity of the sample after removing successive layers (3-5 ~m) by abrasion polishing. The volume diffusion coefficients measured 1.07-5.0 • 10 -'3 cm 2 s -~ with an activation energy of 27.6 kcal, whereas the grain boundary diffusion coefficients were about 5 orders of magnitude higher than the volume diffusion coefficients with an activation energy of about 40 kcal. The results indicated that grain boundary diffusion appears to be the predominant mechanism of sulfur transport for the polycrystal]ine samples. Alloys containing Fe, Ni, and Cr which generally show ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.129.120.3 Downloaded on 2015-07-06 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.129.120.3 Downloaded on 2015-07-06 to IP
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