The influence of chromium on the defect structure and their mobility in nonstoichiometric cobaltous oxide Original Research Article

Defect structure and the mobility of point defects in pure metal deficient cobalt oxide (Co1−yO) and in Co1−yO–Cr2O3 solid solutions have been studied as a function of temperature (1223–1573 K) and oxygen pressure (10–105 Pa) using microthermogravimetric techniques. It has been shown that the predominant defects in pure and Cr-doped cobaltous oxide are singly ionized cation vacancies, and 3% at of dopant is high enough to fix the concentration of predominant defects in such solid solutions on a constant level being much higher than in pure Co1−yO. Re-equilibration rate measurements have demonstrated that the chemical diffusion coefficient and thereby the mobility of point defects in pure Co1−yO is concentration independent, strongly suggesting that in spite of rather high their concentration no interactions and clustering of defects is to be expected. On the other hand, in Cr-doped cobaltous oxide, re-equilibration rate measurements have shown, that in this case the defect structure is more complicated, although singly ionized cation vacancies seem to be still predominant defects.