Application of microcalorimetry in studies of interaction between oxygen and NiO single crystals

Abstract

International audienceMicrocalorimetry was used to study the interaction between gaseous oxygen and NiO single crystals. The studies involved consecutive sorption of small and large oxygen doses at 1000 K. Fast and slow processes of oxygen incorporation into NiO were distinguished. The fast process involved oxygen sorption in the near-surface layer. Then oxygen incorporation was ratecontrolled by a slow lattice diffusion in the crystalline bulk. A power of oxygen pressure dependence was found (1/n = 1/4.25) which was consistent with the defect structure of NiO. Heat of formation of cation vacancies was determined [&#916_f=155 kJ/mole]

Stoichiometric and Nonstoichiometric Compounds

“…Because of excess oxygen and vacancies on Ni site, nickel oxide thus becomes a ptype metal-deficit semiconductor [8]. The findings of investigations done by authors suggest that Ni vacancy is the most dominant point defect present in the system, rather than oxygen interstitial [13,14]. The distribution of vacancy over a particular volume is an important issue.…”