LOCAL-STRUCTURE OF NICKEL-OXIDE GROWN AT HIGH-TEMPERATURES IN CERAMIC ELECTROLYTE CELLS

A study of the local structure of nickel oxide grown at high temps. in solid-state electrochem. cells as well as the basic concept of the oxidn. technique are reported. XANES (x-ray absorption near-edge structure) at the O K-threshold and EXAFS at the Ni K-edge in Ni oxide were measured. XANES spectroscopy at the O K-edge shows the defective nature of the oxide grown electrochem. The Ni K-edge EXAFS is sensitive to the change in the oxide stoichiometry and was used: (1) for a rough evaluation of the defectivity value, (2) for the detn. of the interat. distance change in defective Ni oxide and (3) for the identification of the presence of defective Ni sites. A tentative correlation between the oxides structure and oxidn. technique is reported. The difference in the oxide defectivity was explained in terms of a retarding elec. field effect on the oxidn. kinetics