Local structure of nickel oxide grown at high temperatures in ceramic electrolyte cells

Abstract

A study of the local structure of nickel oxide grown at high temperatures in solid-state electrochemical cells as well as the basic concept of the oxidation technique are reported. XANES at the oxygen K-threshold and EXAFS at the nickel K-edge in nickel oxide have been measured. XANES spectroscopy at the oxygen K-edge shows the defective nature of the oxide grown electrochemically. The nickel 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 determination of the interatomic distance change in defective nickel oxide and (3) for the identification of the presence of defective Ni sites. A tentative correlation between the oxide structure and oxidation technique is reported. The difference in the oxide defectivity is explained in terms of a retarding electric field effect on the oxidation kinetics.