Interfacial pattern formation in the Pt-Ni-O system studied by Energy-Filtering Transmission Electron Microscopy

During a solid state electrochemical experiment, a μm-sized nickel oxide single crystal nucleated at the interface between yttria-stabilized zirconia (YSZ) and platinum. Detailed analyses by energy-filtering transmission electron microscopy (EFTEM) of the platinum - nickel oxide interface revealed an onset of periodic nano-layer formation between the nickel oxide and the platinum. Elemental distribution maps of O, Ni and Pt confirmed the presence of interfacial layers of different chemical composition. Electron energy-loss spectra (EELS) linescans across the interface were recorded to obtain quantitative compositional profiles. Theoretical and experimental considerations suggest that the crystal and the periodic patterns developed due to similar mechanistic principles. The results are discussed within a framework of theories on solid state pattern formation and the oxidation of alloys, such as the Kirkendall effect, Liesegang mechanisms, and Wagner's oxidation mechanisms.