Microstructural evolution of protective La-Cr-O films studied by transmission electron microscopy

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Transmission Electron Microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS) were performed to study the microstructural evolution of La-Cr-O thin films deposited by radio frequency (RF)-magnetron sputtering on stainless steel substrates. Chromium L edges and oxygen K edges are analyzed to determine the valence states of the chromium and elucidate the phase evolution of the thin film. The as-deposited amorphous thin film crystallized to LaCrO4 and finally transformed to the LaCrO3 stable phase during annealing at 800°C. An intermediate Cr/Mn oxide layer was formed in all annealed samples. The thickness of this oxide layer stabilizes after 700°C, which indicates that the LaCrO3 thin film plays a role in inhibiting the growth of an oxide layer on the metal surface.

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Journal of Solid State Electrochemistry