<i>In-Situ</i> Evaluation of Functional Layer Based on Impedance Behavior

Abstract

The characterization of Zr oxide layer formed in Ar and O 2 gas mixture at 973 K on the surface of Zr metal was characterized by electrochemical impedance spectroscopy (EIS). The increase of the layer thickness and the formation of the horizontal crack in the layer were evaluated in situ using EIS. The thickness of the Zr oxide layer estimated by EIS agreed well with that by EPMA analysis. It was found that the time constant t of the Zr oxide layer obtained by the EIS increased with the oxidation time. This trend indicated the growth of horizontal crack. The constant phase element (CPE) parameter p was obtained from the results of EIS. The change of p indicated that the Zr oxide layer has the gradient of the chemical composition in its thickness direction. The single horizontal crack and compositionally gradient in the oxide layer was modeled as they electrically functioned in the equivalent circuits. The simulation results indicated that the EIS method can be used as the in situ monitor the gradient of the chemical composition and the crack formation in the oxide layer.