Cr incorporated phase transformation in Y₂O₃ under ion irradiation

Under irradiation, chemical species can redistribute in ways not expected from equilibrium behavior. In oxide-dispersed ferritic alloys, the phenomenon of irradiation-induced Cr redistribution at the metal/oxide interfaces has drawn recent attention. Here, the thermal and irradiation stability of the FeCr/Y₂O₃ interface has been systematically studied. Trilayer thin films of 90 nm Fe - 20 at.% Cr (1^st layer)/100 nm Y₂O₃ (2^nd layer)/135 nm Fe - 20 at.% Cr (3^rd layer) were deposited on MgO substrates at 500 °C. After irradiation, Cr diffuses towards and enriches the FeCr/Y₂O₃ interface. Further, correlated with Cr redistributed into the oxide, an amorphous layer is generated at the interface. In the Y₂O₃ layer, the original cubic phase is observed to transform to the monoclinic phase after irradiation. Meanwhile, nanosized voids, with relatively larger size at interfaces, are also observed in the oxide layer. First-principles calculations reveal that Cr substitution of Y interstitials in Y₂O₃ containing excess Y interstitials is favored and the irradiation-induced monoclinic phase enhances this process. Our findings provide new insights that may aid in the development of irradiation resistant oxide-dispersed ferritic alloys.