Ion-irradiation-induced phase transformation in rare earth sesquioxides (Dy2O3,Er2O3,Lu2O3)

Abstract

Polycrystalline pellets of cubic C-type rare earth structure (Ia3¯) Dy2O3, Er2O3, and Lu2O3 were irradiated at cryogenic temperature (120K) with 300keV Kr++ ions to a maximum fluence of 1×1020Kr∕m2. Irradiated specimens were examined using grazing incidence x-ray diffraction and transmission electron microscopy. Ion irradiation leads to different radiation effects in these three materials. First, Dy2O3 begins to transform to a monoclinic B-type rare earth structure (C2∕m) at a peak dose of ∼5 displacements per atom (dpa), (corresponding to a fluence of 2×1019Kr∕m2). This transformation is nearly complete at a peak dose of 25 dpa (a fluence of 1×1020Kr∕m2). Er2O3 also transforms to the B-type structure, but the transformation starts at a higher irradiation dose of about 15–20 dpa [a fluence of about (6–8)×1019Kr∕m2]. Lu2O3 was found to maintain the C-type structure even at the highest irradiation dose of 25 dpa (a fluence of 1×1020Kr∕m2). No C-to-B transformation was observed in Lu2O3. The irradiation dose dependence of the C-to-B phase transformation observed in Dy2O3, Er2O3, and Lu2O3 is closely related to the temperature dependence of the C-to-B phase transformation found in phase diagrams for these three materials.