Irradiation-induced order-to-disorder phase transformation at different temperatures in Dy2O3

Polycrystalline pellets of the rare earth sesquioxide Dy2O3 were irradiated at two temperatures (∼120 K and ∼300 K) with 300 keV Kr++ ions up to a fluence of 1 × 1020 Kr/m2. The crystal structure of the irradiated Dy2O3 was observed to change from an ordered cubic bixbyite structure (so-called C-type rare earth sesquioxide structure) to a disordered, anion-deficient fluorite structure. A relatively low ion dose (∼2.5 displacements per atom [dpa]) was sufficient to induce a complete order-to-disorder (O-D) phase transformation at cryogenic temperature (∼120 K) irradiation, while at room temperature (∼300 K) a higher dose (∼25 dpa) produced only a partial O-D phase transformation.