Ion Beam Modification of High-Entropy Oxides

High-entropy oxides (HEOs) have recently gained recognition for their low thermal conductivity and tunable mechanical capabilities, but little is known about their response to high energy heavy ion beams. In this work, the heavy-ion irradiation response of HEOs with the pyrochlore and perovskite structures has been investigated. The damage accumulation behavior at 300 K due to 4 MeV Au ion irradiation of a <100>-oriented HEO titanate pyrochlore single crystal has been investigated by Rutherford backscattering spectrometry in channeling geometry and transmission electron microscopy (TEM). In addition, in situ TEM irradiation using 600 keV Xe ions has been employed to reveal the dose and temperature dependence of amorphization in a HEO pyrochlore with the same composition. In another single-crystal HEO titanate pyrochlore composition, amorphization due to 23 MeV Ni ions has been characterized by Raman spectroscopy, which indicates a much higher dose for amorphization, suggesting significant athermal recovery during irradiation due to the high electronic energy loss of the Ni ions. Ion tracks formed in a HEO perovskite structure irradiated with 774 MeV Xe ions have been characterized by TEM, and the stability of these ion tracks under electron beam irradiation has been evaluated. The results obtained on these HEO structures are compared to those of their single-component counterparts.