Anomalous structural phase transformation in swift heavy ion-irradiated δ-Sc₄Hf₃O₁₂

Swift heavy ion irradiation was carried out to examine the ionization effects on structural changes of δ-Sc 4 Hf 3 O 12 in which oxygen vacancies are regularly arranged. The specimens were irradiated at room temperature with 92 MeV xenon ions fluences ranging from × 10 1 14 /cm 2 and characterized by grazing (glancing) incidence x-ray diffraction, transmission electron microscopy, scanning microscopy. It found that pristine long-range ordered rhombohedral δ-phase undergoes a reconstructive transformation toward disordered cubic oxygen-deficient fluorite phase promoted effects. In addition, an short-range structure different δ-type formed layer going surface depth ∼4.5 μm specimen fluence . is phase. This change anomalous, because it opposite process usual irradiation-induced change, order-to-disorder transformation. Electron diffraction experiments revealed regions this possess oxygen-excess bixbyite organization (C-type rare-earth oxides) randomly filled anion vacant sites account for stoichiometry average