Irradiation induced order-disorder phase transformation in A ₄Zr₃O₁₂ (A = Sc, Lu and Dy)

In this study, 200 keV Ne⁺ ion irradiations were performed under cryogenic conditions (∼77 K) on δ-phase oxide compounds with formula, A₄Zr₃O₁₂ (A = Sc, Lu and Dy). An order-to-disorder (O-D) phase transformation was observed in δ-Lu ₄Zr₃O₁₂ and δ-Sc₄Zr ₃O₁₂ after Ne⁺ ion irradiation, but no phase change was observed in Dy₄Zr₃O₁₂. The latter compound exhibited a disordered fluorite structure before and after irradiation. The threshold doses to produce O-D phase transformations using Ne⁺ ions were found to be significantly lower than for similar irradiations (reported previously) using Kr⁺⁺ ions. This suggests that light ions are more efficient than heavy ions in producing the retained defects that are ultimately responsible for the observed O-D transformation. The ion irradiation-induced O-D transformations observed here are discussed in terms of analogous transformations found in temperature-composition (T-C) phase diagrams for A₄Zr₃O₁₂ compounds.