Fundamental aspects of ion-irradiation-induced phase transformations in fluorite-related oxides, from cubic to monoclinic structures, are investigated through xenon implantation at medium energy in yttrium sesquioxide (Y₂O₃). For that purpose, an original approach considering this material fabricated as a thin film is proposed to control the pristine structure before irradiation and to allow fine measurements of internal stresses. It is evidenced that this oxide can be strongly disordered up to an unexpected amorphization, depending on the initial damage state. We emphasize that point defects created during the irradiation process generate strong internal stresses which turn out to be a major parameter in the mechanism involved during such phase transition. When the oxide structure is initially weakly disordered, the evolutions of the biaxial and triaxial residual stresses, together with the lattice parameter, presents two different steps. Those steps are interpreted at the atomic scale by the nucleation of oxygen vacancy aggregates which collapse in extended dislocation loops that are considered as monoclinic nuclei. The geometry of these extended defects has been considered to explain why the monoclinic phase appears with clearly defined crystallographic orientation relationship (4 0 $\overline{2}$)^B//(2 2 2)^C relative to the initial cubic phase. The link between the energy deposited by irradiation and the critical size of these defects, analyzed from a thermodynamical approach by the evaluation of the Gibbs free energy, also elucidates the presence of sharp thresholds observed between the different phases (amorphous/cubic and monoclinic/amorphous) along the depth of the film.

通过中等能量的倍半氧化钇（Y ₂ O _3）中的氙注入，研究了萤石相关氧化物从立方到单斜晶结构中离子辐照引起的相变的基本方面。）。为此，提出了一种将这种材料制成薄膜的原始方法，以在辐照之前控制原始结构并精确测量内部应力。有证据表明，取决于初始损伤状态，该氧化物会强烈地杂乱直至意外的非晶化。我们强调，在辐照过程中产生的点缺陷会产生很强的内应力，而内应力却成为相变过程中所涉及机制的主要参数。当氧化物结构最初微弱地无序时，双轴和三轴残余应力的演化以及晶格参数呈现两个不同的步骤。这些步骤在原子尺度上通过氧空位聚集体的成核来解释，这些空位聚集体在被认为是单斜晶核的扩展位错环中坍塌。这些扩展缺陷的几何形状已被认为可以解释为什么单斜晶相以明确的晶体取向关系出现（4 0$\overline{\mathrm{2个}}$）^B //（2 2 2）^C相对于初始立方相。通过热力学方法通过吉布斯自由能的评估分析了辐照沉积的能量与这些缺陷的临界尺寸之间的关系，也阐明了在不同相（非晶/立方和单斜/非晶）之间观察到的尖锐阈值的存在。 ）沿着胶片的深度。