Though present in small amounts and migrating at low rates, intrinsic cation defects play a central role in governing the operational lifetime of oxide-ion conducting materials through slow degradation processes such as interdiffusion, kinetic demixing, grain growth, and creep. In this study, a new experimental approach to characterizing the behavior of such slow-moving, minority defects is presented. Diffusion is probed in samples with a constant cation-defect concentration well above the equilibrium values. This approach is applied to monoclinic hafnium dioxide, m-HfO2. To this end, nanocrystalline thin films of m-HfO2 were prepared by atomic layer deposition. Diffusion experiments with ZrO2 as a diffusion source were performed in the temperature range 1173 ≤ T/K ≤ 1323 in air. The Zr diffusion profiles obtained subsequently by secondary ion mass spectrometry exhibited the following two features: the first feature was attributed to slow bulk diffusion and the second was attributed to combined fast grain-boundary diffusion and slow bulk diffusion. The activation enthalpy of Zr diffusion in bulk HfO2 was found to be (2.1 ± 0.2) eV. This result is consistent with the density-functional-theory calculations of hafnium-vacancy migration in m-HfO2, which yield values of ∼2 eV for a specific path. The activation enthalpy of the grain-boundary diffusion of (2.1 ± 0.3) eV is equal to that for bulk diffusion. This behavior is interpreted in terms of enhanced cation diffusion along space-charge layers.

中文翻译：

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通过原子层沉积沉积的单斜 HfO2 多晶薄膜中的阳离子扩散

尽管存在少量并以低速率迁移，固有阳离子缺陷在通过缓慢降解过程（例如相互扩散、动力学分层、晶粒生长和蠕变）控制氧化物离子导电材料的使用寿命方面发挥着核心作用。在这项研究中，提出了一种新的实验方法来表征这种缓慢移动的少数缺陷的行为。在具有远高于平衡值的恒定阳离子缺陷浓度的样品中探测扩散。这种方法适用于单斜二氧化铪，m-HfO2。为此，通过原子层沉积制备了 m-HfO2 纳米晶薄膜。以 ZrO2 作为扩散源的扩散实验在空气中 1173 ≤ T/K ≤ 1323 的温度范围内进行。随后通过二次离子质谱法获得的 Zr 扩散曲线表现出以下两个特征：第一个特征归因于缓慢的体扩散，第二个特征归因于快速晶界扩散和慢体扩散的结合。发现散装 HfO2 中 Zr 扩散的活化焓为 (2.1 ± 0.2) eV。该结果与 m-HfO2 中铪空位迁移的密度泛函理论计算一致，对于特定路径产生 ~2 eV 的值。(2.1 ± 0.3) eV 的晶界扩散的激活焓等于体扩散的激活焓。这种行为被解释为沿空间电荷层的增强的阳离子扩散。第一个特征归因于缓慢的体扩散，第二个特征归因于快速晶界扩散和慢体扩散的结合。发现散装 HfO2 中 Zr 扩散的活化焓为 (2.1 ± 0.2) eV。该结果与 m-HfO2 中铪空位迁移的密度泛函理论计算一致，对于特定路径产生 ~2 eV 的值。(2.1 ± 0.3) eV 的晶界扩散的激活焓等于体扩散的激活焓。这种行为被解释为沿空间电荷层的增强的阳离子扩散。第一个特征归因于缓慢的体扩散，第二个特征归因于快速晶界扩散和慢体扩散的结合。发现散装 HfO2 中 Zr 扩散的活化焓为 (2.1 ± 0.2) eV。该结果与 m-HfO2 中铪空位迁移的密度泛函理论计算一致，对于特定路径产生 ~2 eV 的值。(2.1 ± 0.3) eV 的晶界扩散的激活焓等于体扩散的激活焓。这种行为被解释为沿空间电荷层的增强的阳离子扩散。该结果与 m-HfO2 中铪空位迁移的密度泛函理论计算一致，对于特定路径产生 ~2 eV 的值。(2.1 ± 0.3) eV 的晶界扩散的激活焓等于体扩散的激活焓。这种行为被解释为沿空间电荷层的增强的阳离子扩散。该结果与 m-HfO2 中铪空位迁移的密度泛函理论计算一致，对于特定路径产生 ~2 eV 的值。(2.1 ± 0.3) eV 的晶界扩散的激活焓等于体扩散的激活焓。这种行为被解释为沿空间电荷层的增强的阳离子扩散。