H diffusion in Mg- and Be- doped ⍺Al2O3 (corundum) single crystals

IF 3 4区材料科学 Q3 CHEMISTRY, PHYSICAL

Solid State Ionics Pub Date : 2024-11-21 DOI:10.1016/j.ssi.2024.116730

Michael C. Jollands , Shiyun Jin , Daniel C. Jones , Roland Stalder

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引用次数: 0

Abstract

The diffusivity of hydrogen, as protons, in Mg- and Be-doped corundum has been determined from 544 to 1007 °C, by annealing single crystals in CO₂-H₂ or N₂-H₂ mixes at ambient pressure. The addition of hydrogen leads to decolorization of the crystals, which is attributed to the associated removal of electron holes. Spatially resolved semi-quantitative profiles of hydrogen concentration versus distance were recorded using Fourier transform infrared spectroscopy, and/or Cr luminescence lifetime spectroscopy. These show hydrogen diffusion associated with trapping by Mg or Be, which leads to characteristic step shaped (broadly sigmoidal) forms of concentration-distance profiles. Numerical modelling of this diffusion-plus-trapping process allows hydrogen diffusion coefficients to be extracted, which are several orders of magnitude higher than any diffusion coefficients that have been previously determined in this system. This discrepancy is attributed to previous studies not taking trapping behaviour into account. Re-analysis of some published data, now considering trapping, can explain a ∼ 4-5 orders of magnitude discrepancy in calculated diffusion coefficients.

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掺镁和掺铍的 ⍺Al2O3（刚玉）单晶中的氢扩散

通过在环境压力下将单晶体在 CO2-H2 或 N2-H2 混合气体中退火，测定了掺镁和掺铍刚玉中氢气（质子）在 544 ℃ 至 1007 ℃ 范围内的扩散率。氢的加入会导致晶体脱色，这是由于电子空穴的移除所致。利用傅立叶变换红外光谱和/或 Cr 发光寿命光谱记录了氢浓度随距离变化的空间分辨半定量曲线。这些结果表明，氢的扩散与镁或铍的捕获有关，从而导致浓度-距离曲线呈现出特征性的阶梯形（大致为正余弦形）。通过对这一扩散加捕获过程进行数值建模，可以提取出氢扩散系数，该系数比以前在该系统中测定的任何扩散系数都要高出几个数量级。造成这种差异的原因是以前的研究没有将捕获行为考虑在内。重新分析一些已发表的数据，现在考虑到了捕获行为，可以解释计算出的扩散系数在数量级上有 4 至 5 个数量级的差异。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Solid State Ionics 物理-物理：凝聚态物理

CiteScore

6.10

自引率

3.10%

发文量

152

审稿时长

58 days

期刊介绍： This interdisciplinary journal is devoted to the physics, chemistry and materials science of diffusion, mass transport, and reactivity of solids. The major part of each issue is devoted to articles on: (i) physics and chemistry of defects in solids; (ii) reactions in and on solids, e.g. intercalation, corrosion, oxidation, sintering; (iii) ion transport measurements, mechanisms and theory; (iv) solid state electrochemistry; (v) ionically-electronically mixed conducting solids. Related technological applications are also included, provided their characteristics are interpreted in terms of the basic solid state properties. Review papers and relevant symposium proceedings are welcome.