Hydrogen diffusion in proton-exchanged lithium niobate single crystals
Hydrogen diffusion in proton-exchanged lithium niobate single crystals
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DOI：
10.1063/5.0047606
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发表时间：
2021-04-07
影响因子：
3.2
通讯作者：
Schmidt, Harald
中科院分区：
文献类型：
--
作者：
Doerrer, Lars;Tuchel, Philipp;Schmidt, Harald
在140 - 200 ℃温度范围内研究了氢在质子交换同成分铌酸锂单晶中的扩散。质子交换过程在苯甲酸和苯甲酸锂（1 mol.%）的混合物中进行。导致高达2 μ m厚的表面层，其中Li被H取代约60%（约12 at.% LiNbO 3中的H）。对于扩散实验，使用氘化苯甲酸作为示踪源，氢/氘同位素交换在200摄氏度及以下的温度下发生。同位素敏感深度剖面分析是通过二次离子质谱法进行的。从实验结果中，有效的扩散系数的锂/氢交换和示踪扩散系数的交换层内的氘提取。这两种类型的扩散率可以用阿克里尼乌斯定律来描述，活化焓约为1.2 eV，而有效扩散率低三个数量级。这一结果表明氢的扩散不是质子交换过程的速率决定步骤。讨论了氢示踪剂扩散的可能机制。
Hydrogen diffusion in proton-exchanged congruent LiNbO3 single crystals is investigated in the temperature range between 140 and 200 degrees C. The proton-exchange process carried out in a mixture of benzoic acid and lithium benzoate (1mol.%) results in an up to 2 mu m thick surface layer where Li is substituted by H for about 60% (about 12 at.% H within LiNbO3) as determined by nuclear reaction analysis. For the diffusion experiments, deuterated benzoic acid is used as a tracer source and the hydrogen/deuterium isotope-exchange occurs at temperatures of 200 degrees C and below. Isotope sensitive depth profile analysis is done by secondary ion mass spectrometry. From the experimental results, effective diffusivities governing the lithium/hydrogen exchange and tracer diffusivities of deuterium within the exchanged layer are extracted. Both types of diffusivities can be described by the Arrhenius law with an activation enthalpy of about 1.2 eV, while the effective diffusivities are lower by three orders of magnitude. This result shows that the diffusion of hydrogen is not the rate-determining step for the proton-exchange process. Possible diffusion mechanisms of hydrogen tracer diffusion are discussed.