We studied lithium tracer diffusion in proton-exchanged congruent LiNbO₃ single crystals in the temperature range between 150 and 230 °C. Proton exchange was done in benzoic acid with 1 mol% lithium benzoate added, resulting in a surface layer where Li is substituted by H for about 60% (about 12 at.% H within LiNbO₃). For the diffusion experiments, ion-beam sputtered isotope enriched ⁶LiNbO₃ was used as a tracer source. Isotope sensitive depth profile analysis was carried out by secondary ion mass spectrometry in depth profile mode. From the experimental results effective diffusivities governing the lithium/hydrogen exchange and lithium tracer diffusivities are extracted. Both types of diffusivities are identical within error limits and follow the Arrhenius law with an activation enthalpy of about 1.2 eV. In contrast, the lithium tracer diffusivities are lower by three orders of magnitude than hydrogen tracer diffusivities which were recently determined by our group. The results indicate that the diffusion of Li is the rate determining step for the proton-exchange process.

我们研究了在150至230°C的温度范围内，质子交换的全LiNbO ₃单晶中锂示踪剂的扩散。质子交换是在苯甲酸中进行的，添加了1 mol％的苯甲酸锂，形成了一个表面层，其中Li被H取代了约60％（LiNbO _3中约12 at。％H ）。对于扩散实验，离子束溅射同位素富集了⁶ LiNbO ₃被用作示踪剂源。同位素敏感的深度剖面分析是通过二次离子质谱在深度剖面模式下进行的。从实验结果中提取出控制锂/氢交换的有效扩散率和示踪剂锂的扩散率。两种类型的扩散率在误差范围内都相同，并遵循阿伦尼乌斯定律，其激活焓约为1.2 eV。相反，与我们小组最近确定的氢示踪剂扩散率相比，锂示踪剂的扩散率降低了三个数量级。结果表明，Li的扩散是质子交换过程的速率决定步骤。