Li⁺ diffusivity in 5 mol%MgO-doped LiNbO₃ crystal and Li-poor vapor transport equilibration effect on its surface composition

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• 作者：Zhen Wang^a ; ^b ; Ping-Rang Hua^a ; ^b ; ^c ; Shuai Zhang^a ; ^b ; Dao-Yin Yu^a ; ^b ; Edwin Yue-Bun Pun^c ; De-Long Zhang^a ; ^b ; ^c ; ^{dlzhang@tju.edu.cn} ; ^{delongzhang@eyou.com}
• 关键词：MgO (5  ; mol%) ; LiNbO3 crystal ; Li+ diffusivity ; Li-poor VTE ; Surface composition
• 刊名：Journal of Alloys and Compounds
• 出版年：2012
• 期刊代码：45_09258388
• 类别：ms
• 出版时间：25 July, 2012
• 卷：530
• 期：Complete
• 页码：152-156
• 文件大小：210 K

摘要

Diffusivity of Li⁺ in 5 mol%(in growth melt) MgO-doped LiNbO₃ crystal has been studied as a function of Li₂O-content ranging from 43.4 to 44.4 mol%under different temperatures. First, diffusion-limited Li₂O-content depth profiles were produced by carrying out Li-poor vapour transport equilibration (VTE) treatments on two 0.5-mm-thick MgO-doped LiNbO₃ plates at 1100 and 1130 掳C for 40 h. Second, the profiles were obtained by alternatively doing the optical polish to one crystal surface and the Li₂O-content characterization on the polished surface through the measurement of birefringence. Third, Boltzmann-Matano method was applied to the profile to derive the Li⁺ diffusivity as a function of Li₂O-content. The results show that the diffusivity decreases with the reduced Li₂O-content by at least two orders of magnitude as the Li₂O-content reduces by 1 mol%from the as-grown state. In the Li₂O-content range studied, the diffusivity at 1130 掳C is at least two times larger than that at 1100 掳C. In addition, we also studied the time dependence of the Li-poor-VTE-induced reduction of Li₂O-content on surface of the same MgO-doped crystal. The results show that the surface Li₂O-content reduction induced has a square-root dependence on the VTE duration. Based upon this dependence, the mathematical solution to the Li⁺ diffusion equation, an integral of error function complement, is obtained and verified by the experimental result. It is concluded that the MgO doping has less effect on both the Li⁺ diffusivity and the dependence of surface Li₂O-content reduction on the VTE duration.