NMR Investigations on Ion Dynamics and Structure in Nanocrystalline and Polycrystalline LiNbO3
NMR Investigations on Ion Dynamics and Structure in Nanocrystalline and Polycrystalline LiNbO3
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纳米晶和多晶 LiNbO3 中离子动力学和结构的 NMR 研究
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
P. Heitjans
中科院分区：
文献类型：
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作者：
Detlef Bork and;P. Heitjans
采用高能球磨法从平均晶粒尺寸为1 μ m的多晶（p-）材料中制备出平均晶粒尺寸在16 ~ 105 nm之间的纳米晶（n-）LiNbO 3样品。NMR研究（i）实验室中的7 Li自旋晶格弛豫（SLR）速率T1-1和脉冲旋转参考系中的T1 e-1，以及（ii）7 Li光谱，特别是中心线的线形和运动窄化（MN），在p-LiNbO 3的情况下，在300 K至最大1400 K的温度范围内进行，在n-LiNbO 3的情况下，在140至460 K的温度范围内进行。获得了以下结果。(1)SLR速率测量得出n-LiNbO 3中Li扩散的表观活化能约为p型材料所得值的1/3。(2)在β为1.1 ~ 1.5的范围内，SLR速率随T_1（e）~（-1）τ ν-β的频率变化关系以及扩散诱导峰在对数T_1（e）~（-1）-T ~（-1）图上的不对称性都证明了这一点。
Nanocrystalline (n-) LiNbO3 samples with average grain sizes between 16 and 105 nm were prepared from polycrystalline (p-) material with an average grain size of the order of one micrometer by high-energy ball milling. NMR investigations of (i) the 7Li spin−lattice relaxation (SLR) rate T1-1 in the laboratory and T1e-1 in the pulsed rotating reference frame and of (ii) 7Li spectra, in particular line shapes and motional narrowing (MN) of the central line, were performed in the temperature range from 300 K to a maximum of 1400 K in the case of p-LiNbO3 and from 140 to 460 K in the case of n-LiNbO3. The following results were obtained. (1) The SLR rate measurements yield an apparent activation energy of the Li diffusion in n-LiNbO3 that is about 1/3 of the value obtained for the p-material. (2) The frequency dependence of the SLR rate according to T1(e)-1 ∝ ν-β with β in the range from 1.1 to 1.5 as well as the asymmetry of the diffusion-induced peak in the log T1e-1 vs T -1 diagram of p-LiNbO3 are proving ...