NMR investigations on ion dynamics and structure in nanocrystalline and polycrystalline LiNbO3

被引:50
作者
Bork, D [1 ]
Heitjans, P [1 ]
机构
[1] Univ Hannover, Inst Phys Chem & Elektrochem, D-30167 Hannover, Germany
来源
JOURNAL OF PHYSICAL CHEMISTRY B | 2001年 / 105卷 / 38期
关键词
D O I
10.1021/jp012409w
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
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 Li-7 spin-lattice relaxation (SLR) rate T-1(-1) in the laboratory and T-1e(-1) in the pulsed rotating reference frame and of (ii) Li-7 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 T-1(e)(-1) proportional to v(-beta) with beta in the range from 1. 1 to 1.5 as well as the asymmetry of the diffusion-induced peak in the log T-1e(-1) vs T-1 diagram of p-LiNbO3 are proving non-BPP behavior for both samples. (3) In n-LiNbO3 MN starts already at 250 K, i.e., about 400 K lower than in p-LiNbO3, and reflects an apparent activation energy that is approximately 1/3 of the value found for the p-material. (4) In contrast to p-LiNbO3, with increasing temperature the Li-7 NMR spectra of n-LiNbO3 are revealing a characteristic structure of the central line, namely a superposition of two contributions. This is regarded as a consequence of the different dynamic properties of atoms in the interfacial regions (IR) and in the grains. From the spectrum at 450 K the fraction of atoms belonging to IR can be estimated. (5) The intensities of the quadrupole satellites showing different temperature dependencies in the p- and n-samples are indicating some exchange between the two spin reservoirs 'IR' and 'grains'. This leads to the hypothesis that n-ceramics cannot simply be regarded as heterogeneous materials where the two types of zones, i.e., IR and grains, are independent and closed.
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收藏
页码:9162 / 9170
页数:9
相关论文
共 19 条
[1]   RELAXATION EFFECTS IN NUCLEAR MAGNETIC RESONANCE ABSORPTION [J].
BLOEMBERGEN, N ;
PURCELL, EM ;
POUND, RV .
PHYSICAL REVIEW, 1948, 73 (07) :679-712
[2]   SOLID-STATE NMR-STUDY SUPPORTING THE LITHIUM VACANCY DEFECT MODEL IN CONGRUENT LITHIUM-NIOBATE [J].
BLUMEL, J ;
BORN, E ;
METZGER, T .
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 1994, 55 (07) :589-593
[3]  
BOGDANOV VL, 1968, FIZ TVERD TELA+, V10, P886
[4]   NMR relaxation study of ion dynamics in nanocrystalline and polycrystalline LiNbO3 [J].
Bork, D ;
Heitjans, P .
JOURNAL OF PHYSICAL CHEMISTRY B, 1998, 102 (38) :7303-7306
[5]   QUADRUPOLE EFFECTS IN NUCLEAR MAGNETIC RESONANCE STUDIES OF SOLIDS [J].
COHEN, MH ;
REIF, F .
SOLID STATE PHYSICS, 1957, 5 :321-438
[6]   JUMP RELAXATION IN SOLID ELECTROLYTES [J].
FUNKE, K .
PROGRESS IN SOLID STATE CHEMISTRY, 1993, 22 (02) :111-195
[7]   NANOCRYSTALLINE MATERIALS [J].
BIRRINGER, R .
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 1989, 117 :33-43
[8]   TEMPERATURE DEPENDENCE OF LI NMR-SPECTRUM AND ATOMIC MOTION IN LINBO3 [J].
HALSTEAD, TK .
JOURNAL OF CHEMICAL PHYSICS, 1970, 53 (09) :3427-&
[9]   Ilmenite-like stacking defect in nonstoichiometric lithium niobate crystals investigated by Raman scattering spectra [J].
Kong, YF ;
Xu, JJ ;
Chen, XJ ;
Zhang, CZ ;
Zhang, WL ;
Zhang, GY .
JOURNAL OF APPLIED PHYSICS, 2000, 87 (09) :4410-4414
[10]   LI-7 NMR RELAXATION BY DIFFUSION IN HEXAGONAL AND CUBIC LIXTIS2 [J].
KUCHLER, W ;
HEITJANS, P ;
PAYER, A ;
SCHOLLHORN, R .
SOLID STATE IONICS, 1994, 70 :434-438