Cation distribution in LiMgVO4 and LiZnVO4: structural and spectroscopic study.
Cation distribution in LiMgVO4 and LiZnVO4: structural and spectroscopic study.
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DOI：
10.1021/jp057088t
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发表时间：
2006-02
期刊：
影响因子：
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通讯作者：
D. Capsoni;M. Bini;V. Massarotti;P. Mustarelli;F. Belotti;P. Galinetto
中科院分区：
文献类型：
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作者：
D. Capsoni;M. Bini;V. Massarotti;P. Mustarelli;F. Belotti;P. Galinetto
通过X-射线粉末衍射(XRPD)、(7)Li和(51)V魔角旋转核磁共振(MAS)和显微拉曼光谱测量，得到了LiMgVO(4)和LiZnVO(4)晶位的室温阳离子占有率。在LiMgVO(4)CMCM正交结构中，4c(C(2)(V)对称性)四面体钒位是完全有序的，相反，Li4c四面体和4b(C(2)(H)对称性)镁八面体位置表现出约22%的倒易阳离子交换。在LiZnVO(4)中观察到较高的阳离子无序性：这三个阳离子可以分布在R-3结构的三个四面体和不同的位置上。XRPD和MAS核磁共振分析结果与钒离子在三个阳离子位置(约25%、26%和47%)上的分布高度一致。用Rietveld方法对XRPD谱进行全谱拟合，还得到Li(+)对T1位(约55%)和Zn(2+)对T2位(约46%)的轻微优先占据。两种化合物的振动光谱具有不同的峰位和展宽的拉曼模式，反映了阳离子的分布和局域振动单元的失真。并与最近Li(3)VO(4)的拉曼光谱结果进行了比较。高温XRPD测量排除了这两种化合物在673K以下可能发生的结构转变。
The room temperature cation occupancy in LiMgVO(4) and LiZnVO(4) crystallographic sites is obtained by means of the combined use of X-ray powder diffraction (XRPD), (7)Li and (51)V magic angle spinning nuclear magnetic resonance (MAS NMR), and micro-Raman measurements. In the LiMgVO(4) Cmcm orthorhombic structure, the 4c (C(2)(v) symmetry) tetrahedral vanadium site is fully ordered; on the contrary, the Li 4c tetrahedral site and the 4b (C(2)(h) symmetry) Mg octahedral site display about 22% of reciprocal cationic exchange. Higher cationic disorder is observed in LiZnVO(4): the three cations can distribute on the three tetrahedral and distinct sites of the R-3 structure. XRPD and MAS NMR analysis results highly agree for what concerns vanadium ion distribution on the three cationic sites (about 25, 26, and 47%). From the full profile fitting of XRPD patterns with the Rietveld method, it is also obtained that Li(+) displays a slightly preferred occupation of the T1 position (approximately 55%) and Zn(2+) of the T2 position (approximately 46%). The vibrational spectra of the two compounds are characterized by different peak positions and broadening of the Raman modes, reflecting the cation distribution and the local vibrational unit distortion. A comparison is also made with recent Raman results on Li(3)VO(4). High temperature XRPD measurements rule out possible structural transitions up to 673 K for both compounds.