Local Coordination of Low-Spin Ni3+ Probes in Trigonal LiAlyCo1-yO2 Monitored by HF-EPR
Local Coordination of Low-Spin Ni3+ Probes in Trigonal LiAlyCo1-yO2 Monitored by HF-EPR
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DOI：
10.1021/jp0376119
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发表时间：
2004-03
影响因子：
3.3
通讯作者：
R. Stoyanova;E. Zhecheva;R. Alcántara;J. Tirado
中科院分区：
文献类型：
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作者：
R. Stoyanova;E. Zhecheva;R. Alcántara;J. Tirado
用高频电子顺磁共振（EPR）研究了低自旋Ni ~（3+）探针在LiAlyCo_（1-y）O_2中的局域配位。该技术允许区分两种类型的Ni 3+离子：三角晶场（2 Eg基态）中的Ni 3+离子和四角晶场（2A 1g基态）中的Ni 3+离子。当Ni 3+离子处于均匀的Co环境中时，Ni 3+的轨道简并态被保留，并且可以观察到基态电子振动双重态的EPR谱（中间Jahn-Teller效应）。g1的值随着平均M−O键的收缩而减小。Ni ~（3+）离子在Co ~（6-）-γ-Aly混合环境中，出现了局域四重态畸变。沿着Al逐渐取代Co的方向，Ni 3+的晶场强度逐渐增强，四方畸变程度呈增加趋势。当Ni 3+离子福尔斯落在纯Al环境中时，Jahn-Teller畸变效应达到最大。
The local coordination of low-spin Ni3+ probes in trigonal LiAlyCo1-yO2 was studied using high-frequency EPR spectroscopy. This technique allows distinguishing between two types of Ni3+ ions: Ni3+ ions in trigonal crystal field (2Eg ground state) and Ni3+ ions in tetragonal crystal field (2A1g ground state). When a Ni3+ ion is in a uniform Co environment, the orbitally degenerate state for Ni3+ is preserved and the EPR spectrum of the ground vibronic doublet state can be observed (intermediate Jahn−Teller effect). The value of g1 decreases as the mean M−O bond is contracted. The local tetragonal distortion can be observed for Ni3+ ions located in a mixed Co6-yAly environment. Along the progressive replacement of Co by Al, the strength of the crystal field for Ni3+ increases gradually and the extent of the tetragonal distortion displays a tendency to increase. The maximum effect of Jahn−Teller distortion is achieved when the Ni3+ ion falls in a pure Al environment.