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Cation distribution in LiMgVO4 and LiZnVO4: structural and spectroscopic study
D Capsoni1, M Bini, V Massarotti
1Dipartimento di Chimica Fisica, M. Rolla dell'Università, viale Taramelli 16, 27100 Pavia.
The Journal of Physical Chemistry. B
|March 17, 2006
Summary
Cation distribution in LiMgVO(4) and LiZnVO(4) was studied using X-ray diffraction and NMR. LiMgVO(4) shows cation exchange, while LiZnVO(4) exhibits higher disorder across multiple sites.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Crystallography
Background:
- Understanding cation distribution in mixed metal oxides is crucial for tuning their properties.
- LiMgVO(4) and LiZnVO(4) are relevant materials with potential applications.
Purpose of the Study:
- To determine the room temperature cation occupancy in LiMgVO(4) and LiZnVO(4) crystallographic sites.
- To investigate the impact of cation distribution on structural and vibrational properties.
Main Methods:
- Combined use of X-ray powder diffraction (XRPD) and (7)Li and (51)V magic angle spinning nuclear magnetic resonance (MAS NMR).
- Micro-Raman spectroscopy and Rietveld refinement method for full profile fitting of XRPD patterns.
- High-temperature XRPD measurements to assess structural stability.
Main Results:
- LiMgVO(4) exhibits ordered vanadium on tetrahedral sites, with ~22% reciprocal cationic exchange between Li and Mg on tetrahedral and octahedral sites.
- LiZnVO(4) shows higher cationic disorder, with vanadium distributed across three cationic sites (~25%, 26%, 47%).
- Li(+) and Zn(2+) show preferred site occupations in LiZnVO(4) (T1 and T2 positions, respectively), and vibrational spectra reflect cation distribution and local distortions.
Conclusions:
- The study elucidates the distinct cation distribution patterns in LiMgVO(4) and LiZnVO(4).
- Cation disorder significantly influences the vibrational properties of these materials.
- Both compounds remain structurally stable up to 673 K.
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