Cation ordering in Li2Mn3MO8 spinels: structural and vibration spectroscopy studies

Lithium-manganese oxide spinels with 1/4 manganese replaced by Mg, Ti, Co, Ni, Cu, Zn and Ga, yielding formula LiMn1.5M0.5O4 (or Li2Mn3MO8) have been prepared. Cationic ordering was known previously for M=Mg and Zn, resulting in a superstructure with primitive cubic symmetry. Given the poor chemical...

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Bibliographic Details
Published in:	Solid state sciences 2003-07, Vol.5 (7), p.1009-1018
Main Authors:	STROBEL, Pierre, IBARRA-PALOS, Alejandro, ANNE, Michel, POINSIGNON, Christiane, CRISCI, Alexandre
Format:	Article
Language:	eng
Subjects:	Chemical Sciences Condensed matter: structure, mechanical and thermal properties Exact sciences and technology Inorganic compounds Material chemistry Physics Structure of solids and liquids crystallography Structure of specific crystalline solids Water, oxides, hydroxides, peroxides
Online Access:	Get full text
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Summary:	Lithium-manganese oxide spinels with 1/4 manganese replaced by Mg, Ti, Co, Ni, Cu, Zn and Ga, yielding formula LiMn1.5M0.5O4 (or Li2Mn3MO8) have been prepared. Cationic ordering was known previously for M=Mg and Zn, resulting in a superstructure with primitive cubic symmetry. Given the poor chemical contrast of X-ray diffraction between Mn and Ti, Co, Ni, Cu or Ga, neutron diffraction studies were carried out. Evidence of cation ordering is found for M=Ni and Cu, but not for Ti, Co or Ga. These results are confirmed by FTIR and Raman spectroscopies. Doubly-substituted samples (Li0.5M0.5)[Mn1.5M0.5]O4 (overall formula LiMn3M2O8) were also prepared for M=Mg and Zn. These do not form the primitive superstructure, a result ascribed to the lower manganese valence with respect to LiMn1.5M0.5O4. Zn-containing spinels give rise to an extensive Li/Zn cation inversion, which also shows up as additional high-frequency bands in IR and Raman spectroscopies. This investigation shows that the cell volume is determined by the average octahedral-site cation radius, and that the main driving force for octahedral cation ordering is the charge difference between Mn and M atoms.
ISSN:	1293-2558 1873-3085