[Research on IR spectra of Li-Mn spinel]

The infrared spectra of Li-Mn-spinel were studied in this paper. As the structure of Li-Mn-spinel was classified as Fd3m space group, the lithium ions (Li(I)) occupy tetrahedral sites (8a sites) and manganese ions (Mn(IV) or Mn(III)) occupy octahedral sites (16d sites). The internal relationship between vibration modes and infrared activity was discussed based on the knowledge of group theory. The experimental IR spectra of Li-Mn-spinel were presented also. By theoretical analysis, we concluded that the bands at 618.6 and 501.5 cm-1 resulted from anti-symmetric stretching vibration of Mn(IV)-O and Mn (III)-O in Li-Mn-spinel crystal (Mn(IV)O6 and Mn(III)O6 octahedron), respectively, the weak band at 1,124 cm-1 resulted from anti-symmetric stretching vibration of Li-O in the spinel (LiO4 tetrahedron), and other possible bands at wave number lower than 400 cm-1 were not detected in the range from 400 to 4,000 cm-1. The reliability of conclusions was proved by IR spectra of both the Li-Mn-spinel and doped Li-Mn-spinel.