锂锰尖晶石红外光谱的研究

本文对锂锰尖晶石的红外光谱进行了研究。由于锂锰尖晶石的晶体结构属于Fd3m空间群,锂离子占据四面体空隙(8a位置),锰离子占据八面体空隙(16d位置)。根据群论的知识,对锂锰尖晶石晶体中离子的振动方式与红外活性之间的内在关系进行了讨论。并列出了锂锰尖晶石的红外光谱实验数据。通过理论分析,我们推断:位于618.6和501.5cm~(-1)的红外吸收带分别来源于Mn(Ⅳ)-O和Mn(Ⅲ)-O键在晶体中的不对称伸缩振动(单元为Mn(Ⅳ)O_6和Mn(Ⅲ)O_6八面体),位于1124cm~(-1)的弱红外吸收带来源于Li-O键的不对称伸缩(单元为LiO_4四面体)。还有一些低于400cm~(-1)的可能吸收带在400～4000cm~(-1)范围内未能检测到。这一结论的可靠性通过锂锰尖晶石和掺杂的锂锰尖晶石的红外光谱实验数据得到证实。

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.