Spectroscopic studies of LixFePO4 and LixM0.03Fe0.97PO4 (M=Cr,Cu,Al,Ti) -: art. no. 024105

Mossbauer and Raman measurements for LixFePO4 and LixM0.03Fe0.97PO4 (M=Cr,Cu,Al,Ti) were performed. The results for the Li0.11FePO4 oxide require an unknown additional contribution, besides the high-spin Fe2+ doublet and the high-spin Fe3+ doublet, for the Mossbauer profile to be properly accounted for. The corresponding Raman scattering suggests a two-phase material and an additional disordered structure present in the mixture. The Mossbauer-transformed patterns indicate the unknown doublet to be due to a disordered phase also. In addition, the observation of a high amount of Fe2+ sites for the low-lithium-content LixM0.03Fe0.97PO4 oxides is analyzed on the basis of the electronic charge configuration of the Li-lacking octahedral units to suffer small changes upon lithium extraction.