Mössbauer Spectral Studies of Iron Phosphate Containing Minerals and Compounds

This chapter presents a detailed discussion of the Mössbauer spectra of iron phosphate containing compounds and minerals – compounds that are increasingly important in understanding the use of lithium-ion phosphate in battery materials. An extensive discussion of the thermodynamic stability of these compounds and minerals is followed by several in-depth crystallographic studies of the various structural polymorphs of FePO 4 . Then, the paramagnetic and magnetically ordered structures and Mössbauer spectra of α -FePO 4 , γ -FePO 4 , ζ -FePO 4 , several metastable polymorphs of FePO 4 , and the crystallographic structures of two polymorphs of FePO 4 · 2H 2 O are discussed. The Mössbauer spectral properties of various oxides of iron phosphate compounds and minerals, including their temperature and pressure spectral dependence of α -FePO 4 , α -Fe 2 (PO 4 )O, Fe 3 (PO 4 )O 3 , Fe 9 (PO 4 )O 8 , α -Fe 2 (PO 4 ), and Fe 9 (PO 4 )O are covered in detail. Finally, the Mössbauer spectral discussion covers some of the difficulties encountered in the analysis of magnetic spectra; particularly, the confusion between quadrupole interaction, quadrupole shift, and quadrupole splitting in the analysis of magnetic spectra is illustrated in the case of η -Fe 0.9 Mn 0.1 PO 4 .