A complete study of amorphous iron phosphate structure

In-depth structural studies have been carried out on amorphous FePO ₄ prepared by two different methods, and on amorphous LiFePO ₄ prepared by electrochemical insertion of Li. The local environment of Fe in these samples was investigated using Mössbauer spectroscopy and X-ray absorption spectroscopy. X-ray and neutron diffraction and transmission electron microscopy have been applied to elucidate the first complete structural study of these materials. The Fe environment in amorphous FePO₄ was found to be similar to that in quartz FePO₄ where every Fe is surrounded by four oxygen atoms. However, the Fe environment in amorphous LiFePO₄ is affected by the appearance of Fe metal in this sample as a consequence of Li insertion. Small angle scattering measurements confirmed the presence of nm-scale internal structure in the amorphous FePO₄ prepared by thermal decomposition and in amorphous LiFePO₄.