The structural properties of microcrystalline LiFePO 4 prepared with and without carbon coating are analyzed with X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and magnetic measurements for comparison. While nanosized ferromagnetic particles ͑␥-Fe 2 O 3 clusters͒ are evidenced from magnetic measurements in samples without carbon coating, such ferromagnetic clusters just do not exist in the carbon-coated sample. Ferromagnetic resonance experiments are a probe of the ␥-Fe 2 O 3 nanoparticles, and magnetization measurements as well, allowing for a quantitative estimate of the amount of Fe 3+ . While the fraction of iron in the Fe 3+ configuration rises to 0.18% ͑in the form of ␥-Fe 2 O 3 nanoparticles͒ in the carbon-free sample, this fraction falls to a residual impurity concentration in the carbon-coated sample. Structural properties show that the carbon does not penetrate inside the LiFePO 4 particles but has been very efficient in the reduction of Fe 3+ , preventing the ␥-Fe 2 O 3 clustering thus pointing out a gas phase reduction process. The carbon deposit characterized by Raman spectroscopy is an amorphous graphite deposit hydrogenated with a very small H/C ratio, with the same Raman characteristics as a-C carbon films obtained by pyrolysis technique at pyrolysis temperature 830 ± 30°C. The impact of the carbon coating on the electrochemical properties is also reported.

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