Structure and Stability of Sodium Intercalated Phases in Olivine FePO4

Olivine-type NaFePO4 and Na0.7FePO4 were synthesized making use of sodium batteries. Both atomic structures were obtained via Rietveld refinements of the resulting powders and were proven to be stable up to around 450°C. Olivine NaFePO4 transforms into the high-temperature stable maricite phase. Significant differences are found with LiFePO4.