We report precursor-based methods for low-temperature synthesis of two structure modifications of NaMnPO₄. The maricite phase is thermodynamically more stable, while the olivine phase is of great interest as a positive-electrode material for lithium and sodium ion batteries. The advantage of synthetic procedures is the formation of defectless NaMnPO₄ in the temperature range of 200–400 °C. The structure and morphology characterizations of two modifications are performed by powder XRD, SEM and TEM analyses. The oxidation state of the Mn ions in NaMnPO₄ is determined by X-ray photoelectron spectroscopy. The local environment of Na in both structure modifications is assessed by ²³Na MAS NMR spectroscopy. The synthesis methods are based on the formation of appropriate precursors that are easily transformed to target NaMnPO₄. Thermal decomposition of freeze-dried phosphate–formate precursor yields NaMnPO₄ with a maricite structure at 400 °C. KMnPO₄·H₂O with a dittmarite-type structure acts as a structure-template precursor for the preparation of NaMnPO₄ with an olivine structure by an ion exchange reaction. Both olivine and maricite NaMnPO₄ do not accommodate any anti-site mixing and Na,Mn deficiency. The morphology of NaMnPO₄ consists of nano-sized particles (less than 50 nm) that are closely bound together into aggregates, the shape of the aggregates being dependent on the synthesis procedure used.

The study demonstrates unusual capabilities of phospho-olivine NaMnPO ₄ to intercalate lithium and sodium reversibly, which makes it attractive electrode material instead of the conventional lithium analogue LiMnPO ₄ .