Magnetic properties of mixed sodium-lithium iron fluorophosphate NaLiFePO4F cathode material

摘要

Mixed sodium-lithium iron fluorophosphates NaLiFePOsub4/subF was synthesized by solid-state route. The crystal and magnetic properties were investigated by X-ray diffraction (XRD) measurement, vibrating sample magnetometer (VSM), and M?ssbauer spectroscopy. The crystal structure of NaLiFePOsub4/subF was determined to be orthorhombic with space group of Pnma . The cell parameters of NaLiFePOsub4/subF are as follows: a sub0/sub = 10.9661 ?, b sub0/sub = 6.3693 ?, c sub0/sub = 11.4342 ?, and V = 798.6377 ?sup3/sup. The temperature-dependence of the zero-field-cooled (ZFC) and field-cooled (FC) curves was examined by VSM at 100 Oe from 4.2 to 295 K. We determined the Néel temperature ( T subN/sub = 22 K) and spin reorientation temperature ( T subS/sub = 13 K). The M?ssbauer spectra of NaLiFePOsub4/subF were taken at various temperatures ranging from 4.2 to 295 K. At below T subS/sub, the electric quadrupole splitting (Δ E subQ/sub) decreased and magnetic hyperfine field ( H subhf/sub) increased with decrease temperature due to spin-orbit coupling.