Effects of heat treatment on Na-ion conductivity and conduction pathways of fluorphosphate glass-ceramics

Fluorphosphate glass-ceramics Na2O-NaF-B2O3-P2O5-TiO2-ZrO2 (NTBPZ) were prepared by the conventional melt-quenching method following with the reheat treatment. High temperature phases of NaTi2(PO4)3, Na2HPO4 and Na2HPO4(H2O)2 nanocrystals were precipitated in the glass-ceramics. The influence of crystallization conditions on structure and ionic conductivity of the glass-ceramics was studied using X-ray diffraction, scanning electron microscope, and Electrochemical impedance spectra (EIS). And the results showed that the Na-ion mobility closely depends on the type and the distribution of the nanocrystal conductors. A room-temperature conductivity as high as 5.52 × 10− 5 S/cm was achieved for the glass-ceramic crystallized at 600 °C for 20 h. The effects of the heat treatment on Na-ion conduction pathways were also discussed.