Six NASICON‐type phosphate glasses with a wide variety of compositions (Na3M2(PO4)2F3, where M2 = V2, Ti2, Fe2, TiV, FeV, and FeTi) were synthesized using melt‐quenching and double‐crucible techniques. Their glass transition and crystallization temperatures were determined from differential thermal analysis experiments. The electrical properties were studied with impedance spectroscopy. We found that depending on temperature and composition the studied materials exhibit predominant electronic, ionic, or mixed conduction. This observation is interesting from both fundamental and application point of view (eg, in all‐solid‐state batteries). In general, the conductivity of glasses ranged from 3·10−13 to 10−10 S/cm at room temperature, with activation energies varying from 0.65 to 0.73 eV. After crystallization at 600°C, the values of conductivity noticeably increased. For nanocrystalline materials, they were between 10−11 and 10−7 S/cm (at room temperature). The values of the activation energy spread from 0.53 to 0.70 eV. Most of the glasses exhibited predominant electronic conductivity. After nanocrystallization, the ionic transference number considerably increased in almost all samples. This study proves that thermal nanocrystallization can be used to synthesize nanocrystalline NASICON‐like cathode materials for Na‐ion batteries from their glassy analogs. We believe that this method can be adopted also to other interesting sodium compounds in the future.

This study demonstrated for the first time that it is possible to prepare nanocrystalline δ-Bi2O3 that is stable at room temperature by twin-rollers and free cooling methods, using a ceramic crucible. The phase composition of prepared samples and upper limit of the thermal stability of nanograins confined in an amorphous matrix were determined by the X-ray diffraction (XRD) method. The average size of crystallites and the microstructure of studied samples was determined by SEM and XRD methods. The average grain size varied from 38 to 85 nm, depending on the preparation technique; however, it was also observed that agglomerations consisted of smaller crystallites ca. 10–30 nm. Using the EDX method, it was found that a crucial role in the preparation of nanocrystalline δ-Bi2O3 glass-ceramics was played by Si and Al impurities and their glass forming oxides from ceramic crucible. By impedance spectroscopy (IS), the temperature dependencies of electric conductivity (via oxygen ions) were studied and the activation energies of conductivity were determined.