Evaluation of NaFeTiO4 as an electrode for energy storage application.

We report a polycrystalline NaFeTiO₄ prepared via conventional solid-state reaction route. X-ray diffraction (XRD) results and Rietveld refinement confirmed single-phase NaFeTiO₄ having an orthorhombic unit cell with lattice parameters <italic>a</italic> = 9.17051 Å, <italic>b</italic> = 2.96310 Å, and <italic>c</italic> = 10.73676 Å and Pnma space group (No. 62). Energy dispersive spectrum (EDS) yielded sample stoichiometry that agrees well with its molecular formula. The surface morphology indicated a cylindrical rod-like microstructure comprising well-defined grains having variable dimension, i.e., diameter ~ 250 to 350 nm and length ~ 1 to 5 μm. Vibrational spectroscopy (FTIR/Raman) results indicated presence of FeO₆ and TiO₆ octahedra in good agreement with crystallographic study. Brunner-Emmet-Teller (BET) surface area measurement yielded a specific surface area as high as ~ 4.28 m² g⁻¹. Electrical impedance spectrum indicated presence of grains separated by well-defined grain boundaries in agreement with microstructural analysis. Electrical conductivity of the material was estimated to be ~ 6.05 × 10⁻⁶ S cm⁻¹. The structural model obtained using XRD and vibrational spectrum results suggest layered tunnel/cage structure of cage dimension ~ 4.65 Å, along [010] direction in the <italic>xz</italic> plane, which is larger than the size of Na⁺ ion (0.98 Å). So, easier Na⁺ migration feasibility exists in NaFeTiO₄ crystal lattice making it a good candidate for electrode applications. [ABSTRACT FROM AUTHOR]