Development of low band gap layered Bi₆FeNiTi₃O₁₈ aurivillius phase ceramics for ferroelectric memory and cathode for lithium-oxygen batteries applications

The layered multiferroic perovskite oxides are excellent functional materials for ferroelectric memory applications and also show application potential for cathode materials in lithium-oxygen battery due to high surface area, good stability, easy processing and low price. Synthesis of uniformly distributed layered perovskite oxides with low band gap, ionic-conducting and ferroelctric nature is still challenging. In this work, we have synthesized a new single-phase aurivillius phase Bi₆FeNiTi₃O₁₈ ceramics by high-energy ball mill mechano-chemical reaction. The Rietveld refinement of XRD data reveals that the compound Bi₆FeNiTi₃O₁₈ shows orthorhombic structure with space group P2/m and SEM images confirm the uniform layered morphology. Bi₆FeNi Ti₃O₁₈ ceramic have shown very high T_c of 450 °C and typical relaxor behaviour. Impedance analysis reveals the effect of grains, grain boundaries and electrode on conductivity. Ferroelectric nature is confirmed by obtained P-E loop at room temperature. We also report much lower band gap (E_g = 1.87 eV) as compared to Bi₆Fe₂Ti₃O₁₈ (E_g = 3.2 eV) ceramics which is due to Ni 3d state formation below Fe 3d state. The present work provide new path to engineer the functional properties of perovskite oxides for memory and energy storage applications.