Optimal Bi₀.₈Ba₀.₂FeO₃ doping in Bi₀.₅(Na₀.₇₇K₀.₂₀Li₀.₀₃)₀.₅TiO₃ multiferroic ceramics synthesized by the solid-state combustion technique

Abstract

(1-x)Bi<inf>0.5</inf>(Na<inf>0.77</inf>K<inf>0.20</inf>Li<inf>0.03</inf>)<inf>0.5</inf>TiO<inf>3</inf>-xBi<inf>0.8</inf>Ba<inf>0.2</inf>FeO<inf>3</inf> ((1-x)BNKLT-xBBF) ceramics with x = 0-0.4 were synthesized by the solid-state combustion technique. X-ray diffraction (XRD) analysis confirmed a pure perovskite structure with coexisting rhombohedral and tetragonal phases. Rietveld refinement revealed that the unit cell volume increased with increased x due to the substitution of smaller Bi³⁺ and Ti⁴⁺ ions by larger Ba²⁺ and Fe³⁺ ions at the A- and B-sites, respectively. The average grain size and measured density also increased with increasing x, while the resistivity decreased. At room temperature, (1-x)BNKLT-xBBF ceramics with x = 0.2–0.4 exhibited multiferroic behavior, characterized by ferroelectric and ferromagnetic hysteresis loops. The 0.8BNKLT-0.2BBF ceramic exhibited the most favorable properties, including: the highest relative density (95.48%), the highest dielectric constant and low dielectric loss at room temperature (ε<inf>R</inf> = 1746 and tan δ<inf>R</inf> = 0.0296), good ferroelectric properties (P<inf>r</inf>=6.46 µC/cm² and E<inf>c</inf>=11.84 kV/cm) and good ferromagnetic properties (M<inf>r</inf>=0.002 emu/g, H<inf>c</inf>=110 Oe and α<inf>E</inf> = 1.092 mV/Oe·cm). These results indicate that 0.8BNKLT-0.2BBF has the potential for applications in lead-free, room temperature multiferroic applications.