Citrate-Gel Synthesis of Lithium Sodium Niobate Nano-Crystalline Powder: Phase Formation and Morphology Studies

摘要

The MPB composition, Na_(0.88)Li_(0.12)NbO_3 (commonly known as LNN-12) has been synthesized by adopting recently developed low-cost citrate-gel route where Nb_2O_5 acts as a source of Nb. During synthesis, Nb_2O_5 transforms into a stable and soluble chelate complex, an alternative of expensive metal alkoxides. Thermal decomposition process and phase formation of the as prepared gel were studied using thermo-gravimetry (TG) and X-ray diffractometry (XRD). The gels were calcined in the temperature range 500-800℃ and a pure perovskite phase was obtained at 700℃, which is 200℃ below the conventional ceramics route (900℃). Morphology of the phase pure powders was characterized using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The compacted samples showed high sintered density at < 1200℃. This has been attributed to small particle size and homogeneity. The lower sintering temperature eliminates the possibility of alkali elements loss, leading to exact MPB composition and enhancement in the electrical properties.