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

The MPB composition, Na0.88Li0.12NbO3 (commonly known as LNN-12) has been synthesized by adopting recently developed low-cost citrate-gel route where Nb2O5 acts as a source of Nb. During synthesis, Nb2O5 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 degrees C and a pure perovskite phase was obtained at 700 degrees C, which is 200 degrees C below the conventional ceramics route (900 degrees C). 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 degrees C. 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.