(Na0.8K0.2)0.5Bi0.5TiO3 nanowires:: Low-temperature sol-gel-hydrothermal synthesis and densification

The sol-gel-hydrothermal processing of (Na0.8K0.2)(0.5)Bi0.5TiO3 (NKBT) nanowires as well as their densification behavior were investigated. The morphology and structure analyses indicated that the sol-gel-hydrothermal route led to the formation of phase-pure perovskite NKBT nanowires with diameters of 50-80 nm and lengths of 1.5-2 mu m, and the processing temperature was as low as 160 degrees C, but the conventional sol-gel route tended to lead to the formation of NKBT agglomerated porous structured nanopowders, and the processing temperature was higher than 650 degrees C. It is believed that the gel precursor and hydrothermal environment play an important role in the formation of the nanowires at a low temperature. Owing to the better packing efficiency and therefore a good sinterability of the freestanding nanowhiskers, the pressed pellets made by NKBT nanowires showed > 98% theoretical density at 1100 degrees C for 2 h. The sol-gel-hydrothermal-derived ceramics have typical characteristics of relaxor ferroelectrics, and the piezoelectric properties were better than the ceramics prepared by the conventional sol-gel and solid-state reaction.