Synthesis of homogeneous (Na_1-xK_x)NbO₃ nanorods using hydrothermal and post-heat treatment processes

To synthesize (Na_1-xK_x)NbO₃ nanorods, the Nb₂O₅-added (1-y)NaOH-yKOH specimens with 0.0≤y≤0.9 were heated at 160°C and subsequently annealed at 500°C. Homogeneous Na-rich (Na_1-xK_x)NbO₃ nanorods were only synthesized for the specimen with y=0.15. However, NaNbO₃ nanorods were formed for specimens with y<0.15, and K-rich (Na_1-xK_x)NbO₃ nanoplates were obtained for specimens with y>0.2. The (Na_8xK_8-8x)Nb₆O₁₉{dot operator}nH₂O transient phase was formed in the specimen with y=0.15 heated at 160°C for 8.0-12.0h, and this phase transformed into the Na-rich (Na_1-xK_x)NbO₃ nanorods after annealing at 500°C. Therefore, the formation of a homogeneous (Na_8xK_8-8x)Nb₆O₁₉{dot operator}nH₂O phase at a low temperature is very important for the synthesis of the (Na_1-xK_x)NbO₃ nanorods. The (Na_8xK_8-8x)Nb₆O₁₉{dot operator}nH₂O phase was considerably influenced by the heating temperature, and the processing time. The Na-rich (Na_1-xK_x)NbO₃ nanorods have rectangular shape with various sizes, and the growth direction of these nanorods is [001].