The growth behavior and mechanism of KNN nanorods with sol-gel route

Lead-free potassium sodium niobate (KNN) nanorods were synthesized by a modified sol-gel method with freshly homemade niobium hydroxide as niobium source, oxalic acid as chelator, ethanediol as esterifying agent, rochelle salt as potassium and sodium source. The as-synthesized KNN nanorods exhibited a orthorhombic structure with diameter of 150-500 nm and length of 1-2 m. The effects of the sintering temperature and heating rate on the crystal structure and morphology were examined respectively, and the growth process and mechanism were explained. The results showed that the crystalline structure of KNN nanorods was affected by the sintering temperature significantly and that the morphology was mainly affected by the heating rate. At a low heating rate the particles tended to grow into (001) oriented nanorods, while at a rapid heating rate the particles tended to be cube-like structures. In addition, relatively low sintering temperature was beneficial to grain growth along c axis direction due to the low growth energy of c axis in the orthorhombic system.