Structural variation of hydrothermally synthesized KNbO3 nanowires

KNbO3 (KN) nanowires were synthesized using various process conditions and their structures and morphologies were investigated. Homogeneous KN nanowires were formed in specimens synthesized at 130 °C for 24.0–48.0 h. These KN nanowires have a tetragonal structure that is known to be stable at high temperatures in the range of 225–435 °C. Tetragonal KN nanowires changed to orthorhombic KN nanoplates when the process time increased and homogeneous orthorhombic KN nanoplates existed for specimens synthesized for 144.0 h. In addition, tetragonal and orthorhombic structures coexisted in KN nanoplates synthesized at 130 °C for 72.0 h. For specimens synthesized at 100 °C, a long process time of 144.0 h was required to develop homogeneous KN nanowires that were also considered to have both tetragonal and orthorhombic structures. On the other hand, for specimens synthesized at 150 °C for 8.0 h, KN nanowires and a cube-shaped KN phase coexisted. Furthermore, a K4Nb6O17 second phase was formed in specimens synthesized for short periods of time (<8.0 h), indicating that the formation of homogeneous KN nanowires is difficult at 150 °C. Therefore, homogeneous KN nanowires with a tetragonal structure can be obtained at a low temperature of 130 °C with a short process time in the range of 24.0–48.0 h.