Synthesis of potassium sodium niobate nanostructures by hydrothermal combining with the sol-gel method

•KNbO3-type orthorhombic K1−xNaxNbO3 nanowires were prepared by hydrothermal method.•Metastable K0.52Na0.48NbO3 microfingers have a morphotropic phase boundary.•Sodium dodecyl sulfate could improve the crystallinity of K0.52Na0.48NbO3 powders.•The Curie temperature of rhombohedral-tetragonal KNN was 555 °C.

In this paper the K1−xNaxNbO3(KNN) nanostructures were synthesized by hydrothermal method using KNN gel powders as precursors. KNbO3-type orthorhombic KNN nanowires and perovskite KNN microfingers with a morphotropic phase boundary (MPB) between rhombohedral and tetragonal characterized by X-ray diffraction and Raman spectroscopy were obtained at 190 °C and 220 °C, respectively. KNbO3-type orthorhombic KNN nanowires had rectangular shape and the growth direction of these nanowires was [0 0 1]. The rhombohedral-tetragonal KNN microfingers were metastable, and changed the rhombohedral-tetragonal phase into the orthorhombic phase via thermal treatment at 600 °C then cooled down to room temperature. Sodium dodecyl sulfate (SDS) as surfactant was added to the hydrothermal reaction. It was found that SDS could improve the crystallinity of the rhombohedral-tetragonal K0.52Na0.48NbO3 and reduce the impurity effectively. The tetragonal-cubic phase transition temperature (Tc) of the rhombohedral-tetragonal powders appeared at 555 °C.

Graphical abstractWe prepared novel metastable perovskite K0.52Na0.48NbO3 microstructures with a morphotropic phase boundary (MPB) between rhombohedral and tetragonal via hydrothermal method with SDS surfactant-assist.Figure optionsDownload full-size imageDownload as PowerPoint slide