Synthesis, growth mechanism and optical properties of (K,Na)NbO3 nanostructures

(K1-xNax)NbO3 (KNN) nanomaterials with various morphologies, including nanorods, step-like structures etc. were synthesized through a hydrothermal route. For KNN nanomaterials, the phase structures changed from orthorhombic to monoclinic as the x value increased from 0.27 to 0.66. Oriented attachment and aggregation are the major formation mechanism of the nanorods and the step-like structures, respectively. The compositional change in KNN induced a series of shifts of the Raman bands, of which the mechanisms are briefly discussed. A UV/vis absorption study shows that, for K0.50Na0.50NbO3 nanorods, two interband transitions from O-2p electron states to empty Nb-4d electron states and two intraband transitions in relation to Nb5+ cations are revealed, and the band gap is about 3.09 eV.