Phase transition and morphology evolution of superfine NaNbO3 particles synthesized by the hydrothermal method with the assistance of K+

NaNbO3 (NN) is a well-known perovskite-type dielectric material. However, its phase transition is a complex process and the phase transition mechanism is insufficiently investigated yet. Therefore, in the work, the NN superfine particles were synthesized by a hydrothermal method with the assistance of K+ and the microstructures of NN were carefully investigated to understand the strain-driven phase transition and morphology evolution of NN. The results suggest that K+ leads to strong planar bending of NbO6 by influencing the Na + vibration, which accounts for the O-R phase transition as the K+ increases. Once the R phase is triggered, the O-R phase transition proceeds spontaneously based on phonon calculations of orthorhombic (O) NN and R NN. The antiferroelectric nature of rhombohedral (R) NN with the space group R–3H is confirmed through charge density distribution. Additionally, the morphology evolution is deduced on the TEM analysis basis.