Theoretical design and experimental study of hydrothermal synthesis of KNbO3

In the framework of the Lencka–Riman thermodynamic model, we give a theoretical design for the hydrothermal synthesis of pure KNbO3 powder in a K–Nb–O tri-component system, where the stability yield diagrams and the optimum conditions (i.e., synthesis temperature, precursor concentrations, solution pH) are provided. Additionally, a hydrothermal experiment is carried out to synthesize KNbO3 powder by reacting niobium pentoxide with potassium hydroxide at a temperature above 523 K and highly alkaline conditions. It is found that the experiment is in great agreement with the theoretical design. This research shows that the newly developed Lencka–Riman model is a powerful theoretical tool for designing hydrothermal synthesis of new materials.