Fast synthesis of NaNbO3 and K0.5Na0.5NbO3 by microwave hydrothermal method

Synthesis of sodium and potassium–sodium niobates (NaNbO3 and K0.5Na0.5NbO3) was achieved by reducing the reaction time via microwave-assisted hydrothermal route. Sodium niobate was synthesized at 180 °C for 15 min using NaOH 6 M. During the synthesis of KNN at 180 °C, the K4Na4Nb6O19–9H2O intermediate phase appeared. By increasing the temperature to 200 and 220 °C, the pure KNN phase was obtained. Potassium–sodium niobate was prepared at 220 °C for 15 min using KOH/NaOH 8 and 10 M. These results were confirmed by X-ray diffraction, Scanning Electron Microscopy and Raman spectroscopy. The NaNbO3 and K0.5Na0.5NbO3 powders consisted of agglomerated pseudo-cubic crystals.