KxNa1-xNbO3 (0 0.5) was obtained from 8 M total hydroxide concentration after 6 h of reaction at 200 °C. Rietveld refinement of the XRD data revealed that all samples exhibited the secondary NaNbO3 phase. However, the lowest amount (3.74 vol%) was obtained for 24 h of reaction under 10 M alkaline solution. After 3 h of reaction, dodecahedra shaped hexaniobate phase (KxNa8-xNb6O19.nH2O) was observed. Those structures were, subsequently, replaced by ~3 μm cube shaped KNN crystals, obtained under 10 M reaction in 24 h time period.
