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Potassium sodium niobate (KNN) powders were synthesized using a modified sol-gel method. The metal precursors used for the KNN synthesis were potassium carbonate, sodium carbonate, and niobium hydroxide. Ethylene glycol (EG) and ethylene diamine tetraacetic acid (EDTA)/citrate were used as the esterification and chelating agents, respectively. The effects of the amount of citric acid (CA), EG, and EDTA on the stability of the precursor sol were investigated. The powders and gels were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric-differential scanning calorimetry analysis. The results indicated that the stable precursor sol was formed when n(CA):n(Mn+) = 3:1, n(NH4-H2O):n(EDTA) = 1:3.5, and n(CA):n(EG) = 1:2. The xerogel was calcined at 500-950 ℃ to prepare the KNN powder. The pure perovskite phase of KNN with a cubic-like structure was synthesized at 850 ℃ from the precursor sol with the K/Na molar ratio of 1.2. The formation mechanism of the KNN perovskite phase was also discussed.