Phase-pure K0.5Na0.5NbO3 (KNN) fine powders were synthesized via a solid-state route from a homogeneous solid mixture. A colloidal dispersion comprising a mixed ethanol solution of potassium and sodium acetates and Nb2O5 fine particles was attrition milled and dried carefully to avoid water absorption. Two-step calcination in air at 450 degrees C and 625 degrees C, each for 3h, resulted in the phase-pure KNN powders. The volume-based median diameter of the final product was ca. 0.8m. Starting from the same precursors without dissolving the acetates, the phase-pure KNN was never achieved even when the two calcination temperatures were increased to 550 degrees C and 700 degrees C, in spite of the same milling conditions. Key issues of eliminating second phases were (i) starting from a wet-milled mixture with a single solution containing both of the A-site species, and (ii) repeated wet milling of the reaction mixture to disintegrate reaction-induced agglomerates. These enabled rapid nuclei growth from chemically interacted precursor prior to calcination, and short diffusion path due to repeated deagglomeration, excluding formation of off-stoichiometric second phases. All these items were confirmed by different analytical tools, among others, thermo-gravimetry and differential thermal analysis (TG-DTA), particle size analyses, and XPS at various reaction stages. On the heating stage microscope, a shrinkage onset was observed at 850 degrees C, that is, 150K lower than that of conventionally prepared KNN, that is, via a solid-state synthesis from carbonates by a two-step calcination at 800 degrees C and 750 degrees C, for 4h each. No second phase was observed after sintering up to 1100 degrees C.