<p>Potassium sodium niobate, i.e., K_0.5Na_0.5NbO₃ or KNN, is an important lead (Pb)-free, perovskite-structured, piezoelectric ceramic composition. KNN is typically synthesized by solid-state reaction of the unary alkali carbonates, i.e., K₂CO₃ and Na₂CO₃, with Nb₂O₅ at high temperatures. It is well known that this reaction can result in chemically inhomogeneous powders and ceramics, which can have deleterious effects on key physical properties. In this work, we demonstrate that substantial improvements in chemical homogeneity of KNN are achieved by initially pre-reacting the unary carbonates to form the binary carbonate KNaCO₃, and then subsequently reacting KNaCO₃ with Nb₂O₅ to form KNN. The binary carbonate, KNaCO₃, is a distinct compound with a unique structure relative to the unary carbonates. In contrast with the unary carbonates, the consumption of KNaCO₃ during the reaction to form KNN facilitates the balanced incorporation of K⁺ and Na⁺ into the growing KNN phase, leading to improved chemical homogeneity. Key methods include in situ X-ray diffraction (XRD) during thermal treatment, scaled-up batch processing in a muffle furnace, and Williamson–Hall analysis of XRD patterns to determine changes in microstrain due to chemical homogeneity.</p>