Sodium–potassium–niobate based piezoelectric ceramics: processing—microstructure—properties

Abstract Sodium potassium niobate (KNN) and KNN-based ceramics are considered viable alternatives to lead-based piezoelectric ceramics. Their chemical composition is the key to their phase transitional behaviour, which determines their functional properties. On the other hand, the microstructure is another factor that crucially contributes to shaping the properties of ceramics. The review addresses the synthesis of the perovskite solid solution as well as the issue of chemical homogeneity depending on the choice of the reagents. In sintering, the importance of stoichiometry in densification and microstructure evolution is discussed. Phase boundary engineering, which has been effective in tailoring the functional response of KNN-based ceramics, is discussed from the viewpoint of material chemistry and processing that may contribute to chemical homogeneity. Finally, consolidation approaches with a lower thermal budget are addressed.