Utilization of Nonstoichiometric Nb 5+ to Optimize Comprehensive Electrical Properties of KNN-Based Ceramics.

An easy approach is suggested to obtain excellent piezoelectric performances in potassium sodium niobate (KNN)-based ceramics simultaneously with low dielectric loss (tanδ), high Curie temperature ( T C ), and electromechanical coupling factor ( k p ). Herein, a KNN-based ceramics system with nonstoichiometric Nb 5+ is designed. Excessive Nb 5+ occupying the B-site significantly influences the microstructural features and electrical properties of KNN-based ceramics. Furthermore, the excessive Nb 5+ improves the temperature stability of ceramics by providing the domain wall pegging effect and defect dipole. A high T C = 300 °C, large k p = 0.516, and d 33 = 450 pC/N can be simultaneously obtained in the KNN-based ceramics with nonstoichiometric Nb 5+ . These results confirm that the comprehensive electrical properties of KNN-based ceramics can be tuned by optimizing the content of nonstoichiometric Nb 5+ .