Electronic and atomic structures of interfaces between TiN coatings and Al2O3–WC composites were investigated by Density functional theory (DFT) calculations. As typical examples, interfacial orientation relationships of TiN(001)/Al2O3(0001), TiN(001)/WC(0001), TiN(111)/Al2O3(0001), and TiN(111)/WC(0001) were chosen. It was found that the TiN(111)/Al2O3(0001) and TiN(111)/WC(0001) interfaces have interfacial structural units of six‐fold coordinated triangular prisms centered on Ti atoms. In contrast, those of the interfaces with TiN(001) tend to have more distorted structure units due to their larger lattice misfits. Theoretical works of separation showed that interfacial strength is much more increased at the TiN(111) interfaces, as compared to those at the TiN(001) interfaces. Accordingly, experimental controls of TiN‐coating orientations on Al2O3–WC composites were attempted by using the cathodic arc ion plating method. It was found that orientations of (111) in the TiN coatings can be more enhanced and then interfacial mechanical strengths and hardnesses of the TiN coatings can increase more with rising bias voltages.

Mn-added (K,Na)NbO 3 -based composite lead-free piezoelectric ceramic containing KTiNbO 5 phase was fabricated for potential application to high-power fields. The resulting (K,Na)NbO 3 -based composite ceramic with 2 mol % MnO 2 exhibited piezoelectric properties (mechanical quality factor Q m = 650, piezoelectric constantT /¾ 0 = 750, dielectric loss tan ¤ = 0.5 %), and adequate heat resistance (Curie temperature T c = 320 °C). It exhibited an internal electric field, as indicated by a shift of the polarizationelectric field hysteresis loop in the direction of the electric field. High-power characteristics of bolt-clamped Langevin transducers prepared using the (K,Na)NbO 3 -based composite ceramic was superior to those of a Pb(Zr,Ti)O 3 ceramic at a vibration velocity under high input voltage. The (K,Na)NbO 3 -based composite ceramic has good high-power properties and adequate heat resistance, dense microstructure, and process stability, and is considered to be a promising candidates as lead-free piezoelectric ceramics for high-power devices, such as ultrasonic motors, transformers, and transducers.