Thermally stable high strain and piezoelectric characteristics of (Li, Na, K)(Nb, Sb)O 3 ‐CaZrO 3 ceramics for piezo actuators

The 0.97(Na 0.5 K 0.5 )(Nb 1−x Sb x )O 3 ‐0.03CaZrO 3 ceramic with x = 0.09 exhibits a high d 33 of 518 pC/N and a strain of 0.13% at 4.0 kV/mm owing to its orthorhombic‐pseudocubic polymorphic phase boundary (PPB) structure. However, these values decreased considerably above 90°C owing to its low Curie temperature ( T C ), indicating that its thermal stability is not sufficient for practical applications. Li 2 O was added to the specimen with x = 0.11 to improve its thermal stability of the strain and d 33 by increasing the T C without degrading the actual d 33 and strain values. The 0.97(Li 0.04 Na 0.46 K 0.5 )(Nb 0.89 Sb 0.11 )O 3 ‐0.03CaZrO 3 ceramic, having an orthorhombic‐tetragonal PPB structure, exhibits a d 33 of 502 pC/N and a strain of 0.16%. This large strain was maintained up to 150°C and the d 33 slightly decreased to 475 pC/N at 130°C. Therefore, this lead‐free ceramic displays excellent piezoelectric characteristics with improved thermal stability, indicating that it can be applied to piezoelectric actuators.