Structural and electrical properties of (1-x)(Na_(0.465)K_(0.465) Li_(0.07))NbO3-x CaTiO3 lead-free piezoelectric ceramics with high Curie temperature

摘要

Accompanied by the calling for the suitable development, lead-based piezoelectric ceramics will be gradually substituted by an environment-friendly of lead-free piezoelectric ceramics. Among them, alkaline niobate (Na, K)NbO3-based ceramics are more promising because of their good piezoelectric properties and high Curie temperatures. In this study, lead-free piezoelectric ceramics compositions: (1-x)(Na_(0.465)K_(0.465)Li_(0.07))NbO3-x CaTiO3 (x = 0.005, 0.01, 0.015, 0.02) were prepared by a conventional mixed oxide route, and the effects of CaTiO3 on structural and electrical properties were investigated. X-ray diffraction analysis results indicated that CaTiO3 diffuses into the (Na_(0.465)K_(0.465)Li_(0.07))NbO3 lattice to form a solid solution during sintering. The samples with x ≤ 0.01 showed the coexistence of orthorhombic and tetragonal phases. The tetragonality increased with further increasing x. Grain growth during secondary recrystallization was also affected. The dielectric and piezoelectric properties are enhanced for the composition near the orthorhombic-tetragonal polymorphotropic phase boundary. The 0.995(Na_(0.465)K_(0.465)Li_(0.07))NbO3-0.005 CaTiO3 ceramics exhibit optimum electrical properties (d_(33) = 258 pC/N, ε_r = 1014, tan 5= 0.038, and T_C= 464°C). The results reveal that (1-x)(Na_(0.465)K_(0.465)Li_(0.07))NbO3-x CaTiO3 ceramics are promising candidate materials for lead-free piezoelectric application.