Microstructure and electrical properties of NaNbO3-BaTiO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (1 − x) NaNbO3-xBaTiO₃ have been fabricated by a traditional ceramic sintering technique. The effects of BaTiO₃ (BT) synthesized by hydrothermal method on crystal structure, density, dielectric, piezoelectric, and electromechanical properties were investigated. Results show that the phase structure transforms from the orthorhombic phase to the tetragonal phase with the increase of the content of BT, and the two phases co-exist when 0.08<×⩽0.10. However, the optimum composition for (1 − x)NaNbO₃-xBaTiO₃ ceramics is 0.90NaNbO₃-0.10BaTiO₃. The 0.90NaNbO₃-0.10BaTiO₃ ceramics sintered at 1250°C have higher properties: piezoelectric constant d ₃₃ of 120 pC/N, dielectric constant ε_τ of 718, planar electromechanical coupling factor k _p of 24%, planar frequency N _d of 3 MHz·mm, and the mechanical quality factor Q _m of 138, respectively. The results show that the (1−x)NaNbO₃-xBaTiO₃ ceramics is one of the promising lead-free materials for high-frequency applications.