An ultrasonic therapeutic transducers using lead-free Na _0.5K_0.5NbO₃-CuNb₂O₆ ceramics

In this work, we reports on the CuNb₂O₆ (CN) modified lead-free Na_0.5K_0.5NbO₃ (NKN) based piezoelectric ceramics were synthesized by solid-state reaction methods and sintered at 1075 °C for 3 h. A secondary phase of K₄CuNb ₈O₂₃ was found in the XRD pattern of NKN-based ceramics as the CN dopants is 1 mol%. Microstructural analyses of un-doped and CN-doped ceramics were performed in a scanning electron microscope. The influence of CN content on the microstructure, electrical properties, temperature stability, and mechanical properties of the synthesized ceramics was investigated. The results show that the synthesized ceramics with CN-doped not only had improved density but also exhibited superior piezoelectric characteristics, temperature stability of resonance frequency (TCF), and a better elastic stiffness coefficient than those of pure NKN piezoelectric ceramics. The bulk density (4.47 g/cm ³), k_p (40%), k_t (45%), Q_m (1642), C33D (19.64 × 10¹⁰ N/m²), TCF (-0.011%/°C) and TCC (0.135%/°C) values for NKN-01CN ceramics obtained from experiments show excellent 'hard' piezoelectric properties. Furthermore, a lead-free NKN-01CN ultrasonic therapeutic transducer was successfully driven by a self-tuning circuit.