Broadband ultrasonic transducer based on textured lead-free NKN-based piezoceramics

The performance of ultrasonic transducers in terms of broadband and high sensitivity is crucial for achieving excellent axial resolution and a high signal-to-noise ratio in ultrasonic imaging. These qualities greatly rely on the electromechanical properties of the piezo-materials used. In this work, a potassium sodium niobate (NKN)-based lead-free piezoceramic was fabricated by template grain growth method, resulting in outstanding electromechanical properties (d₃₃ ≈ 710 pC N⁻¹, k₃₃ ≈ 0.88, k_t ≈ 0.61, T_c ≈ 244 °C). A 1–3 composite structure was created using this lead-free textured ceramic to fabricate an ultrasonic transducer with a center frequency of 4.18 MHz. The ultrasonic transducer exhibited a remarkable −6 dB bandwidth of up to 140% and an insertion loss of −23.63 dB. Imaging experiments confirmed that the 1–3 NKN-based textured ceramic transducer displayed excellent −6 dB axial resolution. Notably, these performance parameters exceeded those of ultrasonic transducers made with lead-based PZT-5H piezoceramics, demonstrating the significant potential of this lead-free piezoceramic as a replacement for lead-based materials.