Samarium modified lead-free potassium sodium niobate-based grain orientation-controlled ceramics and its ultrasonic transducer applications

Environment-friendly lead-free potassium sodium niobate-based piezoelectric materials have been widely used in acoustic device applications because of its high piezoelectric response, high Curie temperature, and low acoustic impedance. In our previous works, samarium modified 0.915(K_0.45Na_0.5Li_0.05)NbO₃-0.075BaZrO₃-0.01(Bi_0.5Na_0.5)TiO₃ (Sm-KNLN-BZ-BNT) ceramics have achieved high piezoelectric properties with good thermal stability. To further improve its properties and thermal stability, grain orientation-controlled methods have been introduced to Sm-KNLN-BZ-BNT ceramics. In this work, textured Sm-KNLN-BZ-BNT ceramics with a 93% ⟨001⟩_c-oriented textured degree have been prepared. The samples have achieved a d₃₃* value with 532 pm/V and better thermal stability between room temperature to 150 °C than the non-textured samples. Moreover, ultrasonic transducers with a 25 MHz center frequency have been designed and fabricated by the textured Sm-KNLN-BZ-BNT ceramics. The peak-to-peak of the transducers has reached a 1.78 V high level, which demonstrated the textured Sm-KNLN-BZ-BNT ceramics are a good candidate for acoustic applications.