Lead-Free KNN-Based Textured Ceramics for High-Frequency Ultrasonic Transducer Application
Yi Quan, Chunlong Fei, Wei Ren, Lingyan Wang, Gang Niu, Jinyan Zhao, Jian Zhuang, Junshan Zhang, Kun Zheng, Pengfei Lin, Xinhao Sun, Qiang Chen, Zuo‐Guang Ye, Tomoaki Karaki
Abstract
Environment-friendly lead-free piezoelectric materials with excellent piezoelectric properties are needed for high-frequency ultrasonic transducer applications. Recently, lead-free 0.915(K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.45</sub> Na <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Li <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.05</sub> )NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -0.075BaZrO 3-0.01(Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Na <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> )TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (KNLN-BZ-BNT) textured piezo- electric ceramics have high piezoelectric response, superior thermal stability, and excellent fatigue resistance, which are promising for devices applications. In this work, the KNLN-BZ-BNT textured ceramics were prepared by the tape-casting method. Microstructural morphology, phase transition, and electrical properties of KNLN-BZ-BNT textured ceramics were investigated. High-frequency needle-type ultrasonic transducers were designed and fabricated with these textured ceramics. The tightly focused transducers have a center frequency higher than 80 MHz and a -6-dB fractional bandwidth of 52%. Such transducers were built for an f-number close to 1, and the desired focal depth was achieved by press-focusing technology associated with a set of customer design fixture. Its lateral resolution was better than 90 μm by scanning a 15- μm tungsten wire target. These promising results demonstrate that the lead-free KNLN-BZ-BNT textured ceramic is a good candidate for high-frequency ultrasonic transducer applications.