Eco-Friendly Highly Sensitive Transducers Based on a New KNN-NTK-FM Lead-Free Piezoelectric Ceramic for High-Frequency Biomedical Ultrasonic Imaging Applications. - Ruimin Chen; Laiming Jiang; Tianfu Zhang; Takayuki Matsuok; Masato Yamazaki; Xuejun Qian; Gengxi Lu; Ahmad Safari; Jianguo Zhu 004; K. Kirk Shung; Teng Ma 004; Qifa Zhou (IEEE Trans. Biomed. Eng., 2019)