Lead-free NKN-based materials for ultrasonic therapeutic transducers: Resistance to temperature and humidity

Chung Ming Weng, Cheng Che Tsai, Cheng Shong Hong, Jyh Sheen, Sheng Yuan Chu

Research output: Contribution to journalArticlepeer-review


In this study, CuF2 and LiNbO3 modified lead-free (Na, K)NbO3 (NKN)-based ceramics (NKNCF and NKLN) were synthesized using solid-state reaction methods. The influence of doping materials on the electrical properties and stability of the synthesized ceramics was then investigated. The ceramics synthesized with CuF2 and LiNbO3 dopants were of higher density than pure NKN ceramics and far more stable under the effects of temperature and humidity. NKNCF ceramics sintered at 1000C exhibited excellent “hard” piezoelectric properties (kp = 35%, kt = 45%, d33 = 88 pC/N, Qm = 2800, and tanδ = 0.1%). In contrast, NKLN ceramics sintered at 950C exhibited excellent “soft” piezoelectric properties (kp = 50%, kt = 53%, d33 = 150 pC/N, Qm = 168, and tanδ = 4%). The ceramics were then used in the fabrication of 3-MHz ultrasonic therapeutic transducers driven by a self-tuning circuit to investigate the dynamic performance. Our results clearly demonstrate that the resonance resistance, Qm, and tanδ play a more important role in the generation of acoustic power of ultrasonic therapeutic transducers than the electromechanical coupling coefficient (k). The CuF2-doped ceramics were found to easily generate a greater acoustic power, which makes them suitable for applications in therapeutic transducers.

Original languageEnglish
Pages (from-to)P733-P740
JournalECS Journal of Solid State Science and Technology
Issue number10
Publication statusPublished - 2017

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials


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