10F-4 Self-Focused 1-3 Composite LiNbO3 Single Element Transducers for High Frequency HIFU Applications

In this paper it is shown that LiNbO₃ single crystal may be used as a piezoelectric material for high frequency high intensity focused ultrasound (HIFU) applications for its high Curie temperature and low dielectric constant and superior mechanical properties. Simulation results show that LiNbO₃ with a 1-3 composite structure is suitable to make large aperture (diameter 22-24 mm) and high frequency (> 10 MHz) single element transducer with desired impedance and required sustainable driving voltage for the expected acoustic intensity in the focal zone. Prototype transducers with the diameter of 23 mm and a surface curvature designed for f#/l were designed and fabricated. The results are in good agreement with KLM model calculation. The measurement results show that center frequency is 10.5 MHz with the fractional bandwidth larger than 60%. The -6 dB lateral and the axial beam widths were measured by a needle hydrophone and they are 160 mum and 98 mum respectively, which are also in good agreement with theory (147 mum and 83 mum).