High Frequency Transducer Based on Ultrathin Li Doped (K0.45Na0.55)NbO3Single Crystal for 80MHz Intravascular Ultrasound and Photoacoustic Imaging

The successful preparation of <001> -orientated (K
0.45
Na
0.55
)
0.96
Li
0.04
NbO
3
(KNLN)single crystal thick film with a thickness of approximately 28μ m is achieved. This lead free film maintains superior piezoelectric constant
$(d_{33}\sim 490\text{pm}/\text{V})$
and electromechanical coupling factor
$(k_{t}\sim 0.55)$
. Using such thick film, a tiny side-looking high-frequency ultrasound transducer with a central frequency of 82MHz and a bandwidth of 57.3% at −6dB is fabricated. Most importantly, 80MHz intravascular ultrasound and photoacoustic images of the rabbit aorta are presented. These promising results indicate that KNN-based lead free piezoelectric single crystal thick film is a good candidate to substitute lead-based piezoelectric layers for ultrasound applications in the future.