**4. Conclusions**

Based on a modified dice-and-fill technique, a PIN-PMN-PT single crystal 1-3 composite with high piezoelectric constant (d33 = 1500 pC/N), high electromechanical coefficient (kt = 0.81), and low acoustic impedance (16.2 Mrayls) was prepared. Utilizing this kind of composite, a 20 MHz 48-element side-looking high frequency phased array with central frequency of 20 MHz and −6 dB bandwidth of 77% was successfully fabricated, which was confirmed by the electric impedance resonance curve and the pulse-echo response. Of particular significance was that this PIN-PMN-PT single crystal 1-3 composite-based phased array exhibits a superior insertion loss compared with PMN-PT single crystal and PZT-5H-based 20 MHz phased arrays. The focusing and steering capabilities of the obtained phased array were demonstrated theoretically and experimentally. Furthermore, when using such a phased array, wire phantom images in water and PDMS can be achieved. These promising results sugges<sup>t</sup> that the PIN-PMN-PT single crystal 1-3 composite-based high frequency phased array is competent for biomedical ultrasound imaging in the future.

**Author Contributions:** B.Z. and D.W. conceived and designed the experiments; W.Z. and T.Z. performed the experiments; J.O.-Y. and X.Y. analyzed the data; W.Z. and T.Z. wrote the paper. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Natural Science Foundation of China (Grant no. 11774117), and the Excellent Youth Foundation of Hubei Province (2018CFA083). We thank the Analytical and Testing Center of Huazhong University of Science & Technology.

**Conflicts of Interest:** The authors declare no conflict of interest.
