报告人：Tomoaki Karaki

单位：Toyama Prefectural University, Japan

报告时间：2026年5月29日（星期五）上午4:00

报告地点：知新楼C座709

邀请人：王春明

个人简介：

Professor Tomoaki Karaki earned his Ph.D. in Electrical Engineering from Kyoto University, Japan. Since joining Toyama Prefectural University, his research has centered on single-crystal growth and the preparation of ceramics and films for piezoelectric, dielectric, and ferroelectric applications. His current research interests encompass: alternating current poling (ACP) of relaxor-PbTiO₃ piezoelectric single crystals; development of lead-free piezoceramics; growth of piezoelectric and ferroelectric single crystals; simulation of multilayer SAW devices; characterization of acoustic-wave-related physical constants in piezoelectric single crystals; hydrothermal synthesis of nanocrystals and plate-like particles; and ultrasonic transducer research, with an emphasis on ultrasonic stimulation for farmed fish, small mammals, and humans.

报告摘要：

Wireless communication technology has evolved rapidly, and the communications industry has experienced huge leaps from 2G, 3G, 4G to 5G, and is moving towards 6G. Frequency filters based on piezoelectric materials directly determine the operating frequency band and bandwidth of the communication equipment, and plays a pivotal role in the communication devices. In this lecture, the operating frequencies and principles from SAW (surface acoustic wave) to XBAR (transverse-electric-field excited bulk acoustic wave resonator) and the requirements for piezoelectric materials will be introduced.

The propagating speed of SAW of piezoelectric materials is less than 5000 m/s. Because the width of the (interdigital transducer) IDT electrode is limited about 0.5 m, the maximum operating frequency of the SAW is less than 2.5 GHz. To increase the frequency, IHP SAW (incredible high performance SAW)，in which a piezoelectric film is prepared on a substrate with high acoustic speed, has been realized. In this case, the operating frequency has been increased to 3.5 GHz.

With the improvement of piezoelectric film preparation technology and precise control of film thickness, a SMR-BAW (solidly mounted resonator bulk acoustic wave) utilizing piezoelectric material thickness vibration has been proposed. The operating frequency of SMR-BAW is increased to 6 GHz. The FBAR (film bulk acoustic resonator), which also utilizes the vibration of material thickness, is also mentioned in a wide range of applications. The operating frequency of FBAR is increased to 7 GHz.

The XBAR based on Lamb wave is newly proposed for applications around 8 GHz. The Lamb wave is one of the FPWs (flexural plate waves) mixed with a longitudinal wave (P, primary wave) and a vertically-polarized shear wave (SV) propagating in a thin plate. Smart Cut^TM technology (He⁺ cutting) has been developed for the fabrication of high quality LiTaO₃ and LiNbO₃ single crystal thin films, so called POI (piezo-on-insulator) substrates. This technology allows the manufacturing of high performance, integrated XBAR filter components that can meet the requirements of 5G and/or 6G in smartphone front-end modules.