Ichihashi Kentaro, Tsukamura Kazutoshi, Kimura Takeshi, Kasashima Takashi, Yamazaki Masato
IEEE Trans Ultrason Ferroelectr Freq Control. 2024 Jan;71(1):46-55. doi: 10.1109/TUFFC.2023.3311442. Epub 2024 Jan 9.
By designing a unimorph suitable for the material properties of (K, Na)NbO3-based lead-free piezoelectric ceramics (KNN), we have developed a piezoelectric sounder with a sound pressure level that is superior to that of similar devices based on Pb(Zr, Ti) [Formula: see text] (PZT) over a wide temperature range. The KNN ceramics used in this work have two disadvantages: their piezoelectric constant, d , at room temperature is less than 80% of that of PZT, and their piezoelectric properties deteriorate because of phase transitions to the orthorhombic phase at low temperatures. The former issue was alleviated via design of a thin-layer unimorph that uses the specific mechanical properties of KNN, i.e., a large Young's modulus and low specific gravity when compared with the corresponding properties of PZT; a unimorph was then fabricated with both a vibration velocity and a resonance frequency that are comparable to those of PZT unimorphs. The latter issue was then resolved by reducing the resonance frequency of the unimorph relative to the acoustic resonance frequency of the resonator, which produced a stronger vibration-acoustic coupling effect within the temperature range in which the piezoelectric properties of KNN are lower. The KNN sounder designed in this manner exhibited a sound pressure level that was 1.4 dB greater than that of a PZT sounder at room temperature, and the range of change in the sound pressure level from -20 °C to 90 °C was 2 dB less than that for the PZT sounder.
通过设计一种适合（K，Na）NbO₃基无铅压电陶瓷（KNN）材料特性的单压电片，我们开发了一种压电发声器，其声压级在很宽的温度范围内优于基于Pb（Zr，Ti）O₃（PZT）的类似器件。本工作中使用的KNN陶瓷有两个缺点：其室温下的压电常数d小于PZT的80%，并且由于在低温下向正交相的相变，其压电性能会恶化。通过设计一种利用KNN特定机械性能的薄层单压电片，即与PZT的相应性能相比具有大的杨氏模量和低的比重，缓解了前一个问题；然后制造出一种振动速度和共振频率与PZT单压电片相当的单压电片。通过相对于谐振器的声共振频率降低单压电片的共振频率，解决了后一个问题，这在KNN压电性能较低的温度范围内产生了更强的振动 - 声耦合效应。以这种方式设计的KNN发声器在室温下的声压级比PZT发声器高1.4 dB，并且从 -20°C到90°C声压级的变化范围比PZT发声器小2 dB。
