[20a-W833-1~9] 9.1 Dielectrics, ferroelectrics

[20a-W833-8] Materials Design for Piezoelectric Ceramics from Viewpoints of Elastic Constants

〇Toshio Ogawa¹, Taiki Ikegaya¹ (1.Shizuoka Inst. Sci. & Tech.)

Keywords:piezoelectric ceramics,elastic constants,sound velocities

Sound velocities were evaluated in ceramic disks composed of lead-containing and lead-free ceramics using an ultrasonic precision thickness gauge with high-frequency pulse generation, and furthermore, dielectric and piezoelectric constants were simultaneously measured utilizing the same disk samples. Calculating elastic constants by using the sound velocities, higher piezoelectricity in ceramics were obtained in lower Young’s modulus and rigidity, and furthermore, higher Poisson’s ratio and bulk modulus. Piezoelectric ceramics with lower Young’s modulus and rigidity caused by ferroelectric domain alignment while DC poling were easy to deform by electric field and external force. In addition to these phenomena, higher bulk modulus needs to realize higher Poisson’s ratio. Lower Young’s modulus means mechanical soft in ceramics; however, higher bulk modulus, which means mechanical hard in ceramics, need to obtain higher piezoelectricity. It was thought that these characteristics run counter to the mechanical characteristics of piezoelectric ceramics; however, it was the origin of piezoelectricity in ceramics.