Vibrating Piezoelectric Energy Conversion Efficiency of Sol-Gel PZT Films with Various Crystal Orientations on MEMS Buckled Diaphragm Structures

• Main Authors: Yamashita, Kaoru, Nakajima, Shota, Shiomi, Jo, Noda, Minoru, Muralt, Paul
• Format: Conference Proceeding
• Language: English
• Subjects: Buckling; Crystals; Diaphragm; Energy conversion; Indexes; Micromechanical devices; Piezoelectric; Polarization; PZT; Residual stress; Residual stresses; Silicon; Sol-gel; Temperature control; Temperature measurement
• ISSN: 2375-0448
• DOI: 10.1109/ISAF43169.2019.9034932

Vibrating energy conversion efficiency was investigated on piezoelectric transducers fabricated on MEMS buckled diaphragm structures from the viewpoint of crystal orientation of sol-gel derived lead-zirconate-titanate (PZT) films. The crystal orientation dominates in-plane stress and spontaneous polarization direction of the PZT films. The in-plane stress affects the static buckling of the diaphragm where a large convex buckling results in a high mechanical conversion efficiency from the flexural vibration to the in-plain vibration. The polarization direction affects the intrinsic piezoelectric conversion efficiency. The crystal orientation of the sol-gel PZT was controlled through pyrolysis temperature between 250°C and 350°C, resulting in a texture variation from (100)-oriented films to (111)-oriented ones. Highly (111)-oriented films showed large polarizations but small buckling deflections, while highly (100)-oriented films showed vice versa. Intermediately textured films with 40-45% (111)-orientation index showed the highest conversion efficiency.