Study on Preparation and Electromechanical Energy Conversion of PZT Piezoelectric Fibers

• Main Authors: Chung-Hao Yi, 易崇皓
• Other Authors: Horng-Yi Chang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/86747024142334586824

碩士 === 國立臺灣海洋大學 === 輪機工程系 === 100 === The piezoelectric properties of lead zirconate titanate (PZT) originate from the asymmetrical crystal structure, which are affected by dopants, temperatures and compositions. When the PZT material size reduced to micron- or even nano-meter scale, the grain size and lattice would be varied due to the generated geometrical stress and the obtained results possibly affected the piezoelectric properties. This thesis studies the one-dimensional PZT fiber preparation and its related properties. Such prepared PZT fibers were arrayed and combined with polymer resin to form a 1-3 flexible PZT piezoelectric fiber composite so as to enhancing the piezoelectric constant and power density. The single grain stacking nanofibers were prepared by electro-spinning method and then characterized. In this study, we produced PZT fibers by extruding PZT fibers in which PVA condensation reacted with boric acid in an aqueous bath. The advantages of this innovated method are reduction of the amount of organic additives, sintering PZT fibers densely, and dropping the extrusion pressure as to increasing the lifetime of the extruding orifice. The condensation reaction was very quickly when the extruded fiber paste in an aqueous bath containing boric acid. This extruding process is suitable for continuous mass production. By adjusting PVA molecular weight and concentration of boric acid in aqueous bath, uniform PZT fibers with true roundness were fabricated successfully with diameter of 200 μm-1 mm. The dielectric constant (εr) and saturated polarization (Ps) increased with PZT fibers volume fraction increase for 1-3 type of PZT-epoxy composite. The dielectric constant 2400 (at 1 kHz) and saturated polarization 21 μC/cm2 were obtained when the PZT fiber volume fraction was up to 78%. The piezoelectric coefficient d33 was sensitive with the diameter of the PZT fiber, the composite thickness and the PZT fiber volume fraction in composite. The maximum d33 value was 650 pC/N. Uniform PZT fiber arrays in 1-3 composite allowed the higher PZT volume fraction in composite and then achieved high piezoelectric properties close to bulk characteristics and behaved a flexible feature. The PZT fiber with diameter less than 50 μm is difficult to prepare by extrusion method. The nano-PZT fibers with 50-400 nm diameter were synthesized by electro-spinning method. The abnormal grain growth occurred after 800°C post-heat treatment from the SEM/HRTEM observation. The lattice constant ratio of c/a (tetragonality) decreased with the post-heat treated temperature from 600 to 800°C analyzed by XRD. This result indicated that the piezoelectric characteristics may disappear due to a transition from asymmetrical tetragonal lattice to symmetrical pseudo-cubic lattice resulted from nanofiber surface confined stress. How to synthesize nano-PZT fibers and to maintain the high piezoelectric properties with anisotropic crystal lattice will be a breakthrough issue for materials scientists.