Structural Transformation and Pressure-Induced Phase Transitions in PZT

Angle-dispersive X-ray diffraction, Raman scattering and dielectric spectroscopy measurements versus hydrostatic pressure were carried out to follow the crystalline-to-crystalline transformation occurring in PbZr_{1 – x}Ti_xO₃ ceramic powders. Different PZT compositions under hydrostatic pressure up to 20 GPa were studied. Dielectric measurements versus pressure up to 2 GPa are discussed to bring new insights on the Pressure-composition (P-x) phase diagram. Based on these results, an updated version of the PZT (P-x) phase diagram is proposed.     

Design and Characterization of a Low-Cost Piezoelectric Vibration Energy Harvester with Bulk PZT Film

To improve the efficiency of MEMS piezoelectric vibration energy harvesters (PVEHs), the bulk lead zirconate titanate (PZT) has been used to substitute the thin film PZT for the higher mechanical-electrical coupling coefficients. The expensive equipment of micromachining set a high entry barrier on the research of PVEHs with high efficiency. To solve this issue, this paper developed an efficient PVEH with bulk PZT using common precision machining, whose dimensions and electrical outputs are comparable to the MEMS devices. After numerically analyzing the effects of the length ratio of the proof mass to the harvester on the output power, a compact PVEH consisting of a cantilevered uni-morph and a tungsten proof mass was designed. Simulations show that the mechanical damping ratio and the thickness have little effects on the optimized length ratio. By using a uni-morph with the copper structural layer of about 80-90μm and the bulk PZT-5H layer of 139μm, a low-cost harvester prototype was assembled. The key parameters of the prototype were experimentally identified and compared with the theoretical predictions. Under the harmonic base excitation of 0.4g (where g = 9.8m/s2) at 160 Hz, the maximum output power of the prototype is about 76.7μW, with the normalized power density of about 3.35mW/cm3/g2. Under base excitation of 0.4g at 159Hz, the prototype charged a 680μF capacitor from 0 to 4.84V in about 154 seconds.