Vibration energy harvesting based on piezoelectric or triboelectric effect is a hot research topic in the field of nano electric generator. Although the voltage generated by the piezoelectric or triboelectric mechanism is high, the current output is usually very low, only in the level of mA or even nA range. Recently, Prof. Shuxiang Dong’s group found that a low-cost lead zirconate titanate (PZT) based relaxor piezoelectric ceramic has the highest piezoelectric stress coefficient (e33), with a high effective piezoelectric coefficient (d33*) and a lower mechanical resonance impedance. The piezoelectric ceramic is used to harvest the vibration energy, and it is shown that the maximum output current is 2.5 mApp and the maximum output power is 14 mW under an inertia force of ~0.29N at resonance frequency. The results are published in Advanced Functional Materials (IF=12.12), titled “Giant Piezoelectric Coefficients in Relaxor Piezoelectric Ceramic PNN-PZT for Vibration Energy Harvesting”.
It is well known that the piezoelectric properties of PZT based ceramics are inferior to piezoelectric single crystals due to their polycrystalline structure. The Dong’s group characterizes the full set material properties of the 0.55Pb(Ni1/3Nb2/3)O3–0.135PbZrO3–0.315PbTiO3 (PNN-PZT) relaxor ceramic prepared via solid state reaction method and find the piezoelectric stress coefficient (e33) to be as high as 39 C/m2 which is the highest value in ferroelectric ceramics, ferroelectric single crystals, and other piezoelectric materials. That is, under the same strain or stress conditions, the PNN-PZT relaxor ceramics can induce more charges. To prove this prediction, cymbal energy harvesters are fabricated with the PNN-PZT ceramic and the commercial Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) piezoelectric single crystal of the same size. Under the acceleration of 3.5 g (~0.29 N) and at resonance frequency, the maximum output power of the PNN-PZT ceramic harvester is 14.0 mW which is comparable with that of the PMN-PT single crystal, and notably the maximum output current is 4 times of the PMN-PT single crystal. The results verify the potential of the cheap PNN-PZT ceramic in vibration nano/micro energy harvesting, such as self-powered and self-sensed network. In addition, the effective piezoelectric coefficient d33* = 1753 pm/V is also comparable with that of the commercial PMN-PT piezoelectric single crystal and thus it shows great application prospect in precision actuation.
Figure of PNN-PZT ceramic cymbal energy harvester: a) test setup of vibration energy harvesting; b) schematic view of the structure and sizes of the harvester; c) FEA modeling result under vibration excitation; d) the harvested power and load relationship at 3.5 g; and e) the output current and load relationship at 3.5 g.
The first author of this work is Xiangyu Gao, a Ph.D. student of the Department of Materials Science and Engineering, College of Engineering, Peking University. The research was supported by the National Natural Science Foundation of China (Grant Nos. 51772005 and 51132001) and Beijing Key Laboratory for Magnetoelectric Materials and Devices.
Dong’s group has been devoting to the design and application of piezoelectric materials, magnetoelectric materials and devices for years. The research on piezoelectric ultrasonic piezoelectric motor, actuators, sensors and micro energy harvesting has been widely admitted in the world. Prof. Dong has published 150 paper in international journals such as Advanced Materials, Advanced Functional Materials, Applied Physics Letters, etc with the citations more than 6,400 times, and he owns more than 30 authorized patents in China and United States. In the year from 2014 to 2017, he is selected as China's top cited scholar by Elsevier.