A PIEZOELECTRIC PZT CERAMIC MULTILAYER STACK FOR ENERGY HARVESTING UNDER DYNAMIC FORCES

In this paper, we report the study of a “33 ” longitudinal mode, piezoelectric PZT ceramic multilayer stack (PZT-Stack) with high effective piezoelectric coefficient for broader bandwidth high-performance piezoelectric energy harvesting transducers (PEHTs). The PZT-Stack is composed of 300 layers of 0.1 mm thick PZT plates, with overall dimensions of 32.4 mm × 7.0 mm × 7.0 mm. Experiments were carried out with dynamic forces in a broad bandwidth ranging from 0.5 Hz to 25 kHz. The measured results show that the effective piezoelectric coefficients (EPC, deff) of the PZT-stack is about 1 × 105 pC/N at off-resonance frequencies and 1.39 × 106 pC/N at resonance, which is order of magnitude larger than that of traditional PEHTs. The EPC do not change significantly with applied dynamic forces having root mean square (RMS) values ranging from 1 N to 40 N. In resonance mode, 231 mW of electrical power was harvested at 2,479 Hz with a dynamic force of 11.6 Nrms, and 7.6 mW of electrical power was generated at a frequency of 2,114 Hz with 1 Nrms dynamic force. In off-resonance mode, an electrical power of 18.7 mW was obtained at 680 Hz with a 40 Nrms dynamic force. A theoretical model of energy harvesting for the PZT-Stack was established. The modeled results matched well with experimental measurements. This study demonstrated that structures with high EPC enable PEHTs to harvest more electrical energy from mechanical vibrations or motions, suggesting an effective design for high– performance low-profile PEHTs with potential applications in military, aerospace, and portable electronics. In addition, this study provides a route for using piezoelectric multilayer stacks for active or semi-active adaptive control to damp, harvest or transform unwanted vibrations into useful electrical energy. 1