D₁₅ Mode PZT-51Piezoelectric Energy Harvesters With Series Connection Structure And Coplanar Electrode Structure

Energy harvesting from ambient vibration sources has been a hot research topic due to itspotential to application in micro-wireless sensors and portable electronics. Many experimentsand mathematical models of energy harvesting performances were investigated for the d₃₁andd₃₃modes piezoelectric energy harvesters. Actually, the piezoelectric coefficients of manypiezoelectric materials are usually large in the order of d₁₅> d₃₃> d₃₁, such as PMN-PT singlecrystal, PZT-4, PZT-5A, PZT-5H, PZT-6B, PZT-7A, BaTiO₃, Na0.5K0.5NbO₃and PbTiO₃ceramics. The piezoelectric energy harvester with large piezoelectric coefficient is of highoutput voltage and power. For example, B. Ren et al. fabricated the piezoelectric energyharvester based ond15mode cantilever with PMN-PT single crystal, and compared with thecantilever device based on the d₃₁mode PMN-PT single crystal, the volume of the wafer isonly a half, while the maximum power output is seven times higher and the correspondingpeak voltage is eight times higher. The investigation provides a proper perspective on thepotential of utilizing thed15mode piezoelectric coupling for energy harvesting. Additionally,the series connection structure can enhance the energy harvesting performance of the d₃₁andd₃₃modes piezoelectric energy harvesters. However, relatively few reports for the applicationof series connection based on d₁₅mode piezoelectric energy harvester are available in theliteratures. Moreover, the coplanar electrode structure may offer some useful guidelines todesign the d₁₅mode thin film piezoelectric energy harvester, so the d₁₅mode bulkpiezoelectric energy harvester with coplanar electrode structure should be fabricated toprovide the guidelines. In a word, the energy harvesting performances of d₁₅modepiezoelectric energy harvester with series connection structure and d₁₅mode piezoelectricenergy harvester with coplanar electrode structure are worth studying. The main contents ofthis thesis are given as follows.1. d₁₅mode PZT-51piezoelectric energy harvester with series connection structure isdesigned and fabricated firstly, and the output peak-to-peak voltages and powers at variousfrequencies and load resistances were studied systematically. In order to compare with theoutput peak-to-peak voltage of the designed piezoelectric energy harvester, a d₁₅modepiezoelectric energy harvester with single PZT-51element also be fabricated. Although thearea A of PEHSC is smaller than that of SPEH, the output peak-to-peak voltage of former ishigher than that of latter.2. The finite element model and mathematical model were proposed for the d₁₅modePZT-51piezoelectric energy harvester with series connection structure. The output peak-to-peak voltage and output power versus frequency curves simulated by the finiteelement model and mathematical model are close to the experimental results, indicating thatthe finite element model and mathematical model are effective to predict the energyharvesting of the device and the experiment is credible. The effects of the proof mass andgeometrical dimensions on the output peak-to-peak voltage are discussed to provide someuseful guidelines to the design of piezoelectric energy harvesting devices.3. d₁₅mode PZT-51piezoelectric energy harvester with coplanar electrode structure isdesigned and fabricated firstly, and a d₁₅mode PZT-51piezoelectric energy harvester withsingle piezoelectric element also is fabricated to compare with the energy harvestingperformances at various frequencies and load resistances. Additionally, the piezoelectricmaterial changes to PMN ceramic, we also compare with their energy harvestingperformances at various frequencies and load resistances to verify the superiority of thecoplanar electrode structure device. Two kinds of experiments show that the superiority of thed₁₅mode piezoelectric energy harvester with coplanar electrode structure.