Investigation On PZT Piezoelectric Material D₃₁ Model Series Cantilever Energy Harvesting Performance

PZT piezoelectric ceramic has the characteristics of strong piezoelectricity, easymodification, high Curie temperature and stability, which is widely used in piezoelectricdevices. Piezoelectric energy harvesters (PEHs) are with simple structure, green, noproducing heat and electromagnetic noise. For PEHs, researchers not only have carried onexperimental studies, also proposed kinds of mathematical models. At present, most of theproposed models are limited in Euler Bernoulli beam theory on the d31mode. This theoryignores shear strain. Analysis models about the upper and lower electrode structure of d31thick and short cantilever PEH are seldom reported. As rapid development of MEMStechnology, the traditional piezoelectric transducer developed along micromation, integrationdirection. Coplanar electrode structure can solve the problem of the energy harvester withonly the top electrode of the piezoelectric layer collecting electric power energy. Coplanarelectrode structure may provides guidance for d31model thin film PEHs. Therefore, designingand making the bulk material coplanar electrode structure d31mode piezoelectric energyharvester can provide guidance for its miniaturization and integration. The main contents ofthis thesis are as follows:(1) Based on the piezoelectric constitutive equation and Timoshenko beam theory, theelectrical and mechanical model of d31mode cantilever beam PEH was deduced under simpleharmonic oscillation. According to the model theory and finite element modeling, cantileverPEHs with and without a tip mass were calculated and simulated. The results verified thecorrectness of the proposing cantilever PEH model. The electrical properties on the proposingcantilever PEH model with a tip mass was respectively comparing to experimentalmeasurements, Euler-Bernoulli beam theory and finite element simulation results. The errorvalue of the proposed model and the experiment results was less than that of the EulerBernoulli beam theory and experimental results. Affecting factors of the d31mode cantileverPEH performance were analyzed indetails. The shear strain of the stubby cantilever PEHscould not be ignored. Concrete factors affecting and improvement ways were analyzed andput forward of the d31mode cantilever PEH performance. 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.(2) The coplanar electrode structure d31mode PZT-51PEH was designed and constructed,and the electrical properties at various load resistances, the transient voltage-time curves andthe vibration excitation voltage dependence curve of peak-to-peak voltage in Rl=4.7M were measured and compared systematically. The output peak-peak voltage and loadresistance was proportional relationship, but the output power only could achieve maximumin the best load resistance; with the load resistance increasing, the instantaneous resonanceoutput voltage was also increase accordingly; both of piezoelectric materials’ strain and theoutput voltage were proportional to the input of vibration acceleration. Therefore, designingand making the bulk material coplanar electrode structure d31mode piezoelectric energyharvester can provide guidance for its miniaturization, integration thin.