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# Vibrational energy harvesting using piezoelectric ceramics and free-standing thick-film structures

Bai, Yang (2015)
Ph.D. thesis, University of Birmingham.

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## Abstract

This thesis presents a series of broad but systematic and consecutive investigations on the topic of piezoelectric energy harvesting. These include material fabrication and characterisation, harvester fabrication and material parameter selection, electric output and dynamic behaviour tests of energy harvesters, and the feasibility of utilising lead-free piezoelectric materials for energy harvesting. Three lead-based and one lead-free perovskite solid-solutions compositions have been researched individually and compared to each other. In the form of bulk ceramics the lead-free composition is considered capable of replacing the lead-based compositions for vibrational energy harvesting at room temperature. Typical properties of ε$$_r$$≈4700, $$P$$$$_r$$≈9 μC/cm$$^2$$, $$d$$$$_3$$$$_3$$≈500 pC/N, $$k$$$$_p$$≈0.51 have been achieved for the lead-free and lead-based compositions respectively. Vibrational energy harvesting based on a novel structure of piezoelectric/silver multi-layer free-standing thick-film unimorph and bimorph cantilevers have been investigated using two of the lead-based compositions. A planar shrinkage difference of 3-6% between the silver and piezoelectric layers is suggested in order to ensure successful fabrication. When tested under harmonic vibration conditions, a comparison of unimorph individual harvesters suggests that higher piezoelectric voltage and electromechanical coupling coefficients may be preferred when selecting materials. Further optimisations involving bimorph devices with tip proof mass have demonstrated maximum harvester outputs (root mean square) of about 9 μW and 2.8 V with approximately 14% bandwidth under resonant vibrations (I 00-150 Hz, 0.5 - I.Og). In addition, the cantilevers have utilised to harvest wind energy with a modified spinning configuration, exhibiting 3.4 V average open-circuit output voltage in optimum wind conditions.

Type of Work: Ph.D. thesis. Button, Tim W Colleges (2008 onwards) > College of Engineering & Physical Sciences School of Metallurgy and Materials Publications arising from research:- Journal Articles: Bai, Yang, Carl Meggs, and Tim W. Button. "Investigation of Using Free-Standing Thick-Film Piezoelectric Energy Harvesters to Develop Wideband Devices." International Journal of Structural Stability and Dynamics 14.08 (2014). DOI: 10.1142/S0219455414400161. Zeb, A., Bai, Y., Button, T., Milne, S. J. (2014), Temperature-Stable Relative Permittivity from −70°C to 500°C in (Ba0.8Ca0.2)TiO3–Bi(Mg0.5Ti0.5)O3–NaNbO3 Ceramics. Journal of the American Ceramic Society, 97: 2479–2483. DOI: 10.1111/jace.12949 Conference Proceedings: Bai, Y., Meggs, C., Button, T. W., 'Fabrication and Investigation of Free-standing Piezoelectric Thick-film Cantilevers for Energy Harvesting Applications', 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop 2013. Proceedings : Hannover, July 14th - July 17th, 2013. Jiang, Y., et al. "Lead-free piezoelectric materials and composites for high frequency medical ultrasound transducer applications." Ultrasonics Symposium (IUS), 2014 IEEE International. IEEE, 2014. DOI: 10.1109/ULTSYM.2014.0221 TK Electrical engineering. Electronics Nuclear engineeringTN Mining engineering. Metallurgy University of Birmingham 5826
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