Development of lead-free materials for piezoelectric energy harvesting
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Development of lead-free materials for piezoelectric energy harvesting R. Rai1, I. Coondoo1, R. P. Lopes1, I. Bdikin2, R. Ayouchi3, S. Bhattacharaya, R. Schwarz3, A. L. Kholkin1 1
2
DECV & CICECO, University of Aveiro, Aveiro, Portugal. Centre for Mechanical Technology and Automation, University of Aveiro, Aveiro, Portugal. 3 Department of Physics and ICEMS, Instituto Superior Técnico, Lisbon, Portugal.
ABSTRACT Mechanical energy harvesting from ambient vibrations is an attractive renewable source of energy for various applications. Prior research was solely based on lead-containing materials which are detrimental to the environment and health. Therefore, lead-free materials are becoming more attractive for harvesting applications. The present work is focused on the development of lead-free piezoelectric materials based on solid solution having composition (KNa)NbO3-xABO3, (where A = Li, and B = Nb; x = 0, 5, 5.5, 6, and 6.5 wt%). The solid solutions of the above ceramics were prepared by using solid-state reaction method. The X-ray diffraction spectra exhibited single phase formation and good crystallinity with LiNbO3 addition up to x = 6.5 wt%. Dielectric studies reveal that the composition with LiNbO3 = 6.5 wt% exhibits superior properties suitable for piezoelectric energy harvesting applications. The nanoscale piezoelectric data obtained with piezoresponse force microscopy provide a direct evidence of strong piezoelectricity with LN doping. The best piezoelectric properties are obtained for the composition K0.5Na0.5NbO3 – 6.5%LiNbO3. INTRODUCTION Energy harvesting is the process by which energy is derived from external sources (e.g., solar power, thermal energy, wind energy, mechanical vibrations, and kinetic energy), captured and stored. The objective of a power harvesting device is to capture the untapped energy surrounding a system which is normally lost and convert it into usable energy for the electrical device to consume. Recently, technologies such as biomechanical, piezoelectric and pyroelectric energy harvesting are attracting worldwide interest. Among these, most promising technique is mechanical energy harvesting that utilizes the ability to convert mechanical strain energy into electrical energy and vice versa using piezoelectric components. Piezoelectric materials are known for direct and converse piezoelectric effect and thus can be used to convert oscillatory mechanical energy into electrical energy. This technology, together with innovative mechanical coupling designs, can form the basis for harvesting energy from mechanical motion. With the recent surge of micro scale devices, piezoelectric power generation can provide a convenient alternative to traditional power sources used to operate certain types of sensors/actuators, wireless networks, and MEMS devices. Until now research was solely based on lead-containing materials with high efficiency, however, environmental concerns are strongly driving the need to replace lead-based piezoelectric materials, e.g., lead zirconate titanate (PZT) which
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