PZT–PZN–PNN Piezoelectric Ceramics Andapplication In Energy Harvesting Device

In recent years, the advances in wireless technology and low-energy electronics bring significant increase in research of energy harvesting system, which can acquire the ambient energy and convert it into usable electrical energy. One driving force behind the search for new energy harvesting devices is the desire to power sensor networks and mobile devices without batteries. The use of piezoelectric materials to capitalize on the ambient vibrations surrounding a system is one method that has seen a great rise in use for energy harvesting. Piezoelectric materials generate electrical energy when their shapes are distorted by force, allowing them to easily produce high voltage with a relatively simple structure. It can be easily found that piezoelectric transducers are more suitable as the kinetic to electrical energy converters. In addition to the advantage of being smaller and lighter the piezoelectric have higher energy density as compared to their counterparts electrostatic and electromagnetics. However, the low efficiency of energy conversion has always being the leading cause of restricting the device’s widely use. There are two main reasons. Firstly, as the core of piezoelectric energy harvesting devices, the piezoelectric materials should have a high energy conversion coefficient value d33?g33. Secondly, good structure plays a crucial role to improve the energy conversion efficiency. In this paper, the existing solutions to these problems are to obtain piezoelectric materials with high energy conversion coefficient and structure with high energy efficient conversion, so it could be meet the application requirements in energy harvesting.In this paper, first of all, based on the existing knowledge on the MPB of 0.8Pb(Zr0.5Ti0.5)O3–0.1PZN–0.1PNN, experiments have been made to determine the optimal property composition point sand and find the MPB-like line. XRD patterns indicates clearly that the phases shift from rhombohedral to tetragonal Two high d33?g33 values have been found in the composition of Zr:Ti=52:48 and Zr:Ti=50:50, which are 20019×10-15 m2/N and 17500×10-15 m2/N respectively. This will not only find high energy density property point, but also enlarge people’s understanding on the material systemSecondly, an experimental unit of elastic ball-impacting piezoelectric cantilever has been set up and experiments have been carried on to find out the optimized parameters on high energy output and high ME energy transferring efficiency. Through the experiments, it is found that the dimensions of copper sheet and ceramic have a major influence on the output voltage. However, while the length and width are settled, within certain range, the thickness of the copper sheet has the greatest influence.Finally, based on the above fundamental research, two type of impact-induced high efficiency and high output power piezoelectric energy harvesting devices have been designed, set up and experimentally optimized. In the first prototype, the impact force is introduced through forming a piezoelectric bimorph cantilever polygon which is fixed at the circumference of the rotating fan’s internal surface. Elastic balls are put inside the polygon. The design enables each bimorph being impacted the same similar area and every bimorph being impacted the same similar area in different moments. As a result a relatively stable output frequency can be obtained. The output frequency is also able to be changed by choosing different dimensions of the bimorphs and which will make the device simpler and the cost lower. The second prototype device utilizes twelve piezoelectric bimorphs shape a polygon and six sectors are formed by six radial placed blades and the piezoelectric bimorphs. This Darrieus-type windmill with vertical shaft will easily rotate in any direction of wind and has higher wind energy utilization rate. The elastic balls within the six sectors hit on the tip of each piezoelectric transducer, impact and rebound alternately between the blades and the piezoelectric bimorphs, and which solve the problem of stop running caused by centrifugal force at higher rotating speed.