Ceramics arising from Pb(Mg1/3Nb2/3)1‑x TixO3 with composition near the morphotropic phase boundary (MPB) were prepared by the modified solid-state reaction method. The synthesized ceramics were characterized, and then the operating principles of pyroelectric and piezoelectric harvesters are reviewed. In addition, the dielectric behavior is measured to determine the dielectric constant and losses at different temperatures and frequencies. The typical behavior of a ferroelectric relaxer was observed by adding the PbTiO3 phase. The thermal properties are also analyzed by PPE calorimetry, presaging a one-dimensional heat-flow process. As a result, the dielectric and thermal behaviors of the as-prepared ceramics as well as their thermal stability are intimately linked to the PbTiO3 addition to PbMgl/3Nb2/3O3 phase. These materials exhibit good physical performances, which makes them promising candidates for pyroelectric micro-generators (PEG), cooling systems and infrared applications.
We deal with the thermal energy which is one of the ambient energy sources surely exploitable, but it has not been much interest as the mechanical energy. In the last decades, direct energy conversion devices received particular attention because of the need to develop flexible systems, autonomous and self-powered. The energy harvesting aims to make the systems, autonomous in terms of energy and to contribute to sustainable development by the total respect of the environment. In this paper, our aim is to use thermal energy and show that it's an important source for producing the electrical energy through pyroelectric effect: first, elaborate charged polyurethane (PU) with different proportions (20%, 30% and 40%) of lead zirconate titanate (PZT), then to use those PZT/PU composites as a pyroelectric energy harvesting systems. Secondly, the optimization of energy harvesting and storage. The PZT/PU composite prepared is considered as one of the most promising composites for energy harvesting systems, due its various advantages, such as mechanical flexibility, high temperature sensitivity, low cost as well as its high electro-active functional properties. The current generated by all samples for temperature fluctuations over a period of time in the order of 140 s have been rectified and stored in a charge capacitor of 1μF. The stored energy can reach a maximum value in the order of 14μW for a composite loaded with 40% PZT. Therefore, these composites show an interesting potential to be used in various applications. These results shed light on the thermoelectric energy conversion by a new composite of PZT/PU having the pyroelectric property.
The piezo-ceramics have been using in many piezoelectric applications such as transducers, sensors and actuators. Under high mechanical and electrical strengths, the nonlinear behavior observed on these devices can describe by the second order piezoelectric constitutive equations. However, their hysteretic behavior cannot be described by these equations. In this paper, a more general theoretical model was developed to describe the nonlinear and hysteretic behaviors of the piezo-ceramics under high electrical and mechanical strengths. The model, based on the theory of Landau-Devonshire, can simulate the hysteresis cycles under the combined cyclic electric and static mechanical strengths. It can describe the evolution of the relative dielectric permittivity ε33 as a function of the applied electric field. Using the scaling law, it can also describe the evolution of the piezoelectric coefficient d33 as a function of the applied electric field.
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