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Caractérisation de l'effet électrocalorique dans des matériaux solides et cristaux liquides ferroélectriques

Abstract : This thesis work deals with the characterization of the electrocaloric effect in solid and liquid crystal ferroelectric materials. Following the 2006 discovery of Mischenko and al., the characterization techniques of the electrocaloric effect and the exploration of new caloric materials have attracted much attention. This discovery showed also that electrocaloric materials can be used for efficient innovative solution for refrigeration devices. This PhD dissertation focuses on the development of new techniques used to evaluate the electrocaloric effect by the photopyroelectric technique and by calorimetry. Few years ago, a new particular configuration based on the photopyroelectric technique, developed in our laboratory, was described for measuring thermal parameters of pyroelectric materials themselves. By means of this technique, we indirectly investigate the electrocaloric effect in ferroelectric materials by measuring the ratio of the pyroelectric coefficient to the volumetric heat capacity, as function of temperature and applied field, using Maxwell's relation. Measurements were carried out on ferroelectric solid materials (TriGlycine Sulfate) and liquid crystals. Electrocaloric effect has been evaluated around the phase transition temperature of each sample. To further validate the accuracy to the evaluated adiabatic temperature changes, we proceeded to indirect measurements by using the polarization reversal current technique. In the present work, we also developed a calorimeter in order to directly evaluate the electrocaloric effect. This technique is mainly used to measure with high resolution the heat capacity and enthalpy near phase transition temperature. In addition, this technique allows us to directly measure the temperature and the amount of heat absorbed or transferred from the material to the surrounding environment. A primary study of the electrocaloric effect was carried out on a multilayer material based on barium titanate. The results obtained by this approach have been then compared to conventional direct and indirect measurements. Those two new approaches give access to the measurement of both thermal and pyroelectric properties allowing the evaluation of the electrocaloric effect.
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Submitted on : Tuesday, July 16, 2019 - 1:45:07 PM
Last modification on : Thursday, December 10, 2020 - 3:22:06 PM


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  • HAL Id : tel-02185059, version 1



Eliane Bsaibess. Caractérisation de l'effet électrocalorique dans des matériaux solides et cristaux liquides ferroélectriques. Matériaux. Université du Littoral Côte d'Opale, 2018. Français. ⟨NNT : 2018DUNK0512⟩. ⟨tel-02185059⟩



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