Contribution à l'électrodéposition en milieu liquide ionique de tellurure de bismuth en vue de son dopage

Abstract : Thermoelectricity has soared up for few years. Currently reserved to niche markets such as informatics or aerospace, devices based on thermoelectric materials could be used in vehicles in order to harness wasted heat. However, the performance of these materials is insufficient for scale up. Among thermoelectric materials, bismuth telluride (Bi2Te3) compounds are the most efficient at room temperature. The purpose of this work was the electrochemical synthesis of doped-Bi2Te3. Rare earth elements being hardly reducible, aqueous medium is unsuitable for their electrodeposition that's why ionic liquids were chosen as electrolytes because of their large electrochemical window. The first part of this PhD work consisted in elaborating the most suitable ionic liquid allowing lanthanum(III) electrochemical reduction. Among ionic liquids tested, 1-ethyl,1-octylpiperidinium bis(trifluoromethylsulfonyl)imide (EOPipTFSI) was selected. In a second part, we defined a bath composition allows reaching a high solubility of precursor salts by using a binary mixture EOPipTFSI:EOPipBr, EOPipBr being the intermediate product of EOPipTFSI synthesis. Then, electrochemical behaviors of several Bi(III)/Te(IV) mixtures were studied. The electrochemical system is complex. Nevertheless, this detailed analytical study led to Bi2Te3 electrochemical synthesis. Finally, the Te(IV)/Te(0) electrochemical system was more deeply studied, the analysis of Te deposits revealed the coatings were composed of single crystalline nanowires. The influence of experimental on nanowire diameter and coatings morphology was studied. These nanowires could be of great interest to prepare Te-Bi core-shell nanostructures
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Jonathan Szymczak. Contribution à l'électrodéposition en milieu liquide ionique de tellurure de bismuth en vue de son dopage. Autre. Université de Lorraine, 2013. Français. ⟨NNT : 2013LORR0316⟩. ⟨tel-01750657⟩

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