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Author
Ferré March, Òscar
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Abstract
Lithium 6 is the isotope required to generate in-situ tritium in fusion reactors, so devices capable of measuring lithium in-line will be required to monitor its concentration in the molten metal Pb-17Li. For this purpose, it is proposed to construct lithium electrochemical sensors based on ceramic-type solid-state electrolytes. These sensors have several advantages: they are generally stable compounds that can withstand the aggressive chemical environment of liquid metals, their ionic conductivity increases with temperature, and the output signal (cell potential) is easy to measure.
In this work, synthesis and sintering conditions for the solid conductive lithium electrolyte Li6La3Ta1.5Y0.5O12 are presented. To ensure the structure of the desired electrolyte, the crystallographic phases are characterized with XRD, its surface microstructure with SEM, and the lithium content is determined by atomic flame absorption spectroscopy analysis. Finally, it is satisfied with sintered disks for the construction of the Li-probes. The sensor consists in the union of the sintered ceramic disc with an alumina tube using a glass sealant.
Potentiometric measurements were performed to determine the OCP value between a working and a reference electrode. Each electrode consisted of a Pb-Li alloy of different composition. Pb-Li alloys in the working electrode started at values near 3at% up to 15.9at% Li and the reference electrode a composition of 16,57% was established. The potentiometries were performed at three different temperatures: 400 °C, 500 °C and 600 °C. The values obtained were compared with the theoretical values calculated with the Nernst equation.
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