Lithium sensors based on Li₆La₃Ta_1.5Y_0.5O₁₂ and Li₆BaLa₂Ta₂O₁₂ garnet electrolytes for molten lead alloys

The development of effective breeding blankets is crucial to the success of future fusion reactors. One of the main liquid breeding candidates is molten eutectic Pb-Li. In this environment, it is essential to control lithium concentration and dosage to keep the adequate composition in the melt. In this frame, on-line and on-board lithium monitoring tools, which can operate under extreme conditions, are required. Electrochemical sensors based on lithium conducting solid electrolytes (Li₆La₃Ta_1.5Y_0.5O₁₂ and Li₆BaLa₂Ta₂O₁₂) were designed and tested. These potentiometric sensors were used to measure the Open Circuit Potential (OCP) in molten lead-lithium alloys with different lithium concentrations. Measurements were performed at 400 °C, 500 °C, and 600 °C. Experimental OCP values were in good agreement with those calculated with the Nernst equation. OCP values showed a linear relationship versus the logarithm of the lithium activities, fulfilling the Nernst equation.