Two-Phase Rare-Earth Alloys as Reference Electrodes in Molten Chlorides for Reliable Electrochemical Measurements

• Published in: Rare Metal Technology 2022 pp. 325 - 332
• Main Authors: Smith, Nathan D., Baldivieso, Stephanie Castro, Lichtenstein, Timothy, Im, Sanghyeok, Kim, Hojong
• Format: Book Chapter
• Language: English
• Published: Switzerland Springer International Publishing AG 2022; Springer International Publishing
• Series: The Minerals, Metals & Materials Series
• Subjects: Liquid metals; Rare-earth elements; Reference electrodes; Two-phase electrodes
• ISBN: 9783030926618; 3030926613
• ISSN: 2367-1181; 2367-1696
• DOI: 10.1007/978-3-030-92662-5_31

Electromotive force measurements were used to examine pure rare-earth reference electrodesReference electrodes (Nd, Gd) inNdmoltenGd chloride salts (LiCl-KCl-RECl3) over a temperature range of T = 400–800 °C to determine the effects of disproportionation reactions (i.e., Nd + NdCl3 → NdCl2) andNd active metal dissolution on their longevity and stability. Several methods for developing and calibrating a stable two-phase GdGd-Bi electrode were investigated including the use of a pure GdGd metal reference electrode continuously submerged in the electrolyte, a pure GdGd metal reference electrode intermittently dipped into the electrolyte, and a transient technique that deposited pure GdGd onto an inert W wire. Electromotive force measurements were also employed to examine the lifetime of the two-phase alloy as the reference electrode in comparison to a pure rare-earth metal as the reference electrode. Pure rare-earth metal did not exhibit stability for more than 15 h, whereas two-phase GdGd-Bi electrodes were found to be stable for over 24 days at T = 500–700 °C.