Extraction of Terbium from Terbium–Iron Alloys Using Molten Magnesium

• Published in: MATERIALS TRANSACTIONS Vol. 66; no. 6; pp. 724 - 732
• Main Authors: Murata, Takashi, Yamaguchi, Katsunori, Oishi, Tetsuo
• Format: Journal Article
• Language: English
• Published: Sendai The Japan Institute of Metals and Materials 01.06.2025; 公益社団法人 日本金属学会; Japan Science and Technology Agency
• Subjects: Alloys; Distillation; Electrolysis; energy saving process; Eutectic alloys; Eutectic composition; Ferrous alloys; Iron; Liquid metal extraction; Liquid phases; Magnesium; Molten salts; pyrometallurgy; rare-earth element; Solid phases; Terbium
• ISSN: 1345-9678; 1347-5320
• DOI: 10.2320/matertrans.M-M2024816

Developing a new and energy-saving production process for high-purity terbium that combines molten salt electrolysis, liquid metal extraction, and distillation is necessary. Therefore, we experimentally determined the optimal conditions for the selective extraction of Tb from a Tb–Fe alloy using molten magnesium, which can be obtained via molten salt electrolysis. A eutectic alloy composition of 88 mass%Tb–12 mass%Fe and Mg was maintained at 973 or 1273 K under an Ar atmosphere. The sample was separated into an Fe-based solid phase with a Tb content lower than the eutectic composition and a Tb–Mg-based liquid phase with a small amount of Fe. The obtained results indicate that Tb alloys containing approximately 0.2 mass% Fe can be recovered by liquid Mg extraction at 973 K and subsequent distillation, assuming that only the Mg in the liquid phase is fully volatilized. This concentration of Fe was approximately 2 mass% at 1273 K. Therefore, increasing the extraction temperature significantly increased the concentration of Fe in the Tb obtained by the new process.