Terbium oxide

This heavy rare earth from the lanthanoid group is a true all-rounder. Like dysprosium oxide, it can protect magnets from heat-related demagnetisation. This property is becoming increasingly important due to the sharply rising future demand for magnets for wind turbines, as they heat up significantly during operation. A concept paper by the German Association of Energy and Water Industries states that significant shortages and price increases are to be expected for dysprosium oxide and terbium oxide. According to the report, Europe needs 10,000 tonnes of such magnets for wind power expansion alone. Only 1% of these magnets are produced in Europe, while it requires 50% of the magnets. Terbium as a metal is also important for the energy transition due to its use in fuel cells, where it stabilises the microstructure. Finally, terbium oxide is also used in semiconductor technology. Semiconductors are often doped with terbium oxide and are considered the “oil of the future”.

• Semiconductors
• Phosphor in cathode-ray tubes
• Coating of data storage media
• Micro-magnets
• High-temperature fuel cells
• Improvement of neodymium-iron-boron magnets
• Dopant and light emitter in the lighting industry

The most important source for mining heavy rare earths such as terbium is ion-adsorption clays, which are currently mined almost exclusively in China and Myanmar. The raw material is extracted on site by leaching, after which the metals and oxides are produced.

The production of terbium oxide begins with the mining of terbium-bearing ores such as xenotime, gadolinite, euxenite, and monazite sands, which can contain up to 300 grams of terbium per tonne. Metallic terbium is obtained after concentrating the ores and separating the other rare earth metals, which is done using ion-exchange processes. The terbium is then produced by reducing the resulting terbium halides with calcium or magnesium. Producing terbium oxide at an industrially usable purity is very complex. Since it occurs in nature only in compounds, mostly with yttrium, it must first be isolated. It is then first converted into terbium fluoride using hydrofluoric acid, and only then reduced to terbium with calcium. Because these processes are rarely carried out, terbium oxide is one of the scarcest rare earths. As with the other heavy rare earths, China holds the monopoly.