Rare earths: applications, mineral resources, thorium, and the balance problem

摘要

Rare earth (RE) metals are crucial for the performance of a wide variety of technologies and have been identified as 'critical materials' in the EU, the USA, and Japan. They have only been available in commercial quantities as pure, individual elements for the last 60-70 years due to their mutual similarities in chemical properties and the requirement for complex processing to separate the pure metals. Mineral compositions vary, but the crude generalization is that if one RE metal is in demand then applications must be found for the remaining scandium, yttrium, and lanthanides that will also be present in the mineral. Uses for the REs have fluctuated through the years, with the cost burden for production settling on different materials (those in demand) such as early uses for cerium in lighter flints through yttrium, europium, and terbium for colour television screens, samarium for the first RE permanent magnets, and for neodymium and dysprosium in the most recent RE permanent magnets. The quantities required are minor by commodity standards, but their critical impact is significant in modern technology. The methods of processing, the control and use of actinides (thorium), and in particular the applications of REs in permanent magnets will be examined as the driving force for the RE industry.