chapter  4
Pages 114

The rare-earth oxides are the usual end products of the ore processing and separation operations. They are therefore the natural starting material for conversion to metal by reduction. Rare-earth oxides are extremely stable, and their reduction to metal is, therefore, very difficult. The difficulties are usually compounded but occasionally alleviated by the physical properties such as the melting point and vapor pressure of the rare-earth metals. In several instances, conversion of the rare-earth oxide to a rare-earth halide and reduction of the halide to the metal is a useful procedure because of certain inherent characteristics of the halide reduction method. Fused salt electrolysis as applied to the production of reactive refractory metals can also be effective for rare-earth-metal preparation. The relatively low melting point of many of the rare-earth metals is an advantage here. The preparation of rare-earth metals by a route in which an alloy is prepared first and the metal is then recovered from the alloy is another interesting possibility, being beneficial in both chemical and electrolyte methods of reduction.