After Yttrium separation from the whole bulk of rare earth metals, it is subject for reduction. The metal is now produced commercially by reduction transferring yttrium oxide into yttrium halogenide:
Y2O3 + 6HF -> (700°C) -> 2YF3 + 3H2O
During the process this compound is mixed twice with sublimated calcium, then placed into tantalum bowl and closed by perforated lid. The bowl is placed into quartz induction furnace. The furnace is closed, air is evacuated from it, and then it begins to be slowly heated. When temperature reaches 600°C, argon is pumped into the furnace; it is ceased when the pressure reaches 500 Hg mm. Reduction begins at 1000°C.
2YF3 + 3Ca -> 2Y + 3CaF2
is exothermic (heat-producing) reaction, so the internal furnace temperature keeps growing. Temperature is increased until 1600°C for better metal and slag separation after which the furnace is cooled down.
The slag material is easily split off. The purity of yttrium reaches 99%. Calcium impurities may be easily removed by vacuum remelting. After more hard oxygen and tantalum extraction the yttrium ingots are available to use. |