Fluorination of rare earths

Under isothermal conditions at 5O0 deg C and partial pressure 1 atm, the process of fluorination of rare-earth metals is studied using the gravimetric method. It is shown that the metals studied can be broadly divided into three groups by their behaviour in the flow of fluorine. The first group includes Ce which burns in fluorine, and also Psub(r), Tb, La and Sm reacting with relatively high rates. The second group consists of metals featuring a moderate fluorination rate, viz Y and Gd. The third group includes chiefly metals from yttrium subgroup - Dy, Mo, Er, Tm, Yb and Nb, characterized by a slow rate of reaction with fluorine. On the heaviest metals, protective films of fluorides are formed which makes these metals resistant in the fluorine atmosphere