Investigation of the systems M/sup I/F--M/sup II/F/sub 2/--Ln/sub 2/O/sub 3/ (M/sup I/ is Li, Na, K, or Rb; M/sup II/ is Mg, Ca, Sr, or Ba; Ln is La or Nd) by the isothermal method

Solution of La and Nd oxides in the fused systems M/sup I/F--M/sup II/F/sub 2/ (M is Li, Na, K, or Rb; M/sup II/ is Mg, Ca, Sr, or Ba) is accompanied by a chemical reaction. The latter is probably due to exchange reactions between the oxide oxygen and the F/sup -/ ion of the solvent. Transfer of the rare earth from the oxides to the melt increases with a decrease in the strength of M/sup II/F/sub 2/ and with an increase in the strength of MO, and also with weakening of complex formation between the fluorides of alkali and alkaline earth elements.