Comparison of yttrium, lanthanides and actinides in respect to unit cell volumes of isostructural compounds and thermodynamic functions of complex formation

The investigations carried out up to now and presented in this paper show that apart from the well known itinerant properties of yttrium in respect to free energy of complex formation, also actinides(III) change their position in the lanthanide series in respect to δG. It is also shown that yttrium and actinides exhibit itinerant behaviour in respect to unit cell volumes. Delocalization of 4f and 5f orbitals is proved to be the reason for the two types of migratory properties. Since the itinerant behaviour of yttrium and actinides(III) in respect to stability constants (free energies of complex formation) is the basis for yttrium-lanthanides and lanthanides-actinides group separations, a better qualitative understanding of the mechanism involved may contribute to the development of more efficient separation procedures. (author) 6 refs.; 3 figs