A.R. On the valence state of europium in alloys. W.G. The handbook of binary phase diagrams. The solubility of non electrolytes. Entmischungsverhalten der seltenen erden unter microg und 1g bedingungen.
Rare earths are well suited for the investigation of the influence of physico-chemical parameters.
Whereas the trivalent lanthanides are almost ideally miscible, alloys of bivalent and trivalent lanthanides present wide miscibility gaps in both the liquid and the solid state. They are then fully miscible with other trivalent lanthanides and with related d exp 1 -elements. Since the valence change affects the occupation of the 4f electronic layer and thereby modifies the atomic volume, it can be detected very precisely by means of magnetic as well as density measurements. A number of different experimental and theoretical studies has been performed, aimed at an accurate understanding of these valence instabilities. This change occurs then as soon as the heat of formation of a trivalent Europium alloy exceeds by this amount the heat of formation of a bivalent Europium alloy.