Rare earth alloying systematics: Thallium alloys, a review

The data in the literature relevant to the intermediate phases and to the state diagrams of the R-Tl systems (R ≡ rare earth) are analysed and discussed in connection with the methodologies applied to the study of the alloy constitution. On the basis of the various data available, a number of values for the characteristic constants of the existing phases have been assessed: these values include the melting, peritectic and eutectic temperatures, the enthalpies of formation, the lattice parameters, etc. The trends of these values, in some cases expressed as reduced parameters, are discussed. The regularities of these trends and their applicability to the optimization and prediction of phase equilibria data are shown. The promethium-thallium and the "misch metal"-thallium phase diagrams are calculated and serve as specific examples. It can be seen, moreover, that all these regularities can be included in a systematic description of the general rare earth alloying behaviour: particular attention is given to the analogies between indium and thallium alloys. © 1988.