Binary phase diagrams of the rare earth metals with zinc: the Tb-Zn, Ho-Zn and Er-Zn systems

The phase diagram of the Er –Zn system has been experimentally investigated over its whole composition range by using differential thermal analysis, X-ray diffraction, optical and scanning electron microscopy, and electron probe microanalysis. Seven intermetallic phases have been found and their crystal structure confirmed, namely ErZn, ErZn , ErZn , Er Zn , ErZn , Er Zn , and 2 3 12 58 5 2 17 ErZn12. Four eutectic reactions occur. A degenerate invariant effect has been found in the Zn-rich region. The results obtained in this investigation have been used, together with those of other previously studied rare earth –Zn systems, to predict the constitutional properties of the Tb–Zn and Ho–Zn systems, taking into account that the alloying behaviour of the different rare earths with the same element varies according to systematic patterns. The predicted phase diagrams of the Tb–Zn and Ho–Zn systems are compared with selected equilibria experimentally determined by analysing a few key compositions.