Melting point trend in the binary alkaline earth metal alloys

The very high thermal stability of compounds with the elements representative of the 15th to 16th groups such as the antimonides, tellurides, etc. may be underlined. 

System Ca compounds Sr compounds Ba compounds Eu compoimds Yb compoimds 

These data may be compared with those typical of more electronegative elements of these groups (for instance, CaO 2600°C, BaO 2010°C, BaSe 1780°C, Eu203 2300°C, EuS 2200°C, Ca3N2 1450°C, Ba3P2 1340°C, CaC2 2200°C, CaSi 1325°C). 

A clear indication of the various intermediate phase stability may be obtained from the values of their Afi (AfG). The enthalpies of formation, in the liquid and in the solid state, of divalent metal alloys with Pb, as a typical element in the p-block, have been measured, and their trend discussed, by Sommer et al. (2006). The most exothermic values observed, for instance, in the Ca-Pb and Ba-Pb systems, correspond (for the solid compounds, in kJ/mol of atoms, at 300 K) to — 62 2 (for Ca2Pb) and —13 2 (for BaPb). A relevant compound forming tendency was observed also for the liquid alloys, for which the association model (see 3.2) was successfully applied confirming the existence of strong chemical short-range order. 

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