Alloys of two B sub-group elements

In systems containing two B sub-group metals the partially covalent character of these elements leads to a still more pronounced tendency towards the formation of definite chemical compounds. When 

Compounds with the zincblende or wurtzite structure are commonly formed when one element belongs to the nth. and the other to the (8—rc)th B sub-groups. In these structures each atom is bound to four neighbours by purely covalent bonds and it is necessary that the number of valency electrons available for the formation of these bonds should average four per atom. It is not, however, necessary that these should be contributed equally by the atoms of the two types, and the condition is therefore satisfied if these atoms are related in the manner indicated. Some B-B compounds with the zincblende and wurtzite structures are shown in table 13.09. These structures are not, of course, confined to systems of the type B-B we have encountered numerous examples of their occurrence in compounds of quite other kinds. 

BeSe ZnSe CdSe HgSe AlSb GaSb InSb 

This completes our discussion of the three principal classes into which we have divided the alloy systems. As a summary, a condensed survey of the chief structural characteristics of these classes is given in table 13.10. The remaining class of alloys to be considered is that embracing the interstitial structures. These systems, however, differ materially from the alloy systems so far discussed, and a description of them is accordingly deferred until later in the chapter ( 13 37). 

Wide range of solid so-, lution. Superstructures Laves phases 

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