Intermetallic compounds Laves phases

Zintl phases an introduction. The Zintl phases are a large number of substances which in a way may represent a bridge, a transition, between the ionic and the intermetallic compounds. The expression Zintl Phases was introduced by Laves (1941) in recognition of the work carried out by E. Zintl. 

From an experimental point of view, it appears that the resonant f level is the best starting hypothesis for most U, Np and Pu compounds. Only in some cases of strong hybridization (particularly for Laves phase and AuCua-type structure intermetallics) it will broaden into true bands and we shall try to give criteria for itinerant magnetism. 

There are several dozen metallic AB2 compounds called Laves phases that are superconducting they have either cubic or hexagonal crystal structures. Some have critical temperatures above 10 K and high upper critical magnetic fields Bc2- For example, Zri/2Hfi/2V2 has rc = 10.1K, B 2 = 24 T, and a compound with a different Zr/Hf ratio has similar and Bc2 values with the critical current density Jc 4 X 10 A/cm. These materials also have the advantage of not being as hard and brittle as some other intermetallics and alloys with comparable transition temperatures. 

At present a large variety of solid compounds are called Zintl phases. The name Zintl phase was introduced by Laves According to Laves, Zintl phases are those intermetallic compounds which crystallize in typical non-metal crystal structures. For these compounds one expects an ionic contribution to the chemical bond. This definition has been extended to a large number of solid compounds formed by alkali or alkaline earth metals with metallic or semimetallic elements of the fourth, fifth and partly third group of the Periodic Table for which common structural and bonding properties have been found. The crystal structures and chemical properties of these compounds have been studied extensively . ... 

Table 2.2. Hydrogen-induced amorphization of several types of the AB2 type intermetallic compounds with C15 structure (Laves phase RM2)...

Almost 100 actinide intermetallic compounds of this stoichiometry are already known. Most of them appear as Laves phases which are formed of actinides with transition metals, A1 or Zn. 

Those tellurium atoms that are located in the center of the cluster molecules tend to bond to a large number of copper atoms. In some compounds, the copper atoms themselves form polyhedra, described as Frank-Kasper polyhedra [62]. In these cases, the clusters consist of interpenetrating Frank-Kasper polyhedra, which are [34b, 63] well known from a number of intermetallic phases (e.g.. Laves phases). 

---