Synthesis of potential new Zintl phases

摘要

This work has shown that addition of a transition metal interstitial atom, Z, into Ae(sub 5)Tt(sub 3)Z (Ae = Sr, Ba; Tt = Sn, Pb) does not stabilize a Mn(sub 5)Si(sub 3)-type structure as in the Ca -- Pb system. The products that resulted from these reaction were invariably the same as those seen in the binary systems. Apparently, the Cr(sub 5)B(sub 3), Pu(sub 31)Pt(sub 20), and W(sub 5)Si(sub 3) structure types found in these systems do not have holes in their structures which might allow an interstitial atom to be incorporated into the structure. It is evident that the inverse Cr(sub 5)B(sub 3) structure of La(sub 3)Sn(sub 3)InGe, La(sub 3)Sn(sub 2)In(sub 2)Ge, and La(sub 3)SnIn(sub 3)Ge characterized in this work is seen when the composition yields compounds that will be either electron deficient as are La(sub 3)In(sub 4)Ge, La(sub 3)SnIn(sub 3)Ge, and La(sub 3)Sn(sub 3)In(sub 2)Ge or electron precise as is La(sub 3)Sn(sub 3)InGe. The structure is destabilized if more electrons are added to the system. This helps to explain why La(sub 3)Sn(sub 4)Ge does not exhibit this structure type. In other words this structure is more stable when electron deficient. Perhaps as more electrons are added to the system and more negative charge accumulates on the In/Sn site, anti-bonding levels become populated or electrostatic repulsions contribute to the destabilization of the anionic network.