A Rational Approach to Solid State Synthesis—The Zintl Concept

Abstract

Abstract There are a wide variety of ternary compounds, AxMyXz, where A = alkali or alkaline earth metal, M = semimetal or main group element and X = pnictide, that have been synthesized. For example the compounds Ba3AlSb3, Ca3AlSb3, Ca3AlSb3 and Ca5Al2Sb6 have been synthesized and their structures can be understood via the Zintl formalism which can be simply stated as the octet rule for all atoms. The structures can be generally formulated as A− + [(MX)−] so that the anionic units in these examples may be written as: (Al2Sb6)12-; (AlSb3)6- chains; a (Al2Sb6)10- network; and [(AlSb9- 4) + 4Sb3- + Sb7- 3). The Zintl concept has also been applied to ternary transition metal compounds such as the lanthanum transition metal pnictides and ternary transition metal chalcogenides. These structures and their related properties can be understood in terms of cations and complex polyatomic anionic units. The Zintl concept, as it applies to ternary pnictide compounds, will be presented and its extension to ternary tra...