A Rational Approach to Solid State Synthesis—The Zintl Concept

Abstract

There are a wide variety of ternary compounds, A_xM_yX_z, 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 [(AlSb^9- ₄) + 4Sb^3- + Sb^7- 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 transition metal pnictides will be discussed.

Key Words:

• Zintl
• ternary
• solid slate chemistry
• transition metal ternary compounds
• magnetic semiconductors
• new materials