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Published: 2003

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Zintl phases with general composition AmEn are formed by complete charge transfer from the electropositive metal A (alkali, alkaline earth, or rare earth) to the post transition metal E. The chemical bonding in such semiconducting phases is characterized by localized bonds and is mostly governed by the valence electron concentration (VEC). Various new ternary compounds of the system Na-Zn-Sn, which are presented in the first part of this work, illustrate this principle. By successive variation of the Zn- and Na-content within Sn-rich Na stannides the obtained phases feature typical structure motifs expected from the adjusted VEC. In contrast to that delocalized electrons are simultaneously present in polar intermetallic phases. The transition between the two classes of intermetallic compounds is fluent and also intimately coupled to other factors, such as packing efficiency, Madelung energy, and the interactions between cations and anions. In this context substitution experiments in alkaline earth bismuthides and stannides were carried out not only by changing the VEC but also by successive substitution of the cations. Stabilizing cation-anion interactions were discovered to be of increased importance in such phases. The interplay between localized and delocalized states in those compounds also hints at the superconductive property, which was confirmed by magnetic measurements. The herein reported compounds, obtained by the substitution approach and the Zintl concept, reflect the many different structure governing factors in Zintl phases and at their border. The characterization involved X-ray diffraction, EDX, thermal analysis, and magnetic measurements. DFT Band structure calculations contributed to the understanding of structure-property relationships which often go beyond the grasp of the Zintl concept.