Место издания:University of Bayreuth Bayreuth, Germany
Первая страница:L16
Аннотация:The focus of the work presented here is on linear intergrowth and layered structures combining the fragments of ordered intermetallics with structural units of other nature. Ordered polar intermetallic compounds in themselves are fascinating objects both due to their incredible structural diversity and the variety of unconventional and potentially useful physical properties. Quite often they feature complicated structure motifs and convoluted bonding patterns, as well as complicated structure-property relationships. Furthermore, if a 3D intermetallic system is infused with non-metallic fragments, new possibilities arise. This concept is exploited here using two types of compounds as examples: i) metal-rich mixed group 10 – group 13 chalcogenides and pnictides based on the Cu3Au-type fragments; ii) intergrowth structures based on the LaOAgS structure type.
The first type of compounds can be regarded as linear intergrowth structures and is based on the group 10 – group 13 intermetallic fragments of the Cu3Au structure type alternating with group 10 metal – chalcogen or pnictogen fragments of the Cu2Sb, Li¬2O, and PtHg2 types. The second type of compounds is a layered one and features fairly simple atomic arrangement that consists of two alternating anti-isotypic (PbO- and FeS-type) layers. It is, in fact, its own anti-type and thus is a very convenient object for crystal chemical analysis. The compounds that we are interested in combine non-metallic (rare earth or alkali earth and fluorine or oxygen) and intermetallic (e.g. triel-tetrel: Al-Ge, Al-Si; d-metal-pnictogen: Zn-Sb, Mn-As, Mn-Sb, etc.) layers.
Crystal and electronic structures of both types of compounds, bonding schemes, as well as structure-property relationships are discussed in the presentation. Of particular note are synthetic difficulties: the synthesis of not only phase-pure, but even the samples featuring significant amount of these compounds is severely hindered. However, the use of the miniscule amounts of iodine during high temperature synthesis works wonders, although the exact nature of its effect is yet to be determined.