ИСТИНА

Inorganic clathrates comprise a vast family of inclusion compounds that feature sequestering of guest atoms or molecules in large cavities of tracery frameworks. Ten varieties of their crystal structures are known to scientists, each delighting by their aesthetical beauty. First discovered as “anomalous ice” by Davy and then found in many hydrates as well as in solid-state compounds of p-elements, clathrates have long remained a fascinating object of scientific curiosity. It was only in the middle of the 1990th that Slack realized that clathrates, with their profound separation of host and guest substructures, might provide a base for creating thermoelectric materials of a new generation. Thermoelectric materials convert heat into electrical power or, vice versa, electrical power into a temperature gradient. The efficiency of the conversion rests with the ability of a compound to provide an efficient transport of charge carriers along with a poor transport of heat. Two weakly interacting substructures of clathrates, a host and guests, are ideally suited for decoupling charge carriers and heat-carrying phonons, leading to a property of a phonon glass and electronic crystal. In this lecture, we will focus on cationic clathrates and clathrate-like compounds that exhibit positively charged frameworks of different chemical nature and structure, which trap electronegative anions to form complex symmetric patterns. Their crystal and electronic structures as well as structure-related thermoelectric properties will be the central points of discussion.