Clathrate thermoelectrics

Clathrates represent a fascinating class of inorganic materials with a unique structural motif: 3D framework with large polyhedral cages encapsulating guest ions. Weak electrostatic interactions between the guest atoms and host clathrate framework as well as inability of guest atoms to leave cages define the exceptional properties of the clathrates. Clathrates crystallize in a dozen of different structure types, and clathrates' compositional space includes half of the periodic system. This review discusses the fundamental chemical principles of the clathrates and relates them to predicted and experimentally characterized thermoelectric properties. This review also briefly outlines other emergent applications of clathrates in the areas of gas storage, photovoltaic, and superconducting materials.