Reactivity thermoelectric clathrate compounds in interaction with components of the air

  The project aims to address the fundamental problems of solid state chemistry - revealing the fundamental regularities of the reactivity of crystalline phases in reactions with air components and processes of formation of oxide layers (coatings) for new materials. The general problem is solved for the new crystals of clathrate compounds as promising thermoelectric materials of new generation.

  Application of new clathrate thermoelectric materials is limited by the fact that their surface is unstable in operation. In this regard, the general approach to the development of materials that are suitable for direct conversion of solar thermal energy is the choice of compositions and conditions for the formation of the thin oxide layer with passivating properties. This should be maintained unique properties of these materials - high electrical conductivity with low thermal conductivity, causing their application prospect in the new generation of thermoelectric devices .

  Experimentally and theoretically the following tasks:

1. Synthesis crystal clathrate compounds given composition and preparation of atomically clean surfaces;

2. Theoretical and experimental study of oxidation and segregation phenomena in the oxide and the boundary layers of the crystal;

3. Determination of thermodynamic and kinetic conditions for forming a predetermined oxide layer thickness and composition, as a prospective passivation coatings.

  In a pilot study varied parameters are crystal composition and physico-chemical conditions of formation of the oxide layer: temperature, duration of the process, the composition of the gaseous medium. From the complex probe microscopy techniques, XPS, etc. UPES) studied the structure of the oxide layer (thickness , surface roughness , denseness , the degree of crystallinity , etc. ), its composition and distribution of components across the layer and the surface layers of crystals. Particular attention will be paid to segregation ( ie enrichment of one component of the surface of the crystal) in its connection with the passivation effect.   Theoretical study involves quantum-chemical modeling of the oxidation products and the comparison of their relative stability. As a result of the regularities in the formation of thin oxide layers for clathrate compounds with passivating properties.

 

KEYWORDS

thermoelectric materials , reactivity, energy conversion , protective coatings , clathrate compounds