Аспірантура у Франції
23 березня 2012 р.
Institut Jean Lamour
uMR cnrs - Nancy Université - UPVM 7198
Département de Chimie et Physique des Surfaces et des Solides
Ecole Nationale Supérieure des Mines de Nancy
Parc de Saurupt
F-54042 NANCY Cedex, France
Title of the thesis: Identification, synthesis and characterization of Se-based complex phases for thermoelectric applications.
Energy conversion by thermoelectric effects has witnessed a resurgence of interest in the last two decades owing to the discovery of new efficient materials. Thermoelectric converters offer numerous advantages such as high reliability, no noise or the absence of gas rejection. Either cooling or electricity generation can be achieved by thermoelectric effects.
The thermoelectric efficiency of the generators is controlled by the dimensionless thermoelectric figure of merit ZT defined as ZT = (S2T)/(C.E) with T (K) the absolute temperature, S (thermopower of Seebeck coefficient, V/K), C (W/m.K) the thermal conductivity and E (W.m) the electrical resistivity. High thermoelectric efficiency is then synonymous of high ZT values at a given temperature T. Until the early 90’s, only few materials with ZT higher than 1 were known. This value is insufficient to make this technology a prospective candidate for green energy conversion.
New ideas guided the researchers over the last two decades and resulted in the discovery of new materials with ZT values above unity. Among others, crystalline materials with complex crystal structure such as Half-Heusler, skutterudite or clathrate compounds became good candidate to replace state-of-the-art materials in thermoelectric generators. Se-based compounds also constitute a worthwhile way of research to pursue. The chemical richness of these phases combined with the presence of heavy atoms constitutes desirable features that may result in high ZT values. The investigation of the thermoelectric properties of these phases is at the heart of the thesis subject we propose.
Objectives of the thesis
The candidate will synthesize and characterize different Se-based compounds with the aim at optimizing their thermoelectric properties. The crystallographic structure and chemical homogeneity of the compounds will be checked by powder x-ray diffraction, single crystal x-ray diffraction and electron-probe micro-analysis. The transport properties will be investigated over a broad temperature range (2 – 1000 K) to better assess the thermoelectric potential of these compounds. These measurements include thermopower, electrical resistivity, thermal conductivity, specific heat, Hall effect and magnetic susceptibility. These results will be complemented by neutron diffraction and inelastic neutron scattering carried out in different European centers (ILL @ Grenoble and ISIS @ Oxford). The candidate will also correlate the transport properties to electronic band structure calculations performed by our collaborators.
Laboratory: Institut Jean Lamour – CP2S – Team 204 « Thermoelectric materials », Ecole Nationale Supérieure des Mines de Nancy
Scholarship: Scholarship of the French ministry (MENRT)
Candidate: Master in solid-state physics or solid-state chemistry
Application to return by the end of April 2012 accompanied by detailed CV (including marks or GPA) and a motivation letter to: