Résumé
This thesis concerns the study of complex antimonides with Th3P4 structure type and their potential as p-type materials for thermoelectric power generation. Such materials are characterized by the figure of merit ZT = α2T/ρκ, where α is the Seebeck coefficient, ρ the electrical resistivity and κ the thermal conductivity. R4Sb3 binary compounds (R = La, Ce, Sm and Yb) and ternary Yb4-xR'xSb3 (R = La, Sm, Ce and Eu) and Yb4Sb3-yXy (X = Se, Te, As, Bi and I) have been synthesized by high temperature reaction and crystallize in the anti-Th3P4 structural type (I-43d No. 220). The structural and chemical characterizations were performed by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with the energy dispersive X-ray spectrometry (EDS). Powders have been densified by spark plasma sintering (SPS) at 1573K under a pressure 100Mpa. Transport properties were measured from room temperature up to 1273K. They indicate that the conduction of binary compounds is dominated by electrons and show a low Seebeck coefficient. Only Yb4Sb3 shows a typical metallic behavior with p-type conduction. Magnetic susceptibility measurements performed on this compound indicates that ytterbium is mainly divalent. So by substituting this element by other trivalent rare earths or by substituting antimony by chalcogens, we have improved high temperature thermoelectric properties thus making these materials promising for thermoelectric generation of electricity.