Thermoelectric material development. Final report

A search was made for improved TE materials that could have higher efficiency than state-of-the-art SiGe alloys used in Radioisotope Thermoelectric Generators. A new family of materials having the skutterudite structure was identified (cubic space group Im3, formula (Fe, Co, Ni)As{sub 3}). Properties of n-type IrSb{sub 3}, CoSb{sub 3}, and their solid solutions were investigated. Pt, Te, Tl, and In were used as dopants. The thermal conductivity was reduced by about 70% for the solid solutions vs the binary compounds. A maximum ZT of about 0.36 was measured on Co-rich solid solutions which is 160% improved over that of the binary compounds

LOW TEMPERATURE THERMAL CONDUCTIVITY OF TWO NATURAL DIAMONDS : ANISOTROPIC HEAT CONDUCTION IN THE BOUNDARY SCATTERING REGIME

La conductivité thermique de deux diamants naturels, de type IIa, et d'axes respectif et , a été mesurée entre 0,5 K et 20 K. La conductivité pour le diamant avec l'axe a été trouvée être environ deux fois plus grande que celle de l'autre diamant. Cette anisotropie s'accorde qualitativement avec les prédictions théoriques publiées, basées sur la focalisation des phonons.The thermal conductivity of two natural type IIa diamonds with rod axis and respectively has been measured between 0.5 K and 20 K. The conductivity for the diamond with the rod axis was found to be about double that for the other diamond. This anisotropy is in qualitative agreement with published theoretical predictions based on phonon focusing

Thermoelectric material development. Quarterly technical progress report, January 1, 1995--March 31, 1995

We have found that there is a limited range of solid solutions between the skutterudite compounds CoSb{sub 3} and RuSb{sub 2}Te (about 5% on each side). For the system (RuSb{sub 2}Te){sub x}(CoSb{sub 3}){sub 1-x}, preliminary results obtained on one n-type sample on the CoSb{sub 3}-rich side show that these alloys have good thermoelectric properties and a maximum ZT of about 0.89 was obtained at about 600 C. More experiments will be started to investigate the possibility of a broader range of miscibility in this system which would allow an even further decrease in the lattice thermal conductivity, resulting in better thermoelectric properties. IrSb{sub 3} and RuSb{sub 2}Te form a complete range of solid solutions. Hot-pressed samples in this system have shown p-type conductivity. The thermoelectric properties of these p-type alloys have been measured and results have shown that their potential for thermoelectric applications is limited mainly because of the relatively low Seebeck coefficient values for p-type materials. Efforts will be directed on preparing n-type samples of the same alloys by doping with various dopants such as Ni and Pd