M. Puyet

High temperature transport properties of partially filled CaxCo4Sb12 skutterudites

Partially filled CoSb3 skutterudite compounds are emerging materials for thermoelectric energy conversion at high temperature. CaxCo4Sb12 with different Ca contents has been prepared by the conventional metallurgical route. The temperature dependences of the electrical resistivity, Seebeck coefficient, and thermal conductivity have been measured on these compounds in the 300–800 K temperature range. These measurements have identified Ca as being a true n-type filler atom and offer, for this family of skutterudite, several valuable insights into the potential of Ca to provide good thermoelectric performance.

Improved thermoelectric properties in double-filled Cey∕2Yby∕2Fe4−x(Co∕Ni)xSb12 skutterudites

We have investigated the thermal and electrical properties of filled skutterudites belonging to the series Ce1−zYbzFe4Sb12 and Cey∕2Yby∕2Fe4−x(Co∕Ni)xSb12, as well as their potential for thermoelectric power generation. In the first series, increasing the Yb fraction decreases the resistivity and thermopower. These effects are related to the variations of valence of Yb with the Yb fraction (from 2.2 in Yb0.92Fe4Sb12 to 2.7 in Ce0.85Yb0.05Fe4Sb12). The power factor is increased in Ce0.40Yb0.53Fe4Sb12 while the thermal conductivity is reduced and this leads to an improved figure of merit in this compound when compared to Ce0.85Fe4Sb12. Co or Ni substitution was used to tune the carrier concentration and improve the power factor: we measure a ZT=0.5 at 500K in Ce0.44Yb0.32Fe3.02Co0.98Sb12 and an extrapolation leads to ZT=0.95 at 800K, which is close to state-of-the-art Ce0.28Fe1.52Co2.48Sb12 although the composition is far from being optimized. Double filling happens to be a promising path to provide good th...

Beneficial effect of Ni substitution on the thermoelectric properties in partially filled CayCo4−xNixSb12 skutterudites

We have investigated the influence of nickel doping in a series of n-type CoSb{sub 3} skutterudite materials partially filled with Ca. The electrical resistivity, thermopower, and thermal conductivity have been measured in the 300-800 K temperature range on Ca{sub y}Co{sub 1-x}Ni{sub x}Sb{sub 12} compounds prepared by a powder metallurgy route. The chemical composition and structure have been analyzed by electron probe microanalyses and x-ray diffraction, respectively. It was found that the presence of nickel substantially decreases the electrical resistivity without any detrimental effect on the thermopower, resulting in an improvement of the power factor. The dimensionless thermoelectric figure ZT increases with increasing temperature and reaches a maximum value of 1 at 800 K.

Beneficial effect of Ni substitution on the thermoelectric properties in partially filled Ca{sub y}Co{sub 4-x}Ni{sub x}Sb{sub 12} skutterudites

We have investigated the influence of nickel doping in a series of n-type CoSb{sub 3} skutterudite materials partially filled with Ca. The electrical resistivity, thermopower, and thermal conductivity have been measured in the 300-800 K temperature range on Ca{sub y}Co{sub 1-x}Ni{sub x}Sb{sub 12} compounds prepared by a powder metallurgy route. The chemical composition and structure have been analyzed by electron probe microanalyses and x-ray diffraction, respectively. It was found that the presence of nickel substantially decreases the electrical resistivity without any detrimental effect on the thermopower, resulting in an improvement of the power factor. The dimensionless thermoelectric figure ZT increases with increasing temperature and reaches a maximum value of 1 at 800 K.

Beneficial effect of Ni substitution on the thermoelectric properties in Ca y Co 4-x Ni x Sb 12 skutterudites

We have investigated the influence of nickel doping in a series of n-type CoSb{sub 3} skutterudite materials partially filled with Ca. The electrical resistivity, thermopower, and thermal conductivity have been measured in the 300-800 K temperature range on Ca{sub y}Co{sub 1-x}Ni{sub x}Sb{sub 12} compounds prepared by a powder metallurgy route. The chemical composition and structure have been analyzed by electron probe microanalyses and x-ray diffraction, respectively. It was found that the presence of nickel substantially decreases the electrical resistivity without any detrimental effect on the thermopower, resulting in an improvement of the power factor. The dimensionless thermoelectric figure ZT increases with increasing temperature and reaches a maximum value of 1 at 800 K.

Thermoelectric properties of the new skutterudites (Ce-Yb)/sub y/Fe/sub 4-x/(Co/Ni)/sub x/Sb/sub 12/

Polycrystalline p-type and n-type skutterudites belonging to the family (Ce-Yb)/sub y/Fe/sub 4-x/(Co/Ni)/sub x/Sb/sub 12/ have been synthesized using a standard arc-melting method and subsequent annealing. They have been characterized using X-ray diffraction (XRD) and electron probe microanalysis (EPMA). Yb valence state was estimated using X-ray absorption spectroscopy (XAS) at the Yb L/sub 3/ edge which evidences an evolution of the Yb mixed valence state in the various series. Thermoelectric properties have been investigated between 120K and 800K by mean of thermopower and electrical conductivity measurements.

Synthesis and thermoelectric properties of new partially filled Ca/sub x/Co/sub 4/Sb/sub 12/ skutterudites

Partially filled R/sub x/Co/sub 4/Sb/sub 12/ skutterudite compounds are particularly interesting for thermoelectric energy conversion at high temperature. This paper is devoted to the study of new skutterudite materials, partially filled with calcium. The Ca/sub x/Co/sub 4/Sb/sub 12/ compounds (0 /spl les/ x /spl les/ 0.6, nominal) have been prepared by a conventional metallurgical route. They have been characterized by electron probe microanalysis, x-ray and neutron diffraction. The filling fraction limit was found to be x /spl sim/ 0.2. Rietveld refinement on neutron diffraction data proved Ca atoms are inserted in the voids of the skutterudite structure. The temperature dependences of the electrical resistivity, Seebeck coefficient and thermal conductivity have been measured within the 300-800 temperature range. The influence of Ca content on the transport properties is discussed. A ZT value of 0.45 was achieved at 800 K with non-optimised Ca/sub 0.2/Co/sub 4/Sb/sub 12/ skutterudite.