Structure and physical properties of the thermoelectric skutterudites EuyFe4-xCoxSb12 -: art. no. 094411

Compounds from the solid solution EuyFe4-xCoxSb12 were synthesized and found to crystallize in the partially filled skutterudite-type structure LaFe4P12. The maximal Eu content gradually decreases from practically full occupancy y=0.83 in Eu0.83Fe4Sb12 to y=0.44 for Eu0.44Co4Sb12. As a function of Fe/Co substitution in EuyFe4-xCoxSb12 the magnetic transition temperature decreases from 84 K for Eu0.83Fe4Sb12 to 8 K for Eu0.44Co4Sb12. At lower Eu content, Eu0.2Co4Sb12, long-range magnetic order disappears. Concomitantly, the Eu valence changes from almost divalent Eu in Eu0.83Fe4Sb12 to nuapproximate to2.6 for Eu0.2Co4Sb12. The transition metal exchange Fe/Co reduces the number of free carriers and causes a crossover of the electronic transport from a hole conductivity regime into electron dominated behavior. Thermoelectric properties change accordingly.