Cerium filling and doping of cobalt triantimonide

Abstract

We have fabricated and studied the structural, magnetic, and transport properties of filled skutterudites of the form Ce{sub y}Fe{sub 4{minus}x}Co{sub x}Sb{sub 12} with 0{lt} y{lt}1 and x=3.25 and 4. For samples containing 100{percent} Co, Ce can be inserted into approximately 10{percent} of the voids in the skutterudite structure. It is shown that the rare earth is trivalent and dopes the host CoSb{sub 3} n-type. With substitution of Fe for Co the void occupancy by Ce increases. The thermal conductivity is strongly depressed even at small (5{percent}) rare-earth filling fractions, and is further degraded by substitution of Fe for Co. Although the electron mobility in n-type samples is smaller than the hole mobility in p-type samples, due to their large electron masses the Seebeck coefficient in n-type material maintains large values at high electron concentrations. {copyright} {ital 1997} {ital The American Physical Society}