Ground state properties and thermoelectric behavior of PrFe/sub 4-x/TM/sub x/Sb/sub 12-y/Sn/sub y/ (TM = Co, Ni)

Quasi ternary filled skutterudites Pr/sub y/(Fe,Co,Ni)/sub 4/(Sb,Sn)/sub 12/ were investigated by means of temperature dependent magnetization -, specific heat -, electrical resistivity - and thermopower measurements. As non-Kramers ion in cubic environment Pr can exist in both a magnetic or a nonmagnetic ground state and crystal field effects strongly influence physical properties in an extended temperature range. Detailed investigations of Pr/sub 0.73/Fe/sub 4/Sb/sub 12/ point to antiferromagnetic order and /spl Gamma//sub 5/ as crystal field ground state. Strong electron correlations give rise to significantly enhanced masses of charge carriers, which in turn enhances the Seebeck coefficient S(T). Owing to the Fe/Ni substitution, large values of S(T) are found reaching figures of about 230 /spl mu/V/K at 425 K for Pr/sub 0.21/Fe/sub 2.5/Ni/sub 1.5/Sb/sub 12/ in combination with low thermal conductivity as expected for this class of materials. Moreover, the Fe/Ni substitution drives the system from hole- to electron-dominated transport, which is obvious considering the crossover of S(T) from positive to negative thermopower values in Pr/sub 0.1/Fe/sub 2/Ni/sub 2/Sb/sub 12/.