Thermoelectric Properties of Some Phosphide Skutterudite Materials

Abstract

The synthesis and thermoelectric properties of CoP3, CeFe4P12 and CeRu4P12 have been investigated. These compounds were made by recrystallization from Sn flux. The samples were analyzed by x-ray diffraction and electron microprobe analysis for phase purity. Electrical resistivity and Seebeck coefficient measurements showed that all three compounds are p-type semiconductors, in agreement with theoretical predictions and previous literature results. The large difference between the thermal conductivity of the binary and filled compounds can be primarily attributed to the additional phonon scattering by Ce atoms rattling inside the empty cages. The properties of the phosphide compounds are compared to their antimonide analogs and discussed in order to obtain further insights into the transport properties of skutterudite materials. Guidelines for optimizing thermoelectric properties of this class of compounds are also provided.

Preparation and thermoelectric properties of CeFe4As12

“…3 Both compounds exhibit semiconducting behavior, in agreement with other experimental results 4 -7 and theoretical calculations. [8][9][10] In comparing the properties of these compounds to their arsenide and antimonide analogs, no precise trend can be established from the data of only a few available samples.…”

“…This suggests that this material may be a narrow band gap semiconductor similar to CoP 3 . 3 Nonstoichiometry can also play a role in determining the electrical properties of this compound. It is to be noted that the magnitude of the resistivity of CeFe 4 As 12 was nearly the same as that of CeFe 4 Sb 12 .…”

X-ray Study with Synchrotron Radiation for Filled Skutterudite CeRu4As12at Ambient Pressure and at High Pressures

“…8,9 The thermal conductivities in CeRu 4 P 12 and CeRu 4 Sb 12 are 86 and 42 mW/cmK, respectively and show weak temperature dependence. 8 The thermal conductivity of the phosphide is about two times that of the antimonides.…”

“…8,9 The thermal conductivities in CeRu 4 P 12 and CeRu 4 Sb 12 are 86 and 42 mW/cmK, respectively and show weak temperature dependence. 8 The thermal conductivity of the phosphide is about two times that of the antimonides. As mentioned above, CeRu 4 As 12 is the Kondo semiconductor with a small activation energy of 50 K. 5 The thermal equivalent isotropic parameter (B eq ) of Ce in CeRu 4 As 12 is large, 1.30Å…”

“…7 The filled skutterudites CeRu 4 X 12 (X = P and Sb) exhibit remarkable thermoelectric properties. 8,9 Previously, the powder xray diffractions of CeRu 4 X 12 (X = P and Sb) have been studied with synchrotron radiation at high pressures.…”