Low-temperature transport properties of the filled and unfilled IrSb3 skutterudite system

Abstract

We have measured the electrical resistivity, ρ, thermoelectric power, α, and thermal conductivity, κ, of the skutterudite material IrSb3 in a temperature range from 300 down to 4 K. It is found that the electrical resistivity and thermopower decrease monotonically as the temperature is reduced to 50–60 K. Below approximately 60 K the resistivity rises in a semiconducting manner. It appears the thermopower exhibits a large phonon drag peak at around 20 K and then falls towards zero. The thermal conductivity increases rapidly as the temperature is decreased with a maximum at around 20 K, corresponding to the peak in the thermopower. We will discuss these results and compare them to higher temperature data from G. A. Slack and V. G. Tsoukala [(IrSb3) J. Appl. Phys. 76, 1635 (1994)]. We have also measured some of the so-called ‘‘filled skutterudites,’’ Ir4LaGe3Sb9, Ir4NdGe3Sb9 and Ir4SaGe3Sb9. The thermoelectric properties of these materials are considerably different than those of the unfilled sample. The thermopower is considerably lower and the resistivity is a factor of 2–4 times higher than the unfilled sample at room temperature. The thermal conductivity is markedly reduced by the filling, as much as a factor of 20 reduction for some of the systems.

High-Pressure Synthesis, Structure, and Magnetic Properties of Ge-Substituted Filled Skutterudite Compounds; LnxCo4Sb12−yGey, Ln = La, Ce, Pr, and Nd

“…Such a disorder would have an effect of decreasing the lattice thermal conductivity [10][11][12]. It is desirable to evaluate the thermal conducting and thermoelectric properties for these compounds.…”

“…Nolas et al reported the first filled skutterudite compounds containing group 14 elements in the M site, LnIr 4 Sb 9 Ge 3 , Ln = La, Nd, and Sm. In these compounds, the electrons from the guest trivalent cations compensate for the electron deficiency of the host network caused by the substitution of a group 14 element for the group 15 element [10][11][12]. We also prepared a series of Ge-substituted filled skutterudite compounds LnRh 4 Sb 9 Ge 3 , Ln = La, Ce, Pr, and Nd, using high-pressure and high-temperature reactions [13].…”

Effect of partial la filling on high-temperature thermoelectric properties of IrSb3-based skutterudite compounds

“…Therefore, the focus of research on skutterudite materials is to minimize the thermal conductivity by preparing filled skutterudite without degrading the excellent electrical properties of binary compounds. [3][4][5][6][7][8][9] In this study, the La filling effects on the phase stability and high-temperature thermoelectric properties are investigated in IrSb 3 -based skutterudite compounds. Especially, the correlation between phase stability and thermoelectric properties with La filling for IrSb 3 -based skutterudite compounds is discussed.…”

“…2 A family of compounds with the filled skutterudite structure (space group Im3), the general formula RMX 3 , where R is the rare earth element, M is the transition metal element Co, Rh, or Ir, and X is the pnicogen element such as P, As, or Sb, has been identified as a candidate for good thermoelectric materials. [3][4][5][6][7][8][9] The body-centered unit cell contains 34 atoms, and the rare earth ion fills an atomic cage formed by MX 6 octahedra, which is oversized for R ions. It is believed that the R ions rattle in the cages and therefore interact with a broad spectrum of lattice phonons, reducing their mean free paths substantially below that of the unfilled skutterudite.…”

Elastic properties of the filled and unfilled skutterudite compounds

“…Low temperature transport properties of the unfilled skutterudite systems, RhSb 3 and IrSb 3 suggest semiconducting type behavior with a narrow band gap. [10][11] The aim of the present work is to evaluate the role of the guest ions RE by means of an ultrasonic measurement. Ultrasonic measurement is a powerful tool with which to study the charge fluctuation through phonons coupled with elastic strains induced by a sound wave.…”