Polaronic transport and thermoelectricity in Fe$_{1-x}$Co$_x$Sb$_2$S$_4$ ($x$ = 0, 0.1, and 0.2)

Yu Liu; Chang-Jong Kang; Eli Stavitski; Qianheng Du; Klaus Attenkofer; G. Kotliar; C. Petrovic

doi:10.1103/PhysRevB.97.155202

paper

Polaronic transport and thermoelectricity in Fe $_{1 - x}$ Co $_{x}$ Sb $_{2}$ S $_{4}$ ( $x$ = 0, 0.1, and 0.2)

arXiv:1804.07776 · doi:10.1103/PhysRevB.97.155202

Abstract

We report a study of Co-doped berthierite Fe $_{1 - x}$ Co $_{x}$ Sb $_{2}$ S $_{4}$ ( $x$ = 0, 0.1, and 0.2). The alloy series of Fe $_{1 - x}$ Co $_{x}$ Sb $_{2}$ S $_{4}$ crystallize in an orthorhombic structure with the Pnma space group, similar to FeSb $_{2}$ , and show semiconducting behavior. The large discrepancy between activation energy for conductivity, $E_{ρ}$ (146 $\sim$ 270 meV), and thermopower, $E_{S}$ (47 $\sim$ 108 meV), indicates the polaronic transport mechanism. Bulk magnetization and heat capacity measurements of pure FeSb $_{2}$ S $_{4}$ ( $x$ = 0) exhibit a broad antiferromagnetic (AFM) transition ( $T_{N}$ = 46 K) followed by an additional weak transition ( $T^{*}$ = 50 K). Transition temperatures ( $T_{N}$ and $T^{*}$ ) slightly decrease with increasing Co content $x$ . This is also reflected in the thermal conductivity measurement, indicating strong spin-lattice coupling. Fe $_{1 - x}$ Co $_{x}$ Sb $_{2}$ S $_{4}$ shows relatively high value of thermopower (up to $\sim$ 624 $μ$ V K $^{- 1}$ at 300 K) and thermal conductivity much lower when compared to FeSb $_{2}$ , a feature desired for potential applications based on FeSb $_{2}$ materials.

Polaronic transport and thermoelectricity in Fe1−x​Cox​Sb2​S4​ (x = 0, 0.1, and 0.2)

Abstract

Polaronic transport and thermoelectricity in Fe $_{1 - x}$ Co $_{x}$ Sb $_{2}$ S $_{4}$ ( $x$ = 0, 0.1, and 0.2)