title: Optimization and Analysis of Thermoelectric Properties of Unfilled Co(1-x-y)Ni(x)Fe(y)Sb3 Synthesized via a Rapid Hydrothermal Procedure.
abstract: A series of nanostructured co-doped Co(1-x-y)Ni(x)Fe(y)Sb3 were fabricated using a rapid hydrothermal method at 170 °C for a duration of 12 h, followed by evacuated-and-encapsulated heating at 580 °C for a short period of 5 h. The resulting samples were characterized using powder X-ray diffraction, field emission scanning electron microscopy, bulk density, electronic and thermal transport measurements. The power factor of Co(1-x-y)Ni(x)Fe(y)Sb3 is significantly enhanced in the high-temperature region due to significant enhancement of the electrical conductivity and absolute value of thermopower. The latter arises from the onset of bipolar effect being shifted to higher temperatures as compared with the non-doped CoSb3. The room temperature thermal conductivity falls in the range between 1.22 and 1.67 W m(-1) K(-1) for Co(1-x-y)Ni(x)Fe(y)Sb3. The thermal conductivity of both the (x,y) = (0.14,10) and (0.14,12) samples is measured up to 600 K and found to decrease with increasing temperature. The thermal conductivity of the (0.14,10) sample goes down to ∼1.02 W m(-1) K(-1). As a result, zT = 0.68 is attained at 600 K. The lattice thermal conductivity is analyzed to gain insight into the contribution of various scattering processes that suppress the heat transfer through the phonons in Co(1-x-y)Ni(x)Fe(y)Sb3. The effect of the simultaneous presence of Co, Ni, and Fe elements on the electronic structure and transport properties of Co(1-x-y)Ni(x)Fe(y)Sb3 is described using the quantum mechanical tunneling theory of electron transmission among the potential barriers.
authors: Department of Physics, National Changhua University of Education , Changhua 500, Taiwan.
authors: Ahmad
authors: A
authors: Gharleghi
authors: Department of Physics, National Changhua University of Education , Changhua 500, Taiwan.
authors: Yu-Hsien
authors: YH
authors: Chu
authors: Department of Physics, National Changhua University of Education , Changhua 500, Taiwan.
authors: Fei-Hung
authors: FH
authors: Lin
authors: Department of Physics, National Changhua University of Education , Changhua 500, Taiwan.
authors: Zong-Ren
authors: ZR
authors: Yang
authors: Department of Physics, National Changhua University of Education , Changhua 500, Taiwan.
authors: Yi-Hsuan
authors: YH
authors: Pai
authors: Department of Physics, National Changhua University of Education , Changhua 500, Taiwan.
authors: Chia-Jyi
authors: CJ
authors: Liu
keywords: bipolar effects; co-doping effects; cobalt skutterudites; hydrothermal synthesis; low thermal conductivity; thermoelectrics