Phase stability and lattice thermal conductivity reduction in CoSb3 skutterudites, doped with chalcogen atoms

Abstract

We report a significant reduction in the lattice thermal conductivity of the CoSb3 skuttertudites, doped with chalcogen atoms. Te/Se chalcogen atoms doped CoSb3 skutterudite samples (Te0.1Co4Sb12, Se0.1Co4Sb12, Te0.05Se0.05Co4Sb12) are processed by ball milling and spark plasma sintering. X-ray diffraction data combined with energy dispersive X-ray spectra indicate the doping of Te/Se chalcogen atoms in the skutterudite. The temperature dependent X-ray diffraction confirms the stability of the Te/Se doped CoSb3 skutterudite phase and absence of any secondary phase in the temperature range starting from 300 K to 773 K. The Raman spectroscopy reveals that different chalcogen dopant atoms cause different resonant optical vibrational modes between the dopant atom and the host CoSb3 skutterudite lattice. These optical vibrational modes do scatter heat carrying acoustic phonons in a different spectral range. It was found that among the Te/Se chalcogen atoms, Te atoms alter the host CoSb3 skutterudite lattice vibrations to a larger extent than Se atoms, and can potentially scatter more Sb related acoustic phonons. The Debye model of lattice thermal conductivity confirms that the resonant phonon scattering has important contributions to the reduction of lattice thermal conductivity in CoSb3 skutterudites doped with Te/Se chalcogen atoms. Lattice thermal conductivity ∼ 0.9 W/mK at 773 K is achieved in Te0.1Co4Sb12 skutterudites, which is the lowest value reported so far in CoSb3 skutterudites, doped with single Te chalcogen atom.

Effect of Pb Filling and Synthesis Pressure Regulation on the Thermoelectric Properties of CoSb3

“…In the Raman peaks range of 80–200 cm –1 , six Raman peaks were observed. Separate Raman peaks due to Pb and Te doping were not observed, the result is similar to the study by Battabyal et al The A g energy mode of Pb 0.2 Co 4 Sb 11.5 Te 0.5 prepared by 1.5 GPa is higher than that of Pb 0.2 Co 4 Sb 11.5 Te 0.5 prepared by 3 and 3.5 GPa, which is presumably due to the higher synthesis pressures can increase the filling ratio of Pb and then make Sb–Sb bond longer. From the analysis of SEM images, we have found that the sample synthesized under 3.5 GPa have smaller grain size.…”

“…According to the polarization dependence, these Raman peaks have been identified to different symmetry modes. The corresponding results are compared with earlier theoretical calculations and experimental studies . In the Raman peaks range of 80–200 cm –1 , six Raman peaks were observed.…”

“…The corresponding results are compared with earlier theoretical calculations 15 and experimental studies. 16 In the Raman peaks range of 80−200 cm −1 , six Raman peaks were observed. Separate Raman peaks due to Pb and Te doping were not observed, the result is similar to the study by Battabyal et al 16 The A g energy mode of Pb 0.2 Co 4 Sb 11.5 Te 0.5 prepared by 1.5 GPa is higher than that of Pb 0.2 Co 4 Sb 11.5 Te 0.5 prepared by 3 and 3.5 GPa, which is presumably due to the higher synthesis pressures can increase the filling ratio of Pb and then make Sb−Sb bond longer.…”

Impact of noble-gas filler atoms on the lattice thermal conductivity of CoSb3 skutterudites: first-principles modelling

“…. 18 Frequency spectra of the averaged modal three-phonon interaction strengths of XeCo8Sb24 as defined in Eq. 12 in the text.…”

“…[10,11] However, CoSb3 is chemically very flexible and is amenable both to doping the host framework, e.g. with transition metals [13,14] and chalcogenides, [14] and to filling the cavities with atoms including alkali and alkaline earth metals, [15,16] Group III elements, [17] chalcogens, [18] halogens, [19] transition metals [20] and rare-earth elements. [21,22].…”