Ba-filled Ni-Sb-Sn based skutterudites with anomalously high lattice thermal conductivity

Werner Paschinger, Gerda Rogl, Andrij Grytsiv, Herwig Michor, Patrick Heinrich, Helmut Müller, Stephan Puchegger, Benedikt Klobes, Raphael P. Hermann, Marius Reinecker, C. Eisenmenger-Sittner, Pavel Broz, Ernst Bauer, Gerald Giester, Michael Zehetbauer, Peter Franz Rogl

Novel filled skutterudites BayNi4Sb12-xSnx (ymax = 0.93) have been prepd. by arc melting followed by annealing at 250, 350 and 450 °C up to 30 days in vacuum-sealed quartz vials. Extension of the homogeneity region, solidus temps. and structural investigations were performed for the skutterudite phase in the ternary Ni-Sn-Sb and in the quaternary Ba-Ni-Sb-Sn systems. Phase equil. in the Ni-Sn-Sb system at 450 °C were established by means of Electron Probe Microanal. (EPMA) and X-ray Powder Diffraction (XPD). With rather small cages Ni4(Sb,Sn)12, the Ba-Ni-Sn-Sb skutterudite system is perfectly suited to study the influence of filler atoms on the phonon thermal cond. Single-phase samples with the compn. Ni4Sb8.2Sn3.8, Ba0.42Ni4Sb8.2Sn3.8 and Ba0.92Ni4Sb6.7Sn5.3 were used to measure their phys. properties, i.e. temp. dependent elec. resistivity, Seebeck coeff. and thermal cond. The resistivity data demonstrate a crossover from metallic to semiconducting behavior. The corresponding gap width was extd. from the maxima in the Seebeck coeff. data as a function of temp. Single crystal X-ray structure analyses at 100, 200 and 300 K revealed the thermal expansion coeffs. as well as Einstein and Debye temps. for Ba0.73Ni4Sb8.1Sn3.9 and Ba0.95Ni4Sb6.1Sn5.9. These data were in accordance with the Debye temps. obtained from the sp. heat (4.4 K < T < 140 K) and Mossbauer spectroscopy (10 K < T < 290 K). Rather small atom displacement parameters for the Ba filler atoms indicate a severe redn. in the "rattling behavior" consistent with the high levels of lattice thermal cond. The elastic moduli, collected from Resonant Ultrasonic Spectroscopy ranged from 100 GPa for Ni4Sb8.2Sn3.8 to 116 GPa for Ba0.92Ni4Sb6.7Sn5.3. The thermal expansion coeffs. were 11.8 × 10-6 K-1 for Ni4Sb8.2Sn3.8 and 13.8 × 10-6 K-1 for Ba0.92Ni4Sb6.7Sn5.3. The room temp. Vickers hardness values vary within the range from 2.6 GPa to 4.7 GPa. Severe plastic deformation via high-pressure torsion was used to introduce nanostructuring; however, the phys. properties before and after HPT showed no significant effect on the materials thermoelec. behavior.

Department of Materials Chemistry, Department of Physical Chemistry, Faculty Center for Nano Structure Research, Physics of Functional Materials, Department of Mineralogy and Crystallography, Physics of Nanostructured Materials
External organisation(s)
Christian Doppler Laboratory for Thermoelectricity, Technische Universität Wien, Forschungszentrum Jülich, Masaryk University
Dalton Transactions (Print Edition): a journal of inorganic chemistry
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Publication date
Peer reviewed
Austrian Fields of Science 2012
Materials chemistry, Physical chemistry, Crystallography
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