  Novel filled skutterudites EpyNi4Sb12-xSnx (Ep = Ba and La) have been
prepared by arc melting followed by annealing at 250C, 350C and 450C up to 30
days in sealed quartz vials. A maximum filling level of y = 0.93 and y = 0.65
was achieved for the Ba and La filled skutterudite, respectively. Single-phase
samples with the composition Ni4Sb8.2Sn3.8, Ba0.42Ni4Sb8.2Sn3.8 and
Ba0.92Ni4Sb6.7Sn5.3 were employed for measurements of the physical properties
i.e. temperature dependent electrical resistivity, Seebeck coefficient and
thermal conductivity.
  Resistivity data showed a crossover from metallic to semiconducting
behaviour. The corresponding gap width was extracted from maxima in the Seebeck
coefficient data as a function of temperature. Temperature dependent single
crystal X-ray structure analyses (at 100 K, 200 K and 300 K) revealed the
thermal expansion coefficients, Einstein and Debye temperatures for two
selected samples Ba0.73Ni4Sb8.1Sn3.9 and Ba0.95Ni4Sb6.1Sn5.9. These data
compare well with Debye temperatures from measurements of specific heat (4.4 K
< T < 200 K).
  Several mechanical properties were measured and evaluated. Thermal expansion
coefficients are 11.8.10-6 K-1 for Ni4Sb8.2Sn3.8 to 13.8.10-6 K-1 for
Ba0.92Ni4Sb6.7Sn5.3. Room temperature Vicker's hardness values (up to a load of
24.5 mN) vary within the range of 2.6 GPa to 4.7 GPa. Severe plastic
deformation (SPD) via high-pressure torsion (HPT) was used to introduce
nanostructuring. Physical properties before and after HPT were compared,
showing no significant effect on the material's thermoelectric behaviour.
