The effect of Cu<inf>2</inf>O nanoparticle dispersion on the thermoelectric properties of n-type skutterudites

We report the thermoelectric properties of Ba0.4Co4Sb12 and Sn0.4Ba0.4Co4Sb12 skutterudites dispersed with Cu2O nanoparticles. The samples were synthesized by ball milling and consolidated by spark plasma sintering. Dispersion of Cu2O is found to significantly influence the electrical resistivity and thermopower at high temperatures with a more pronounced effect on the electrical resistivity due to the energy filtering effect at the interface between Cu2O nanoparticles and a Ba0.4Co4Sb12 and Sn0.4Ba0.4Co4Sb12 matrix. At 573 K, the electrical resistivity of Ba0.4Co4Sb12 decreases from 5.01 ×10-5 Ωm to 2.98 ×10-5 Ωm upon dispersion of Cu2O. The dispersion of Cu2O reduces the thermal conductivity of the samples from 300 K and above by increasing the phonon scattering. The lowest observed thermal conductivity at 573 K is found to be 2.001 W mK-1 in Cu2O dispersed Ba0.4Co4Sb12 while it is 2.91 W mK-1 in the Ba0.4Co4Sb12 sample without Cu2O dispersion. Hence Cu2O dispersion plays a significant role in the thermoelectric properties and a maximum figure of merit (ZT ) ∼ 0.92 is achieved in Cu2O dispersed Ba0.4Co4Sb12 at 573 K which is more than 200% compared to the pure Ba0.4Co4Sb12 sample. The results from nanoindentation experiments show that the Cu2O dispersed sample (Cu2O + Sn0.4Ba0.4Co4Sb11.6) has a higher reduced Young's modulus (∼139 GPa) than the pure Sn0.4Ba0.4Co4Sb11.6 sample (∼128 GPa).