Improvement of thermoelectric performance for Te-doped CoSb3 by higher synthesis pressure

Skutterudite Co4Sb11.5Te0.5 compounds with bcc crystal structure were prepared by high pressure and high temperature (HPHT) method. HPHT is highly suited to produce bulk ultrafine-grained and polycrystalline materials. X-ray diffraction and scanning electron microscopy (SEM) showed that single-phase CoSb3 with fine grain size could be quickly synthesized under high pressure. The separate optimizing of the crystal structure and electron structure could be realized by changing the synthesis pressure. In this paper, the higher synthesis pressure was used to reduce electrical resistivity and thermal conductivity of Co4Sb11.5Te0.5 compounds. In comparison with 1.5 GPa synthesized Co4Sb11.5Te0.5, 1.8 GPa synthesized Co4Sb11.5Te0.5 showed a reduction of the thermal conductivity up to 46%. Finally, a dimensionless thermoelectric figure of merit (ZT) of 0.92 at 710 K was achieved for n-type Co4Sb11.5Te0.5 synthesized at 1.8 GPa.