Effect of thermal annealing on the microstructure and thermoelectric properties of nano-TiN/Co_4Sb_(11.5)Te_(0.5) composites

摘要

The microstructure and thermoelectric properties of nano-TiN (1 vol%) dispersed CO_4Sb_(11.5)Te_(0.5) skutt-erudite composites were systematically investigated after different thermal annealing time at 773 K in vacuum. Interior pores and surface bulges are formed clearly in the annealed sample. After 120 h annealing, the porosity of the sample increases by 10 %. However, the elemental composition and the phase composition remain stable after thermal annealing. The electrical conductivity and the thermal conductivity simultaneously decline due to the higher porosity in the annealed sample, but the thermal conductivity reduces more remarkably. In addition, the Seebeck coefficient changes slightly after annealing. As a result, the ZT value increases by 20 % after 120 h annealing. The results show that the annealing treatment can improve the ZT value of the TiN/CO_4Sb_(11.5)Te_(0.5) nanocomposites to some extent, but it will also degrade the structure of the sample, and cause the decrease of the sample's mechanical prosperities.