The thermoelectric materials of CoSb 3-based Skutterudite compounds were prepared by spark plasma sintering. The micrographic images, the elemental compositions and the crystalline structures of the samples were characterized by scanning electronic microscopy, energy spectrum analysis and X-ray diffraction respectively. The molar heat capacities of CoSb 3, (Co 0.95Ni 0.05)Sb 3 and Er 0.1CoSb 3 were measured by modulated differential scanning calorimetry from 190 to 600 K. The results show that both the transition element Ni and the rare-earth element Er can decrease considerably the molar heat capacities of CoSb 3-based compounds.