Synthesis and properties of CaCd 2Sb 2 and EuCd 2Sb 2

Abstract

High density polycrystalline CaCd 2Sb 2 and EuCd 2Sb 2 intermetallics are synthesized by Spark Plasma Sintering and their thermoelectric properties are investigated. X-ray diffraction measurements reveal both materials have a structure in R 3 ¯ m space group, containing a small amount of CdSb as a second phase. Thermoelectric measurements indicate both are p-type conductive materials. The figure of merit value of CaCd 2Sb 2 is 0.04 at 600 K and that of EuCd 2Sb 2 is 0.60 at 617 K. Theoretical calculations show that CaCd 2Sb 2 is a degenerate semiconductor with a band gap of 0.63 eV, while EuCd 2Sb 2 is metallic with DOS of 13.02 electrons/eV. For deeper understanding of the better thermoelectric properties of EuCd 2Sb 2, its low temperature magnetic, transport and heat capacity properties are investigated. Its Nèel temperature is 7.22 K, convinced by heat capacity anomaly at 7.13 K. Hall effect convinced that it is a p-type conductive material. It has high Hall coefficient, high carrier concentration and high carrier mobility of +1.426 cm 3/C, 4.38 × 10 18/cm 3 and 182.40 cm 2/Vs, respectively. They are all in the magnitude of good thermoelectric materials. The Eu 4 f level around Fermi energy and antiferromagnetic order may count for the better thermoelectric properties of EuCd 2Sb 2 than that of CaCd 2Sb 2.