Article

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

Intermetallics (Impact Factor: 1.86). 01/2010; 18(1):193-198. DOI: 10.1016/j.intermet.2009.07.011

ABSTRACT High density polycrystalline CaCd2Sb2 and EuCd2Sb2 intermetallics are synthesized by Spark Plasma Sintering and their thermoelectric properties are investigated. X-ray diffraction measurements reveal both materials have a structure in R3¯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 CaCd2Sb2 is 0.04 at 600K and that of EuCd2Sb2 is 0.60 at 617K. Theoretical calculations show that CaCd2Sb2 is a degenerate semiconductor with a band gap of 0.63eV, while EuCd2Sb2 is metallic with DOS of 13.02electrons/eV. For deeper understanding of the better thermoelectric properties of EuCd2Sb2, its low temperature magnetic, transport and heat capacity properties are investigated. Its Nèel temperature is 7.22K, convinced by heat capacity anomaly at 7.13K. Hall effect convinced that it is a p-type conductive material. It has high Hall coefficient, high carrier concentration and high carrier mobility of +1.426cm3/C, 4.38×1018/cm3 and 182.40cm2/Vs, respectively. They are all in the magnitude of good thermoelectric materials. The Eu 4f level around Fermi energy and antiferromagnetic order may count for the better thermoelectric properties of EuCd2Sb2 than that of CaCd2Sb2.

1 Bookmark
 · 
69 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Compact polycrystalline samples of SrZn2Sb2 [space group P[`3] m1 P\overline{3} m1 , a=4.503(1)Å, c=7.721(1)Å] were prepared by spark plasma sintering. Thermoelectric performance, Hall effect, and magnetic properties were investigated in the temperature range from 2K to 650K. The thermoelectric figure of merit ZT was found to increase with temperature up to ZT=0.15 at 650K. At this temperature the material showed a high Seebeck coefficient of +230μVK−1, low thermal conductivity of 1.3Wm−1K−1, but rather low electrical conductivity of 54Scm−1, together with a complex temperature behavior. SrZn2Sb2 is a diamagnetic p-type conductor with a carrier concentration of 5×1018 cm−3 at 300K. The electronic structure was calculated within the density-functional theory (DFT), revealing a low density of states (DOS) of 0.43stateseV−1cell−1 at the Fermi level. KeywordsSrZn2Sb2 -Thermoelectric performance-Hall effect-magnetic properties
    Journal of Electronic Materials 39(9):1772-1776. · 1.64 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The thermoelectric performance of EuZn(2)Sb(2) and EuCd(2)Sb(2) was optimized by mixed occupation of the transition metal position. Samples in the solid solution Eu(Zn(1-x)Cd(x))(2)Sb(2) with the CaAl(2)Si(2)-type crystal structure (space group Pm1) were prepared from the elements for compositions with x = 0, 0.1, 0.3, 0.5 and 1. The thermoelectric properties were investigated after densification of the products by spark plasma sintering (SPS). The samples show low electrical resistivity, high thermopower and a low lattice thermoconductivity. The highest ZT value of 1.06 at 650 K is obtained for x = 0.1.
    Dalton Transactions 01/2010; 39(4):1101-4. · 3.81 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Zn doped BaMn2Sb2 single crystals were synthesized by a Sn-flux method using nominal compositions of BaMn2−xZnxSb2 (x = 0.0, 0.3, 0.5, 0.7, and 1.0). The products were characterized by powder X-ray diffraction and scanning electron microscopy equipped with electron energy dispersive spectroscopy, respectively. A pure phase of BaMn2Sb2 for x = 0, a mixture of Zn doped BaMn2Sb2 and Sn for x = 0.3–0.7, and a mixture of Zn doped BaMn2Sb2, Sn and ZnSb for x = 1 were obtained. The electrical conductivity and Seebeck coefficient of the crystals from room temperature to 773 K were measured. The electrical conductivity of all the crystals increased with increasing temperature, while the Seebeck coefficient decreased with increasing temperature and approached negative values at high temperatures. The Zn doped BaMn2Sb2 crystals showed significantly higher Seebeck coefficient at low temperatures (T < 550 K) and lower electrical conductivity at higher temperatures (T > 550 K) than the BaMn2Sb2 single crystal.
    Journal of Materials Science Materials in Electronics 23(12). · 1.49 Impact Factor