Search

Abstract: In the present study, p-type (Bi,Sb)2Te3 thermoelectric materials have been fabricated through the spark plasma sintering (SPS) method by using powders with various particle sizes. Electrical conductivity (σ), Seebeck coefficient (α), and thermal conductivity (κ) were evaluated in the temperature range of 300–500K. The effect of annealing of the sintered samples on thermoelectric properties was also investigated. The maximum figure of merit ZT (ZT = α2σT/κ) of the sintered samples in the direction perpendicular to the pressing direction (with c-axis preferred orientation) was 1.15 at about 350K, corresponding to be about 115% of that of the zone-melted ingot with the same composition in the same crystallographic orientation; while the bending strength was highly improved from about 10 to 80MPa. [Copyright &y& Elsevier]

Ca3-xDyxCo4O9+δ (x=0, 0.15, 0.3 and 0.45) polycrystalline samples have been prepared using a sol–gel process followed by SPS sintering. Their thermoelectric properties have been carefully studied from room temperature to 1000 K. The substitution of Dy for Ca results in increasing of both thermopower and electrical resistivity, which could be attributed to the decreasing of carrier concentrations. The Dy substituted samples (x=0, 0.3) have lower thermal conductivity than Ca3Co4O9+δ due to their lower electronic and lattice thermal conductivities. The dimensionless figure of merit ZT reaches 0.27 at 1000 K for the sample of Ca2.7Dy0.3Co4O9+δ. [Copyright &y& Elsevier]

Abstract: Polycrystalline (Fe1−x Co x )2VAl (0≤ x ≤0.5) alloys were synthesized through a combined process of arc-melting, annealing and sintering. Thermoelectric properties were investigated from 300 to 850K. Stoichiometric Fe2VAl exhibited p-type conduction, however, it shifted to n-type with slight Co substitution for Fe site. After Co substitution, the electrical conductivity and absolute value of Seebeck coefficient at room temperature increased from 1.2×105 to 5×105 Sm−1 and 30 to 112μV/K, respectively. Meanwhile, the lattice thermal conductivity dropped from 23 to 6W/mK because of the introduction of extra phonon scattering due to alloying effect. The highest dimensionless figure of merit ZT value for (Fe0.7Co0.3)2VAl is 0.09 at 650K. [Copyright &y& Elsevier]

Abstract: TiCoSb-based half-Heusler compounds were prepared by solid-state reaction and their thermoelectric properties were studied. The un-doped TiCoSb compound shows n-type conduction and demonstrates high Seebeck coefficient at high temperatures. The partial substitution of Co by Ni caused great increase in electron concentration and electrical conductivity, while the Seebeck coefficient and the thermal conductivity showed little change when Ni content (x) is below 5%. A maximum power factor of 16μW/K2 cm and a maximum dimensionless figure of merit (ZT) of 0.27 have been obtained for the composition of TiCo0.95Ni0.05Sb at 900K. [Copyright &y& Elsevier]

The interfacial stability of thermoelectric (TE) joints is among the key issues determining the durability of thermoelectric generators (TEGs) in practical operation. For skutterudite (SKD) based TEGs, the inter-diffusion between the metal electrode and the SKD material at high temperature plays a vital role on the interfacial stability of the joints. In this work, we report the evolution of the interfacial microstructure and the interfacial contact resistivity for a series of p-type SKD TE joints (Ti/Ce y Fe x Co 4 -x Sb 12 , x = 1.5–4, y = 0.35–1) at high temperature. The growth of the intermetallic compound (IMC) layers at the interface of all the joints was found to be controlled by the diffusion process. In contrast to the binary Ti/CoSb 3 joints, the growth of the interfacial IMC layers in the p-type Ti/Ce y Fe x Co 4 -x Sb 12 joints was considerably depressed. Moreover, no brittle TiCoSb phase was formed at the interface of the p-type joints, which resulted in good stability of the interfacial contact resistivity at high temperature. Related mechanisms were discussed. [ABSTRACT FROM AUTHOR]

Abstract: Ba8Ga16Ge30 clathrate crystals were grown by Czochralski method. The influence of growth condition on the composition and thermoelectric property of the obtained crystals was investigated. The lower pulling rate and higher pressure resulted in a larger Ga/Ge ratio in the grown crystals, and the elemental composition was homogeneous. The sample with a higher Ga/Ge ratio showed the larger electrical conductivity than the sample with a lower Ga/Ge ratio, but the Seebeck coefficient was not sensitive to the Ga/Ge ratio, which led to a larger power factor. The higher Ga/Ge ratio also resulted in a lower lattice thermal conductivity and as a result led to a higher ZT value, which was measured to be 0.93 at 850K and could reach 1.3 as extrapolated to 1000K. [Copyright &y& Elsevier]

Abstract: Ge-doped TiCoSb-based half-Heusler compounds, TiCoGe x Sb1−x (x =0–0.2), were prepared by arc melting and spark plasma sintering (SPS). The electrical conductivity, Seebeck coefficient and thermal conductivity were measured from room temperature to 850K. The Seebeck coefficient changed from negative to positive by Ge doping, and the electrical conductivity increased with increasing Ge content. The lattice thermal conductivity for TiCoGe x Sb1−x is considerably reduced, because the point defects induced by Ge substitution for Sb intensively scatter the thermal phonons. The mass fluctuation part Γ mass and strain field fluctuation part Γ stra were estimated, and it was found that the reduction of lattice thermal conductivity is mainly attributed to the strain field fluctuation. Ge doping improved the thermoelectric figure of merit ZT of TiCoSb and the maximum ZT value of 0.16 was obtained for TiCoGe0.15Sb0.85 sample at 850K. [Copyright &y& Elsevier]

Abstract: Sr0.29CoO2 crystals have been successfully prepared by a low temperature ion exchange from layered Na x CoO2, and it is isomorphic to its precursor Na x CoO2 with a layered triangular structure. The thermoelectric properties of Sr0.29CoO2 crystal were measured in the temperature of 2.5–773K. A transition has been exhibited in the resistivity, Seebeck coefficient and carrier concentration at approximately 75K. The resistivity, Seebeck coefficient and power factor increase with increasing temperature, and reach the values of 2.78mΩcm, 171μV/K and 7.1×10−4 Wm−1 K−2 at 773K, respectively. [Copyright &y& Elsevier]