Papers by Keyword: Thermoelectric Material

Abstract: The Mg₂Si compound was synthesized by the solid state reaction method. The powder precursors of Mg and Si were thoroughly mixed in ballmilling for 24 hr in an argon atmosphere. Mixed powder was pressed at 170MPa and sintered at 800 °C for 6 hr in an argon atmosphere. The sinter powder was crushed in mortar for 1 hr. The crystal structure and microstructure were measured and observed by using XRD and SEM. The microstructure and the crystal structure were analyzed. TheMg₂Si shows single phase, cubic structure and particle size about 1-10 mm.

Abstract: The PbTe has been prepared by pressing and annealing method in argon atmosphere. The PbTe sample was obtained single phase and cubic structure. The Seebeck coefficient, the electrical resistivity, thermal conductivity measured by steady state method and evaluated dimensionless figure merit at room temperature. The values of Seebeck coefficient, the electrical resistivity, thermal conductivity and dimensionless figure merit are about -260 µV/K, 3 mΩcm, 0.5 W/m K and ~ 0.35 respectively at 420 K.

Abstract: Crystal structure of Zn_0.96Al_0.02Ga_0.02O was analyzed by X-Ray diffraction (XRD) technique and the microstructure was observed by scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD results showed single phase and hexagonal structure a = b = 3.24982 Å, and c = 5.20661 Å. The SEM and TEM results showed the grain size of material arrangement changed after sintering and TEM diffraction pattern confirmed hexagonal crystal structure of Zn_0.96Al_0.02Ga_0.02O after sintering.

Abstract: Ca₃Co_4xCu_xO₉ (0x1.4) misfit-layered thermoelectric oxides were prepared by traditional solid-state reaction method which cost less, operate easer, may produce Ca₃Co₄O₉ on large scale. XRD study shows that we obtain Ca₃Co₄O₉ major phase in series Ca₃Co_4xCu_xO₉ (0x1.4) samples which were sintered at the highest temperature 880°C for 8h by two steps. Metallographic microscopic analysis indicates that some samples grain size range at 2~4μm which were doped less Cu. Doping Cu in different way experiment suggests that Ca₃Co_4xCu_xO₉ (x=0.4) sample has lower electric resistivity while Ca₃Co₄O₉+5%Cu samples resistivity increases, compared with Ca₃Co₄O₉ (x=0). The article infers that Ca₃Co_4xCu_xO₉ (0x0.4) can decrease the electric resistivity of Ca₃Co₄O₉.

Abstract: The 8.33at% Mn-doped TiFeSb half-heusler thermoelectric materials were studied by first-principles in this paper. The space occupying of Mn atoms in Mn-doped TiFeSb system was studied according to thermodynamic stability, mechanical stability, and density of states at the Fermi level. The results show that Mn atoms would substitute Ti atoms preferentially at 8.33at% doping amount. The electronic and phonon transport properties were calculated in TiFeSb and (Ti_0.75Mn_0.25)FeSb to characterize their electronic and thermal conductivity. The results indicate that Mn-doping can increase the power factor due to improving the electronic conductivity while reducing the lattice thermal conductivity. Therefore, the (Ti_0.75Mn_0.25)FeSb are expected to show better thermoelectric properties than TiFeSb.

Abstract: Various (ZnO)₅In₂O₃ ceramics were fabricated by microwave heating. Density, XRD pattern and microstructure were examined and those of Al-doped (ZnO)₅In₂O₃ were almost the same as Al-free one. Highly textured (ZnO)₅In₂O₃ ceramic was also fabricated by reactive templated grain growth (RTGG) method. The electrical conductivity was not improved by Al-doping; however it was improved slightly by microwave heating compared with conventional heating and especially improved by texturing using RTGG method. On the other hand, the absolute Seebeck coefficient in microwave heating was improved about 25% by Al-doped. Maximum electric power factor of textured specimen fabricated by RTGG method along ab-plane showed 5.76×10^-4 WK^-2m^-1 (at 873K), which was attributed to high electrical conductivity.

Abstract: In the current work p-Pb_0.925Yb_0.075Te:Te and n-Pb_0.925Yb_0.075Se_0.2Te_0.8 powders synthesized by solid-state microwave route were used to fabricating thermally evaporated thin films. The micro-thermoelectric devices were composedof 20-pairs and 10-pairs p-Pb_0.925Yb_0.075Te:Te and n-Pb_0.925Yb_0.075Se_0.2Te_0.8 thin films on glass substrates. Overall size of the thin films thermoelectric generators which consist of 20-pairs and 10-pairs of legs connected by aluminumelectrodes were 23 mm×20 mm and 12 mm×10 mm, respectively. The 20-pairs p–n thermocouples in series device generated output maximum open-circuit voltage of 275.3 mV and a maximum output power up to 54.4 nW at temperature difference ∆T= 162 K, and 109.4 mV and 16.7 nW at ∆T=162 K, for 10-pairs, respectively.

Abstract: Thermoelectric materials are a novel class of materials having unique characteristics. They are Seebeck and Peltier effect materials and are used as thermocouples, for thermoelectric cooling of microelectronic products, as thermoelectric converter for energy conservation etc. Due to their versatility of behaviour, they are now used as construction materials for microelectronic equipment, wireless sensors also. This paper aims at elaborating the development of such materials by compiling the recent and ongoing researches. In this regard, the research developments of some newer materials by other investigators have been presented here. Brief details of the development of thermoelectric generation, thermoelectric cooling, thermoelectric power generator for wearable systems, nano-thermocouple, thermoelectric Peltier microcoolers etc. are presented. In these elaborations, it is shown by the respective investigators that these TE materials can be effectively used in heavily doped semiconductor, thin films, quantum well etc.

Abstract: Significant progress has been made in thermoelectric materials during the last decades and it is found that thermoelectric thin film materials have high thermoelectric conversion efficiency. ZnO based thermoelectric materials, such as ZnO:Al (AZO), are considered as the most promising oxide materials for high-temperature, nontoxic and low-cost thermoelectric application. In this work, the effects of annealing temperature on the thermoelectric properties of AZO thin films prepared by direct current magnetron sputtering were investigated. The results indicate that the Seebeck coefficient of AZO thin films increases and the resistivity decreases as increasing of annealing temperature. Among the prepared AZO films in this work, the maximum absolute value of Seebeck coefficient is 460 μV/K and the minimum resistivity is 3.25×10^-4 Ω·m. The sample annealed at 773 K has a maximum power factor value of 1.46×10^-4 W/mK² at 620 K with a moderate Seebeck coefficient of-355 μV/K and a electrical conductivity of 1.16×10³ S/m.

Abstract: In the present study, the glass microsphere dispersed Bi-Sb thermoelectric materials have been fabricated through mechanical alloying followed by pressureless sintering. The phase composition and the microstructure were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. Electrical conductivity, Seebeck coefficient and thermal conductivity were measured in the temperature range of 77~300 K. The ZT values were calculated according to the measurement results. The results showed that the electrical conductivity, Seebeck coefficient and thermal conductivity decreased by adding glass microsphere into Bi-Sb thermoelectric materials. However, the optimum ZT value of 0.24 was obtained at 260 K, which was increased 10% than that of the Bi-Sb matrix. So it is confirmed that the thermoelectric performance of Bi-Sb-based materials can be improved by adding moderate glass microspheres.