Role of Nanostructuring and Microstructuring in Silver Antimony Telluride Compounds for Thermoelectric Applications (original) (raw)
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Silver-Antimony-Telluride: From First-Principles Calculations to Thermoelectric Applications
Thermoelectrics for Power Generation - A Look at Trends in the Technology, 2016
Silver-antimony-telluride (AgSbTe 2) based compounds have emerged as a promising class of materials for thermoelectric (TE) power generation at the mid-temperature range. This Chapter demonstrates utilization of first-principles calculations for predicting TE properties of AgSbTe 2-based compounds and experimental validations. Predictive calculations of the effects of La-doping on vibrational and electronic properties of AgSbTe 2 compounds are performed applying the density functional theory (DFT), and temperature-dependent TE transport coefficients are evaluated applying the Boltzmann transport theory (BTE). Experimentally, model ternary (AgSbTe 2) and quaternary (3 at. % La-AgSbTe 2) compounds were synthesized, for which TE transport coefficients were measured, indicating that thermal conductivity decreases due to La-alloying. The latter also reduces electrical conductivity and increases Seebeck coefficients. All trends correspond with those predicted from first-principles. Thermal stability issues are essential for TE device operation at service conditions, e.g. changes of matrix composition and second-phase precipitation, and are also addressed in this study on both computational and experimental aspects. It is shown that La-alloying affects TE figure-of-merit positively, e.g., improving from 0.35 up to 0.50 at 260 °C. We highlight the universal aspects of this approach that can be applied for other TE compounds. This enables us screening their performance prior to synthesis in laboratory.
Journal of Nanoscience and Nanotechnology, 2017
We report on rapid solidification of an Ag 16 7 Sb 30 0 Te 53 3 compound using planar flow casting to stabilize the-AgSbTe 2 single phase and avoid precipitation of the interconnected Sb 2 Te 3 phase, which leads to deterioration of thermoelectric properties. Rapidly solidified samples are in form of flakes with different thickness (60-400 m). Precipitation of Sb 2 Te 3 phase is fully inhibited in thin flakes (thickness below 100 m), which consist of an homogeneous-AgSbTe 2 matrix, whereas isolated Sb 2 Te 3 precipitates, dispersed throughout the-AgSbTe 2 matrix, were found in thick flakes (thickness above 100 m). The lattice parameter of the-AgSbTe 2 phase progressively increases with the cooling rate, indicating progressive supersaturation of the matrix for high degree of supercooling. Bulk specimens were prepared by hot pressing of the rapidly solidified flakes to evaluate thermoelectric properties. After sintering of the rapidly solidified flakes, the differential scanning calorimetry (DSC) traces indicates partial decomposition of the non equilibrium-AgSbTe 2 into the stable phases. Measurements of the thermoelectric transport properties indicate the positive effects of rapid solidification on thermal conductivity and Seebeck coefficient and its negative effect on electrical conductivity, suggesting an operative way to improve thermoelectric performance.
Phase equilibria of Ag–Sb–Te thermoelectric materials
Acta Materialia, 2011
The ternary Ag-Sb-Te system is important for thermoelectric applications because the AgSbTe 2 ternary compound has a high figureof-merit and because Ag-Sb-Te is a subsystem of the very promising quaternary Pb-Ag-Sb-Te thermoelectric alloys. In this study we prepared equilibrated Ag-Sb-Te ternary alloys at 250 and 400°C. These alloys were metallographically examined, and their microstructures and equilibrium phases were determined. Based on the phase equilibria information available in the literature and the experimental results determined in this study, the isothermal sections of the ternary Ag-Sb-Te system at 250 and 400°C were constructed. The AgSbTe 2 compound is stable at 400°C but not at 250°C. Moreover, high-resolution transmission electronic microscopy images of the ternary AgSbTe 2 compound and its crystal structure were determined. The crystal structure of AgSbTe 2 is rock salt (NaCl type), and its homogeneous compositional regime is determined to be 49.0-53.0 at.% Te and 28.0-30.0 at.% Sb. The solubilities of Ag in the Sb-Te binary compounds, c and d, at 400°C are as high as 8.6 and 5.7 at.%, respectively.
Facile synthesis and thermal analysis of antimony telluride nanostructures
Materials Today: Proceedings, 2018
Fabrication of nano-sized thermoelectric (TE) semiconductors like Antimony chalcogenides and study of their properties is a growing interest among the inorganic thermoelectric (TE) materials, which leads to the increase in the efficiency of energy conversion. The demand for fabricating high performance Thermoelectric (TE) materials in large quantity is very high. A facile synthesis was carried out for nanostructures of Sb 2 Te 3 material trough chemical precipitation and solvo-thermal route. Both these chemical synthesis routes are not complicated and are suitable for expeditious way of synthesizing Nano crystallites, but have their own advantages. The structural and morphological studies of the prepared nanostructure material were carried out by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The thermal studies were carried by Non destructive Thermal Analysis. Measurements of the thermal conductivity of the prepared nanostructured powders indicate that these synthesized Sb2Te3 material can be tuned to enhance the thermoelectric (TE) behavior as they possess considerably low thermal conductivity than that of bulk Sb 2 Te 3 .
Journal of Alloys and Compounds, 2010
Ternary Ag x Sb 2−x Te 3−x thermoelectric materials have been prepared with x value varying from 0.78 to 0.93. By adjusting the Ag 2 Te ratio, double-phased in situ nanocomposites were obtained with the nanostructured Ag 2 Te embedded in the AgSbTe 2 matrix when x > 0.81. The high-resolution transmission electron microscopy observation showed that the Ag 2 Te precipitates were in situ formed as nanodots and nanoscale lamellar structures. Compared with the single-phased samples of x = 0.78 and 0.81, the Seebeck coefficient of the nanocomposite samples exhibited significant improvement over the entire measured temperature range and the electrical conductivity also slightly increased, resulting in the increase of the power factor. At the same time, the thermal conductivity of the nanocomposite samples slightly decreased. The optimization of both the power factor and the thermal conductivity contributed to the notable improvement in figure of merit ZT by a factor of ∼40% at 670 K.
Journal of Alloys and Compounds, 2021
Antimony telluride (Sb 2 Te 3) nanoparticles of different sizes were fabricated by mechanical alloying (MA) of elemental Sb and Te powers for different durations. The powder nanostructures were pelletized, annealed in Ar ambient, and characterized by XRD, FESEM, TEM to study the effect of milling time and thermal treatment on particle size, grain growth, and crystallinity. The annealed and unannealed pelletized nanostructures were analyzed in a PPMS to study the effect of grain growth on their electrical and thermoelectric properties. Room temperature electrical conductivity of the p-type semiconductor nanostructures improved significantly (from~10 3 to~10 5 mho/m) due to thermal annealing and results in the considerable improvement in thermoelectric figure of merit (ZT). Thermal annealing-induced grain growth also transforms the semiconducting nature of the sample to metallic. The reduced thermal conductivity of the nanostructures with reduced grain size improves the ZT. The temperaturedependent Lorenz number (L effective) is used to find the electronic contribution of total thermal conductivity, and it is explained by the non-parabolic Kane model.
Preparation and thermoelectric properties of AgPb m SbTe 2+ m alloys
Journal of Alloys and Compounds, 2009
Hydrothermally synthesized AgPbmSbTe2+m (m=10–18) nanopowders were pressure-less sintered at 450–480°C for 5h in Ar. The samples show large positive Seebeck coefficient but low electrical conductivity and the AgPb18SbTe20 sample shows higher power factors. The hot pressed AgPb10SbTe12 sample was highly densified with grain size down to nanoscale, and the sample has inhomogeneous Seebeck coefficient. Obviously different thermoelectric properties have been
Fabrication of Ag–Sn–Sb–Te based thermoelectric materials by MA-PAS and their properties
Starting from elemental powder mixtures of AgSn 18 SbTe 20 and Sn 50 Te 50 , P-type AgSn 18 SbTe 20 and Sn 50 Te 50 bulk thermoelectric materials were fabricated by a combined process of mechanical alloying (MA) and plasma activated sintering (PAS). It was found that SnTe compound could be easily synthesized after milling only for 1 h. Prolonging the milling time, Ag and Sb atoms diffused into the lattice of the primary SnTe compound gradually and SnTe-based solid solution was formed. The electrical resistivity and Seebeck coefficient of the as-PASed samples were measured from 323 K to 723 K. The maximum power factor of 1.98 × 10 −3 Wm −1 K −2 was obtained at 673 K for AgSn 18 SbTe 20 and it was higher than that of the material with similar composition from previous published literature.