Structure and thermoelectric properties of higher manganese silicides synthesized by pack cementation (original) (raw)
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Thermoelectric performance of higher manganese silicide nanocomposites
Journal of Alloys and Compounds, 2015
Thermoelectric is a promising technology that can convert temperature differences to electricity (or vice versa). However, their relatively low efficiencies limit their applications to thermoelectric power generation systems. Therefore, low cost and high performance are important prerequisites for the application of thermoelectric materials to automotive thermoelectric generators. Silicide-based thermoelectric materials are good candidates for such applications. Recently, the thermoelectric performances of silicide-based thermoelectric materials have been significantly improved. However, increasing the thermoelectric performance of the materials while ensuring mechanical reliability remains a challenge. This review summarizes the preparation and design guidelines for silicide-based thermoelectric nanocomposites, as well as our recent progress in the development of nanocomposites with high thermoelectric performances or high mechanical reliabilities.
Journal of Alloys and Compounds, 2019
Effects of Re substitution for Mn on the microstructure-property relationships in Mn 30.4 Re 6.0 Si 63.6 thermoelectric material have been investigated in comparison with those in Mn 36.4 Si 63.6. The rapid quenching using the meld spinning leads to relatively uniform distribution of Re. After sintering, the Nowotny chimney ladder phases known as the higher manganese silicide (HMS) are stabilized in both the Re-free and Re-substituted HMSs, and the chemical formulae become Mn 15 Si 26 and Mn 19 Si 33 , respectively. The Re atoms are successfully substituted for Mn in the (Mn,Re) 19 Si 33 HMS. The number density of the sublattice dislocation in the Re-substituted HMS is 1.6 times higher than that in the Re-free HMS, that causes a decrease in lattice thermal conductivity. Due to the impurity effect of the Re substitution, the electrical conductivity is supposed to be enhanced, resulting in the highest dimensionless figure of merit (ZT) among the investigated HMSs.
Journal of Nanoscience and Nanotechnology, 2017
Higher manganese silicides (HMS), represented by MnSi x x = 1.71-1.75), are promising p-type candidates for thermoelectric (TE) energy harvesting systems at intermediate temperature range. The materials are very attractive as they may replace lead based compounds due to their nontoxicity, low cost of starting materials, and high thermal and chemical stability. Dense pellets were obtained through fast reactive sintering by spark plasma sintering (SPS). The addition-or nanoinclusion, of Al and Mg permitted the figure of merit enhancement of the material obtained with this technique, reaching the highest value of 0.40 at 600 C. Morphology, composition and crystal structure of the samples were characterized by electron microscopies, energy dispersive X-ray spectroscopy, and X-ray diffraction analyses, respectively.
Thermoelectric Properties of Higher Manganese Silicide Consolidated by Flash-Sintering Technique
Social Science Research Network, 2022
Higher manganese silicide (HMS) MnSi γ films with varying γ (1.65 ≤ γ ≤ 3.23) were deposited on oxidized Si wafers at 703K by radio frequency (RF) magnetron co-sputtering of Mn and Si targets. As-deposited films were annealed at 1273K for 3min using a lamp annealing system, and the thermoelectric (TE) properties were measured in the temperature range from room temperature to 1073K. All the MnSi γ films were p-type below about 550K, but the polarity converted to n-type at higher temperatures. Moreover, the power factor (PF) of the polarity-inverted films was exceptionally high, reaching the maximum value of 12.3 mW/K 2 m in the annealed MnSi 2.04 film. In case of the as-deposited films, the PF in the p-type regime (PF p) grew larger as the Si/Mn molar ratio γ approached the stoichiometric value of 1.73, while the PF n became vanishingly small. In contrast, the PF n of the annealed films remained very high even in the Mn-rich film (γ < 1.73), such that 9.6 mW/K 2 m was obtained from the MnSi 1.65 film. Hall measurement at elevated temperatures (≤ 773K) showed that electron mobility was greatly increased after the annealing, which has produced unusually high PF n. The HMS phase was composed of Mn 4 Si 7 and Mn 11 Si 19 , but regions of unidentified phase were also confirmed by transmission Kikuchi diffraction (TKD) analysis, the proportion of which was larger in the Si-rich films. The modification of the band structure induced by defects and structural disorder of the Mn and/or Si sublattice are supposed to be the origin of this novel phenomenon.
Journal of Materials Science
In this paper, the crystal structure, microstructure, thermoelectric properties and figure of merit (zT) of highly pure higher manganese silicide (HMS) alloys are reported and discussed without the bias generally introduced by impurities in published results. The alloys were produced by both solid-state reaction diffusion assisted by spark plasma sintering and conventional arc melting in order to evaluate the effect of the process on the microstructure and on the resulting properties of HMS. The effect of Ge addition is also explored. Properties diagram for thermoelectric materials is displayed to assess the performance of undoped and Ge-doped HMS alloys in comparison with the state of the art. Electrical conductivity and zT at 500°C of the HMS alloys studied here exceed published properties achieved with similar alloys, providing new process options for reliable, affordable and efficient thermoelectric applications.
Journal of Alloys and Compounds, 2022
Higher manganese silicide (HMS) MnSi γ films with varying γ (1.65 ≤ γ ≤ 3.23) were deposited on oxidized Si wafers at 703K by radio frequency (RF) magnetron co-sputtering of Mn and Si targets. As-deposited films were annealed at 1273K for 3min using a lamp annealing system, and the thermoelectric (TE) properties were measured in the temperature range from room temperature to 1073K. All the MnSi γ films were p-type below about 550K, but the polarity converted to n-type at higher temperatures. Moreover, the power factor (PF) of the polarity-inverted films was exceptionally high, reaching the maximum value of 12.3 mW/K 2 m in the annealed MnSi 2.04 film. In case of the as-deposited films, the PF in the p-type regime (PF p) grew larger as the Si/Mn molar ratio γ approached the stoichiometric value of 1.73, while the PF n became vanishingly small. In contrast, the PF n of the annealed films remained very high even in the Mn-rich film (γ < 1.73), such that 9.6 mW/K 2 m was obtained from the MnSi 1.65 film. Hall measurement at elevated temperatures (≤ 773K) showed that electron mobility was greatly increased after the annealing, which has produced unusually high PF n. The HMS phase was composed of Mn 4 Si 7 and Mn 11 Si 19 , but regions of unidentified phase were also confirmed by transmission Kikuchi diffraction (TKD) analysis, the proportion of which was larger in the Si-rich films. The modification of the band structure induced by defects and structural disorder of the Mn and/or Si sublattice are supposed to be the origin of this novel phenomenon.
Enhanced Thermoelectric Properties of W- and Fe-Substituted MnSi γ
Journal of Electronic Materials, 2016
We have investigated the effect of heavy-element (W) substitution on the thermoelectric properties of higher manganese silicide (HMS). Samples were prepared by arc melting followed by liquid quenching, where the latter assisted in achieving higher solubility for tungsten. We observed that Mn 34.6 W 1.8 Si 63.6 was a p-type material, whereas simultaneous substitution of 12 at.% Fe made the higher manganese silicide an n-type material. The optimal carrier concentration was obtained by simultaneous substitution of Fe and W for Mn atoms. Although the samples were metastable, we successfully obtained bulk samples by a low-temperature (970 K), high-pressure (>100 MPa), long-duration sintering process. The lattice thermal conductivity was effectively reduced by W substitution, and the ZT value was improved to above 0.5 for both n-and p-type samples.
Thermoelectric properties of higher manganese silicide films with addition of chromium
2007
Polycrystalline higher manganese silicide (MnSi 1.73) films with addition of chromium were prepared on thermally oxidized silicon substrates by magnetron sputtering. A cap layer of chromium disilicide was used as the doping source. Both the Seebeck coefficient and the resistivity were strongly dependent on the amount of chromium added to the film. When the thickness ratio of chromium disilicide to manganese silicide increased from 2.4% to 9.8%, the Seebeck coefficient at room temperature decreased from 121 to 100 µV/K. However, the temperature at which the maximum value of the Seebeck coefficient occurred increased from 343 to 633 K. When the thickness ratio was about 2.4%, the resistivity increased to 33 × 10 −3 Ω cm. Otherwise, the resistivity decreased from 13 × 10 −3 to 5.2 × 10 −3 Ω cm by increasing the thickness ratio. As a result, the thermoelectric power factor increased greatly at high temperatures. Several activation energies (0.021-0.383 eV) were observed from the curves of the logarithm of resistivity versus reciprocal temperature.
A review on Silicide based materials for thermoelectric applications
Thermoelectric materials are considered prime in converting energy, thanks to its nature to translate heat into electricity openly. Low efficiency and the intricacy in fabrication restrict their applications commercially. Moreover, there are certain thermoelectric materials such as alloys of telluride owing to their toxicity present peril to the environment. There is scarcity in present examination to get an ecological gracious thermoelectric material which is available in abundance to be utilized in large volumes owing to the low efficiency. The paper presents a review of such thermoelectric material which is ecological gracious. In the beginning, a number of techniques employed in advancing the figure of merit (ZT) is offered, then an indepth review of several thermoelectric materials which are siliconbased is showed. N-type doping of Mg2Si0.75Sn0.25 among aluminum along with lead at operational temperature of 850 K scaled up the value of ZT by a factor of 2. Considerable addition in carrier concentration resulted in the attainment of figure of merit with peak value of 1.4. Techniques such as nanostructuring and doping have boosted silicides such as HMS to show a remarkable achievement in the attainment of dimensionless figure of merit. Iron disilicide (FeSi2), Chromium silicide (CrSi2) and Cobalt Silicide (CoSi) have shown their worth to be employed as thermoelectric materials in industries in near future. It is also recommended to analyze supplementary types of metal oxides and organic materials which exhibit thermoelectric traits. I.