Infrared Absorption of Magnesium Stannide

Lipson, Herbert G.; Kahan, A.

doi:10.1103/physrev.133.a800

Cited by 55 publications

(13 citation statements)

References 15 publications

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“…The conduction band of Mg 2 Si and Mg 2 Sn is composed of a primary minimum at the X point and a secondary minimum lying above it at the same k‐point . In Mg 2 Si, the heavy band (C H ) is above the light one (C L ) with an energy gap of ≈0.4 eV, while for Mg 2 Sn the two bands reverse with a 0.16 eV gap . As shown in Figure b, by increasing the Si/Sn ratio, the energy position of each band varies with composition and converges at Sn content x = 0.65–07 .…”

Section: Strategies For the Optimization Of Individual Te Parametersmentioning

confidence: 93%

Compromise and Synergy in High‐Efficiency Thermoelectric Materials

et al. 2017

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The past two decades have witnessed the rapid growth of thermoelectric (TE) research. Novel concepts and paradigms are described here that have emerged, targeting superior TE materials and higher TE performance. These superior aspects include band convergence, "phonon-glass electron-crystal", multiscale phonon scattering, resonant states, anharmonicity, etc. Based on these concepts, some new TE materials with distinct features have been identified, including solids with high band degeneracy, with cages in which atoms rattle, with nanostructures at various length scales, etc. In addition, the performance of classical materials has been improved remarkably. However, the figure of merit zT of most TE materials is still lower than 2.0, generally around 1.0, due to interrelated TE properties. In order to realize an "overall zT > 2.0," it is imperative that the interrelated properties are decoupled more thoroughly, or new degrees of freedom are added to the overall optimization problem. The electrical and thermal transport must be synergistically optimized. Here, a detailed discussion about the commonly adopted strategies to optimize individual TE properties is presented. Then, four main compromises between the TE properties are elaborated from the point of view of the underlying mechanisms and decoupling strategies. Finally, some representative systems of synergistic optimization are also presented, which can serve as references for other TE materials. In conclusion, some of the newest ideas for the future are discussed.

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Section: Strategies For the Optimization Of Individual Te Parametersmentioning

confidence: 93%

Compromise and Synergy in High‐Efficiency Thermoelectric Materials

et al. 2017

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“…Plots of all2 and all3 vs. hv gave equally good straight lines whose intercepts were about 0.015eV lower than t.hose of [9]. No pressure shift was observed in the pressure range available.…”

Section: Optical Measurementsmentioning

confidence: 75%

“…Better cryst,als are needed to get (BEIBP), from electrical measurements on Mg,Si and Mg,Ge. Higher pressures are needed for getting (BEIBP), for Mg,Sn from optical data, but the ambiguity in the fits of the absorption edge, leading not only to two possible values for E , but to two values of (BEIBP), [9], may preclude a unique determination of (BE/BP), from optical data. The electrical measurements on Mg,Sn clearly give (dEIBP), > 0.…”

Section: Discussionmentioning

confidence: 99%

Pressure Coefficient of the Band Gap in Mg₂Si, Mg₂Ge, and Mg₂Sn

Stella

Hopkins

Lynch

1967

Physica Status Solidi (b)

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The pressure derivative of the band gap, (aE/aP)T, has been determined to be + 3 x x evbar-l forMg,Sn by measurements of the pressure derivative of the electrical conductivity. Similar measurements on Mg,Si and Mg,Ge were inconclusive, but estimates of this parameter were made from the shift of the optical obsorption edge with pressure.(aE/aP), = (0 0.5) x evbar-l for both compounds. The similarity of the coefficients for Mg,Si and Mg,Ge suggests that the symmetries of the band edges of both compounds are similar, while either the conduction band edge, the valence band edge, or both edges in Mg,Sn may have a different symmetry.Le coefficient de pression de la bande interdite (aE/aP),, determink d'aprhs des mesures du coefficient de pression de la conductivite Blectrique, a la valeur +3 x evbar-l pour le Mg,Sn. Des mesures semblables dans Mg,Si et Mg,Ge n'ont pas BtB concluantes, mais & partir du glissement du seuil d'absorption optique avec la pression, on estime que le m6me parametre a la valeur (aE/aP)T = (0 & 0.5) x €0-6 evbar-l pour les deux composks. Le fait que Mg,Si e t Mg,Ge ont des coefficients voisins sugghre que les bandes ont des extrema de m h e symktrie dans les deux composks, tandis que les e x t r h a de la bande de conduction ou de la bande de valence, ou encore des deux bandes, peuvent avoir des symktries diffkrentes dans Mg,Sn., ) Present address:

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“…S5, ESI †), which may be related to the electronic transition 25 between multiple conduction bands. 45,46 Furthermore, from our new viewpoint suggested by Eq. (10), the widening band gap contributes to the enhancement in the new material parameter B* and hence increase of maximum ZT with respect to doping concentration and temperature.…”

Section: Decreased Bipolar Thermal Conductivity Due To Increased E Gmentioning

confidence: 99%

New insight into the material parameter B to understand the enhanced thermoelectric performance of Mg₂Sn_1−x−yGe_xSb_y

Liu

Zhou

et al. 2016

Energy Environ. Sci.

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Historically, material parameter B incorporating weighted mobility and lattice thermal conductivity has guided the exploration of novel thermoelectric materials. However, the conventional definition of B neglects the bipolar effect which can dramatically change the thermoelectric energy conversion efficiency at high temperatures. In this paper, a generalized material parameter B * is derived, which connects weighted mobility, lattice thermal conductivity, and band gap. Broader ContextThermoelectric conversion involves the transport of electrons and phonons. It has been very challenging to synergistically tune the macro thermoelectric transport parameters: electrical conductivity, thermal conductivity, and Seebeck coefficient as these properties are coupled 20 to each other. Recently, we have achieved a significant enhancement in the thermoelectric performance of Mg 2 Sn by partially substituting Sn with Ge and doping Sb. The new material Mg 2 Sn 0.728 Ge 0.25 Sb 0.022 has a high average ZT (0.9) and power factor (52 μW cm −1 K −2 ) in the temperature range of 25-450 °C, with favourably high efficiency and large output power density. The ZT improvement is understood through a generalized material parameter B * , which connects weighted mobility, lattice thermal conductivity, and band gap. A higher B * is desired for higher ZT. The new parameter will help guide the optimizations of known materials by synergistically tailoring 25 these fundamental parameters to enhance their thermoelectric performance, and the search of new materials by using it as new scale.

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Infrared Absorption of Magnesium Stannide

Cited by 55 publications

References 15 publications

Compromise and Synergy in High‐Efficiency Thermoelectric Materials

Compromise and Synergy in High‐Efficiency Thermoelectric Materials

Pressure Coefficient of the Band Gap in Mg₂Si, Mg₂Ge, and Mg₂Sn

New insight into the material parameter B to understand the enhanced thermoelectric performance of Mg₂Sn_1−x−yGe_xSb_y

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Infrared Absorption of Magnesium Stannide

Cited by 55 publications

References 15 publications

Compromise and Synergy in High‐Efficiency Thermoelectric Materials

Compromise and Synergy in High‐Efficiency Thermoelectric Materials

Pressure Coefficient of the Band Gap in Mg2Si, Mg2Ge, and Mg2Sn

New insight into the material parameter B to understand the enhanced thermoelectric performance of Mg2Sn1−x−yGexSby

Contact Info

Product

Resources

About

Pressure Coefficient of the Band Gap in Mg₂Si, Mg₂Ge, and Mg₂Sn

New insight into the material parameter B to understand the enhanced thermoelectric performance of Mg₂Sn_1−x−yGe_xSb_y