Effect of Magnesium Content and Processing Conditions 	on Phase Formation and Stability in Mg2+δSi0.3Sn0.7

Goyal, Gagan K.; Dasgupta, Titas

doi:10.1007/s11664-017-6012-9

Cited by 7 publications

(5 citation statements)

References 21 publications

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“…Details on homogenization of, e.g., for a Mg 2 Si 0.5 Sn 0.5 matrix and investigation of its microstructure by scanning electron microscope (SEM) can be found in our previous work [21a,22]. Furthermore, Sn‐rich samples were less stable against Mg loss at high temperatures than Si‐rich samples . Therefore, to avoid Mg loss and formation of elemental impurities as well as to tune the microstructure, the sintering temperatures and durations were optimized for different compositions, from 600 °C for x = 1 (Mg 2 Sn) to 800 °C for x = 0 (Mg 2 Si).…”

Section: Methodsmentioning

confidence: 99%

Raman Spectroscopic Study of the Optical Phonons of Mg₂Si_1−xSn_x Solid Solutions

Yasseri

Schüpfer

Chen

et al. 2020

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Mg2Si1−xSnx solid solutions are prepared in the composition range from x = 0 to 1 by mechanical alloying using high‐energy ball milling followed by direct‐current sintering at 600–800 °C. X‐ray diffraction analysis confirms that the samples obtained are uniform solid solutions. Raman spectroscopy shows two first‐order phonon Raman bands and a distribution of Raman signals due to second‐order phonon Raman scattering. The first‐order Raman bands are assigned to the nondegenerate Raman‐forbidden F1u (LO) mode and the triply degenerate Raman‐allowed F2g mode. Both modes exhibit a linear shift of the phonon frequency with a composition showing a clear one‐mode behavior for this solid solution. The findings are discussed in the context of existing theories for the occurrence of the one‐mode or two‐mode behavior of phonons in solid solutions.

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Section: Methodsmentioning

confidence: 99%

Raman Spectroscopic Study of the Optical Phonons of Mg₂Si_1−xSn_x Solid Solutions

Yasseri

Schüpfer

Chen

et al. 2020

Physica Rapid Research Ltrs

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“…It is to be noted that the interface layer was originally a homogeneous mixture of n-doped Mg 2 Si 0.3 Sn 0.7 and Ni. The possible origin of this segregation might lie in the degradation of Mg 2 Si x Sn 1– x based solid solutions at high temperatures, − which results in the formation of the Mg 2 Sn rich phase and elemental Sn along with the Mg 2 Si rich phase . Both Mg 2 Sn eutectic compositions and elemental Sn are molten at the compaction temperature (650 °C) and hence have a tendency to ooze out of the graphite die , due to the uniaxial pressure applied during sintering.…”

Section: Resultsmentioning

confidence: 99%

“…The excess Mg taken during the synthesis of the n- and p-legs was 10 and 2 at %, respectively. With lower compensatory Mg available, the p-leg material is expected to be more prone to degradation. , Hence, the formation of low melting Sn-rich phases and their subsequent segregation and loss from the crucible will be higher compared to the n-leg material. This results in a lower Sn content and lesser thickness of the interface layer, both of which are observed on comparing the p- and n-leg materials.…”

Section: Resultsmentioning

confidence: 99%

“…The possible origin of this segregation might lie in the degradation of Mg 2 Si x Sn 1−x based solid solutions at high temperatures, 38−40 which results in the formation of the Mg 2 Sn rich phase and elemental Sn along with the Mg 2 Si rich phase. 39 Both Mg 2 Sn eutectic compositions 41 and elemental Sn are molten at the compaction temperature (650 °C) and hence have a tendency to ooze out of the graphite die 31,33 due to the uniaxial pressure applied during sintering. This results in the segregation of Si and Sn within the interface layer, with the outer layer richer in molten Sn.…”

Section: Resultsmentioning

confidence: 99%

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Generic Approach for Contacting Thermoelectric Solid Solutions: Case Study in n- and p-Type Mg₂Si_0.3Sn_0.7

Goyal

Dasgupta

2021

ACS Appl. Mater. Interfaces

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Metallization (known as contacting) of thermoelectric (TE) legs is vital to the long-term performance of a TE device. It is often observed that the compositional changes in a TE solid solution may render a given contact material unsuitable due to a mismatch in the thermal expansion coefficient values. Finding suitable contact materials for TE solid solutions (which often are the best TE materials) remains a challenge. In this work, we propose a multilayer single-step approach in which the same combination of contact materials can be used for a wide compositional range in a solid solution. The outer layer is a metal foil, which helps in creating an Ohmic contact with the interconnects. The intermediate layer is a mixture of the TE material and a metal powder, which results in the formation of the diffusion barrier. The innermost layer is the TE material, which is the active component of the device. The strategy was applied on n- and p-doped Mg2Si0.3Sn0.7 with elemental Cu and Ni providing the desired interface functionalities. Single-step compaction was carried out using the monoblock sintering technique. Microscopic investigation reveals the formation of a well-bonded crack-free interface. Various intermetallic phases were identified at the interface, and the formation of the MgNi2Sn phase was found to be critical to prevent any interdiffusion of elements. Electrical contact resistance (r c) measurements were conducted, and low values of 3 and 19 μΩ cm2 were measured in n- and p-type legs, respectively. The contacted TE legs were further annealed at 400 °C for 7 days to check their stability. Microstructural and electrical resistance measurements reveal minimal changes in the interface layer and r c values, indicating the workability of the multilayer technique.

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“…It is commonly reported in the literature that the Mg2(Si,Sn) material system suffers from Mg loss above 500 °C [32][33][34]. It is often reported in the literature that the phase separation in the miscibility gap is followed by the formation of elemental Si, elemental Sn or an Sn-Mg melt due to Mg loss from Mg2(Si,Sn) [10,32,34,35].…”

Section: -Introductionmentioning

confidence: 99%

Influence of Mg loss on the phase stability in Mg2X (X = Si, Sn) and its correlation with coherency strain

et al. 2021

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Effect of Magnesium Content and Processing Conditions on Phase Formation and Stability in Mg2+δSi0.3Sn0.7

Cited by 7 publications

References 21 publications

Raman Spectroscopic Study of the Optical Phonons of Mg₂Si_1−xSn_x Solid Solutions

Raman Spectroscopic Study of the Optical Phonons of Mg₂Si_1−xSn_x Solid Solutions

Generic Approach for Contacting Thermoelectric Solid Solutions: Case Study in n- and p-Type Mg₂Si_0.3Sn_0.7

Influence of Mg loss on the phase stability in Mg2X (X = Si, Sn) and its correlation with coherency strain

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Effect of Magnesium Content and Processing Conditions on Phase Formation and Stability in Mg2+δSi0.3Sn0.7

Cited by 7 publications

References 21 publications

Raman Spectroscopic Study of the Optical Phonons of Mg2Si1−xSnx Solid Solutions

Raman Spectroscopic Study of the Optical Phonons of Mg2Si1−xSnx Solid Solutions

Generic Approach for Contacting Thermoelectric Solid Solutions: Case Study in n- and p-Type Mg2Si0.3Sn0.7

Influence of Mg loss on the phase stability in Mg2X (X = Si, Sn) and its correlation with coherency strain

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Raman Spectroscopic Study of the Optical Phonons of Mg₂Si_1−xSn_x Solid Solutions

Raman Spectroscopic Study of the Optical Phonons of Mg₂Si_1−xSn_x Solid Solutions

Generic Approach for Contacting Thermoelectric Solid Solutions: Case Study in n- and p-Type Mg₂Si_0.3Sn_0.7