Eu5Sn2As6is a Zintl phase crystalizing in the orthorhombic space group
The impact of site selectivity and disorder on the thermoelectric properties of Yb 21 Mn 4 Sb 18 solid solutions: Yb 21 Mn 4−x Cd x Sb 18 and Yb 21−y Ca y Mn 4 Sb 18
Thermoelectric materials can convert heat into electricity. They are used to generate electricity when other power sources are not available or to increase energy efficiency by recycling waste heat. The Yb 21 Mn 4 Sb 18 phase was previously shown to have good thermoelectric performance due to its large Seebeck coefficient (∼290 μV K −1 ) and low thermal conductivity (0.4 W m −1 K −1 ). These characteristics stem respectively from the unique [Mn 4 Sb 10 ] 22− subunit and the large unit cell/site disorder inherent in this phase. The solid solutions, Yb 21 Mn 4− x Cd x Sb 18 ( x = 0, 0.5, 1.0, 1.5) and Yb 21− y Ca y Mn 4 Sb 18 ( y = 3, 6, 9, 10.5) have been prepared, their structures characterized and thermoelectric properties from room temperature to 800 K measured. A detailed look into the structural disorder for the Cd and Ca solid solutions was performed using synchrotron powder X-ray diffraction and pair distribution function methods and shows that these are highly disordered structures. The substitution of Cd gives rise to more metallic behavior whereas Ca substitution results in high resistivity. As both Cd and Ca are isoelectronic substitutions, the changes in properties are attributed to changes in the electronic structure. Both solid solutions show that the thermal conductivities remain extremely low (∼0.4 W m −1 K −1 ) and that the Seebeck coefficients remain high (>200 μV K −1 ). The temperature dependence of the carrier mobility with increased Ca substitution, changing from approximately T −1 to T −0.5 , suggests that another scattering mechanism is being introduced. As the bonding changes from polar covalent with Yb to ionic for Ca, polar optical phonon scattering becomes the dominant mechanism. Experimental studies of the Cd solid solutions result in a max zT of ∼1 at 800 K and, more importantly for application purposes, a ZT avg ∼ 0.6 from 300 K to 800 K.
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- Award ID(s):
- 2001156
- NSF-PAR ID:
- 10324460
- Date Published:
- Journal Name:
- Materials Advances
- Volume:
- 2
- Issue:
- 17
- ISSN:
- 2633-5409
- Page Range / eLocation ID:
- 5764 to 5776
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Pbam with one‐dimensional chains of corner‐shared SnAs4tetrahedra running in thec ‐direction. Eu5Sn2As6has an impressive room temperature Seebeck of >100 μV/K and < – 100 μV/K at 600 K crossing fromp ‐ ton ‐type at 650 K. The maximum thermoelectric figure of merit,zT , for Eu5Sn2As6is small (0.075), comparable to that of the Zintl phase Ca5Al2Sb6whose thermoelectric performance was improved by doping Na onto the Ca sites. In this study, we show that the thermoelectric properties of Eu5Sn2As6can be improved by substituting with K or La. The series Eu5‐x KxSn2As6provides an increase in maximumzT of 0.22 forx =0.15 due to a decrease resistivity while the onset of bipolar conduction systematically increases in temperature. Upon La substitution, Eu5‐x LaxSn2As6results in a newn ‐type Zintl phase across the temperature range of 300–800 K. -
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d1ma00497b
