Abstract
We investigate the transport properties of bulk Ca2YZ (Y = Au, Hg; Z = As, Sb, Bi, Sn and Pb) by a combination method of first-principles and Boltzmann transport theory. The focus of this article is the systematic study of the thermoelectric properties under the effect of a spin–orbit coupling. The highest dimensionless figure of merit (ZT) of Ca2AuAs at optimum carrier concentration are 1.23 at 700 K. Interestingly enough, for n-type Ca2HgPb, the maximum ZT are close to each other from 500 K to 900 K and these values are close to 1, which suggests that semimetallic material can also be used as an excellent candidate for thermoelectric materials. From another viewpoint, at room temperature, the maximum PF for Ca2YZ are greater than 3 mW m−1 K−2, which is very close to that of ∼3 mW m−1 K−2 for Bi2Te3 and ∼4 mW m−1 K−2 for Fe2VAl. However, the room temperature theoretical κl of Ca2YZ is only about 0.85–1.6 W m−1 K−1, which is comparing to 1.4 W m−1 K−1 for Bi2Te3 and remarkably lower than 28 W m−1 K−1 for Fe2VAl at same temperature. So Ca2YZ should be a new type of promising thermoelectric material at room temperature.
Highlights
Thermoelectric (TE) materials, which can generate electricity from waste heat or be used as solid-state Peltier coolers, are considered for a variety of energy harvesting and thermal management applications.[1,2,3] The efficiency of TE materials is described by the dimensionless gure of merit ZT, which is de ned as ZT 1⁄4 S2sT/(ke + kl), where S is the Seebeck coefficient, s is the electrical conductivity (S2s known as the power factor, PF), T is the absolute temperature, and ke and kl are the electronic and lattice contributions to the thermal conductivity, respectively
The most signi cant thing is that at room temperature, the maximum value of PFS for Ca2YZ is PF S 3 mW mÀ1 KÀ2, which is similar to that of $3 mW mÀ1 KÀ2 for Bi2Te3 and $4 mW mÀ1 KÀ2 for Fe2VAl.[9,10,11]
The main focus of this study is a new family of intermetallic compounds with ten valence electrons Ca2YZ (Y 1⁄4 Au and Hg; Z 1⁄4 As, Sb, Bi, Sn and Pb), which was discovered through highthroughput ab initio screening.[17]
Summary
Thermoelectric (TE) materials, which can generate electricity from waste heat or be used as solid-state Peltier coolers, are considered for a variety of energy harvesting and thermal management applications.[1,2,3] The efficiency of TE materials is described by the dimensionless gure of merit ZT, which is de ned as ZT 1⁄4 S2sT/(ke + kl), where S is the Seebeck coefficient, s is the electrical conductivity (S2s known as the power factor, PF), T is the absolute temperature, and ke and kl are the electronic and lattice contributions to the thermal conductivity, respectively. There are two ways to improve the ZT of thermoelectric materials: one way is to enhance the PF, the other one is to suppress the thermal conductivity. 20) and Fe2VAl.[9,10,11] The most signi cant thing is that at room temperature, the maximum value of PFS for Ca2YZ is PF S 3 mW mÀ1 KÀ2, which is similar to that of $3 mW mÀ1 KÀ2 for Bi2Te3 20) and $4 mW mÀ1 KÀ2 for Fe2VAl.[9,10,11] And at room temperature, the theoretical kl of Ca2YZ is estimated to be about 0.85–1.6 W mÀ1 KÀ1.17 At the same temperature, the value is comparable to those of known thermoelectric materials i.e., 1.4 W mÀ1 KÀ1 for Bi2Te3 Ca2YZ should be a new promising material for thermoelectric applications
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