Abstract
Thermoelectric technology, which possesses potential application in recycling industrial waste heat as energy, calls for novel high-performance materials. The systematic exploration of novel thermoelectric materials with excellent electronic transport properties is severely hindered by limited insight into the underlying bonding orbitals of atomic structures. Here we propose a simple yet successful strategy to discover and design high-performance layered thermoelectric materials through minimizing the crystal field splitting energy of orbitals to realize high orbital degeneracy. The approach naturally leads to design maps for optimizing the thermoelectric power factor through forming solid solutions and biaxial strain. Using this approach, we predict a series of potential thermoelectric candidates from layered CaAl2Si2-type Zintl compounds. Several of them contain nontoxic, low-cost and earth-abundant elements. Moreover, the approach can be extended to several other non-cubic materials, thereby substantially accelerating the screening and design of new thermoelectric materials.
Highlights
Thermoelectric technology, which possesses potential application in recycling industrial waste heat as energy, calls for novel high-performance materials
The performance of TE materials is governed by the dimensionless figure of merit, zT 1⁄4 a2sT/k, where a is the Seebeck coefficient, s is the electrical conductivity, k is the thermal conductivity and T is the absolute temperature
Enhanced zT value requires a combination of excellent electrical transport properties, quantified by the TE power factor PF 1⁄4 a2s, and low thermal conductivity
Summary
Thermoelectric technology, which possesses potential application in recycling industrial waste heat as energy, calls for novel high-performance materials. The approach naturally leads to design maps for optimizing the thermoelectric power factor through forming solid solutions and biaxial strain Using this approach, we predict a series of potential thermoelectric candidates from layered CaAl2Si2-type Zintl compounds. Despite the intuitive appeal of this approach, it has only been applied to a few cubic or pseudo-cubic alloys This might be attributed to the limited insight into the underlying bonding orbitals at the band edges, which makes it difficult to extend the approach to new materials. We identify a few promising TE candidates with nontoxic, inexpensive and earth-abundant elements from CaAl2Si2-type Zintl compounds It is shown how the selection rule naturally leads to strategies for rationally optimizing the TE PF through solid solution map and biaxial strain engineering. The orbital engineering approach presented here provides insightful guidance for the search and design of novel promising TE materials with good electronic transport properties
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