Rationally Designing High-Performance Bulk Thermoelectric Materials

Abstract

There has been a renaissance of interest in exploring highly efficient thermoelectric materials as a possible route to address the worldwide energy generation, utilization, and management. This review describes the recent advances in designing high-performance bulk thermoelectric materials. We begin with the fundamental stratagem of achieving the greatest thermoelectric figure of merit ZT of a given material by carrier concentration engineering, including Fermi level regulation and optimum carrier density stabilization. We proceed to discuss ways of maximizing ZT at a constant doping level, such as increase of band degeneracy (crystal structure symmetry, band convergence), enhancement of band effective mass (resonant levels, band flattening), improvement of carrier mobility (modulation doping, texturing), and decrease of lattice thermal conductivity (synergistic alloying, second-phase nanostructuring, mesostructuring, and all-length-scale hierarchical architectures). We then highlight the decoupling of the electron and phonon transport through coherent interface, matrix/precipitate electronic bands alignment, and compositionally alloyed nanostructures. Finally, recent discoveries of new compounds with intrinsically low thermal conductivity are summarized, where SnSe, BiCuSeO, MgAgSb, complex copper and bismuth chalcogenides, pnicogen-group chalcogenides with lone-pair electrons, and tetrahedrites are given particular emphasis. Future possible strategies for further enhancing ZT are considered at the end of this review.

Promising Thermoelectric Bulk Materials with 2D Structures

“…A good thermoelectric material should simultaneously possess high electrical conductivity (σ) to minimize the internal Joule loss, a high Seebeck coefficient (S) to produce high voltage, and low thermal conductivity (κ) to maintain the temperature gradient. [1] To give a clearer criterion, the dimensionless figure www.advmat.de www.advancedsciencenews.com room temperature TE devices, is discussed for its general opti mization method. Then, two typical kinds of bulk materials with 2D structures developed in our group, stacking with the same slabs or different slabs, are examined to determine the detailed transport properties resulting from their structure.…”

“…Interested readers are encouraged to refer to other excellent review papers on TE materials. [1,[76][77][78][79] …”

High thermoelectric performance and low thermal conductivity in Cu2−yS1/3Se1/3Te1/3 liquid-like materials with nanoscale mosaic structures

“…Thermoelectric (TE) materials, which are capable of direct and reversible conversion between heat and electricity, have attracted widespread research interests due to their advantages of no moving parts, no mechanical or chemical processes involved, emission free, high durability, and reliability [1][2][3][4][5]. TE technology shows a great potential in a variety of applications such as spot cooling and power generation using waste heat [6].…”

Phonon-glass electron-crystal behaviour by A site disorder in n-type thermoelectric oxides

“…The identification of the phonon-scattering processes that limit heat conduction in a material has led to a panoscopic approach to reduce κ for PC materials. 4,5 Here κ remains above the minimum thermal conductivity (κmin) expected for a PG, where the thermal conductivity is described by a coupled lattice of harmonic oscillators vibrating with the same frequency but with random phases, and κmin can be calculated using Cahill's model (Equation S9, ESI †) from the number density of atoms (N) and D. 6 The phonon MFP of a PG is much smaller than a PC and remains constant as a function of temperature as all vibrations are localised over interatomic distances.…”

“…23 The nanostructuring approaches used to reduce κ in classical compound semiconductors and intermetallics by increasing grain boundary scattering are inefficient in titanate perovskites as the phonon MFP of SrTiO3 is 2-3 nm, requiring nanometer-sized grains for any noticeable effect on κ. 4,24 Because of this inherently small phonon MFP, the best strategy to reduce κlatt is through the introduction of point defect scattering achieved by substitution. The scattering time for point defects (PD) is added to the other scattering processes according to the Mathiessen rule, 25 and is influenced heavily by the disorder scattering parameter,  = MF + SF, where MF is the mass fluctuation arising from the mass contrast introduced by the defect and SF the strain field induced by ionic radius variance of the defect (Equation S5, ESI †).…”