Insights into the Classification of Nanoinclusions of Composites for Thermoelectric Applications

Abstract

Thermoelectric composites are known for their enhanced power conversion performance via interfacial engineering and intensified mechanical, structural, and thermal properties. However, the selection of these nanoinclusions, for example, their type, size effect, volume fraction, distribution uniformity, coherency with host, carrier dynamics, and physical stability, plays a crucial role in modifying the host material thermoelectric properties. In this Review, we classify the nanoinclusions into five types: carbon allotropes, secondary thermoelectric phases, metallic materials, insulating oxides, and others. On the basis of the classification, we discuss the mechanisms involved in improving the ZT of nanocomposites involving reduction of thermal conductivity (κ) by phonon scattering, improving the Seebeck coefficient (α) via energy filtering effect and the electrical conductivity (σ) by carrier injection or carrier channeling. Comprehensibly, we validate that adding nanoinclusions with high electrical and low thermal conductivity as compared to the matrix material is the best way to optimize the interlocked thermoelectric parameters. Thus, collective doping and nanoinclusions in thermoelectric materials is the best possible solution to achieve a higher power conversion efficiency equivalent to other renewable energy technologies.

Enhanced Thermoelectric Properties by Embedding Fe Nanoparticles into CrN Films for Energy Harvesting Applications

“…Several theoretical and experimental studies have suggested new horizons for improving the thermoelectric properties by phonon and carrier engineering using nanoparticle (NP)-containing nanocomposite materials. ,,− In fact, it was suggested that using soft magnetic, typically Fe-based, NPs dispersed in a semiconductor matrix would (i) reduce the thermal conductivity by inserting defects which combined with a Kondo-like effect can increase phonons scattering, (ii) increase the Seebeck coefficient by electron filtering at the metal/semiconductor interface, and (iii) increase the electrical conductivity by modulation doping at the metal/semiconductor interfaces due to the difference in work functions between matrix and NPs …”

Boosting Thermoelectric Performance in Nanocrystalline Ternary Skutterudite Thin Films through Metallic CoTe2 Integration

“…One effective strategy for decoupling these properties involves the manipulation of nanoscale crystallinity and integration of nanostructures into the parent material. This results in the creation of distinctive multiphase structures designed to modify carrier transport. − The presence of a multiphase interface disrupts the heat-carrying phonon movement due to varying thermal transport properties across different lattices, especially at the nanoscale where electron and phonon mean free paths differ significantly. A nanoscale phase with a coherent interface is essential for inducing long-wavelength phonon scattering while preserving the mobility of charge carriers. , The application of such multiphase nanocomposites facilitates synchronized modulation of electron and phonon transport by establishing unique heterojunctions at the interface between the parent matrix and the guest phase …”

Dispersion of InSb Nanoinclusions in Cu3SbS4 for Improved Stability and Thermoelectric Efficiency

“…[24] Indium antimonide (InSb) intermetallic as a nanoinclusions can improve the thermoelectric efficiency of materials and enhance the material's ZT simultaneously. [25][26][27][28][29][30][31][32][33] Semiconducting InSb nanoinclusions are added in both ex situ and in situ manner. Ex situ processing route has advantages in terms of homogeneous distribution, eliminating unwanted secondary phase formations, and controlled particle size in maximizing the interfacial boundary region.…”

“…Ex situ processing route has advantages in terms of homogeneous distribution, eliminating unwanted secondary phase formations, and controlled particle size in maximizing the interfacial boundary region. [25,28,30] Huang et al [26] demonstrated that 3 mol% InSb nanoinclusions in the Cu 12 Sb 4 S 13 matrix enhanced the thermopower via carrier energy filtering and degraded thermal conductivity via phonon scattering for maximized thermoelectric performance. Ghosh et al [27] showed that ex-situ InSb nanoinclusions reduced the CoSb 4 matrix conductivity while improving the thermopower and reducing the thermal conductivity for overall improvement in thermoelectric performance.…”