Thermoelectric, Magnetic, and Mechanical Characteristics of Antiferromagnetic Manganese Telluride Reinforced with Graphene Nanoplates

Abstract

Mechanical and thermal stability are the two challenging aspects of thermoelectric compounds and modules. Microcrack formation during material synthesis and mechanical failure under thermo-mechanical loading is commonly observed in thermoelectric materials made from brittle semiconductors. Herein, the results of graphene-nanoplates (GNPs) reinforcement on the mechanical and thermoelectric properties of MnTe compound are reported. The binary antiferromagnetic MnTe shown promising thermoelectric characteristics due to the paramagnon-hole drag above the Néel temperature. In this study, different bulk MnTe samples are synthesized with the addition of GNPs in a small quantity (0.25-1 wt%) by powder metallurgy and spark plasma sintering. The thermoelectric factors, magnetic behavior, microstructure, and mechanical properties of the samples are evaluated and analyzed. Nearly 33% improvement is observed in the fracture toughness of MnTe reinforced with 0.25 wt% GNPs compared to the pristine structure. The Néel temperature remains approximately unaffected with the GNP inclusion; however, the low-temperature ferromagnetic phase impurity is significantly suppressed. The thermal conductivity and power factor decrease almost equally by %34% at 600 K; hence, the thermoelectric figure-of-merit is not affected by GNP reinforcement in the optimized sample.

Thermal Management Systems and Waste Heat Recycling by Thermoelectric Generators—An Overview

“…The readers are referred to this work [62] for more information since the further discussion is outside the scope of the current paper. Another approach for manipulation of microstructure through reinforcing nanoparticles such as graphene nanoplates (GNPs) has been investigated in previous works of this group [28,63] for two thermoelectric nanocomposites, namely MnTe-GNPs and CoVSn-GNPs (Figure 9). The results revealed an improved modification in the thermoelectric parameters, mainly in the Seebeck coefficients (27% increase) and thermal conductivity (34% decrease) for the samples reinforced with 0.25 wt.% GNPs in comparison to the pristine MnTe samples at the temperature of 600 K. Moreover, dispersion and precipitation of GNPs in the CoVSn multiphase microstructure influenced the thermoelectric factors by reducing the thermal conductivity and increasing the Seebeck coefficient, leading to the Another approach for manipulation of microstructure through reinforcing nanoparticles such as graphene nanoplates (GNPs) has been investigated in previous works of this group [28,63] for two thermoelectric nanocomposites, namely MnTe-GNPs and CoVSn-GNPs (Figure 9).…”

“…Another approach for manipulation of microstructure through reinforcing nanoparticles such as graphene nanoplates (GNPs) has been investigated in previous works of this group [28,63] for two thermoelectric nanocomposites, namely MnTe-GNPs and CoVSn-GNPs (Figure 9). The results revealed an improved modification in the thermoelectric parameters, mainly in the Seebeck coefficients (27% increase) and thermal conductivity (34% decrease) for the samples reinforced with 0.25 wt.% GNPs in comparison to the pristine MnTe samples at the temperature of 600 K. Moreover, dispersion and precipitation of GNPs in the CoVSn multiphase microstructure influenced the thermoelectric factors by reducing the thermal conductivity and increasing the Seebeck coefficient, leading to the Another approach for manipulation of microstructure through reinforcing nanoparticles such as graphene nanoplates (GNPs) has been investigated in previous works of this group [28,63] for two thermoelectric nanocomposites, namely MnTe-GNPs and CoVSn-GNPs (Figure 9). The results revealed an improved modification in the thermoelectric parameters, mainly in the Seebeck coefficients (27% increase) and thermal conductivity (34% decrease) for the samples reinforced with 0.25 wt.% GNPs in comparison to the pristine MnTe samples at the temperature of 600 K. Moreover, dispersion and precipitation of GNPs in the CoVSn multiphase microstructure influenced the thermoelectric factors by reducing the thermal conductivity and increasing the Seebeck coefficient, leading to the enhancement of the thermoelectric figure of merit.…”

“…The change in the thermoelectric factor was attributed to the phonon scattering at the grain boundaries beside carrier filtering against the band bending (Schottky barriers) (see Figure 9d-f). [63] with permission), (c) GNPs precipitation at microstructural barriers of CoVSn compound (adapted from [28] with permission), (d) schematic band alignment of Schottky contact for graphene/n-type semiconductor (adapted from [28] with permission), (e) schematic band alignment of Schottky contact for graphene/p-type semiconductor (adapted from [28] with permission), (f) schematic diagrams of hole trap, hole barrier, electron trap, and electron barrier generated at grain boundaries (adapted from [28] with permission).…”

“…Many more strategies have been studied to enhance the performance of thermoelectric compounds. The examples would be materials selection (as described in Figure 7) [64][65][66], sintering method (e.g., pondermotive force in microwave sintering enhances the diffusion of mobile ionic species and results in accelerating the solid-state reaction by increasing the collision probability) [67], band engineering (e.g., modulation doping, resonance level, and band convergence) [68][69][70][71][72][73][74], carrier pocket engineering [75][76][77], complex structures [78,79], carrier energy filtering [80,81], creation of resonant energy levels close [63] with permission), (c) GNPs precipitation at microstructural barriers of CoVSn compound (adapted from [28] with permission), (d) schematic band alignment of Schottky contact for graphene/n-type semiconductor (adapted from [28] with permission), (e) schematic band alignment of Schottky contact for graphene/p-type semiconductor (adapted from [28] with permission), (f) schematic diagrams of hole trap, hole barrier, electron trap, and electron barrier generated at grain boundaries (adapted from [28] with permission).…”

Assessment of Thermoelectric, Mechanical, and Microstructural Reinforcement Properties of Graphene-Mixed Heterostructures

“…TE characteristics of pristine and graphene-reinforced nanocomposites, (a) Seebeck coefficients, (b) electrical conductivities, (c) lattice thermal conductivity (E and H show the total thermal conductivity), and (d) dimensionless figure of merit ( zT ): (A) Bi 0.85 Sb 0.15 -0.5 wt %G ( T = 280 K), (B) Nb-doped SrTiO 3 -RGO ( T = 800 K), (C) Zn 0.98 Al 0.02 O-1.5 wt %RGO ( T = 900 °C), (D) p -phenediamino-modified graphene (PDG) (RT), (E) CoSb 3 /G ( T = 800 K), (F) LaCoO 3 -0.01 wt % G ( T = 300 K), (G) MnTe-GNPs ( T = 823 K), (H) CuInTe 2 /G (80:1) mass ratio ( T = 700 K), (I) SnSe-3.2 wt % MoS 2 /G ( T = 810 K) …”