Origin of electrical contact resistance and its dominating effect on electrical conductivity in PbTe/CoSb3 composite

Kosonowski, Artur; Kumar, Ashutosh; Wolski, Karol; Zapotoczny, Szczepan; Wojciechowski, Krzysztof

doi:10.1016/j.jeurceramsoc.2022.01.049

Cited by 8 publications

(3 citation statements)

References 43 publications

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“…It is seen that achieving a high zT in a TE material is daunting due to the intertwined relations between these TE parameters. Several innovative strategies have been deployed to decouple electron and phonon transport in material to achieve an elevated zT that includes bandstructure engineering, [3][4][5][6][7] nanostructuring, [8] composite approach, [9][10][11][12] high-entropy concept, [13,14] etc. In other words, concurrent improvement in electronic trans-@ Equal contribution port and prohibition of phonon propagation is the utmost criteria to have high-performance TE materials like PbTe, [15] SnSe, [16] skutterudites, [17] half-Heusler compounds, [18] etc.…”

Section: Introductionmentioning

confidence: 99%

Effect of crystal field engineering and Fermi level optimization on thermoelectric properties of Ge$_{1.01}$Te: Experimental investigation and theoretical insight

Kumar¹,

Bhumla²,

Sivaprahasam³

et al. 2023

Preprint

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This study shows a method of enhancing the thermoelectric properties of GeTe-based materials by Ti and Bi co-doping on cation sites along with self-doping with Ge via simultaneous optimization of electronic (via crystal field engineering, and precise Fermi level optimization) and thermal (via point-defect scattering) transport properties. The pristine GeTe possesses high carrier concentration (n) due to intrinsic Ge vacancies, low Seebeck coefficient (α), and high thermal conductivity (κ). The Ge vacancy optimization and crystal field engineering results in an enhanced α via excess Ge and Ti doping, which is further improved by band structure engineering through Bi doping. As a result of improved α and optimized Fermi level (carrier concentration), an enhanced power factor (α 2 σ) is obtained for Ti-Bi co-doped Ge1.01Te. These experimental results are also evidenced by theoretical calculations of band structure, and thermoelectric parameters using density functional theory and Boltztrap calculations, respectively. A significant reduction in the phonon thermal conductivity (κ ph ) fromat 300 K for Ti-Bi co-doping in GeTe, attributed to point-defect scattering due to mass and strain field fluctuation, in line with the Debye-Callaway model. The phonon dispersion calculations show a decreasing group velocity in Ti-Bi co-doped GeTe, supporting the obtained reduced κ ph . The strategies used in the present study can significantly increase the effective mass, optimize the carrier concentration, and decrease phonon thermal conductivity while achieving an impressive maximum zT value of 1.75 at 773 K and average zT (zTav) of 1.03 for Ge0.91Ti0.02Bi0.08Te over a temperature range of 300-773 K.

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Section: Introductionmentioning

confidence: 99%

Effect of crystal field engineering and Fermi level optimization on thermoelectric properties of Ge$_{1.01}$Te: Experimental investigation and theoretical insight

Kumar¹,

Bhumla²,

Sivaprahasam³

et al. 2023

Preprint

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show abstract

“…The strong coupling between σ, α, and κ e creates a challenge to achieve a high zT in a pristine, unmodified material . The electrical properties have been optimized through several concepts regarding transport mechanisms of charge carriers to achieve enhanced α 2 σ in single-phase materials. − Furthermore, the reduction in κ ph has been presented in the literature through several strategies that amplify phonon scattering, that is, the introduction of lattice defects in the structure, , creation of artificial superlattices, utilization of mass fluctuation/disorder effects, nanostructurization, or preparation of composite materials. , However, such concepts for lowering κ ph will also alter the charge transport and most likely reduce σ due to the scattering of carriers …”

Section: Introductionmentioning

confidence: 99%

“…12,13 However, such concepts for lowering κ ph will also alter the charge transport and most likely reduce σ due to the scattering of carriers. 14 Moreover, the preparation of composite materials is promising for simultaneous optimization of electrical and thermal transport properties to obtain an improved TE performance. This approach allows the utilization of a few transport phenomena that can result in improvement of the σ/ κ ratio.…”

Section: Introductionmentioning

confidence: 99%

Synergistic Effect of Work Function and Acoustic Impedance Mismatch for Improved Thermoelectric Performance in GeTe-WC Composite

Kumar

Bhumla

Kosonowski

et al. 2022

ACS Appl. Mater. Interfaces

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The preparation of composite materials is a promising methodology for concurrent optimization of electrical and thermal transport properties for improved thermoelectric (TE) performance. This study demonstrates how the acoustic impedance mismatch (AIM) and the work function of components decouple the TE parameters to achieve enhanced TE performance of the (1-z)Ge 0.87 Mn 0.05 Sb 0.08 Te-(z)WC composite. The simultaneous increase in the electrical conductivity (σ) and Seebeck coefficient (α) with WC (tungsten carbide) volume fraction (z) results in an enhanced power factor (α 2 σ) in the composite. The rise in σ is attributed to the creation of favorable current paths through the WC phase located between grains of Ge 0.87 Mn 0.05 Sb 0.08 Te, which leads to increased carrier mobility in the composite. Detailed analysis of the obtained electrical properties was performed via Kelvin probe force microscopy (work function measurement) and atomic force microscopy techniques (spatial current distribution map and current−voltage (I−V) characteristics), which are further supported by density functional theory (DFT) calculations. Furthermore, the difference in elastic properties (i.e., sound velocity) between Ge 0.87 Mn 0.05 Sb 0.08 Te and WC results in a high AIM, and hence, a large interface thermal resistance (R int ) between the phases is achieved. The correlation between R int and the Kapitza radius depicts a reduced phonon thermal conductivity (κ ph ) of the composite, which is explained using the Bruggeman asymmetrical model. Moreover, the decrease in κ ph is further validated by phonon dispersion calculations that indicate the decrease in phonon group velocity in the composite. The simultaneous effect of enhanced α 2 σ and reduced κ ph results in a maximum figure of merit (zT) of 1.93 at 773 K for (1z)Ge 0.87 Mn 0.05 Sb 0.08 Te-(z)WC composite for z = 0.010. It results in an average thermoelectric figure of merit (zT av ) of 1.02 for a temperature difference (ΔT) of 473 K. This study shows promise to achieve higher zT av across a wide range of composite materials.

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Improvement of stability in a Mg2Si-based thermoelectric single-leg device via Mg50Si15Ni50 barrier

Chen

Fan

Wang

et al. 2022

Journal of Alloys and Compounds

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Origin of electrical contact resistance and its dominating effect on electrical conductivity in PbTe/CoSb3 composite

Cited by 8 publications

References 43 publications

Effect of crystal field engineering and Fermi level optimization on thermoelectric properties of Ge$_{1.01}$Te: Experimental investigation and theoretical insight

Effect of crystal field engineering and Fermi level optimization on thermoelectric properties of Ge$_{1.01}$Te: Experimental investigation and theoretical insight

Synergistic Effect of Work Function and Acoustic Impedance Mismatch for Improved Thermoelectric Performance in GeTe-WC Composite

Improvement of stability in a Mg2Si-based thermoelectric single-leg device via Mg50Si15Ni50 barrier

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