Tuning the Vacancy Concentration in Lithium Germanium Antimony Tellurides—Influence on Phase Transitions, Lithium Mobility, and Thermoelectric Properties

Schwarzmüller, Stefan; Jakob, Matthias; Nentwig, Markus; Schröder, Thorsten; Kuhn, Alexander; Düvel, André; Heitjans, Paul

doi:10.1021/acs.chemmater.8b03609

Cited by 11 publications

(5 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Some propose that this ultimately causes a reduction of the specific heat capacity. [1,3] The caveat is that the magnitude and temperaturedependence of ionic conduction are not typically reported, [6] so it is not clear how "liquid-like" these materials really are, nor is it clear if the occurrence of ionic transport is fundamentally responsible for the observed low thermal conductivity values Next-generation thermal management requires the development of low lattice thermal conductivity materials, as observed in ionic conductors. For example, thermoelectric efficiency is increased when thermal conductivity is decreased.…”

Section: Introductionmentioning

confidence: 99%

“…algebraically solved for k B T iso (Equation(6), coupling constant N can be related to the characteristic phonon occupation 0  n (which is frequency-dependent following Bose-Einstein). At high isokinetic temperatures, the Bose-Einstein distribution function can be simplified to0 B  ν ≈ n k T h iso ,such that the inverse slope of the phonon occupation model, 0  ν h n , leads to the classical expression of k B T iso .…”

mentioning

confidence: 99%

See 1 more Smart Citation

Considering the Role of Ion Transport in Diffuson‐Dominated Thermal Conductivity

Bernges

Hanus

Wankmiller

et al. 2022

Advanced Energy Materials

View full text Add to dashboard Cite

Next‐generation thermal management requires the development of low lattice thermal conductivity materials, as observed in ionic conductors. For example, thermoelectric efficiency is increased when thermal conductivity is decreased. Detrimentally, high ionic conductivity leads to thermoelectric device degradation. Battery safety and design also require an understanding of thermal transport in ionic conductors. Ion mobility, structural complexity, and anharmonicity have been used to explain the thermal transport properties of ionic conductors. However, thermal and ionic transport are rarely discussed in direct comparison. Herein, the ionic conductivity of Ag+ argyrodites is found to change by orders of magnitude without altering the thermal conductivity. Thermal conductivity measurements and two‐channel lattice dynamics modeling reveal that the majority of Ag+ vibrations have a non‐propagating diffuson‐like character, similar to amorphous materials. It is found that high ionic mobility is not a requirement for diffuson‐mediated transport. Instead, the same bonding and structural traits that can lead to fast ionic conduction also lead to diffuson‐mediated transport. Bridging the fields of solid‐state ionics and thermal transport, it is proposed that a vibrational perspective can lead to new design strategies for functional ionic conducting materials. As a first step, the authors relate the so‐called Meyer–Neldel behavior in ionic conductors to phonon occupations.

show abstract

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Considering the Role of Ion Transport in Diffuson‐Dominated Thermal Conductivity

Bernges

Hanus

Wankmiller

et al. 2022

Advanced Energy Materials

View full text Add to dashboard Cite

show abstract

“…[ 82 ] Therefore, reducing n p is critical to improve the thermoelectric performance of GeTe. Reduced n p can be achieved by aliovalent doping [ 77,113–115 ] and vacancy engineering (including isovalent doping/alloying [ 116 ] and intrinsic Ge vacancy regulation [ 86 ] ).…”

Section: Electrical Transport Properties Optimizationmentioning

confidence: 99%

High‐Performance GeTe‐Based Thermoelectrics: from Materials to Devices

Liu

Wang

et al. 2020

Advanced Energy Materials

198

128

View full text Add to dashboard Cite

m ), [52] enlarging band degeneracy (N V ), [43] and introducing resonant energy levels, [26] can also tune n p effectively. Taking Ge 1−x−y Sb x Zn y Te as an example, Zn doping can reduce the energy offset (ΔE) between L and Σ point. [52] The minimization of thermal transport properties is mainly achieved through suppressing the electrical property-independent κ l . [53][54][55][56][57] Thermoelectric materials with High-performance GeTe-based thermoelectrics have been recently attracting growing research interest. Here, an overview is presented of the structural and electronic band characteristics of GeTe. Intrinsically, compared to lowtemperature rhombohedral GeTe, the high-symmetry and high-temperature cubic GeTe has a low energy offset between L and Σ points of the valence band, the reduced direct bandgap and phonon group velocity, and as a result, high thermoelectric performance. Moreover, their thermoelectric performance can be effectively enhanced through either carrier concentration optimization, band structure engineering (bandgap reduction, band degeneracy, and resonant state engineering), or restrained lattice thermal conductivity (phonon velocity reduction or phonon scattering). Consequently, the dimensionless figure of merit, ZT values, of GeTe-based thermoelectric materials can be higher than 2. The mechanical and thermal stabilities of GeTe-based thermoelectrics are highlighted, and it is found that they are suitable for practical thermoelectric applications except for their high cost. Finally, it is recognized that the performance of GeTe-based materials can be further enhanced through synergistic effects. Additionally, proper material selection and module design can further boost the energy conversion efficiency of GeTe-based thermoelectrics.

show abstract

“…GST materials are perfectly suitable matrix materials as they are characterized by good thermoelectric performance. − In addition, a wide range of substitutions are possible (e.g., Sn, Cd, or Mn for Ge, − Se for Te, or In for Sb). Moreover, the concentration of structural vacancies can be tuned according to 2 M + = vacancy + Ge 2+ ( M = Ag and Li), − e.g., in Li 2 Ge 11 Sb 2 Te 15 . In contrast to Li + and Ag + , Cu + and Au + are known to form very stable binary chalcogenides that can coexist with multinary compounds; thus, the formation of Cu 2– x Te, which may act as a PLEC material, − , is expected with M = Cu in Cu 2 Ge 11 Sb 2 Te 15 .…”

Section: Introductionmentioning

confidence: 99%

Endotaxial Intergrowth of Copper Telluride in GeTe-Rich Germanium Antimony Tellurides Leads to High Thermoelectric Performance

et al. 2022

Self Cite

View full text Add to dashboard Cite

In composite materials with nominal compositions Cu 2 Ge x Sb 2 Te x+4 (11 ≤ x ≤ 18, i.e., between Cu 6.7 Ge 36.7 Sb 6.7 Te 50 and Cu 4.5 Ge 40.9 Sb 4.5 Te 50 ), precipitates consisting of copper tellurides are endotaxially intergrown in a matrix of Cu-doped germanium antimony tellurides. The precipitates as well as the matrix material undergo various phase transitions as shown by temperature-dependent X-ray diffraction and X-ray absorption contrast imaging. Eventually, the precipitates dissolve in the matrix at temperatures exceeding 580 °C. The temperature-dependent behavior was also traced by photoemission electron microscopy up to 460 °C. At high temperatures, the thermoelectric properties are superior to those of pure germanium antimony tellurides obtained by comparable syntheses; a maximal zT value of 1.83 for Cu 2 Ge 16 Sb 2 Te 20 is reached at 500 °C. The application of an effective mass model reveals optimal charge carrier concentrations for all three compositions investigated. The p-type Cu 2 Ge 16 Sb 2 Te 20 material was used in combination with PbTe:In (n-type) to construct a thermoelectric module. Concludingly, the measurement of the Hall effect that suggests no significant changes in Cu-doping levels of the matrix with temperature application of grain boundary optimization and a temperature-induced reset of the microstructure are proposed as strategies for overcoming material degradation upon applying electrical currents.

show abstract

Tuning the Vacancy Concentration in Lithium Germanium Antimony Tellurides—Influence on Phase Transitions, Lithium Mobility, and Thermoelectric Properties

Cited by 11 publications

References 49 publications

Considering the Role of Ion Transport in Diffuson‐Dominated Thermal Conductivity

Considering the Role of Ion Transport in Diffuson‐Dominated Thermal Conductivity

High‐Performance GeTe‐Based Thermoelectrics: from Materials to Devices

Endotaxial Intergrowth of Copper Telluride in GeTe-Rich Germanium Antimony Tellurides Leads to High Thermoelectric Performance

Contact Info

Product

Resources

About