Carrier density control in Cu2HgGeTe4and discovery of Hg2GeTe4viaphase boundary mapping

Ortiz, Brenden R.; Gordiz, Kiarash; Gomes, Lídia C.; Braden, Tara; Adamczyk, Jesse M.; Qu, Jiaxing; Ertekin, Elif; Toberer, Eric S.

doi:10.1039/c8ta10332a

Cited by 29 publications

(39 citation statements)

References 77 publications

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“…It is guided by Gibbs' Phase Rule, which states that the composition of each compound in a multi-phase system is fixed at a given temperature when there are sufficient phases in equilibrium. Applying phase boundary mapping has improved thermoelectric performance in several materials, [28][29][30][31][32][33] including the recent breakthrough of n-type Mg 3 Sb 2 compounds. 21,34 Achieving well-defined phase equilibrium for this technique involves controlling sample composition to the point where secondary phases can be characterized, complicating its applicability in samples that require phase purity, such as single crystals.…”

Section: Methodsmentioning

confidence: 99%

The importance of phase equilibrium for doping efficiency: iodine doped PbTe

et al. 2019

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Section: Methodsmentioning

confidence: 99%

The importance of phase equilibrium for doping efficiency: iodine doped PbTe

et al. 2019

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“…Table 4 compares different GeTe‐based thermoelectric materials synthesized by different method, including high‐vacuum and high‐temperature melting [ 80,127,128,140,144–147 ] or solid‐state reaction [ 148,149 ] method. The high temperature can secure sufficient reaction of precursors to form high‐purity and composition‐homogeneous solid solutions.…”

Section: Materials Preparationmentioning

confidence: 99%

“…After material synthesis, post‐treatments are required to enhance the thermoelectric performance and stability of GeTe‐based thermoelectric materials. Quenching [ 80,128,145 ] and annealing [ 128,149 ] are most commonly used, which can boost the formation of planar vacancies and subsequently enhance the performance of GeTe‐based thermoelectric materials. Furthermore, as‐prepared GeTe powders need to be sintered into pellets for the thermoelectric measurement, characterization and device assembling.…”

Section: Materials Preparationmentioning

confidence: 99%

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

Liu

Wang

et al. 2020

Advanced Energy Materials

185

128

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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.

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“…Once the composition crosses the boundary of single‐phase region in phase diagram, nonstoichiometric defects and secondary phase shall form. Phase‐boundary mapping has been implemented to guide the control of extrinsic doping and off‐stoichiometry,41–46 in which we were able to determine the highest tolerance of off‐stoichiometry for Zintl phases, the maximum filling fraction limits (FFLs) of specific guest elements in skutterudites, and how the variations of nominal composition and the formation of secondary phase affect the TE properties.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Routes to Ultralow Thermal Conductivity and High Thermoelectric Performance

Wei

Liao

et al. 2020

Advanced Materials

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Thermoelectric (TE) research is not only a course of materials by discovery but also a seedbed of novel concepts and methodologies. Herein, the focus is on recent advances in three emerging paradigms: entropy engineering, phase‐boundary mapping, and liquid‐like TE materials in the context of thermodynamic routes. Specifically, entropy engineering is underpinned by the core effects of high‐entropy alloys; the extended solubility limit, the tendency to form a high‐symmetry crystal structure, severe lattice distortions, and sluggish diffusion processes afford large phase space for performance optimization, high electronic‐band degeneracy, rich multiscale microstructures, and low lattice thermal conductivity toward higher‐performance TE materials. Entropy engineering is successfully implemented in half‐Huesler and IV–VI compounds. In Zintl phases and skutterudites, the efficacy of phase‐boundary mapping is demonstrated through unraveling the profound relations among chemical compositions, mutual solubilities of constituent elements, phase instability, microstructures, and resulting TE properties at the operation temperatures. Attention is also given to liquid‐like TE materials that exhibit lattice thermal conductivity at lower than the amorphous limit due to intensive mobile ion disorder and reduced vibrational entropy. To conclude, an outlook on the development of next‐generation TE materials in line with these thermodynamic routes is given.

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Carrier density control in Cu₂HgGeTe₄and discovery of Hg₂GeTe₄viaphase boundary mapping

Abstract: Phase boundary mapping in Cu2HgGeTe4 allows discovery of Hg2GeTe4 and further enables carrier density control over 4 orders of magnitude.

Cited by 29 publications

References 77 publications

The importance of phase equilibrium for doping efficiency: iodine doped PbTe

The importance of phase equilibrium for doping efficiency: iodine doped PbTe

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

Thermodynamic Routes to Ultralow Thermal Conductivity and High Thermoelectric Performance

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