Evolution of the Structural, Mechanical, and Phonon Properties of GeSe Polymorphs in a Pressure-Induced Second-Order Phase Transition

Yang, Jianhui; Fan, Qiang; Xiao, Bing; Ding, Yingchun

doi:10.3390/ma12213612

Cited by 9 publications

(5 citation statements)

References 35 publications

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“…This in turn suggests that the high-temperature rocksalt structure observed in experiments may be a crystallographic average over locallydistorted R3m domains. The predicted dynamical stability of Pnma GeS/GeSe and R3m GeSe are consistent with previous studies, [76][77][78] as is the instability of rocksalt GeSe. 79 There is, however, an interesting contrast with the analagous rocksalt SnS and SnSe.…”

Section: Structures and Lattice Dynamicssupporting

confidence: 91%

Thermoelectric properties of Pnma and R3m GeS and GeSe

Zhang,

Flitcroft,

Guillemot

et al. 2023

Preprint

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With ∼60 % of global energy lost as heat, technologies such as thermoelectric generators (TEGs) are an important route to enhancing the efficiency of energy-intensive processes. Optimising thermoelectric (TE) materials requires balancing a set of interdependent physical properties to meet efficiency, cost and sustainability requirements, and is a complex materials-design challenge. In this study, we demonstrate a fully first-principles modelling approach to calculating the properties and thermoelectric figure of merit ZT and apply it to the orthorhombic and rhombohedral phases of GeS and GeSe. We predict a large ZTmax = 2.12 for n-doped Pnma GeSe at 900 K, which would make it a good match for p-type SnSe in a thermoelectric couple. In contrast to the more usual p-type doping, the electrical conductivity σ is largest along the layering direction, which would combine with the low κlatt to produce a much larger ZTmax > 3 if the growth direction could be controlled. We also predict that p-doped R3m GeS and GeSe can achieve an industrially-viable ZT > 1, through a high σ counterbalanced by a large thermal conductivity, and experiments indicate this can be further improved by alloying. Our results therefore strongly motivate further study of the under-explored Ge chalcogenides as prospective TEs, with particular focus on strategies for n-doping the Pnma phases.

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Section: Structures and Lattice Dynamicssupporting

confidence: 91%

Thermoelectric properties of Pnma and R3m GeS and GeSe

Zhang,

Flitcroft,

Guillemot

et al. 2023

Preprint

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show abstract

“…This in turn suggests that the high-temperature rocksalt structure observed in experiments may be a crystallographic average over locally-distorted R3m domains. The predicted dynamical stability of Pnma GeS/GeSe and R3m GeSe is consistent with previous studies, [76][77][78] as is the instability of rocksalt GeSe. 79 There is, however, an interesting contrast with the analagous rocksalt SnS and SnSe.…”

Section: Structures and Lattice Dynamicssupporting

confidence: 91%

Thermoelectric properties of Pnma and R3m GeS and GeSe

Zhang,

Flitcroft,

Guillemot

et al. 2023

J. Mater. Chem. C

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“…The lattice thermal conductivity of Pnma structure SnSe also has similar characteristics [ 46 ]. The main reason for the above characteristics of lattice thermal conductivity is that the different phonon group velocities along different direction, as shown in previous research of phonon spectrums [ 23 ]. Similar to SnSe with the same Pnma structure, GeSe also has low lattice thermal conductivity.…”

Section: Resultsmentioning

confidence: 95%

“…We calculate the mode Grüneisen parameter, phonon group velocity, phase velocity and average free path of phonons along the a , b and c directions based on our previous work about phonon spectrum of GeSe [ 23 ]. The Umklapp scattering and boundary scattering are considered in our calculation.…”

Section: Resultsmentioning

confidence: 99%

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Thermoelectric performances for both p- and n-type GeSe

et al. 2021

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In this paper, the thermoelectric properties of p-type and n-type GeSe are studied systematically by using first principles and Boltzmann transport theory. The calculation includes electronic structure, electron relaxation time, lattice thermal conductivity and thermoelectric transport properties. The results show that GeSe is an indirect band gap semiconductor with band gap 1.34 eV. Though p-type GeSe has a high density of states near Fermi level, the electronic conductivity is relative low because there is no carrier transport pathway along the a -axis direction. For n-type GeSe, a charge density channel is formed near conduction band minimum, which improves the electrical conductivity of n-type GeSe along the a -axis direction. At 700 K, the optimal ZT value reaches 2.5 at 4 × 10 19 cm −3 for n-type GeSe, while that is 0.6 at 1 × 10 20 cm −3 for p-type GeSe. The results show n-type GeSe has better thermoelectric properties than p-type GeSe, indicating that n-type GeSe is a promising thermoelectric material in middle temperature.

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Evolution of the Structural, Mechanical, and Phonon Properties of GeSe Polymorphs in a Pressure-Induced Second-Order Phase Transition

Cited by 9 publications

References 35 publications

Thermoelectric properties of Pnma and R3m GeS and GeSe

Thermoelectric properties of Pnma and R3m GeS and GeSe

Thermoelectric properties of Pnma and R3m GeS and GeSe

Thermoelectric performances for both p- and n-type GeSe

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