Phonon spectra in superionic and normal states of the layered crystal AgCrSe2

Wakamura, Kunio; Hirokawa, Kojiro; Shima, Hiromi; Takarabe, Kenichi

doi:10.1016/0167-2738(90)90353-s

Cited by 11 publications

(4 citation statements)

References 3 publications

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“…Three phonons are observed with smaller oscillations between 5 meV and 15 meV. corresponding to the three infrared active optical phonons expected for AgCrSe 2 [18,19]. Each of the modes shows significant temperature dependence, broadening as the temperature is increased.…”

Section: Resultsmentioning

confidence: 76%

“…At low temperatures the Ag ions form a regular triangular lattice, while at high temperatures a second triangular lattice becomes partially occupied, forming a honeycomb lattice. There are six infrared active phonons associated with this structure, of which three are in-plane modes [18]. The phonon dispersions and partial phonon density of states have been previously calculated in Refs.…”

Section: Discussionmentioning

confidence: 89%

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Optical phonons and magnetoelastic coupling in the ionic conductor AgCrSe2

Groefsema

Feng

Morice

et al. 2022

Phys. Rev. Materials

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AgCrSe 2 is an example of a superionic conductor that has recently attracted attention for its low thermal conductivity. Here we investigate the optical properties of AgCrSe 2 in the ordered phase between 14 K and 374 K using reflectivity experiments and compare them to the optical conductivity obtained from electronic structure calculations. The far infrared optical response is dominated by three phonon modes, while six interband transitions are observed in the visible range. We find good agreement between the experimental interband transitions and the calculated optical transitions. From our analysis we find that the phonon parameters display an interesting temperature dependence around the Néel temperature, pointing to a small magnetoelastic coupling. In addition, the lifetimes of the modes indicate that three-phonon processes dominate and the optical phonons decay into low-energy acoustic modes involved in the superionic transition. Finally, we detect a small free charge carrier response through the analysis of Fabry-Perot interference fringes in our reflectivity data.

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Section: Resultsmentioning

confidence: 76%

Section: Discussionmentioning

confidence: 89%

Optical phonons and magnetoelastic coupling in the ionic conductor AgCrSe2

Groefsema

Feng

Morice

et al. 2022

Phys. Rev. Materials

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“…To study the response of optical vibrations in the normal and superionic phases, we performed temperature dependent Raman spectroscopy from 3–550 K (Figure a and b). The four atoms in a unit cell result in 12 vibrational modes, with A 1 and E being the possible mode symmetries . In AgCrSe 2 at low temperatures (∼3 K and above), six Raman active modes are observed: two low frequency M1 (∼28 cm –1 ) and M2 (∼36 cm –1 ) modes lying very close to the Rayleigh line and having weak intensity.…”

Section: Resultsmentioning

confidence: 99%

“…The four atoms in a unit cell result in 12 vibrational modes, with A 1 and E being the possible mode symmetries. 29 In AgCrSe 2 at low temperatures (∼3 K and above), six Raman active modes are observed: two low frequency M1 (∼28 cm −1 ) and M2 (∼36 cm −1 ) modes lying very close to the Rayleigh line and having weak intensity. However, these modes are clearly visible in the polarization dependent spectra (Figure S7).…”

Section: Raman Spectroscopy Studymentioning

confidence: 94%

Anharmonic Phonon Vibrations of Ag and Cu for Poor Lattice Thermal Conductivity in Superionic AgCrSe₂ and CuCrSe₂

Rana,

Singh,

Bhui

et al. 2024

ACS Appl. Energy Mater.

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Solids generally possess higher thermal conductivity compared to liquids, as heat energy in solids is conducted through both transverse and longitudinal vibrations, whereas, the heat conduction in liquids is mainly reliant on the longitudinal vibrations. Here, we report the ultralow lattice thermal conductivity (k l ) and high thermoelectric (TE) performance in layered Ag(Cu)CrSe 2 attributed to the strong crystal anharmonicity caused by the weakly bounded Ag(Cu) + ions, following phonon-liquid electron-crystal concept. The low-frequency Raman vibrations vanish as the kinetically disordered state due to Ag(Cu) + ions starts appearing, showing the influence toward the vibrational properties. The strong acoustic-low energetic optical interactions, poor transverse and mean sound velocities, low-frequency rattling-like vibrations, a broad boson-like peak, and high Gruneisen parameter make AgCrSe 2 a poorer thermal conductor than CuCrSe 2 . Overall, at high temperatures, we observed ultralow k l ∼ 0.3 W m −1 K −1 for AgCrSe 2 and ∼0.5 W m −1 K −1 for CuCrSe 2 , along with high TE figures of merit ∼0.83 and ∼0.61, respectively, indicating their potential suitability for applications requiring poor thermal conductivity and high TE performance.

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Observation of characteristic phonon spectra for cage and mobile ions in the layered superionic conductor AgCrS2

Wakamura

Hirokawa

Orita

1996

Journal of Physics and Chemistry of Solids

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Phonon spectra in superionic and normal states of the layered crystal AgCrSe2

Cited by 11 publications

References 3 publications

Optical phonons and magnetoelastic coupling in the ionic conductor AgCrSe2

Optical phonons and magnetoelastic coupling in the ionic conductor AgCrSe2

Anharmonic Phonon Vibrations of Ag and Cu for Poor Lattice Thermal Conductivity in Superionic AgCrSe₂ and CuCrSe₂

Observation of characteristic phonon spectra for cage and mobile ions in the layered superionic conductor AgCrS2

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Phonon spectra in superionic and normal states of the layered crystal AgCrSe2

Cited by 11 publications

References 3 publications

Optical phonons and magnetoelastic coupling in the ionic conductor AgCrSe2

Optical phonons and magnetoelastic coupling in the ionic conductor AgCrSe2

Anharmonic Phonon Vibrations of Ag and Cu for Poor Lattice Thermal Conductivity in Superionic AgCrSe2 and CuCrSe2

Observation of characteristic phonon spectra for cage and mobile ions in the layered superionic conductor AgCrS2

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Anharmonic Phonon Vibrations of Ag and Cu for Poor Lattice Thermal Conductivity in Superionic AgCrSe₂ and CuCrSe₂