Abstract
We present a systematic study of thermal conductivity, specific heat, electrical resistivity, thermopower, and x-ray diffraction measurements performed on single-crystalline samples of the pseudoquaternary type-I clathrate system Sr8 Ga16 Si30-x Gex, in the full range of 0≤x≤30. All the samples show metallic behavior with n -type majority carriers. However, the thermal conductivity and specific heat strongly depend on x. Upon increasing x from 0 to 30, the lattice parameter increases by 3%, from 10.446 to 10.726 Å, and the localized vibrational energies of the Sr guest ions in the tetrakaidecahedron (dodecahedron) cages decrease from 59 (120) K to 35 (90) K. Furthermore, the lattice thermal conductivity at low temperatures is largely suppressed. In fact, a crystalline peak found at 15 K for x=0 gradually decreases and disappears for x≥20, evolving into the anomalous glasslike behavior observed for x=30. It is found that the increase of the free space for the Sr guest motion directly correlates with a continuous transition from quasi-on-center harmonic vibration to off-center anharmonic vibration, with consequent increase in the coupling strength between the guest's low-energy modes and the cage's acoustic phonon modes.
| Original language | English |
|---|---|
| Article number | 195210 |
| Journal | Physical Review B - Condensed Matter and Materials Physics |
| Volume | 75 |
| Issue number | 19 |
| DOIs | |
| Publication status | Published - May 21 2007 |
| Externally published | Yes |
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All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
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Cage-size control of guest vibration and thermal conductivity in Sr8 Ga16 Si30-x Gex. / Suekuni, Koichiro; Avila, M. A.; Umeo, K.; Takabatake, T.
In: Physical Review B - Condensed Matter and Materials Physics, Vol. 75, No. 19, 195210, 21.05.2007.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Cage-size control of guest vibration and thermal conductivity in Sr8 Ga16 Si30-x Gex
AU - Suekuni, Koichiro
AU - Avila, M. A.
AU - Umeo, K.
AU - Takabatake, T.
PY - 2007/5/21
Y1 - 2007/5/21
N2 - We present a systematic study of thermal conductivity, specific heat, electrical resistivity, thermopower, and x-ray diffraction measurements performed on single-crystalline samples of the pseudoquaternary type-I clathrate system Sr8 Ga16 Si30-x Gex, in the full range of 0≤x≤30. All the samples show metallic behavior with n -type majority carriers. However, the thermal conductivity and specific heat strongly depend on x. Upon increasing x from 0 to 30, the lattice parameter increases by 3%, from 10.446 to 10.726 Å, and the localized vibrational energies of the Sr guest ions in the tetrakaidecahedron (dodecahedron) cages decrease from 59 (120) K to 35 (90) K. Furthermore, the lattice thermal conductivity at low temperatures is largely suppressed. In fact, a crystalline peak found at 15 K for x=0 gradually decreases and disappears for x≥20, evolving into the anomalous glasslike behavior observed for x=30. It is found that the increase of the free space for the Sr guest motion directly correlates with a continuous transition from quasi-on-center harmonic vibration to off-center anharmonic vibration, with consequent increase in the coupling strength between the guest's low-energy modes and the cage's acoustic phonon modes.
AB - We present a systematic study of thermal conductivity, specific heat, electrical resistivity, thermopower, and x-ray diffraction measurements performed on single-crystalline samples of the pseudoquaternary type-I clathrate system Sr8 Ga16 Si30-x Gex, in the full range of 0≤x≤30. All the samples show metallic behavior with n -type majority carriers. However, the thermal conductivity and specific heat strongly depend on x. Upon increasing x from 0 to 30, the lattice parameter increases by 3%, from 10.446 to 10.726 Å, and the localized vibrational energies of the Sr guest ions in the tetrakaidecahedron (dodecahedron) cages decrease from 59 (120) K to 35 (90) K. Furthermore, the lattice thermal conductivity at low temperatures is largely suppressed. In fact, a crystalline peak found at 15 K for x=0 gradually decreases and disappears for x≥20, evolving into the anomalous glasslike behavior observed for x=30. It is found that the increase of the free space for the Sr guest motion directly correlates with a continuous transition from quasi-on-center harmonic vibration to off-center anharmonic vibration, with consequent increase in the coupling strength between the guest's low-energy modes and the cage's acoustic phonon modes.
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U2 - 10.1103/PhysRevB.75.195210
DO - 10.1103/PhysRevB.75.195210
M3 - Article
VL - 75
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
SN - 1098-0121
IS - 19
M1 - 195210
ER -