Relationship between composition and charge carrier concentration in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Eu</mml:mi><mml:mn>8</mml:mn></mml:msub><mml:msub><mml:mi>Ga</mml:mi><mml:mrow><mml:mn>16</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Ge</mml:mi><mml:mrow><mml:mn>30</mml:mn><mml:mo>+</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math>clathrates

Pacheco, V.; Bentien, Anders; Carrillo‐Cabrera, W.; Paschen, S.; Steglich, F.; Grin, Yu.

doi:10.1103/physrevb.71.165205

Cited by 65 publications

(21 citation statements)

References 36 publications

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“…To our satisfaction, almost at the same time we first submitted this manuscript the research group from Dresden published two excellent works [15,16] describing how their polycrystalline Eu 8 Ga 16 Ge 30 samples can be tuned with respect to composition, carrier concentration and thermoelectric properties, although in their case only ntype samples were found. Their results also challenge the current "tunneling" models for glass-like thermal conductivity (which we mentioned in the introduction section) attributing this low-temperature behavior to phonon-charge-carrier scattering instead.…”

Section: Resultsmentioning

confidence: 99%

Tunable charge carriers and thermoelectricity of single-crystal Ba₈Ga₁₆Sn₃₀

Ávila¹,

Huo²,

Sakata³

et al. 2006

J. Phys.: Condens. Matter

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We have grown single crystals of the type-VIII intermetallic clathrate Ba 8 Ga 16 Sn 30 from both Sn and Ga flux, evaluated their compositions through electron microprobe analysis and studied their transport properties through measurements on temperature dependent resistivity, thermopower and Hall coefficient. Crystals grown in Sn flux show n-type carriers and those from Ga flux show p-type carriers, whereas all measured compositions remain very close to the stoichiometric 8:16:30 proportion of Ba:Ga:Sn, expected from charge-balance principles. Our results indicate a very high sensitivity of the charge carrier nature and density with respect to the growth conditions, leading to relevant differences in transport properties which point to the importance of tuning this material for optimal thermoelectric performance.

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Section: Resultsmentioning

confidence: 99%

Tunable charge carriers and thermoelectricity of single-crystal Ba₈Ga₁₆Sn₃₀

Ávila¹,

Huo²,

Sakata³

et al. 2006

J. Phys.: Condens. Matter

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“…One proposes that the tunnelling states are not required, only an off-center vibration of the guest ions, 13,14 and another proposes that the guest ions don't play a major role at all at low temperatures, but rather it is the phonon scattering on charge carriers that leads to the glasslike behavior. 15,16,17,18 In this work we address the issue by performing single crystal x-ray diffraction (SCXRD), thermal conductivity κ(T ) and heat capacity C p (T ) experiments on Ba 8 Ga 16 Sn 30 (BGS) and Ba 8 Ga 16 Ge 30 (BGG) crystals, which have been tuned through the crystal growth process to display n-type or p-type majority charge carriers as a result of small imbalances in their Ga:Ge or Ga:Sn ratios. 19,20 By analyzing the differences and similarities between the behaviors of these samples, we can test the applicability of the various models proposed to explain the origin of unusual glasslike behavior, in this case observed for p-type samples whereas the n-type samples show the normal crystalline peak.…”

Section: Fig 1: (Color Online)mentioning

confidence: 99%

Glasslike versus crystalline thermal conductivity in carrier-tunedBa8Ga16X30clathrates(X<

et al. 2006

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The present controversy over the origin of glasslike thermal conductivity observed in certain crystalline materials is addressed by studies on single-crystal x-ray diffraction, thermal conductivity κ(T ) and specific heat Cp(T ) of carrier-tuned Ba8Ga16X30 (X = Ge, Sn) clathrates. These crystals show radically different low-temperature κ(T ) behaviors depending on whether their charge carriers are electrons or holes, displaying the usual crystalline peak in the former case and an anomalous glasslike plateau in the latter. In contrast, Cp(T ) above 4 K and the general structural properties are essentially insensitive to carrier tuning. We analyze these combined results within the framework of a Tunneling/Resonant/Rayleigh scatterings model, and conclude that the evolution from crystalline to glasslike κ(T ) is accompanied by an increase both in the effective density of tunnelling states and in the resonant scattering level, while neither one of these contributions can solely account for the observed changes in the full temperature range. This suggests that the most relevant factor which determines crystalline or glasslike behavior is the coupling strength between the guest vibrational modes and the frameworks with different charge carriers.

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“…20,22,23,24,25 These results appear inconsistent with the idea of the guest ion vibration having the relevant role in producing the glass-like behavior. An alternate model 20,24,26,27 based on phonon-scattering by charge carriers 28 was proposed instead, and the question of which factors are dominant at low temperatures remains a currently open debate.…”

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confidence: 99%

Cage-size control of guest vibration and thermal conductivity inSr8Ga16Si30−xGex
Suekuni
¹
,
Ávila
²
,
Umeo
³

et al. 2007
Phys. Rev. B
119
15
101
0
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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 Sr8Ga16Si30−xGex, 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 10.726Å, and the localized vibrational energies of the Sr guest ions in the tetrakaidekahedron (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 glass-like 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 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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Relationship between composition and charge carrier concentration inEu8Ga16−xGe30+xclathrates

Cited by 65 publications

References 36 publications

Tunable charge carriers and thermoelectricity of single-crystal Ba₈Ga₁₆Sn₃₀

Tunable charge carriers and thermoelectricity of single-crystal Ba₈Ga₁₆Sn₃₀

Glasslike versus crystalline thermal conductivity in carrier-tunedBa8Ga16X30clathrates(X<

Cage-size control of guest vibration and thermal conductivity inSr8Ga16Si30−xGex
Suekuni
¹
,
Ávila
²
,
Umeo
³

et al. 2007
Phys. Rev. B
119
15
101
0
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Relationship between composition and charge carrier concentration inEu8Ga16−xGe30+xclathrates

Cited by 65 publications

References 36 publications

Tunable charge carriers and thermoelectricity of single-crystal Ba8Ga16Sn30

Tunable charge carriers and thermoelectricity of single-crystal Ba8Ga16Sn30

Glasslike versus crystalline thermal conductivity in carrier-tunedBa8Ga16X30clathrates(X<

Cage-size control of guest vibration and thermal conductivity inSr8Ga16Si30−xGexSuekuni1, Ávila2, Umeo3 et al. 2007Phys. Rev. B119151010View full textAdd to dashboardCite

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Tunable charge carriers and thermoelectricity of single-crystal Ba₈Ga₁₆Sn₃₀

Tunable charge carriers and thermoelectricity of single-crystal Ba₈Ga₁₆Sn₃₀

Cage-size control of guest vibration and thermal conductivity inSr8Ga16Si30−xGex
Suekuni
¹
,
Ávila
²
,
Umeo
³

et al. 2007
Phys. Rev. B
119
15
101
0
View full text Add to dashboard Cite