Thermal Conductivity of Molecular Crystal with Various Types of Chemical Bonding: Quasi-One-Dimensional Organic Superconductor (DMET)<sub>2</sub>AuI<sub>2</sub>

Iwasaki, Yoshiki; Yoshino, Hideaki; Kuroda, Natsuki; Kikuchi, Kôichi; Murata, Keizo

doi:10.7566/jpsj.84.054601

Cited by 8 publications

(9 citation statements)

References 31 publications

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“…Thermal conductivities were measured by using the comparative steady-state method with aM anganin wire (f= 50 mm)f ollowing the scheme of Yoshino et al (see the Supporting Information). [2,9] Te mperature-dependent heat capacities were measured by the relaxation method by using ac ustom-built apparatus (see the Supporting Information). DSC measurements were carried out by using aR igaku Thermo plus DSC8120 and aM ettler DSC1 instrument.…”

Section: Methodsmentioning

confidence: 99%

“…Unfortunately, the thermal conductivities of such crystals have rarely been measured because commonly used thermal conductivity meters generally require centimeter‐sized bulk or film samples . Recently, the thermal conductance of several molecular crystals has been measured by using instruments that can accommodate sub‐millimeter samples . These measurements demonstrated anomalous thermal conductance behavior in the crystals of fullerenes, 4‐bromobenzophenone, and substituted benzenes .…”

Section: Introductionmentioning

confidence: 99%

“…[1] Recently,t he thermalc onductance of several molecular crystals has been measured by using instrumentst hat can accommodate sub-millimeter samples. [1][2][3][4][5][6][7][8][9][10] These measurements demonstrated anomalous thermal conductanceb ehavior in the crystalso ff ullerenes, 4-bromobenzophenone, and substituted benzenes. [11][12][13] These crystals show transitions from as tatic to ar otational phase, which is considered to be am esophase between the anisotropic crystalsa nd an isotropic liquid.…”

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confidence: 99%

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Negative‐to‐Positive Thermal Conductivity Temperature Coefficient Transition Induced by Dynamic Fluctuations of the Alkyl Chains in the Layered Complex (C₄H₉NH₃)₂CuCl₄

Hoshino

Tamura

Akutagawa

2020

Chemistry A European J

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A negative‐to‐positive transition of the temperature coefficients of thermal conductivity was found in the two‐dimensional organic–inorganic layered complex (C4H9NH3)2CuCl4 (C4CuCl4) over the three structural phase transitions in the range 176–218 K. The coefficients of the low‐temperature phases (85–200 K, α and β phases) were negative, as is typical for insulating crystals, whereas those of the high‐temperature phases (200–300 K, γ and δ phases) were positive, as is typical for glasses and liquids. Single‐crystal X‐ray structure analyses revealed that the tilted C4H9NH3+ chains in the α and β phases were fully outstretched in the δ phase, and the interlayer distances between the CuCl42− planes increased significantly. The γ phase was an intermediate phase that crystallized with an incommensurate structure, in which the CuCl42− sheets formed wave‐like structures consisting of connected alternating regions of β‐like and δ‐like moieties. In the γ and δ phases, thermal fluctuations of the C4H9NH3+ chains were found in the electron density maps; however, powder X‐ray diffraction (PXRD) data indicated that the thermal expansion of the C4H9NH3+ layers was restricted by the rigid CuCl42− layers. This situation was considered to induce glass‐like thermal conducting properties in the material, such as a positive temperature coefficient. The mean free path of the phonons estimated by using the thermal conductivities and heat capacities was a function of T−1 in the range 85–200 K, as would be expected for crystals, whereas it was approximately constant in the range 200–300 K, which is typical of glasses. In addition, the existence of soft vibration modes in the two‐dimensional perovskite CuCl42− sheets was revealed by analysis of the incommensurate crystal structure of the γ phase. These low‐energy vibration modes were believed to induce the cooperative phase transitions, along with the thermal fluctuations and van der Waals interactions in the C4H9NH3+ layers.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Negative‐to‐Positive Thermal Conductivity Temperature Coefficient Transition Induced by Dynamic Fluctuations of the Alkyl Chains in the Layered Complex (C₄H₉NH₃)₂CuCl₄

Hoshino

Tamura

Akutagawa

2020

Chemistry A European J

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“…The present measurements are essentially the same as described in literature. 24,25) After measuring the transport properties, we examined the iodine content in each crystal by X-ray diffraction measurement at Kyoto University. The gold-evaporated parts of the three samples (#1602, #1701, and #1704) were cut out before the measurement, and the size of the crystals was reduced to 0.26 × 0.08 × 0.06 mm 3 , 0.27 × 0.07 × 0.04 mm 3 and 0.20 × 0.10 × 0.04 mm 3 , respectively.…”

Section: Methodsmentioning

confidence: 99%

Disorder-Enhanced Dimensionless Thermoelectric Figure of Merit zT of Non-stoichiometric Organic Conductor (TTT)₂I_3+δ (δ ≤ 0.1)

et al. 2019

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Sample dependence of dimensionless thermoelectric figure of merit (zT ) and power factor (PF) were determined for the non-stoichiometric organic conductor (TTT) 2 I 3+δ (TTT = tetrathiatetracene, δ ≤ 0.1) with the simultaneous measurement of the electrical resistivity (ρ), thermopower (S ) and thermal conductivity on small single crystals. Both the zT and PF show large sample dependence between 10 and 310 K, even though all the samples have nearly stoichiometric composition of TTT:I − 3 ∼ 2:1 (δ ∼ 0). It was found that both the electrical conductivity (σ = 1/ρ) and S increase at room temperature as disorder -that is phase mismatch among the iodine chains -becomes more pronounced. This behavior contrasts the usual tendency that the S decreases as the σ increases in conventional conductors; and suggests a new strategy to improve the zT and PF by introducing an appropriate type of disorder.

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“…3a, the as-measured κ of pristine BOS (S1-orange stars) exhibits a broad phonon peak at about 8 K and decreases with increasing T up to 100 K. Further heating leads to an upturn up to 400 K. We may not ascribe this upturn to ambipolar thermal conductivity from thermally excited electron-hole pairs 35,36 , given the large energy gap (∆ ≈ 0.8 eV) of BOS. In the measurements of materials with low κ, the radiation loss may not be neglected, which will lead to the overestimation of thermal conductivity, especially at high temperatures [37][38][39] . The radiation loss from the sample to the environment can be estimated by Stefan-Boltzmann law:…”

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confidence: 99%

Thermoelectric properties of Bi2O2Se single crystals

Wang,

Hu,

Lou

et al. 2021

Preprint

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Bismuth oxyselenide (Bi 2 O 2 Se) attracts great interest as a potential n-type complement to p-type thermoelectric oxides in practical applications. Previous investigations were generally focused on polycrystals. Here, we performed a study on the thermoelectric properties of Bi 2 O 2 Se single crystals. Our samples exhibit electron mobility as high as 250 cm 2 .V −1 .s −1 and thermal conductivity as low as 2 W.m −1 .K −1 near room temperature. The maximized figure of merit is yielded to be 0.188 at 390 K, higher than that of polycrystals. Consequently, a rough estimation of the phonon mean free path ( ph ) from the kinetic model amounts to 12 Å at 390 K and follows a T −1 behavior. An extrapolation of ph to higher temperatures indicates that this system approaches the Ioffe-Regel limit at about 1100 K. In light of the phonon dispersions, we argue that the ultralow ph is attributed to intense anharmonic phonon-phonon scattering, including Umklapp process and acoustic to optical phonon scattering. Our results suggest that single crystals provide a further improvement of thermoelectric performance of Bi 2 O 2 Se.

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Thermal Conductivity of Molecular Crystal with Various Types of Chemical Bonding: Quasi-One-Dimensional Organic Superconductor (DMET)₂AuI₂

Cited by 8 publications

References 31 publications

Negative‐to‐Positive Thermal Conductivity Temperature Coefficient Transition Induced by Dynamic Fluctuations of the Alkyl Chains in the Layered Complex (C₄H₉NH₃)₂CuCl₄

Negative‐to‐Positive Thermal Conductivity Temperature Coefficient Transition Induced by Dynamic Fluctuations of the Alkyl Chains in the Layered Complex (C₄H₉NH₃)₂CuCl₄

Disorder-Enhanced Dimensionless Thermoelectric Figure of Merit zT of Non-stoichiometric Organic Conductor (TTT)₂I_3+δ (δ ≤ 0.1)

Thermoelectric properties of Bi2O2Se single crystals

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Thermal Conductivity of Molecular Crystal with Various Types of Chemical Bonding: Quasi-One-Dimensional Organic Superconductor (DMET)2AuI2

Cited by 8 publications

References 31 publications

Negative‐to‐Positive Thermal Conductivity Temperature Coefficient Transition Induced by Dynamic Fluctuations of the Alkyl Chains in the Layered Complex (C4H9NH3)2CuCl4

Negative‐to‐Positive Thermal Conductivity Temperature Coefficient Transition Induced by Dynamic Fluctuations of the Alkyl Chains in the Layered Complex (C4H9NH3)2CuCl4

Disorder-Enhanced Dimensionless Thermoelectric Figure of Merit zT of Non-stoichiometric Organic Conductor (TTT)2I3+δ (δ ≤ 0.1)

Thermoelectric properties of Bi2O2Se single crystals

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Thermal Conductivity of Molecular Crystal with Various Types of Chemical Bonding: Quasi-One-Dimensional Organic Superconductor (DMET)₂AuI₂

Negative‐to‐Positive Thermal Conductivity Temperature Coefficient Transition Induced by Dynamic Fluctuations of the Alkyl Chains in the Layered Complex (C₄H₉NH₃)₂CuCl₄

Negative‐to‐Positive Thermal Conductivity Temperature Coefficient Transition Induced by Dynamic Fluctuations of the Alkyl Chains in the Layered Complex (C₄H₉NH₃)₂CuCl₄

Disorder-Enhanced Dimensionless Thermoelectric Figure of Merit zT of Non-stoichiometric Organic Conductor (TTT)₂I_3+δ (δ ≤ 0.1)