Low-temperature Thermal Conductivity Research Articles

Magnetic phase transitions and magnetoelectric coupling of GdFeO3single crystals probed by low-temperature heat transport

The low-temperature thermal conductivity ($\ensuremath{\kappa}$) of GdFe${O}_{3}$ single crystals is found to be strongly dependent on magnetic field. The low-field $\ensuremath{\kappa}(H)$ curves show two ``dips'' for $H\ensuremath{\parallel}a$ and only one dip for $H\ensuremath{\parallel}c$, with the characteristic fields having good correspondence with the spin-flop and the spin-polarization transitions. A remarkable phenomenon is that the sub-Kelvin thermal conductivity shows hysteretic behaviors on the history of applying the magnetic field; that is, the $\ensuremath{\kappa}(H)$ isotherms measured with increasing field are larger than those with decreasing field. Intriguingly, the broad region of magnetic field ($~$0--3 T) showing the irreversibility of heat transport coincides with that presenting the ferroelectricity. It is discussed that the irreversible $\ensuremath{\kappa}(H)$ behaviors are due to the phonon scattering by ferroelectric domain walls. This result shows an experimental feature that points to the capability of controlling the ferroelectric domain structures by magnetic field in multiferroic materials.

Thermoelectric Properties of Ge-doped Cu3SbSe4

ABSTRACTTernary variations of the II-VI zincblende semiconductors have received little attention for thermoelectric applications. Here we present the first systematic doping study on Cu3SbSe4, a zincblende-like ternary semiconductor with a unit cell four times larger than the parent II-VI compounds. The large unit cell of Cu3SbSe4results in a low room temperature thermal conductivity (~3.0 W/m*K) and its large hole effective mass produces a Seebeck coefficient approaching 500 μV/K in the undoped compound. Our results show that Ge is an effective p-type dopant in Cu3SbSe4, and the power factor reaches nearly 16 μW/cm*K2at 630K when 3% Ge is added, rivaling that of state-of-the-art thermoelectric materials at this temperature.

Low-temperature thermal conductivity of the noncentrosymmetric superconductor LaRhSi3

We report on low-temperature thermal conductivity of the noncentrosymmetric superconductor LaRhSi3 (TC = 2.3K), which is a paramagnetic analog of the pressure-induced superconductor CeRhSi3. In the normal state (either in zero field above Tc, or in magnetic field above Hc2), the thermal conductivity k is mostly due to electrons, and shows a nearly T-linear dependence. In the superconducting state, k decreases exponentially below Tc, and crosses over to κ ∝ T2 behavior at T << Tc. The temperature dependence of thermal conductivity of LaRhSi3 is similar to that of a number of conventional s-wave superconductors. The field dependence of the residual linear term κ0/T as a function of magnetic field suggests that LaRhSi3 has no nodes in the superconducting gap.

Resistivity, thermopower, and thermal conductivity of nickel doped compounds Cr1−xNixSb2 at low temperatures

Substitutional compounds Cr1−xNixSb2 (0≤x≤0.1) were synthesized, and the effect of Ni substitution on transport and thermoelectric properties of Cr1−xNixSb2 were investigated at the temperatures from 7 to 310K. The results indicated that the magnitudes of the resistivity and thermopower of Cr1−xNixSb2 decreased greatly with increasing Ni content at low temperatures, owing to an increase in electron concentration caused by Ni substitution for Cr. Experiments also showed that the low-temperature lattice thermal conductivity of Cr1−xNixSb2 decreased substantially with increasing Ni content due to an enhancement of phonon scattering by the increased number of Ni atoms. As a result, the figure of merit, ZT, of lightly doped Cr0.99Ni0.01Sb2 was improved at T>∼230K. Specifically, the ZT of Cr0.99Ni0.01Sb2 at 310K was approximately ∼29% larger than that of CrSb2, indicating that thermoelectric properties of CrSb2 can be improved by an appropriate substitution of Ni for Cr.

Low temperature transport properties and heat capacity of single-crystalNa8Si46

The low temperature thermal conductivity, resistivity, and Seebeck coefficient of single-crystalNa8Si46 are investigated revealing the intrinsic low temperature transport properties ofthis material. Metallic conduction is observed, with a higher residual resistanceratio than any other known type I clathrate. Heat capacity together with thermalconductivity provide insight into the Na disorder inside the polyhedra formedby the Si framework. Single-crystal structural refinement and thermal propertyanalyses reveal anisotropic disorder for Na inside the tetrakaidecahedra due to areduction in the symmetry inside these polyhedra, unlike that for Na inside thedodecahedra.

Anomalous thermal conductivity in multiwalled carbon nanotubes with impurities and short-range order

Low-temperature thermal conductivity and thermopower of multiwalled carbon nanotubes considered within a bundle of nanotubes are calculated taking into account multiple scattering of electrons on the atoms of impurities (like single carbon atoms) and short-range order regions arising due to a some distribution of the impurities. The calculations are realized on a base of the temperature diagrammatic Feynman techniques and the results of our research are in a good quantitative and qualitative agreement with the corresponding experimental data for multiwalled carbon nanotubes with diameter less or equal 10 nm at T<50K.

The effect of Ti substitution for Cr on transport and thermoelectric properties of CrSb 2 at low temperatures

Substitutional compounds Cr 1− x Ti x Sb 2 (0 ≤ x ≤ 0.10) were synthesized, and the effect of Ti substitution on transport and thermoelectric properties of Cr 1− x Ti x Sb 2 were investigated from 7 to 310 K. The results indicated that the temperature dependence of electrical resistivity and thermopower ǀ Sǀ for CrSb 2 did not alter significantly after substitution. However, the magnitudes of the resistivity and thermopower of Cr 1− x Ti x Sb 2 decreased monotonically with increasing Ti content owing to an increase in electron concentration indirectly caused by Ti substitution for Cr. Experiments also showed that the low-temperature lattice thermal conductivity of Cr 1− x Ti x Sb 2 generally decreased with increasing Ti content, which could originate from an enhancement of phonon scattering by increased number of Ti atoms. As a result, the figures of merit, ZT, of lightly-doped Cr 1− x Ti x Sb 2 ( x = 0.03) samples was improved at T > ∼200 K. Specifically, at 310 K, the ZT value of Cr 0.97Ti 0.03Sb 2 was ∼11% larger than that of CrSb 2, indicating that thermoelectric properties of CrSb 2 can be improved by an appropriate substitution of Ti for Cr.

Effects of silicon addition on thermoelectric properties of bulk Zn 4Sb 3 at low-temperatures

The thermoelectric properties of Si-doped compounds (Zn 1− x Si x ) 4Sb 3 ( x = 0, 0.0025, 0.005, 0.01) have been studied. The results indicate that low-temperature ( T < 300 K) thermal conductivity of moderately doped (Zn 0.9975Si 0.0025) 4Sb 3 reduces remarkably as compared with that of Zn 4Sb 3 due to enhanced impurity (dopant) scattering of phonons. Electrical resistivity and Seebeck coefficient are found to increase and then decrease moderately with the increase in the Si content. In addition, first-principles calculations are performed on the occupation options of Si atoms in disordered β-Zn 4Sb 3. The results indicate that Si atoms occupy preferentially the Zn vacancies in normal sites. Subsequently, Si atoms will substitute for interstitial Zn atoms. The lightly doped compound (Zn 0.9975Si 0.0025) 4Sb 3 exhibits the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient. Its figure of merit, ZT, is about 1.3 times larger than that of pure Zn 4Sb 3 at 300 K.

Structure and thermal conductivity of Na 1−xGe 3+z

Structural analyses as well as low temperature thermal conductivity is reported for the binary phase Na 1− x Ge 3+ z . Specimens were characterized by thermal analysis, conventional and synchrotron powder X-ray diffraction, neutron powder diffraction, 23Na nuclear magnetic resonance spectroscopy, and electrical and thermal transport measurements. With structural characteristics qualitatively analogous to some aluminum-silicate zeolites, the crystal structure of this phase exhibits an unconventional covalently bonded tunnel-like Ge framework, accommodating Na in channels of two different sizes. Observed to be non-stochiometric, Na 1− x Ge 3+ z concurrently exhibits substantial structural disorder in the large channels and a low lattice thermal conductivity, of interest in the context of identifying novel low thermal conductivity intermetallics for thermoelectric applications.

Enhanced thermoelectric properties of iron doped compound (Zn 1 − xFe x) 4Sb 3

The thermoelectric properties of Fe-doped compounds (Zn 1 − x Fe x) 4Sb 3 ( x = 0, 0.0025, 0.005, 0.01) have been studied at the temperatures from 7 K to 305 K. The results indicate that low-temperature ( T < 300 K) thermal conductivity of the moderately doped (Zn 1 − x Fe x) 4Sb 3 ( x = 0.0025 and 0.005) reduces remarkably as compared with that of Zn 4Sb 3 due to enhanced impurity (dopant) scattering of phonons. Electrical resistivity and Seebeck coefficient are found to increase first and then decrease obviously with the increase in the Fe content. Moreover, the lightly doped compound (Zn 0.995Fe 0.005) 4Sb 3 exhibits the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient, whose figure of merit (at 300 K), ZT, is about 1.3 times larger than that of β-Zn 4Sb 3 obtained in the present study.

Effect of coexisting order of various form and wave vector on low-temperature thermal conductivity ind-wave superconductors

In light of recent experimental evidence of density wave order in the cuprates, we consider a phenomenological model of a $d$-wave superconductor with coexisting charge-, spin-, or pair-density wave order of various form and wave vector. We study the evolution of the nodal structure of the quasiparticle energy spectrum as a function of the amplitude of the coexisting order and perform diagrammatic linear-response calculations of the low-temperature (universal-limit) thermal conductivity. The work described herein expands upon our past studies, which focused on a particular unit-cell-doubling charge-density wave, generalizing our techniques to a wider class of coexisting order. We find that the question of whether the nodes of the $d$-wave superconductor survive amidst a reasonable level of coexisting order is sensitive to the form and wave vector of the order. However, in cases where the nodes do become gapped, we identify a signature of the approach to this nodal transition, in the low-temperature thermal conductivity, that appears to be quite general. The amplitude of this signature is found to be disorder dependent, which suggests a connection between the presence of coexisting order in the underdoped cuprates and recent observations of deviations from universal (disorder-independent) thermal conductivity in the underdoped regime.

Relation between Low-Temperature Thermal Conductivity and the Specific Heat of Cesium Borate Glasses

Low-temperature specific heat and thermal conductivity measurements have been performed on cesium borate glasses as a function of cesium oxide content. We have found experimental evidence of a concurrent growth of specific heat and thermal conductivity with increasing Cs(+) content. This finding shows the existence of an uncommon relationship between the peak in C(p)/T(3) and the plateau in thermal conductivity in glasses and represents the most intriguing result for these alkaline borate glasses. The role of local modes associated with heavy cations on the vibrational dynamics in oxide glasses has been considered. Furthermore, a possible correlation between low-temperature thermal properties and the structure on the nanometer length scale of these glasses is put forward.

The effects of iodine doping on the thermoelectric properties of [formula omitted] at low temperatures

The thermoelectric properties of iodine-doped compounds Zn 4(Sb 1− x I x ) 3 ( x = 0 , 0.005, 0.01, 0.015) have been studied at temperatures from 5 to 310 K. The results indicate that the low-temperature ( T < 300 K ) thermal conductivity λ of moderately doped Zn 4(Sb 0.995I 0.005) 3 reduced remarkably as compared with that of Zn 4Sb 3 due to the enhanced impurity (dopant) scattering of phonons. The electrical resistivity and Seebeck coefficient were found to increase monotonically with the increase in the iodine content, which would reflect the decrease in carrier concentration due to the substitution of I for Sb. Moreover, the lightly doped compound Zn 4(Sb 0.995I 0.005) 3 exhibited the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient. Its figure of merit, ZT, was about 1.2 times larger than that of β - Zn 4Sb 3 obtained in the present study at 300 K.

Effects of Se doping on thermoelectric properties of Zn 4Sb 3 at low-temperatures

The thermoelectric properties of Se-doped compounds Zn 4(Sb 1− x Se x ) 3 ( x = 0, 0.005, 0.01, 0.015) have been studied. The results indicate that low-temperature ( T < 300 K) thermal conductivity of moderately doped Zn 4(Sb 0.99Se 0.01) 3 reduce remarkably as compared with that of Zn 4Sb 3 due to enhanced impurity (dopant) scattering of phonons. Electrical resistivity and Seebeck coefficient are found to increase and then decrease moderately with the increase in the Se content. Moreover, the lightly doped compound Zn 4(Sb 0.99Se 0.01) 3 exhibits the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient. Its figure of merit, ZT, is about 1.3 times larger than that of pure Zn 4Sb 3 at 300 K.

Effects of Ag doping on thermoelectric properties of Zn 4Sb 3 at low temperatures

The thermoelectric properties of Ag-doped compounds (Zn 1− x Ag x ) 4Sb 3 ( x = 0, 0.0025, 0.005, 0.01) have been studied at the temperatures from 15 to 300 K. The results indicate that low-temperature ( T < 300 K) thermal conductivity of the moderately doped (Zn 1− x Ag x ) 4Sb 3 ( x = 0.0025 and 0.005) reduced remarkably as compared with that of Zn 4Sb 3 due to enhanced impurity (dopant) scattering of phonons. Electrical resistivity and Seebeck coefficient were found to increase first and then decrease obviously with the increase in the Ag content, which could be ascribed to the change of carrier concentration presumably due to different Zn positions occupied by Ag upon increasing doping content. Moreover, the lightly doped compound (Zn 0.995Ag 0.005) 4Sb 3 exhibited the best thermoelectric performance due to the improvement in both its electrical resistivity and thermal conductivity, whose figure of merit (at 300 K), ZT, is about 1.3 times larger than that of β-Zn 4Sb 3 obtained in the present study. Present results suggest that proper Ag doping in Zn 4Sb 3 is a promising way of improving its thermoelectric properties.

Low-temperature thermal conductivity ofBaFe2As2: A parent compound of iron arsenide superconductors

We report low-temperature thermal conductivity down to 40 mK of the antiferromagnet BaFe$_2$As$_{2}$, which is the parent compound of recently discovered iron-based superconductors. In the investigated temperature range below 4 K, the thermal conductivity $\kappa$ is well described by the expression $\kappa$ = $aT$ + $bT^{2.22}$. We attribute the ``$aT$''-term to an electronic contribution which is found to satisfy the Wiedemann-Franz law in the $T$ $\to$ 0 K limit, and the remaining thermal conductivity, $\sim$ $T^{2.22}$, is attributed to phonon conductivity. A small influence on thermal conductivity by magnetic fields up to 8 T is well accounted by the observed magnetoresistance. The result is consistent with a fully gapped magnon spectrum, inferred previously from inelastic neutron scattering measurements.

Low temperature specific heat and thermal conductivity of bulk metallic glass (Cu 50Zr 50) 94Al 6

The low temperature specific heat and thermal conductivity of (Cu 50Zr 50) 94Al 6 bulk metallic glass have been studied experimentally. A low temperature anomaly in the specific heat is observed in this alloy. It is also found that in addition to Debye oscillators, the localized vibration modes whose vibration density of state has a Gaussian distribution should be considered to explain the low temperature phonon specific heat anomaly. The phonon thermal conductivity dependence on temperature for the sample does not show apparent plateau characteristics as other glass materials do; however, the influence of the resonant scattering from the localized modes on the lattice thermal conductivity is prominent in the bulk metallic glass at low temperatures.

Reply to “Comment on ‘Low-temperature phonon thermal conductivity of single-crystallineNd2CuO4: Effects of sample size and surface roughness’ ”

In their comment \cite{Sun} on our study of phonon heat transport in Nd$_2$CuO$_4$ \cite{Li}, Sun and Ando estimate that the phonon mean free path at low temperature is roughly half the width of the single crystal used in our study, from which they argue that phonon scattering cannot be dominated by sample boundaries. Here we show that their use of specific heat data on Nd$_2$CuO$_4$, which contains a large magnetic contribution at low temperature that is difficult to reliably extract, leads to an underestimate of the mean free path by a factor two compared to an estimate based on the specific heat data of the non-magnetic isostructural analog Pr$_2$CuO$_4$. This removes the apparent contradiction raised by Sun and Ando.

Low-Temperature Heat Transport in the Low-Dimensional Quantum MagnetNiCl2−4SC(NH2)2

We report a study of the low-temperature thermal conductivity of NiCl2-4SC(NH2)_{2}, which is a spin-1 chain system exhibiting the magnon Bose-Einstein condensation (BEC) in a magnetic field. It is found that the low-T thermal conductivity along the spin-chain direction shows strong anomalies at the lower and upper critical fields of the magnon BEC state. In this state, magnons act mainly as phonon scatterers at relatively high temperature, but change their role to heat carriers upon temperature approaching zero. The result demonstrates a large thermal conductivity in the magnon BEC state and points to a direct analog between the magnon BEC and the conventional one.

Low-temperature thermal conductivity in a d-wave superconductor with coexisting charge order: Effect of self-consistent disorder and vertex corrections

Given the experimental evidence of charge order in the underdoped cuprate superconductors, we consider the effect of coexisting charge order on low-temperature thermal transport in a d-wave superconductor. Using a phenomenological Hamiltonian that describes a two-dimensional system in the presence of a Q = ( π , 0 ) charge density wave and d-wave superconducting order, and including the effects of weak impurity scattering, we compute the self-energy of the quasiparticles within the self-consistent Born approximation, and calculate the zero-temperature thermal conductivity using linear response formalism. We find that vertex corrections within the ladder approximation do not significantly modify the bare-bubble result that was previously calculated. However, self-consistent treatment of the disorder does modify the charge-order-dependence of the thermal conductivity tensor, in that the magnitude of charge order required for the system to become effectively gapped is renormalized, generally to a smaller value.