J. Rafałowicz

Thermal conductivity and electrical resistivity of the high-Tc superconductor YBa2Cu3O9−Δ

Abstract Thermal conductivity and electrical resistivity of single-phase YBa 2 Cu 2 O 9−Δ compound were measured in the superconducting ( T c =89.5 K) and normal states, in the temperature range 5–320 K. The electronic component of the total thermal conductivity was estimated to be 20%. The electrical resistivity changed linearly in the normal state up to highest measured temperature.

Thermal conductivity of YBCO and thermal conductance at YBCO/ruby boundary Part 1: Joint experimental set-up for simultaneous measurements and experimental study in the temperature range 10–260 K

Abstract A joint experimental set-up has been constructed for simultaneous low temperature measurements of thermal conductivity, k , of two solid samples and thermal conductance, R b −1 , at a solid/solid boundary using the steady state method. The thermal measurements presented here were carried out in the temperature range 10–260 K. A discussion of the peculiarities of the thermal conductivity behaviour of YBCO superconducting samples during the cooling cycle has been presented. Initial thermal boundary conductance measurements at the high temperature superconductor/solid (YBCO/ruby) boundary have been performed.

The Influence of Residual Gas Pressure on the Thermal Conductivity of Microsphere Insulations

Experimental results of investigations of the heat exchange by residual gas in microsphere insulations are presented. The results of measurements of microsphere effective thermal conductivity versus residual gas (N2) pressure in the pressure range of 10−3−105 Pa are also given. A sample of self-pumping microsphere insulation was prepared and its thermal parameters were tested. In comparison to the standard microsphere insulation, the self-pumping insulation yielded lower thermal conductivity results over the entire pressure range. The stability of its thermal parameters as a result of considerable gas input into the insulation volume is discussed. Measurements of temperature and pressure distributions inside the microsphere layer were performed. Plots of temperature and pressure gradients inside the layer of the microsphere insulation are presented.

The influence of neutron irradiation on the thermal conductivity of aluminum in the range 5–50 K

Measurements of thermal conductivity of 6N to 3N pure aluminum in the temperature range 5–50 K subjected to fast neutron irradiation, with exposures of 1013 and 1016 n · cm−2, are reported. The thermal conductivity maximum was found to shift towards higher temperatures with an increase in the fast neutron irradiation exposure. At high temperatures, a departure from Wilsons theory was observed, which may be attributed to the existence of additional electron scattering mechanisms. An increase in both ideal and residual thermal resistivity components with an increase in the radiation exposure was noted.

Deviation from matthiessen's rule for thermal conductivity of quenched Zn-doped Cd crystals in the temperature range 5–20 K

Quantitative deviations from Matthiessens rule (DMR) for thermal conductivity of quenched, Zn-doped Cd single crystals have been calculated on the basis of thermal and electrical conductivity measurements of the metal. The observed nonlinearity of DMRmax versus β, where β is an electron-lattice defect interaction parameter, suggests that anisotropic effects of electron scattering are the most probable source of the DMR for Zn-doped Cd. We have also observed that DMRmax saturates itself, reaching a constant value for higher values of β.

A universal dependence for thermal conductivity of metals and dilute alloys

A universal curve relating the maximum of thermal conductivity and its respective temperature with the residual electrical resistivity has been proposed for metals and dilute alloys. Based on the equation of that curve, a comparative analysis of selected literature data of thermal conductivity of metals, which have residual electrical resistivity in the range 10−11<ρ0<10−5Ω. cm, have been performed. Using the data for 33 metals, confirmation of the Wiedemann-Franz law for the impurity componentβ/T of thermal conductivity was obtained, which means that βth/βel∼1, whereβth andβel are the parameters of the electron-lattice defect interaction obtained from measurements of thermal and electrical conductivity, respectively. Examples of the failure of the Wiedemann-Franz law are also presented, exhibiting the values ofβth/βel in the range 0.16 to 25. Measurements of thermal conductivity in the range 2 to 20 K and determination of the residual electrical resistivity for the samples of Cd doped with Zn and quenched were performed, resulting in valuesβth/βel∼1.

Thermal conductivity of YBCO and thermal conductance at YBCO/ruby boundary Part 2: Hysteresis behaviour between 40 and 230 K

Abstract The thermal conductivity, k , of YBCO superconducting oxides and the thermal conductance, R b −1 , at the YBCO/ruby boundary have been simultaneously measured during a heating cycle using a joint experimental set-up and a steady state method. The measurements were carried out in the temperature range 10–260 K. Thermal hysteresis of both the thermal conductivity and thermal boundary conductance have been observed within the temperature interval 40–230 K. Some speculations and substantiations using other methods of measurement are offered in order to explain the observed behaviour of k ( T ) and R b −1 ( T ).

Low-temperature anisotropy of thermal conductivity of tin single crystals doped with zinc

The thermal conductivity of tin single crystals with zinc admixtures has been measured in the temperature range 3.5–25 K for concentrations up to 0.1 wt%. The anisotropy of thermal conductivity for two orientations, [001] and [010], has been determined. It was found that the influence of zinc admixture on the thermal conductivity anisotropy is of a complex, temperature-dependent character.

Electrical resistivity and deviation from matthiessen's rule in polycrystalline lead-doped tin

The results of measurements of the electrical resistivity, π of lead-doped (weight concentrations: 0.001, 0.01, 0.1, and 1%) polycrystalline tin are presented. The experiments were performed using a comparative method with the aid of a tantalum thermomagnetic modulator applied as a null indicator. A nonlinear dependence of the residual resistivity on lead concentration was obtained. An anomalous character ofp(T) dependence was observed in the lowest-Pb concentration sample (0.001%). The deviation of the resistivity-temperature characteristics from Matthiessens rule (DMR) was determined. The characteristics of the DMR do not show “humps” in the temperature range from 3.7 to 28 K.

Thermal conductivity and electrical resistivity of pure polycrystalline cobalt in the temperature range 2.5–30 K

Thermal conductivity and electrical resistivity of 99.99% pure Co sample were measured in the temperature range 2.5–30 K. The annealing, procedure of the sample (either above or below Curie temperature), followed by cooling it down to room temperature at a slow cooling rate, caused an unexpected increase in its thermal resistivity and residual electrical resistivity, contrary to the results obtained for most pure metals. Co samples either not thermally treated or annealed consist only of a HI phase as proved by X-ray and electron diffraction analyses. The result, led to the conclusion that changes of grain structure and physical defects appearing in the Co at Curie temperature and at 690 K, when phase transitions take place, should be taken into account. The electron-magnon scattering, is significant in electrical conductivity but the electron-physical defect and impurity scattering plays a dominant role in thermal conductivity. The electron-physical defect and impurity scattering is elastic (validity of the Wiedemann Franz law)) as demonstrated by the value ofβthβel = 1.0, obtained in this work.