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Order or disorder in subsystem of dipolar constituents of a solid often significantly influences its physical properties. The results of investigation of the effect of glassy state in subsystem of carbon monoxide molecules on thermal conductivity of CO crystal in its equilibrium vapor pressure are reported. The thermal conductivity of a high quality carbon monoxide crystal was specified over the temperature range 1.2–45 K. The results of these measurements were analyzed within the frame of relaxation time approximation. It was shown that at low temperatures phonon scattering by subsystem of disordered CO molecules is the most significant dissipative mechanism of heat transfer in the investigated crystal.

By applying the Klemens–Callaway expression for the thermal conductivity in the framework of the Debye's model of phonons we present an analysis of the thermal transport by phonons in ceramic composites Si3N4/BN of various fibre structure (including plaited fibre configurations denoted [0/45] and [0/90]) and biomorphic composites (or ecocomposites) SiC/Si based on beech matrices filled with Si of two different volume percentage (2% and 26%). We obtained a good agreement with the Debye–Klemens–Callaway theory of the thermal conductivity at low temperatures for the ceramic composites Si3N4/BN with the plaited fibre configurations. A good fitting of the Callaway expression for the thermal conductivity coefficient in the whole temperature range can be made to our experimental results for the biomorphic composites SiC/Si. The latter fitting allowed us to assess the magnitude of the mean free path of phonons scattered by the boundaries of grains. We also estimated that the contribution of the conduction electrons to the heat transfer at low temperatures is 5–7% of the effective thermal conductivity in case of SiC/Si.

Thermal conductivity, k , of Ge x As 40− x S 60 glasses has been measured between 4.5 and 300 K. A variation of k with the composition is found and dependences of its parameters on the mean coordination numbers are established. Analyses have been made within but also independently of the soft-potential model. Some correlations and scaling laws are proposed.

Results of measurements of thermal conductivity of bulk GaN crystals in the temperature interval 4.2 – 300 K are reported. Experiments were performed on two types of single GaN crystals grown under high-pressure: highly conducting n-type sample and on a highly resistive sample compensated by magnesium doping. For n-GaN crystals, the highest thermal conductivity kmax is equal to 1600 W/m K at Tmax ¼ 45 K; and k . 220 W/m K at 300 K. Our analysis indicates that for the best n-GaN crystal and for T $ Tmax; the contribution of Umklapp phonon scattering processes dominate whereas for other samples scattering of phonons by point mass defects represents the main contribution. The dependence of kðTÞ is used to reveal possible mechanisms of thermal resistance of GaN crystals at temperatures Tmax: Our thermal conductivity measurements yields Debye’s temperature uD < 400 K: q 2003 Elsevier Ltd. All rights reserved.

The niobium hydrogen system has been studied in the region of hysteresis of thermal conductivity in the β phase. The relaxation of non-equilibrium hydrogen distribution following the λ-β and ɣ-β phase transitions has been observed for the first time by thermal conductivity measurements. The relaxation times corresponding to various temperatures have been extracted from the time and temperature dependences of the thermal conductivity.

We studied thermal conductivity, κ, and electrical resistivity, ϱ, in niobium hydrides between 5 and 420 K, during both cooling and heating. The temperature dependences of κ and ϱ show hysteresis, revealed for the first time in the system Nb-H. The results of thermal conductivity measurements suggest occurrence of a hysteretic ordering change in the β phase between 215.8 and 280 K for NbH0.87 and between 208.4 and 350 K for NbH0.90. The beginning of hysteresis takes place at the structural phase transition at ∼200 K. At this transition a jump of thermal conductivity was found - for NbH0.87 (215.8 K) during heating and for NbH0.90 (208.4 K) during both cooling and heating. The jump of electrical resistivity was observed only for NbH0.90. The appearance of hysteresis of κ was found also in other ranges of temperature.

Thermal conductivity (λ) has been measured with high precision in YBaCuO superconductor in the temperature range 80–320 K. The main results are: 1) observed increase of λ below Tc was connected with heat conduction by convection; 2) hysteresis and creep effect were discovered in λ(T) course — both effect connected with spinodal decomposition below Tc; 3) it was found that the temperature range in which hysteresis appeared is tightly connected with the oxygen content in the sample; 4) an anomaly in λ(T) was observed near ambient temperature, what may be result of oxygen vacancy ordering. In a sample of pure sintered CuO no anomalies like those in YBaCuO were found.