[en] Mo-Ru-Rh-Pd alloys as the simulated materials for metallic inclusions precipitated in irradiated nuclear fuels were prepared by high vacuum induction melting. The compositions of the alloys evaluated by energy dispersive X-ray spectroscopy (EDX) analysis are Mo₃₅Ru₃₁Rh₉Pd₂₅, Mo₂₀Ru₅₄Rh₁₅Pd₁₁, Mo₃₀Ru₄₃Rh₁₄Pd₁₃, and Mo₄₃Ru₃₄Rh₁₂Pd₁₁. The thermophysical properties of the alloys, such as the elastic moduli, Debye temperature, and thermal conductivity were evaluated. The relationships between the micro-Vickers hardness and Young's modulus for the alloys show metallic characteristics. The thermal conductivities of all the alloys almost linearly increase with increasing temperature, and above about 1000 K, they are 10-fold as large or larger than that of UO₂. The electronic contribution to the thermal conductivity was also evaluated from the Wiedemann-Franz-Lorenz relation by using the electrical resistivity. It is confirmed that the characteristics of the mechanical and thermal properties of the alloys differ from those of UO₂

[en] The series of layered rare earth copper oxides with RE₂CuO₄ type formula, where RE is neodymium, samarium, or gadolinium, has been prepared and various thermophysical properties, such as elastic moduli, Debye temperature, and thermal conductivity, have been evaluated. The relationships between several properties of RE₂CuO₄ have also been studied. It was found that RE₂CuO₄ have relatively high thermal conductivity at around room temperature, which decreases with increasing temperature. Gd₂CuO₄ has the highest thermal conductivity compared with those of Nd₂CuO₄ and Sm₂CuO₄ in the whole temperature range, and the value at 330 K of Gd₂CuO₄ is 30.0 W m^-1 K^-1

[en] The series of layered rare earth copper oxides with RE₂CuO₄ type formula, where RE is neodymium, samarium, or gadolinium, has been prepared and various thermoelectric properties, viz. the electrical resistivity, Seebeck coefficient, and thermal conductivity, have been evaluated. The electrical resistivities of RE₂CuO₄ show negative temperature dependence and are extremely higher than those of the state-of-the-art thermoelectric materials. The Seebeck coefficients are negative in the whole temperature range, indicating that the majority of charge carriers are electrons. It was found that RE₂CuO₄ type oxides have relatively high thermal conductivities, which are about one order of magnitude higher than those of the state-of-the-art thermoelectric materials. The maximum value of the dimensionless figure of merit ZT is 0.0056 at about 950 K for Sm₂CuO₄. In order to utilize RE₂CuO₄ type oxides in an actual thermoelectric module, it is necessary to optimize the electrical properties and to reduce the thermal conductivity

[en] The series of Chevrel phases, Mo₆Te_8-xS_x (x=0, 1, 2), was prepared and the thermoelectric properties such as the electrical resistivity, Seebeck coefficient, and thermal conductivity were measured. Sulfur substitution increases the electrical resistivity and decreases the absolute value of the Seebeck coefficient of Mo₆Te_8-xS_x. The Seebeck coefficients of all samples are positive in the whole temperature range, showing that the majority of charge carriers are holes. The thermal conductivities of Mo₆Te_8-xS_x are lower than those of Mo₃Te₄, which is caused by the enhancement of phonon scattering due to the substitution of sulfur for tellurium. The thermoelectric figure of merit, ZT is not enhanced by the substitution of sulfur, and the maximum value of ZT is 0.015 at about 1000 K for Mo₃Te₄

No abstract available

[en] The thermoelectric properties of Sr_0.9R_0.1TiO₃ (R=Y, La, Sm, Gd, Dy) have been measured from room temperature to 1073 K. The electrical conductivities and Seebeck coefficients are independent of the kind of rare earth elements in the temperature range, so the figure of merits are influenced by the difference in the thermal conductivities. The thermal conductivities decrease with doping according to the rare earth atomic mass and ionic radius. Sr_0.9Dy_0.1TiO₃ shows the highest figure of merit of the investigated samples, reaching 3.84x10^-4 K^-1 at 573 K

[en] Titanium-based half-Heusler compounds (Zr_xHf_1-x)_0.7Ti_0.3NiSn (x=0.3, 0.4, 0.5, 0.6, 0.7) were prepared. The electrical resistivity, Seebeck coefficient, and thermal conductivity of the compounds were measured from room temperature to about 1000 K. The electrical resistivities decrease with increasing temperature. The Seebeck coefficients are negative in the whole temperature range, showing that the majority of charge carriers are electrons. The thermal conductivities increase with increasing temperature. The values at room temperature are around 3.5 W m^-1 K^-1. The maximum value of the thermoelectric figure of merit ZT is 0.32 at around 800 K for (Zr_0.7Hf_0.3)_0.7Ti_0.3NiSn

[en] Zirconium oxidized above the α/β transformation temperature and quenched to room temperature, had a needle-like prior-β phase. As prior-β zirconium was known to influence the mechanical properties of the cladding tube during a loss-of-coolant accident (LOCA), the nanochemical properties of prior-β zirconium were studied by nanoindentation tests at room temperature. The nanohardness and the oxygen distribution of prior-β phase have wave undulations whose wavelengths are almost the same as the grain size in the prior-β phase. A grain in the prior-β phase has nanohardness distribution caused by the difference in oxygen concentration

[en] The Heusler type compounds Fe_3-xV_xSi were prepared by arc melting in the concentration range between x=0 and x=1. The samples were characterized by a powder X-ray diffraction method and EDXA. The thermoelectric properties such as the thermal diffusivity, electrical resistivity, and Seebeck coefficient were measured in the temperature range from 300 to 1073 K. The thermal conductivities of Fe_3-xV_xSi were evaluated from the heat capacity, experimental density, and thermal diffusivity measured by a laser flash method. A strong vanadium concentration dependence is shown in the thermoelectric power (TEP) of Fe_3-xV_xSi. The temperature and vanadium concentration dependences of the thermoelectric properties of Fe_3-xV_xSi were studied

[en] The thermal properties of SrZrO₃ were evaluated from room temperature to 1400 K. SrZrO₃ was prepared by the solid state reaction of SrCO₃ and ZrO₂ powders. X-ray diffraction measurements showed that the sample has a perovskite structure. The sample for the measurements of the thermal properties was prepared from a sintered body. The heat capacities of SrZrO₃ were measured using a differential scanning calorimeter (DSC) in a high purity argon atmosphere. The phase transitions of SrZrO₃ were confirmed at higher temperature. The linear thermal expansion of SrZrO₃ was measured using a dilatometer. The thermal expansion data exhibited an excess volume increment that was related to one of the phase transitions confirmed by DSC