[en] An assessment of thermodynamic information for Zr-O-H system was executed using the Calculation of Phase Diagrams (CALPHAD) technique. Phase diagram of Zr-O-H ternary system was calculated using our experimental data and those from literature for Zr-O-H system. Effect of oxygen on phase modification of Zr-H system was also discussed using the assessed thermodynamic information

[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 creep properties of zirconium hydrogen solid solution were studied to elucidate the influence of hydrogen on the characteristics of zirconium solid solution. The power law creep exponent was found not to change with increasing hydrogen content. The creep rate of a zirconium alloy hydrogen solid solution was discussed in terms of the present result on creep properties and our previous result on the elastic properties

[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] 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] 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

[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 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] Thermodynamic modelling was demonstrated for ZrO₂-ThO₂ system based on the data for the ZrO₂-UO₂ and ZrO₂-CeO₂ systems in the literature. The calculated phase diagram for the ZrO₂-ThO₂ system showed a good agreement with the experimental data in the literature. Using the data obtained, together with the data for ZrO₂-UO₂, ZrO₂-PuO₂ and ZrO₂-CeO₂ systems, the stability of the fluorite structure phases in the ZrO₂-MO₂ (M=Th, U, Pu, Ce) systems was also studied with respect to the partial molar quantities. The effect of the ZrO₂ on the enthalpy in the MO₂ rich region increased as the cation size of the matrices decreased. The solubility limits of the ZrO₂ in the fluorite structure phase in this region also increased as the cation size of the matrix decreased. The effect of MO₂ on the partial molar Gibbs energy in the ZrO₂ rich region increased as the cation size of the MO₂ increased. It implies that the dissolution of the larger cation stabilises the fluorite structure of the ZrO₂ more

[en] Thermodynamic modelling was performed to assess the phase relation in the O-Pu-Zr system. Firstly a preliminary thermodynamic modelling was attempted for the O-Pu system with thermodynamic data and phase diagram information available in the literature. The assessed data reproduced the general feature of the system with respect to phase diagram, oxygen potential and heat capacity. Secondly a possible set of phase diagrams for the O-Pu-Zr system was calculated using obtained data for the O-Pu system together with those for the O-Zr and Pu-Zr sub-systems available in the literature. Thermodynamic parameters assessed for the PuO₂-ZrO₂ pseudobinary system gave a phase diagram with a feature very similar to those for CeO₂-ZrO₂ and UO₂-ZrO₂ systems. O-Pu-Zr ternary phase diagrams were also calculated in the temperature range of 773-1773 K, and phase relation in the system was discussed