Thermal conductivities and structures of Fukushima weathered biotite

Hayakawa, Kosetsu; Muraguchi, Masakazu*; Oda, Masato*; Iino, Chiaki*; Ishii, Hiroyuki*; Honda, Mitsunori   

We have found that there are regions of high Seebeck coefficient in crystalline minerals based on Fukushima weathered biotite, to utilize this for thermoelectric devices, we have to investigate its basic properties such as the relation between thermal conductivities and atomic structures. In this report, we present the results of our analysis of the relationship between the thermal conductivity and structure of weathered biotite, which is essential for determining the thermoelectric performance index of the material. Thermal conductivity was measured for weathered biotite pellets prepared under various sample preparation conditions using the steady-state method. Sample preparation conditions were compared by varying the pressure during the molding process and the heating rate during the sintering process. In order to measure thermal conductivity at high temperatures, we evaluated the methods to reduce and compensate for leakage heat flow and contact thermal resistance. In order to elucidate the composition and structure of the samples, structural analysis was performed by X-ray fluorescence analysis and X-ray diffraction. Consequently, the changes in the crystal structure due to sintering were revealed to have an influence on the thermal conductivity. To determine the structure in more detail, we will discuss the results of local structure analysis by X-ray absorption fine structure (XAFS) using synchrotron radiation.