| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2006: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2005: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2004: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
In the first year of the project, I set up the density measurement system utilizing the high energy gamma ray attenuation method by renewing the gamma ray detector. With this system, I measured the density of the molten Ge-Te and Si-Te systems around the eutectic composition, 85 at.% Te. Using the density data, the molar volume and thermal expansion coefficient have been obtained as a function of temperature. In the meantime the sound velocity up to 1200℃ and specific heat up to 650℃ have been measured. Combining all those data, the thermodynamic response functions, i.e. the specific heat at constant pressure, isothermal compressibility, and thermal expansion coefficient, which characterize structural changes in the melt of Ge-Te and Si-Te alloys have been evaluated. Main results are summarized as bellow.
1) Ge-Te system
For this system, the Darken stability has been evaluate with the abovementioned thermodynamic functions using the new thermodynamic relations derived by the present inve
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stigator (J. Phys. Condens Matter 11 (1999) 593). From the results, I have shown for the first time that structural change in liquid Ge15Te85 proceeds without inducing concentration fluctuations. The specific heat data obtained in this research has been used as the cover illustration of the proceedings of TOFA 2004 in Vienna.
2) Si-Te system
Si belongs to the same column of the periodic table and the Si-Te phase diagram around the eutectic composition is very similar to the one for the Ge-Te system. However, structural change in this system proceeds in different way in which the concentration fluctuations induced by structural changes develops most substantially around the eutectic composition. The difference in concentration fluctuations may be consistently explained with the new thermodynamic relations. The results have been presented at the spring meeting of the Physical Society of Japan, 2007 and are in preparation for publishing.
3) Structural changes in elemental liquids : Trends in the periodic table.
Sound velocity has been measure to investigate whether or not structural changes occur in elemental liquid around the melting point. It has been confirmed that liquid As changes its structure very rapidly in the undercooled state. Clear trend has been found in the position in the periodic table of the element undergoing structural change in the liquid state. The paper has been published in the special issue of Int. J. Mat. Res dedicated to Prof. F. Sommer on the occasion of his 65th birthday. Less
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