In-situ measurement of thermodiffusion in liquid alloys

Kurzfassung

Thermodiffusion, also called Soret effect, describes the formation of a concentration gradient induced by a temperature gradient. This cross-coupling effect of heat and mass transfer influences the homogeneity of doped semiconductors and grown crystals as well as the microstructure formation in alloys. The calculation of thermodiffusion by molecular dynamic simulation can be very sensitive to the specific potential. To validate models for thermodiffusion in liquid alloys, reliable measurements are needed. Using x-ray radiography in combination with a high temperature furnace, thermodiffusion in liquid Al-Ag has been measured. This technique enables in-situ observation which excludes disturbances by solidification and reveals possible error sources as e.g. free surfaces. Thanks to the time-resolved information from x-ray radiography, the interdiffusion coefficient could simultaneously be measured and is in good agreement with previous interdiffusion measurements in this concentration range. The measured Soret coefficient is compared with the values predicted by the current theoretical models, which are found to be off by at least a factor of two.