A novel resistance measurement technique in the field of directional solidification

A brief review of existing diagnostic methods in directional solidification is first presented. We then discuss the potential of global and differenti al resistance measurements to determine the interface position and velocity in liquid metals and semiconductors. An electronic design allowing the mea surements to be carried out with maximum accuracy is proposed. This design is characterized both at low and high temperatures and it is shown that the peak to peak noise on the resistance signal can be kept of the order of 0. 1 mu Omega. In the tin based system used in our investigations, this amount s to an accuracy in terms of solid-liquid interface position in the microme ter range, which represents a significant improvement with respect to exist ing techniques. We found that such an accuracy allows us to characterize in detail the heat transfer phenomena within our directional solidification f urnace, and to identify the thermal lag of the device in the ;translation a nd stabilization stages. (C) 2001 American Institute of Physics.