COMPUTER-CONTROLLED THERMOELECTRIC-POWER MEASUREMENT FOR BULK HIGH-TC SUPERCONDUCTORS

We have established a quick and easy, modified dc method to measure thermoelectric power for bulk high transition-temperature (T(c)) superconductors. The temperature range investigated is from 300 to 50 K. The apparatus was developed on the basis of our already-existing commercial APD (APD CRYOGENICS INC, Allentown, Pennsylvania) superconductor characterization cryostat with a limited amount of extra instrumentation. The thermoelectric power is measured continuously within the temperature range by the control of a computer, a real time Seebeck coefficient S(T) versus temperature curve is plotted on the computer screen during the measurement, and the data can be saved to a disk. The entire processing period for each sample takes less than 2 h. This apparatus was calibrated with pure lead. By measuring on high T(c) superconductors which are well known in thermoelectric power, the system has been shown to have high accuracy and reliability.