LOW-TEMPERATURE THERMAL-CONDUCTIVITY MEASUREMENT APPARATUS - DESIGN ASSEMBLY, CALIBRATION AND MEASUREMENT ON (Y123, BI2223) SUPERCONDUCTORS

A cluster approach has been developed with the inclusion of the well k nown and traditionally employed transient plane source (TPS) technique for a comprehensive set of measurements of the thermal transport feat ures of high-T-c superconductors at low temperature. The present work shows the experimental arrangement containing a resistive element, 'th e TPS element', made of nickel material which serves the purpose of he at source and temperature sensor. From the practical point of view the main goal of the work is to design a simple cryogenic system and a sa mple holder configuration together for low-temperature measurements (8 4-293 K). The whole experimental arrangement is linked with the vacuum system containing a rotary pump for vacuum purposes. The apparatus is calibrated with a disc-shaped fused quartz sample for low-temperature measurements and carbon steel samples for room-temperature measuremen ts taken as reference standard materials. Large disc-shaped supercondu cting samples (Y123 and Bi2223) are studied for thermal properties wit h the same designed apparatus, The thermal conductivity values for the samples are 2.695 and 0.944 W m(-1) K-1 at the transition temperature respectively. A sharp increase below T-c in the thermal conductivity curve for both the samples is observed.