No abstract

A cluster approach has been developed with the inclusion of the well known and traditionally employed transient plane source (TPS) technique for a comprehensive set of measurements of the thermal transport features of high-T c superconductors at low temperature. The present work shows the experimental arrangement containing a resistive element, 'the TPS element', made of nickel material which serves the purpose of heat 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 sample holder configuration together for low-temperature measurements (84-293 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 measurements taken as reference standard materials. Large disc-shaped superconducting samples (Y123 and Bi2223) are studied for thermal properties with 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.

Simultaneous measurements of thermal conductivity and thermal diffusivity of composite red‐sand bricks, glycerine and mercury have been made at room temperature by the recently developed transient plane source (TPS) technique. This paper describes, in brief, the theory and the experimental conditions for the simultaneous measurements of thermal conductivity and thermal diffusivity of insulators, fluids and metals. The source of heat is a hot disc made out of bifilar spirals. The disc also serves as a sensor of temperature increase in the sample. The measured values of the thermal conductivity and thermal diffusivity of these samples are in agreement with the values reported earlier using other methods. The advantage of the TPS technique is the simplicity of the equipment, simultaneous information on thermal conductivity and thermal diffusivity, and also the applicability of the technique to insulators, fluids and metals.

Thermal conductivity and thermal diffusivity of rock marbles have been measured between 290 and 335 K in dry air at atmospheric pressure using the TPS technique. X-ray diffraction has been carried out. Infrared spectroscopic studies identify various polyatomic anions of the type C032-, NO3'-, S042-, etc. The temperature coefficient of resistivity of the TPS sensor has also been determined over a wide temperature range. Thermal conductivities and thermal diffusivities do not change with change of heating currents at room temperature. Four of the five samples showed a slight increase in thermal conductivity with temperature but thermal conductivity of Sohabi White marble showed a decreasing trend with rise in temperature.

No abstract