I= PREPARATION AND THERMAL TRANSPORT PROPERTIES OF INSULATORS AND HIGH-TC SUPERCONDUCTORS
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Title of Thesis
PREPARATION AND THERMAL TRANSPORT PROPERTIES OF INSULATORS AND HIGH-TC SUPERCONDUCTORS

Author(s)
IZHAR-UL-HAQ
Institute/University/Department Details
Department of Physics/ Quaid-i-Azam University, Islamabad
Session
1993
Subject
Physics
Number of Pages
499
Keywords (Extracted from title, table of contents and abstract of thesis)
thermal transport properties, insulators, high-tc superconductors, transient plane source technique, transient hot strip, heat conduction

Abstract
The transient plane source technique (TPS) for measuring thermal conductivity, diffusivity has recently been developed. In this method a resistive pattern, cut out from a thin sheet of metal and covered on both sides with thin layer of an insulator material, is used both as heat source and as temperature sensor. The configurations used so far might be referred as "Hot Disc or Hot Square". The special attention in this work is given to the design of these elements when used for thermal transport studies of insulators as well as for electrical conducting materials. The TPS technique is an evolution from the transient hot strip (THS) technique and since both have complemented each other, therefore, the THS technique is briefly described. The theory of TPS technique is developed for materials with direction independent properties and are given in some detail. To check the validity of the theory of TPS technique, first experiment was performed on composite materials i.e. five marbles at room temperature. The measured values of the thermal conductivity and Thermal diffusivity and specific heat capacity per unit volume of these samples are in good agreement with the values of other marble samples reported earlier using the THS method. A comparison of these two techniques have been given in the light of experimental results.

Transient plane source technique has been employed to measure experimentally the thermal conductivity of three selected steel samples. The measured values of thermal conductivities have been critically analyzed taking in to. The measurements were made on fused quartz which have a well established thermal conductivity data at low temperature. The results of fused quartz showed no hysteresis either in cooling and heating. In fact, fused quartz data confirm that the TPS-sensors have a well defined temperature coefficient of resistivity (TCR) values down to liquid nitrogen temperatures and can be used to determine thermal transport properties, particularly the thermal conductivity values. The measurement on Ceramic Cecorite 130P is investigated in the temperature range 88 to 280k. The results showed that the thermal conductivity is influenced by the thermal history of the sample. This technique is also used to measure the thermal transport properties of High-Tc Superconducting materials [RBa2Cu307_0 (R=Y,Er)]. The results are quantitatively interpreted in terms of two models , the first model is the ordinary electron and phonon transport theory applied to high-Tc superconductors, and the second model is the BRT theory of the lattice heat conduction in high-Tc superconductors. Both models suggest that the electron-phonon coupling could vary from moderately weak to strong coupling depending on the characteristic parameters of considered material such as oxygen content,'. porosity, Tc value, ˆ†Tc etc., all of which are directly related to the purity of the investigated samples account factors such as composition and nature of alloying elements. An effort has been made to study the temperature dependence of thermal conductivity of these samples from room temperature to 300°C. Results of the present measurements have also been discussed in the light of the values of thermal conductivity on equivalent steel measured by other workers.

Download Full Thesis
1119.45 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
69.52 KB
2 1 Introduction 1
66.46 KB
  1.1 Phenomena Of Heat Conduction 1
3 2 Preparation And Characterization Of High- Tc Superconductors 9
109.1 KB
  2.1 Sample 9
  2.2 Characterization 11
4 3 Transient Plane Source (TPS) Technique For The Studies Of Insulators And Metals 22
201.64 KB
  3.1 Basic Equation For Heat Conduction 22
  3.2 Transient Hot Strip (THS) Method 23
  3.3 The Transient Plane Source Technique TPS) Experimental Design Criteria 28
  3.4 Electrical Insulation Of The Conducting Pattern 37
  3.5 Design Criteria For Measurements On Materials With Low thermal Conductivity 39
  3.6 Experimental Arrangement And Procedure 40
5 4 Results And Discussion 46
164.56 KB
  4.1 Experiment On Rock-Marbles To Validate The Theory Of TPS Technique 46
  4.2 Discussion On The Results Of The Rock-Marbles 46
  4.3 Experiments On Steel Samples 48
  4.4 Discussion On The Results Of The Steel Samples 49
  4.5 Experimental Set Up To Measure The Thermal Conductivity Of The Fused Quartz And Ceramic 130p At Low Temperature (88-280k ) 57
  4.6 Discussion On The Results Of Cecorite 130p And Fused Quartz 61
6 5 Thermal Conductivity And Electrical Resistively Of The Y And Er Substituted 123 Superconducting Compounds In The Vicinity Of The Transition Temperature 68
117.98 KB
  5.1 Experiment 69
  5.2 Resultsanddiscussion 70
7 6 Conclusions 83
150.91 KB
8 7 References
395.62 KB
  7.1 Lrelevantpublications 86