الفهرس 
Sample preparationOnly 14 pages are availabe for public view
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Abstract
The new HT,-ceramic superconductors are very important for their useful applications in magnets, power transmission, computer interconnections, Josephson devices and other instrumentations. The success of these applications depends on many interlocking factors, including critical T, critical c.d., critical fields, allowable processing temperatures, mechanical properties and chemical stability for the intended superconductors. Thus, Sr-bearing Hg-based 1212-ceramic superconductor is a class of solid state compounds which generally have a highly oxygen-deficient Hg-layer. An attempt to synthesis HgSr2CaCu20, has been unsuccessful. However, hgh-valence cations and rare-earth additives at the Hg- and Ca-sites have been employed to stabilize many series of 12 12-type superconductors and to improve their properties. Foreign high-valence cations together with rare-earth elements can stabilize the superconducting tetragonal Hg-1212 phase and produce changes in the superconducting properties by increasing the critical temperature (T,) and enhancing densification of the compact as well as controlling their grain growth. Some minor high-valence cations and rare-earth additions are often quite effective as sintering aids or microstructure regulators accelerating grain growth or may promote oxidation or reduction of their grain boundaries. The aim of the present thesis was, therefore, to follow up the effects of dopant cations at both Hg- and Ca-sites and their concentrations on the stability, physico-nuclear and superconducting properties of Sr-bearing Hg-based and Ga-based 12 12-ceramic superconductors.