Effects Of Carbon And Oxide On The Superconductivity Of Doped MgB₂

Because of high critical temperature (Tc), low material cost and weak-link free behaviour. MgB2 has been regarded as a possible substitute for Nb-based conventional superconductors. MgB2 is believed to be a promising candidate for practical applications, especially for MRI magnets in the temperature range of 20-25 K.Unfortunately, Because of the lack of flux pinning centers and low upper critical field(Hc2), the applications of MgB2 are hampered. A fine and well-bonded particle structure of superconducting phase with introduced fine nano-size second-phase particles is pursued to order to improve the flux pinning properties of MgB2. The work in this thesis concentrates on the influence of chemical doping on the superconducting.In Chapter 1, An overview of the research on MgB2 superconductor and the development superconducting materials are briefly introduced. The progress of MgB2 superconductor was sresearched. The aims as well as the main contents of the present dissertation are also explained.In Chapter 2, Mainly from its superconducting mechanism, three basic physical properties and the impact of these factors are expounded and briefly introduces various MgB2 superconductors preparation methods and test instrument.In Chapter 3,we present the influence of the Copper oxide and Ferric oxide doping in MgB2 superconductor.In Chapter 4, we introduce the effects of a different quality percentage of citric acid doping on MgB2 bulks and we also introduce the effects of pretreated citric acid doping on MgB2 bulks.