Study Of Superconductivity Of [Mg(B_1-xC_x)₂]_0.97 Cu_0.03 And Doping Choice Of Rare-earth Iron Oxyarsenide

The development and theory of superconductivity were simply intruduced in the dissertation at first.The characteristics and research of MgB₂ and LaOFeAs were also introduced at the same time,Then,the relevant knowledge of average energy of valence orbit and electro-negativity were introduced . The dissertation mainly describes the following work in two areas:1 C, Cu- Doping effects on the structural change MgB₂. A series of samples of [Mg(B_1-xC_x)₂]_0.97Cu_0.03 (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25) and MgB₂ were synthesized by a solid state reaction method and analyzed carefully these samples . The XRD result indicates that the c-axis of the lattice remains unchanged with increasing C doping, while the a-axis shows a small decrease. The real carbon content x is estimated from the lattice parameter, and the solubility limit for C in MgB₂ presumed lies between 12.5% and 15%. The R-T result indicates when the C content remains unchanged, the superconducting transition temperature (T_c) of samples steadily decreases with increasing C doping.2 The correlation between the energy of valence orbit and the superconductivity of doping rare-earth iron oxyarsenides was researched in this paper. It was found that the average energy values of valence orbits parameter's about cations and anions concentrate in 11.407eV to 11.705eV and the difference of that concentrate in 8.446eV to 8.8698eV for doping rare-earth iron oxyarsenides superconductors. Moreover, we speculated that the best superconductive state of doping rare-earth iron oxyarsenides had not occurred on the basis of relationship between T_c and average energy of valence orbits, at present. It was helpful to understand the connection between the electrostatic actions of the electron on the lattice of valence orbits with superconductivity and research the superconductivity of doping rare-earth iron oxyarsenides.