New Carbonide, Silicide And Boride Superconducting Material Research

This thesis has made a brief introduction in various types of superconducting materials which are found recently. After summarizing the new superconductor exploration direction, ways and means, we primarily research on the carbonide, silicide and boride superconductor. Intermetallic compound C_xGeNi₃, Ti-Cr co-doped V_3-2xTi_xCr_xSi system, Nd_1-xY_xB₆ and Zr_1-xY_xB₁₂ system, and other superconducting materials containing carbon and boron are investigated.1. By solid state reaction, single phase C_xGeNi₃ compounds are successfully prepared and their physical properties are investigated. The limit of solid solubility of carbon in the C_xGeNi₃ phase is within the range from x=0.15 to x=0.2. The intermeticallic compound C_xGeNi₃ system is isostructural with that of MgCNi₃ superconductor. They are not superconducting above 5K and have a good metallic resistance behavior. A paramagnetic into weak ferromagnetic transition takes place at temperature near 280K and the transation temperature is decreasing with the carbon concentrations increasing.2. We fabricated V_3-2xTi_xCr_xSi samples with x up to 0.2 and the samples were characterized by the resistivity and magnetization method. The T_c drop in the Ti and Cr co-doped V₃Si is much slower than that in the solo-element Ti or Cr doped V₃Si with the same total dopant concentrations. The critical current density of V_2.8Ti_0.1Cr_0.1Si is significantly enhanced to more than 6 times of that for pure V₃Si at 10K in magnetic fields up to 4T. The effects of the isoelectronic co-doping in V₃Si samples, i.e. the slow drop of T_c and the large increase of J_c, have potential applications in other practical A15 superconductors such as Nb₃Sn and Nb₃Al. Further research on these practical applied superconducting materials are well under way in our laboratory.3. We primarily research on the binary boride which is attributed to cubic crystal system or laminated structure. Single phase Nd_1-xY_xB₆ compounds are successfully prepared and their physical properties are investigated. The intermeticallic compound Nd_1-xY_xB₆ system is isostructural with that of NdB₆. They are not superconducting above 2K and a paramagnetic into antiferromagnetic transition takes place at temperature near 10K.The Neel temperature T_N is decreasing with the dopant concentrations increasing. Further research on the Zr_1-xY_xB₁₂ system is well under way in our laboratory.