Y - Superconductor Preparation Process And The Substitution Effect Study

Contrapose the problems exist in the traditional preparation process of high critical transition temperature yttrium family superconductors, we grope for the new preparation technics using the hydrochemical method, and analyzed its approximate process of reaction using the thermal-gravity analysis technology. The superconducting transition temperature crystal structure particle diameter surface topography and micro-region ingredient of YBCO superconductor obtained were tested by standard four probe method XRD analysis SEM and EDS means. On the basis of YBCO superconductor synthesized by hydrochemical method, we have tried this method to the precursor preparation for single domain blocks of yttrium family. This may provide a brand-new preparation technics for the preparation of precursor for high quality single domain superconductors; it is redound to the preparation efficiency of single domain superconductors.To comprehend the superconductivity influenced by magnetic and non magnetic ions in the Cu substitution sites in YBCO, we also prepared the series superconductors of YBCO, whose Cu sites were substituted by magnetic ion Mn or non-magnetic ion Zn. The series characteristics of series superconductors with Mn substitution were investigated by standard four probe method XRD analysis SEM and EDS means. The main conclusion we obtained in this paper were as follows:(1) The particle diameters of synthesized precursor for YBCO single phase superconductor and single domain superconducting blocks were all in several microns, and the final samples after sintering process have good superconducting performance. The XRD analysis results of the final samples show that there seldom appearance of miscellaneous phases. This is a convincing proof that this method is a feasible technics for preparing superconducting materials.The precursor for single crystal YBCO superconducting blocks was preliminary synthesized using the hydrochemical technics and tested simply. the results reveal that the particle diameters were all about several microns. If we can control the particle diameters in nano degree, its will be a brand-new technics for large-scale preparation of single domain superconducting blocks.The research results on the series YBCMO (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.40) samples show that Mn substitution has affect critical transition temperature T_c slightly with a lower substitution. The lattice structure of samples was seldom affected and still the Y123 phase structure. There is no superconducting transition hint in high substitution content samples under liquid nitrogen temperature. The results of SEM and EDS analysis show that Mn and YBCO combine together and form little grain which adhere to the big grain of YBCO. Since these little grains is independent to the grain of YBCO in small concentration, so they may not mainly affect the whole crystal structure, this may one of the reasons that small substitute content seldom affect the superconductors' T_c. With the increase of Mn substitution content, the crystal formed by combining Mn with YBCO enter into YBCO superconductors, even dispersed in the whole superconductors and thus can severely affect the structure of superconductors and superconductivity. We can consider little Mn substitution may show cluster effect in the superconductors, namely Mn combined with YBCO and formed rich Mn small areas!The change characteristics of the crystal lattice parameters illustrate that the substitution of Zn has affect the T_c greatly. The reason may be Zn substitute for the Cu sites of CuO2 plane, where is the place for the occurrence of superconductivity. So Zn can restrain the T_c strongly. After Zn substituted for Cu, since the valence of Zn is lower than that of Cu, so it need less coordinate oxygen ions, the oxygen content of samples should decrease with the increase of Zn. The TG results confirmed the decrease of the oxygen content in the samples substituted by Zn.The influence of the substitution of Nonmagnetic element Zn for Cu sites in YBCO is greater than that of magnetic element Mn, this is completely different from conventional superconductors. These also illuminate the unique function of CuO₂ plane...