Relations between microstructure and superconducting properties of Ce+Sn doped YBCO

Pellets of cerium plus tin doped YBa2Cu3O7–δ (Y123) were textured using the top seeding melt texturing growth method. Amounts of SnO2 varying from 0.25 to 1.00 wt.% were added to the 0.5 wt.% CeO2 doped compound. The critical transition temperature, which is 90.5 K for cerium alone doping, recovers gradually the pure Y123 value of 92 K with tin addition. For the lowest tin amount studied, the bean critical current density is enhanced compared to the cerium alone doping, reaching more than 90 kA/cm2 in self field and 50 kA/cm2 under 1 T at 77 K. SEM studies have revealed the existence of sub micron size particles containing Y, Ba, Cu, Ce, Sn, and O. Their number increases with tin addition. TEM observations coupled with EDX analyses have shown that their composition largely varies from one particle to another and include impurities such as Sr or Zr. Twin density was also calculated and related to the observed properties of the doped materials.