The Structural, Superconducting and Transport Properties of the Compounds Y3Ba5Cu8O18 and Y3Ba5Ca2Cu8O18

This work is related to the structural, superconducting, and transport properties of the compounds Y₃Ba₅Cu₈O₁₈ and Y₃Ba₅Ca₂Cu₈O₁₈ prepared by the sol-gel method. The influence of the doping of Ca atoms into the compound Y₃Ba₅Cu₈O₁₈ was studied by employing XRD, SEM, AFM, EDX, DTA, TGA, and the electrical resistivity (ρ), Hall coefficient (R _H), Hall mobility (μ _H), and magnetoresistance measurements. The XRD spectra showed that Y₃Ba₅Ca₂Cu₈O₁₈ almost has the same crystal structure as that of Y₃Ba₅Cu₈O₁₈, except with some impurity peaks. The resistivity measurements have pointed out that the compounds Y₃Ba₅Cu₈O₁₈ and Y₃Ba₅Ca₂Cu₈O₁₈ have their T _c-onset temperatures at approximately 92.7 and 86.6 K, respectively. The Hall coefficients R _H and Hall mobilities μ _H have been measured at the 10–300 K temperature interval in a magnetic field of 0.55 T. The signs of R _H and μ _H are found to be positive for both samples, which indicate that the conduction is p-type in our samples. As expected, the magnetoresistance results clearly demonstrate a considerable decrease of the offset temperatures with increasing magnetic field.