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 Y 3 Ba 5 Cu 8 O 18 and Y 3 Ba 5 Ca 2 Cu 8 O 18 prepared by the sol-gel method. The influence of the doping of Ca atoms into the compound Y 3 Ba 5 Cu 8 O 18 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 Y 3 Ba 5 Ca 2 Cu 8 O 18 almost has the same crystal structure as that of Y 3 Ba 5 Cu 8 O 18 , except with some impurity peaks. The resistivity measurements have pointed out that the compounds Y 3 Ba 5 Cu 8 O 18 and Y 3 Ba 5 Ca 2 Cu 8 O 18 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.