Conductivity fluctuation and superconducting parameters of the YBa2Cu3−x(PO4)xO7-δ material

Synthesis of the YBa2Cu3−x(PO4)xO7-δ superconducting material by the standard solid-state reaction is reported. DC resistivity measurements reveal the improvement of the critical temperature (TC) when substitution of phosphate in the Cu sites is performed. A bulk TC=97 K was determined by the criterion of the maximum in the temperature derivative of electrical resistivity. Structure characterization by means the X-ray diffraction technique shows the crystalline appropriated distribution of PO4 into the CuO2 superconducting planes. In order to examine the effect of phosphates on the pairing mechanism close to TC, conductivity fluctuation analysis was performed by the method of logarithmic temperature derivative of the conductivity excess. We found the occurrence of Gaussian-like fluctuations. The correlations of the critical exponents with the dimensionality of the fluctuation system for each Gaussian regime were performed by using the Aslamazov-Larkin theory. The Ginzburg number for this superconducting material is predicted and the critical magnetic fields, critical current density and the jump in the specific heat at the critical temperature are theoretically determined.