Influence of Grain Size on the Superconductivity of La1.85Sr0.15CuO4

Abstract

We study the influence of varying grain size on superconductivity of bulk La1.85Sr0.15CuO4 superconductor. The samples are synthesized by a sol-gel method. The grain size is varied by sintering the samples at various temperatures between 700 °C to 1050 °C. The samples are characterized by X-Ray Diffraction (XRD), Rietveld refinement, Scanning Electron Microscopy (SEM), resistivity and magnetization measurements. The electrical resistivity measurements revealed considerable lowering of the superconducting transition temperature (\(T_{\mathrm{c}}^{R=0}\)) and broadening of the transition width (ΔTc) with decreasing grain size though the onset of transition temperature (\(T_{\mathrm{c}}^{\mathrm{onset}}\)) changes only marginally. The magnetic measurements carried out are consistent with each other and scale well with the grain size. Critical current density has been calculated from the magnetization hysteresis, assuming that supercurrents flow throughout the sample as a whole and within the individual grains as well. The observed results have been discussed on the basis of inter- and intra-granular boundary characteristics of high-temperature superconductors (HTSc). It is found that lowering of grain size deteriorates the superconducting properties in general.