Conductivity Fluctuation and Some Parameters of High temperature Superconductor Polycrystalline Y1Ba2Cu3O7−δ doped with Silver Nanoparticles

Abstract

In this study, we report the effect of Ag nanoparticles doping on the dimensional fluctuations of superconducting order parameters, crystal structure, and some parameters of Y 1 Ba 2 Cu 3 O 7−δ + × Ag (x = 0.0, 0.06, 0.1, 0.3, and 0.6 wt%) polycrystalline ceramics. By increasing the content of Ag in YBCO matrix, X-ray diffraction (XRD) with the Rietveld refinement technique revealed that the crystal lattice parameters changed and the orthorhombicity decreased slightly. Also, the increase of Ag wt% caused a decrease of superconducting transition temperatures (Tc) which are determined from the standard four-probe method and dropped abruptly. Aslamazov-Larkin (AL) model was used to analyze excess conductivity fluctuation. Lawerence-Doniach (LD) temperature named T LD which is responsible for the dimensional nature of fluctuation inside the grains is influenced by nano-silver combination in the compound. Crossover temperature from 2D to 3D (T LD) decreased in the mean-field region as a resultant dominance of 3D region by increasing of Ag in YBCO matrix. The decrease in zero-resistance critical temperature (T c zero), zero-temperature coherence length along the c-axis ξ c (0), and super layer length d values implies the degradation of inter-grain weak links, more disorder state of samples and unsettling of the mean free path for the charge carriers respectively with addition of silver nanoparticles. The calculations based on AL and LD model showed the highest anisotropy (γ = 1.34681) for the x = 0.6 sample. The size of the Ag ions, being larger compared to Cu ions, and the number of substitution sites affects the coupling between the CuO2 planes and that results in higher anisotropy. Critical magnetic fields B c1 (0), B c2 (0), and critical current density J c (0) were indirectly calculated from the Ginzburg-Landau (GL) number and GL equations. By increasing the doping level of silver nanoparticle, these parameters were found to be higher in Ag-added YBCO samples compared to the pure Y123, meaning better intrinsic flux pinning properties of doped Y123. The silver nanoparticle inclusion reduces the grain size and increases the strength and hardness of the parent compound.

Excess Conductivity Analysis of Polycrystalline FeSe Samples with the Addition of Ag

“…In this case as well, the upper critical field increased by a factor > 2 upon Ag addition, and the critical current improved by a factor > 3. The superconducting transition temperature, however, remained unchanged or even decreased upon Ag addition [39]. These observations demonstrate again that the Ag addition to FeSe does not just fill the pores and reduce the electric resistance, but also alters the electronic configuration.…”

“…The Josephson coupling, E J , slightly decreases upon Ag addition from about 0.64 to 0.54, which is distinctly different from materials like Bi-2212 and Bi-2223, where E J is found around 0.025 [37,38]. In Ag-added YBa 2 Cu 3 O y (YBCO), E J was found to be in the range of 0.30-0.35 [39], which is two times lower than the values obtained here. The observed reduction of the E J value upon Ag addition suggests the intensification of the density of charge carriers within the conducting planes.…”

“…We can directly compare this situation with the Ag (or Ag 2 O) addition to the YBa 2 Cu 3 O y compound, which was extensively studied in the literature (see, e.g., [45,46]). The fluctuation-induced conductivity of such samples was also analyzed in [26,39]. In this case as well, the upper critical field increased by a factor > 2 upon Ag addition, and the critical current improved by a factor > 3.…”