6,893 research outputs found
AC susceptibility study of superconducting YBa2Cu3O7:Agx bulk composites (x = 0.0-0.20): The role of intra and inter granular coupling
We report the effect of silver addition on superconducting performance of
bulk YBCO (YBa2Cu3O7) superconductor. All the studied samples are prepared by
conventional solid-state reaction method. Rietveld fitted X-ray diffraction
data confirmed the single phase formation for all the studied samples. Detailed
AC susceptibility measurements as a function of driven AC amplitude (1Oe-17Oe)
of these samples revealed the enhancement of grains coupling with increasing Ag
content in YBCO+Agx composite system. 10wt% Ag added YBCO superconductors
exhibited the optimum inter granular coupling. The Scanning Electron Microscopy
(SEM) observations indicate an increase in the grains connectivity in terms of
narrow grain boundaries for doped samples. The average grain size is found to
increase with Ag doping. It is concluded that limited addition of Ag in bulk
YBCO superconductor significantly improves the grains coupling and as result
optimum superconducting performance. YBCO+Ag composites could prove to be
potential candidates for bulk superconducting applications of the studied high
Tc system.Comment: 15 pages of text + Fig
Evolution of superconductivity in PrFe1-xCoxAsO with x = 0.0 to 1.0
We report the synthesis and physical property characterization of
PrFe1-xCoxAsO with x = 0.0 to 1.0. The studied samples are synthesized by solid
state reaction route via vacuum encapsulation method. The pristine compound
PrFeAsO does not show superconductivity, but rather exhibits a metallic step
like transition due to spin density wave ordering of Fe moments below 150 K,
followed by another upward step due to anomalous ordering of Pr moments at 12
K. Both the Fe-SDW and Pr-TN temperatures decrease monotonically with Co
substitution at Fe site. Superconductivity appears in a narrow range of x from
0.07 to 0.25 with maximum Tc at 11.12 K for x = 0.15. Samples, with x = 0.25
exhibit metallic behavior right from 300 K down to 2 K, without any Fe-SDW or
Pr-TN steps in resistivity. In fact, though Fe-SDW decreases monotonically, the
Pr-TN is disappeared even with x = 0.02. The magneto transport measurements
below 14 Tesla on superconducting polycrystalline Co doped PrFeAsO lead to
extrapolated values of the upper critical fields [Hc2(0)] of up to 60 Tesla.Comment: 15 pages Text+Fig
- …