Effect of the oxygen distribution and inhomogeneity on the superconducting properties of YBa₂Cu₃O_7−δ+xmol% Y₂Ba₄CuMoO_ysuperconductors

Abstract

A series of polycrystalline YBa 2 Cu 3 O 7−δ (YBCO) + x mol% Y 2 Ba 4 CuMoO y (Y-24Mo1) (x = 0.00, 0.05, 0.10, 0.20, 0.30, 0.50, 2.00 and 3.00) superconductors have been synthesized in air via a standard solid-state reaction technique. The effects of Y-24Mo1 addition on the microstructure, elemental distribution and the superconducting transition temperature were systematically investigated. When Y-24Mo1 was added to the YBCO, the predominantly single-phase with orthorhombic structure was maintained even at the highest concentration. SEM, EDS and EELS analyses show the presence of inhomogeneities, the change of homogeneity and the variation of oxygen distribution in the superconducting matrix. The Y-24Mo1 addition modifies the normal-state resistivity of samples from metallic to semiconducting, and is accompanied by a two-step transition. Moreover, low Y-24Mo1 concentration leads to a relatively sharp superconducting transition and a broad transition takes place for Y-24Mo1 addition greater than 0.30 mol%. These results can be interpreted by the change of oxygen distribution and by the variation of defects, twins, and oxygen deficiency.

Enhanced performance of GdBCO bulk superconductors by doping a new kind of YGdBa4CuNbO y nanoparticles

“…However, the effective flux pinning force can be achieved only when the size of the particles is near the coherent length (ξab ≈ 2-4 nm below 77 K for REBCO bulk superconductors) [25][26][27]. To attain greater flux pinning performance, the RE 2 Ba 4 CuMO y (RE-2411) has been introduced in REBCO bulk superconductors as effective flux pinning centers [28][29][30][31][32][33]. Moreover, it has been partially demonstrated that the Y 2 Ba 4 CuNbO y (YNb2411) particles do not ripen during melt processing [34,35].…”

High-Efficient Method for Introducing Nanometer Y2Ba 4 CuNbO x Flux Pinning Centers in Single-Domain YBa2Cu3O7−δ Bulk Superconductors by TSIG Process

“…Recently, Weinstein et al [9] and Hari Babu et al [10,11] found that RE 2 Ba 4 CuMO y (REM2411, M = U, Mo, Zr, Bi, Nb, W, ...) particles could form nanoscale inclusions in the superconducting phase matrix both during and post-melt processing and result in obvious enhancement of the J c of YBCO bulks. Therefore doping REM2411 in YBCO bulks became an important method to improve superconducting properties, such asJ c [11][12][13]. It is found that the flux pinning centers are mainly introduced by direct addition of REM2411 powders in precursor pellets [12][13][14].…”

“…Therefore doping REM2411 in YBCO bulks became an important method to improve superconducting properties, such asJ c [11][12][13]. It is found that the flux pinning centers are mainly introduced by direct addition of REM2411 powders in precursor pellets [12][13][14]. But fabrication of REM2411 powders usually need several times sintered at high temperature, this is not economical and time costing.…”