Tungsten and molybdenum double perovskites as pinning centers in melt-textured Y123

Y123 + 30 mol% Y211 powders were doped with tungsten and platinum, and textured. Microstructure studies show the presence of profuse spherical deposits, 200-300 nm in diameter. These deposits were identified as (W0.5Pt0.5)YBa2O6, a double perovskite. The size of the W-rich deposits is independent of the W doping level. There is no substitution of W into the Y123 matrix. For Pt doping > 0.5 wt.%, trapped field is observed to increase monotonically up to 40% for W doping of up to 0.48 wt.%. We conservatively estimate that this corresponds to a 60% increase in J(c) at constant field. Thus (W0.5Pt0.5)YBa2O6 double perovskites deposits act as pinning centers. Similar studies of molybdenum doping indicate deposits 200-300 nm, of (Mo0.5Pt0.5)YBa2O6, also a double perovskite. The (W0.5Pt0.5)YBa2O6 and (Mo0.5Pt0.5)YBa2O6 deposits are remarkably similar to the (U0.6Pt0.4)YBa2O6 deposits found earlier in U-doped Y123. Therefore, W and Mo are suitable non-radioactive substitutes for U. (C) 2002 Elsevier Science B.V. All rights reserved.