Record flux pinning in melt-textured NEG-123 doped by Mo and Nb nanoparticles

We report on a highly improved pinning performance in the melt-textured (Nd0.33 Eu0.33 Gd0.33) Ba2 Cu3 Oy +35 mol % Gd2 BaCu O5 (70 nm in size) composite doped by tiny amounts of nanometer-sized Mo O3 or Nb O3 particles. The doping led to a spontaneous formation of clouds with extremely small (≤10 nm) (Nd,Eu,Gd)2 BaCuX O5 particles, X=Mo,Nb. With an optimum content of Mo O3 and Nb O3, the self-field supercurrent at 77 K was twofold and threefold higher than before, respectively. At 65 K the supercurrent reached 700 kA cm2 with Mo and 925 kA cm2 with Nb at both 0 and 4.5 T, and the self-field current at 90 K was 100 A cm2 in the Nb-doped sample, which is a value high enough for a safe levitation.