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

Abstract

We report on a highly improved pinning performance in the melt-textured (Nd0.33Eu0.33Gd0.33)Ba2Cu3Oy+35mol% Gd2BaCuO5 (70nm in size) composite doped by tiny amounts of nanometer-sized MoO3 or NbO3 particles. The doping led to a spontaneous formation of clouds with extremely small (⩽10nm) (Nd,Eu,Gd)2BaCuXO5 particles, X=Mo,Nb. With an optimum content of MoO3 and NbO3, the self-field supercurrent at 77K was twofold and threefold higher than before, respectively. At 65K the supercurrent reached 700kA∕cm2 with Mo and 925kA∕cm2 with Nb at both 0 and 4.5T, and the self-field current at 90K was 100A∕cm2 in the Nb-doped sample, which is a value high enough for a safe levitation.