Self-assembled, rare earth tantalate pyrochlore nanoparticles for superior flux pinning in YBa2Cu3O7-δ films

Addition of pyrochlore rare earth tantalate phases, RE3TaO7 (RTO, where RE = rare earth, Er, Gd and Yb) to YBa2Cu3O7-delta (YBCO) is shown to vastly improve pinning, without being detrimental to the superconducting transition temperature. The closely lattice matched to RTO phase provides a lower interfacial energy with YBCO than BaZrO3 (BZO) and produces very fine (similar to 5 nm) particles with high linearity in their self-assembly along c. Critical current densities of 0.86, 0.38 MA cm(-2) at 1 and 3 T (for fields) parallel to the c axis were recorded at 77 K in 0.5-1.0 mu m thick films and a transition temperature of 92 K was observed even in the highest level doped sample (8 mol%).