Influence of coating solution composition on REBa_2Cu _3O_y(RE=Gd and Sm,Eu,Gd) films fabricated by fluorine-free metalorganic deposition

摘要

GdBa_2Cu_3O_y (GdBCO) and Sm _(0.33)Eu_(0.33)Gd_(0.33)Ba_2Cu _3O_y (SEG) films were prepared by metalorganic deposition (MOD) using two fluorine-free solutions: A metal 2-ethylhexanate (2-EH) and a complex solution (CS) consisting of metal 2-EH and metal-naphthenate. We investigated the effects of these new fluorine-free solutions, and their potential use in the fabrication of several REBCO (RE: rare earth) materials. The crystal growth, surface morphology, and superconducting properties of films prepared on single-crystal LaAlO_3 substrates at low oxygen partial pressure strongly depended upon the coating solution used. Films prepared using 2-EH exhibited improved thermal stability of the superconducting phase during heat treatment. On the other hand, films prepared by CS had a flat superconducting matrix, with a roughness of several tens of nm and large precipitates 23 μm in diameter. In addition, the CS films had a higher critical temperature (91.2 K) than the 2-EH film. The zero-field critical current density at 77.3 K was 0.19 MA/cm~2 for 2-EH films, and 0.61 MA/cm~2 for CS films.