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Metal Organic Deposition of REBa2Cu3O7-y Films from Metal Trifluoroacetate Precursors Tetsuji Honjo, Hiroshi Fuji, Daxiang Huang, Yuichi Nakamura, Teruo Izumi, Yuh Shiohara Superconductivity Research Laboratory, ISTEC, Shinonome 1-10-13, Koto-ku, Tokyo 135-0062, JAPAN ABSTRACT Metal organic deposition (MOD) process using metal trifluoroacetate (TFA) precursors was applied to the Nd1+XBa2-XCu3Oy (Nd123) and the Tc dependence on experimental conditions such as the oxygen partial pressure (PO2) and the substrate temperature (Ts) for annealing was investigated. Thin films grown on SrTiO3 substrates at Ts = 800 °C under PO2 = 300 ppm showed a Tc value of 89 K. However, from the results of TEM-EDS measurements, the substitution values of x in the Nd123 films increased from the substrate toward the surface in the film. These experimental results could be thermodynamically explained by the following model. The basic idea of the model is that the Ba potential in the precursor decreases by coarsening of BaF2 particles during the annealing for the Nd123 crystal growth. This model predicts that the small substitution value can be obtained with a higher growth rate of the Nd123 phase under low PO2.

INTRODUCTION Metal organic deposition (MOD) is expected as one of the attractive processes for tape conductor applications because of a non-vacuum process and a rapid deposition rate. Especially, the MOD process of YBa2Cu3O7-y (Y123) using metal trifluoroacetate (TFA) precursors has been of great interest for development of coated conductors since high quality Y123 films with high critical current density (Jc) can be fabricated by this process [1]. Actually, this process has been applied for coated conductors and realized the high Jc Y123 films on metal substrate [2, 3]. From a material point of view, the RE-Ba-Cu-O system (RE=Nd or Sm) is one of the most promising materials, since NdBa2Cu3O7-y and SmBa2Cu3O7-y with higher Tc values than that of Y123 have been obtained [4]. Furthermore, REBa2Cu3O7-y is known to form the RE1+xBa2-xCu3Oy (RE123) type solid solution in which RE3+ ions substitute for Ba2+ ions and its crystals with small x can exhibit the peak effect in the magnetization hysterisis loop at 77 K [5]. However, the Tc value decreases as the substitution value (x) increases [6]. Therefore, the control of x value is a very important factor to obtain high Tc values for the RE123 crystals. In this study, the TFA process was applied to the Nd123 and the Tc dependence on experimental conditions such as the oxygen partial pressure (PO2) and the substrate temperature (Ts) for annealing was investigated.

EXPERIMENTAL A TFA precursor solution for fabrication of Nd123 was prepared by dissolving the TFA salts of Nd, Ba and Cu with 1:2:3 cation ratio into sufficient methyl alcohol to give a II4.2.1

solution with total metal ions concentration of 1.5 M. The coating solution so prepared was spin-coated onto the single crystal substrate of SrTiO3(100) with a size of 10 mm square. The sample was fired in the following two steps. In the f