改良型TFA-MOD法によるYBCO線材の臨界電流値向上に関する検討

Abstract

The metal organic deposition (MOD) method which uses solution materials including trifluoroacetates (TFA) as a solute, is one of the most promising methods to fabricate high-quality superconducting wires at low coast. In this study, a new combination of starting materials was developed using F-free salt of Cu and TFA salts of Y and Ba in order to shorten annealing time. Moreover, a new process temperature profile for this solution was developed as an advanced TFA-MOD process, in which a high heating rate was achieved. As a result, an overall transport Ic value of 210 A and a Jc value of 1.5 MA/cm2 at 77 K in a self-field similar to Ic and Jc values using TFA for all salts were obtained. In order to obtain higher Jc performance, the effect parameters such as partial pressure of the water vapor in the annealing process were investigated. Consequently, a YBCO film of 1.3 μm in thickness was fabricated on a CeO2/IBAD-Gd2Zr2O7 layer buffered Hastelloy substrate with Δφ =4°. Consequently, the Ic values increased as the water vapor pressure increased during the crystallization, and the overall transport Ic value of 340 A at 77 K in a self-field was obtained by annealing under a partial water vapor pressure of 6.3 vol%.