Interface Control in All MOD Coated Conductors: Influence on Critical Currents

Abstract

AbstractIn this work we will report our recent progress in the control of the interface quality between buffer layers and YBCO thin films grown by the trifluoroacetates route (TFA) and how it influences the critical current of the coated conductors. We have mainly focused on vacuum and metalorganic deposited (MOD) fluorite-like CeO2 buffer layers and on MOD perovskite SrTiO3 buffer layers. We will show that for vacuum CeO2 buffer layers, microcracks at the surface can be controlled by the means of thermal treatments. Coated conductors TFA-YBCO/CeO2sputt/YSZ/CeO2/Ni with Jc(77K)˜1MA/cm2 can be grown even in the presence of these microcracks. For MOD SrTiO3 we will show that growing the buffer layer at low temperature reduces surface roughness and multilayers with high critical currents can be achieved. An all-chemical coated conductor has been grown TFA-YBCO/SrTiO3MOD/BaZrO3MOD/NiO-SOE/Ni with promising in-plane texture, Δ φYBCO=6.6°. For MOD CeO2 buffer layers, thermal annealings in oxidizing atmospheres lead to atomically flat surfaces that avoid the typical polycrystalline surfaces observed in MOD CeO2 grown in Ar/H2. High Jc multilayers can be achieved and the first all chemical coated conductor in IBAD tapes TFA-YBCO/CeO2MOD/YSZIBAD/SS has been obtained with Jc(60K)=2.3MA/cm2.