Development of REBCO Tapes on Nonmetallic Flexible Substrates for RF Applications

Abstract

REBa 2 Cu 3 O 7-x (RE = rare earth) films on a flexible, low-cost, and low thermal expansion substrate offer a unique advantage for RF applications such as surface receiver coils for a magnetic resonance imaging (MRI). In this work, polycrystalline, inexpensive, lightweight, and flexible yttria-stabilized zirconia (YSZ) with low thermal conductivity and low RF loss was used as a substrate for epitaxial REBCO films. The YSZ substrate surface was planarized to a surface roughness R q of about 1 nm. Ion-beam assisted deposition was used to obtain highly oriented single-crystalline-like buffer templates. Homo-epitaxial MgO and epitaxial LaMnO 3 (LMO) thin films were deposited via reel-to-reel magnetron sputtering. The out-of-plane and in-plane texture values of LMO were optimized to 2.6° and 6.8°FWHM, respectively. Epitaxial GdYBCO was grown by an advanced metal organic chemical vapor deposition on the buffered YSZ substrates with an average in-plane texture 4.3°FWHM. A magnetization critical current density (J c ) at 77 K, 0 T measured by a physical property measurement system is 0.84 MA/cm 2 . A quality factor measured at 77 K, 12.9 GHz is comparable to that of high-quality epitaxial REBCO films single-crystal rigid substrates. The epitaxial REBCO films on the YSZ polycrystalline substrates after further optimization can be used to construct RF coils for the MRI and other RF, microwave applications.