Enhancement in critical current density of Y1Ba2Cu3O7−δ thin films on hastelloy with TiN buffer layers

Abstract

We have prepared high quality superconducting Y1Ba2Cu3O7−δ (YBCO) thin films on hastelloy (C) with titanium nitride (TiN) buffer layers. The hastelloy (C) is a nickel based superalloy with excellent high-temperature properties and corrosion resistance. The superconducting and TiN buffer layers were deposited sequentially at 600 °C using pulsed excimer laser irradiation of the respective targets. TiN has been suitably chosen owing to matching of thermal expansion coefficient (∼8.0–9.0×10−6/K) with hastelloy (∼9.0×10−6/K) and YBCO (∼12–13×10−6/K). X-ray diffraction, four point ac electrical resistivity and scanning electron microscope studies were performed on these films for correlations between crystal structure, microstructure, and superconducting properties. Auger electron spectroscopy (AES) was used to determine the extent of interdiffusion in metal-TiN and TiN-Y1Ba2Cu3O7−δ interfaces. These films exhibited a characteristic metallic conductivity followed by an onset of superconductivity at 91 K with a zero resistance temperature (Tco) of 85 K. Critical current density (Jc) for these films (77 K and zero magnetic field) was determined to be ∼9.0×104 A/cm2 for thin films on metallic substrates.