Synthesis and characterization of YBCO superconducting thin films doped with BaHfO3 via the TFA-MOD technique for potential aerospace applications

Abstract

The study aims to improve the critical current density (J_c) and flux pinning of YBa₂Cu₃O_7-δ (YBCO) high-temperature superconducting films. The decline in J_c at high temperatures and magnetic fields is due to intrinsic crystalline anisotropy, thermal fluctuations, and lack of effective pinning centers. To tackle this, the study uses a novel approach by incorporating BaHfO₃ (BHO) nanostructures (dots, rods, or particles) as artificial pinning centers in YBCO films. The objective is to augment critical current density and enhance flux pinning properties using trifluoroacetates metal organic deposition method (TFA-MOD) on SrTiO₃ (STO) substrates, with a specific focus on applications in the aerospace industry. Characterization of YBCO solutions involves measuring contact angle, viscosity, and modulus. Thermal, structural, microstructural and superconducting properties of the films were scrutinized by Differential Thermal Analysis-Thermogravimetry (DTA-TG), Fourier Transform Infrared (FTIR), X-ray diffractometry (XRD), X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) and Atomic Force Microscopy (AFM), Surface Profilometer (SP) and Physical Property Measurement System (PPMS). Rheological tests show viscosity decreases with temperature before stabilizing. Undoped YBCO exhibits good wetting on STO substrates. Heat treatment involves organic solvent removal and TFA decomposition, with FTIR and XRD analyses confirming decomposition of acetate complexes and strong c-axis texture. XPS results indicate consistent chemical compositions, while surface morphologies are flat and crack-free, with denser structures in BHO-doped films. Doping improves superconductivity up to a certain concentration, after which it decreases. Average film thickness is around 240 nm. Undoped YBCO films exhibit poor superconducting properties due to secondary phases, while BHO doping influences superconductivity, with an increase in critical current density up to a certain concentration, beyond which superconductivity is lost.