Preparation of textured YBCO films using all-iodide precursors

We developed an all-iodide precursor approach to grow epitaxial YBa₂Cu₃O_7-y (YBCO) films on single crystal substrates. The respective metal iodides were used as the starting materials. Initially, yttrium and barium iodides were dissolved in 2-methoxyethanol, whereas copper iodide was dissolved in ammonium iodide/dimethylformamide solution. The solutions were mixed together and concentrated to give a 2.5-M total cation precursor solution. The precursor solutions were spin coated on SrTiO₃ (100) substrates and heat-treated at 800-830 °C in 300 ppm oxygen atmospheres. X-ray diffraction (XRD) results from the theta-2theta (θ-2θ) scan, omega (ω) and phi (φ) scans for the films revealed a (100) cubic texture. The full-width-at-half-maximum (FWHM) values for YBCO (105) and YBCO (005) were 1.3° (in-plane epitaxy, Δφ) and 0.42° (out-of-plane epitaxy, Δω), respectively. The YBCO films had a T_c of 90.3 K. The measured transport J_c, critical current density was 1.3×10⁵ A/cm² at 77 K and self-field.