Surface-oxidation studies of cube-textured, pure nickel to form NiO as a potential YBa2Cu3O7−x-coated conductor buffer layer

Abstract

The growth of nickel oxide (NiO) on {100}〈001〉 cube textured, rolling-assisted biaxially textured substrates (RABiTS) of pure nickel was studied. Single-phase (100) NiO formed only in a narrow temperature range at 1250 ± 5 °C. At lower or higher temperatures, other orientations, namely (111), (311), and (220), also formed. At 1250 °C, practically single phase (100) NiO was observed for short oxidation times t of 0.2–10 min (oxide thickness < 10 μm). For 10 < t < 120 min, small quantities of (111) NiO formed in addition to (100), but near-single-phase (100) NiO formed once again after oxidation for >150 min (thickness > 35 μm). The ratio of (100) to (111) textures with oxidation time is explained in terms of epitaxial constraints, growth rates, and oxygen absorption on the (100) and (111) grains. The optimum oxidation conditions are oxidation for approximately 0.5 min at 1250 °C in flowing oxygen, yielding (100) NiO, a few microns in thickness, and root-mean-square roughness of approximately 40 nm on the length-scale of the grain size.