The lateral material distribution of laser-deposited YBa2Cu307_ ,~ films and the density of droplets coming from the target were studied by varying the laser pulse energy, the laser spot size and the target-to-substrate distance. Silicon wafers at ambient temperature were used as substrates to guarantee a large sticking coefficient of the particles. The deposition rate is found to depend linearly on the laser energy density E and quadratically on the spot size S at the target, whereas the droplet density is slightly dependent on E and increases linearly with l/S, yielding a threshold energy of 0.9 J cm -2. With a laser spot size of 7.15 mm 2 and a laser energy density of 1.2 J cm-2, we were able to reduce the number of droplets to one to two per 500/zm 2 for a high quality high T~ film with a typical thickness of 100 nm.
YBa2Cu3O7−x bulk samples made by citrate synthesis and pyrolysis are characterized and compared with samples made by solid-state reaction. Calcination at 830 °C followed by sintering at 950 °C of samples made of pyrolyzed powder gives pellets with quite good superconducting properties. They are very dense (6.06 g/cm3) and have a specific heat jump of 4 J/mol K at 91 K. X-ray diffraction shows a strong c-axis orientation, scanning electron microscope, and energy dispersive x-ray spectroscopy show a homogeneous structure and composition for these kinds of samples.
High quality Y-Ba-Cu-O thin films were successfully prepared by using ion beam sputtering. Zero resistance was reached at 90 K. The critical current density at 77 K was 4–5×104 A/cm2. The surface morphology of the films was observed by scanning electron microscopy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.