Comparison of microstructures of pulsed laser deposited YBa2Cu3O7-δ thin films using solid-state sintered and modified melt-textured grown targets

YBa2Cu3O7-delta (YBCO) thin films were deposited by pulsed laser deposition (PLD) using differently prepared targets. The targets were fabricated using both solid-state sintering (SSS) and modified melt-textured growth (MTG) methods. The films deposited from MTG targets had better superconducting properties, such as T-c, Delta T and J(c), than the films deposited from SSS targets. In order to understand the enhanced superconducting properties, the film microstructures were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). As the laser energy density was increased, the films showed an increase of a-axis outgrowth. However, the observed a-axis outgrowth formation indicated that the deposition using MTG targets would result in a more homogeneous and stable film growth as compared to SSS targets. Also, TEM analysis implied that the film deposited from MTG targets had an enhanced grain connectivity that would reduce weak-link effects in the film. Thus, these microstructural differences of films deposited from MTG targets were considered to result in higher J(c) than the films deposited from SSS targets. (C) 1999 Elsevier Science B.V. All rights reserved.