Preferred orientation of Y-Ba-Cu-O superconducting films on polycrystalline alumina by a melt method without crucible

Abstract

The effects were studied of surface buffer layers, a sputtered gold or platinum film and/or a screen-printed Y,BaCuO, (211) layer, on the microstructure, preferred orientation and superconducting transition of YBa,Cu,O,-, (123) films, grown by a melt method without crucible on polycrystalline alumina substrates. The degree of (ON) preferred orientation (DPO) reached 89% as Pt buffer alone was used, but this was without a superconducting transition. A combined 211 layer on a sputtered metal layer resulted in films with T,-,,,, of above 55 K, smoother film surfaces and DPO of 44%. The growth of preferred orientation is attributed to an inhomogeneous (ON) nucleation effect during solidification. Reduced surface cracks and better connection among crystallites of the films grown on a combined buffer layer are responsible for the measurable superconducting transition.