Dependence of Microstructure and J c of YBCO Films on CeO2 Cap Layers Deposited by Multi-plume PLD

Abstract

In order to achieve high-performance YBa2Cu3O7−x (YBCO)coated conductors (CCs) fabricated in industrial scale, it is necessary to enhance the transport properties and production speed of the CCs for use in various application forms. The transport performance of CCs depends upon the inner structure of the conductors, which make it important to analyze the microstructure and transport properties. The thickness of the buffer layer is a factor in improving speed. In this work, we deposited YBCO films on CeO2 cap layers with different thicknesses ranging from 21 to 563 nm by multi-plume pulsed laser deposition (PLD) and investigated the dependence of the microstructure and superconducting properties of YBCO film on the thickness of CeO2 films. The crystalline structure and surface morphology of YBCO films are systematically characterized by means of XRD, AFM, SEM and TEM. The critical current of YBCO film was measured by the conventional four-probe method at 77 K, in self-field. The results showed that the microstructure and superconducting performance of YBCO film were strongly dependent on the thickness of CeO2 films. At the optimal CeO2 layer thickness of 221 nm, the YBCO film exhibited a sharp in-plane and out-of-plane texture of full width at half maximum (FWHM) values of 1.5° and 2.4°, respectively, and smooth morphology of root mean square (RMS) value as low as 4.0 nm. The sharply biaxially textured YBCO films with the critical current density as high as 4.7 × 106 A/cm2 (77 K, in self-field) were obtained on CeO2/MgO/Y2O3/Al2O3/C276 architecture.