Reel-to-reel Texture Analysis of Hts Coated Conductors Using a Modified Gadds System

High temperature superconducting (HTS) materials need a high degree of texture over kilometerlong lengths in order to carry the maximum amount of supercurrent for electric power industry applications. One way to achieve the high degree of texture is with the coated conductor architecture. The coated conductor is comprised of the HTS layer epitaxially grown on a textured oxide buffer layer on a metal tape which gives flexibility and strength to the multilayer conductor. Traditionally a 360o phi scan is conducted on a small centimeter-wide sample to determine the (111) texture of the buffer layer. The pole figure full-width at half-maximum (FWHM) is calculated for the (111) peaks to quantify the texture of the buffer layer. This pole figure FWHM value is a critical quality control parameter, since the current-carrying capability of the HTS material increases as the FWHM decreases. The texture of the HTS coated conductors was characterized using a Bruker AXS General Area Detector Diffraction System (GADDS) which was modified to analyze meter-long lengths of conductor. The unique reel-toreel sample holder design, coupled with the parallel beam produced by the cross-coupled Göbel mirrors in the GADDS system, allows fast and accurate pole figure FWHM determination at selected points along meter-long samples. System modifications and texture results for samples up to 10 meters long are described. INTRODUCTION The high temperature superconductor YBa2Cu3Ox (YBCO) has great potential for use in electrical power generation and transmission applications [1,2]. For YBCO to be a cost-effective replacement for conventional materials, the critical current (Ic) carrying capability must be increased. Other researchers have shown that high angle grain boundaries in the superconductor reduce Ic [3,4]. At low misorientation angles, the current is relatively unaffected by the grain boundary. As the grain boundary misorientation angle increases, the current able to flow across the grain boundary decreases exponentially. To retain high Ic in polycrystalline superconductors, the grain boundary angles must remain small; therefore, a well-textured superconductor is necessary for high Ic. The “coated conductor” architecture schematically shown in Figure 1 makes it possible to produce long lengths of well-textured HTS. The superconductor gets its texture from the buffer layer, which also acts as a barrier to prevent diffusion from the substrate. The substrate is inexpensive metal chosen for strength and flexibility. The top layer of silver protects the superconductor during handling. To make long lengths of YBCO superconductor with only low Copyright©JCPDS International Centre for Diffraction Data 2003, Advances in X-ray Analysis, Volume 46. 163