Rapid Formation of 200 m-long YBCO Coated Conductor by Multi-Stage CVD

Abstract

Toward the industrialization of YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-x</sub> (YBCO) coated conductors for practical applications, metal-organic chemical vapor deposition (MOCVD) has been investigated. We applied multi-stage MOCVD to achieve high-speed production of coated conductor because the increase of the number of depositing stages placed in a line could enlarge deposition area. Using 12-stage CVD, we succeeded in deposition of highly biaxially oriented YBCO layer at tape transfer speed of 50 m/h on the CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> capped ion-beam-assisted-deposition (IBAD) - Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> (GZO) buffered Hastelloy tape, and achieved high critical current density ( J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) exceeding 2 MA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in a short sample. And it was found that lowering substrate temperature according to YBCO layer growth was effective to increase I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> . Using this method, high critical current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) of 174 A was achieved by 1 mum thick YBCO layer which passed through 12-stage CVD, and 227 A by 1 mum thick YBCO layer deposited by 6-stage one. Based on these results, three 200 m-class YBCO layers were deposited by multiple depositions at tape speed of 50 m/h each, using the 12-stage CVD system. A 203 m-long YBCO layer was successfully deposited with end-to-end I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> of 92.8 A, so that the multiplication of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> and length reached 18.8 kA ldr m. These results indicate that a multi-stage CVD technique is useful for a rapid fabrication of long YBCO coated conductor.