Friday, 2C-08, 12:10-12:20

Development of High Rate Deposition Technique for PLD-GdBCO Coated Conductors

Noriko Chikumoto

Sergey Lee, Keiichi Tanabe

Superconductivity Research Laboratory, ISTEC, 1-10-13, Shinonome, Tokyo, 135-0062, Japan
chiku@istec.or.jp

Pulsed-laser deposition (PLD) technique has been shown to be one of the promising methods to fabricate long-length REBCO coated conductors (CC) with high quality. However, for the future commercialization of CC, we have to reduce production cost by speeding up the deposition process as well as by raising I_c values. Here we show our achievement of high-rate fabrication of high-I_c GdBCO tapes by developing a novel "inside-plume deposition" (IP-PLD) technique. The main idea of the IP-PLD technique is to increase the deposition rate simply by reducing substrate-to-target (ST) distance. We also employed very large laser energy density, >3J/cm², for further increasing the deposition rate. As a result, the production rate increased up to about 3 times higher compare to the conventional PLD method.

However, the IP-PLD technique requires appropriate adjustment of target compositions, since the enrichment of Ba and Gd composition occurs with decreasing the ST distance. According to the systematic study of the relationship between the chemical nonstoichiometry of the tape composition and J_c, we found that adjustment of tape composition to a slightly Ba-deficient composition very effectively suppresses formation of impurity phases, such as BaCuO₂, and thus improves J_c properties. By combining the Ba-poor composition, and addition of 5 mol % BaZrO₃ as pinning centers, we obtained very high I_c values at 77 K of 700-1000 A/cm(s.f.) and 135A/cm @ 3 Tesla (//c) for short samples with an about 5 µm thick GdBCO layer. We also show some recent results of reel-to-reel fabrication of long-length tapes using the IP-PLD technique.

This work is supported by the New Energy and Industrial Technology Development Organization (NEDO).

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