Transmission electron microscopy studies of YBCO coated conductors prepared by pulsed-laser deposition and multiple-stage chemical vapor deposition processes

Takeharu Kato, Hirokazu Sasaki, Hiroyuki Iwai, Akira Ibi, Naoji Kashima, Toshiharu Niwa, Takemi Muroga, Seiki Miyata, Tomonori Watanabe, Yasuhiro Iijima, Kazuomi Kakimoto, Yasunori Sutoh, Yutaka Yamada, Shigeo Nagaya, Takashi Saitoh, Teruo Izumi, Yukichi Sasaki, Tsukasa Hirayama, Yuh Shiohara, Yuichi Ikuhara

    Research output: Contribution to journalConference articlepeer-review

    9 Citations (Scopus)

    Abstract

    Three types of YBCO films were deposited on metal tapes with biaxially textured CeO2/Gd2Zr2O7 multilayer. One YBCO film 4 μm in thickness was formed by pulsed-laser deposition (PLD) on the stationary substrate and another film 3 μm in thickness by PLD using a reel-to-reel substrate tape transferring system. Ic values of the films were 173 A and 293 A, respectively A further film 1 μm in thickness was fabricated by multiple-stage chemical vapor deposition (MSCVD). The I c value of the MSCVD-YBCO film was 100 A. The microstructures of these YBCO films were characterized using transmission electron microscopy (TEM). In the PLD-YBCO films, the films less than 1 μm thick were predominantly composed of c-axis oriented grains which were considered to grow spirally, however, irregular instances of a-axis oriented grains were also found. The a-axis oriented grains size increased with increasing thickness of the YBCO films. In the 4 μm-thick PLD-YBCO film with an Ic value of 173 A, a-axis oriented grains were considered to nucleate on the CeO 2. We found many Y2O3 and cupper oxides at the boundaries between a- and c-axes oriented grains and the orientation relationships between YBCO and Y2O3 were determined to be as follows: (0 0 1)YBCO//(0 0 1)Y2O3 and (1 0 0)YBCO//(1 1 0)Y2O3. We also found many gaps and pores between YBCO grains. Nucleation of a-axis oriented grains was completely suppressed on the CeO2 in the 3 μm-thick PLD-YBCO film with an Ic value of 293 A. In the MSCVD-YBCO film, the YBCO film mostly consisted of c-axis oriented grains, however a-axis oriented grains and polycrystal also formed in the film. As the MSCVD-YBCO film became thicker, the a-axis oriented grains grew large, as same as in the PLD-YBCO films. The growth rate of a-axis oriented grain along the substrate normal was much higher than that of c-axis oriented grains in comparison to the difference in the growth rate between a- and c-axes oriented grains in the PLD-YBCO. In these specimens, the grain growth of the a-axis oriented grains was considered to be one of the most significant causes of degradation of Jc values in the YBCO films.

    Original languageEnglish
    Pages (from-to)1033-1042
    Number of pages10
    JournalPhysica C: Superconductivity and its applications
    Volume426-431
    Issue numberII
    DOIs
    Publication statusPublished - 2005
    EventProceedings of the 17th Internatioanl Symposium on Superconductivity (ISS 2004) Advances in Superconductivity -
    Duration: 2004 Nov 232004 Nov 25

    Keywords

    • MOCVD-YBCO
    • PLD-YBCO
    • TEM
    • YO
    • a-Axis oriented grain

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Condensed Matter Physics
    • Energy Engineering and Power Technology
    • Electrical and Electronic Engineering

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