title: Microstructural characterization of GdBa2Cu3O7-δ superconductor films with BaHfO3 artificial pinning centers by scanning transmission electron microscopy.
abstract: Critical current (IC) of superconductor films under magnetic field is strongly influenced by dispersions and morphologies of artificial pinning centers (APCs) in general [1]. BaHfO3 (BHO) is acknowledged as the best candidates of APCs for REBCO films, which shows utmost thickness dependence and isotropic angular dependence of IC values for REBCO films [2]. Moreover, several researchers have focused on the nanostrains caused by the lattice mismatch at the interface between APCs and REBCO matrix, which are also the source for enhanced vortex pinning of the REBCO films [3]. In this study, we investigated to examine the nanostrain at the interface using spherical aberration (CS) corrected scanning transmission electron microscopy (STEM).BHO introduced GdBa2Cu3O7-δ (GdBCO) film was fabricated by pulsed laser deposition (PLD) method. TEM samples were prepared by focused ion beam (FIB; Quanta 3D 200i, FEI) method followed by Ar ion thinning (NanoMill, Fischione) method. Atomic scale imaging was performed by spherical aberration corrected STEM (JEM-ARM200F, JEOL), then microstructures of BHO/GdBCO interface was then examined by Fourier transformation (FFT).BHO nanorods and nanoparticles were found dispersed in the GdBCO matrix, where {100} and {110} facets were present at BHO/GdBCO interfaces, as shown in Fig. 1. In the case of PLD process, most favorable growth direction of BHO is [001] direction, so that the regular quadrangular prism shaped BHO with {100} facets would be grown along [001] direction of GdBCO matrix [4]. {110} facets of BHO were formed to maintain the minimum surface area at BHO/GdBCO to reduce the interfacial energy.jmicro;63/suppl_1/i27-a/DFU082F1F1DFU082F1Fig. 1.Plan view HAADF-STEM image and FFT image showing facets at BHO/GdBCO interfaces. This work was supported by the Ministry of Economy, Trade and Industry (METI) as "Development of Fundamental Technologies for HTS Coils" and the JSPS KAKENHI (26600046).
authors.affiliation: Department of Materials Science and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yamada
authors.affiliation: Department of Materials Science and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishiyama
authors.affiliation: Department of Materials Science and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kaneko
authors.affiliation: Department of Materials Science and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Department of Materials Science and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Teranishi
authors.affiliation: Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587, Japan.
authors.forename: Takeharu
authors.initials: T
authors.lastname: Kato
authors.affiliation: HTS Conductor Processing & Power Application Division, International Superconductivity Technology Center, 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Ibi
authors.affiliation: HTS Conductor Processing & Power Application Division, International Superconductivity Technology Center, 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan.
authors.forename: Masateru
authors.initials: M
authors.lastname: Yoshizumi
authors.affiliation: HTS Conductor Processing & Power Application Division, International Superconductivity Technology Center, 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan.
authors.forename: Teruo
authors.initials: T
authors.lastname: Izumi
authors.affiliation: HTS Conductor Processing & Power Application Division, International Superconductivity Technology Center, 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan.
authors.forename: Yuh
authors.initials: Y
authors.lastname: Shiohara