Preparation of Bi Superconducting Grains Including Seed Crystals by Shock Compaction
- PDF / 188,394 Bytes
- 5 Pages / 432 x 648 pts Page_size
- 48 Downloads / 168 Views
Preparation of Bi Superconducting Grains Including Seed Crystals by Shock Compaction
Hiroshi Kezuka1 , Kazuhiro Endo2 , Takaki Kameya1 , Mineo Itoh3 , Hitoshi Matsumoto4 , Hiroaki Kishimura4 , Tamio Endo5 and Shunichi Arisawa6 1 Tokyo University of Technology, 1404-1 Katakura-machi, Hachioji, Tokyo 192-0983, Japan. 2 Kanazawa Institute of Technology, 7-1 Ohgigaoka, Nonoichi, Ishikawa 921-8501, Japan 3 Interdisciplinary Graduate School of Kinki University, 3-4-1 Kowakae, Higashiosaka, Osaka 577-8502, Japan 4 National Defense Academy of Japan, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan 5 Mie University, 1577 Kurimamachiya-cho, Tsu, Mie 514-8507, Japan 6 National Institute for Material Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
ABSTRACT We have fabricated Bi2212 and Bi2223 bulk samples by shock compaction technique. Seed crystals were added to the starting materials in order to promote crystallization. The grain size of the prepared sample was increased by the addition of seed crystals to the starting material.
INTRODUCTION It is of great importance to synthesize high quality bulk high T c superconductors for electric applications such as current leads, fault current limiter and sensors etc. We have reported that the grain size and T c can be improved by using the shock compaction method [1–3] employing a propellant gun-system and post annealing in an electronic furnace. The specimen was maintained superconducting state at 77.4 K under a current density of approximately 40 A/cm2 without an external magnetic field. The superconductivity was however broken when the field was higher than 40×10−4 T. That is, electrical resistance occurred in the specimens when they were exposed to 40×10−4 T under a constant J of 40 A/cm2 . The fabricated samples thus can be used as magnetic sensors by this transition. The objective of this study is to promote grain sizes of Bi based superconductors of 2223-phase and 2212-phase crystals fabricated by shock compaction technology and to establish optimal experimental conditions.
EXPERIMENT 5%, 10% and 15% of crystal nuclei were added to the starting material (Bi1.85 -Pb0.35 -Sr1.90 Ca2.05 -Cu3.05 -O x ) to promote crystal grain growth. Superconducting Bi-Pb-Sr-Ca-Cu-O (BPSCCO) specimens (1)-(6). In order to enlarge the crystal grain size, 10%, 5% and 15% of seed crystals were mixed with the starting material. The crystallization is carried out by the shock compaction technique at a high pressure of about 10 GPa, melting the surface of the particles, and then solidifying by using the effect of the particles putting pressure on each other’s surfaces. Afterwards,
123
annealing process was carried out for 48 hours at 840 ◦ C to create a distribution of the crystallization. Figure 1 shows a diagrammatic illustration of the device used for the shock compaction. The size and the shape of the crystal grain were observed by SEM, and crystal structures were analyzed by X-ray diffraction.
Figure 1. The shock compaction system
DISCUSSION In the case of 5% seed content, an a
Data Loading...
