AVS 51st International Symposium
    Advanced Surface Engineering Tuesday Sessions
       Session SE-TuP

Paper SE-TuP10
Characterizations of the Surfaces of Shocked-Bi-Pb-Sr-Ca-Cu-O Superconductor Particles for a Magnetic Sensor

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: H.K. Kezuka, Tokyo University of Technology, Japan
Authors: H.K. Kezuka, Tokyo University of Technology, Japan
K.Y. Yamagata, Kinki University, Japan
M.I. Itoh, Kinki University, Japan
T.S. Suzuki, Tokai University, Japan
M.K. Kikuchi, Tohoku Fukushi University, Japan
T.A. Atou, Tohoku University, Japan
M.K. Kawasaki, Tohoku University, Japan
K.F. Fukuoka, Tohoku University, Japan
Correspondent: Click to Email
Recently, there has been an increased need for a highly sensitive magnetic sensor. Bi-Pb-Sr-Ca-Cu-O(BPSCCO) oxide superconductors are very attractive material as a highly sensitive magnetic sensor in which magnetic sensitivity of the sensor is found to be about 27 %/(10 @super -4@ T) using BPSCCO powders pasted for constructing the magnetic sensor. Characteristics of BPSCCO superconductor depend sensitivity on the grain growth temperature. Researches for applications of high-T@sub c@. BPSCCO superconductor particles have been made to overcome the weak-link problem around the grain boundaries for higher J@sub c@. Shock compaction for BPSCCO superconductor particles have been investigated by shock compaction technique. After the shock compaction characterizations of as-shocked BPSCCO superconductor particles are investigated by X-ray diffraction(XRD)-analysis for the measurements of lattice parameters and SQUID-measurements for the susceptibility. The grain growth with growth steps of as-shocked BPSCCO superconductor particles are observed by AFM(Atomic Force Microscope) and SEM(Scanning Electron microscopy). The particle size distribution was measured by a laser diffraction size analyzer, which employed laser diffraction and scattering methods. In this measurement, use was made of an isopropyl alcohol for dispersing the BPSCCO particles. The average particles is found to be about 4.2 µm. The specimens were pressed into pellets with 10 mm in diameter and around 1 mm in thickness. These pellets were tightly encased in stainless containers. Shock compaction experiments were carried out under the shock pressure of around 2-5 GPa by using a propellant gun-system. From XRD-analysis, it is found that Bi-2223 phase is appeared clearly after the shock compaction process under 2-5 GPa with Bi-2212 phase. The Amplitude Mode image shows the surface details better than the unfiltered Height Mode images for BPSCCO particles. Tapping AFM image of the surface and edges for annealed BPSCCO particles at 850 °C for 96 hr after shock compaction. It is found from the section analysis that the vertical distance around edge area varies from 86 to 478 nm. BPSCCO superconductors, the Bi-2223 structures of as-shocked BPSCCO probably have shock-induced defects by the shock compaction. The ∆M (the difference of susceptibility at 5 K obtained from the temperature dependency of field cooling and zero field cooling at 20 Oe) which is proportional to J@sub c@, is measured by SQUID magnetometer. As a result, from the measurements of the susceptibility by SQUID magnetometer, it is found from the susceptibility measurements as a function of temperatures that ∆M clearly increases to 0.073 (emu/g) for as-shocked BPSCCO after annealed at 850°C for 48 hr,which seems to indicate the new pinning centers around the grain boundaries　caused probably by the new defects of vacancies. The shocked specimens was compacted in platelet disk with a high crystal density over 97 %. The as-shocked specimen showed an oriented crystal structure with large grains of 3-5µm in length partly for shocked specimen by 2-5GPa. The ∆M (0.073 emu/g) of shocked specimen after annealing at 850° C for 48 hr became higher than that of starting specimen. These increase of ∆M indicate the introduction of a new pinning center through the shock compaction and annealing processes. The Amplitude Mode image of AFM show large edge effects which reflect the amplitude changes. Also form the section analysis of AFM, the vertical distance of 86-478 nm is obtained around the edge area in grains for annealed BPSCCO after shock compaction.