110 K Bi(Pb)-Ca-Sr-Cuo Superconducting Fibers by Glass-To-Ceramic Process
- PDF / 1,078,123 Bytes
- 4 Pages / 417.6 x 639 pts Page_size
- 101 Downloads / 181 Views
110 K Bi(Pb)-Ca-Sr-Cu-O SUPERCONDUCTING FIBERS BY GLASS-TO-CERAMIC PROCESS Haixing Zheng, Yi Hu, Yun-Seung Choi, Patrick Lin and J.D.Mackenzie Department of Materials Science and Engineering, University of California-Los Angeles, Los Angeles, CA 90024 Bi(Pb)-Ca-Sr-Cu-O glass fibers have been successfully fabricated by the melt-spinning technique. The sequence for the formation of the superconducting phase was Bi 2 Sr 2CuOz, Bi 2 (Ca,Sr)3 Cu 2Oz and Bi 2 (Ca,Sr) 4 Cu 3Oz. The transformation from the Bi 2 (Ca,Sr) 3 Cu 2Oz phase to the Bi2(Ca,Sr) 4Cu 3Oz phase was sluggish due to the stability of Bi 2(Ca,Sr)3Cu 2Oz phase. The formation of the liquid phase helped to decompose the Bi 2(Ca,Sr)3Cu2O0 phase and precipitate the Bi 2 (Ca,Sr) 4 Cu 3Oz phase. The glass-ceramic fibers showed different superconducting transitions, depending upon the composition and the heat treatment. Bil.s4Pb0. 34Ca 2Sr 2Cu 4Oz glass ceramic fibers reached zero resistance at 108 K, and have a 2 critical current density of 230 A/cm at 77 K in zero magnetic field. I. INTRODUCTION It is well known that glasses can be fabricated into different shapes by various welldeveloped techniques. Two widely used techniques are preform-fiber drawing and melt-fiber drawing. Both are used to fabricate continuous optical fibers. The glass formation in the Bi-CaSr-Cu-O system provided the opportunity to apply glass technology to the fabrication of high temperature Bi-Ca-Sr-Cu-O superconductors. Different shapes of Bi-Ca-Sr-Cu-O glass ceramics have been made, such as wires, rings and thick films. However, poor viscosity behavior of Bi-Ca-Sr-Cu-O glasses makes fibers difficult to prepare. Continuous amorphous metallic fibers or ribbons which can not be made by the conventional glass technology are easily fabricated by the so-called melt-spinning technology [ I ]. In this work, we report that Bi(Pb)Ca-Sr-Cu-O glass fibers have been successfully fabricated by the melt-spinning technique, and then the fibers are converted into the superconducting ceramic fibers.
II. FIBER FABRICATION Appropriate amounts Bi20 3 (99.8%), CaCO 3 (99.9%), SrCO 3 (99.7%), CuO (99.9%) and Pb(N0 3)2 (99.9%) were weighed and mixed. The mixture was melted in a platinum crucible at
1 100oC for 15 minutes. The viscosity of the melt was about one poise. The melt was continuously poured onto twin rotating brass rollers, with subsequent solidification into the glass fibers which were 10 cm long. The compositions which had better glass forming ability [21 could easily be spun into fibers. The Bi(Pb)-Ca-Sr-Cu-O glass fibers prepared by this method (Fig. 1) were smooth with a diameter of 20 pm.
Fig. 1 Bil.g4Pbo.34Ca 2Sr 2Cu4Oy glass fibers (A) side surface; and (B) cross-section. Mat. Res. Soc. Symp. Proc. Vol. 169. t1990 Materials Research Society
298
•."6310C' CP
~3iCC
C~21
~•"•
h
•l2~
~r
•
S5100C
8.5 h
4 0
4340C
5 min. 10
20
30 20
40
20
25
30 20
35
40
Fig.2 X-ray diffraction patterns of Bii.4Pb0.34 Ca2Sr 2Cu4 Oy glass fibers heated (a) at different
temperature for 10 hou
Data Loading...
