Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Effect of Po2 and Ag on the Phase Formation of the Pb-2223 Superconductor



Winnie K. Wong-Ng, Lawrence P. Cook, W Greenwood


The chemical reactions and the compositional characteristics of liquids which lead to the phase formation of the Pb-2223 ((Bi,Pb):Sr:Ca:Cu:O) superconductor have been studied for a precursor composition of Bi1.8Pbo.4Sr2Ca2.2Cu3Ox. The combined techniques of quenching, powder X-ray diffraction, differential thermal analysis (DTA), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) were used for this study. Samples were annealed under pure air (CO2- and moisture-scrubbed) and under a mixture of 7.5 volume % O2/ 92.5 volume % Ar. Under pure air, the precursor composition was within the five-phase subsolidus volume: 2212-CuO-(ca,Sr)2CuO3-(Ca,Sr)2PbO4-(Sr,Ca)14Cu24O41, whereas under 7.5 volume % O2 the five-phase subsolidus volume prior to melting was: 2212-CuO-3221-(Ca,Sr)2CuO3 -(Ca,Sr)2PbO4. In both cases, the formation of a metastable liquid was found to assist in the formation of the 2223 phase from the precursor solids. Under pure air, the reaction which produced metastable liquid was: CuO + 2212 + (Sr,Ca)14Cu24O41 + (Ca,Sr)2PbO4 > (Ca,Sr)2CuO3 + L. Under 7.5 volume % O2, the reaction was: CuO + 2212 + 3221 + (Ca,Sr)2PbO4 > (Ca,Sr)2CuO3 + L. Long-term annealing of precursor materials above the temperature of metastable melting resulted in a stable equilibrium assemblage containing 2223. The temperature of melting of this assemblage was consistently higher than that of the precursor materials. Depending on the temperature of the long-term annealing, both metastable and stable melts assisted in the formation of the 2223 phase. The presence of Ag in both the pure air and the 7.5 volume % O 2 experiments lowered the temperature of the melting events. Ag partially dissolved in the liquid, and its presence altered the subsolidus equilibria when the sample was annealed under 7.5 volume % O 2. These results are discussed with respect to their processing implications.
Journal of Materials Research


Ag-addition, melting, phase formation, superconductor


Wong-Ng, W. , Cook, L. and Greenwood, W. (1998), Effect of P<sub>o2</sub> and Ag on the Phase Formation of the Pb-2223 Superconductor, Journal of Materials Research (Accessed May 28, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created June 25, 1998, Updated February 19, 2017