Premium
Effect of Hot‐Pressing on the Bi─Pb─Sr─Ca─Cu─O System
Author(s) -
Song KangHo,
Sorrell Charles C.,
Dou ShiXue,
Liu HuaKun
Publication year - 1991
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1991.tb06802.x
Subject(s) - hot pressing , materials science , annealing (glass) , sintering , analytical chemistry (journal) , superconductivity , pressing , grain size , phase (matter) , relative density , calcination , critical current , mineralogy , metallurgy , composite material , chemistry , condensed matter physics , chromatography , physics , organic chemistry , biochemistry , catalysis
Uniaxial hot‐pressing has been used to improve the relative density and preferred gain orientation of the nearly pure (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O 10‐y (2223) phase in the Bi‐Pb‐Sr‐Ca‐Cu‐O system. Samples were prepared by freeze‐drying, calcining, and hot‐pressing the powders at 650° to 840°C at 50 and 200 MPa for 2 h. The hot‐pressed samples showed a high degree of grain alignment and increased density up to 99% of theoretical. At 200 MPa, the 2223 phase was partially destroyed during hot‐pressing, probably because of the weak bonding between the Bi─O 2 layers. However, the 2223 phase and superconductivity were recovered with subsequent annealing. The critical current density ( J c ) was improved 10‐fold over that of sintered samples through this technique, with the highest J c being 2100 A°Cm −2 at 77.3 K and zero field. The hot‐pressed samples also showed significant improvements in the J c as a function of applied magnetic field. The J c of a hot‐pressed and postannealed sample at 0.2 T and 77.3 K was 2 orders of magnitude greater than that of a sintered sample.