ISSN:
1572-9605
Keywords:
superconductor
;
(Tl1-x Bi x )1.33Sr1.33Ca1.33Cu2O6.67+δ
;
crystal structure
;
1212 phase
;
ceramic
Source:
Springer Online Journal Archives 1860-2000
Topics:
Electrical Engineering, Measurement and Control Technology
,
Physics
Notes:
Abstract Joining YBa2Cu3O6.5+δ (123 phase) and Bi4Sr4Ca2Cu4O16+δ (4424 phase) as structurally characterized high-T c , superconductors, the thallium-containing superconductor (Tl.75Bi.25)1.33Sr1.33Ca1.33Cu2O6.667+δ with the ideal stoichiometry (Tl,Bi)1Sr2Ca1Cu2O6.5+δ (1212 phase) is reported here. As prepared from the component oxides, 1212 has an initial deviation from resistance linearity at 120 K, a superconducting onset temperature of 92 K, and zero resistance at 75 K. The tetragonal unit cell (P4/mmm, a=3.800 Å;c=12.072 Å, deduced from powder data) contains double copper oxygen sheets (like 4424 and 123) that alternate withsingle thallium-bismuth oxygen sheets (in contrast to 4424, which containsdouble bismuth oxygen sheets), resulting in a total of three stacked perovskite-like cells (as in 123). The copper oxide sheets (with intersheet spacing 3.38 Å) are separated by Ca2+ and the Cu oxide sheets and (Tl,Bi) oxide sheets (with spacing 4.35 Å) are separated by Sr2+, Ca2+, and excess (Tl,Bi)3+. The 1212 cell constitutes the building block for the centered, more complex 4424 cell. The 1212 structure persists to Bi contents as low as 1% and can also be stabilized by Pb instead of Bi; Tl cuprates also form other superconductors with lowerT c .
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00617665
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