The effect of heat treatment on the properties of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub {delta}}
- Institute of Solid-State Chemistry, Ekaterinburg (Russian Federation)
In synthesis of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 2}O{sub {delta}} (2-2-2-3 phase), which is known to belong to a homologous series of bismuth-based superconductors, several routes have been reported to date to yield materials with a high content, around 95% of the main phase. This phase is characterized by the highest superconducting-transition temperature {Tc} among all known high-{Tc} materials. Based on literature data, heat-treatment conditions are expected to affect strongly the {Tc} of the 2-2-2-3 phase, as they do for other high-{Tc} materials. An optimal oxygen content in 2-2-2-3 was presumed to be the deciding factor for attainment of high {Tc}`s. However, heating below {approximately} 870 K in air causes no change in oxygen content in the 2-2-2-3 phase. At the same time, it is oxidizing annealing at T < 970 K that increases {Tc} up to 105-110 K. The conclusions found that changes in oxygen content for (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 2}O{sub {delta}} (2-2-2-3 phase) do not affect T{sub c}, which remains unchanged after shor anneals at 370-1020 Kelvin in different atmospheres. In order to obtain high T{sub c}`s, it will suffice to exclude long anneals at 1020-1090 Kelvin from the technology. For the 2-2-2-3 phase, a degradation process, which does not change the composition of the phase, is like that for YBa{sub 2}Cu{sub 3}O{sub 6+delta}. Proposed is that different structural planes participate in mass exhanage with an atmosphere: (BiO) planes which do not participate to superconductivity, participate in oxygen exchange; and H{sub 2}O and CO{sub 2} penetrate into the CuO{sub 2} planes, which are responsible for superconductivity in the 2-2-2-3 phase.
- OSTI ID:
- 98716
- Journal Information:
- Inorganic Materials, Vol. 30, Issue 8; Other Information: PBD: Aug 1994; TN: Translated from Neorganicheskie Materialy; 30: No. 8, 1074-1077(1994)
- Country of Publication:
- United States
- Language:
- English
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