The Role of Oxygen in the Hot Isostatic Pressing of High Tc Superconductors

1991 ◽  
Vol 251 ◽  
Author(s):  
John V. Niska ◽  
Bengt Loberg
Keyword(s):  
Hot Isostatic Pressing ◽  
Base Metals ◽  
High Tc Superconductors ◽  
Oxygen Loss ◽  
High Tc ◽  
Energy Diagram ◽  
Free Energy Diagram ◽  
Ellingham Diagram ◽  
The Stability

ABSTRACTThe bismuth-based 2212 and 2223 superconductors and the yttrium-based 123 and 124 high Tc superconductors are oxide ceramics, so that oxidizing conditions must be maintained in the HIP to avoid oxygen loss and decomposition. This has been done in an argon gas HIP by using glass encapsulation, but internal gas pressure retards densification. The thermodynamics of the release of oxygen by the superconductive ceramics and the stability of the metal to oxygen can be shown on a free energy diagram (Ellingham diagram). The base metals (as Fe and Cu) are reactive with respect to superconductive ceramics but not silver.

THE VAN HOVE SINGULARITY IN HIGH Tc SUPERCONDUCTORS

1995 ◽  
Vol 09 (09) ◽  
pp. 1067-1080 ◽  
Author(s):  
M.L. HORBACH ◽  
H. KAJÜTER
Keyword(s):  
Energy Scale ◽  
Measured Temperature ◽  
Van Hove Singularity ◽  
High Tc Superconductors ◽  
Electronic Density ◽  
High Tc ◽  
Scattering Rate ◽  
Weakly Coupled ◽  
Coherence Lengths

Experimental indications for the role of the van Hove singularity (vHs) in the electronic density of states of high Tc superconductors are discussed. It is argued that (i) like the resistivity, the measured temperature and doping dependences of the normal state electronic specific heat of YBCO are consistent with the existence of a vHs and (ii) the doping dependence of Tc in the underdoped and optimally doped regimes may be accounted for mainly by a vHs. Further, we discuss the suppression of the quasiparticle scattering rate below Tc, and the coherence lengths in the hole-doped materials and NCCO. Assuming that the same mechanism for superconductivity operates in the electron-doped and the hole-doped cuprates, we argue that the bosonic mode that causes the superconductivity is strongly influenced by the doping in the overdoped regime. We further argue that this boson involves an energy scale larger than that of phonons and is only weakly coupled to the charge carriers.

Role of Cu in high Tc superconductors: A photoemission study

1988 ◽  
Vol 153-155 ◽  
pp. 153-154 ◽  
Author(s):  
P. Sen ◽  
B. Dauth ◽  
T. Kachel ◽  
B. Rupp ◽  
W. Gudat
Keyword(s):  
High Tc Superconductors ◽  
High Tc ◽  
Photoemission Study

CHARGE CARRIER MASS IN HIGH Tc SUPERCONDUCTORS

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3582-3584
Author(s):  
MARCO ZOLI
Keyword(s):  
Charge Carrier ◽  
Numerical Study ◽  
Small Polaron ◽  
Electron Mass ◽  
High Tc Superconductors ◽  
High Tc ◽  
Effective Masses ◽  
Polaron Theory ◽  
Holstein Model

The theory of polarons has experienced a surge of activity in the last years partly due to the possible role of polaronic quasiparticles in high Tc superconductors. This numerical study of the Holstein model shows that the polaronic effective masses become essentially dimension independent and of order ≃10–50 times the electron mass at sufficiently strong intermolecular coupling forces. Such values (which are much lower than those obtained by traditional small polaron theory) would erase one the serious objections against a (bi)polaronic picture for high Tc superconductors.

DESCRIPTION OF THE Tl, Pb and Bi CUPRATE HIGH-Tc SUPERCONDUCTORS AS INTERCALATION COMPOUNDS

1989 ◽  
Vol 03 (09) ◽  
pp. 723-728 ◽  
Author(s):  
R.S. MARKIEWICZ ◽  
B.C. GIESSEN
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Intercalation Compounds ◽  
Acceptor Site ◽  
High Tc Superconductors ◽  
High Tc ◽  
Stage Number ◽  
Graphite Intercalation ◽  
Superconducting Oxides

Treating the new superconducting oxides as intercalation compounds, especially, as analogues to graphite intercalation compounds (GIC), clarifies the understanding of a number of their properties; in this description, the ratio of the number of cuprate layers per intercalant unit is equivalent to the stage number in GIC’s. In particular, the role of charge transfer (presumably, electron transfer from oxygen in the [Formula: see text] sheets to an acceptor site located in the intercalant) in optimizing Tc can be well discussed in these terms, leading to the prediction that the curve of Tc versus n, the number of [Formula: see text] layers, must have a maximum at a specific value of n.

On the role of doping in high-Tc superconductors

1994 ◽  
Vol 52 (S28) ◽  
pp. 687-693 ◽  
Author(s):  
Changjiang Mei ◽  
Vedene H. Smith
Keyword(s):  
High Tc Superconductors ◽  
High Tc

The role of Cu−O chain fragments in the REBa2Cu3O6+x high-Tc superconductors

1996 ◽  
Vol 46 (S2) ◽  
pp. 967-968 ◽  
Author(s):  
D. R. Grempel ◽  
H. Haugerud ◽  
G. Uimin ◽  
W. Selke
Keyword(s):  
High Tc Superconductors ◽  
High Tc
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