Crystal chemistry of high-Tc superconductors

1990 ◽  
Vol 48 (4) ◽  
pp. 1118-1119
Author(s):  
Maryvonne Hervieu
Keyword(s):  
Oxygen Deficiency ◽  
Large Family ◽  
Copper Oxides ◽  
High Tc Superconductors ◽  
High Tc ◽  
Single Mechanism ◽  
Square Planar ◽  
History Of ◽  
Bismuth Cuprates ◽  
New Compounds

Four years after the discovery of superconductivity at high temperature in the Ba-La-Cu-O system, more than thirty new compounds have been synthesized, which can be classified in six series of copper oxides: La2CuO4 - type oxides, bismuth cuprates, YBa2Cu3O7 family, thallium cuprates, lead cuprates and Nd2CuO4 - type oxides. Despite their quite different specific natures, close relationships allow their structures to be simply described through a single mechanism. The fifth first families can indeed be described as intergrowths of multiple oxygen deficient perovskite slabs with multiple rock salt-type slabs, according to the representation [ACuO3-x]m [AO]n.The n and m values are integer in the parent structures, n varying from 0 to 3 and m from 1 to 4; every member of this large family can thus be symbolized by [m,n]. The oxygen deficient character of the perovskite slabs involves the existence or the co-existence of several types of copper environment: octahedral, pyramidal and square planar.Both mechanisms, oxygen deficiency and intergrowth, are well known to give rise easily to nonstoichiometry phenomena. Numerous and various phenomena have actually been characterized in these cuprates, strongly depending on the thermal history of the samples.

Mixed-valence copper oxides: A large family of high Tc superconductors related to the perovskites

1989 ◽  
Vol 33 (2) ◽  
pp. 109-121 ◽  
Author(s):  
C. Michel ◽  
M. Hervieu ◽  
J. Provost ◽  
B. Raveau
Keyword(s):  
Mixed Valence ◽  
Large Family ◽  
Copper Oxides ◽  
High Tc Superconductors ◽  
High Tc

scholarly journals Synthesis and characterization of Pr substituted Gd-123 high-Tc superconductors

Cerâmica ◽  
2012 ◽  
Vol 58 (347) ◽  
pp. 381-387 ◽  
Author(s):  
V. R. Huse ◽  
V. D. Mote ◽  
Y. Purushotham ◽  
B. N. Dole
Keyword(s):  
Oxygen Deficiency ◽  
Resistivity Measurement ◽  
Charge Carriers ◽  
Electrical Resistivity Measurement ◽  
Chemical Formula ◽  
Curie Constant ◽  
High Tc Superconductors ◽  
High Tc ◽  
Magnetic Pair

High Tc superconducting materials with chemical formula Gd1-xPr xBa2Cu3O7-δ, where x = 0.0, 0.1, 0.2 and 0.3 were prepared by ceramic route. XRD studies confirm the orthorhombic pervoskite structure. Electrical resistivity measurement shows that Tc decreases with increasing Pr concentration. Copper valency and oxygen content decreasing with increasing Pr content. Value of n(CuO2) decreases with increasing x and oxygen deficiency (δ) has a linear dependence with (2x+δ). SQUID investigation reveals that Bohr magneton number and Curie constant are decreasing with increasing Pr concentration. Annihilation of superconductivity may be owing to reduction in CuO2 charge carriers or magnetic pair breaking.

RECENT STRUCTURAL DEVELOPMENTS IN COPPER OXIDES HIGH-Tc SUPERCONDUCTORS

1987 ◽  
Vol 01 (03n04) ◽  
pp. 733-744 ◽  
Author(s):  
B. RAVEAU ◽  
M. HERVIEU ◽  
C. MICHEL ◽  
J. PROVOST
Keyword(s):  
Copper Oxides ◽  
High Tc Superconductors ◽  
High Tc

Effect of thermomagnetic history of field-cooled magnetization on the irreversibility line in conventional and high-Tc superconductors

1994 ◽  
Vol 194-196 ◽  
pp. 1857-1858
Author(s):  
Ravi Kumar ◽  
A.V. Volkozub ◽  
P.A.J. de Groot ◽  
A.K. Grover ◽  
S.K. Malik
Keyword(s):  
Irreversibility Line ◽  
High Tc Superconductors ◽  
High Tc ◽  
History Of

A Model for Correlated Valence Fluctuation in High Tc Superconductors

1987 ◽  
Vol 01 (03n04) ◽  
pp. 1049-1055 ◽  
Author(s):  
W.Y. Liang
Keyword(s):  
Simple Model ◽  
Binding Energies ◽  
Copper Oxides ◽  
High Tc Superconductors ◽  
Valence Fluctuation ◽  
Electron Pairs ◽  
High Tc ◽  
High Binding ◽  
Coulomb Attraction

A simple model is proposed as a possible mechanism for high T c superconductivity in certain copper oxides based on correlated valence fluctuation. Electron pairs are formed by Coulomb attraction between electrons in mainly Cu2+ ( d 9 configuration) pyramidal planes mediated by Cu 3+ ( d 8 configuration) ions in the CuO 4 chain-like plane in YBa2Cu3O7−x . These electron pairs have high binding energies necessary for high Tc , and the model is capable of explaining a number of other observed properties.

Structure of High Tc Oxide Superconductors

MRS Bulletin ◽  
1989 ◽  
Vol 14 (1) ◽  
pp. 27-30 ◽  
Author(s):  
Ivan K. Schuller ◽  
J.D. Jorgensen
Keyword(s):  
Variable Number ◽  
Oxide Superconductors ◽  
Detailed Knowledge ◽  
Coupling Mechanism ◽  
High Tc ◽  
Square Planar ◽  
Structural Principles ◽  
The Common ◽  
The Individual ◽  
New Compounds

Our understanding of the superconducting mechanism in the newly discovered oxide superconductors is closely connected with a detailed knowledge of the structural properties displayed by these materials. Moreover, it is important to explore possible connections between structural and superconducting properties and to establish general structural principles which can guide our search for new compounds.We present here a survey of the structures of the recently discovered oxide superconductors. The common feature of these structures (with the exception of cubic Ba1-x Kx BiO3-y) is the presence of one or more planes of copper atoms with four strongly bonded oxygen atom neighbors in a square planar arrangement at a distance of approximately 1.90 Å (“CuO2 planes”). In some structures these planes occur in groups, with the individual planes inside a group being separated by one Y or Ca layer and the groups being intercalated by a variable number of LaO, BaO, CuO, TIO and/or BiO layers. (The intercalated CuO layer is crystallographically distinct from the “CuO2 plane”). A natural model for superconductivity which arises from these structures is that the conductivity occurs predominantly in the Cu02 planes, while the other (intercalated) layers provide in some fashion carriers and/or the coupling mechanism necessary for the superconductivity.

ON THE RELEVANCE OF THE CONVENTIONAL BAND THEORY IN CASE OF HIGH-Tc SUPERCONDUCTORS: OPTICS OF La2−xSrxCuO4

1988 ◽  
Vol 02 (05) ◽  
pp. 883-891 ◽  
Author(s):  
E. G. Maksimov ◽  
I. I. Mazin ◽  
S. N. Rashkeev ◽  
S. Y. Savrasov ◽  
Yu. A. Uspenski
Keyword(s):  
Band Structure ◽  
Plasma Frequency ◽  
Copper Oxides ◽  
Band Structure Calculation ◽  
High Tc Superconductors ◽  
Band Theory ◽  
High Tc ◽  
Band Structure Calculations ◽  
Reflectivity Spectra ◽  
Structure Calculations

We discuss the question of the applicability of conventional band structure calculation to superconducting copper oxides. We show that optical spectra of La 2−x Sr x CuO 4 are reasonably described by LMTO band structure calculations. In fact, 20% reduction of calculated plasma frequency and introducing interband relaxation makes theoretical reflectivity spectra to reproduce essentially all features of single-crystal experimental reflectivity.

Defect Chemistry of High Tc Superconductors

1990 ◽  
Vol 209 ◽  
Author(s):  
Kazuo Fueki ◽  
Yasushi Idemoto
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Master Curve ◽  
Oxygen Deficiency ◽  
Smooth Curve ◽  
Mass Action ◽  
High Tc Superconductors ◽  
High Tc ◽  
Mass Action Law ◽  
Data Points

ABSTRACTThe oxygen deficiency δ in YBa2Cu3O7−δ was determined as a function of oxygen partial pressure and temperature. It was found that all the δ−log Po2 data points fall on a single smooth curve (master curve) when the points for each temperature were shifted in parallel with each other in the direction of abscissa by a certain distance. A theoretical equation describing the δ−logP02 relation was derived on the basis of electroneutrality, mass action law and site conservation.The theoretical curve agreed well with the experimental hL.Lster curve.

Resistance of High-Tc Superconductors: Review Article

2020 ◽  
Vol 65 (1-2) ◽  
pp. 87-96
Author(s):  
C. Lung ◽  
◽  
D. Marconi ◽  
M. Pop ◽  
A.V. Pop ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
High Temperature Superconductors ◽  
Short Review ◽  
Review Article ◽  
Copper Oxides ◽  
Model Parameters ◽  
High Tc Superconductors ◽  
High Tc ◽  
Normal State Properties ◽  
Ceramic Compounds

"The origin of resistance and its relation to the superconducting mechanism remain a profound, unsolved mystery. Currently, model parameters used to fit normal state properties are specific and vary arbitrarily from one doping. This short review illustrates the electrical resistivity of ceramic high temperature superconductors copper oxides. The article gives a summary of the prevailing arguments of researchers to relate the material to ceramic HTS compounds. Keywords: superconductivity, HTC ceramic compounds, resistivity. "

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