Oxygen Stoichiometry and the High Tc Superconducting Oxides

MRS Bulletin ◽  
1989 ◽  
Vol 14 (1) ◽  
pp. 53-57 ◽  
Author(s):  
J-M. Tarascon ◽  
B.G. Bagley
Keyword(s):  
Optical Properties ◽  
Liquid Nitrogen ◽  
Broad Spectrum ◽  
Low Temperatures ◽  
Large Family ◽  
Oxygen Stoichiometry ◽  
High Tc ◽  
Metallic Conductivity ◽  
Superconducting Oxides ◽  
Technological Interest

Oxide compounds have been extensively studied through the years because they exhibit a broad spectrum of electrical, magnetic, and optical properties providing both scientific and technological interest. Most oxides are insulators, but a few of them (e.g., LiTi2O4 or BaPb1−x BixO3 show metallic conductivity and even superconductivity at low temperatures. The discovery of superconductivity at 35 K by Bednorz and Müller in the cuprate La-Ba-Cu-O system prompted the search for other high Tc compounds among this oxide family. Superconductivity above liquid nitrogen was then rapidly achieved with the Y-Ba-Cu-O system (Tc=90 K) and subsequently, with the Bi-Sr-Ca-Bu-O and Tl-Ba-Ca-Cu-O systems, Tc was raised to 110 K and then 125 K.A common feature of these new high Tc cuprates is that they belong to the large family of materials, termed perovskites, which have been studied over the years because of their ability to absorb or lose oxygen reversibly (i.e., for their nonstoichiometry in oxygen). It had been previously established in the field of superconductivity that Tc is extremely sensitive to compositional stoichiometry.

Oxygen stoichiometry and physical properties of high-Tc superconducting oxides

Physica B+C ◽  
1987 ◽  
Vol 148 (1-3) ◽  
pp. 349-352 ◽  
Author(s):  
H. Takagi ◽  
S. Uchida ◽  
H. Iwabuchi ◽  
H. Eisaki ◽  
K. Kishio ◽  
...  
Keyword(s):  
Physical Properties ◽  
Oxygen Stoichiometry ◽  
High Tc ◽  
Superconducting Oxides

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.

STUDY OF THE DEPENDENCE OF HIGH Tc ON VARIOUS SINTERING TEMPERATURES FOR Bi-Pb-Sr-Ca-Cu-O SUPERCONDUCTORS

1991 ◽  
Vol 05 (24n25) ◽  
pp. 1635-1638
Author(s):  
S.M. M.R. NAQVI ◽  
A.A. QIDWAI ◽  
S.M. ZIA-UL-HAQUE ◽  
FIROZ AHMAD ◽  
S.D.H. RIZVI ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Liquid Nitrogen ◽  
X Ray Diffraction ◽  
High Tc ◽  
X Ray ◽  
Resistivity Measurements ◽  
Zero Resistance

Bi1.7-Pb0.3-Sr2-Ca2-Cu3-Ox superconducting samples were prepared at 855°C, 862 C, 870 C, and 882 C sintering temperatures respectively. All samples were sintered for 120 hours. The samples were then quenched in liquid nitrogen. The electrical resistivity measurements showed that the samples sintered at 870° C had the best Tc. For these samples the Tc onset was around 120 K and the zero resistance was obtained at 108 K. X-ray diffraction studies showed that the samples were multiphased.

Hydrogen in Crystalline Silicon

1985 ◽  
Vol 59 ◽  
Author(s):  
S. J. Pearton
Keyword(s):  
Low Temperatures ◽  
Atomic Hydrogen ◽  
Crystalline Silicon ◽  
Deep Level ◽  
Surface Damage ◽  
Defect Complexes ◽  
Microscopic Models ◽  
Related Defect ◽  
Shallow Acceptors ◽  
Technological Interest

ABSTRACTThe ability of hydrogen to migrate in crystalline Si at low temperatures (<400°C) and bond to a variety of both shallow and deep level impurities, passivating their electrical activity, is of fundamental and technological interest. Recent results on the deactivation of the shallow acceptors in Si are compared with similar experiments in other semiconductors, microscopic models are proposed, and the implications for the states of hydrogen in the Si lattice at a variety of temperatures, and the diffusivity of some of these different states, is discussed. New results on the migration of atomic hydrogen under electronic stimulation are also detailed, along with a compendium of the deep levels in Si passivated by reaction with hydrogen. Surface damage by hydrogen-containing plasmas, and the infrared and electrical properties of H-related defect complexes are also reviewed.

NANOSCOPIC PHASE SEPARATION AND THE UNIVERSAL TRANSPORT AND MAGNETIC PROPERTIES OF HIGH Tc SUPERCONDUCTORS

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3528-3531
Author(s):  
J. JUNG ◽  
H. YAN ◽  
H. DARHMAOUI ◽  
M. ABDELHADI
Keyword(s):  
Magnetic Properties ◽  
Phase Separation ◽  
Temperature Dependence ◽  
Current Density ◽  
Low Temperatures ◽  
Energy Barrier ◽  
Vortex Motion ◽  
Superfluid Density ◽  
High Tc Superconductors ◽  
High Tc

We have found the correlation between nanoscopic phase separation in the copper-oxygen planes of YBCO and TlBCCO and the transport and magnetic properties of these materials in the a-b planes such as: the temperature dependence of the critical current density Jc( T ), the temperature dependence of the superfluid density ns( T )∝1/λ2( T ) at low temperatures, the temperature dependence of the normalized logarithmic relaxation rate S(T), and the dependence of the effective energy barrier against vortex motion on the current density Ueff( J ). These properties are controlled by the ratio of the amount of an underdoped filamentary phase to that of an optimally doped one.

Sign in / Sign up

Export Citation Format

Share Document