Correlation of Tc with hole concentration in La2-xSrx
IBM1
TL;DR: In this paper, the electron deficiency (hole concentration) in a superconducting system was determined by a chemical method and the results showed a direct correlation between the hole concentration and the Sr concentration.
Abstract: The electron deficiency (hole concentration) in the ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}\mathrm{Cu}{\mathrm{O}}_{4\ensuremath{-}\ensuremath{\delta}}$ system is determined by a chemical method. Our results show a direct correlation between ${T}_{c}$ and hole concentration. The hole concentration equals the Sr concentration to about $x=0.15$. For $xg0.15$, the hole concentration decreases and oxygen vacancies are formed. These results strongly support an all-electronic mechanism for superconductivity in this system.
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IBM1
TL;DR: In this article, a review on the problems of high-temperature superconductivity is presented, and ideas encouraging the search for high-time superconductivities are elucidated.
Abstract: The review dwells on the problems of high-temperature superconductivity. Ideas encouraging the search for high-temperature superconductivity are elucidated. The way from cubical alloys, containing niobium, to laminated copper-containing oxides with the perovskite-type structure is shown. Properties of new laminated oxide superconductors are described.
492 citations
TL;DR: In this article, the authors highlight the important roles played by crystal chemistry in controlling the superconductive properties of the intergrowth structures of the copper oxides and show that the coordination geometry preferred by different oxidation states of Cu appears to control the oxygen ordering and the Tc variation in the YBa2Cu3O6+x system.
184 citations
TL;DR: A comprehensive review of structure work on high-Tc oxides as reported during the years 1987 and 1988 is given in this paper, where 13 structures are refined from X-ray single-crystal and/or neutron powder diffraction data.
Abstract: A comprehensive review of structure work on high-Tc oxides as reported during the years 1987 and 1988 is given. Thirteen structures are refined from X-ray single-crystal and/or neutron powder diffraction data:I. (Ba1−x,Kx)BiO3 (Tc=30 K),II. (La2−x, Srx)CuO4 (Tc=40 K),III. (Nd, Ce, Sr)2CuO4 (Tc=28 K),IV. (Nd2−x, Cex)CuO4 (Tc=24 K),V. YBa2Cu3O7 (Tc=90 K),VI. YBa2Cu4O8 (Tc=80 K),VII. Y2Ba4Cu7O14 (Tc=40 K),VIII. Pb2Sr2NdCu3O8 (Tc=70 K),IX. TlBa2CaCu2O7 (Tc=103 K),X. TlBa2Ca2Cu3O9 (Tc=120 K),XI. Tl2Ba2CuO6 (Tc=90 K),XII. Tl2Ba2CaCu2O8 (Tc=112 K),XIII. Tl2Ba2Ca2Cu3O10 (Tc=125 K). Except forI (perovskite type),II (K2NiF4 type) andIV (Nd2CuO4 type) they represent new structure types. Structure data, bond distances, structure drawings and calculated X-ray powder diffraction patterns are given for each compound. Structural features and correlations with superconductivity are discussed. The review contains 301 citations.
182 citations
TL;DR: Growth conditions for YBaCuO thin films are investigated in this article, and it is found that in conditions of lower oxygen, pressure films with average composition off the 1-2-3 stoichiometry have higher Tc's.
Abstract: Growth conditions for YBaCuO thin films are investigated. Films have been made by reactive e-beam coevaporation using three metal sources. In the best cases, as-made films are superconducting with Tc's (R = 0) up to 90 K and Jc's (at 4.2 K) above 107 A/cm2. Oxygen pressure, deposition temperature, as well as compositional dependencies of the films are presented. It is found that in conditions of lower oxygen, pressure films with average composition off the 1–2–3 stoichiometry have higher Tc's. For pressure 100 mTorr). The expanded c0's for these films cannot be reduced by a low temperature oxygen anneal. We suggest that metal-atom point-like defects are quenched into these films and we discuss a particular Ba-for-Y substitution model.
170 citations
166 citations