Journal ArticleDOI

# Effect of oxide additives on the properties of high temperature superconductor, YBa2Cu3O7

01 Mar 1989-Bulletin of Materials Science (Springer India)-Vol. 12, Iss: 1, pp 81-93

TL;DR: The effect of oxide additives on sintering and superconducting properties of YBa2Cu3O7 was studied in this article, and the best results were obtained with Bi2O3, SiO2 and Y2O 3.

AbstractThe effect of oxide additives-CuO, SiO2, Y2O3, Bi2O3 and ZnO in 1–10 mol% on the sintering and superconducting properties of YBa2Cu3O7 was studied. SEM studies indicated improvement of grain size and interconnectivity due to the additives, the best results being obtained with Bi2O3, SiO2 and Y2O3. The superconducting transition temperature is unaffected (92±2 K) even with 10 mol % of the additives. ZnO, however, decreases theT c as expected.

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Jacob Koshy
TL;DR: In this paper, a tetragonal to orthorhombic transformation has taken place within seconds, indicating that the rate of oxygen absorption has increased tremendously by HfO2 addition.
Abstract: Superconductivity in YBa2Cu3O7−δ with HfO2 addition has been studied by x‐ray diffraction, temperature‐resistivity measurements, and scanning electron microscopy. The studies revealed that HfO2 addition up to 5 wt % does not have any detrimental effect on the superconducting properties of YBa2Cu3O7−δ. It is also found that the widely accepted procedure of slow cooling or prolonged heating at 600 °C for oxygenation of the samples is not essential to obtain superconductivity in an HfO2‐added YBa2Cu3O7−δ system. A superconducting transition (92 K) was obtained by directly quenching the HfO2‐added samples in air from a sintering temperature of 950 °C. A tetragonal to orthorhombic transformation has taken place within seconds, indicating that the rate of oxygen absorption has increased tremendously by HfO2 addition. The implications are discussed.

6 citations

Journal ArticleDOI
TL;DR: In this paper, the authors explored the possibility of substituting Bi for Nd in orthorhombic NdBa2Cu3O676, a new cubic compound witha=0.8703 nm, and showed that a poorly crystallized oxygen-deficient form of this compound is already present prior to reheating.
Abstract: Attempts to substitute Bi for Nd in orthorhombic NdBa2Cu3O y , prepared in air or oxygen at about 950°C led instead to formation of Ba2NdBiO6, a new cubic compound witha=0.8703 nm. The possibility was then explored of preparing superconducting (Nd1−x Bi x )Ba2Cu3O y , by first forming the tetragonal phase at 880–950°C in nitrogen or argon followed by reheating in oxygen or air at 250–500°C in order to insert the additional oxygen required to yield the orthorhombic form while avoiding oxidation of Bi3+ to Bi5+. X-ray diffraction studies, electrical conductivity measurements, and thermogravimetric analysis of products indicate that Bi does not enter the NdBa2Cu3O y , lattice in either the tetragonal or the orthorhombic phase. Ba2NdBiO6 clearly forms on reheating in oxygen or air even at low temperatures, and evidence is presented that a poorly crystallized oxygen-deficient form of this compound is already present prior to the reheating.

1 citations

##### References
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Journal ArticleDOI
, Li Gao2
TL;DR: A stable and reproducible superconductivity transition between 80 and 93 K has been unambiguously observed both resistively and magnetically in a new Y-Ba-Cu-O compound system at ambient pressure.
Abstract: A stable and reproducible superconductivity transition between 80 and 93 K has been unambiguously observed both resistively and magnetically in a new Y-Ba-Cu-O compound system at ambient pressure. An estimated upper critical field H c2(0) between 80 and 180 T was obtained.

5,758 citations

Journal ArticleDOI

TL;DR: Observation de la transition supraconductrice a 91 K, sur 1,5 K and determination of the densite de courant critique, de l'effet Meissner, du champ critique, du parametre de Sommerfeld, de parametres GL.
Abstract: We have prepared and identified as a single phase the high-temperature superconducting compound in the chemical system Y-Ba-Cu-O, an orthorhombic, distorted oxygen-deficient perovskite of stoichiometry ${\mathrm{Ba}}_{2}$${\mathrm{YCu}}_{3}$${\mathrm{O}}_{9\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ (\ensuremath{\delta}\ensuremath{\simeq}2.1). Samples exhibit zero resistance at 91 K, with a transition width of 1.5 K. The Meissner effect attains a value of 76% of the independently measured diamagnetic susceptibility. We estimate parameters that characterize this superconductor, e.g., \ensuremath{\gamma}\ensuremath{\simeq}3--5 mJ (mole Cu${)}^{\mathrm{\ensuremath{-}}1}$ ${\mathrm{K}}^{\mathrm{\ensuremath{-}}2}$. The critical current density at 77 K and H=0 exceeds 1100 A/${\mathrm{cm}}^{2}$.

1,254 citations

Journal ArticleDOI
, Li Gao1
TL;DR: An apparent superconducting transition with an onset temperature above 40 K has been detected under pressures in the La-Ba-Cu-O compound system synthesized directly from a solid-state reaction of La/sub 2/O/ sub 3/, CuO, and BaCO/sub 3/ followed by a decomposition of the mixture in a reduced atmosphere.
Abstract: An apparent superconducting transition with an onset temperature above 40 K has been detected under pressure in the La-Ba-Cu-O compound system synthesized directly from a solid-state reaction of La2O3, CuO, and BaCO3 followed by a decomposition of the mixture in a reduced atmosphere. The experiment is described and the results of effects of magnetic field and pressure are discussed.

1,111 citations

Journal ArticleDOI
01 Jul 1975

736 citations

Journal ArticleDOI

TL;DR: The superconducting critical current in these films at 77 K is in excess of ${10}^{5}$ A/${\mathrm{cm}}^{2}$ and at 4.2 K in addition to this.
Abstract: We have grown epitaxial films of the ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$ compound on ${\mathrm{SrTiO}}_{3}$ substrates. The superconducting critical current in these films at 77 K is in excess of ${10}^{5}$ A/${\mathrm{cm}}^{2}$ and at 4.2 K in excess of ${10}^{6}$ A/${\mathrm{cm}}^{2}$.

692 citations