Effect of oxide additives on the properties of high temperature superconductor, YBa2Cu3O7
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.
Abstract: The 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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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
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
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TL;DR: In this article, the effect of transition-metal impurities on the superconducting properties of Y1Ba2Cu3O7-x was studied and the transition temperature was found to be sensitive to the orthorhombic-tetragonal phase transition, which in turn depends on a number of elemental properties including the oxidation state.
Abstract: The effect of transition-metal impurities on the superconducting properties of Y1Ba2Cu3O7-x was studied and the transition temperature was found to be sensitive to the orthorhombic-tetragonal phase transition, which in turn depends on a number of elemental properties including the oxidation state. Thermodynamic calculations show that dopants with high oxidation states have the same effect as oxygen partial pressure in stabilising the superconducting orthorhombic phase. This effect is consistent with experimental results.
20 citations
TL;DR: In this article, a high-Tc superconductor Y1Ba2Cu3O7−x has been fabricated through the powder metallurgy technique and a critical current density of 26·4 A cm−2 (77K, 0T) is obtained in these wires.
Abstract: Silver clad wires of highTc superconductor Y1Ba2Cu3O7−x have been fabricated through the powder metallurgy technique. The reacted wires show a midpointTc of 84K. A critical current density of 26·4 A cm−2 (77K, 0T) is obtained in these wires. The wires, however, turn complete normal only at a current density of 280 A cm−2. The reasons for low critical current density obtained in these wires are discussed.
10 citations
9 citations
TL;DR: In this paper, the structure and stoichiometry of YBa2Cu3O7+δ and other high-Tc oxide superconductors are discussed, and the nature of Cu and the importance of the Cu3+/Cu2+ ratio in these copper oxides are pointed out.
Abstract: Some interesting aspects of the structure and stoichiometry of YBa2Cu3O7+δ and other high-Tc oxide superconductors are discussed. The nature of Cu and the importance of the Cu3+/Cu2+ ratio in these copper oxides are pointed out. Marginal metallicity of the non-superconducting phase in these oxides as an important factor in the mechanism is indicated. Effect of Y substitution in YBa2Cu3O7+δ by other rare earths is commented upon.
9 citations
TL;DR: In this paper, the successful extrusion of short lengths of brittle wires of YBa2Cu3O that are superconducting above 77 K was reported, and detailed critical current measurements were presented on wires having undergone different physical treatments.
Abstract: The successful extrusion of short lengths of brittle wires of YBa2Cu3O
y
that are superconducting above 77 K is reported. Detailed critical current measurements are presented on wires having undergone different physical treatments. The highest critical current obtained from V-I data is ⋍ 90 A/cm2, but this particular wire shows clear evidence of flux-pinning forces corresponding to ⋍ 130 A/cm2.
8 citations