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.
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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.
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TL;DR: In this paper, the oxygen-deficient phase of the highTc superconductor, YBa2Cu3O7, was enriched using the fluidization technique to give good superconducting properties.
Abstract: The oxygen-deficient phase of the highTc superconductor, YBa2Cu3O7, was oxygen-enriched using the fluidization technique to give good superconducting properties. The normal method of oxygen treatment at 900°C for 24 h and at 600°C for 24 h has been reduced to just one treatment at 600°C for 12 h by the fluidization technique to achieve almost the same strength of superconducting signal for the YBa2Cu3O7 powder, which establishes the attractiveness of the latter route for the large-scale preparation of superconducting material. The particle sizes were in the range 0–90, 90–180 and 180–420 µm. The fluidized particles were crystalline with orthorhombic distortion.Tconset, estimated using the a.c. magnetic susceptibility method, was 91·3 K. The volume fraction of superconducting material in the product was 83·7–85·3%, one of the highest values reported so far for YBa2Cu3O7.
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TL;DR: In this paper, the results of x-ray diffraction, electrical resistance, DC and AC magnetization studies on two specimens of compositions Y2.1Ba3.9Cu6O14 and Y1.8Ba4.2Cu 6O14 are presented.
Abstract: The results of x-ray diffraction, electrical resistance, DC and AC magnetization studies on two specimens of compositions Y2.1Ba3.9Cu6O14 and Y1.8Ba4.2Cu6O14 are presented. Our studies confirm that La3Ba3Cu6O14 type ortnornombic phase is responsible for superconductivity in 90K range. The heat treatment that yields high quality samples with sharp transition in electrical resistance as well as in AC magnetic susceptibility measurements is described. Magnetic response just below Tc is found to be sensitive to the measuring field.
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