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 paper, an increase of a factor up to 5 in JC on mixing varying amounts of Ag2O with YBa2Cu3O7 was reported, which correlates with an increase in texture as seen by x-ray diffraction intensities.
Abstract: We report an increase of a factor up to 5 in JC on mixing varying amounts of Ag2O with YBa2Cu3O7. The increase correlates with an increase in texture as seen by x‐ray diffraction intensities. Microstructure indicates the formation of platelets with c axis normal to the platelets.
51 citations
28 citations
TL;DR: The oxide responsible for high-temperature superconductivity (onet ∼100 K, zero resistance above liquid N2 temperature) was found to be YBa2Cu3O7±δ as mentioned in this paper.
Abstract: The oxide responsible for high-temperature superconductivity (onset ∼100 K, zero resistance above liquid N2 temperature) is found to be YBa2Cu3O7±δ.
26 citations
TL;DR: In this paper, the low temperature specific heat and electrical resistivity of YBa2Cu3O6.8 and YBa 2Cu3o6.0 have been measured at a temperature range from 2 K to 40 K. A strong current density dependence was observed.
Abstract: The low temperature specific heat and electrical resistivity of YBa2Cu3O6.8 and YBa2Cu3O6.0 have been measured. The specific heat data were taken at a temperature range from 2 K to 40 K. Abnormal upturns at the lower temperature end and a large electron contribution were observed in the C/T vs T2 curve. The resistivity ρ was measured from 20 K to 270 K for YBa2Cu3O6.0. A strong current density dependence was observed. Log ρ measured at low current density was found to show T-1/3 dependence below 170 K.
26 citations
TL;DR: In this article, the absolute thermopower of single phase YBa2Cu3O7 and Y0.8Er0.2Ba2C 3O7 has been measured in the range 250 K to the superconducting transition temperature.
Abstract: The absolute thermopower of single phase YBa2Cu3O7 and Y0.8Er0.2Ba2Cu3O7 has been measured in the range 250 K to the superconducting transition temperature. It is found that these compounds show a large enhancement of thermopower in the range 150 K down toT
c. This enhancement shows a steep exponential drop as the temperature increases from the transition temperature. The temperature variation of the enhancement is too steep to be accounted for by electron-phonon or electron-local structural excitation mechanisms.
24 citations