EFFECT OF COOLING RATE ON THE TRANSITION TEMPERATURE IN Bi–Pb–Sr–Ca–Cu–O SYSTEM

1990 ◽  
Vol 04 (04) ◽  
pp. 293-299
Author(s):  
YUGUI WANG ◽  
JINSONG WANG ◽  
NANLIN WANG ◽  
XINPING JIAO ◽  
GUCHANG HAN ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Specific Heat ◽  
Cooling Rate ◽  
Volume Fraction ◽  
Oxygen Deficiency ◽  
Ac Susceptibility ◽  
Rapid Quenching ◽  
Nominal Composition ◽  
Unit Cell Size ◽  
Superconducting Volume Fraction

The resistance and ac susceptibility measurements show that cooling rate of the cast-annealing samples in heat treatment process has some effect on the 110 K superconducting phase in Bi–Pb–Sr–Ca–Cu–O system. Rapid quenching of the sample in air from 845°C causes oxygen deficiency in lattice and brings about a trifling change of unit cell size along c-axis direction. The dc magnetization and specific heat anomaly ∆c measurements demonstrate that fast cooling rate can reduce the transition temperature of high T c phase and the lower critical field, and weaken the pinning forces for vertex lines. The peak value of specific heat anomaly of the sample with nominal composition of Bi 1.7 Pb 0.3 Sr 2 Ca 2 Cu 4.5 O y is still small in comparison with YBa 2 Cu 3 O 7. From the magnetization curve we can estimate that the superconducting volume fraction is about 20%.

STABILIZATION OF Bi(2223) SUPERCONDUCTING PHASE BY VANADIUM OXIDE ADDITION

1993 ◽  
Vol 07 (01n03) ◽  
pp. 157-161 ◽  
Author(s):  
D. SURESH BABU ◽  
G. NARSING RAO ◽  
L. BROHAN ◽  
M. GANNE
Keyword(s):  
Critical Current Density ◽  
Current Density ◽  
Flux Pinning ◽  
Volume Fraction ◽  
Ac Susceptibility ◽  
Superconducting Phase ◽  
Nominal Composition ◽  
Oxide Addition ◽  
Probable Role

We report on the ac susceptibility, microwave absorption and dc magnetization of Bi 2− x V x Sr 2 Ca 2 Cu 3 O y (nominal composition). The low T c (2212) phase ( T c = 85 K ) dominates in the x = 0 sample with extremly weak flux pinning. In x = 0.4 sample, both flux pinning and volume fraction of the high T c (2223) phase ( T c = 105 K ) were increased. The intragrain critical current density of the sample with x = 0.4 was estimated and found to be comparable with that of Pb doped Bi 2 Sr 2 Ca 2 Cu 3 O y superconductor. The data suggest that addition of V 2 O 5 in Bi 2 Sr 2 Ca 2 Cu 3 O y system increases the volume fraction of the high T c phase. Probable role of vanadium in enhancing the high T c (2223) phase in Bi-V-Sr-Ca-Cu-O system is discussed.

Superconductivity of κ-(BEDT–TTF)2 Cu[N(CN) 2]Br: Isotope Effect Revisited

1997 ◽  
Vol 488 ◽  
Author(s):  
M. Tokumoto ◽  
N. Kinoshita ◽  
Y. Tanaka ◽  
H. Anzai
Keyword(s):  
Transition Temperature ◽  
Isotope Effect ◽  
Volume Fraction ◽  
Organic Superconductors ◽  
Organic Superconductor ◽  
Superconducting Transition ◽  
Hydrogen Atoms ◽  
Superconducting Volume Fraction ◽  
Cooling Speed ◽  
Inverse Isotope Effect

AbstractIn 1991, we reported a normal isotope effect in organic superconductor κ-(BEDT–TTF)2Cu[N(CN)2]Br, when all the hydrogen atoms of BEDT – TTF were replaced with deuterium. In other words, Tc was depressed by as much as 0.9 K, in contrast to the “inverse isotope effect” commonly observed in 10K-class organic superconductors. Recently, it was reported that the deuterated κ-(BEDT–TTF)2Cu[N(CN)2]Br shows an insulating nature when cooled very rapidly. Therefore, it is necessary for us to reexamine the superconducting transition of both deuterated and undeuterated κ- (BEDT – TTF)2Cu[N(CN)2]Br by SQUID measurements with special attention to the cooling speed. We studied the effect of cooling rate ranging from 10 K/min down to as slow as 0.02 K/min, and observed a significant effect not only on the superconducting transition temperature Tc but also on the superconducting volume fraction.

scholarly journals Evolution of Shape and Volume Fraction of Superconducting Domains with Temperature and Anion Disorder in (TMTSF)2ClO4

Crystals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 72
Author(s):  
Kaushal K. Kesharpu ◽  
Vladislav D. Kochev ◽  
Pavel D. Grigoriev
Keyword(s):  
Cooling Rate ◽  
Annealing Time ◽  
Volume Fraction ◽  
Density Wave ◽  
Spin Density Wave ◽  
Finite Size ◽  
Organic Superconductors ◽  
Organic Superconductor ◽  
Sample Length ◽  
Sample Shape

In highly anisotropic organic superconductor (TMTSF)2ClO4, superconducting (SC) phase coexists with metallic and spin-density wave phases in the form of domains. Using the Maxwell-Garnett approximation (MGA), we calculate the volume ratio and estimate the shape of these embedded SC domains from resistivity data at various temperature and anion disorder, controlled by the cooling rate or annealing time of (TMTSF)2ClO4 samples. We found that the variation of cooling rate and of annealing time affect differently the shape of SC domains. In all cases the SC domains have oblate shape, being the shortest along the interlayer z-axis. This contradicts the widely assumed filamentary superconductivity along the z-axis, used to explain the anisotropic superconductivity onset. We show that anisotropic resistivity drop at the SC onset can be described by the analytical MGA theory with anisotropic background resistance, while the anisotropic Tc can be explained by considering a finite size and flat shape of the samples. Due to a flat/needle sample shape, the probability of percolation via SC domains is the highest along the shortest sample dimension (z-axis), and the lowest along the sample length (x-axis). Our theory can be applied to other heterogeneous superconductors, where the size d of SC domains is much larger than the SC coherence length ξ, e.g., cuprates, iron-based or organic superconductors. It is also applicable when the spin/charge-density wave domains are embedded inside a metallic background, or vice versa.

Specific heat and ac susceptibility ofHg0.8Cu0.2Ba2CuO4+δsingle crystals withTC=95K

1997 ◽  
Vol 56 (17) ◽  
pp. 10824-10827 ◽  
Author(s):  
B. Billon ◽  
M. Charalambous ◽  
O. Riou ◽  
J. Chaussy ◽  
D. Pelloquin
Keyword(s):  
Specific Heat ◽  
Ac Susceptibility

Reduction in the Thermal Conductivity of Thermoelectric Titanium Oxide by Introduction of Planar Defects

2009 ◽  
Vol 1218 ◽  
Author(s):  
Shunta Harada ◽  
Katsushi Tanaka ◽  
Haruyuki Inui
Keyword(s):  
Thermal Conductivity ◽  
Titanium Oxide ◽  
Hot Pressing ◽  
Oxygen Deficiency ◽  
Nominal Composition ◽  
Titanium Oxides ◽  
X Ray Diffraction ◽  
Planar Defects ◽  
Magnéli Phase ◽  
Magneli Phase

AbstractThermoelectric properties of a homologous series of Magnéli phase titanium oxides TinO2n-1 (n = 2, 3..) have been investigated. Dense polycrystalline specimens with nominal composition of TiO2-x (x = 0.10, 0.20) have been prepared by conventional hot-pressing. X-ray diffraction analysis has revealed that prepared specimens are slightly reduced during hot-pressing. Electrical conduction is of n-type for all prepared titanium oxides and electrical resistivity and absolute values of Seebeck coefficient decrease with increasing oxygen deficiency. The carrier concentration of Magnéli phase titanium oxide increases with increasing oxygen deficiency. Lattice thermal conductivity decreases with increasing oxygen deficiency by more than 60% at room temperature and 40% at 773K compared to TiO2, which can be due to the presence of dense planar defects. The largest thermoelectric figure of merit Z, 1.6×10-4 K-1 at 773K, was obtained in TiO1.90 hot pressed specimen.

Dependence of the glass transition temperature on heating and cooling rate

1974 ◽  
Vol 78 (26) ◽  
pp. 2673-2677 ◽  
Author(s):  
Cornelius T. Moynihan ◽  
Allan J. Easteal ◽  
James Wilder ◽  
Joseph Tucker
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Cooling Rate ◽  
Heating And Cooling

Bridging Precipitate Microstructure and Mechanical Hardness of Nickel-Based Superalloy Through Artificial Neural Network Model

2020 ◽  
Author(s):  
Yangping Li ◽  
Yangyi Liu ◽  
Sihua Luo ◽  
Zi Wang ◽  
Ke Wang ◽  
...  
Keyword(s):  
Neural Network ◽  
Mechanical Properties ◽  
Artificial Neural Network ◽  
Cooling Rate ◽  
Volume Fraction ◽  
Sem Images ◽  
Mechanical Hardness ◽  
Nickel Based Superalloy ◽  
Artificial Neural ◽  
Artificial Neural Network Ann

Abstract The attractive mechanical properties of nickel-based superalloys primarily arise from an assembly of γ′ precipitates with desirable size, volume fraction, morphology and spatial distribution. In addition, the solutioning cooling rate after super solvus heat treatment is critical for controlling the features of γ′ precipitates. However, the correlation between these multidimensional parameters and mechanical hardness has not been well established to date. Scanning electron microscope (SEM) images with different γ′ precipitates were investigated in this study, and artificial neural network (ANN) method was used to build a microstructure-mechanical property model. The critical step in this work is to extract different microstructural features from hundreds of SEM images. In order to improve the accuracy of prediction, the cooling rate was also considered as the input. In this work, the methodology was proved to be capable of bridging microstructural features and mechanical properties under the inspiration of material genome spirit.

scholarly journals White Dwarf Seismology at the Université de Montréal

1993 ◽  
Vol 139 ◽  
pp. 120-120
Author(s):  
G. Fontaine ◽  
P. Brassard ◽  
P. Bergeron ◽  
F. Wesemael
Keyword(s):  
Specific Heat ◽  
Cooling Rate ◽  
Internal Structure ◽  
White Dwarf ◽  
White Dwarfs ◽  
Period Change ◽  
Core Material ◽  
The Core ◽  
Core Composition ◽  
Chemical Stratification

Over the last several years, we have developed a comprehensive program aimed at better understanding the properties of pulsating DA white dwarfs (or ZZ Ceti stars). These stars are nonradial pulsators of the g-type, and their study can lead to inferences about their internal structure. For instance, the period spectrum of a white dwarf is most sensitive to its vertical chemical stratification, and one of the major goals of white dwarf seismology is to determine the thickness of the hydrogen layer that sits on top of a star. This can be done, in principle, by comparing in detail theoretical period spectra with the periods of the observed excited modes. Likewise, because the cooling rate of a white dwarf is very sensitive to the specific heat of its core material (and hence to its composition), it is possible to infer the core composition through measurements and interpretations of rates of period change in a pulsator.

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