ANALYSIS OF FLUCTUATION CONDUCTIVITY OF GRANULAR Gd1-xPrxBa2Cu3O7-δ SUPERCONDUCTOR

2010 ◽  
Vol 24 (24) ◽  
pp. 2465-2475 ◽  
Author(s):  
CRISTIANO SANTOS LOPES ◽  
LINCOLN BRUM DE LEITE GUSMÃO PINHEIRO ◽  
MARCELO DOS SANTOS ◽  
ALCIONE ROBERTO JURELO ◽  
ROSÂNGELA MENEGOTTO COSTA ◽  
...  
Keyword(s):  
Critical Temperature ◽  
Electrical Transport ◽  
Single Phase ◽  
Transition Width ◽  
X Ray Diffraction ◽  
Solid State Reaction Technique ◽  
Fluctuation Conductivity ◽  
X Ray ◽  
Zero Resistance ◽  
Resistance State

Single phase polycrystalline Gd 1-x Pr x Ba 2 Cu 3 O 7-δ (0 ≤ x ≤ 0.10) samples have been prepared by standard solid state reaction technique and characterized by SEM, X-ray diffraction and electrical transport experiments. The samples were granular and homogeneous. It was observed that the critical temperature decreases and that the transition width increases with increasing Pr doping. Systematic measurements of fluctuation conductivity are reported. Special attention is taken above the critical temperature, where Gaussian and critical regimes are observed. Below the critical temperature, on approaching the zero resistance state, our results show a power-law behavior consistent with a phase transition from a paracoherent to a coherent state of the granular array.

scholarly journals Study of multiferroic properties of Bi2Fe2WO9 ceramic for device application

2016 ◽  
Vol 06 (03) ◽  
pp. 1650023 ◽  
Author(s):  
Jyoshna Rout ◽  
R. N. P. Choudhary
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
X Ray Diffraction ◽  
Electrical Parameters ◽  
Orthorhombic Crystal ◽  
Solid State Reaction Technique ◽  
X Ray ◽  
Universal Power Law ◽  
Phase Compound ◽  
Comprehensive Study

The Bi2Fe2WO9 ceramic was prepared using a standard solid-state reaction technique. Preliminary analysis of X-ray diffraction pattern revealed the formation of single-phase compound with orthorhombic crystal symmetry. The surface morphology of the material captured using scanning electron microscope (SEM) exhibits formation of a densely packed microstructure. Comprehensive study of dielectric properties showed two anomalies at 200[Formula: see text]C and 450[Formula: see text]C: first one may be related to magnetic whereas second one may be related to ferroelectric phase transition. The field dependent magnetic study of the material shows the existence of small remnant magnetization ([Formula: see text]) of 0.052[Formula: see text]em[Formula: see text]/g at room temperature. The existence of magneto-electric (ME) coupling coefficient along with above properties confirms multi-ferroic characteristics of the compound. Selected range temperature and frequency dependent electrical parameters (impedance, modulus, conductivity) of the compound shows that electric properties are correlated to its microstructure. Detailed studies of frequency dependence of ac conductivity suggest that the material obeys Jonscher’s universal power law.

DIELECTRIC, FERROELECTRIC, PIEZOELECTRIC AND IMPEDANCE STUDY OF LEAD-FREE CERAMIC: SrBi4Ti3.975Zr0.025O15

2012 ◽  
Vol 02 (04) ◽  
pp. 1250023 ◽  
Author(s):  
B. MAMATHA ◽  
P. SARAH
Keyword(s):  
Single Phase ◽  
Electromechanical Coupling ◽  
Xrd Analysis ◽  
Coupling Coefficients ◽  
X Ray Diffraction ◽  
Solid State Reaction Technique ◽  
Debye Relaxation ◽  
X Ray ◽  
Resonance Frequencies ◽  
Spectroscopy Studies

Polycrystalline SrBi4Ti3.975Zr0.025O15 (SBTZ) was prepared using solid-state reaction technique. SBTZ was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis indicated the formation of a single-phase orthorhombic structure. Particle size was found using SEM. The dielectric, ferroelectric, piezoelectric, modulus and impedance spectroscopy studies on SBTZ were investigated in the frequency range 1 Hz–1 MHz from room temperature (RT) to 600°C. Piezoelectric charge and electromechanical coupling coefficients were calculated from resonance and anti-resonance frequencies. Impedance and modulus plots were used as tools to analyze the sample behavior as a function of frequency. Cole–Cole plots showed a non-Debye relaxation. Conductivity measurements were performed on SBTZ.

STUDY OF STRUCTURAL, ELECTRICAL TRANSPORT AND MAGNETIC PROPERTIES IN La1-xAgxMnO3 COMPOUNDS

2004 ◽  
Vol 18 (05n06) ◽  
pp. 221-231 ◽  
Author(s):  
MANORANJAN KAR ◽  
S. RAVI
Keyword(s):  
Magnetic Field ◽  
Electrical Transport ◽  
Single Phase ◽  
Ac Susceptibility ◽  
X Ray Diffraction ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Phase Form ◽  
X Ray ◽  
Maximum Value

X-ray diffraction, electrical resistivity and ac susceptibility measurements have been carried out on La 1-x Ag x MnO 3 compounds for x=0.05 to 0.30. These samples are found to be in single phase form with [Formula: see text] space group and with typical lattice parameters a=b=5.524Å and c=13.349Å for x=0.05 sample. The Mn–O–Mn bond angles and variance, σ2 are found to increase with doping. Metal-insulator transitions in the temperature range 254 to 259 K have been observed. These materials exhibit paramagnetic to ferromagnetic transitions in the vicinity of metal-insulator transition temperatures. The paramagnetic susceptibility could be analyzed using Curie–Weiss law. All the above samples exhibit colossal magneto-resistivity and its maximum value is found to be 73% for x=0.15 sample at 50 kOe magnetic field.

REBa2ZrO5.5 (RE = La, Ce, Eu, and Yb): Synthesis, characterization, and their potential use as substrates for YBa2Cu3O7–δ superconductors

1997 ◽  
Vol 12 (11) ◽  
pp. 2976-2980 ◽  
Author(s):  
R. Jose ◽  
Asha M. John ◽  
J. Kurian ◽  
P. K. Sajith ◽  
J. Koshy
Keyword(s):  
Single Phase ◽  
Detrimental Effect ◽  
Solid State Reaction Method ◽  
Dielectric Constants ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resistivity Measurements ◽  
New Class ◽  
Zero Resistance ◽  
Potential Use

A new class of complex perovskites REBa2ZrO5.5 (where RE = La, Ce, Eu, and Yb) have been synthesized and sintered as single phase materials by the solid state reaction method. The structure of these materials was studied by x-ray diffraction, and all of them were found to be isostructural, having a cubic perovskite structure. X-ray diffraction and resistivity measurements have shown that there is no detectable chemical reaction between YBa2Cu3O7–delta; and REBa2ZrO5.5 even under severe heat treatment at 950 °C, and that the addition of REBa2ZrO5.5 up to 20 vol.% in YBa2Cu3O7–δ shows no detrimental effect on the superconducting properties of YBa2Cu3O7-δ. Dielectric constants and loss factors are in the range suitable for their use as substrates for microwave applications. Thick films of YBa2Cu3O7–δ fabricated on polycrystalline REBa2ZrO5.5 substrates gave a zero resistance transition temperature Tc(0) ∼ 92 K, indicating the suitability of these materials as substrates for YBa2Cu3O7–δ.

STUDY OF Y1-xCaxBa2-yLayCu3Oz CARRIER UN-COMPENSATING SYSTEM

2009 ◽  
Vol 23 (25) ◽  
pp. 5039-5047
Author(s):  
W. T. JIN ◽  
S. J. HAO ◽  
H. ZHANG ◽  
Y. ZHAO
Keyword(s):  
Critical Temperature ◽  
Carrier Concentration ◽  
Single Phase ◽  
Magnetization Measurement ◽  
The Self ◽  
Careful Study ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bond Lengths

The single-phase samples of Y 0.9 Ca 0.1 Ba 2-y La y Cu 3 O z and Y1-x Ca x Ba 1.5 La 0.5 Cu 3 O z were synthesized with both x and y from 0 to 0.5, respectively. Structural and superconducting properties have been investigated by X-ray diffraction, Rietveld refinement, and DC magnetization measurement, respectively. Different from the self-compensating compound of Y 1-x Ca x Ba 2-x La x Cu 3 O z, carriers in these two systems of Y1-x Ca x Ba 2-y La y Cu 3 O z are not compensated as x ≠ y. By careful study of the chemical bond lengths related to Cu (2)– O plane and Cu (1)– O chain, it is demonstrated that the critical temperature (Tc) changes monotonously with the bond lengths of Cu (1)– O (4) and Cu (2)– O (4). The analysis demonstrates that crystalline structure is one of the important factors to high-Tc superconductivity, and its influence is independent of the carrier concentration.

SUPERCONDUCTIVITY AND STRUCTURES OF MBa2Cu3O7−x (WITH M = Y, Eu AND Yb) OXIDES

1988 ◽  
Vol 02 (06) ◽  
pp. 1407-1410 ◽  
Author(s):  
M. N. KHAN ◽  
S. Al-DALLAL ◽  
A. MEMON
Keyword(s):  
Tetragonal Phase ◽  
Perovskite Structure ◽  
Single Phase ◽  
Chemical System ◽  
Temperature Transition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ir Studies ◽  
Zero Resistance ◽  
Orthorhombic Perovskite

We have prepared and observed that the zero-resistance temperature transition occurs in the chemical system MBa 2 Cu 3 O 7 (M = Y, Eu and Yb). The highest T c (ρ = 0) is 92.50 K for Y, 93.80 K for Eu and 96.00 for Yb. The X-ray diffraction analysis shows that these compounds correspond to a single phase which is an orthorhombic perovskite structure. The results of the infrared (IR) studies on orthorhombic and tetragonal phases of some of these compounds provide evidence for the oxygen rearrangement on going from the orthorhombic to the tetragonal phase.

OXIDE SUPERCONDUCTIVITY RESEARCH AT NORTHWESTERN UNIVERSITY

1987 ◽  
Vol 01 (03n04) ◽  
pp. 829-829
Author(s):  
J.B. KETTERSON
Keyword(s):  
Electrical Transport ◽  
Short Review ◽  
Argon Atmosphere ◽  
Oxide Superconductors ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transport Studies ◽  
Wide Range ◽  
Northwestern University ◽  
Zero Resistance

A short review was presented of a wide range of activities involving the high Tc oxide superconductors at the Northwestern University. Calculations of the charge density associated with the d9 shell of the copper atom in the Cu-O planes and the d8 shell of the copper atoms along the Cu-O lines of the unit cell of YBa2Cu3O7 performed by Freeman, Massida and Yu were presented. Results of a detailed study of the pseudoternery phase diagram involving CuO, BaO and YO1.5 were shown which verify the existence of three compounds having the Y:Ba:Cu ratios 123 (the high Tc superconductor), 211 (the so-called green phase) and 132 (a new insulating compound). This work, performed by Mason and coworkers, involved X-ray diffraction, optical spectroscopy, magnetic susceptibility, and electrical transport studies. Transport measurements by Poeppelmeier, Song, Hwu and coworkers on the assembledges YBaSrCu3O7 anf YBa2Cu3O5F2 were reported; no evidence of superconducting behavior at temperatures above 90K was seen in the latter. A detailed study of the magnetic and transport properties of the YBa2−xLaxCu3−xNixO7±δ system was reported. For small Ni concentration (x<0.3) a continuous drop in Tc was observed. For x= 0.4 and 0.5 evidence of two separate transitions, near 75K and 25K, were seen in the resistance (with the resistance going to zero at about 15K); for x=0.7 semiconducting behavior was observed. A continuous drop in the normalized diamagnetic signal was seen with increasing x with the diamagnetic fraction being below 5 % for x=0.7 and above. X-ray diffraction showed a continuous decrease in the orthorhombic fraction and an increase in the tetragonal fraction with increasing x. Results on d.c. magnetron sputtering of thin films on MgO from a stoichiometric 123 target in an argon atmosphere were shown. With proper annealing films with onset temperature of 90K and zero resistance at 68K have been prepared; this work was done by Jin, Lee, Song and coworkers. A brief report on the effect of O-stoichiometry on EPR and susceptibility measurements in the 123 compound performed by Hoffman and coworkers and NMR in the La2−xSrxCuO4 compound by Halpern and coworkers was presented.

Effects of Nano-Sized NiF2 Addition in Bi1.4Pb0.6Sr2Ca2Cu3O10+δ Superconductor

2014 ◽  
Vol 895 ◽  
pp. 87-90 ◽  
Author(s):  
Muhammad Hafiz ◽  
Roslan Abd-Shukor
Keyword(s):  
Electron Microscope ◽  
Critical Temperature ◽  
Scanning Electron Microscope ◽  
Electrical Transport ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Average Size ◽  
20 Nm ◽  
Scanning Electron

The effects of NiF2addition on the superconducting and transport properties of Bi1.4Pb0.6Sr2Ca2Cu3O10+δ(Bi-2223) were studied. Bi-2223 superconductor samples were prepared via conventional nitrate coprecipitation method, and 0.01 wt% - 0.05 wt% of NiF2nanoparticles with average size of 20 nm were added into the samples. The critical temperature (Tc) of each sample was measured by using the four-point probe method. Furthermore, phase formation and the microstructure of the samples were identified using x-ray diffraction method (XRD) and scanning electron microscope (SEM) respectively. The optimumTcwas observed for the sample with 0.04 wt% addition of NiF2. Results of electrical transport measurement are presented.

FLUCTUATION CONDUCTIVITY OF POLYCRYSTALLINE Y1-xTbxBa2Cu3O7-δ SUPERCONDUCTORS

2006 ◽  
Vol 20 (10) ◽  
pp. 565-570 ◽  
Author(s):  
ALCIONE ROBERTO JURELO ◽  
ROBERSON ASSIS DE OLIVEIRA ◽  
ROGÉRIO DOBRZANSKI ◽  
ROSÂNGELA MENEGOTTO COSTA
Keyword(s):  
Electrical Conductivity ◽  
Critical Temperature ◽  
Fluctuation Conductivity ◽  
Strong Disorder ◽  
Low Concentrations ◽  
Zero Resistance ◽  
Resistance State ◽  
High Concentrations ◽  
Two Stages ◽  
Superconducting Fluctuations

We studied the effect of superconducting fluctuations on the electrical conductivity of granular samples of Y 1-x Tb x Ba 2 Cu 3 O 7-δ superconductors. For all samples we observed that the transition proceeds in two stages. Above the critical temperature, the Gaussian and critical regimes were observed, independently of the terbium concentration. In the regime of approach to the zero resistance state, and for low concentrations of terbium, an occurrence of a coherence transition was observed. For high concentrations of Tb , the results show a strong disorder at mesoscopic levels.

Ba2RESbO6 (RE = Nd, Eu and Dy); Characterization and Potential Use as Substrate for Superconducting YBCO Films

1997 ◽  
Vol 11 (20) ◽  
pp. 889-897 ◽  
Author(s):  
P. R. S. Wariar ◽  
J. Kurian ◽  
P. K. Sajith ◽  
T. G. N. Babu ◽  
J. Koshy
Keyword(s):  
Single Phase ◽  
Detrimental Effect ◽  
Diffraction Measurement ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
Complex Perovskite ◽  
X Ray ◽  
Dielectric Constant And Loss ◽  
Zero Resistance ◽  
Potential Use

Perovskite compounds of the general formula, Ba2RESbO6 (where RE = Nd, Eu and Dy) were sintered as single phase materials by standard solid state techniques. These compounds are found to be isostructural and to have a complex perovskite structure as observed by powder X-ray diffraction measurement. No chemical reaction between YBa2Cu3O 7-δ and Ba2RESbO6 compounds, was observed even under severe heat treatment at 950°C, and the addition of Ba2RESbO6 up to 20 vol% in YBa2Cu3O 7-δ, shows no detrimental effect on the superconducting properties of YBa2Cu3O 7-δ. The dielectric constant and loss factor values of sintered specimens, are in a range suitable for their use as substrates for microwave applications. Thick films of YBCO fabricated on highly polished Ba2RESbO6 specimens, gave a superconducting zero resistance transition T c(o) of 92 K, with a critical current density, J c of 2×104 A/cm2 at 77 K.

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