EFFECT OF BARIUM ON DIELECTRIC, FERROELECTRIC, IMPEDANCE AND ELECTRICAL MODULUS PROPERTIES OF Bi0.5Na0.5TiO3 CERAMICS

2011 ◽  
Vol 25 (22) ◽  
pp. 2931-2948 ◽  
Author(s):  
K. SAMBASIVA RAO ◽  
K. CH. VARADA RAJULU ◽  
B. TILAK
Keyword(s):  
Power Law ◽  
Single Phase ◽  
Low Frequency ◽  
Rhombohedral Structure ◽  
Conductivity Spectrum ◽  
X Ray ◽  
Impedance Spectroscopy Study ◽  
Conventional Sintering ◽  
Phase Compound ◽  
Jonscher’S Power Law

Perovskite structured ferroelectric ( Na 1/2 Bi 1/2)0.945 Ba 0.055 TiO 3 (BNBT-5.5) material has been synthesized by the conventional sintering technique. X-ray analysis on the material showed a single phase compound with rhombohedral structure with lattice parameters a = 3.89 Åand α = 89.893 Å. Frequency and temperature dependence of dielectric permittivity, impedance, modulus and conductivity have been performed in the frequency and temperature range 45 Hz–5 MHz and 35–595°C, respectively. The observed low frequency dielectric dispersion (LFDD) in the material could be explained by Jonschers power law and evaluated activation energies at different temperature regions. Impedance spectroscopy study showed the presence of both bulk and grain boundary effects in the materials. The ac conductivity spectrum obeyed the Jonscher's power law. Modulus analysis indicated the possibility of hopping mechanism for electrical process in the system.

Impedance Spectroscopy Study of LiTaO3 Powder Synthesized via Sol-Gel Method

2012 ◽  
Vol 545 ◽  
pp. 275-278 ◽  
Author(s):  
Lili Widarti Zainuddin ◽  
Norlida Kamarulzaman
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Sol Gel ◽  
Rhombohedral Structure ◽  
Spectroscopy Study ◽  
X Ray Diffraction ◽  
Gel Method ◽  
X Ray ◽  
Sol Gel Method ◽  
Impedance Spectroscopy Study

A ceramics sample of LiTaO3 was prepared using a sol-gel method. The sample is annealed at 750 °C for 48 hours. X-ray diffraction analysis indicate the formation of single phase, rhombohedral structure. An ac impedance study was used to analyse the conductivity of LiTaO3 at room temperature and at various temperatures.

scholarly journals Influence of Li2CO3 addition on electrical and magnetic properties of Ni0.6Mg0.4Fe2O4

2020 ◽  
Vol 10 (03) ◽  
pp. 2050003
Author(s):  
M. R. Hassan ◽  
M. T. Islam ◽  
M. N. I. Khan
Keyword(s):  
Magnetic Properties ◽  
Single Phase ◽  
Low Frequency ◽  
Solid State Reaction Method ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrical And Magnetic Properties ◽  
Frequency Regime ◽  
Xrd Patterns

In this research, influence of adding Li2CO3 (at 0%, 2%, 4%, 6%) on electrical and magnetic properties of [Formula: see text][Formula: see text]Fe2O4 (with 60% Ni and 40% Mg) ferrite has been studied. The samples are prepared by solid state reaction method and sintered at 1300∘C for 6[Formula: see text]h. X-ray diffraction (XRD) patterns show the samples belong to single-phase cubic structure without any impurity phase. The magnetic properties (saturation magnetization and coercivity) of the samples have been investigated by VSM and found that the higher concentration of Li2CO3 reduces the hysteresis loss. DC resistivity increases with Li2CO3 contents whereas it decreases initially and then becomes constant at lower value with temperature which indicates that the studied samples are semiconductor. The dielectric dispersion occurs at a low-frequency regime and the loss peaks are formed in a higher frequency regime, which are due to the presence of resonance between applied frequency and hopping frequency of charge carriers. Notably, the loss peaks are shifted to the lower frequency with Li2CO3 additions.

Laser Sintering of Greens Compacts of MoSi2

2006 ◽  
Vol 530-531 ◽  
pp. 364-368
Author(s):  
G. de Vasconcelos ◽  
R. Cesar Maia ◽  
Carlos Alberto Alves Cairo ◽  
R. Riva ◽  
N.A.S. Rodrigues ◽  
...  
Keyword(s):  
Cross Section ◽  
Laser Processing ◽  
Single Phase ◽  
Sintering Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heating Source ◽  
Scanning Electron Microcopy ◽  
Conventional Sintering ◽  
Reduced Time

In this study, the results of the feasibility of sintering green compacts of metallic powder of MoSi2 by a CO2 laser beam as the heating source has been investigated. The main advantage of this technique is to promote a dense material in a reduced time when compared to the conventional sintering process. In order to sintering the MoSi2 powder, green compacts of 6mm of diameter and 1.6mm thickness were produced in a steel die in a uniaxial press at 100MPa and after, isostatic pressed at 350MPa. The micrograph of the samples exposed to the laser radiation performed by scanning electron microcopy (SEM) reveal the efficiency of the sintering process and the X-ray diffraction of the powders confirmed the presence of single phase after and before laser processing. The average microhardness of these compacts reached near to 700 Hv0.2 in the cross section to the laser irradiation, indicating the all sintering of the green compact.

scholarly journals Spectral Index Versus Frequency and Models for the Continua of AGN and QSOs

1989 ◽  
Vol 134 ◽  
pp. 201-202
Author(s):  
Wayne A. Stein
Keyword(s):  
Accretion Disk ◽  
Spectral Index ◽  
Power Law ◽  
Spectral Distribution ◽  
Secondary Electron ◽  
Low Frequency ◽  
Spectral Indices ◽  
Ultraviolet Continuum ◽  
Electron Synchrotron ◽  
X Ray

The observed spectral index as a function of frequency of QSO continua must be explained in models. It is generally increasing (F(ν) ∝ ν−α, α increasing) with higher frequency in the infrared (downward curvature). The visual to ultraviolet continuum has been shown to be a broken power law with F(ν) ∝ ν−0.5 at low frequency and a break to larger α at νo ∼ 3×1015 Hz. X-ray observations frequently exhibit a flat continuum with α < 1. One prominent example is 3C273 for which α1–3μm → 2, αvis ∼ 0.5 and αx ∼ 0.5. These spectral indices arise naturally in Secondary Electron Synchrotron Self-Compton (SESSC) models. Some accretion disk models approach these spectral indices for the visual-ultraviolet portion of the spectral distribution.

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.

Electronic and Magnetic States of Iron Ions in (Bi1-xSrx)FeO3-y Multiferroic Perovskites

2009 ◽  
Vol 152-153 ◽  
pp. 89-92 ◽  
Author(s):  
V. M. Cherepanov ◽  
V. S. Pokatilov
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Ceramic Technology ◽  
Rhombohedral Structure ◽  
X Ray Diffraction ◽  
Strontium Content ◽  
X Ray ◽  
Similar Dependence ◽  
Magnetic States ◽  
57Fe Isotope

The mixed perovskites (Bi1-xSrx)FeO3-y (x = 0.07, 0.14, 0.25 and 0.50) were studied by 57Fe Mössbauer spectroscopy in the temperature range 87–700 K. The samples were prepared by conventional ceramic technology with 10% 57Fe isotope enrichment. X–ray diffraction measurements showed that the samples were single-phase and had a rhombohedral structure at x = 0.07 and a cubic one at x = 0.14-0.50. As the strontium content x increases, the Neel temperature TN(x) increases from 640 K (x = 0) to 670 K (x = 0.25) and then decreases to 637 K (x = 0.5). The similar dependence on x was found for the hyperfine field values B(x) at T = 87 K. The experimental Mössbauer spectra are satisfactorily described by three to four Fe3+ states with the room temperature isomer shift values in the range 0.17-0.43 mm/s, which correspond to the iron sites with 4, 5 and 6 oxygen neighbours.

scholarly journals Engineered Layer-Stacked Interfaces Inside Aurivillius-Type Layered Oxides Enables Superior Ferroelectric Property

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 710 ◽  
Author(s):  
Shujie Sun ◽  
Xiaofeng Yin
Keyword(s):  
Single Phase ◽  
Ferroelectric Properties ◽  
Solid State Reactions ◽  
Layered Oxides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Phase Compound ◽  
Layer Sample ◽  
Lattice Distortions

Layer engineering with different layer numbers inside Aurivillius-type layered structure, similar to interface engineering in heterojunctions or superlattices, can give rise to excellent physical properties due to the correlated layer-stacked interfaces of two different layer phases with different strain states. In this work, using the solid-state reactions from Aurivillius-type Bi3TiNbO9 (2-layer) and Bi4Ti3O12 (3-layer) ferroelectric powder mixtures, single-phase compound of Bi7Ti4NbO21 with an intergrowth structure of 2-layer and 3-layer perovskite slabs sandwiched between the Bi-O layers was synthesized and the effects of this layer-engineered strategy on the structure, Raman-vibration and ferroelectric properties were systematically investigated. The mostly-ordered intergrowth phase was observed clearly by utilizing X-ray diffraction and advanced electron micro-techniques. Uniformly dispersions and collaborative vibrations of Ti and Nb ions in the layer-engineered Bi7Ti4NbO21 were demonstrated. Remarkably, dielectric and ferroelectric properties were also recorded and an enhanced ferroelectric response was found in the layer-engineered mixed-layer sample with high ferroelectric Curie temperature, compared with the homogeneous 2-layer and 3-layer samples. Analyses of the Raman spectra and atomic structures confirmed that the performance improvement of the layer-engineered sample is intrinsic to the correlated layer-stacked interfaces inside the Aurivillius-type layered oxides, arising from strain-induced lattice distortions at the interfaces.

Effect of Annealing Temperatures on Formation of Na0.5Bi0.5TiO3 and (Na0.5Bi0.5)0.96Ba0.04TiO3 Ceramics Prepared via Sol Gel Method

2012 ◽  
Vol 501 ◽  
pp. 76-80
Author(s):  
Mohammad Hafizuddin Haji Jumali ◽  
Siti Mariam Mohamad ◽  
Rozidawati Awang ◽  
Muhammad Yahaya ◽  
Mohd Riduan M. Said ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Glacial Acetic Acid ◽  
Single Phase ◽  
Sol Gel ◽  
Rhombohedral Structure ◽  
Gel Method ◽  
X Ray ◽  
Sol Gel Method ◽  
Annealing Temperatures ◽  
Ba Substitution

The effect of annealing temperatures on the formation of pure perovskite Na0.5Bi0.5TiO3 (NBT) based ceramics prepared by sol gel method has been investigated. The NBT sol was prepared using NaCH3COO, C6H9BiO6 and Ti(C4H9)4 with 2-methoxyethanol and glacial acetic acid were used as solvents. The BaTiO3 sol was synthesized using C4H6BaO4 and Ti(C4H9)4 with acetic acid and ethanolamine were used as solvents. The (Na0.5Bi0.5)0.96Ba0.04TiO3 (NBBT) sol was prepared by mixing appropriate amount of NBT and BaTiO3 sols. Then NBT and NBBT sols were dried at 200oC for 24 h, ground and subsequently annealed at temperatures ranging from 440oC – 640oC for 5 min. Formation of NBT and NBBT ceramics was examined using XRD technique. X-ray diffractograms reveal that the NBT ceramic with rhombohedral structure starts to form at 540oC and complete crystallization is achieved at 620oC. Addition of 4vol% of BaTiO3 sols drastically reduces the crystallization temperature of NBBT ceramic to 460oC and a pure single phase ceramic is achieved at 520oC. Despite retaining the same rhombohedral structure, the NBBT exhibits lattice parameters expansion indicating a successful Ba substitution which is also confirms by the absence of BaTiO3 peaks in the diffractograms. Both ceramics exhibit great thermal stability with additional increment in annealing temperatures.

Electrical and Magnetic Properties of (BiLi)1/2(FeV)1/2O3

2011 ◽  
Vol 110-116 ◽  
pp. 5437-5441
Author(s):  
Subrat K. Barik ◽  
Sudipta K. Bera
Keyword(s):  
Single Phase ◽  
Complex Impedance ◽  
Polycrystalline Sample ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Solid State Reaction Technique ◽  
X Ray ◽  
Electrical And Magnetic Properties ◽  
Phase Compound ◽  
Different Temperatures

The polycrystalline sample of (BiLi) 1/2 (FeV) 1/2O3 was prepared by a high-temperature solid-state reaction technique. A preliminary X-ray structural analysis exhibited the formation of single-phase compound with an orthorhombic structure. Detailed studies of electrical properties of the compound, investigated in a wide frequency range (1kHz-1MHz) at different temperatures by complex impedance spectroscopy (CIS) technique, showed that these properties of the material are strongly dependent on frequency and temperature. Ac conductivity is found to obey the Johnscher’s law. The M-H curve shows the presence of ferromagnetism in the studied compound.

scholarly journals On the frequency correlations of low-frequency QPOs with kilohertz QPOs in accreting millisecond X-ray pulsars

2019 ◽  
Vol 490 (4) ◽  
pp. 5270-5284 ◽  
Author(s):  
Marieke van Doesburgh ◽  
Michiel van der Klis
Keyword(s):  
Black Hole ◽  
Power Law ◽  
Equations Of State ◽  
Low Frequency ◽  
Data Sets ◽  
Periodic Oscillations ◽  
X Ray ◽  
Frame Dragging ◽  
Low Mass ◽  
X Ray Binaries

ABSTRACT We investigate frequency correlations of low frequency (LF, &lt;80 Hz) and kHz quasi-periodic oscillations (QPOs) using the complete RXTE data sets on six accreting millisecond X-ray pulsars (AMXPs) and compare them to those of non-pulsating neutron star (NS) low-mass X-ray binaries with known spin. For the AMXPs SAX J1808.4−3658 and XTE J1807−294, we find frequency-correlation power-law indices that, surprisingly, are significantly lower than in the non-pulsars, and consistent with the relativistic precession model (RPM) prediction of 2.0 appropriate to test-particle orbital and Lense–Thirring precession frequencies. As previously reported, power-law normalizations are significantly higher in these AMXPs than in the non-pulsating sources, leading to requirements on the NS specific moment of inertia in this model that cannot be satisfied with realistic equations of state. At least two other AMXPs show frequency correlations inconsistent with those of SAX J1808.4−3658 and XTE J1807−294, and possibly similar to those of the non-pulsating sources; for two AMXPs no conclusions could be drawn. We discuss these results in the context of a model that has had success in black hole (BH) systems involving a torus-like hot inner flow precessing due to (prograde) frame dragging, and a scenario in which additional (retrograde) magnetic and classical precession torques not present in BH systems are also considered. We show that a combination of these interpretations may accommodate our results.

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