IMPEDANCE SPECTROSCOPIC STUDIES OF BiFeO3-Pb(ZrTi)O3 NANOCOMPOSITES

2009 ◽  
Vol 23 (22) ◽  
pp. 2655-2664 ◽  
Author(s):  
R. N. P. CHOUDHARY ◽  
SUBRAT K. BARIK ◽  
R. S. KATIYAR
Keyword(s):  
Complex Impedance ◽  
Signal Amplitude ◽  
Dissipation Factor ◽  
Spectroscopic Studies ◽  
Solid State Reaction Technique ◽  
Dielectric Parameters ◽  
Air Atmosphere ◽  
Universal Power Law ◽  
Wide Range ◽  
Electrical Data

BiFeO 3- Pb ( ZrTi ) O 3 [i.e., ( Bi 1-x Pb x)( Fe 1-x Zr 0.6x Ti 0.4x) O 3 (x = 0.15, 0.25, 0.40, 0.50)] nanocomposites were synthesized using mechanical activation followed by a solid-state reaction technique. The dielectric parameters (capacitance, dissipation factor D, impedance Z and phase angle Φ) of all the samples were measured in a wide range of frequencies (1 kHz–1 MHz) and temperatures (300–630 K) in air atmosphere using an impedance analyzer with low signal amplitude of 500 mV. Electrical properties of the compounds were studied using a complex impedance spectroscopy (CIS) technique. The frequency dependence of electrical data was analyzed in the framework of conductivity and modulus formalisms. AC conductivity spectrum obeys Jonscher's universal power law.

IMPEDANCE CHARACTERISTICS OF La3/2Bi3/2Fe5O12 CERAMICS

2009 ◽  
Vol 23 (26) ◽  
pp. 5179-5189
Author(s):  
K. JAWAHAR ◽  
BANARJI BEHERA ◽  
R. N. P. CHOUDHARY
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Solid State ◽  
Room Temperature ◽  
Complex Impedance ◽  
Conductivity Spectrum ◽  
High Temperature Region ◽  
Solid State Reaction Technique ◽  
Impedance Characteristics ◽  
Universal Power Law

Polycrystalline La 3/2 Bi 3/2 Fe 5 O 12 (LBIO) compound was prepared by a high-temperature solid-state reaction technique. The complex impedance of LBIO was measured over a wide temperature (i.e., room temperature to 500°C) and frequencies (i.e., 102–106 Hz) ranges. This study takes advantage of plotting ac data simultaneously in the form of impedance and modulus spectroscopic plots and obey non-Debye type of relaxation process. The Nyquist's plot showed the presence of grain effects in the material at high temperature. The ac conductivity spectrum was found to obey Jonscher's universal power law. The dc conductivity was found to increase with rise in temperature. The activation energy of the compound was found to be 0.24 and 0.51 eV in the low and high-temperature region, respectively, for conduction process.

scholarly journals Studies of Structural, Dielectric and Electrical Characteristics of Complex Perovskite: Pb(Co1/3Mn1/3W1/3)O3

2020 ◽  
Vol 64 (2) ◽  
Author(s):  
P.Ganga Raju Achary ◽  
Deeptimayee Khatua ◽  
Santosh Parida ◽  
Sujit Dehury ◽  
R.N.P. Choudhary
Keyword(s):  
Complex Impedance ◽  
Orthorhombic Crystal ◽  
Solid State Reaction Technique ◽  
Dielectric Parameters ◽  
Orthorhombic Crystal Structure ◽  
Sem Image ◽  
Multiple Phase ◽  
Nyquist Plots ◽  
Diffusivity Parameter ◽  
Frequency Temperature

A lead-based multiferroic, Pb(Co1/3Mn1/3W1/3)O3, was synthesized by using a high-temperature solid-state reaction technique. Based on X-ray structural analysis, an orthorhombic crystal structure has been suggested for the material. The scanning electron microscopy (SEM) image exhibits a morphology with and uniform grains distribution. A detailed study of variation of dielectric parameters with frequency and temperature exhibits that Pb(Co1/3Mn1/3W1/3)O3 undergoes multiple phase transitions; first transition (Tc1) appeared at 436K (ferroelastic to ferroelectric) whereas second transition ( Tc2) appeared at 504K ( ferroelectric to paraelectric). Since the peaks of dielectric constant are broader and diffused, a diffusivity parameter (γ) has been estimated to the amount of disordering in the material structure.The contribution of grain,grain boundaries and electrode effect in electrical conduction mechanisim can be understood by frequency-temperature dependence of resistive characterestics using CIS spectroscopy (complex impedance spectroscopy). Impedance or Nyquist plots were modeled with an equivalent circuit having capacitance, resistance and related parameters. Studies of transport properties, ac conductivity, electrical modulus and magneto-electric (ME) effect of the materialis reported in this communication.

Porphyrin-Catalyzed Oxidation of N-Substituted Tetrahydroisoquinolines to Dihydroisoquinolones

Synlett ◽  
2021 ◽  
Author(s):  
Ao Li ◽  
Bin Pan ◽  
Mu Chao ◽  
Na Wang ◽  
Yu-Long Li ◽  
...  
Keyword(s):  
Visible Light ◽  
Room Temperature ◽  
Air Atmosphere ◽  
Wide Range ◽  
Convenient Route ◽  
Catalyzed Oxidation

A visible-light-induced direct α-oxygenation of N-substituted tetrahydroisoquinoline derivatives has been successfully developed. Metalloporphyrin (ZnTPP) has been identified as an effective and inexpensive photocatalyst for this transformation with a wide range of substrates. This protocol provides a convenient route to afford the desired products in moderate to good yields at room temperature under air atmosphere.

scholarly journals Preparation and Characterization of Transparent Polyimide Nanocomposite Films with Potential Applications as Spacecraft Antenna Substrates with Low Dielectric Features and Good Sustainability in Atomic-Oxygen Environments

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1886
Author(s):  
Yan Zhang ◽  
Bo-han Wu ◽  
Han-li Wang ◽  
Hao Wu ◽  
Yuan-cheng An ◽  
...  
Keyword(s):  
Atomic Oxygen ◽  
Composite Films ◽  
Dissipation Factor ◽  
Low Earth Orbit ◽  
Nanocomposite Films ◽  
Dielectric Parameters ◽  
Low Dielectric ◽  
Aerospace Applications ◽  
Optically Transparent ◽  
Order Of Magnitude

Optically transparent polyimide (PI) films with good dielectric properties and long-term sustainability in atomic-oxygen (AO) environments have been highly desired as antenna substrates in low earth orbit (LEO) aerospace applications. However, PI substrates with low dielectric constant (low-Dk), low dielectric dissipation factor (low-Df) and high AO resistance have rarely been reported due to the difficulties in achieving both high AO survivability and good dielectric parameters simultaneously. In the present work, an intrinsically low-Dk and low-Df optically transparent PI film matrix, poly[4,4′-(hexafluoroisopropylidene)diphthalic anhydride-co-2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane] (6FPI) was combined with a nanocage trisilanolphenyl polyhedral oligomeric silsesquioxane (TSP-POSS) additive in order to afford novel organic–inorganic nanocomposite films with enhanced AO-resistant properties and reduced dielectric parameters. The derived 6FPI/POSS films exhibited the Dk and Df values as low as 2.52 and 0.006 at the frequency of 1 MHz, respectively. Meanwhile, the composite films showed good AO resistance with the erosion yield as low as 4.0 × 10−25 cm3/atom at the exposure flux of 4.02 × 1020 atom/cm2, which decreased by nearly one order of magnitude compared with the value of 3.0 × 10−24 cm3/atom of the standard PI-ref Kapton® film.

scholarly journals Fiber Optical Hydrogen Sensor Based on WO3-Pd2Pt-Pt Nanocomposite Films

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 128
Author(s):  
Jixiang Dai ◽  
Yi Li ◽  
Hongbo Ruan ◽  
Zhuang Ye ◽  
Nianyao Chai ◽  
...  
Keyword(s):  
Optical Power ◽  
Single Mode ◽  
Hydrogen Sensor ◽  
Single Mode Fiber ◽  
Nanocomposite Films ◽  
Electric Signal ◽  
Hydrogen Sensing ◽  
Air Atmosphere ◽  
Sensing Material ◽  
Wide Range

In this paper, WO3-Pd2Pt-Pt nanocomposite films were deposited on a single mode fiber as the hydrogen sensing material, which changes its reflectivity under different hydrogen concentration. The reflectivity variation was probed and converted to an electric signal by a pair of balanced InGaAs photoelectric detectors. In addition, the performance of the WO3-Pd2Pt-Pt composite film was investigated under different optical powers, and the irrigating power was optimized at 5 mW. With the irrigation of this optical power, the hydrogen sensitive film exhibits quick response toward 100 ppm hydrogen in air atmosphere at a room temperature of 25 °C. The experimental results demonstrate a high resolution at 5 parts per million (ppm) within a wide range from 100 to 5000 ppm in air. This simple and compact sensing system can detect hydrogen concentrations far below the explosion limit and provide early alert for hydrogen leakage, showing great potential in hydrogen-related applications.

scholarly journals Structure-Property Correlation in Ir Transparent Zinc Sulphide (Zns) Ceramics Under Chemical Vapour Deposited & Hot Iso-Statically Pressed Conditions

2019 ◽  
Vol 3 (2) ◽  
Keyword(s):  
Grain Size ◽  
Hot Isostatic Pressing ◽  
Chemical Vapour ◽  
Complex Impedance ◽  
Ac Impedance ◽  
Spectroscopic Studies ◽  
Structure Property ◽  
Frequency Range ◽  
Equivalent Circuit Analysis ◽  
Isostatic Pressing

IR Transparent ZnS ceramics processed through chemical vapour deposition were subjected to Hot Isostatic pressing and the samples in both the conditions were characterized by XRD, microstructure and high temperature impedance spectroscopic studies for the dielectric and electrical properties. Both the samples have shown cubic sphalerite phase with enhanced orientation along (111) plane as a result of hot isostatic pressing as revealed by XRD.HIP treatment to ZnS facilitated the enhancement of the homogeneity of microstructure and enhancement in the grain size from 10μm to 50μm. The electrical behavior of both the samples was investigated by AC impedance spectroscopy in the frequency range 1Hz to 1MHz from RT to 500°C in dry air. HIP has resulted in a significant increase in the dielectric constant, which can be attributed to the increase in homogeneity and the grain size. Further, the complex impedance plots exhibited two impedance semicircles identified in the frequency range is explained by the grain and grain boundary effects. An equivalent-circuit analysis of AC impedance spectra based on the brick-layer model was performed. Activation energies obtained from the conductivity plots indicates an Arrhenius type thermally activated process.

scholarly journals Installation for measuring the dielectric anisotropy of liquid crystals at low frequencies by the bridge method with constant displacement

2021 ◽  
Vol 1198 (1) ◽  
pp. 012006
Author(s):  
S V Kalashnikov ◽  
N A Romanov ◽  
A V Nomoev
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Internal Resistance ◽  
Dielectric Anisotropy ◽  
Dielectric Parameters ◽  
Low Frequencies ◽  
Offset Voltage ◽  
Wide Range ◽  
Ac Current ◽  
Constant Displacement

Abstract Installation designed to measure the dielectric anisotropy in laboratory studies of liquid crystal polymer films is described. The installation operates on the principle of a balanced alternating current (AC) bridge, allowing the application of a direct external current (bias) to the liquid crystal cell. The internal resistance of the direct current (DC) source, which affects the equilibrium condition of the bridge, is compensated. The frequency of the AC current feeding the bridge and the offset voltage of the cell is regulated within a wide range, which makes it possible to study various functional dependences of the dielectric parameters of liquid crystals and their modifiers.Introduction

scholarly journals Dielectric properties of Li doped Ni-Zn ferrite

2018 ◽  
Vol 16 (36) ◽  
pp. 140-152 ◽  
Author(s):  
Nasma A. Jaber
Keyword(s):  
Sol Gel ◽  
Dissipation Factor ◽  
X Ray Diffraction ◽  
Lithium Ions ◽  
Sem Images ◽  
Dielectric Parameters ◽  
Ferrite Material ◽  
Zn Ferrite ◽  
Auto Combustion ◽  
Experimental Values

Lithium doped Nickel-Zinc ferrite material with chemical formula Ni0.9−2x Zn0.1LixFe2+xO4, where x is the ratio of lithium ions Li+ (x = 0, 0.01, 0.02, 0.03 and 0.04) prepared by using sol-gel auto combustion technique. X-ray diffraction results showed that the material have pure cubic spinal structure with space group Fd-3m. The experimental values of the lattice constant (aexp) were decreased from 8.39 to 8.35 nm with doped Li ions. It was found that the decreasing of the crystallite size with addition of lithium ions concentration. The radius of tetrahedral (rtet) and octahedral (roct) site were computed from cation distribution. SEM images have been taken to show the morphology of compound. The dielectric parameters [dissipation factor (Df), the dielectric constant (Ԑ') and a.c. conductivity (ζac)] of spinal ferrite nano-powder have been measured. The dielectric parameters as a function of concentration have been studied for ferrite synthesis. The saturation of magnetization (Ms), remiensis (Mr) and coersivity (Hc) were found from hysteresis loop. The Ms and Hc varied from 36.47 to 66.15 emu/gm and 103 to 133 Oe for ferrite synthesis, respectively.

scholarly journals Methods development for diffraction and spectroscopy studies of metalloenzymes at X-ray free-electron lasers

2014 ◽  
Vol 369 (1647) ◽  
pp. 20130590 ◽  
Author(s):  
Jan Kern ◽  
Johan Hattne ◽  
Rosalie Tran ◽  
Roberto Alonso-Mori ◽  
Hartawan Laksmono ◽  
...  
Keyword(s):  
Free Electron ◽  
Water Oxidation ◽  
Spectroscopic Studies ◽  
Free Electron Lasers ◽  
Software Suite ◽  
X Ray ◽  
Methods Development ◽  
Wide Range ◽  
Linac Coherent Light Source ◽  
Spectroscopy Studies

X-ray free-electron lasers (XFELs) open up new possibilities for X-ray crystallographic and spectroscopic studies of radiation-sensitive biological samples under close to physiological conditions. To facilitate these new X-ray sources, tailored experimental methods and data-processing protocols have to be developed. The highly radiation-sensitive photosystem II (PSII) protein complex is a prime target for XFEL experiments aiming to study the mechanism of light-induced water oxidation taking place at a Mn cluster in this complex. We developed a set of tools for the study of PSII at XFELs, including a new liquid jet based on electrofocusing, an energy dispersive von Hamos X-ray emission spectrometer for the hard X-ray range and a high-throughput soft X-ray spectrometer based on a reflection zone plate. While our immediate focus is on PSII, the methods we describe here are applicable to a wide range of metalloenzymes. These experimental developments were complemented by a new software suite, cctbx.xfel . This software suite allows for near-real-time monitoring of the experimental parameters and detector signals and the detailed analysis of the diffraction and spectroscopy data collected by us at the Linac Coherent Light Source, taking into account the specific characteristics of data measured at an XFEL.

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