scholarly journals Realization of structural transformation for the enhancement of magnetic and magneto capacitance effect in BiFeO3–CoFe2O4 ceramics for energy storage application

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Muniyandi Muneeswaran ◽  
Ali Akbari-Fakhrabadi ◽  
Miguel Angel Gracia-Pinilla ◽  
Juliano C. Denardin ◽  
Nambi Venkatesan Giridharan
Keyword(s):  
Energy Density ◽  
Phonon Scattering ◽  
Structural Phase ◽  
Solid State Reaction Method ◽  
Maximum Efficiency ◽  
Response Analysis ◽  
Reitveld Refinement ◽  
Capacitance Effect ◽  
Raman Modes ◽  
Polar Symmetry

AbstractIn this study, (1 − x) BFO-xCFO (CFO, x = 0.00, 0.05, 0.10 and 0.30) ceramics were synthesized by a solid-state reaction method; their compositions were driven by structural, microstructural, vibrational, electrical, magnetic properties; their enhanced magneto capacitance (MC) effect have also been carried out. Reitveld refinement studies of X-ray diffraction data shows composition-driven structural phase transformation from rhombohedral (R3c) to tetragonal (P4mm). Two phonon scattering Raman modes were observed for the higher wavenumber which supports the crystal structural transition in the BFO-CFO. Ferroelectric polarization shows that the polarization increased with increasing CFO concentration, which describes the changes of the polar symmetry of the crystal structure from rhombohedral (R3c) to tetragonal (P4mm). In Further, the maximum efficiency of energy density (η = 68.65%), reversible energy density of 0.138 J/cm3 and the strong magneto capacitance was observed in 0.9BFO-0.1CFO, which belongs to the morphotropic phase boundary (MPB) region near to the BiFeO3-rich region. The magnetic response analysis has shown, the saturation magnetization (Ms) values of 83 emu/gm and 139 emu/gm for pure CFO and 0.7BFO-0.3CFO composite, respectively, and their magnetic behaviours were also confirmed with Arrott–Belov–Kouvel (ABK) plot.

scholarly journals Structural modification and evaluation of Dielectric, Magnetic and Ferroelectric Properties o f Nd- modified BiFeO3– PbTiO3 Multiferroic Ceramics

2021 ◽  
Author(s):  
Manoj Baloni ◽  
Ram Chhavi Sharma ◽  
Hemant Singh ◽  
Bushra Khan ◽  
Manoj K Singh ◽  
...  
Keyword(s):  
Ferroelectric Properties ◽  
Structural Phase ◽  
Hysteresis Loops ◽  
Xrd Analysis ◽  
Solid State Reaction Method ◽  
Rhombohedral Structure ◽  
Linear Behavior ◽  
Ferro Magnetic ◽  
Ion Substitution ◽  
Raman Modes

Abstract 0.9Bi1 − xNdxFeO3 – 0.1PbTiO3 solid solution where x = 0.05, 0.10, 0.15 and 0.20 were success fully synthesized by the standard solid-state reaction method. The effect of Nd3+ion substitution on structural, micro structural, ferroelectric, magnetic, dielectric and magneto-electric properties of 0.9BiFeO3-0.1PbTiO3 have been investigated. The XRD analysis for the samples under study revealed distorted rhombohedral structure with R3C space group. 0.9Bi1 − xNdxFeO3 – 0.1PbTiO3 where x = 0.05, 0.10, 0.15 and 0.20 i.e.(BNFPT)x compounds crystallised as single-phase materials with the same structure as the parent BiFeO3 compound.. The SEM study revealed the uniform grain scattering for all prepared samples. Raman spectroscopy showed disappearance of some Raman modes indicated a structural phase transition with substitution of Nd dopants at Bi site and also confirmed the distorted rhombohedral perovskite structure of (BNFPT)x compounds with R3c symmetry. Dielectric measurements showed magnetoelectric coupling around Neel temperature in all the samples and also improved dielectric properties with addition of dopants in BiFeO3(BFO) compound. All the prepared samples exhibit weak ferro-magnetic character at room temperature. However, the variation in linear behavior and enhancement in magnetization is found at 5 K which shows gradual increase in remnant magnetization from 0.00785 emu/g to 0.37513 emu/g with increase in Nd doping for all (BNFPT)x samples. Nd doping reduces leakage current by three orders of magnitude, from 10− 4 to 10− 7. Ferroelectric study revealed the pinning effect in hysteresis loops with low remnant polarization.

Magnetic Properties and Magnetostriction of ZnxNi1-x MnSb Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 1715-1718
Author(s):  
S.K. Ren ◽  
G.B. Ji ◽  
Song Ling Huang ◽  
Q.Q. Cao ◽  
Feng Ming Zhang ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Curie Temperature ◽  
Structural Phase ◽  
Solid State Reaction Method ◽  
Experimental Result ◽  
Xrd Pattern ◽  
Zn Concentration ◽  
Magnetostriction Coefficient ◽  
The Relationship ◽  
Curie Temperature Tc

We have investigated the magnetic properties and magnetostriction of ZnxNi1-xMnSb compounds prepared by solid state reaction method. It is found that for x less than 0.6 the magnetization of ZnxNi1-xMnSb almost remains unchanged. However, when x is larger than 0.6 the magnetization starts to drop linearly. Experimental result indicates that at low Zn concentrations, x < 0.7, the Curie temperature (TC) decreases with increasing Zn concentration x. However, when x > 0.7, the Curie temperature increases distinctly with increasing x. The Zn concentrartion dependence of magnetostrictive ceofficient is also studied. The experimental curve shows that when x < 0.6 the value of magnetostriction coefficient for ZnxNi1-xMnSb decreases linearly with the increasing Zn concentration x. However, when x is above 0.6, the magnetostrictive ceofficient raises distinctly. By analyzing the XRD pattern, the structures of the materials are examined and the relationship between the properties and the structures are discussed. A structural phase transition is observed. It has been indicated that the structure plays an important role in the magnetic and magnetostrictive properties of the system.

Electron–Phonon Interaction Model and Prediction of Thermal Energy Transport in SOI Transistor

2007 ◽  
Vol 7 (11) ◽  
pp. 4094-4100 ◽  
Author(s):  
Jae Sik Jin ◽  
Joon Sik Lee
Keyword(s):  
Energy Density ◽  
Group Velocity ◽  
Phonon Scattering ◽  
Phonon Dispersion ◽  
Dispersion Model ◽  
Hot Spot ◽  
Interaction Model ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Electron Phonon Scattering

An electron–phonon interaction model is proposed and applied to thermal transport in semiconductors at micro/nanoscales. The high electron energy induced by the electric field in a transistor is transferred to the phonon system through electron–phonon interaction in the high field region of the transistor. Due to this fact, a hot spot occurs, which is much smaller than the phonon mean free path in the Si-layer. The full phonon dispersion model based on the Boltzmann transport equation (BTE) with the relaxation time approximation is applied for the interactions among different phonon branches and different phonon frequencies. The Joule heating by the electron–phonon scattering is modeled through the intervalley and intravalley processes for silicon by introducing average electron energy. The simulation results are compared with those obtained by the full phonon dispersion model which treats the electron–phonon scattering as a volumetric heat source. The comparison shows that the peak temperature in the hot spot region is considerably higher and more localized than the previous results. The thermal characteristics of each phonon mode are useful to explain the above phenomena. The optical mode phonons of negligible group velocity obtain the highest energy density from electrons, and resides in the hot spot region without any contribution to heat transport, which results in a higher temperature in that region. Since the acoustic phonons with low group velocity show the higher energy density after electron–phonon scattering, they induce more localized heating near the hot spot region. The ballistic features are strongly observed when phonon–phonon scattering rates are lower than 4 × 1010 s−1.

scholarly journals Influence of Mn2+ doping on structural phase transformation and optical property of TiO2:Mn2+ nanoparticles

2019 ◽  
Vol 29 (3) ◽  
Author(s):  
Trinh Thi Loan ◽  
Nguyen Ngoc Long
Keyword(s):  
Tio2 Nanoparticles ◽  
Doping Concentration ◽  
Sol Gel ◽  
Structural Phase ◽  
Photoluminescence Spectra ◽  
X Ray Diffraction ◽  
Defect States ◽  
Ion Doping ◽  
Raman Modes ◽  
Synthesized Materials

Titanium dioxide (TiO2) nanoparticles with various Mn2+-doping concentration (from 0 to 12 mol%) were successfully synthesized by the sol–gel method using titanium tetrachloride (TiCl4), and manganese II chloride tetrahydrate (MnCl2.4H2O)  as precursors. The phase and crystallinity of the synthesized materials were investigated by powder X-ray diffraction pattern and Raman spectroscopy. Diffuse reflection and photoluminescence spectra were taken to investigate the absorption and emission characteristics of the synthesized samples. The results show that the anatase and rutile phases existed simultaneously in all the doping TiO2 nanoparticles and the Mn2+ doping enhances anatase-rutile transformation. The Mn2+ contents did not affect the lattice of TiO2 host, but affected positions of its Raman modes. The optical band gap of the TiO2:Mn2+ decreases with the increase of doping concentration. Photoluminescence spectra of the TiO2:Mn2+ nanopaticles showed the transitions between the bands, the transitions related to defect states and the Mn2+ ion doping leads to quenching the photoluminescence.

Thermomechanical Behavior of GaN Nanowires During Tensile Loading and Unloading

2012 ◽  
Author(s):  
Kwangsub Jung ◽  
Maenghyo Cho ◽  
Min Zhou
Keyword(s):  
Thermal Conductivity ◽  
Phase Transformations ◽  
Phonon Scattering ◽  
Structural Phase ◽  
Tensile Loading ◽  
Reverse Transformation ◽  
Tetragonal Structure ◽  
Gan Nanowires ◽  
Forward Transformation ◽  
Dynamics Simulations

Structural phase transformations from wurtzite to a graphite-like phase and from wurzite to a tetragonal phase in ZnO and GaN nanowires under tensile loading cause significant changes in thermal conductivity. Molecular dynamics simulations are carried out to investigate the effect of deformation and the phase transformations on the thermal conductivity of [0001]-oriented GaN nanowires. The calculation of conductivity at each state of the nanowires is based on the equilibrium Green-Kubo approach with quantum correction. Under tensile loading, initially wurtzite-structured wires transform into a tetragonal structure, causing the thermal conductivity to decrease as the strain increases. Unloading of the transformed wires is associated with a reverse transformation from the tetragonal structure to the wurtzite structure. Opposite to what is observed during the forward transformation during loading, the thermal conductivity increases as the strain decreases in the unloading process. However, during the reverse transformation, the nanowires consist of both tetragonal regions and wurtzite-structured regions. Such intermediate states are not observed during the loading process. Phonon scattering at the interfaces between the wurtzite and tetragonal regions during unloading causes the thermal conductivity of the nanowires to be lower compared with that during loading.

Electron–Phonon Interaction Model and Prediction of Thermal Energy Transport in SOI Transistor

2007 ◽  
Vol 7 (11) ◽  
pp. 4094-4100
Author(s):  
Jae Sik Jin ◽  
Joon Sik Lee
Keyword(s):  
Energy Density ◽  
Group Velocity ◽  
Phonon Scattering ◽  
Phonon Dispersion ◽  
Dispersion Model ◽  
Hot Spot ◽  
Interaction Model ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Electron Phonon Scattering

An electron–phonon interaction model is proposed and applied to thermal transport in semiconductors at micro/nanoscales. The high electron energy induced by the electric field in a transistor is transferred to the phonon system through electron–phonon interaction in the high field region of the transistor. Due to this fact, a hot spot occurs, which is much smaller than the phonon mean free path in the Si-layer. The full phonon dispersion model based on the Boltzmann transport equation (BTE) with the relaxation time approximation is applied for the interactions among different phonon branches and different phonon frequencies. The Joule heating by the electron–phonon scattering is modeled through the intervalley and intravalley processes for silicon by introducing average electron energy. The simulation results are compared with those obtained by the full phonon dispersion model which treats the electron–phonon scattering as a volumetric heat source. The comparison shows that the peak temperature in the hot spot region is considerably higher and more localized than the previous results. The thermal characteristics of each phonon mode are useful to explain the above phenomena. The optical mode phonons of negligible group velocity obtain the highest energy density from electrons, and resides in the hot spot region without any contribution to heat transport, which results in a higher temperature in that region. Since the acoustic phonons with low group velocity show the higher energy density after electron–phonon scattering, they induce more localized heating near the hot spot region. The ballistic features are strongly observed when phonon–phonon scattering rates are lower than 4 × 1010 s−1.

scholarly journals Space charges and negative capacitance effect in organic light-emitting diodes by transient current response analysis

RSC Advances ◽  
2017 ◽  
Vol 7 (80) ◽  
pp. 50598-50602 ◽  
Author(s):  
Min Guan ◽  
Litao Niu ◽  
Yang Zhang ◽  
Xingfang Liu ◽  
Yiyang Li ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Transient Current ◽  
Organic Light Emitting Diodes ◽  
Response Analysis ◽  
Current Response ◽  
Negative Capacitance ◽  
Light Emitting ◽  
Organic Light ◽  
Capacitance Effect ◽  
First Time

Space charge capacitance and the physical mechanism of negative capacitance in organic light-emitting diodes (OLEDs) by transient current response analysis are investigated for the first time.

scholarly journals Structural phase variations in high-entropy alloy at irradiation by pulsed electron beam

2021 ◽  
Vol 64 (11) ◽  
pp. 846-854
Author(s):  
Yu. F. Ivanov ◽  
V. E. Gromov ◽  
S. V. Konovalov ◽  
Yu. A. Shlyarova ◽  
S. V. Vorob'ev
Keyword(s):  
Surface Layer ◽  
Electron Beam ◽  
Energy Density ◽  
High Velocity ◽  
Structural Phase ◽  
Dendritic Structure ◽  
Cell Junctions ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Wire Arc Additive Manufacturing

The high-entropy alloy (HEA) of Al - Co - Cr - Fe - Ni system of nonequiatomic composition is obtained by the technology of wire-arc additive manufacturing (WAAM) in atmosphere of pure nitrogen. By the methods of modern physical materials science it is shown that in the initial state the alloy has dendritic structure indicating nonhomogeneous distribution of alloying elements. It is a multiphase material whose main phases are Al3NCr3C2 , (Ni, Co)3Al4 . Nonadimensional particles (Ni, Co)3Al4 of cubic shape are located along interfaces of submicron phases Al3Ni and Cr3C2 . The HEA irradiation by pulsed electron beams with energy density Es = 10 + 30 J/cm2, pulse duration of 50 is, frequency of 3 Hz and pulse number of 3 leads to high-velocity melting and subsequent crystallization of surface layer. If Es = 10 J/cm2, no failure of dendritic crystallization structure happens. Interdendritic spaces are enriched in chemical elements Al, Ni and Fe, and dendrites themselves - in chromium atoms. The most liquating element of the alloy is Al, the least one is Co. If Es = 20 J/cm2, a nanocrystalline structure is formed in the layer 15 inn thick in bulk of grains. Size of crystallization cells amounts to 100 - 200 nm, size of inclusions in cell junctions is 20 - 25 nm, and along cell boundaries it is 10 - 15 nm. Cells of high-velocity crystallization are enriched in Al and Ni. The Co atoms are homogeneously distributed along the surface layer volume. The most liquating element is Cr, the least liquating one is Co. The increase in energy density of electron beam to 30 J/cm2 doesn't lead to substantial (as compared to Es = 20 J/cm2 ) variations in surface layer structure. The irradiation mode (Es = 20 J/cm2, 50 is, 3 pulses, 0.3 Hz) is detected that allows formation of the surface layer with the highest level of homogeneity of chemical element distribution in the alloy.

Effect of Cr-N codoping on structural phase transition, Raman modes, and optical properties of TiO2 nanoparticles

2018 ◽  
Vol 123 (16) ◽  
pp. 161541 ◽  
Author(s):  
G. Hassnain Jaffari ◽  
Adnan Tahir ◽  
Naveed Zafar Ali ◽  
Awais Ali ◽  
Umar S. Qurashi
Keyword(s):  
Phase Transition ◽  
Optical Properties ◽  
Tio2 Nanoparticles ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Raman Modes
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