scholarly journals Effects of molar ratio on dielectric, ferroelectric and magnetic properties of Ni0.5Zn0.5Fe2O4-BaTiO3 composite ceramics

2020 ◽  
Vol 14 (2) ◽  
pp. 91-101
Author(s):  
Xiaodong Luo ◽  
Hong Wang ◽  
Rongli Gao ◽  
Xinliang Li ◽  
Jing Zhang ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Magnetic Properties ◽  
Sol Gel ◽  
Low Frequency ◽  
Molar Ratio ◽  
Composite Ceramics ◽  
Molar Ratios ◽  
Magnetoelectric Composite ◽  
Relaxation Polarization ◽  
Two Peaks

Ni0.5Zn0.5Fe2O4-BaTiO3 (NZFO-BTO) magnetoelectric composite ceramics with different molar ratios (mNZFO:mBTO = 1:1.5, 1.5:1 and 2:1, defined as N1B1.5, N1.5B1 and N2B1, respectively) were prepared successfully by using a joint hydrothermal method and sol-gel technique and sintering at 1000 ?C. Meanwhile, the dielectric, ferroelectric and magnetic properties of the composites were investigated. The presence of bi-phase structure in the composites was verified with X-ray diffraction analyses. The scanning electron microscopy images and energy dispersion spectrum results confirmed that the bulk-like grains (2 to 5 ?m) and spherelike grains (_0.5 ?m) could be attributed to NZFO and BTO, respectively. The dielectric constant and loss increased with increasing NZFO/BTO molar ratio because the carrier concentration of NZFO is higher than that of BTO. Thus, the dielectric constant of the N2B1 ceramics is more than 7800 at low frequency of 100Hz and room temperature, while only less than 2000 for the N1B1.5 composite. Two peaks can be observed in the temperature dependence of the dielectric constant curves. One is near 120 ?C, which corresponds to the Curie temperature of BTO, while the other peak occurs at about 320 ?C, corresponding to the relaxation polarization. The remanent polarization increases with increasing the content of ferroelectric BTO. The maximum value at 1 kHz was observed for the N1B1.5 sample and it is larger than 4.5 ?C/cm2, while the minimal value was obtained for the N2B1 composite and is only 1.2 ?C/cm2. Magnetic properties were also measured and it was observed that magnetization increases with increasing the molar ratio. The largest saturation magnetization has the N2B1 composite (_51.74 emu/g) due to the larger concentration of NZFO phase. However, the sample N1B1.5 shows the largest coercive field due to the highest interface interaction. This study provides guidelines for the fabrication of NZFO-BTO magnetoelectric composite ceramics.

scholarly journals Influence of molar ratio on dielectric, ferroelectric and magnetic properties of Co0.5Mg0.5Fe2O4/Ba0.85Sr0.15TiO3 composite ceramics

2019 ◽  
Vol 13 (3) ◽  
pp. 257-268
Author(s):  
Lang Bai ◽  
Rongli Gao ◽  
Qingmei Zhang ◽  
Zhiyi Xu ◽  
Zhenhua Wang ◽  
...  
Keyword(s):  
Sol Gel ◽  
Peak Position ◽  
Relaxation Peak ◽  
Molar Ratio ◽  
Composite Ceramics ◽  
Molar Ratios ◽  
Mean Grain Size ◽  
Higher Temperature ◽  
Two Phases ◽  
Two Peaks

In the present work, Co0.5Mg0.5Fe2O4/Ba0.85Sr0.15TiO3 (CMFO/BST) composite ceramics with different molar ratios (1:1, 1:2, 1:4, 1:6 and 1:8) were prepared by sol-gel method and sintered at 1150?C. The effects of molar ratio on the structure, dielectric and multiferroic properties were comparatively studied. The results indicate that all the synthesized composites mainly show bi-phase structure except slight presence of impurity phases. The surface of the specimens is relatively dense and the mean grain size is about 2 ?m. It decreases at first and then increases with the increased molar ratio. The dielectric constant shows decreased trend with increasing the molar ratio, while the dielectric loss presents the opposite behaviour. With the increase of molar ratio, the height of the relaxation peak decreases while the peak position shifts to higher temperature range. The relaxation peak evolves gradually from one to two peaks. The residual polarization increases with voltage but decreases with frequency. The maximal polarization of 1.28 ?C/cm2 is obtained in the specimen with the molar ratio of 1:8, due to the largest concentration of ferroelectric phase BST. The magnetization shows abnormal behaviour with the change in molar ratio. The largest saturation and remnant magnetization are 20.89 and 12.66 emu/g, respectively when the molar ratio is 1:2 due to the stronger interface interaction effect between the two phases.

scholarly journals A comparative study on the dielectric and multiferroic properties of Co0.5Zn0.5Fe2O4/Ba0.8Sr0.2TiO3 composite ceramics

2019 ◽  
Vol 13 (4) ◽  
pp. 349-359
Author(s):  
Xiaofeng Qin ◽  
Ruicheng Xu ◽  
Heng Wu ◽  
Gao Rongli ◽  
Zhenhua Wang ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Leakage Current ◽  
Ferroelectric Phase ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Secondary Phase ◽  
Molar Ratio ◽  
Intensity Increase ◽  
Composite Ceramics ◽  
Multiferroic Properties

Co0.5Zn0.5Fe2O4/Ba0.8Sr0.2TiO3 (CZFO/BST) composite ceramics with different molar ratios (1:3, 1:2, 1:1, 2:1 and 3:1) were prepared by combining chemical co-precipitation and sol-gel method. Effects of molar ratio on the microstructure, dielectric and multiferroic properties were investigated. The formation of the individual phases and the composites was confirmed by XRD results and small amount of secondary phase (Ba2Fe2Ti4O13) was observed. The grain sizes of magnetic (CZFO) and ferroelectric phase (BST), measured by SEM, were about 5 ?m and 0.5 ?m, respectively. The sample with molar ratio (1:2) has the largest dielectric constant, while the sample with molar ratio (3:1) shows the lowest dielectric constant. A distinct loss peak can be observed for all the samples. Both the peak position and peak intensity increase with the frequency, indicating relaxation polarization process generated by space charge or interface polarization. The ceramics with molar ratio (1:1) shows the smallest leakage current (~ 10?7 A/cm at 1.5 kV/cm), while the leakage current (~ 10?5 A/cm at 1.5 kV/cm) of the sample with molar ratio (3:1) is the largest. The ferroelectric hysteresis loop is not apparent due to the low Curie temperature of the ferroelectric phase, but the sample with molar ratio (2:1) shows the best ferroelectric properties. It was found that with the increase of CZFO content, the values of saturation (Ms) and remnant (Mr) magnetization increase at first and then decrease. The sample with molar ratio (3:1) has the maximum Ms value (about 50.34 emu/g), while the sample with molar ratio (1:2) shows the minimal Mr value (about 0.46 emu/g). This anomalous magnetic property is induced by the interface interaction between the two phases.

Sol-gel synthesis and characterization of Ag nanoparticles in ZrO2 thin films

2009 ◽  
Vol 24 (8) ◽  
pp. 2541-2546 ◽  
Author(s):  
Eisuke Yokoyama ◽  
Hironobu Sakata ◽  
Moriaki Wakaki
Keyword(s):  
Thin Films ◽  
Sol Gel ◽  
Composite Films ◽  
Dip Coating ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Silver Surface ◽  
Molar Ratios ◽  
Sol Gel Synthesis

ZrO2 thin films containing silver nanoparticles were prepared using the sol-gel method with Ag to Zr molar ratios [Ag]/[Zr] = 0.11, 0.25, 0.43, 0.67, 1.00, 1.50, and 2.33. After dip coating on glass substrate, coated films were annealed at 200 and 300 °C in air. X-ray diffraction peaks corresponding to crystalline Ag were observed, but a specific peak corresponding to ZrO2 was not observed. At the molar ratio [Ag]/[Zr] = 0.25, the particle size of Ag distributed broadly centered at 17 nm for an annealing temperature of 200 °C and at 25 nm for 300 °C. The films annealed in air at 200 °C showed an absorption band centered at 450 nm because of the silver surface plasmon resonance, whereas films heated at 300 °C in air caused a red shift of the absorption to 500 nm. The absorption peak was analyzed using the effective dielectric function of Ag-ZrO2 composite films modeled with the Maxwell-Garnett expression.

Preparation and Magnetic Properties of Fe@SiO2 Soft Magnetic Composites

2020 ◽  
Vol 993 ◽  
pp. 638-645
Author(s):  
Shuai Feng ◽  
Yan An ◽  
Zong Xiang Wang ◽  
Kai Sun ◽  
Run Hua Fan
Keyword(s):  
Magnetic Properties ◽  
Sol Gel ◽  
Core Loss ◽  
Low Frequency ◽  
Magnetic Flux Density ◽  
Iron Particles ◽  
Soft Magnetic ◽  
Magnetic Composites ◽  
Insulating Layer ◽  
Iron Powders

In this work, the insulating SiO2 was coated successfully on the surface of reduced iron particles by a sol-gel method to decrease the core loss at low frequency. The scanning electron microscope images and elements analysis confirm that the surface of iron powders particles were covered by a thin insulating layer in the form of uniform core-shell structure. The samples were annealed at 400 °C in N2 atmosphere to obtain better magnetic properties. The annealed SMCs with 10 mL/h dropping rate of TEOS have optimum magnetic properties with low core loss Ps of 280.89 W/kg and high saturation magnetic flux density Bs of 1.038 T at 1000 Hz.

scholarly journals Photocatalytic Improvement under Visible Light inTiO2Nanoparticles by Carbon Nanotube Incorporation

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Mathana Wongaree ◽  
Siriluk Chiarakorn ◽  
Surawut Chuangchote
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Sol Gel ◽  
Multiwall Carbon Nanotubes ◽  
High Specific Surface Area ◽  
Molar Ratio ◽  
Molar Ratios ◽  
Calcination Temperatures ◽  
Photocatalytic Activities ◽  
Multiwall Carbon

Photocatalytic activity ofTiO2nanoparticles was successfully enhanced by addition of multiwall carbon nanotubes (MWCNT) to make CNT/TiO2nanocomposites by sol-gel method at ambient temperature. CNT treated by HNO3 : H2SO4treatment (1 : 3 v/v) was mixed withTiO2nanoparticles at various molar ratios and calcination temperatures. The optimal molar ratio of CNT : TiO2was found at 0.05 : 1 by weight. The optimal calcination condition was 400°C for 3 h. From the results, the photocatalytic activities of CNT/TiO2nanocomposites were determined by the decolorization of 1 × 10−5 M methylene blue (MB) under visible light. CNT/TiO2nanocomposites could enhance the photocatalytic activity and showed faster for the degradation of MB with only 90 min. The degradation efficiency of the MB solution with CNT/TiO2nanocomposite achieved 70% which was higher than that with pristineTiO2(22%). This could be explained that CNT preventsTiO2from its agglomeration which could further enhance electron transfer in the composites. In addition, CNT/TiO2nanocomposites had high specific surface area (202 m2/g) which is very promising for utilization as a photocatalyst for environmental applications.

The Influences of Different Precursors on Morphology of Bi3TiNbO9 Powders Prepared by a Sol-Gel Method

2013 ◽  
Vol 815 ◽  
pp. 765-772 ◽  
Author(s):  
Zuo Dong Li ◽  
Dan Liu
Keyword(s):  
Ethylene Glycol ◽  
Chemical Method ◽  
Single Phase ◽  
Perovskite Phase ◽  
Sol Gel ◽  
Particle Morphology ◽  
Deionized Water ◽  
Molar Ratio ◽  
Molar Ratios ◽  
Baking Process

Bi3NbTiO9 (BNTO) powders were synthesized by a sol-gel chemical method using niobium oxalates, bismuth nitrate and tetra-n-butyl-titanate as starting materials. In order to determine the influence of the molar ratio of the deionized water to ethylene glycol on the particle morphology and crystallization, different molar ratios, the deionized water/ethylene glycol, were chosen to prepare BNTO powders. Single phase BNTO powders could be obtained at a calcinations temperature of 600°C. Moreover, the possible formation mechanism of BNTO powders was also proposed in this paper. In the baking process, perovskite phase BNTO was formed via a reaction between oxides and bismuth niobium.

Synthesis and Magnetic Properties of FePt Nanoparticles with Hard Nonmagnetic Shells

2007 ◽  
Vol 7 (1) ◽  
pp. 350-355 ◽  
Author(s):  
Shishou Kang ◽  
Shifan Shi ◽  
G. X. Miao ◽  
Zhiyong Jia ◽  
David E. Nikles ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Crystallographic Orientation ◽  
Sol Gel ◽  
Molar Ratio ◽  
Core Shell ◽  
Fept Nanoparticles ◽  
Shell Nanoparticles ◽  
Spherical Core ◽  
Size And Morphology ◽  
Core Shell Nanoparticles

Chemically synthesized FePt nanoparticles were coated with nonmagnetic SiO2 and MnO shells by sol–gel and polyol processes. TEM images show that the FePt/SiO2 nanoparticles exhibit a thick spherical shell. The size and morphology of the MnO shell can be controlled by changing the reaction temperature, the molar ratio of surfactants/Mn(acac)2, and/or the concentration of precursor. The morphology of the MnO shell can be either spherical-like or cubic-like, depending on whether the molar ratio of surfactants/Mn(acac)2 is less than or larger than 2. From XRD measurements, the spherical core/shell nanoparticles exhibit 3D random crystallographic orientation, while the cubic core/shell nanoparticles prefer (200) texture. The magnetic moment of FePt particles can be enhanced by coating with SiO2 and MnO shells. Furthermore, the agglomeration of FePt particles upon the thermal annealing can be significantly inhibited with SiO2 and MnO shells.

Characterization and Photocatalytic Activity of Composite La-TiO2/ITO Thin-Film Electrodes

2009 ◽  
Vol 79-82 ◽  
pp. 899-902
Author(s):  
Ming Yi Chang ◽  
Wei Fu Wang ◽  
Yung Hsu Hsieh ◽  
Chen Yu Chang
Keyword(s):  
Sol Gel ◽  
Dip Coating ◽  
Molar Ratio ◽  
Xrd Pattern ◽  
Molar Ratios ◽  
Sem Image ◽  
Uniform Particles ◽  
Spherical Structure ◽  
Coating Method ◽  
Dip Coating Method

The different molar ratios of La/Ti (0.025, 0.050, 0.075 and 0.100) photocatalytic electrodes use in this study were synthesized by sol-gel method and dip-coating method. The XRD pattern of TiO2/ITO presents only anatase phases, [1] but for La-TiO2/ITO presents both anatase and rutile phases. The SEM image of the La-TiO2/ITO showed particles of regular shapes with smaller size (＜10nm) compared to the TiO2/ITO, which presented uniform particles of spherical structure and larger size （20nm）.The La-TiO2/ITO photocatalytic electrode with molar ratio 0.050 shows the best ability both on the absorbtion and photocatalytsis. Applied potential 2.0V would effectively increase the photoelectrocatlaytic activity under visible light irradiation.

Optical properties of ZnO nanoparticles synthesized by varying the sodium hydroxide to zinc acetate molar ratios using a Sol-Gel process

Open Physics ◽  
2011 ◽  
Vol 9 (5) ◽  
Author(s):  
Francis Dejene ◽  
Abdub Ali ◽  
Hendrik Swart ◽  
Reinhardt Botha ◽  
Kittesa Roro ◽  
...  
Keyword(s):  
Zno Nanoparticles ◽  
Sol Gel ◽  
Visible Region ◽  
Blue Emission ◽  
Molar Ratio ◽  
Broad Emission Band ◽  
Photoluminescence Intensity ◽  
Molar Ratios ◽  
Quantum Confinement Effects ◽  
Sol Gel Process

AbstractMaterial property dependence on the OH−/Zn2+ molar ratio of the precursor was investigated by varying the amount of NaOH during synthesis of ZnO. It was necessary to control the water content and temperature of the mixture to ensure the reproducibility. It was observed that the structural properties, particle size, photoluminescence intensity and wavelength of maximum intensity were influenced by the molar ratio of the precursor. The XRD spectra for ZnO nanoparticles show the entire peaks corresponding to the various planes of wurtzite ZnO, indicating a single phase. UV measurements show the absorption that comes from the ZnO nanoparticles in visible region. The absorption edge of these ZnO nanoparticles are shifted to higher energies and the determined band gap energies are blue shifted as the OH−/Zn2 molar ration increases, due to the quantum confinement effects. The photoluminescence characterization of the ZnO nanostructures exhibited a broad emission band centred at green (600 nm) region for all molar ratios except for OH−/Zn2+ = 1.7 where a second blue emission around 468 nm was also observed. The photoluminescence properties of ZnO nanoparticles were largely determined by the size and surface properties of the nanoparticles.

Electrical investigations of holmium-doped BaTiO3 derived from sol-gel combustion

2010 ◽  
Vol 25 (6) ◽  
pp. 1057-1063 ◽  
Author(s):  
Marin Cernea ◽  
Carmen Galassi ◽  
Bogdan S. Vasile ◽  
Paul Ganea ◽  
Roxana Radu ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Loss ◽  
Remanent Polarization ◽  
Sol Gel ◽  
Combustion Method ◽  
Molar Ratio ◽  
Gel Combustion ◽  
Tan Δ ◽  
Gel Combustion Method ◽  
Structure And Microstructure

Holmium-doped BaTiO3 with composition Ba0.97Ho0.03TiO3 was prepared by sol-gel combustion method. A molar ratio of citrate/nitrate (CA/NO3− = 1.3) was used to prepare nanopowders of (Ba,Ho)TiO3. The structure and microstructure of (Ba,Ho)TiO3 powders and ceramics were investigated. The ceramics exhibit a dielectric constant of about 4400 and dielectric loss (tan δ = 0.267) at 10 Hz, and at the Curie temperature (Tc = 132 °C). The remanent polarization and the coercive field of Ba0.97Ho0.03TiO3 ceramics, at 1 kHz, were Pr = 6 μC/cm2 and EC = 0.75 kV/cm. The dielectric and ferroelectric behavior of the holmium-doped BaTiO3 is influenced by the amphoteric character of Ho3+ ions.

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