scholarly journals Comprehensive characterization of BiFeO3 powder synthesized by the hydrothermal procedure

2016 ◽  
Vol 10 (4) ◽  
pp. 201-208 ◽  
Author(s):  
Maria Cebela ◽  
Bojan Jankovic ◽  
Radmila Hercigonja ◽  
Miodrag Lukic ◽  
Zorana Dohcevic-Mitrovic ◽  
...  
Keyword(s):  
Single Phase ◽  
Elevated Temperatures ◽  
Bismuth Ferrite ◽  
Hydrothermal Process ◽  
Stacking Faults ◽  
Secondary Phase ◽  
Annealed Powder ◽  
Fe Ions ◽  
Comprehensive Characterization

In this paper, bismuth ferrite (BFO) particles synthesized by controlled hydrothermal process, where the particles of small sizes and with high purity were obtained. Structural analysis showed that non-annealed powder can be perfectly fitted to rhombohedral space group R3c and contains a very small amount of secondary phase, whereas the final product (annealed at 800?C) represents single-phase perovskite powder with high crystallinity. HRTEM analysis confirmed existence of twin stacking faults, which are responsible for enhanced magnetic properties. EPR measurements suggested existence of electrons trapped by vacancies or defects. It has been proposed that existence of Fe3+?OV defect complex could be generated at elevated temperatures followed by formation of trivalent Fe ions, which intensely provide local 3d moments.

Structural and Optical Properties of BiFeO3 via Polymer-Assisted Hydrothermal Synthesis under Different Weight of Chitosan

2021 ◽  
Vol 317 ◽  
pp. 53-59
Author(s):  
Muhammad Safwan Sazali ◽  
Muhamad Kamil Yaakob ◽  
Mohamad Hafiz Mamat ◽  
Oskar Hasdinor Hassan ◽  
Muhd Zu Azhan Yahya
Keyword(s):  
Optical Properties ◽  
Single Phase ◽  
Energy Gap ◽  
Bismuth Ferrite ◽  
Secondary Phase ◽  
Synthesis Process ◽  
Rhombohedral Structure ◽  
X Ray Diffraction ◽  
Structural And Optical Properties ◽  
Diffraction Angle

In this work, single phase Bismuth Ferrite, BiFeO3 was successfully synthesized by using hydrothermal method assisted with different weight (0.24 g, 0.36 g and 0.48 g) of Chitosan. Potassium hydroxide (KOH) were used as a mineralizer during the synthesis process for the precipitation. The samples were characterized for different properties such as structural and optical properties, and were then compared with previous works. The X-ray diffraction data for all the samples showed that the samples had a single phase belonging to R3c space group with perovskite rhombohedral structure at diffraction angle 32.0° to 32.5° even though the slight presence of secondary phase at diffraction angle 28° was detected. Scanning electron microscope revealed a decrement in particle size as the weight of Chitosan increased indicating effective used of Chitosan in controlling the agglomeration of the particles. All samples BiFeO3 assisted with and without Chitosan showed significant enhancement in energy gap where the obtained results showed a small energy gap values ranging from ~1.22 eV to ~1.88 eV determined from UV-vis absorbance characterization. Therefore, by the addition of Chitosan, the properties of BiFeO3 such as structural and optical have changed as well as preventing from the particle to agglomerate.

scholarly journals A Comparative Study of Spinel ZnFe2O4 Ferrites Obtained via a Hydrothermal and a Ceramic Route: Structural and Magnetic Properties

2020 ◽  
Author(s):  
Xuesong Zhu ◽  
Chunxiang Cao ◽  
Shubing Su ◽  
A.L. Xia ◽  
Huiyan Zhang ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Comparative Study ◽  
Spinel Structure ◽  
Single Phase ◽  
Hydrothermal Process ◽  
Ceramic Method ◽  
Mixed Spinel ◽  
Structural And Magnetic Properties ◽  
Ceramic Route ◽  
Fe Ions

Abstract The spinel ZnFe2O4 specimens were obtained via a hydrothermal and a ceramic method, respectively, and their structural and magnetic properties were comparatively studied. It was found that all the specimens exhibited a single-phase and mixed spinel structure. The magnetism of specimens synthesized via the hydrothermal method is obviously greater than that of specimen prepared via the ceramic method. This can be ascribed to the occupancy of Fe ions resulted from the loss of Zn during the hydrothermal process.

Preparation and Characterization of Dielectric Behavior of A2/3Cu3Ti4O12 (A = Nd, Sm, Gd, Dy) Ceramics

2010 ◽  
Vol 67 ◽  
pp. 28-33 ◽  
Author(s):  
Dorota Szwagierczak ◽  
Jan Kulawik
Keyword(s):  
Single Phase ◽  
Elevated Temperatures ◽  
Relaxation Times ◽  
Dielectric Behavior ◽  
X Ray Diffraction ◽  
Conventional Solid State Reaction ◽  
Low Frequencies ◽  
Perovskite Materials ◽  
Very High

In this work perovskite materials A2/3Cu3Ti4O12 (where A=Nd, Sm, Gd, Dy) were synthesized by conventional solid state reaction and sintered at 1000-1100°C. X-ray diffraction analysis confirmed single-phase composition of the investigated ceramics. Dielectric properties of the samples were investigated in the temperature range from -55 to 300°C at frequencies 10 Hz – 2 MHz. Dielectric permittivities of the ceramics are very high, exceeding 105 at low frequencies and/or elevated temperatures (above 50°C) and 103 at higher frequencies and/or low temperatures. Two observed contributions to the dielectric response are attributed to semiconducting grains and more resistive grain boundaries. For Nd2/3Cu3Ti4O12 and Sm2/3Cu3Ti4O12 ceramics, the observed low- and high frequency plateaus are lower than those for Gd2/3Cu3Ti4O12 and Dy2/3Cu3Ti4O12. The relaxation times determined on the basis of impedance data were found to decrease with increasing atomic number of lanthanide. The analysis of the impedance spectroscopic data and the microstructure implies spontaneous formation of internal barrier layer capacitors in the investigated materials.

Characterization of 4H-SiC Bipolar Junction Transistor at High Temperatures

2014 ◽  
Vol 778-780 ◽  
pp. 1013-1016 ◽  
Author(s):  
Nuo Zhang ◽  
Yi Rao ◽  
Nuo Xu ◽  
Ayden Maralani ◽  
Albert P. Pisano
Keyword(s):  
Silicon Carbide ◽  
High Temperatures ◽  
Elevated Temperatures ◽  
Current Gain ◽  
Voltage Gain ◽  
Bipolar Junction Transistor ◽  
Voltage Amplifier ◽  
Junction Transistor ◽  
Comprehensive Characterization

In this work, a 4H-Silicon Carbide (SiC) Bipolar Junction Transistor (BJT) capable of operating at high temperatures up to 673 K is demonstrated. Comprehensive characterization including current gain, early voltage, and intrinsic voltage gain was performed. At elevated temperatures, although the current gain of the device is reduced, the intrinsic voltage gain increases to 5900 at 673 K, suggesting 4H-SiC BJT has the potential to be used as a voltage amplifier at extremely high temperatures.

Effect of Calcination Conditions on Phase Formation and Characterization of BiFeO3 Powders Synthesized by a Solid-State Reaction

2008 ◽  
Vol 55-57 ◽  
pp. 237-240 ◽  
Author(s):  
C. Silawongsawat ◽  
S. Chandarak ◽  
Thanapong Sareein ◽  
Athipong Ngamjarurojana ◽  
S. Maensiri ◽  
...  
Keyword(s):  
Solid State ◽  
Phase Formation ◽  
Solid State Reaction ◽  
Single Phase ◽  
Bismuth Ferrite ◽  
Vibrating Sample Magnetometer ◽  
Time Saving ◽  
First Time ◽  
Perovskite Type

A perovskite-type phase of Bismuth Ferrite, BiFeO3, powder was synthesized by a solid-state reaction via a rapid vibro-milling technique. The effect of calcination condition on the phase formation, and characterization of BiFeO3 powder was investigated. The formation of the BiFeO3 phase investigated as a function of calcination conditions by TG–DTA and XRD. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques and vibrating sample magnetometer (VSM) were used to characterize the structures and magnetic properties of prepared samples. The rapid vibro-milling is employed for the first time in this work as a significant time-saving method to obtain single-phase BiFeO3 powders.

Calcium Vanadinite: An Alternative Apatite Host for Cl-rich Wastes

2014 ◽  
Vol 1665 ◽  
pp. 319-324 ◽  
Author(s):  
M. R. Gilbert
Keyword(s):  
Elevated Temperatures ◽  
Secondary Phase ◽  
Phase System ◽  
Secondary Phases ◽  
Waste Forms ◽  
Good Potential ◽  
Multi Phase

ABSTRACTApatites are often seen as good potential candidates for the immobilization of halide-rich wastes and, in particular, chlorapatite (Ca5(PO4)3Cl) has received much attention in recent years. However, synthesis of chlorapatite waste-forms can produce a complicated multi-phase system, with a number of secondary phases forming, including β-TCP (Ca3(PO4)2), spodiosite (Ca2(PO4)Cl) and pyrophosphate (Ca2P2O7), many of which require elevated temperatures and extended calcinations times to reduce. Calcium vanadinite (Ca5(VO4)3Cl) demonstrates a much simpler phase system, with calcination at 750 °C yielding Ca5(VO4)3Cl together a small quantity of a Ca2V2O7secondary phase, the formation of which can be retarded by the addition of excess CaCl2. Characterization of compositions doped with SmCl3as an inactive analogue for AnCl3show the Cl to be immobilized in the vanadinite whilst the Sm forms a wakefieldite (SmVO4) phase.

Process optimization for the fabrication of Tl2Ba2Ca2Cu3O10 thin films

1996 ◽  
Vol 11 (6) ◽  
pp. 1349-1366 ◽  
Author(s):  
W. L. Holstein ◽  
L. A. Parisi
Keyword(s):  
Thin Films ◽  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Surface Resistance ◽  
Single Phase ◽  
Elevated Temperatures ◽  
Secondary Phase ◽  
Superconducting Transition ◽  
Microwave Surface Resistance ◽  
Partial Pressures

A process has been developed for the fabrication of nearly single phase superconducting Tl2Ba2Ca2Cu3O10 thin films on (100) LaAlO3 substrates with a superconducting transition temperature Tc of 120 K and low microwave surface resistance at temperatures up to 110 K. Amorphous BaCaCuO precursor films were first deposited by rf magnetron sputtering and then thallinated at elevated temperatures. The double TlO layer phases (Tl2Ba2Ca2Cu3O10 + Tl2Ba2CaCu2O8) formed preferentially over the single TlO layer phases (TlBa2Ca2Cu3O9 + TlBa2CaCu2O7) at high Tl2O partial pressures. Thin films containing Tl2Ba2Ca2Cu3O10 and a small amount of CuO were prepared from Cu-rich precursor films (Cu/Ba > 1.7), while lower Cu content led to the formation of Tl2Ba2CaCu2O8 as a secondary phase. Tl2Ba2Ca2Cu3O10 film epitaxy was enhanced by carrying out the thallination in reduced oxygen partial pressures of 0.01–0.05 atm. Following the thallination step, the Tl2Ba2Ca2Cu3O10 thin films had a superconducting transition temperature Tc of only 106 ± 4 K. An additional 62 h anneal at 800 °C or an 8 h anneal at 850 °C in a Tl2O/O2 atmosphere increased the Tc to 120 K. The increase in Tc was accompanied by a decrease in the c-axis lattice constant, an enhancement in the long-range order in the c-direction, and the formation of a small amount of Tl2Ba2CaCu2O8 as a secondary phase. Minimization of surface resistance at high temperature (95–110 K) requires that the fraction of Tl2Ba2CaCu2O8 secondary phase in the films be kept low. Process routes are also described for the formation of nearly single phase TlBa2Ca2Cu3O9 and TlBa2CaCu2O7 thin films and the formation of a new ordered intergrowth phase, Tl4Ba4Ca3Cu5O18, which consists of alternating Tl2Ba2CaCu2O8 and Tl2Ba2Ca2Cu3O10 layers.

Effect of the Type of Solvent and Bi-Stoichiometric Excess on the Purity of Nanocrystalline Bismuth Ferrite Single Phase

2012 ◽  
Vol 1454 ◽  
pp. 45-50 ◽  
Author(s):  
Gina Montes-Albino ◽  
Marco Gálvez-Saldaña ◽  
Boris Renteria-Beleño ◽  
Oscar Perales-Pérez
Keyword(s):  
Acetic Acid ◽  
Ethylene Glycol ◽  
Single Phase ◽  
Bismuth Ferrite ◽  
Average Crystallite Size ◽  
Secondary Phase ◽  
Systematic Evaluation ◽  
Acid Media ◽  
Synthesis Conditions ◽  
Main Challenge

ABSTRACTThe main challenge associated with the synthesis of pure bismuth ferrite (BFO) is the extremely high stability of parasitic or secondary phase Bi-oxides, which contaminates the single ferrite phase and affects the corresponding functional properties. Therefore, any attempt to determine the optimum synthesis conditions conducive to the inhibition of the formation of those impurity phases becomes indispensable. Accordingly, the present work addresses the systematic evaluation of the type of solvent and synthesis parameters to exclusively produce the BFO structure. Nanocrystalline BFO powders were synthesized after thermal treatment of the solid intermediates formed in ethylene glycol and acetic acid media. The experimental work also considered the effect of the excess of Bi species with respect to the BiFeO3stoichiometry and the annealing of the intermediates at different temperatures. The structure formation was confirmed by XRD analysis and magnetic properties were studied by VSM. X-ray diffraction analyses confirmed that powders exhibiting single phase BFO structure were produced after annealing the intermediate which was formed in acetic acid for one hour at 700°C. The average crystallite size and lattice parameter were calculated to be approximately 40 nm and 5.36 Å, respectively. It was also found that the synthesis under 7% of Bi-stoichiometric excess inhibited the formation of the parasitic phases after annealing the intermediate produced in ethylene glycol medium. The saturation magnetization of the powders annealed at 700°C were 0.15 emu/g and 0.17 emu/g when the BFO intermediates were formed in ethylene glycol and acetic acid media, respectively. The corresponding coercivity values were 6 Oe and 21 Oe.

Microstructural Characterization of Ferroelectric Bismuth Ferrite (BiFeO3) Ceramic by Electron Backscattered Diffraction

2011 ◽  
Vol 702-703 ◽  
pp. 1011-1014
Author(s):  
Jayant Kolte ◽  
Devidas Gulwade ◽  
Aatish Daryapurkar ◽  
Prakash Gopalan
Keyword(s):  
Direct Evidence ◽  
Bismuth Ferrite ◽  
Microstructural Characterization ◽  
Secondary Phase ◽  
Future Generation ◽  
Potential Candidate ◽  
Electron Backscattered Diffraction ◽  
Secondary Phase Formation ◽  
Backscattered Electron

Ferroelectric BiFeO3 (BFO) is potential candidate for future generation of FeRAM due to its large polarization. However, BFO is very sensitive to secondary phase formation during synthesis because of volatility issues related to Bismuth. Investigation of the microstructure for phase purity is the key as impurities can destroy the desired properties. We have used backscattered electron diffraction to study the microstructure of BFO ceramic. The EBSD results provide a direct evidence of the appearance of secondary phase that XRD could not be detected in XRD.

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