The Nd-Doping Effect on Dielectric Abnormity of BiFeO3 Ceramics below the Néel Temperature

2011 ◽  
Vol 687 ◽  
pp. 439-446 ◽  
Author(s):  
Dong Ge Chen ◽  
Xin Gui Tang ◽  
Qiu Xiang Liu ◽  
Xiao Fang Cheng ◽  
Yan Zou
Keyword(s):  
Complex Impedance ◽  
Precipitation Method ◽  
Neel Temperature ◽  
X Ray Diffraction ◽  
Néel Temperature ◽  
Low Leakage ◽  
Low Leakage Current ◽  
Different Temperatures ◽  
Co Precipitation ◽  
Complex Impedance Spectra

Bismuth neodymium ferrite (Bi1-xNdxFeO3: BNFO;x=0, 0.025, 0.075, 0.125, 0.175) ceramics were prepared by a co-precipitation method and sintered at 800 °C, using nitrates as precursors. The crystal structure and dielectric properties of the samples were characterized by X-ray diffraction （XRD）and dielectric permittivity measurement at different temperatures and frequencies. XRD suggests that the impurity phases are weakened by suitably dopingx=0.075. Dielectric spectra indicate that relaxation peaks below the Néel temperature which may be produced by the effect of grain boundaries and dipoles with heating vanish after doping Nd at the same content. Complex impedance spectra manifest that the doped samples are closer to Debye-type, and the impedance rises which will lead to low leakage current.

A Comparative Study on the Morphology and Magnetic Properties of Barium and Strontium Hexaferrite Nanoparticles Synthesized by Co-Precipitation Method

2009 ◽  
Vol 67 ◽  
pp. 203-208 ◽  
Author(s):  
Sachin Tyagi ◽  
Ramesh Chandra Agarwala ◽  
Vijaya Agarwala
Keyword(s):  
Ultrafine Particles ◽  
Barium Hexaferrite ◽  
Nitrogen Atmosphere ◽  
Precipitation Method ◽  
Strontium Hexaferrite ◽  
X Ray Diffraction ◽  
Heat Treated ◽  
Different Temperatures ◽  
Co Precipitation ◽  
Decomposition Behaviour

Nanocrystalline strontium hexaferrite (SrFe12O19) and barium hexaferrite (BaFe12O19) powders were synthesized by co-precipitation method. The ‘as synthesized’ powders were heat treated (HT) at different temperatures ranging from 800 to 1200°C at a heating rate of 30°C /min in nitrogen atmosphere. Decomposition behaviour and the phases associated therein are investigated by thermal analysis (DTA/DTG/TG) and X-ray diffraction (XRD). Formations of ultrafine particles have been confirmed through field emission scanning electron microscop (FESEM). The superparamagnetic behavior of both, barium and strontium hexaferrite is confirmed by vibrating sample magnetometer (VSM). The increase in saturation magnetization from 1.94 to 31.05 emu/gm in case of barium hexaferrite and from 2.44 to 43.38 emu/gm for strontium hexaferrite is observed with HT temperatures. The changes in coercivity and remanence with HT temperatures for both the ferrites are analysed.

scholarly journals Zinc Titanate Nanopowders. Synthesis and Characterization

2021 ◽  
Author(s):  
M Gabal ◽  
Y.M. Al Angari
Keyword(s):  
Nitrogen Adsorption ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Zinc Titanate ◽  
Low Dielectric ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Precursor Decomposition ◽  
Co Precipitation ◽  
Adsorption Desorption

Abstract Zinc titanates nanopowders viz.; Zn2TiO4, ZnTi3O8 and ZnTiO3 were synthesized through the thermal decomposition course of ZnC2O4.2H2O-TiO2 precursor (1:1 mole ratio), prepared via a new co-precipitation method up to 900oC. Thermogravimetric measurement (TG) was utilized to characterize the precursor decomposition while X-ray diffraction (XRD), Fourier transform infra-red (FT-IR) were used to characterize the decomposition products as well as the phase transitions at different temperatures. XRD revealed the starting of titanates formation at 700oC via detecting Zn2TiO4 along with ZnO and TiO2 (anatase) diffraction peaks. By increasing the calcination temperature to 800oC, the ZnO content vanished with the appearing of Zn2Ti3O8 besides ZnTi2O4 and impurities of TiO2 (anatase). Finally at 900oC, the Zn2Ti3O8 content was decomposed into ZnTiO3. Nitrogen adsorption-desorption isotherm of the calcined precursor at 900oC indicated low specific surface area of 7.1 m2 g-1 in accordance with the agglomeration nature estimated via transmission electron microscopy (TEM) study. The conductivity measurements showed semiconducting behavior of the prepared titanates with ferroelectric transition in the range 200-308oC.The obtained low dielectric value suggests the uses of present titanates as a co-fired ceramic or resonator ceramics.

Modified Synthesis Temperature of Ba3 Co1.7 Ni0.1 Cu0.1 Mn0.1 Fe24 O41 Z-Type Ferrite Nanoparticles Prepared by Co-Precipitation Method

2013 ◽  
Vol 829 ◽  
pp. 737-741 ◽  
Author(s):  
Mohammad Javad Pourhosseini Asl ◽  
Ali Ghasemi ◽  
Gholam Reza Gordani
Keyword(s):  
Low Temperature ◽  
Synthesis Temperature ◽  
Precipitation Method ◽  
Diffraction Field ◽  
X Ray Diffraction ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Optimum Synthesis ◽  
Different Temperatures ◽  
Co Precipitation

In this study, the low temperature synthesis of barium-Z type hexaferrite nanoparticles was considered. In this manner, the Z-type hexaferrite with the chemical composition of Ba3 Co1.7 Ni0.1 Cu0.1 Mn0.1 Fe24 O41 was synthesized at different temperatures of 900, 1000 and 1100 0C for 3hr. An X-Ray diffraction, field emission scanning electron microscopy (FE-SEM) and a vibrating sample magnetometer (VSM) analysis were carried out to investigate structural and magnetic properties of samples. XRD results showed that the Z-type ferrite phase was formed in all samples. However, At the low temperature synthesis (T=900 0C), the Ba2Me2Fe12O22 and BaFe2O4 phases were also detected. FE-SEM micrographs showed that with increasing the synthesis temperature, the particle size was increased. It was found that the saturation of magnetization was slightly increased from 54 to 55. 5emugr with an increase in synthesis temperature from 900 to 11000C, while the coercivity increased initially from 670 Oe to 860 Oe and then decreased to 488 Oe. The results also indicated that the temperature of 10000C was the optimum synthesis temperature of Ba-Z type hexaferrite nanoparticles, which was much lower than that of Z-type hexaferrite produced by previous researchers.

Characterization of Al2(WO4)3 Synthesized by Co-Precipitation Method

2014 ◽  
Vol 798-799 ◽  
pp. 85-89 ◽  
Author(s):  
E.S.G. Junior ◽  
P.M . Jardim
Keyword(s):  
Precipitation Method ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Tem Analysis ◽  
X Ray ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Co Precipitation ◽  
Alpha Alumina

Al2(WO4)3was synthesized by co-precipitation using Na2WO4and Al (NO3)3as precursors. After drying the precipitate, it was calcined at different temperatures between 500°C and 800°C. The crystallization and degradation temperatures of the samples were evaluated by means of Differential Scanning Calorimetry (DSC), Thermogravimetry (TG) and X-Ray Diffraction (XRD). It was observed that the crystallization starts at around 600°C, however Transmission Electron Microscopy (TEM) analysis showed that at this temperature the sample is partially amorphous. The degradation of the material starts at around 1200°C and at 1400°C the tungsten oxide has almost completely evaporated and the material is transformed mainly in alpha-alumina.

Effect of Sintering Temperature on Nanostructured Multiferroic BiFeO3 Ceramics

2012 ◽  
Vol 510-511 ◽  
pp. 348-355 ◽  
Author(s):  
M.Y. Shami ◽  
M.S. Awan ◽  
M. Anis-ur-Rehman
Keyword(s):  
Sintering Temperature ◽  
Volumetric Strain ◽  
Precipitation Method ◽  
Ferromagnetic Behavior ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Electrical And Magnetic Properties ◽  
Multiferroic Bifeo ◽  
Different Temperatures ◽  
Co Precipitation

Nanostructured multiferroic BiFeO3(BFO) powders were synthesized by using the co-precipitation method. Calcination of acquired powder was carried out at 400°C for 3h. Uniaxially pressed pellets were sintered at 500°C, 600°C, 700°C and 800°C for 2 hours in air. These samples were characterized for structural, thermal, electrical and magnetic properties. X-ray diffraction (XRD) confirmed the amorphous nature of the as driven powder and phase purity of the calcined BFO sample. The crystallite size varied with the sintering temperature from 52 to 70 nm. Sintering above 500°C induced impure phases due to oxygen vacancies and volumetric strain in crystal structure. Ferroelectric to paraelectric transition temperature TC~815°C was verified by the differential scanning calorimetry (DSC). Surface morphology and grain growth was observed using scanning electron microscopy (SEM). Electrical ac measurements were performed in the frequency range from 20 Hz to 3 MHz at room temperature. For a particular sample, capacitance decreased and susceptance increased with the increase of applied frequency signal. These parameters were increased with the increase of sintering temperature. Vibrating sample magnetometer (VSM) revealed the diverse weak ferromagnetic behavior for the samples sintered at different temperatures. Maximum coercivity (Hc~119.2 Oe) and maximum remnant magnetization (MR~2.1x10-3emu/g) were obtained for the sample sintered at 700°C for 2hr.

Magnetic and dielectric properties of BiFeO3 nanoparticles

2015 ◽  
Vol 7 (2) ◽  
pp. 1393-1403
Author(s):  
Dr R.P VIJAYALAKSHMI ◽  
N. Manjula ◽  
S. Ramu ◽  
Amaranatha Reddy
Keyword(s):  
Diffuse Reflectance Spectrum ◽  
Precipitation Method ◽  
Secondary Phases ◽  
X Ray Diffraction ◽  
Bifeo3 Nanoparticles ◽  
Transmission Electron ◽  
Multiferroic Bifeo3 ◽  
Pure Phase ◽  
Simple Chemical ◽  
Co Precipitation

Single crystalline nano-sized multiferroic BiFeO3 (BFO) powders were synthesized through simple chemical co-precipitation method using polyethylene glycol (PEG) as capping agent. We obtained pure phase BiFeO3 powder by controlling pHand calcination temperature. From X-ray diffraction studies the nanoparticles were unambiguously identified to have a rhombohedrally distorted perovskite structure belonging to the space group of R3c. No secondary phases were detected. It indicates single phase structure. EDX spectra indicated the appearance of three elements Bi, Fe, O in 1:1:3. From the UV-Vis diffuse reflectance spectrum, the absorption cut-off wavelength of the BFO sample is around 558nm corresponding to the energy band gap of 2.2 eV. The size (60-70 nm) and morphology of the nanoparticles have been analyzed using transmission electron microscopy (TEM).   Linear M−H behaviour and slight hysteresis at lower magnetic field is observed for BiFeO3 nanoparticles from Vibrating sample magnetometer studies. It indicates weak ferromagnetic behaviour at room temperature. From dielectric studies, the conductivity value is calculated from the relation s = L/RbA Sm-1 and it is around 7.2 x 10-9 S/m.

scholarly journals Photoluminescent Properties of Hydroxyapatite and Hydroxyapatite/Multi-Walled Carbon Nanotube Composites

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 832
Author(s):  
Edna X. Figueroa-Rosales ◽  
Javier Martínez-Juárez ◽  
Esmeralda García-Díaz ◽  
Daniel Hernández-Cruz ◽  
Sergio A. Sabinas-Hernández ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Hexagonal Phase ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Multi Walled Carbon Nanotube ◽  
Nanotube Composites ◽  
Carbon Nanotube Composites ◽  
Co Precipitation ◽  
Functionalized Mwcnts

Hydroxyapatite (HAp) and hydroxyapatite/multi-walled carbon nanotube (MWCNT) composites were obtained by the co-precipitation method, followed by ultrasound-assisted and microwave radiation and thermal treatment at 250 °C. X-ray diffraction (XRD) confirmed the presence of a hexagonal phase in all the samples, while Fourier-transform infrared (FTIR) spectroscopy elucidated the interaction between HAp and MWCNTs. The photoluminescent technique revealed that HAp and the composite with non-functionalized MWCNTs present a blue luminescence, while the composite with functionalized MWCNTs, under UV-vis radiation shows an intense white emission. These findings allowed presentation of a proposal for the use of HAp and HAp with functionalized MWCNTs as potential materials for optoelectronic and medical applications.

Impedance Analysis of Layer Structured NBT–CBT Mixed Ceramics

1998 ◽  
Vol 12 (11) ◽  
pp. 433-441 ◽  
Author(s):  
P. S. Rama Sastry ◽  
T. Bhimasankaram ◽  
G. S. Kumar ◽  
G. Prasad
Keyword(s):  
Comparative Study ◽  
Complex Impedance ◽  
Impedance Analysis ◽  
Equivalent Circuits ◽  
Impedance Spectra ◽  
Ceramic System ◽  
Different Temperatures ◽  
Mixed Ceramics ◽  
Mixed Ceramic ◽  
Complex Impedance Spectra

Complex impedance spectra of ferroelectric mixed ceramic system ( Na 0.5 Bi 0.5)1-x Ca x Bi 4 Ti 4 O 15 with x=0, 0.1, 0.3, 0.5, 0.7 and 1 was studied as a function of frequency and temperature in the range 1 KHz to 10 MHz and 30°C to 620°C respectively. Equivalent circuits involving resistive and capacitive elements at different temperatures, activation energies of relaxations and conduction were evaluated using impedance plots. A comparative study of impedance and conductivity facilities an insight in understanding the electrical nature of these electroceramics.

Photocatalytic Activity of Fe-Doped ZnO/Montmorillonite Nanocomposite for Degradation of Malachite Green

2015 ◽  
Vol 827 ◽  
pp. 19-24 ◽  
Author(s):  
Nur Afifah ◽  
Nadia Febiana Djaja ◽  
Rosari Saleh
Keyword(s):  
Photocatalytic Activity ◽  
Malachite Green ◽  
Organic Dyes ◽  
Uv Light ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spin Resonance ◽  
Doped Zno ◽  
Co Precipitation

In this study, the photocatalytic activity of pure Fe- doped ZnO and Fe- doped ZnO/Montmorillonite nanocomposite has been investigated for the degradation of malachite green under UV light irradiation. Both photocatalysts were synthesized using co-precipitation method and characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier-transform infrared absorption, and electron spin resonance. The results showed that the photocatalytic efficiency is better in the presence of montmorillonite compared to pure Fe- doped ZnO. To detect the possible reactive species involved in degradation of organic dyes control experiments with introducing scavengers into the solution of organic dyes were carried out. It is found that electron plays an important role in the degradation of malachite green.

Conduction Characteristics of Charge Ordering Type Ferroelectrics,YFe2O4

2006 ◽  
Vol 966 ◽  
Author(s):  
Ken Imamura ◽  
Yoichi Horibe ◽  
Takeshi Yoshimura ◽  
Norifumi Fujimura ◽  
Shigeo Mori ◽  
...  
Keyword(s):  
Room Temperature ◽  
Inflection Point ◽  
Oxygen Deficiency ◽  
Complex Impedance ◽  
Charge Ordering ◽  
Neel Temperature ◽  
Ohmic Conduction ◽  
Néel Temperature ◽  
Impedance Measurements ◽  
Conduction Properties

ABSTRACTElectrical conduction properties of charge ordering type ferroelectrics YFe2O4 were investigated. YFe2O4 was synthesized in reduced atmosphere at 1200 °C. Oxygen partial pressure of the reduced atmosphere was controlled by the equilibrium state of CO and CO2. YFe2O4 is paramagnetic at room temperature and has Néel temperature around 250K. The Néel temperature was decreased with increasing the amount of oxygen deficiency. Moreover, YFe2O4 showed ohmic conduction from 260 to 100 K. The temperature dependence of the DC conductivity showed an inflection point at the Néel temperature, which indicated the development of charge ordering of Fe2+ and Fe3+ ions. From the complex impedance measurements, the equivalent circuits of YFe2O4 with different oxygen deficiency were determined at various temperatures.

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