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1.
《Ceramics International》2020,46(7):8730-8744
We have studied the structural, magnetic, dielectric and impedance properties of the Sm1-xBixFe1-yMnyO3 [SmFeO3 (SFO), Sm0.9Bi0.1FeO3 (SBFO), Sm0.9Bi0.1Fe0.9Mn0.1O3 (SBFMO)] polycrystalline samples synthesized by solid-state reaction method. Rietveld refinement of room temperature (RT) powder x-ray diffraction pattern confirms the orthorhombic crystal structure with Pnma/Pbnm space group. The average particle size of Bi doped and co-doped (Bi–Mn) samples determined from SEM analysis are 5.6 μm and 5.2 μm, respectively. Room temperature field-dependent magnetization increases, suggesting the presence of magnetic contribution due to the Rare earth-Fe ion interaction which persists even at RT. However, with co-doping of Bi and Mn, a decrease in magnetization is observed, which corresponds to the dilution of Fe3+-Fe3+ interactions due to the presence of Mn3+ ions. The observed values of magnetization at 90 kOe for Bi doped sample is (2.87 emu/g) approximately two times and for codoped (0.7 emu/g) sample is nearly half of that of pristine sample (1.51 emu/g). Dielectric measurements as a function of frequency/temperature and impedance analysis using equivalent circuit model reveal grain and grain boundary contributions of SBFO (at high temperature) and SBFMO (for all temperature) samples towards the electrical properties indicating the electrically heterogeneous nature of these samples. However, for SFO sample grain contribution is dominant. Observed value of dielectric constant varies from ~103-104 with Bi–Mn doping. The conduction mechanism of the studied samples has been explained by considering Jonscher power law. Arrhenius law fitting of AC conductivity data manifests two types of conduction mechanisms in these samples. The depressing nature of the semicircular arc observed in the Nyquist plot of all the samples indicates the presence of a non-Debye type of relaxation. 相似文献
2.
《Ceramics International》2015,41(8):9843-9848
Ni0.4Zn0.6Fe2O4 powders were prepared by combustion synthesis with different amount of NaClO4. Phases, particle size and magnetic properties of the powders and annealed powders were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and vibrating sample magnetism (VSM). The excess content of NaClO4 offered significant advantages with respect to the size, morphology and magnetic properties of the powders. After annealing, sub-micro ferrite spherical powders with spinel phase in a range of 500–800 nm can be obtained. With the increase of the NaClO4 content, the saturation magnetization of the powders shows a maximum value at 68.8 emu/g when w=0.4, whereas the coercivity stayed nearly constant. The maximum saturation of annealed powders by combustion synthesis is much higher than the range reported in the literature. 相似文献
3.
Amir Abbas Nourbakhsh Azadeh Vahedi Ali Nemati Mohsen Noorbakhsh Seyed Nezamoddin Mirsatari Mehrdad Shaygan Kenneth J.D. Mackenzie 《Ceramics International》2014
The aim of this paper was to improve the magnetic properties of magnetoplumbite-type (M-type) strontium hexaferrite substituted with Co2+–La3+ produced by conventional ceramic forming techniques. The effect on the magnetic properties of varying the composition of the target compound Sr1−xLaxFe12−yCoyO19 and the primary and secondary firing temperatures was investigated. Microstructure studies and XRD phase analysis indicated that optimum values of the remanent magnetization Br and coercive field Hcj were obtained with a primary firing temperature of 1240 °C and a final firing temperature of 1180 °C, where (x=y)th 1=0.15, (y/x)exp 2=0.75 and the molar ratio of ferric oxide to strontium oxide=5.8. The optimized magnetic properties obtained under these conditions were Br=4070 Gs, Hcj=4710 Oe, (Hk/Hcj)=82. 相似文献
4.
In this study, Sr and Ca doped LaMnO3 thin ceramic films were coated on Al2O3 substrates by using a sol–gel route as the cathode material for SOFC. Nitrate precursors were used for the preparation of the thin film coating solution, and methanol and acetyl acetone were also used as the solvent and chelating agent, respectively. After the solution was prepared, an Al2O3 single crystal substrate was dipped into the solution. Then it was fired at 500 °C and annealed at 1025 °C for the crystallization. Coated films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), focused ion beam (FIB) and atomic force microscopy (AFM). Conductivity of the coated films was measured by the four probe Van der Pauw method. XRD, SEM, AFM and FIB characterizations of the coated film showed that the LaMnO3 phase was formed, surface of the films was uniform and had homogenously distributed pores sized about 10 nm, mean grain size was about 60–80 nm and the film thickness was about 180 nm. The specific resistivity of the film was calculated to be 0.524 Ω m. 相似文献
5.
A series of nanocrystalline Li0.25Ni0.5Fe2.25−xErxO4 (x=0.00, 0.02, 0.06, 0.08, and 0.10) ferrite powders, having a cubic spinel crystal structure and a low value of coercivity, was synthesized by the sol–gel auto-combustion route. The structure, morphology and magnetic properties of the prepared nanoferrites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the magnetic property measurement system (MPMS). A well-defined single phase spinel structure is confirmed in all the samples by X-ray diffraction analysis. The lattice parameters of the samples increase slightly with increasing the erbium content. The crystallite size of the Er-doped samples is smaller than that of pure Li–Ni ferrite, and decrease regularly in the range of 36.0–14.5 nm. It has been observed that the magnetic properties of these ferrites are strongly influenced by the added erbium content. The magnetic measurements indicate that saturation magnetization (Ms) and coercivity (Hc) decrease gradually with the increase of Er content in the lattice. 相似文献
6.
Gunjan Srinet Prateek Varshney Ravindra Kumar Vivek Sajal P.K. Kulriya M. Knobel S.K. Sharma 《Ceramics International》2013
Effects of Co doping on the structural, optical and magnetic properties of ZnO samples prepared by the sol–gel method are reported. The X-ray diffraction, X-ray photoelectron spectroscopy and UV–visible spectroscopy confirmed the substitution of Co ions on Zn sites without changing the wurtzite structure. No segregated secondary phases or Co rich clusters were detected. Optical absorption spectra of the samples exhibit a blue shift in the absorption band edge with increasing dopant concentration. The photoluminescence measurements show a blue shift in UV emission peak with the increase in Co concentration and a slight shift in the green emission band at around 509 nm which gets suppressed for higher sintering temperature. The field dependence of magnetization observed at room temperature exhibits clear ferromagnetic behavior. Efforts have been made to fit the experimental M–H data using the magnetic polarons model (BMP) which involves localized carriers and magnetic cations. The calculated concentration of the BMPs is found to be below the typical percolation threshold in ZnO. Thus BMP model alone is not sufficient to explain the room temperature ferromagnetic behavior in ZnO. To know the exact magnetic ordering in the system, we also attempted to fit temperature dependent magnetization curves with the Curie–Weiss Law which shows antiferromagnetic ordering in all samples. 相似文献
7.
《Ceramics International》2017,43(4):3879-3884
The purpose of the research was to improve the intrinsic magnetic properties of strontium ferrite by substituting lanthanum and cobalt for strontium and iron. The salt-assisted ultrasonic spray pyrolysis (SA-USP) following calcination process were used to from La-Co substituted strontium ferrite particles (LaxSr1-xFe12-yCoyO19), and their compositional dependent magnetic properties systemically investigated. All the samples were calcined at 1050 °C for 1 h in an air atmosphere to yield single-phased hexagonal particles several hundred nanometers to microns in size. A saturation magnetization of 70.76 emu/g and a coercivity 7265 Oe were obtained at a composition of La0.25Sr0.75Fe11.75Co0.25O19. The amount of Co was reduced to obtain an optimized saturation magnetization of 71.40 emu/g and a coercivity of 7572 Oe at a composition of La0.25Sr0.75Fe11.8Co0.2O19. 相似文献
8.
In this work, nanocrystalline M–Zn ferrites (M=Ni; Mn; Cu) with compositions of M1?xZnxFe2O4 (x=0.0, 0.2 and 0.4) were synthesized from metal nitrate precursors by rapid the sol–gel combustion method using diethanolamine (DEA) as the fuel. As-synthesized powders were calcined at 1000 °C for 4 h. The crystal structures and morphologies of these compounds were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM), respectively. The chemical interaction of ferrite powders was investigated by Fourier transform infrared spectroscopy (FTIR). The magnetic properties of after-calcined nanoparticles were measured at room temperature using a vibrating sample magnetometer (VSM). The single phase spinel cubic structure formation is confirmed by XRD and FTIR results. Meanwhile FE-SEM micrographs show the appearance of both undoped and Zn-doped ferrite ceramic samples. In addition, the VSM analyses indicate that the Zn content has a significant influence on the magnetic properties such as saturation magnetization (Ms) and coercivity (Hc). 相似文献
9.
《Journal of the European Ceramic Society》2003,23(13):2193-2202
For the development of a new wear resistant and chemically stable glass-ceramic glaze, the CaO–ZrO2–SiO2 system was studied. Compositions consisting of CaO, ZrO2, and SiO2 were used for frit, which formed a glass-ceramic under a single stage heat treatment in electric furnace. In the sintered glass-ceramic, wollastonite (CaSiO3) and calcium zirconium silicate (Ca2ZrSi4O12) were crystalline phases composed of surface and internal crystals in the microstructure. The internal crystal formed with nuclei having a composition of Ca1.2Si4.3Zr0.2O8. The CaO–ZrO2–SiO2 system showed good properties in wear and chemical resistance because the Ca2ZrSi4O12 crystals positively affected physical and mechanical properties. 相似文献
10.
The microstructure, electrical properties, and dielectric characteristics of the ZNR (zinc oxide-based nonlinear resistors), which are composed of zinc oxide-based ceramics doped with Pr–Co–Cr–La, were investigated at different sintering temperatures (1240, 1245, 1250, 1255, 1260, and 1300 °C). The increase of sintering temperature led to more densified ceramics, whereas it decreased the nonlinear properties and breakdown voltage. The highest nonlinearity was obtained from 1240 °C, with 79.3 in nonlinear coefficient and 0.3 μA in leakage current. As the sintering temperature increased, the donor density increased from 0.90 × 1018 to 2.59 × 1018/cm3, and the barrier height decreased from 1.90 to 0.67 eV, and the dielectric dissipation factor increased from 0.0874 to 0.2839. 相似文献
11.
Titania and titania–silica aerogels were prepared by alkoxide or non-alkoxide sol–gel route and subsequent supercritical drying
with carbon dioxide at low temperature. The resulting aerogels having high surface area and mesoporosity were used as photocatalysts
for gas phase methanol degradation reaction. Photocatalytic degradation reactions were carried out on titania and titania–silica
aerogels, and commercial Degussa P-25 titania. The photocatalytic activities of titania and titania–silica aerogels were higher
than that of the P-25. While the conversion of methanol degradation over the P-25 catalyst was only 50–60%, that for the titania
aerogel was observed to be above 98% due to the higher specific surface area and the well developed mesoporous structure.
In spite of lower titania contents, much higher surface area and high dispersion of titania of titania–silica aerogel gave
rise to the high photocatalytic activity in comparison to those of titania aerogels. Moreover, titania–silica aerogel was
also used for the photodegradation and adsorption hybrid system. It was observed that the high removal efficiency for methanol
was caused by the combination of higher catalytic activity and adsorption capacity. 相似文献
12.
《Ceramics International》2016,42(4):4748-4753
The effect of substitution of diamagnetic Al3+ and In3+ ions for partial Fe3+ ions in a spinel lattice on the magnetic and microwave properties of magnesium–manganese (Mg–Mn) ferrites has been studied. Three kinds of Mg–Mn based ferrites with compositions of Mg0.9Mn0.1Fe2O4, Mg0.9Mn0.1Al0.1Fe1.9O4, and Mg0.9Mn0.1In0.1Fe1.9O4 were prepared by the solid-state reaction route. Each mixture of high-purity starting materials (oxide powders) in stoichiometric amounts was calcined at 1100 °C for 4 h, and the debinded green compacts were sintered at 1350 °C for 4 h. XRD examination confirmed that the sintered ferrite samples had a single-phase cubic spinel structure. The incorporation of Al3+ or In3+ ions in place of Fe3+ ions in Mg–Mn ferrites increased the average particle size, decreased the Curie temperature, and resulted in a broader resonance linewidth as compared to un-substituted Mg–Mn ferrites in the X-band. In this study, the In3+ substituted Mg–Mn ferrites exhibited the highest saturation magnetization of 35.7 emu/g, the lowest coercivity of 4.1 Oe, and the highest Q×f value of 1050 GHz at a frequency of 6.5 GHz. 相似文献
13.
E. Muhammad Abdul Jamal P. A. Joy Philip Kurian M. R. Anantharaman 《Polymer Bulletin》2010,64(9):907-923
Rubber–nickel nanocomposites were synthesized by incorporating freshly prepared nanometric nickel particles in two different
matrices namely natural rubber and neoprene rubber according to specific recipes for various loadings of nano nickel and the
cure characteristics of these composites were evaluated. The maximum torque values register an increase with the increase
in loading of nickel in both composites and this is attributed to the non-interacting nature of nickel nanoparticles with
rubber matrices. The cure time of natural rubber composites decreases with increase in the content of nickel, and in neoprene
rubber cure, time increases with increase in filler content. In natural rubber, the curing reaction seems to be activated
by the presence of nickel particles. The magnetization studies of the composites reveal that the magnetic properties of nickel
are retained in the composite samples. The elastic modulus of natural rubber and neoprene rubber are largely improved by the
incorporation of nickel particles. 相似文献
14.
B.T. Raut M.A. Chougule S.R. Nalage D.S. Dalavi Sawanta Mali P.S. Patil V.B. Patil 《Ceramics International》2012,38(7):5501-5506
Camphor sulfonic acid (CSA) doped polyaniline/CdS nanohybrid materials were prepared by chemical oxidative polymerization method and characterized by field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR) spectroscopy. It is proved that there is a strong synergetic interaction between the CSA and polyaniline–CdS nanohybrid. Gas sensing measurements showed that the gas sensor based on the CSA doped PANi–CdS nanohybrid had high sensor response (75%), good selectivity (for H2S) and stability (97.34%), as well as comparatively short recovery time to H2S, operating at room temperature. The enhanced gas sensing performance of the nanohybrid is due to the high surface area of the CSA doped PANi–CdS hybrids and the p–n heterojunction formed between p-type polyaniline and n-type CdS nanoparticles. 相似文献
15.
L. P. Mezentseva I. Yu. Kruchinina A. V. Osipov V. L. Ugolkov V. F. Popova S. K. Kuchaeva 《Glass Physics and Chemistry》2017,43(1):98-105
A series of physical–chemical studies of a series of binary REE orthophosphate systems has been performed: LaPO4–DyPO4–H2O, LaPO4–YPO4–H2O, LaPO4–LuPO4–H2O, YPO4–LuPO4–H2O, and YPO4–ScPO4–H2O. Nanopowders of Ln'1 ?xLn'x PO4 · nH2O orthophosphates have been synthesized by the sol–gel method using direct and reverse precipitation techniques. Ceramic samples were produced from the nanopowders, and their physical–mechanical properties were determined depending on the thermal treatment temperature and duration. The ceramic samples’ thermal behavior has been investigated by the dilatometry method. The results have been compared depending on the technique of nanopowder synthesis. 相似文献
16.
S. Rada E. Culea R. Chelcea M. Rada A. Bot N. Aldea V. Rednic 《Ceramics International》2013,39(2):1403-1411
Glasses and glass ceramics of the xMoO3(100?x)[7GeO2·3PbO] system where x=0–30 mol% MoO3 were synthesized and characterized in order to obtain information about the structural correlations and the relationship between structure and physical properties in these materials. Changes of the FTIR, UV–vis and EPR data are discussed in view of the glass network structural changes determined by the evolution of molybdenum ions state, glass composition and MoO3 concentration.The spectroscopic studies indicate that with increasing of MoO3 content a fraction of the Mo6+ ions convert Mo3+ and Mo5+ ions. Accordingly, these modifications cause the depolymerization of the host network, the increase of the structural disorder and formation of GeO2 and PbMoO4 crystalline phases. The shape of EPR spectra is modified by the increase of the MoO3 concentration indicating that molybdenum ions exists in glass and glass ceramics in more than one valence state. The EPR spectra contain a broad line located at g~5.2 and, for the samples with a MoO3 content up to x≥15 mol%, the presence of the hyperfine structure characteristic for the Mo5+ ions can be observed, too.The electrochemical performances of the glass and glass ceramics samples with x=10 and 30 mol% MoO3 were demonstrated by cyclic voltammetry. 相似文献
17.
M. K. Rendale S. N. Mathad D. C. Kulkarni V. Puri 《International Journal of Self-Propagating High-Temperature Synthesis》2016,25(2):86-91
Li0.35–0.5x Mg x Zn0.3Fe2.35–0.5x O4 nanoparticles (x = 0, 0.14, 0.28, 0.42, 0.56, and 0.70) were prepared by low-cost combustion synthesis at relatively low temperature. Thick films of Li–Mg–Zn ferrite were prepared by screen printing method and characterized by XRD and microwave characteristics at microwave frequencies (within X- and Ku-bands) by overlay technique using λ/2 rejection filter. The influence of magnesium content x on the resonance frequency, quality factor, effective dielectric constant, complex permittivity, complex permeability, microwave conductivity, and penetration depth was explored. 相似文献
18.
Crystallisation of magnetite in multicomponent glass melts was investigated. Structural features and magnetic properties were tested using X-ray diffraction, scanning electron microscope techniques, vibrating sample magnetometer and Mössbauer spectroscopy at room temperature. The results show that the magnetite phase was detected in the glass–ceramic samples after heat treatment at higher crystallisation temperature (over 900°C). Fe2+ and Fe3+ ions contribute to the formation of magnetite crystal. Various crystal morphologies were observed. Isomer shift values suggest that Fe3+ and Fe2+ are in tetrahedral and octahedral coordination respectively. The saturation magnetisation tends to increase with the crystallisation temperature. 相似文献
19.
Al-doped BiFeO3 (BiFe(1?x)AlxO3) thin films with small doping content (x=0, 0.05, and 0.1) were grown on Pt(111)/TiO2/SiO2/Si substrates at the annealing temperature of 550 °C for 5 min in air by the sol–gel method. The crystalline structure, as well as surface and cross section morphology were studied by X-ray diffraction and scanning electron microscope, respectively. The dielectric constant of BiFeO3 film was approximately 71 at 100 kHz, and it increased to 91 and 96 in the 5% and 10% Al-doped BiFeO3 films, respectively. The substitution of Al atoms in BiFeO3 thin films reduced the leakage current obviously. At an applied electric field of 260 kV/cm, the leakage current density of the undoped BiFeO3 films was 3.97×10?4 A/cm2, while in the 10% Al-substitution BiFeO3 thin films it was reduced to 8.4×10?7 A/cm2. The obtained values of 2Pr were 63 μC/cm2 and 54 μC/cm2 in the 5% and 10% Al-doped BiFeO3 films at 2 kHz, respectively. 相似文献
20.
Hybrid nanocomposite coatings were prepared by sol–gel method using silica, titania and alumina nanoparticles derived from their alkoxides precursors; in the presence of 3-glycidoxypropyl-trimethoxysilane (GPTMS) and bisphenol A (BPA) on 1050 aluminium alloy substrate. The effect of type and ratio of nanoparticles on mechanical behaviour of the coatings were investigated by dynamic mechanical thermal analysis (DMA) and nanoindentation experiments. DMA results demonstrated that the values of the glass transition temperature (Tg) and the temperature at maximum tan (δ), (Tt) as well as the storage modulus of the hybrid samples depend mainly on the silane content and titania to alumina molar ratio of nanoparticles in the coating composition. In addition, nanoindentaion experiments were performed to study the mechanical properties such as hardness, elastic modulus and E/H ratio for the nanocomposite hybrid coatings. Nanoindentation results indicate that the homogenous reinforced structure was formed in the surface of nanocomposite coating with incorporation of titania and alumina-derived nanoparticles. The incorporation of TiO2 in comparison with AlOOH nanoparticles in the GPTMS-based coatings showed an improving effect on E/H ratio. 相似文献