Nanocrystalline Zinc Ferrite Research Articles

Impacts of annealing temperature on microstructure, optical and electromagnetic properties of zinc ferrites nanoparticles synthesized by polymer assisted sol-gel method

Nanocrystalline zinc ferrite (NZF) were successfully synthesized at different calcination temperature via sol-gel method from the precursor salt solutions using tartaric acid and PVA solution as a chelating agent and binder respectively. The characterization of NZF and their properties had been investigated using sophisticated techniques viz. X-ray diffraction, Fourier transform infra-red spectroscopy, Scanning electron microscopy, Transmission electron microscopy, Energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, UV–Vis-NIR spectroscopy, Vibrating sample magnetometer and Impedance analyzer. X-ray peak profile analysis through Debye Scherer and Wilson method, Halder-Wagner method has been used to estimate the structural parameters. The crystallite size and particle size of ZnFe2O4 samples were found to increases with increasing annealing temperature while lattice parameters and lattice strain decreases. Dynamic light scattering and zeta potential measurements were used to evaluate the particle size distribution and stability of these systems. The room temperature magnetic properties measurement showed that the net magnetic moment is observed for NZF due to cation distribution although the bulk ZnFe2O4 is non-magnetic. Direct optical band gaps of the prepared NZF samples has been investigated by UV–Vis NIR spectroscopy using Tauc formula and found that energy band gaps (Eg) values are in a narrow range of 1.19–1.86 eV. The frequency dependent dielectric properties, impedance and modulus spectroscopy measurement has been investigated in the frequency range of 100 Hz to 20 MHz. The synthesized NZF particles will be applied for Gas sensor, humidity sensor and photocatalyst.

Albumen-mediated Green Synthesis of ZnFe2O4 Nanoparticles and Their Physico-Chemical Properties

Abstract: Spinel ferrites with general formula AB2O4 possess charming magnetic and electrical properties owing to their thermal and chemical steadfastness. Spinel zinc ferrite (ZnFe2O4) nanoparticles have attracted massive attention due to their unusual amalgamation of properties, especially magnetic properties, where these properties are equipped as suitable candidates in the field of electronics. Here, a simple self-combustion technique is made with the assistance of albumen to synthesize nanocrystalline zinc ferrite (ZnFe2O4) particles. The egg white (albumen) that is used in the synthesis process plays the fuel role in the process of combustion. The results of the powder X-ray diffraction (PXRD) and Fourier Transform Infrared Spectroscopy (FTIR) suggested that the synthesized nanoparticles are of single phase and show spinel structure. The photoluminescence studies reported a doublet peak at around 360-380 nm. The functional groups present in the synthesized nanoparticles were revealed from FTIR data. EDX findings give an account of the percentage composition of the elements Fe, Zn and O present in the synthesized sample. High-resolution Scanning Microscope (HRSEM) reveals the agglomerated coalescence nature of ferrite nanoparticles. Keywords: Ferrite, PXRD, FTIR, HRSEM, EDX Albumen.

Investigation on Synthesis, Structural and Electrical properties of Zinc Ferrite on Gamma Irradiation

In the view of magnetic materials application, ferrites are the most attention-grabbing materials therefore in the present work nanocrystalline Zinc ferrite (ZnFe2O4) was prepared by sol-gel auto combustion technique. The synthesis was carried out by using citric acid as a chelating agent and nitrates as oxidant. The preparation of zinc ferrite was done at a sufficiently low temperature of 1000C. To get the good crystallinity and ferrite phase formation of prepared nanopowder was sintered at 5500C for 4 hours and then used for structural and electric investigations. Prepared ZnFe2O4 sample have been irradiated by a gamma-ray source (60Co) to examine the changes that occurred in structural and electrical properties. These changes on gamma irradiation were investigated by X-ray diffraction (XRD) technique and two probe technique respectively. From XRD patterns, it was observed that the lattice constant and average crystallite size decrease after gamma irradiation. DC electrical resistivity after gamma irradiation revealed that the charge carrier concentration and activation energy of zinc ferrite increases whereas drift mobility (µ) decreases.

Reversible transitions among four modes of nonpolar resistive switching characteristics in nano-crystalline zinc ferrite magnetic thin films

Nano-crystalline zinc ferrite (ZnFe2O4) magnetic thin film was prepared on Pt/Ti/SiO2/Si substrate by chemical solution deposition method though spin coating technique. Reproducible nonpolar resistive switching (RS) characteristics in Pt/ZnFe2O4/Pt devices are reported. By changing the magnitude and polarity of the applied electric bias, reversible transitions among all the four nonpolar RS modes can be realized. For each switching mode, I-V characteristics were measured in the temperature range of 200 K–340 K. Temperature dependent I-V characteristics of high resistance state (HRS) have been found to support the conduction mechanism across the metal/insulator/metal (MIM) systems to be Schottky emission. Associated parameters such as activation energy and effective height of Schottky barrier at zero biasing (ϕo) have been evaluated at different temperature and electric field. In addition, the increase in resistance of low resistance state (LRS) with temperature revealed that the conduction through ZnFe2O4 in LRS is metallic. Based on the temperature-dependent characteristics, the reversible switching among the four modes of nonpolar RS via formation and rupture of the conducting filaments has been attributed to the joint effect of field-induced migration of oxygen vacancies and metallic Zn atoms.

Magnetostriction studies in nano-crystalline zinc ferrite thin films by strain modulated ferromagnetic resonance

The magnetoelastic properties of nano-crystalline zinc ferrite (ZnFe2O4) thin films prepared by Pulse laser deposition on amorphous fused quartz substrates have been investigated by means of the strain-modulated ferromagnetic resonance, as a function of the substrate temperature during the deposition, and as a function of the annealing temperature. Magnetoelastic constants reveal the same trends as the magnetization, showing correlation between these two parameters. The results are similar to that obtained earlier for the Y3Fe5O12 ferrite.

Temperature and field dependent magnetization studies on nano-crystalline ZnFe2O4 thin films

Single phase nano-crystalline zinc ferrite (ZnFe2O4) thin films were deposited on fused quartz substrate using the pulsed laser deposition technique. The films were deposited at different substrate temperatures. The field dependence of magnetization at 10 K shows hysteresis loops for all the samples. Temperature dependence of the field cooled (FC) and zero field cooled (ZFC) magnetization indicated irreversible behavior between the FC and ZFC data, and the irreversibility depends on the measuring magnetic field. The thermo-magnetic irreversibility in the magnetization data is correlated with the magnitude of the applied field and the coercivity (HC) obtained from the M-H loops.

Magnetization in Nanocrystalline PLD Zinc Ferrite Thin Films Deposited on Fused Quartz Substrate

The nanocrystalline zinc ferrite (ZnFe2 O 4) thin films were grown on the fused quartz substrate using pulsed laser deposition. The effects of atmospheric conditions on structural, magnetic, and morphological properties have been systematically studied using X-ray diffraction, vibrating sample magnetometry, and atomic force microscopy. The films showed textured growth of zinc ferrite for the substrate temperatures at ≥ 600 °C irrespective of the ambient environment. Interestingly, thin films of zinc ferrite showed a magnetic hysteresis loop in contrast to the paramagnetic nature of their bulk counterpart. The value of saturation magnetization (4π M s) increased from 130 to 360 G when the substrate temperature was increased from room temperature (RT) to 800 °C in the oxygen atmosphere. In the absence of oxygen pressure, the value of 4π M s is observed to be 330 G for the film deposited at RT and found to increase to a value of 670 G when the film is deposited at 400 °C and the maximum value of 2580 G is observed for the film deposited at 700 °C. However, the value of 4π M s of 800 °C dropped down to 2000 G.

Influence of particle size on H2 and H2S sensing characteristics of nanocrystalline zinc ferrite

Nanocrystalline zinc ferrite ZnFe2O4 was synthesized by sol–gel self-combustion technique. Ball milling at room temperature was carried out to control the particle size. Characterization of synthesized powders was made using X-ray diffraction and transmission electron microscopy analysis. Fine powders resulted from milling were used to prepare gas sensing elements in pellet form. The gas-sensing properties were studied in presence of hydrogen and hydrogen sulphide as test gases. The gas response behavior was found to be strongly influenced by the particle size. Significantly high sensitivity of ~82 % was found for ~7 nm zinc ferrite in presence of 200 ppm H2S at an operating temperature of 150 °C. Sensitivity was found to increase with temperature before being maximum at a particular operating temperature.

Effect of chromium substitution on the structural and magnetic properties of nanocrystalline zinc ferrite

Single-phase Cr doped zinc ferrites have been synthesized by hydrothermal method. The crystal structure, microstructure, crystallite size and distribution, composition and magnetic properties of the synthesized nanoparticles were determined using X-ray powder diffraction, electron microscopies and vibrating sample magnetometry. Powders are composed of ultrafine spherical nanoparticles with a highly homogeneous elemental composition. The nanoparticles have partially inversed cubic spinel structure with average crystallite size below 10 nm. Superparamagnetic behavior is observed at high temperature while ferrimagnetic ordering and surface spin canting is reported at 5 K. Substitution of Fe with Cr ions controls both structural and magnetic parameters.

Mössbauer and magnetic studies of nanocrystalline zinc ferrites synthesized by microwave combustion method

Zinc ferrite nano-crystals were synthesized by a microwave assisted combustion route with varying the urea to metal nitrates (U/N) molar ratio The process takes only a few minutes to obtain Zinc ferrite powders. The Effect of U/N ratio on the obtained phases, particle size, magnetization and structural properties has been investigated. The specimens were characterized by XRD, Mossbauer and VSM techniques. The sample prepared with urea/metal nitrate ratio of 1/1 was a poorly crystalline phase with very small crystallite size. A second phase is also detected in the sample. The crystallite size increases while the second phase decrease with increasing the urea ratio. The saturation magnetization and coercivity of the as prepared nano-particles changed with the change of the U/N ratio. The powder with the highest U/N ratio showed the presence of an unusually high saturation magnetization of 16 emu/g at room temperature. The crystallinity of the as prepared powder was developed by annealing the samples at 700 ∘C and 900 ∘C. Both the saturation magnetization (Ms) and the remnant magnetization (Mr) were found to be highly dependent upon the annealing temperature. Mossbauer studies show magnetic ordering in the powder even at room temperature. The Mossbauer and the magnetic parameters of this fraction are different from the standard values for bulk zinc ferrite.

Incorporation of Cr 3+ ions in tuning the magnetic and transport properties of nano zinc ferrite

Cost effective and low temperature synthesis methods namely solution combustion and hydrothermal methods were used to prepare chromium incorporated nanocrystalline zinc ferrites. The effect of incorporation of low concentration Cr3+ ions on the structural, morphological, magnetic and transport properties of the zinc ferrite compounds were investigated. The crystalline nature and size variation with chromium content were valid from powder x-ray diffraction. Particles size and crystallite size variation were valid from scanning electron microscopy and transmission electron microscopy respectively. With the increase in chromium incorporation, the crystallite and particles sizes were decreased. Fourier transform infrared spectroscopy (FTIR) studies confirmed the presence of strong metal-oxygen bonds. The elastic properties of the materials in both the methods were estimated by FTIR studies. Magnetic properties namely saturation magentization, remanent magnetization and coercivity values were decreased with increase in Cr3+ ions concentration. The dielectric properties of the samples decreased with increase in the Cr3+ ions. The dielectric constant was observed to be of the order of 106 at low frequency and almost 1 at higher frequency range. The activation energy estimated using Arrhenius plots was of the order of 0.182 eV and 0.368 eV respectively for the compounds prepared by solution combustion and hydrothermal methods. The emission spectra of the samples excited at 344 nm were reported using photoluminescence (PL) spectroscopy. Further, the approximate energy band gap(Eg) was estimated from PL studies. The Eg of the materials were lie in the range of 2.11–1.98 eV.

Synthesis and characterization of nanocrystalline zinc ferrite spinel powders by homogeneous precipitation method

Single-phase nanocrystalline zinc ferrite (ZnFe2O4) spinel powders have been successfully synthesized by an easy homogeneous precipitation method in short precipitation time at low calcination temperature (250°C). Characterization of the synthesized samples were carried out by powder X-ray diffraction, thermal gravimetric analysis, Fourier transform infrared spectroscopy, diffuse reflectance spectroscopy, surface area measurements, field emission scanning electron microscopy coupled with energy dispersive X-ray analysis and transmission electron microscopy. The spinel ZnFe2O4 powders consist of spherical nanoparticles with an average size of 5.2±0.61nm. The antifungal activity of the nanocrystalline zinc ferrite powders was tested against pathogenic Candida albicans using the disc-diffusion susceptibility method. The nanocrystalline zinc ferrite powders exhibit strong antifungal activity against pathogenic C. albicans.

Nanocrystalline zinc ferrite films studied by magneto-optical spectroscopy

Ferrimagnetic Zn-ferrite (ZnFe2O4) films can be grown with the ferromagnetic resonance linewidth of 40 Oe at 9.5 GHz without going through a high temperature processing. This presents interest for applications. The work deals with laser ablated ZnFe2O4 films deposited at O2 pressure of 0.16 mbar onto fused quartz substrates. The films about 120 nm thick are nanocrystalline and their spontaneous magnetization, 4πMs, depends on the nanograin size, which is controlled by the substrate temperature (Ts). At Ts ≈ 350 °C, where the grain distribution peaks around ∼20–30 nm, the room temperature 4πMs reaches a maximum of ∼2.3 kG. The films were studied by magnetooptical polar Kerr effect (MOKE) spectroscopy at photon energies between 1 and 5 eV. The complementary characteristics were provided by spectral ellipsometry (SE). Both the SE and MOKE spectra confirmed ferrimagnetic ordering. The structural details correspond to those observed in MgFe2O4 and Li0.5Fe2.5O4 spinels. SE experiments confirm the insulator behavior. The films display MOKE amplitudes somewhat reduced with respect to those in Li0.5Fe2.5O4 and MgFe2O4 due to a lower degree of spinel inversion and nanocrystalline structure. The results indicate that the films are free of oxygen vacancies and Fe3+-Fe2+ exchange.

Oriented nanometric aggregates of partially inverted zinc ferrite: One-step processing and tunable high-frequency magnetic properties

In this work, it is demonstrated that the in situ growth of oriented nanometric aggregates of partially inverted zinc ferrite can potentially pave a way to alter and tune magnetocrystalline anisotropy that, in turn, dictates ferromagnetic resonance frequency (fFMR) by inducing strain due to aggregation. Furthermore, the influence of interparticle interaction on magnetic properties of the aggregates is investigated. Mono-dispersed zinc ferrite nanoparticles (<5 nm) with various degrees of aggregation were prepared through decomposition of metal-organic compounds of zinc (II) and iron (III) in an alcoholic solution under controlled microwave irradiation, below 200 °C. The nanocrystallites were found to possess high degree of inversion (>0.5). With increasing order of aggregation in the samples, saturation magnetization (at 5 K) is found to decrease from 38 emu/g to 24 emu/g, while coercivity is found to increase gradually by up to 100% (525 Oe to 1040 Oe). Anisotropy-mediated shift of fFMR has also been measured and discussed. In essence, the result exhibits an easy way to control the magnetic characteristics of nanocrystalline zinc ferrite, boosted with significant degree of inversion, at GHz frequencies.

Influence of Temperature on Reducing Gas Sensing Performance of Nanocrystalline Zinc Ferrite

Pure phase, zinc ferrite (ZnFe2O4) nanoparticles were synthesized at lower temperature (80 °C) by auto combustion synthesis method. The resulting ‘as synthesized’ powder was heat treated (HT) at 560 °C for 2 h in air atmosphere. As-synthesized particles had sizes ~10 nm with spherical shape. Further, these spherically shaped nanoparticles tended to change their morphology to hexagonal plate shape with increasing HT temperature. The band gap of the ‘as synthesized’ and HT zinc ferite, as determined by using UV–Vis spectroscopy were found to be 1.92 and 1.86 eV respectively. Gas responses of the ZnFe2O4 nanoparticles were measured by exposing them to ethanol gas vapors. It was found that the zinc ferrite nanoparticles exhibited various sensing responses to ethanol gas at different operating temperature. The best sensitivity was observed at low temperature for ‘as synthesized’ ferrite nanoparticles than HT zinc ferrite nanoparticles. Sensing material that had smaller particle size and larger specific surface area was observed to have larger gas sensitivity and vice-versa.

Cr3+-substitution induced structural reconfigurations in the nanocrystalline spinel compound ZnFe2O4 as revealed from X-ray diffraction, positron annihilation and Mössbauer spectroscopic studies

In an earlier work, the substitution of Zn2+ ions at the tetrahedral sites of nanocrystalline zinc ferrite (ZnFe2O4) by Ni2+ ions had been observed to cause a transformation from the normal spinel structure to the inverse one.

Effect of Particle Size on the Structural and Magnetic Properties of Nanocrystalline Zinc Ferrite

ZnFe 2 O 4 is one of the most important technological material having applications in radio engineering, radio technology, semiconductors, bio-medical applications etc. ZnFe 2 O 4 when in bulk form shows paramagnetic behavior at room temperature. When ZnFe 2 O 4 is synthesized by some techniques it was possible to see the ferromagnetic behavior. Also, ZnFe 2 O 4 in nanocrystalline form exhibit different magnetic properties. Therefore in the present work we intend to present the properties of particle size behavior of ZnFe2O4 nanoparticles. ZnFe 2 O 4 nanoparticles were synthesized by oxalic acid based precursor method. The obtained ZnFe 2 O 4 nano powders were thermally annealed from 300 to 600 °C. The structural and magnetic characterization were measured using X-ray diffraction (XRD), scanning electron microscope (SEM), IR measurements and vibrating sample magnetometer (VSM). XRD patterns clearly showed the formation of zinc ferrite. The particle size was observed to increase from 19 to 35 nm with increasing annealing temperature. The lattice constants were observed to decrease with increasing particle size. The nanoparticles size were confirmed using SEM measurements. IR measurements were carried to confirm the phase formation of ZnFe 2 O 4 nanoparticles. The Infrared spectra showed the characteristic features of vibrational bands corresponding to spinel ferrite. Room temperature ferromagnetic properties were observed for zinc ferrite having particle sizes 19 and 21 nm. For the particle size 29 and 35 nm it showed paramagnetic nature. The magnetic properties of zinc ferrite nanoparticles were observed to be dependent on the particle size. Keywords: Nanoferrites Zn ferrite Structural properties Magnetic properties

Role of mode of heating on the synthesis of nanocrystalline zinc ferrite

In the present work, microwave-assisted coprecipitation route was used for synthesis of nanocrystalline zinc ferrite and results were compared with conventionally prepared zinc ferrite. Synthesis conditions were kept uniform in both cases, except that the mode of heating was changed. The effects of mode of heating on the material properties were studied systematically. Microstructures of both samples were studied by scanning electron microscopy and transmission electron microscopy and the particle size was found to be in the range of 3–4 nm. Particle size distribution in microwave-processed MS-ZnFe2O4 is found to be highly uniform compared to conventionally processed samples (CS-ZnFe2O4). XRD data confirmed the presence of single-phase face-centered cubic structure for both the samples. The XRD data fitted well with Reitveld refinement. The functional groups were analyzed by FT-IR. Local distortions in the structures were studied by FT-Raman spectra of zinc ferrites at room temperature. This study concludes that the microwave-assisted synthesis route reduced the time of reaction by around 23 h and developed uniformly distributed fine-scaled particles. This method has high potential to synthesize other ferrite materials also.

Activation behavior and dielectric relaxation of nanocrystalline zinc ferrite

We report the ac conductivity and dielectric relaxation studies of nanocrystalline zinc ferrite prepared by the ball milling. The real part of the complex ac conductivity is found to follow the universal dielectric response σ′(f)∝Tnfs and values of both s and n show an anomalous behavior. Both the magnitude of the temperature exponent ‘n’ and thermal activation energy for ac conduction strongly depends on frequencies. The dielectric constant exhibits strong temperature dependence at higher temperature and lower frequencies. The dielectric properties of the samples have been analyzed in terms of electric modulus vector. The complex impedance has also been modeled by an ideal equivalent circuit consisting of grain and grain boundary resistances and capacitances. Considering the formation of Schottky diode at the metallic electrode and semiconductor junction, the diode parameters like built in voltage and space charge density have been extracted from the capacitance-voltage characteristics.

High frequency dielectric response and magnetic studies of Zn1−xTbxFe2O4 nanocrystalline ferrites synthesized via micro-emulsion technique

Tb3+-doped nanocrystalline zinc ferrites with a nominal composition of Zn1−xTbxFe2O4 (x=0, 0.03, 0.06, 0.09, 0.12 and 0.15) were prepared by micro-emulsion method and were annealed at 600°C for 8.5h. The synthesized samples were characterized by thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) and dielectric measurement techniques. The powder XRD patterns confirm the single phase cubic spinel structure, indicated that doping nanoferrites with small concentrations of terbium ions allowed their entrance to the spinel lattice and the crystallite size is found in the range of 16–24nm. The dielectric constant (ε) and dielectric loss (tanδ) of all the samples were measured in the frequency range 100MHz–3GHz at room temperature. The dielectric constant and dielectric loss of the samples are found to decrease with increase in frequency and Tb3+ content. The reduction in the dielectric parameters is attributed to the obstruction incorporated in electron exchange mechanism caused by the lockup among iron and terbium cations. The magnetic properties revealed that these terbium doped nanocrystalline zinc ferrites exhibit ferrimagnetic behavior. The high saturation magnetization and coercivity along with smaller dielectric parameters having Tb-contents suggests that the materials are suitable for applications in memory devices and high frequency applications.