Nanocrystalline ZnFe2O4 Research Articles

Cationic disorder: Governing the spin-insulatronic properties of nanocrystalline ZnFe2O4 thin films

Controlling cation order/disorder in spinel offers a highly effective means of tailoring material properties by modifying inter- and intra-sub-lattice ionic interactions. In this study, we conducted high-temperature magnetization measurements (300–1000 K) to determine average Curie temperatures (TC) for nanocrystalline ZnFe2O4 thin films. Thermodynamical stability of these films under extreme conditions was investigated by assessing lattice structures, oxygen vacancies, magnetization, and electric resistivity for spin-insulatronic applications. Reversible cation inversion via heat treatments (in-situ and ex-situ) yields tunable ferrimagnetic (FiM) order in ZnFe2O4, with TC ranging from 425 to 710 K. First-principles calculations highlight effective cation inversion mitigating magnetic frustration, promoting collinear FiM ordering, and elevating TC. Oxygen vacancies further reinforce ferrimagnetism, slightly reducing resistivity through the formation of Fe-3d gap states near the Fermi level. A proposed magnetic nanophase diagram elucidates dominant competing magnetic ground states (cluster spin-glassy state, FiM, and antiferromagnetic) with increasing growth temperature, fostering innovative homo-architectures from multiple ZnFe2O4 thin films with diverse functionalities.

Broadening of magnetocaloric effect at elevated temperatures in nanocrystalline ZnFe2O4 thin films

The detection and characterization of the Magnetocaloric Effect (MCE) at the nanoscale and its subsequent impact on next-generation cooling on-chip devices are of paramount importance. Here, we demonstrate that the MCE properties housed within a ferrimagnetic phase arise in disordered ZnFe2O4. The robustness of the MCE in terms of magnetic entropy change ΔSmax (=0.07–0.09 J/kg-K at 0.5 T) emerges in ZnFe2O4 thin films at larger temperature ranges 425–710 K, reaching above room temperature. By fitting the magnetization vs. temperature curves with a Gaussian-type distribution, we observed a correlation between the broadening of the MCE peak, Curie temperature (TC) distribution, and grain size distributions in nanocrystalline ZnFe2O4 thin films. The width of TC distributions increases (up to 150 K) and consequently, the ΔS curves show an extended full width at half maximum, resulting in larger relative cooling power (RCP), and a wider change in specific heat capacities (ΔCP) and adiabatic temperatures (ΔTad). This study reveals that tuning the relative strengths of the sublattice spin configuration of antiferromagnetic (AFM) ZnFe2O4 through in-situ and ex-situ heat treatment paves the way for the alteration of MCE properties.

Tailoring the structural and dielectric properties of ZnFe2O4 through annealing temperature

In this study, we synthesized nano-crystalline ZnFe2O4 through the sol-gel method and explored the impact of annealing temperature on its physical properties. The average crystallite size, determined using the Debye-Scherres's formula with data obtained from Rietveld-refined X-ray diffraction, increased from 16 nm to 58 nm as the annealing temperature rose from 200 to 1000 K. FTIR spectra showcased vibrational modes corresponding to metal-oxygen bonds at both octahedral and tetrahedral sites. UV–Vis DRS measurements uncovered a widening of the optical band gap from 2.03 eV to 2.14 eV with increasing annealing temperatures. The rearrangement of cations exerted a substantial influence on the dielectric properties and AC conductivity. Dielectric assessments illustrated a diminishing trend in both the real and imaginary components of impedance as frequency progressed, decreasing from 107 at 100 Hz to 10 at 100 MHz. Additionally, conductivity investigations emphasized that the AC conductivity of ZnFe2O4 experiences enhancement at higher frequencies.

Rapid microwave-assisted combustion route for production of MFe2O4 (M = Zn, Ni, Co) nanoferrites for gas sensors view point

Nanocrystalline ZnFe2O4, NiFe2O4 and CoFe2O4 were prepared using rapid microwave assisted combustion technique. Single phase Nanocrystalline structure of ferrites confirmed by X-ray diffraction and Rietveld refinement. Fine powder of Nanocrystalline Zn, Ni and Co ferrites resulted from rapid synthesis route were used for gas sensor fabrication in the form of thick film by screen printing method. Scanning electron microscopy was used to study surface of the sensing element and to study the surface morphology of the sensor. The gas sensing responses of the indigenously built sensor were analyzed by measuring the resistance of sensing element in presence and in absence of LPG. Amongst the studied sensors, NiFe2O4 thick film sensor showed superior response.

Structural Properties and Cation Distribution in Co2+ and Ho3+ Ions Induced Nanocrystalline ZnFe2O4

Nanocrystalline CoyZn1-yHozFe2-zO4 (where y = 0.0, 0.25, 0.5, 0.75, 1.00 and z=0.0, 0.03, 0.06, 0.08, 0.1) ferrites were prepared by sol-gel auto combustion method at pH of 8. Samples were obtained by annealing at relatively low temperature 600 °C for 4 h and characterized by thermo gravimetric/differential thermal analysis (TG/DTA) all the samples were annealed at 600 °C for 4 h. The prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. Particle size measured from XRD and TEM are in good agreement with each other. The TEM study reveals the fine particle nature of the ferrites with little agglomerations. The cation distribution suggests that Zn2+ ion mainly on tetrahedral-A sites, Ho3+ ions shows strong preference towards octahedral-B site, Co2+ and Fe3+ ions are randomly distributed at the tetrahedral-A and octahedral-B site. FT-IR study confirmed two main absorption bonds in the frequency range 400-600 cm-1, assigned due to the tetrahedral-A and octahedral-B stretching vibrations.

Synergetic effect of thermal and electromagnetic energy on electrical properties of zinc ferrite thin film

In this study, the nanocrystalline ZnFe2O4 thin films were deposited using spray pyrolysis technique. The structure, morphology, and optical and electrical properties of the sample were analyzed. The film shows higher conductivity for selective illumination having wavelength corresponding to the bang gap energy. In case of thermal excitation the rapid increase in conductivity was observed after 500 K. The combined exposure of heat and light affects the conductivity without changing activation energy of the material.

Influence of Particle Size on the Electrical Properties and Magnetic Field Dependent I–V Characteristics of Nanocrystalline ZnFe2O4

ABSTRACTThe influence of grain size (7-16 nm) on electrical conductivity, dielectric properties and magnetic field dependent I–V characteristics along with magnetoresistance have been studied for zinc ferrite ( ZnFe 2O4). ZnFe2O4 was prepared by co-precipitation technique. Ball milling on the chemical routed material was carried out to control the particle size. The effect of particle size on the conduction mechanism was investigated by nonlinear least-squares fitting of the impedance spectrum. The electrical response was found to be strongly influenced by the particle size of the material. Electrical conductivity decreased with decrease of particle size. Electrical conductivity (σ) significantly changed with temperature indicating thermal activated conductivity mechanism. I–V characteristics of the material showed variation of resistance with magnetic field, indicating existence of magnetoresistance (MR). The exhibition of I–V loops confirmed the existence of two irreversible electronic states (bi-stable states: LRS and HRS) in the material, which helped to extract information about non-volatile electronic states and electrical power loss (loop area) in presence of magnetic field. The I–V loop repetition for 20 times within bias voltage range ±20 V gave the information about the stability of the current variation with bias voltage.

Removal of Evans Blue dye from aqueous solution using magnetic spinel ZnFe2O4 nanomaterial: Adsorption isotherms and kinetics

Magnetic nano crystalline ZnFe2O4 was successfully synthesized by simple combustion route using oxalyldihydrazine as fuel and the material formed was characterized by powder X-ray diffraction, Fourier transform infra-red spectroscopy and scanning electron microscope. Surface area measurements (90.004 m2 g−1) were done using Brunauer–Emmett–Teller analysis. Magnetic measurements done using vibrating sample magnetometer shows that ZnFe2O4 nanoparticle is superparamagnetic. Adsorption capability of the as prepared nanospinel ZnFe2O4 was measured for the removal of Evans Blue, an anionic dye by batch adsorption process. Parameters like adsorbent loading, initial dye concentration and stirring effects were carried out at neutral pH and room temperature. Spinel ZnFe2O4 nanoparticles showed good adsorptive capacity and the maximum monolayer coverage (Q0) was determined as 46 mg/g of the adsorbent. The data were analyzed by three different kinetic models viz; Lagergren pseudo first order, pseudo second order and Intraparticle diffusion models and by various isotherm models like Langmuir, Freundlich and Temkin models to study the mechanism of adsorption process. Kinetic study shows that it follows pseudo second order with highest R 2=0.998 and the rate determining step was found to be intraparticle diffusion. Isotherm studies shows that the adsorption of EB is highly favorable and the value of Temkin constant, AT = 0.5445 and heat of adsorption, B = 14 J/mol indicates that the adsorption process is exothermic and physical in nature.

Local structural changes of nano-crystalline ZnFe2O4 during lithiation and de-lithiation studied by X-ray absorption spectroscopy

X-ray absorption spectroscopy was carried out to investigate local structural changes around Fe and Zn atoms of the nano-crystalline spinel ferrite ZnFe2O4 anode material at various states-of-charge during the 1st and 2nd lithiation/de-lithiation. From the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), we propose a possible structure evolution process of the ZnFe2O4 electrode during the 1st discharge and charge cycle. A mixture of metallic iron, ZnO, metallic zinc, LiZn and Li2O phases seem to be formed as the cell is firstly discharged to 0.02V. Instead of the original ZnFe2O4 spinel phase, the metallic iron and zinc particles are re-oxidized to Fe2O3 and ZnO phases during the subsequent de-lithiation. A reversible redox reaction between Fe2O3, ZnO and lithium ions is found in the 2nd cycle. The formation of SEI layer in the initial cycles plays a major role in the irreversible capacity of the electrode. The inactive disordered ZnO formed due to the conversion reaction of ZnFe2O4 during the 1st lithiation is probably the main reason for the poor electrochemical behavior of the nano-crystalline ZnFe2O4 electrode.

Molten Salt Synthesis of Nanocrystalline ZnFe2O4 and Its Photocatalytic Dye Degradation Studies

Magnetically separable ZnFe2O4 photocatalyst was prepared by facile Molten Salt Method (MSS) using eutectic mixture of NaCl- KCl flux. The obtained products were characterized by Powder X-ray diffraction (XRD) and Scanning electron microscopy (SEM). XRD confirm single phase ZnFe2O4 formed at 900°C for 1 h. Crystalline size was calculated to be 50 - 90 nm using Scherrer expression. SEM micrographs shown particles crystallized in submicron range of polygonal morphology. The photocatalytic activity was evaluated for degradation of Rhodamine B (RhB) under UV irradiation, it found to show 98% of degradation.

Superconductivity and mechanical properties of SmBa2Cu3O7−δ added with nano-crystalline ZnFe2O4

The effect of nanosized ZnFe2O4 addition on the physical properties of polycrystalline SmBa2Cu3O7–δ superconductor was studied. Superconducting samples of the type (ZnFe2O4) x SmBa2Cu3O7−δ, x = 0.00, 0.01, 0.02, 0.04, 0.06, 0.08, 0.10, 0.15 and 0.20 wt% were prepared by the solid-state reaction method. The characterization and superconductivity investigation were carried out using X-ray powder diffraction, XRD, scanning electron microscope, SEM, energy-dispersive X-ray, EDX, dc electrical resistivity and transport critical current density at 77 K. Improvements in the volume fraction, superconducting transition temperature, Tc, and transport critical current density, Jc, were observed as x increased from 0.00 up to 0.08 wt% and then they decreased with further increase in nanosized ZnFe2O4 addition. The Vickers microhardness number, H v, and elastic parameters have been measured at room temperature. The ultrasonic pulse-echo technique at 4 MHz was used to determine the elastic parameters. H v and the elastic parameters were observed to increase with increasing x. The enhancement of the elastic parameters may be due to the hindrance of dislocation motion with nanosized ZnFe2O4 addition. Moreover, Debye temperatures (θ D) were calculated and it was found that their values increased with increasing nanosized ZnFe2O4 addition. The elastic parameters of the samples were computed and corrected to zero porosity using different models. Finally, the relationship between Young’s modulus and H v was estimated for different models.

Synthesis of intertwined Zn0.5Mn0.5Fe2O4@CNT composites as a superior anode material for Li-ion batteries

Nanocrystalline ZnFe2O4, Zn0.5Mn0.5Fe2O4, and Zn0.5Mn0.5Fe2O4@CNT composites have been successfully prepared by a facile and high-yield co-precipitation method. All the samples as the anode materials were characterized by X-ray diffraction, thermogravimetry, and electrochemical measurements. It has been found that the appropriate Mn doping and CNTs intertwining actively affect the formation of uniform morphology and improve the cycling stability and rate capability. The Zn0.5Mn0.5Fe2O4@CNT composites exhibit excellent electrochemical performance as the anode material, with enhanced reversible capacity (1374.8 mAh g−1 after 100 cycles at the current density of 100 mA g−1) and good rate capability (933.5 mAh g−1 at 500 mA g−1, 809.9 mAh g−1 at 1000 mA g−1, 634.2 mAh g−1 at 1500 mA g−1). We also present the crystal structure and Li-ion insertion mechanism for the above materials. Our work displays the Li storage matrix model of the ZMFO electrode which may offer a novel way for the investigation of the LIBs with excellent electrochemical performance and perfect structural stability .

Studies on the microwave assisted and conventional combustion synthesis of Hibiscus rosa-sinensis plant extract based ZnFe2O4 nanoparticles and their optical and magnetic properties

Nanocrystalline ZnFe2O4 samples were synthesized by both conventional combustion method (CCM) and microwave assisted combustion method (MCM) using Hibiscus rosa-sinensis plant extract for comparison purpose. The prepared ZnFe2O4 samples were characterized by X-ray diffraction (XRD), Rietveld analysis, Fourier transform-infrared spectrophotometer (FT-IR), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and vibrating sample magnetometer (VSM). The formation of single phase ZnFe2O4 was confirmed by XRD and FT-IR. The lattice parameter was calculated by Rietveld analysis. The change in the particle size ranges from 372.0 to 541.7nm and 23.4 to 48.5nm respectively for the conventional and microwave methods and has been clearly shown by HRSEM. UV–visible diffuse reflectance spectroscopy is used to measure the band gaps of ZnFe2O4, which is about 2.1eV. Single phase ZnFe2O4 emits the photoluminescence bands at 486, 530, 542, and 566nm. The magnetic properties of the synthesized ZnFe2O4 nanoparticles were investigated by VSM studies and the hysteresis loops were studied at room temperature. The saturation magnetization (Ms) of ZnFe2O4-CCM (63.61emu/g) is lesser than that of ZnFe2O4-MCM (255.7emu/g). ZnFe2O4 nanoparticles prepared by the microwave assisted combustion method were found to have higher surface area and lower crystallite size than ZnFe2O4 nanoparticles prepared by the conventional combustion method.

Study of Physical and Magnetic Properties of Nanocrystalline ZnFe2O4 and MnFe2O4

Study of Physical and Magnetic Properties of Nanocrystalline ZnFe₂O₄ and MnFe₂O₄

Mössbauer studies of nanocrystalline ZnFe2O4 particles prepared by spray pyrolysis method

This paper reports the synthesis and characterization of nanoparticles of Zn Fe2O4 by spray pyrolysis method. XRD studies indicates that the particle formed are ultra fine (20 nm) associated with strain. The particle size is confirmed by TEM analysis. The room temperature Mossbauer spectrum shows only a doublet which could be indicative of either paramaganetic or superparamagnetic phase. The value of isomer shift is in the range 0.34±0.01 mm/s while quadruple splitting is in the range 0.48±0.01 mm/s. A series of low temperature studies has been performed and the spectra obtained at 20 K and 5K show the presence of two well resolved sextets, which are attributed to the Fe3+ ion in the tetrahedral and octahedral sites of the spinel structure. The application of external magnetic field yields a better fitting resolution of the sub spectra between A and B sites. The temperature dependant and in-field measurements yielded valuable insights about magnetic phase (superparamagnetic), local cation distribution among A sites and B sites, inversion parameter (δ =0.74), canted spin alignment (ψA = 29.58, ψB= 48.46) and the blocking temperature (TB= 50 K).

Ferromagnetic Behavior in Zinc Ferrite Nanoparticles Synthesized using Coprecipitation Technique

Zinc ferrite have been produced and used by humans since long time, however understanding of ZnFe2O4 as a nano structured materials is very useful in order to be used for technological applications. ZnFe2O4 structural, magnetic and electrical properties are different when synthesized using different techniques. Therefore, it would be interesting to investigate the structural and magnetic properties of ZnFe2O4 when in nanosize. In the present work nanocrystalline ZnFe2O4 was synthesized using coprecipitation technique. The structural and magnetic properties of ZnFe2O4 nanopowders were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), dynamic light scattering (DLS), infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The XRD of ZnFe2O4 nanoparticles showed the single phase spinel structure. The average particle size of ZnFe2O4 calculated from XRD was observed to be 45 nm. DLS measurements showed the average particle size to be 42 nm. Further, the phase formation of ZnFe2O4 was confirmed from the IR measurements. The IR spectra showed the bands corresponding to ZnFe2O4. We observed the room temperature ferromagnetic behavior in synthesized ZnFe2O4 nanoparticles which may be due to the random distribution of Zn2+ and Fe3+ at the tetrahedral (A) and octahedral [B] sites. In our future work, we want to investigate the defect induced magnetic properties of ZnFe2O4 nanoparticles which is likely to contribute for ferromagnetic behavior in this material.

Microstructure and magnetic properties of patterned nano crystalline zinc ferrite thin film fabricated by pulse laser deposition

Patterned nano crystalline ZnFe2O4 thin film was fabricated on quartz substrate by pulse laser deposition. XRD and Raman spectroscopic techniques were employed for structural characterization of the film. Silencing of a small number of prominent ferrite XRD peaks in thin film signify mild textured film growth. The observed XRD peak position swing with respect to the target material in thin film indicates formation of lateral strain in opposite directions during film growth. The thin film XRD peak position shift with target material data as reference is explained by suggesting an appropriate film growth model. Designated ferrite Raman emission peaks originated from film surface authenticates the stoichiometric and structural stability of ferrite material. AFM images indicate specific pattern formation with nanogranular morphology. Magnetic property measurements of the thin film revealed enhanced properties which are explained on the basis of texture, lattice strain, and surface features that are originated from patterned thin film growth.

Magnetic Properties of ZnFe2O4 Nanoparticles Synthesized by Starch-Assisted Sol–Gel Auto-combustion Method

In this paper, ZnFe2O4 spinel ferrite nanoparticles with different grain sizes at different annealing temperatures have been synthesized using the starch-assisted sol–gel auto-combustion method. The synthesized nanoparticles were characterized by conventional powder X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and vibrating sample magnetometer. The X-ray diffraction (XRD) patterns demonstrated that the ZnFe2O4 nanoparticles consist of single-phase spinel structure with crystallite sizes 4.81, 8.72, 12.06, 29.32, and 72.60 nm annealed at 400, 600, 800, 1000, and 1200 °C, respectively. Field emission scanning electron microscopy reveals that particles are of spherical morphology at lower annealing temperature and hexagonal-like morphology at higher temperature. An infrared spectroscopy study shows the presence of two principal absorption bands in the frequency range around 525 cm−1 (ν 1) and around 350 cm−1 (ν 2), which indicate the presence of tetrahedral and octahedral group complexes, respectively, within the spinel ferrite nanoparticles. Raman spectroscopy study also indicated the change in octahedral and tetrahedral site-related Raman modes in zinc ferrite nanoparticles with change of particle size. The nanocrystalline ZnFe2O4 samples (4.81, 8.72, 12.06, 29.32 nm) show ferrimagnetic behavior, and bulk sample (72.60 nm) shows paramagnetic behavior. This change in magnetic behavior is due to change of cation distribution in ZnFe2O4 nanoparticles with decrease of particle size.

Rapid low-temperature synthesis of mesoporous nanophase ZnFe2O4with enhanced lithium storage properties for Li-ion batteries

In this work, a rapid low-temperature and cost-effective refluxing synthesis strategy was elegantly designed, and elaborately developed for high-yield fabrication of mesoporous nanocrystalline ZnFe2O4 with nano-scaled size of ∼7 nm, desirable mesoporosity and large specific surface area. Benefitting from these admirable nanostructured architectures, the as-derived nanophase ZnFe2O4 exhibited excellent discharge capacity of 1322 mA h g−1 on the first cycle, and showed outstanding cycling durability, rate capability, and coulombic efficiency even at high current rates when evaluated as an anode for Li-ion batteries. More importantly, a low temperature of 100 °C and short reaction time of 5 h were applied here; therefore, the efficient synthetic strategy we proposed herein is advocated for scaled-up commercial application.

Synthesis, Characterization and Vapour Sensing Properties of Nanosized ZnFe2O4

In recent years, there has been a renewed interest on spinel ferrites for their remarkable versatile applications. Among AFe2O4, zinc ferrite (ZnFe2O4) has gained special importance due to its application in gas sensing, drug delivery and magnetic resonance imaging. Nanocrystalline powder of ZnFe2O4 with average size of 25-30 nm was synthesized using citrate-gel method. Thermogravimetric analysis and XRD confirmed the formation of nanocrystalline ZnFe2O4 at 400°C. The band appearing below 700 cm–1 in the FTIR spectrum confirmed the presence of Zn(Fe-O) group. Microstructural investigation was done on SEM and TEM. The response of ZnFe2O4 towards alcohol and acetone vapour at 350°C was studied. The sample showed n-type conductivity with excellent vapour sensitivity.