In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol–gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual...

Solution Combustion Synthesis of Nanoscale Materials

Spinel ferrite magnetic adsorbents: Alternative future materials for water purification?

Nanoparticles exhibit unique properties that enable them to find potential applications in various fields. Accordingly, significant research attention is being given to the development of novel strategies for the synthesis of nanoparticles. Among these, biological route of nanoparticle synthesis has been portrayed as an efficient, low-cost and environmental friendly technique. Biological materials such as bacteria, fungi, yeast, algae and plant have been reported to possess high bioreduction ability to synthesize various size and shape of metallic nanoparticles. Of these biomaterials, this review focuses on plant-mediated biosynthesis of metallic nanoparticles. The biomolecules present in the plants such as terpenoids, flavones, ketones, aldehydes, proteins, amino acids, vitamins, alkaloids, tannins, phenolics, saponins, and polysaccharides play a vital role in reduction of metals. A systematic comparison of literature, based on the bioreduction capacity of various plant biomass/extract towards various metals under different experimental conditions, is also provided. Various instrumental techniques utilized to characterize nanoparticles are also discussed. Finally, this review also highlights the application of biosynthesized nanoparticles in different fields such as medicine, agriculture, catalytic, cosmetic and food. Thus, this article reviews the achievements and current status of plant-mediated biosynthesis, and hopes to provide insights into this exciting research frontier.

Plant-mediated biosynthesis of metallic nanoparticles: A review of literature, factors affecting synthesis, characterization techniques and applications

Nanoparticles of CoFe2O4 and CoIn0.15Fe1.85O4 ferrites were prepared by citrate gel route and characterized to understand their structural, electrical, and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase cubic spinel structure. The average grain sizes from the Scherrer formula were below 50 nm. Microstructural features were obtained by scanning electron microscope and compositional analysis by energy dispersive spectroscopy. The hysteresis curve shows enhancement in coercivity while reduction in saturation magnetization with the substitution of In3+ ions. Enhancement of coercivity is attributed to the transition from multidomain to single domain nature. Electrical properties, such as dc resistivity as a function of temperature and ac conductivity as a function of frequency and temperature were studied for both the samples. The activation energy derived from the Arrhenius equation was found to increase in the doped sample. The dielectric cons...

Magnetic and electrical properties of In doped cobalt ferrite nanoparticles

The Zn substituted cobalt ferrite nanoparticles having the generic formula Co1−xZnxFe2O4 (x=0.0–0.7) were prepared by wet chemical coprecipitation technique using analytical reagent (AR) grade sulphates. The prepared samples were heated at 150 °C to remove water molecules and then annealed at 725 °C for 16 h. Investigation of the structural properties were carried out using x-ray diffraction, transmission electron microscopy (TEM), and scanning electron microscopy techniques. The nanocrystalline nature of the samples is confirmed by TEM data. Substitution of the nonmagnetic Zn2+ ions considerably changes the magnetic properties. Neel’s model fails to explain the observed magnetic behavior above x=0.2. For x≥0.2 the Yafet–Kittel model can be fitted. AC susceptibility measurements confirm the decrease in Curie temperature.

Effect of Zn substitution on magnetic properties of nanocrystalline cobalt ferrite

Ferrite samples of Al3+ substituted NiFe2O4 nanoparticles were prepared by wet chemical co-precipitation method. The samples were obtained by annealing at relatively low temperature at 600 °C and characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and ac susceptibility. On applying the full pattern fitting of Rietveld method using FullProf program, exact coordinates of atoms, unit cell dimensions, atom ion occupancy, degree of inversion as well as crystallite size and residual microstrain have been determined. The lattice parameter, density, particle size, lattice strain, magnetization, magneton number, and Curie temperature are seen to decrease with increasing A13+ content whereas the specific surface area, porosity, coercive force, shows an increasing trend with A13+ content. Cation distribution is obtained from XRD and Rietveld method and the variation of the cation distribution has been discussed on ...

Rietveld structure refinement, cation distribution and magnetic properties of Al3+ substituted NiFe2O4 nanoparticles

The magnetic and electrical properties of Cr3+ substituted nickel ferrite synthesized by wet chemical route have been studied Particle size measured from x-ray diffraction and from transmission electron microscopy images confirms the nanosize dimension of prepared particles Magnetic parameters such as coercivity and saturation magnetization are measured from vibrating sample magnetometer Magnetization, ac susceptibility, electrical resistivity, and Mossbauer measurements were carried out Electrical properties such as ac resistivity as a function of frequency and dc resistivity as a function of temperature were studied for various Cr3+ substitutions in nickel ferrite The dielectric properties such as dielectric constant (e′) and dielectric loss (e″) were also studied The dielectric constant and dielectric loss obtained for the ferrites prepared through wet chemical route posses a value lower than that of the ceramically prepared samples of the same composition The resistivity obtained is higher than

Electrical and magnetic properties of Cr3+ substituted nanocrystalline nickel ferrite

CoCrxFe2–xO4 (0 ≤ x ≤ 1.0) was synthesized by sol–gel auto combustion method using nitrates of respective elements and by keeping 1:3 ratio of metal nitrate to citrate. Representative sample was in...

Santosh S. Jadhav

Papers

Effect of Zn substitution on magnetic properties of nanocrystalline cobalt ferrite

Rietveld structure refinement, cation distribution and magnetic properties of Al3+ substituted NiFe2O4 nanoparticles

Electrical and magnetic properties of Cr3+ substituted nanocrystalline nickel ferrite

Autocombustion High-Temperature Synthesis, Structural, and Magnetic Properties of CoCrxFe2–xO4 (0 ≤ x ≤ 1.0)

Ferrites Obtained by Sol–Gel Method