Narrow Results

Superparamagnetic (SP) crystalline cobalt ferrite (CoFe₂O₄) nanoparticles are synthesized by chemical co-precipitation method. Grown nanoparticles are annealed in air at various temperatures in the range 373 K to 1173 K to understand the variation in properties in nanoregion. Physical properties are analyzed for crystalline phase, crystallite size, particle size, shape, magnetization and relaxation behavior by using various characterization techniques viz. X-ray diffractometer (XRD), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and electron paramagnetic resonance (EPR). Annealing effect on various physical properties of particles are investigated. Particles are used in the development of stable ferrofluid.

The scope of the present work is in enhancing the particle size, and dielectric properties of Mg-substituted Cobalt ferrites nanoparticles prepared by sol–gel auto combustion method. The different ratios of Mg-substituted Co Ferrites (Co${}_{1-x}$Mg_xFe₂O₄($x=0.00$, 0.05, 0.10, 0.15, 0.20 and 0.30)) are calcinated at 850${}^{\circ }$C. The synthesized nanoparticles were characterized by powder XRD, FTIR, FE-SEM, EDX techniques and dielectric behavior. The structural parameters were confirmed from powder XRD and the average particle size is obtained from 39 to 67 nm due to the substitution of Mg${}^{2+}$ which was calculated by Debye Scherrer’s formula. FE-SEM showed the surface morphology of the different ratio of the sample. The dielectric loss has measured the frequency range of 50Hz–5MHz. From electrical modulus, conductivity relaxation and thermal activation of charge carriers has been discussed.

Ferrite nanoparticles of Ni${}_{0.35}$Mn${}_{0.35}$Zn${}_{0.3}$Fe${}_{2-x}$Ce_xO₄ ferrite system were produced using sol–gel auto combustion technique. X-ray diffraction analysis confirms the single phase cubic spinel structure of the samples with space group Fd-3m. Replacement of Fe${}^{3+}$ ions by Ce${}^{3+}$ ions increases the lattice parameter 8.4105 Å to 8.4193. Average crystallite size obtained from Scherrer method varies from 21.73nm to 22.71nm with replacement of Fe${}^{3+}$ ions by Ce${}^{3+}$ ions. Williamson–Hall and strain-size plot analysis confirms the nanocrystalline nature of the samples and the micro-strain induced in the cubic crystals is of tensile type. Cation distribution suggests that Zn${}^{2+}$ ions occupy tetrahedral — A-site while Ni${}^{2+}$ ions occupy octahedral — B-site. Majority of the Mn${}^{2+}$ ions prefer A-site and majority of the Ce${}^{3+}$ ions replace Fe${}^{3+}$ ions at octahedral — B-site. High resolution transmission images confirm the homogeneity and nanoparticle nature of the samples. Two main characteristics absorption bands corresponding to spine structure are observed in the Fourier transmission infra-red spectra within the wavenumber range of 350–600cm${}^{-1}$. Stiffness constant, Young’s modulus, rigidity modulus, bulk modulus and Debye temperature were estimated using FTIR data. Debye temperature obtained from the Waldron equation varies from 676K to 692K with the addition of Ce${}^{3+}$ ions. Higher values of elastic moduli are suitable for industrial applications due to increased mechanical strength.