Impact of grain size and structural changes on magnetic, dielectric, electrical, impedance and modulus spectroscopic characteristics of CoFe2O4nanoparticles synthesized by honey mediated sol-gel combustion method

In this work CoFe2O4spinel ferrite nanoparticles were synthesized by honey mediated sol-gel combustion method and further annealed at higher temperature 500 °C, 700 °C, 900 °C and 1100 °C. The synthesized spinel ferrite nanoparticles is investigated by x-ray diffraction, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), field emission scanning electron microscopy, x-ray photoelectron spectroscopy and vibrating sample magnetometer. The x-ray diffraction study reveals face-centered cubic spinel cobalt ferrite crystal phase formation. The crystallite size and lattice parameter are increased with annealing temperature. Raman and Fourier transform infrared spectra also confirm spinel ferrite crystal structure of synthesized nanoparticles. The existence of cation at octahedral and tetrahedral site in cobalt ferrite nanoparticles is confirmed by x-ray photoelectron spectroscopy. Magnetic measurement shows increased saturation magnetization 74.4 emu g-1at higher annealing temperature 1100 °C, high coercivity 1347.3 Oe at lower annealing temperature 500 °C, and high remanent magnetization 32.3 emu g-1at 900 °C annealing temperature. The magnetic properties of synthesized ferrite nanoparticles can be tuned by adjusting sizes through annealing temperature. Furthermore, the dielectric constant and ac conductivity shows variation with frequency (1-107Hz), grain size and cation redistribution. The modulus spectroscopy study reveals the role of bulk grain and grain boundary towards the resistance and capacitance. The cole-cole plots in modulus formalism also well support the electrical response of nanoparticles originated from both grain and grain boundaries. The dielectric, electrical, magnetic, impedance and modulus spectroscopic characteristics of synthesized CoFe2O4spinel ferrite nanoparticles demonstrate the applicability of these nanoparticles for magnetic recording, memory devices and for microwave applications. © 2017 Vietnam Academy of Science & Technology.LO1504, NPU, Northwestern Polytechnical Universit

Effect of Pr3+ substitution on structural and magnetic properties of CoFe2O4 spinel ferrite nanoparticles

In this paper, CoFe2-xPrxO4 (x = 0.00 to 0.1 in step of 0.025) nanoparticles were synthesized by starch-assisted sol-gel auto-combustion method. Powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, infrared spectroscopy and vibrating sample magnetometer (VSM) were employed to characterize these synthesized CoFe2-xPrxO4 nanoparticles. The structural phase purity, crystallite size, and lattice parameter of synthesized CoFe2-xPrxO4 ferrite nanoparticles were estimated from X-ray diffraction studies. XRD patterns reveal the formation of cubic spinel ferrite with the signature of PrFeO3 phase at higher Pr3+ concentration. FE-SEM images endorse that the synthesized nanoparticles are of spherical morphology with size in the range of 5-20 nm. Raman and Fourier transform infrared (FTIR) spectra support the formation of the spinel Co-Fe-Pr ferrite structure in the nanocrystalline form. Room temperature magnetic measurement shows increase in saturation magnetization and coercivity, from 13.96 emu g(-1) (x = 0.0) to 19.34 emu g(-1) (x = 0.075) and 52.30 Oe (x = 0.0) to 546.94 Oe (x = 0.075), respectively, in CoFe2-xPrxO4 nanoparticles synthesized by starch-assisted sol-gel auto-combustion methodMaterials Research Centre, Brno University of Technology [CZ.1.07/2.3.00/30.0005]; project Centre of Polymer Systems at Tomas Bata University in Zlin, Czech Republic [CZ.1.05/2.1.00/03.0111

Structural, magnetic, dielectric, and electrical properties of NiFe2O4 spinel ferrite nanoparticles prepared by honey-mediated sol-gel combustion

In this study, NiFe2O4 nanoparticles were synthesized using a honey-mediated sol-gel combustion method. The synthesized nanoparticles and samples annealed at 800 °C and 1100 °C were characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM). XRD and Raman spectroscopy confirmed the formation of a cubic spinel ferrite structure. FE-SEM demonstrated the octahedral morphology of the NiFe2O4 spinel ferrite nanoparticles with sizes ranging from 10 to 70 nm. Quantitative analysis based on XPS suggested a mixed spinel structure comprising NiFe2O4 nanoparticles. XPS analysis determined occupation formulae of (Ni0.21 2+Fe0.44 3+)[Ni0.79 2+Fe1.56 3+]O4 and (Ni0.23 2+Fe0.50 3+)[Ni0.77 2+Fe1.50 3+ ]O4 for the as-prepared NiFe2O4 nanoparticles and those annealed at 1100 °C, respectively. Magnetic measurements showed that the saturation magnetization increased with the crystallite size from 32.3 emu/g (20 nm) to 49.9 emu/g (163 nm), whereas the coercivity decreased with the crystallite size from 162 Oe (20 nm) to 47 Oe (163 nm). Furthermore, the dielectric constant, dielectric loss tangent, and AC conductivity of the NiFe2O4 nanoparticles were dependent on the frequency (1–107 Hz) and grain size. The influence of the grain size was also observed by modulus spectroscopy based on the Cole-Cole plot. © 2017 Elsevier LtdLO1504, MŠMT, Ministerstvo Školství, Mládeže a TělovýchovyMinistry of Education, Youth and Sports of the Czech Republic [LO1504

Effects of annealing temperature variation on the evolution of structural and magnetic properties of NiFe<inf>2</inf>O<inf>4</inf> nanoparticles synthesized by starch-assisted sol-gel auto-combustion method

Evolution of the structural and magnetic properties of NiFe2O4 nanoparticles synthesized by starch-assisted sol-gel auto-combustion method, and exposed to further annealing at 200 °C, 400 °C, 600 °C, 800 °C and 1000 °C, was evaluated in detail and correlation of these properties explored. The ferrite nanoparticles were characterized by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy, Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy and Vibrating Sample Magnetometer. The X-ray diffraction patterns demonstrated single phase formation of NiFe2O4 spinel ferrite nanoparticles at different annealing temperature 200 °C, 400 °C, 600 °C, 800 °C and 1000 °C. The change in crystallite size with increase of annealing temperature is observed. The FE-SEM analysis also indicated an increase of particle size with increase of higher annealing temperature. The change in Raman modes and infrared absorption bands were noticed with change of particle size. The X-ray photoelectron spectroscopy revealed the presence of Ni2+ and Fe3+ at octahedral and tetrahedral sites in NiFe2O4 nanoparticles. The representative sample NiFe2O4 nanoparticles annealed at 400 C, have mixed cation distribution (Formula presented.). The highest value of coercivity 62.35 Oe and saturation magnetization 34.10 erg/g were obtained at annealing temperature 600 °C and 1000 °C, respectively. © 2015 Elsevier B.V.Project Excellent Teams at the Materials Research Centre, Brno University of Technology [CZ.1.07/2.3.00/30.0005]; Project Centre of Polymer Systems at Tomas Bata University in Zlin, Czech Republic [CZ.1.05/2.1.00/03.0111

Cation migration-induced crystal phase transformation in copper ferrite nanoparticles and their magnetic property

Impact of crystal phase evolution on structural and magnetic properties of copper ferrite nanoparticles is studied and reported. The copper ferrite nanoparticles were synthesized by starch-assisted sol-gel auto-combustion method and further annealed at 200, 500, 800, and 1100°C. The X-ray diffraction study indicated phase evolution from cubic to tetragonal with increase of annealing temperature. Raman spectroscopy and Fourier transform infrared spectroscopy study revealed the impact of phase transformation and cation redistribution in copper ferrite nanoparticles with increase of annealing temperature. X-ray photoelectron study revealed the cation migration with annealing temperature, which is responsible for structural phase evolution. The field emission-scanning electron microscopy (FE-SEM) study revealed that the ferrite nanoparticles at a lower annealing temperature (200, 500, and 800°C) were agglomerated spherical and elongated particles in the grain size range 10–100 nm. However, at a higher annealing temperature (1100°C), it was hexagonal plate-like particles in the grain size range 50–200 nm. The increase in saturation magnetization (Ms) from 11.60 emu/g (200°C) to 25.48 emu/g (1100°C) with grain growth and crystal phase evolution (i.e., increase of c/a ratio and cation redistribution in CuFe2O4 mixed spinel ferrite) was noticed. In addition, a crystal phase evolution from cubic to tetragonal and a grain growth as a function of annealing temperature both cause also an increase in coercivity (Hc) value from 132.56 Oe (200 °C) to 1442.50 Oe (800 °C) Furthermore, the decrease of coercivity (Hc) value from 1442.50 Oe (800°C) to 218.06 Oe (1100°C) with increase of annealing temperature was due to the “pinning” effect of domain wall at the grain boundary. © 2015, Springer Science+Business Media New York.European Project Excellent Teams [CZ.1.07/2.3.00/30.0005, REG LO1211]; Program of National Program of Sustainability I (The Ministry of Education, Youth and Sports) at The Materials Research Centre, Faculty of Chemistry, Brno University of Technology; Project Centre of Polymer Systems at Tomas Bata University in Zlin, Czech Republic [CZ.1.05/2.1.00/03.0111

Structural, Cation Distribution, and Magnetic Properties of CoFe2O4 Spinel Ferrite Nanoparticles Synthesized Using a Starch-Assisted Sol-Gel Auto-Combustion Method

In this article, cobalt ferrite nanoparticles were synthesized using a starch-assisted sol-gel auto-combustion route. The significant role played by further annealing temperatures of 300, 500, 700, 900 and 1100 A degrees C on particle size and magnetic properties of ferrite nanoparticles was explored and reported. The prepared nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, using a vibrating sample magnetometer. The X-ray diffraction patterns demonstrated singlephase formation of CoFe2O4 spinel ferrite nanoparticles at different annealing temperatures. The FESEM analysis indicated a change of particle size and morphology at higher annealing temperature. The change in Raman modes and infrared absorption bands was observed with change of particle size and cation distribution. The highest value of coercivity (1091.2 Oe) and the saturation magnetization (54.76 erg g(-1)) were obtained at annealing temperatures of 900 and 1100 A degrees C, respectively. X-ray photoelectron spectroscopy revealed the presence of Co2+ and Fe3+ at octahedral and tetrahedral sites in CoFe2O4 nanoparticles. Further, the cation redistribution with change of particle size was confirmed by X-ray photoelectron spectroscopy.Project Excellent Teams at the Materials Research Centre, Brno University of Technology [CZ.1.07/2.3.00/30.0005]; Project Centre of Polymer Systems at Tomas Bata University in Zlin, Czech Republic [CZ.1.05/2.1.00/03.0111

Impact of Nd3+ in CoFe2O4 spinel ferrite nanoparticles on cation distribution, structural and magnetic properties

Nd3+ doped cobalt ferrite nanoparticles have been synthesized by starch-assisted sol-gel auto-combustion method. The significant role played by Nd3+ added to cobalt ferrite in changing cation distribution and further in influencing structural and magnetic properties, was explored and reported. The crystal structure formation and crystallite size were studied from X-ray diffraction studies. The microstructural features were investigated by field emission scanning electron microscopy and transmission electron microscopy that demonstrates the nanocrystalline grain formation with spherical morphology. An infrared spectroscopy study shows the presence of two absorption bands related to tetrahedral and octahedral group complexes within the spinel ferrite lattice system. The change in Raman modes in synthesized ferrite system were observed with Nd3+ substitution, particle size and cation redistribution. The impact of Nd3+ on cation distribution of Co2+ and Fe3+ at octahedral and tetrahedral sites in spinel ferrite cobalt ferrite nanoparticles was investigated by X-ray photoelectron spectroscopy. Room temperature magnetization measurements showed that the saturation magnetization and coercivity increase with addition of Nd3+ substitution in cobalt ferrite. © 2015 Elsevier B.V. All rights reserved.Ministry of Education, Youth and Sports [CZ.1.07/2.3.00/30.0005, LO1211]; Project Centre of Polymer Systems at Tomas Bata University in Zlin, Czech Republic [CZ.1.05/2.1.00/03.0111

Structural, dielectric, electrical and magnetic properties of CuFe2O4 nanoparticles synthesized by honey mediated sol–gel combustion method and annealing effect

In this work, CuFe2O4 nanoparticles were synthesized by natural source of glucose and fructose (i.e., honey)—mediated sol–gel auto-combustion method. Grain size, cation distribution and crystal phase were further tuned through annealing at higher temperature 500, 700, 900 and 1100 °C. The structural investigation was performed using powder X-ray Diffraction, Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy and X-ray Photoelectron Spectroscopy. X-ray diffraction study confirmed the phase transformation from cubic to tetragonal as a function of annealing temperature. Magnetic properties were investigated by using vibrating sample magnetometer under an applied magnetic field of 10 kOe at room temperature. The highest value of saturation magnetization (Ms) was 26 emu/g for ferrite nanoparticles annealed at 1100 °C, whereas the lowest value was 11 emu/g for annealed at 700 °C. The highest and lowest coercivity (Hc) was 1389 and 65 Oe for ferrite nanoparticles annealed at 900 and 1100 °C, respectively. Detailed study of modulus and impedance spectroscopy revealed the contribution of grain and grain boundary on electrical transport mechanism and relaxation process. Further, dependence of relaxation time, resistance and capacitance at grain and grain boundary on grain size, cation distribution and annealing temperature was noticed. The asymmetry of peak in imaginary part of modulus spectra indicates that the relaxation process is non-Debye type. At lower frequency, ac conductivity is frequency independent, whereas, at high frequency, it follows an apparent power law, σ(ω) α ωs. Dielectric parameters (real and imaginary part, dielectric loss) with variation of frequency (1 Hz to 10 MHz) are investigated and dependence with frequency and annealing temperature is observed. © 2017, Springer Science+Business Media New York.Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504

Structural and Magnetic Properties of CoFe2-x Gd (x) O-4 (0.0 a parts per thousand currency sign x a parts per thousand yen 0.1) Spinel Ferrite Nanoparticles Synthesized by Starch-Assisted Sol-Gel Auto-combustion Method

In this present article, CoFe2-x Gd (x) O-4 (0.0 a parts per thousand currency sign x a parts per thousand yen 0.1) nanoparticles were synthesized by starch-assisted sol-gel auto-combustion method. Powder X-ray diffraction patterns revealed the formation of cubic spinel ferrite with the signature of GdFeO3 phase at higher Gd3+ concentration. The field emission scanning electron microscopy study demonstrated the spherical nanoparticle in the size range 4-10 nm. Raman and Fourier transform infrared spectra supported the formation of the spinel ferrite structure in the nanocrystalline form. The X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of Co2+ and Fe3+ at the octahedral site as well as the tetrahedral site in CoFe2-x Gd (x) O-4 (x = 0.05) nanoparticles. The distribution of Fe3+ ions was obtained to be about 73 % in the octahedral sites and about 27 % in the tetrahedral sites. The distribution of Co2+ ions at the octahedral and tetrahedral sites were 78 and 22 %, respectively. The increase in saturation magnetization and coercivity from 14.59 emu/g (x = 0.00) to 16.11 emu/g (x = 0.025) and 51.75 Oe (x = 0.00) to 92.86 Oe (x = 0.050), respectively, in CoFe2-x Gd (x) O-4 nanoparticles were observed.Project Excellent Teams at the Materials Research Centre, Brno University of Technology [CZ.1.07/2.3.00/30.0005]; project Centre of Polymer Systems at Tomas Bata University in Zlin, Czech Republic [CZ.1.05/2.1.00/03.0111

Structural, magnetic, elastic, dielectric and electrical properties of hot-press sintered Co1−xZnxFe2O4 (x = 0.0, 0.5) spinel ferrite nanoparticles

In this article, Co1−xZnxFe2O4 (x = 0.0 and 0.5) disc-shaped pellets were formed by hot-press sintering of nanoparticles at temperature 925 °C for 10 min in vacuum atmosphere under 30 MPa mechanical pressure. X-ray diffraction study confirmed the formation of spinel cubic ferrite structure of hot-press sintered spinel ferrite Co1−xZnxFe2O4 (x = 0.0 and 0.5) samples. The scanning electron microscopy image indicated that the growth and densification of smaller ferrite nanoparticles were higher than larger ferrite nanoparticles. Magnetic properties of sintered samples were investigated by the superconducting quantum interface device (SQUID) magnetometer at room temperature. The hot press sintered Co1−xZnxFe2O4 (x = 0.0 and 0.5) pellet samples exhibited magnetic properties dependent on the grain size of spinel ferrite particles. The maximum saturation magnetization 82.47 emu/g was obtained for Co0.5Zn0.5Fe2O4 hot press sintered sample of ball-milled ferrite particles. Further, the impact of grain size and density of sample on hardness, dielectric property and ac conductivity of hot-press sintered samples was investigated. In addition, the longitudinal wave velocity (Vl), transverse wave velocity (Vt), mean elastic wave velocity (Vm), bulk modulus (B), rigidity modulus (G), Young's modulus (E), Poisson ratio (σ) and Debye temperature (θD) were calculated. The elastic moduli of hot press sintered ferrite samples were corrected to zero porosity using Hosselman and Fulrath model. © 2017 Elsevier B.V.Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504