Effect of sintering conditions on resistivity and dielectric properties of Ni-Zn ferrites (original) (raw)
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Materials Chemistry and Physics, 2022
The influences of sintering temperature on the microstructure and giant dielectric properties of a new co-doped TiO 2 system, i.e., V and Ta co-doped TiO 2 , were investigated. The grain size of (V 1/2 Ta 1/ 2) 0.01 Ti 0.99 O 2 ceramics was enlarged with increasing sintering temperature. Dense microstructure and homogeneous dispersion of dopants were achieved in the ceramics sintered at 1400e1500 C for 5 h. The dielectric permittivity in the frequency range 40e10 6 Hz of the (V 1/2 Ta 1/2) 0.01 Ti 0.99 O 2 ceramics significantly increased with the mean grain size, while the dielectric loss tangent was reduced to 0.033 at 10 2 Hz. Furthermore, the high-temperature stability of the dielectric permittivity was improved with increasing mean grain size. The electrically heterogeneous microstructure consisting of semiconducting grains and insulating grain boundaries and/or surface layers was confirmed using impedance spectroscopy. The conduction inside the semiconducting grains was attributed to electron hopping between Ti 4þ and Ti 3þ , which was confirmed by X-ray photoelectron spectroscopy. Very high resistivity with a large conduction activation energy of the insulating parts was suggested as the primary cause of the giant dielectric permittivity with low loss tangent.
Advances in Materials Science and Engineering, 2014
This work aims to investigate the relationship between the microstructure of Ni-Zn ferrite and its electrical and magnetic properties in the presence and absence of as small amounts as 0.12% of 0.4CaO + 0.8SiO 2 over different sintering times. The X-ray diffraction pattern showed a single spinel phase formation in all the samples. The results indicate that grain growth occurred by increasing sintering time from 15 to 270 min in the two types of samples prepared in this study although it was greatly impeded by the additive oxides. Moreover, the oxides increase the resistivity of the ferrite and decrease its zinc loss. Magnetic properties such as induction magnetization ( ) and saturation magnetization ( ) decreased in the presence of the additives while its coercivity ( ) increased. Finally, the density of the samples was observed to increase with increasing sintering time in both types of the samples but with a higher value in the samples with no additives.
Chemical, mechanical and dielectric properties after sintering of hydrothermal nickel–zinc ferrites
Materials Letters, 1999
NiZn ferrites microstructurally controlled were produced after sintering of hydrothermal nanopowders. Chemical microanalyses showed that the zinc-loss phenomenon did not occur significantly, and that the elements iron and nickel probably control the diffusion process in the initial stage of sintering. The hardness and the dielectric response of the sintered NiZn ferrites exhibited a greater dependence on the grain size than on the density of the samples. The variations of the static dielectric permittivity and the relaxation frequency with the sintering conditions were correlated with the microstructural parameters. Complex impedance spectroscopy showed materials with high dielectric response, attributed to electron hopping conduction mechanism, and revealed the presence of a single relaxation, occurring at the grain boundaries. q 1999 Elsevier Science B.V. All rights reserved. 00167-577Xr99r$ -see front matter q 1999 Elsevier Science B.V. All rights reserved.
Journal of Materials Science: Materials in Electronics, 2021
compounds have been prepared by standard solid-state reaction technique and sintered at 1000, 1100, 1150, 1200, and 1250°C for 5 h in air. The effect of sintering temperature on the structural, morphological, magnetic, dielectric, and electrical properties of these spinel ferrites has been studied thoroughly and comparatively. Formation of the single-phase cubic spinel structure of these compositions is confirmed by X-ray diffraction analysis. The lattice constant increases with sintering temperature as well as with 5% scandium (Sc 3?) doping in Ni-Cu-Zn ferrite. Surface morphology reveals that the grain size increases with sintering temperature. Among the prepared ferrites, Ni 0.3 Cu 0.2 Zn 0.5 Sc 0.05-Fe 1.95 O 4 has the maximum density (5.05 9 10 3 kg/m 3) at sintering temperature 1150°C, which gives the highest value of initial permeability. It is observed that initial permeability varies with sintering temperature, and it gives the maximum value at optimum sintering temperature. It is noted that Curie temperature decreases with 5% Sc 3? ions doping, whereas it slightly increases with increasing sintering temperature for both compositions. Ni 0.3 Cu 0.2 Zn 0.5 Fe 2 O 4 compound shows the highest Curie temperature 418°C. Dielectric constant, dielectric loss factor and AC electrical conductivity decrease with 5% Sc 3? ions doping in Ni-Cu-Zn ferrite. The initial permeability decreases sharply at Curie temperature, which indicates a high degree of compositional homogeneity. The 'Hopkinson' peak is observed just below the Curie temperature in the real part of initial permeability versus temperature graphs. The mechanism of dielectric polarization and electrical conductivity has been explained based on the electron hopping between Fe 3? and Fe 2? ions. The variation trend of complex
Structural and Electrical Characterization of Ni-Zn Ferrites
The effect of Zn substitution on the DC electrical resistivity, AC electrical conductivity and microstructure of V 2 O 5 doped Zn (1-x) Ni x Fe 2 O 4 with x=0.0, 0.1, 0.2, 0.3, 0.4 (5 samples) were prepared by conventional ceramic technique has been investigated. The structural characterization of nickel-zinc ferrites were done by X-ray diffraction technique. Micro-structural and morphological studies were carried out by scanning electron microscope technique. The lattice constant determined from XRD data is in the reported range (8.4086 A.U.) DC electrical resistivity exhibits excellent semiconducting behavior. The result shows that AC conductivity increase with the increases in frequency. The micrographs of the samples shows that the average grain size increases with the decreases of Zn content while the grain size decrease with decreasing of Ni content. The variation of DC electrical resistivity with temperature is explained in this work.
Effect of sintering temperature on dielectric properties, and microstructure of Ni(₀.₃)Zn(₀.₇)Fe₂O₄
2017
A series of ferrite material with Ni(0.3)Zn(0.7)Fe2O4 composition have been prepared by the solid state reaction method and sintered at a temperature range of 673 to 1623 K with an interval of 100 K. A total of ten samples was synthesized for this research work. After the samples were sintered, the surface morphology, structure of each sample, density, dielectric and conductivity measurement were made first and then the samples were re-sintered at an increase temperature of 50 K so that the sintered temperatures were 723, 823,
Journal of Advanced Dielectrics
Spinel ferrite Ni[Formula: see text]Mn[Formula: see text]Zn[Formula: see text]Fe2O4 was prepared by a conventional ceramic process followed by sintering at three different temperatures (1050[Formula: see text]C, 1100[Formula: see text]C and 1150[Formula: see text]C). X-ray diffraction (XRD) investigations stated the single-phase cubic spinel structure and the FTIR spectra revealed two prominent bands within the wavenumber region from 600 cm[Formula: see text] to 400 cm[Formula: see text]. Surface morphology showed highly crystalline grain development with sizes ranging from 0.27 [Formula: see text]m to 0.88 [Formula: see text]m. The magnetic hysteresis curve at ambient temperature revealed a significant effect of sintering temperature on both coercivity ([Formula: see text] and saturation magnetization ([Formula: see text]. Temperature caused a decrease in DC electrical resistivity, while the electron transport increased, suggesting the semiconducting nature of all samples and that ...
The effect of heating conditions on the properties of nano- and microstructured Ni–Zn ferrite
The structural, microstructural and morphological, as well as electric and dielectric, properties of nickel-zinc ferrite (Ni 0.3 Zn 0.7 Fe 2 O 4 ) derived from sol-gel auto-combustion have been studied after sintering from 900 to 1300 • C. The effect of heating rate has not been previously investigated and is reported here. X-ray diffraction showed a pure cubic spinel after calcination. Atomic force microscopy revealed nanosized particles after calcination, but scanning electron microscopy showed nanosized grains after sintering at 900 • C. The heating rate has a marked effect on oxidation of Fe 3+ to Fe 2+ , showing an additional approach to control charge carrier concentration in Ni-Zn ferrites (powder and monoliths). The heating rate also influences the average particle size and distribution. Grain size and resistivity of sintered pellets do not show significant change with heating rate, proving that resistivity is mainly dictated by the number of grain boundaries. The dielectric loss tangent curves at room temperature exhibit dielectric relaxation peaks attributed to the similarity in frequency of charge hopping between the localized charge states and external fields. The relaxation peak shifts to higher frequencies for ferrites with nanosized grains.
Effects of La 2O 3 and Gd 2O 3 on some properties of Ni–Zn ferrite
Journal of Magnetism and Magnetic Materials, 2002
The effects of Fe substitution by La 2 O 3 and Gd 2 O 3 (Ni 0.5 Zn 0.5 Fe 2Àx R x O 4 , R=La or Gd, x ¼ 020:04) on the structure, magnetic, and dielectric properties of Ni-Zn ferrite are investigated. With increasing R 2 O 3 , the relative density of sintered bodies decreases, while the lattice parameter increases. La 2 O 3 and Gd 2 O 3 both tend to increase the cut-off frequency, decrease the initial permeability (m 0 ) and magnetic loss tangent tg d(m 0 )) in the range of 1 M-300 MHz; while they flatten the e 0 -f curves, increase e 0 values and decrease dielectric loss tangent (tg d(e 0 )) in the range of 1 M-40 MHz. r (J. Sun). 0304-8853/02/$ -see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 -8 8 5 3 ( 0 2 ) 0 0 4 0 3 -1
Influence of the V2O5 additions on the resistivity and dielectric properties of nickel zinc ferrites
… of Optoelectronics and …, 2005
Ni-Zn ferrites with the formulae Ni 0.65 Zn 0.35 Fe 2 O 4 + xV 2 O 5 where x values ranging from 0.0 wt% to 1.5 wt% in steps of 0.3 wt% have been prepared by conventional ceramic technique. Single phase cubic spinel structures were confirmed by X-ray diffraction patterns. For increasing addition of vanadium up to 0.6 wt% the resistivity of the system has been found to increase. High addition concentration, up to 1.2 wt%, are followed by slow decrease of the resistivity. The variation of the resistivity versus temperature was studied and the activation energies corresponding to the ferrimagnetic and paramagnetic regions for each sample have been estimated. The dielectric constant of the system has a variation quite opposite to that of dc resistivity. A slow variation of the dielectric loss tangent with the additive concentration has been found for all the samples. The sample without addition show lower values of the loss tangent. The results are explained in terms of the conduction and polarization processes associated with the distribution in the lattice of the ions having different valences.