Open access peer-reviewed chapter

The Synthesis and Characterization of Nickel and Cobalt Ferrite Nanopowders Obtained by Different Methods

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Ilmars Zalite, Gundega Heidemane, Janis Grabis and Mikhail Maiorov

Submitted: December 1st, 2017 Reviewed: March 27th, 2018 Published: September 26th, 2018

DOI: 10.5772/intechopen.76809

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Abstract

The single-phase NiFe2O4 and CoFe2O4 ferrites were synthesized by four methods: the high-frequency plasma chemical synthesis (“plasma”), sol-gel self-propagating combustion method (“combust”), and co-precipitation technology, combined with the hydrothermal synthesis (“hydrotherm”) or spray-drying (“spray”). The specific surface area (SSA), crystallite size, and magnetic properties of the synthesized products have been determined. The synthesized ferrites are nanocrystalline single-phase materials with crystallite size of 5-40 nm. The SSA of nanoparticles synthesized in plasma is 28-30 m2/g, the particle size distribution is in the range of 10-100 nm, with some individual particles up to 200 nm. The SSA of the ferrites obtained by the self-combustion and hydrothermal synthesis is 40 ± 3 and 60 ± 5 m2/g, respectively. The SSA of the samples obtained by the spray-drying method is 80-90 m2/g, and the calculated particle size is 13-15 nm. In this process, pellets up to 10 μm are obtained. After synthesis, CoFe2O4 are characterized by the saturation magnetization Ms of 75 emu/g (“plasma”), 53 emu/g (“combust”) and 57 emu/g (“hydrotherm”). The Ms of NiFe2O4 is 44, 29, and 30 emu/g, respectively. The products obtained by the spray-drying method are partially X-ray amorphous and show magnetic properties only after heating above 450°C. These nanopowders were used in sintering studies.

Keywords

  • NiFe2O4
  • CoFe2O4
  • nanoparticles
  • synthesis
  • properties

1. Introduction

Ferrites are a wide range of minerals and synthetic materials, which have attracted a wide range of scientists’ interest due to their various applications. Ferrites are technologically significant materials due to their unique electrical, dielectric, electronic, mechanical, magnetic, optical and catalytic properties. These ferrites are characterized by good magnetic properties [1], low (NiFe2O4) [2] or high (CoFe2O4) [3] magnetic coercivity, high electrical resistivity and negligible eddy current loss for high-frequency electromagnetic wave propagation [2], chemical stability and fairly high mechanical hardness [4], low dielectric losses and high Curie temperature [5]. CoFe2O4 has a high permeability in the radio frequency range [6], high thermal stability [7], moderate saturation magnetization [3] and electrical conductivity [8].

The most significant and most popular use of ferrites is in optics, electronics, mechanics and other technical fields [9]. Ferrites also play a major role in medicine, biomedical applications, as chemical catalysis and special coatings (antistatic, electromagnetic shielding). Scientific articles contain extensive information on hyperthermia. This method introduces ferrite nanoparticles into living organisms and, under controlled conditions, nanoparticles are transported to the cancerous areas of the body, and cancer cells are destroyed in a magnetic field by heat treatment [10].

Ferrites have become suitable for many technological applications such as microwave devices [11] and telecommunication devices, electric motors and generators, as excellent core material for power transformers in electronics, antenna rods, loading coils and read/write heads for high speed digital tape [1], tape recorders and discs [3], high-density information storage and recording devices and as permanent magnets [11], sensors [12], and so on. Magnetic nanoparticles and in particular magnetic fluids (ferrofluids) are particularly important in biotechnology and biomedicine—the supply of biomedical drugs and as contrast media [12], in medical diagnostics [13]. Ferrite materials are widely used in catalysts [12]. In recent years, ferrite materials have been used to prevent and eliminate radio frequency interference in audio systems [4], as polarized ferroelectric ceramics in acoustic elements in underwater converters [14] and microwave absorbing materials [15], including ferrite-containing radar absorbing paints for masking military aircraft [16]. Lately, it has been discovered that cobalt ferrite nanoparticles can also act as photomagnetic material that shows interesting light-induced coercivity changes [17].

Ferrites in a nanocrystalline state (i.e., below single domain sizes [9]) are often found to have unique physical and mechanical properties compared to coarse-grained polycrystalline materials [18]. It is known that the properties of nanocrystalline ferrite materials, including dielectric constant, conductivity, permeability, and other magnetic properties are determined by their microstructure [19], which, in turn, is influenced by the method of their production [8], that is, the synthesis methods [1]. It is well known that the microstructure, in particular the crystallite size, essentially determines the parameters of the hysteresis loop of soft ferromagnetic materials [20]. Samples obtained with different synthesis methods show different electrical and magnetic properties [4]. Therefore, many new nanoparticle production techniques have been developed in recent years.

Ferrites, as the majority of ceramic materials, are obtained by reactions of solid phase from various oxides [21]. The development of nanotechnological processes has resulted in the development of several liquid phase and gas phase synthesis methods—chemical co-precipitation method [22], the sol-gel method [23], combustion reaction synthesis [24], hydrolysis [25], hydrothermal synthesis [26], salt melt technique [6], pyrolysis, various microwave synthesis methods [1] including microwave refluxing [27], microwave plasma [28] and microwave hydrothermal methods [29], high energy ball milling techniques [30], microemulsion methods [31], sono-chemical reactions [32], vapor deposition [33], precursor methods [34] and plasma synthesis [35].

In this work, we have tried to summarize our research results on ferrite nanoparticles produced by different methods and to compare their properties, including magnetic properties.

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2. Experimental procedure

In research, nickel and cobalt ferrite nanopowders are obtained by the chemical sol-gel self-propagating combustion (“combust.”) method [36], the co-precipitation technology in combination with hydrothermal synthesis (“hydrotherm.”) [37] or spray-drying (“spray”) [38] method and high-frequency plasma chemical synthesis (“plasma”) [39]. The obtained nanopowders have been studied for mechanical and magnetic properties.

The synthesis of cobalt and nickel ferrites by the sol-gel self-propagating combustion method was carried out using reagent grade chemicals: Co(NO3)2·6H2O, Ni(NO3)·6H2O, Fe(NO3)3·9H2O, glycine, nitric acid [36]. A 100 ml 0.1 M cobalt (or nickel) nitrate solution was added to a 200 ml 0.1 M iron nitrate solution. The glycine was separately dissolved in 100 ml of distilled water, nitric acid added and both added to the nitrate mixture. Glycine (Gly) was used as a self-combustion agent with a molar ratio Me/Gly = 1: 0.8 and Gly/Nitr. = 1:4. The mixture was evenly stirred until the mixture has congealed. Then the mixture was heated until it ignited, and the heating was continued at 300°C for 4 h.

By the co-precipitation method, cobalt and nickel ferrites were synthesized using reagent grade chemicals: FeCl3.6H2O, urea, Co(NO3)2.6H2O or Ni(NO3)2.6H2O, NaOH [37]. The precursor was obtained as follows: urea was hydrolyzed for 3 h in a FeCl3.6H2O solution (molar ratio of 3: 1) at 70–75°C. Cobalt or nickel nitrate was added the cooled reaction mixture. The molar ratio FeCl3.6H2O: Co(NO3)2.6H2O or Ni(NO3)2.6H2O corresponds to the metal ion stoichiometry in ferrite. Continually stirring the suspension with 40% NaOH solution, cobalt or nickel hydroxide was slowly precipitated until the pH of the suspension reached 9–10. Then the suspension was placed in an ultrasonic bath for 20 min and then treated for 24 h at 40°C. The sediment was then washed with distilled water by decantation until the presence of Cl ions was no longer detected. Next are two processing options:

  1. by the hydrothermal method, the volume of the hydroxides mixture is reduced by decanting to 250 ml, poured into the reaction vessel and placed in an autoclave. The hydroxide mixture was then treated hydrothermally at different temperatures (200–250°C, 1–3 h, p = 17–17.5 MPa). After hydrothermal treatment, the formed precipitate was filtered with a water jet pump using a 5 μm membrane filter and washed with distilled water and dried at 40°C;

  2. for spraying the hydroxide mixture with the spray-drying method, the pelleting machine was used developed by RTU Institute of Inorganic Chemistry. Main parameters of the suspension spray: hot air temperature and consumption of 370°C and 24 m3/h, temperature in evaporating chamber 120–130°C.

Technological equipment developed by the Institute of Inorganic Chemistry of the Riga Technical University [35] was used for the production of ferrites by means of high-frequency (HF) plasma chemical synthesis. Commercial metals and metal oxides (Ni, Co, NiO, CoO and FeO) powders were evaporated in HF plasma to obtain ferrites. All raw materials in stoichiometric ratios (to obtain NiFe2O4 and CoFe2O4) were injected into nitrogen plasma at an average temperature of 5800–6200 K. After evaporation of the raw materials, the vapor was cooled very quickly with the cooling gas (air) and the product condensed on the filter in the form of nanosized ferrite particles.

Ferrite nanopowders for sintering were prepared as follows: the ferrite nanopowder samples were mechanically mixed for 1 h in a planetary mill with 3% by weight of stearic acid (400 rpm, ZrO2 container, ZrO2 ball material) using isopropanol as a dispersing medium. Stearic acid was used for better pressing. After mixing, the samples were dried in an oven at 80°C and sieved through a 200 μm sieve. For sintering without pressure samples were pressed (200 MPa) as tablets with a diameter of 12 mm and a height of 4–6 mm. Stearic acid was burned out at 600°C. Samples were sintered at 900–1300°C in an air atmosphere at a rate of 10°C/min in an oven LHT-08/18 (Nabertherm GmbH) for 2 h.

All samples were analyzed using the X-ray diffractometer Advance 8 (Bruker AXS). The size of the crystallites was calculated using the Scherer’s equation. The magnetic properties of the synthesized ferrites were analyzed using vibrating sample magnetometry (VSM Lake Shore Cryotronics, Inc., Model 7404 VSM). The SSA was measured using the BET single point method. The size and morphology of the particles as well as the microstructure of the sintered material were studied using transmission electron microscope JEM-100S (JEOL) and a scanning electron microscope Mira/Tescan and Tescan Lyra-3 on the fracture surfaces. The density and open porosity of the sintered samples were determined by the Archimedes method.

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3. Results

The characteristics of synthesized ferrites are given in Table 1 and Figures 15. It has been found that all synthesized ferrites, with the exception of the spray-drying method, are nanocrystalline stoichiometric single-phase powders (Figure 1) with a SSA in the wide range of 30–55 m2/g depending on the synthesis method and calculated (average) particle size of 20–40 nm (Table 1, Figure 2). The crystallite size of these ferrites is also in the range of 10–40 nm. During the spray-drying process high-dispersity nanoparticles, mainly consisting of cobalt or nickel ferrite, iron hydroxide FeO(OH), and X-ray amorphous part of the sample [38] were obtained. The SSA of these samples was in the range of 80–90 m2/g (Table 1), but the calculated average particle size was 13–15 nm [38]. In this process, pellets of up to 10 μm were obtained (Figure 3).

SampleSSA, m2/gd50, nm*Crystallite size, nmPhase compositionMs, emu/gMr, emu/gHc, Oe
CoFe2O4 (plasma)293940CoFe2O475.432.0780
CoFe2O4 (combust.)373120CoFe2O453.420.31170
CoFe2O4 (hydrotherm.)542110–12CoFe2O450.112.6390
CoFe2O4 (spray)8414p.a. CoFe2O4, FeO(OH)
NiFe2O4 (plasma)293840NiFe2O444.210.074
NiFe2O4 (combust.)432610NiFe2O421.42.381
NiFe2O4 (hydrotherm.)422622NiFe2O439.02.623
NiFe2O4 (spray)8513p.a. NiFe2O4, FeO(OH)

Table 1.

Properties of synthesized ferrite nanopowders.

Average particle size calculated from SSA.


p.a.—partially amorphous; Ms—saturation magnetization; Mr—remanent magnetization; Hccoercivity

Figure 1.

XRD pattern of ferrite nanopowders.

Figure 2.

The electron microscope image of CoFe2O4 (A, C) and NiFe2O4 (B, D) obtained by the plasma synthesis (A), self-combustion (B), hydrothermal (C) and spray (D) methods.

Figure 3.

The electron microscope (SEM) images of spray-dried NiFe2O4 at different enlargements.

The finer particles were obtained in the spray-drying process, hydrothermal and sol-gel self- propagating combustion synthesis, but the distribution of the particle size of ferrites obtained by the plasma synthesis is the most extensive (20–100 nm) with individual particles up to 200 nm. Plasma-derived particles are spherical.

The samples obtained at the optimal synthesis conditions were very clean because any other additional phase (usually magnetite, maghemite, hematite or other metal oxides) was not found by the X-ray analysis. By analyzing samples of ferrites produced by different methods, slight differences in relative intensity and width of reflexes, indicating differences in crystallite size (Figure 1), can be seen in the X-ray images. The self-combustion and hydrothermal synthesis methods give nanopowders with a lower crystallite size than those obtained by plasma synthesis (Table 1).

The magnetic properties of the nanoparticles obtained by the plasma synthesis process (Table 1, Figure 4) are very close to those of the standard dense material (CoFe2O4 magnetic saturation values are 80 emu/g and NiFe2O4 50 emu/g [40]). In contrast, the samples prepared by self-combustion and hydrothermal method have different magnetic properties than those obtained by plasma synthesis. This is probably due to difference in the size of nanoparticles obtained by plasma, self-combustion and hydrothermal synthesis. The products obtained by the spray-drying method have magnetic properties only after heat treatment at 400–450°C at 550°C, the saturation magnetization of nickel ferrite is 16.9 emu/g, while for the cobalt ferrite is 51.3 emu/g.

Figure 4.

Magnetic properties of ferrites synthesized by the spray-drying (1) at 450°C, sol-gel self-combustion (2) and hydrothermal (3) method and in plasma (4).

Another interesting feature of nanoparticles synthesized in this study is their magnetic behavior, that is, although for all synthesized powders the particle size is below the critical size of a single domain (about 70 nm [41]), quasi-supermagnetic behavior is observed only for plasma-synthesized NiFe2O4 nanoparticles.

As an example of the impact of synthesis parameters, CoFe2O4 hydrothermal synthesis can be mentioned. Synthesizing at 200°C for 1 h, the product contains also FeO(OH) in addition to the basic phase (Figure 5). The product has weak magnetic properties (Table 2). Experiments have shown that the optimum synthesis temperature, when the pure one-phase product is formed, is from 230°C. Increasing the processing temperatures (up to 250°C) and time (up to 3 h) does not significantly affect the size of the specific surface area and crystallite. Increasing of the synthesis temperature and hydrothermal treatment time results in a small increase in magnetic characteristics (saturation magnetization Ms, remanent magnetization Mr and coercivity Hc) (Table 2).

Figure 5.

XRD pattern of the hydrothermally synthesized CoFe2O4 nanopowder prepared at: 1–200°C, 1 h; 2–230°C, 1 h; 3–250°C, 1 h.

NoMode, °C /hSSA, m2/gd50, nm*Crystallite size, nmXRD phasesMagnetic properties
Ms, emu/gMr, emu/gHc, Oe
1200/15820~10CoFe2O4, FeO(OH)13.22.6105
2200/3591913–14CoFe2O4
3230/1631810–13CoFe2O450.010.2494
4230/3552115–16CoFe2O458.917.8643
5250/1611912–13CoFe2O457.317.3566
6250/3621810–12CoFe2O459.816.8574

Table 2.

Characteristics of CoFe2O4 nanopowders prepared hydrothermally.

Calculated from SSA.


After thermal treatment at higher temperatures, ferrite nanopowders synthesized by self-combustion, hydrothermal and spray-drying method, tend to decrease their SSA, but the particle size and crystallite size increase (Figure 6). This trend can be explained by the fact that the particles recrystallize and grow at higher temperatures, so the specific surface decreases. With the increase of crystallite size, the saturation magnetization and remanent magnetization of ferrites increase (Tables 3 and 4, Figures 7 and 8). For example, after thermal treatment of CoFe2O4 obtained by self-combustion and hydrothermal method at 800°C and more, the saturation magnetization increases to 80 and 72 emu/g, respectively.

Figure 6.

Specific surface area (SSA) and crystallite size comparison depending on temperature for NiFe2O4 and CoFe2O4 synthesized by the sol-gel self-combustion (A), the hydrothermal (B) and spray-drying (C) method.

SamplesHeating temperature, °CMs, emu/gMr, emu/gHc, Oe
CoFe2O4 combust.Raw powder53.420.31170
45055.021.71190
65076.139.31350
85079.935.7930
90079.831.3980
CoFe2O4 hydrotherm.Raw powder50.010.2495
40050.112.6390
60062.822.4760
80071.628.9875
CoFe2O4 sprayRaw powder
350
55051.314.7649
75061.122.3878
95076.834.11067

Table 3.

Magnetic properties of CoFe2O4 synthesized by the sol-gel self-combustion, hydrothermal and spray-drying methods after thermal treatment (2 h at different temperatures).

SamplesHeating temperature, °CMs, emu/gMr, emu/gHc, Oe
NiFe2O4 combust.Raw powder29.06.0120
45031.44.8130
65037.49.1200
85045.214.8145
90047.415.0135
NiFe2O4 hydrotherm.Raw powder37.42.623
40036.73.834
60040.25.255
80042.65.070
NiFe2O4 sprayRaw powder
350
55016.91.157
75021.64.5214
95040.08.6151

Table 4.

Magnetic properties of NiFe2O4 synthesized by the sol-gel self-combustion, hydrothermal and spray-drying methods after thermal treatment (2 h at different temperatures).

Figure 7.

The magnetic properties of the sample CoFe2O4 prepared by the hydrothermal synthesis (A) after thermal treatment at 400°C (1), 600°C (2) and 800°C (3), NiFe2O4 prepared by the self-combustion synthesis (B) after thermal treatment at 450°C (4), 650°C (5) and 850°C (6).

Figure 8.

The magnetic properties of samples of CoFe2O4 and NiFe2O4 after thermal treatment at 450 (1), 650 (2) and 950 (3)°C prepared by the spray-drying method.

The spray-dried powder after the synthesis and granulation is partially amorphous and contains a small amount of FeO(OH). After heat treatment, starting from 400 to 450°C, a stoichiometric, single-phase nanocrystalline powder (NiFe2O4 or CoFe2O4) (Figure 9) was formed, with SSA from 100 (at 350°C) to 20 m2/g (at 950°C) (Figure 6). The crystallite size at 350°C is 4 and 6 nm, respectively for NiFe2O4 and CoFe2O4, which increases with the increase of the processing temperature. The saturation magnetization (Ms) of the NiFe2O4 and CoFe2O4 ferrites increases, respectively, from 6 and 15 emu/g (at 450°C) to 40 and 77 emu/g (at 950°C) (Tables 3 and 4, Figure 8).

Figure 9.

XRD pattern of spray-dried CoFe2O4 and NiFe2O4 ferrite nanopowders.

The relative density of samples before sintering was of 51–52% for plasma synthesized products and of 31–33% for products obtained by other methods. This shows that the ferrite nanopowders obtained by these methods are more difficult to compress because their particles are finer than ferrite powders synthesized in plasma.

Nanosized ferrite powders were sinteredat 900–1300°C. The density of ferrites after the heat treatment is shown in Table 5.

SampleSintering temperature, °C
9001000110012001300
ρ, %Pop., %ρ, %Pop., %ρ, %Pop., %ρ, %Pop., %ρ, %Pop., %
CoFe2O4 (plasma)82.616.097.00.298.50.197.90
CoFe2O4 (combust.)65.733.478.321.693.43.1
CoFe2O4 (hydrotherm.)81.314.294.30.895.00.1
CoFe2O4 (spray)62.335.590.08.890.84.795.10.7
NiFe2O4 (plasma)87.912.199.40.299.90.1100.00
NiFe2O4 (combust.)72.425.587.79.496.11.6
NiFe2O4 (hydrotherm.)79.119.885.812.0
NiFe2O4 (spray)52.244.069.527.685.312.190.77.1

Table 5.

The relative density and open porosity of ferrites depending on sintering temperature (after 2 h sintering).

ρ—density; Pop—open porosity.

The sintering process of plasma synthesis products is the fastest compared with all investigated nanopowders: they have a high density at 900°C, but above 1000°C, the density is approaching already 100%. CoFe2O4 ferrites synthesized by other methods have a relatively high density at 1100°C, while NiFe2O4 ferrites require the temperature of 1200°C or higher to achieve high density. Although the sintering temperature of the ferrites obtained by the spray method is slightly higher, they could be the most promising on the technological point of view among all these nanopowders because they are flowing and can be pressed without further treatment.

The crystallite size grows slightly during sintering: from 70 to 80 nm at 1100°C to 120–140 nm at 1300°C. For example, the crystallite size of hydrothermal CoFe2O4 varies from 10 to 13 nm in the raw powder to 75 nm (1000°C) and 150 nm (sintered at 1200°C). The grain size of samples sintered at 1200°C, obtained from self-combustion, hydrothermal and spray-dried powders, does not exceed 1 to 6 μm (Figure 10). As a result of high sintering activity, the grain size of plasma-synthesized ferrite outweighs: 10–15 μm for NiFe2O4 and 10–30 μm for CoFe2O4.

Figure 10.

Typical SEM image of NiFe2O4 (a, D) and CoFe2O4 (B, C, E) ceramics sintered at 1200°C 2 h. The powders are prepared by hydrothermal (A, B), sol-gel self-propagating combustion (C), spray-drying (D) and plasma (E) methods.

Compared with the ferrite nanopowders, ceramic materials have a higher saturation magnetization (Figure 11) and lower coercivity. This could be explained by the increase in grain size and crystallite size. An increase in the temperature of the sintering results in the increase of the grain size and magnetization for all ferrite materials, while coercivity decreases (Table 6). The magnetic properties of the samples sintered at 1200°C are almost the same regardless of the method of extracting ferrite powders: saturation magnetization for CoFe2O4 is of 80–84 emu/g and 46–48 emu/g for NiFe2O4.

Figure 11.

Magnetic properties of CoFe2O4 (a) and NiFe2O4 (B) ferrite, sintered at 1200°C from different powders: 1—hydrothermal, 2—spray-drying, 3—combustion, 4—plasma.

Heating temperature, °CCoFe2O4NiFe2O4
Ms, emu/gMr, emu/gHc, OeMs, emu/gMr, emu/gHc, Oe
Self-combustion
120082.66.9190
Hydrothermal
110077.020.749340.46.5102
120081.314.116946.01.715
Spray
110074.615.342748.03.035
130073.85.918747.02.411
Plasma
110081.814.025845.73.835
120083.68.011046.30.711

Table 6.

Magnetic properties of CoFe2O4 and NiFe2O4 ceramics after 2 h sintering.

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4. Conclusions

Single-phase nickel and cobalt ferrite nanopowders can be successfully synthesized by the chemical sol-gel self-propagating combustion and co-precipitation method combined with hydrothermal synthesis or spray-drying method as well as high-frequency plasma synthesis. The magnetic properties of synthesized ferrite powders depend on their synthesis method.

Comparing the methods for obtaining ferrite nanopowders described earlier, we can say that plasma synthesis currently is the most productive method resulting in the highest magnetic properties (75 emu/g for CoFe2O4 and 44 emu/g for NiFe2O4). The disadvantage of this method is the presence of particles exceeding the size of 100 nm in a product that is not acceptable in all applications.

The chemical sol-gel self-propagating combustion and hydrothermal synthesis methods enables the production of smaller particles (SSA. = 35–55 m2/g; average particle size 20–30 nm) with less explicited magnetic properties (50–55 emu/g for CoFe2O4 and 20–40 emu/g for NiFe2O4) after synthesis, which can be increased after heat treatment at temperatures up to 800°C. The lack of these methods is a time-consuming process of filtering nanoparticles.

The filtration process can be bypassed by the spray-drying method. Here, the smallest particles of the powder (SSA = 80–90 m2/g, average particle size 10–15 nm) are obtained, but due to the low processing temperatures, they have no explicited magnetic properties. Magnetic properties are observed after additional treatment starting at 400–450°C. However, the granular product is well suited for automated pressing processes for production of ceramic materials.

Sintered materials have higher magnetic properties than nanopowders. Magnetic properties of samples sintered at 1200°C are almost the same regardless of the method of obtaining ferrite powders: the saturation magnetization of CoFe2O4 is 80–84 emu/g and 46–48 emu/g for NiFe2O4.

References

  1. 1. Costa ACFM, Tortella E, Morelli MR, Kiminami RHGA. Synthesis, microstructure and magnetic properties of Ni–Zn ferrites. Journal of Magnetism and Magnetic Materials. 2003;256:174-182. DOI: 10.1016/S0304-8853(02)00449-3
  2. 2. Priyadharsini P, Pradeep A, Chandrasekaran G. Novel combustion route of synthesis and characterization of nanocrystalline mixed ferrites of Ni–Zn. Journal of Magnetism and Magnetic Materials. 2009;321:1898-1903. DOI: 10.1016/j.jmmm.2008.12.005
  3. 3. Hou C, Yu H, Zhang Q, Li Y. WangH. Preparation and magnetic property analysis of monodisperse Co–Zn ferrite nanospheres. Journal of Alloys and Compounds. 2010;491:431-435. DOI: 10.1016/j.jallcom.2009.10.217
  4. 4. Gul IH, Ahmed W, Maqsood A. Electrical and magnetic characterization of nanocrystalline Ni–Zn ferrite synthesis by co-precipitation route. Journal of Magnetism and Magnetic Materials. 2008;320:270-275. DOI: 10.1016/j.jmmm.2007.05.032
  5. 5. Yadoji P, Peelamedu R, Agrawal D, Roy R. Microwave sintering of Ni–Zn ferrites: Comparison with conventional sintering. Materials Science and Engineering: B. 2003;98:269-278. DOI: 10.1016/S0921-5107(03)00063-1
  6. 6. Jadhav SS, Patange SM, Jadhav KM. Dielectric behaviour study of nanocrystalline Co-Zn ferrite. Journal of Biomedical and Bioengineering. 2010;1:21-29
  7. 7. Ahmed MA, EL-Khawlani AA. Enhancement of the crystal size and magnetic properties of Mg-substituted Co ferrite. Journal of Magnetism and Magnetic Materials. 2009;321:1959-1963. DOI: 10.1016/j.jmmm.2008.12.021
  8. 8. Gul IH, Abbasi AZ, Amin F, Anis-ur-Rehman M, Maqsood A. Structural, magnetic and electrical properties of Co1−xZnxFe2O4 synthesized by co-precipitation method. Journal of Magnetism and Magnetic Materials. 2007;311:494-499. DOI: 10.1016/j.jmmm.2006.08.005
  9. 9. Xue B, Liu R, Xu ZD, Zheng YF. Microwave Fabrication and Magnetic Property of Hierarchical Spherical α-Fe2O3 Nanostructures. Chemistry Letters. 2008;37:1058-1059. DOI: 10.1246/cl.2008.1058
  10. 10. Fortin JP, Wilhelm C, Servais J, Menager C, Bacri JCF, Gazeau J. Size sorted anionic iron oxide nanomagnets as colloidal mediators for magnetic hyperthermia. Chemical Society. 2007;129:2628-2635. DOI: 10.1021/ja067457e
  11. 11. Gul IH, Amin F, Abbasi AZ, Anis-ur-Rehman M, Maqsood A. Physical and magnetic characterization of co-precipitated nanosize Co–Ni ferrites. Scripta Materialia. 2007;56:497-500. DOI: 10.1016/j.scriptamat.2006.11.020
  12. 12. Slatineanu T, Iordan AR, Oancea V, Palamaru MN, Dumitru I, Constantin CP, Caltun OF. Magnetic and dielectric properties of Co–Zn ferrite. Materials Science and Engineering: B. 2013;178:1040-1047. DOI: 10.1016/j.mseb.2013.06.014
  13. 13. Arulmurugan R, Jeyadevan B, Vaidyanathan G, Sendhilnathan S. Effect of zinc substitution on Co–Zn and Mn–Zn ferrite nanoparticles prepared by co-precipitation. Journal of Magnetism and Magnetic Materials. 2005;288:470-477. DOI: 10.1016/j.jmmm.2004.09.138
  14. 14. Tawfik A. Electromechanical properties of Co0.6Zn0.4Fe2O4 ferrite transducer. Journal of Magnetism and Magnetic Materials. 2001;237:283-287. DOI: 10.1016/S0304-8853(01)00466-8
  15. 15. Kumar S, Singh V, Aggarwal S, Mandal UK, Kotnala RK. Monodisperse Co, Zn-Ferrite nanocrystals: Controlled synthesis, characterization and magnetic properties. Journal of Magnetism and Magnetic Materials. 2012;324:3683-3689. DOI: 10.1016/j.jmmm.2012.05.048
  16. 16. Gul IH, Maqsood A. Structural, magnetic and electrical properties of cobalt ferrites prepared by the sol–gel route. Journal of Alloys and Compounds. 2008;465:227-231. DOI: 10.1016/j.jallcom.2007.11.006
  17. 17. Giri AK, Kirkpatrick EM, Moongkhamklang P, Majetich SA. Photomagnetism and structure in cobalt ferrite nanoparticles. Applied Physics Letters. 2002;80:2341. DOI: 10.1063/1.1464661
  18. 18. Suryanarayana C. Nanocrystalline materials. International Materials Reviews. 1995;40:41-64. DOI: 10.1179/imr.1995.40.2.41
  19. 19. van der Zaag PJ, Ruigrok JJM, Noordermeer A, van Delden MHWM. The initial permeability of polycrystalline MnZn ferrites: The influence of domain and microstructure. Journal of Applied Physics. 1993;74:4085-4095. DOI: 10.1063/1.354454
  20. 20. Chicinas I. Soft magnetic nanocrystalline powders produced by mechanical alloying routes. Journal of Optoelectronics and Advanced Materials. 2006;8:439-448
  21. 21. Akther Hossain AKM, Tabata H, Kawai T. Magnetoresistive properties of Zn1−xCoxFe2O4 ferrites. Journal of Magnetism and Magnetic Materials. 2008;320:1157-1162. DOI: 10.1016/j.jmmm.2007.11.009
  22. 22. Ferreira TAS, Waerenborgh JC, Mendonça MHRM, Nunes MR, Costaa FM. Structural and morphological characterization of FeCo2O4 and CoFe2O4 spinels prepared by a coprecipitation method. Solid State Sciences. 2003;5:383-392. DOI: 10.1016/S1293-2558(03)00011-6
  23. 23. Tang DQ, Zhang DJ, Ai H. Fabrication of magnetic core–shell CoFe2O4/Al2O3 nanoparticles as immobilized metal chelate affinity support for protein adsorption. Chemistry Letters. 2006;35:1238-1239. DOI: 10.1246/cl.2006.1238
  24. 24. Zhou Z, Zhang Y, Wang Z, Wei W, Tang W, Shi J, Xiong R. Electronic structure studies of the spinel CoFe2O4 by X-ray photoelectron spectroscopy. Applied Surface Science. 2008;254:6972-6975. DOI: 10.1016/j.apsusc.2008.05.067
  25. 25. Duong GV, Hanh N, Linh DV, Groessinger R, Weinberger P, Schafler E, Zehetbauer M. Monodispersed nanocrystalline Co1–xZnxFe2O4 particles by forced hydrolysis: Synthesis and characterization. Journal of Magnetism and Magnetic Materials. 2007;311:46-50. DOI: 10.1016/j.jmmm.2006.11.167
  26. 26. Millot N, Gallet SL, Aymes D, Bernard F, Grin Y. Spark plasma sintering of cobalt ferrite nanopowders prepared by coprecipitation and hydrothermal synthesis. Journal of the European Ceramic Society. 2007;27:921-926. DOI: 10.1016/j.jeurceramsoc.2006.04.141
  27. 27. Giri J, Sriharsha T, Bahadur D. Optimization of parameters for the synthesis of nano-sized Co1−xZnxFe2O4, (0 ≤ x ≤ 0.8) by microwave refluxing. Journal of Materials Chemistry. 2004;14:875-880. DOI: 10.1039/B310668C
  28. 28. Chau JLH, Hsu MK, Kao CC. Microwave plasma synthesis of Co and SiC-coated Co nanopowders. Materials Letters. 2006;60:947-951. DOI: 10.1016/j.matlet.2005.10.054
  29. 29. Kim CK, Lee JH, Katoh S, Murakami R, Yoshimura M. Synthesis of Co-, Co-Zn and Ni-Zn ferrite powders by the microwave-hydrothermal method. Materials Research Bulletin. 2001;36:2241-2250. DOI: 10.1016/S0025-5408(01)00703-6
  30. 30. Jiang JZ, Wynn P, Mørup S, Okada T, Berry FJ. Magnetic structure evolution in mechanically milled nanostructured ZnFe2O4 particles. Nanostructured Materials. 1999;12:737-740. DOI: 10.1016/S0965-9773(99)00228-7
  31. 31. Hochepied JF, Bonville P, Pileni MP. Nonstoichiometric zinc ferrite nanocrystals: Syntheses and unusual magnetic properties. The Journal of Physical Chemistry B. 2000;104:905-9122. DOI: 10.1021/jp991626i
  32. 32. Shafi KVPM, Gedanken A, Prozorov R, Balogh J. Sonochemical preparation and size-dependent properties of nanostructured CoFe2O4 particles. Chemistry of Materials. 1998;10:3445-3450. DOI: 10.1021/cm980182k
  33. 33. Jalaly M, Enayati MH, Karimzadeh F, Kameli P. Mechanosynthesis of nanostructured magnetic Ni–Zn ferrite. Powder Technology. 2009;193:150-153. DOI: 10.1016/j.powtec.2009.03.008
  34. 34. Li F, Liu J, Evans DG, Duan X. Stoichiometric synthesis of pure MFe2O4(M = Mg, Co, and Ni) spinel ferrites from tailored layered double hydroxide (hydrotalcite-like) precursors. Chemistry of Materials. 2004;16:1597-1602. DOI: 10.1021/cm035248c
  35. 35. Grabis J, Zalite I. Nanosize powders of refractory compounds for obtaining of fine-grained ceramic materials. Materials Science Forum. 2007;555:267-272. DOI: 10.4028/www.scientific.net/MSF.555.267
  36. 36. Zalite I, Heidemane G, Kodols M, Grabis J, Maiorov M. The synthesis, characterization and sintering of nickel and cobalt ferrite nanopowders. Materials Science (Medžigotyra). 2012;18:3-7. DOI: 10.5755/j01.ms.18.1.1332
  37. 37. Zalite I, Heidemane G, Kuznetsova L, Maiorov M. Hydrothermal synthesis of cobalt ferrite nanosized powders. IOP Conference Series: Materials Science and Engineering. 2015;77:5. DOI: 10.1088/1757-899X/77/1/012011
  38. 38. Zalite I, Heidemane G, Palcevskis E, Maiorov M. Properties of nanosized ferrite powders and sintered materials prepared by the Co-precipitation technology, combined with the spray-drying method. Key Engineering Materials. 2016;721:295-299. DOI: 10.4028/www.scientific.net/KEM.721.295
  39. 39. Zalite I, Heidemane G, Kuznetsova L, Kodols M, Grabis J, Maiorov M. The synthesis and characterization of nickel and cobalt ferrite nanopowders obtained by different methods. Chemical Technology. 2016;67:53-57. DOI: 10.5755/j01.ct.67.1.15824
  40. 40. Smit J, Wijn HPJ. Ferrites: Physical properties of ferrimagnetic oxides in relation to their technical applications. Eindhoven, The Netherlands: Philips Technical Library; 1959. p. 384
  41. 41. Song Q, Zhang ZJ. Correlation between spin-orbital coupling and the superparamagnetic properties in magnetite and cobalt ferrite spinel nanocrystals. Journal of Physical Chemistry B. 2006;110:11205-11209. DOI: 10.1021/jp060577o

Written By

Ilmars Zalite, Gundega Heidemane, Janis Grabis and Mikhail Maiorov

Submitted: December 1st, 2017 Reviewed: March 27th, 2018 Published: September 26th, 2018