CN100480187C - Nickel zinc ferrite material and preparation method thereof - Google Patents

Abstract

The nickel-zinc ferrite material disclosed by the present invention has an expression of Ni _0.5 Zn _0.5 Fe ₂ O ₄ . The preparation steps are as follows: Take analytically pure ferric citrate, zinc nitrate and nickel nitrate according to the stoichiometric ratio of Ni _0.5 Zn _0.5 Fe ₂ O ₄ , and dissolve them in deionized water respectively, add analytical pure citric acid after mixing, stir evenly, and obtain clarified The precursor solution; the precursor solution is heated to evaporate the solvent to form a black-red foamy substance, which is self-combustible, and the foamy substance expands to obtain a loose brown powder; the brown powder is pressed into shape and sintered. The preparation process of the invention is simple, and the prepared nickel-zinc ferrite material has ultra-high DC resistivity and ultra-low dielectric loss. The self-propagating combustion method is used to prepare nickel-zinc ferrite materials, which avoids the high-temperature sintering process of powders, low energy consumption, short synthesis time, high output, no environmental pollution, suitable for large-scale production, uniform particle size distribution, and stable performance. Has a good market prospect.

Description

A kind of nickel-zinc ferrite material and preparation method thereof

technical field

The invention relates to a nickel-zinc ferrite material and a preparation method thereof.

Background technique

Soft magnetic material NiZn ferrite, its performance is very stable, the price is relatively low, the preparation process is relatively easy, and because of its high resistivity, low eddy current loss, and good magnetic properties, this ferrite is widely used in Microwave devices, high-energy converters in the electronics industry, high-quality filters, antenna masts, audio coils, input and output ports of high-speed digital bands, and other communication fields. In the application of NiZn ferrite in the actual high-frequency range, it is necessary to obtain high resistivity, because generally the higher the resistivity, the larger the high-frequency range of its application.

DC resistivity, dielectric constant, and dielectric loss are important properties of NiZn ferrite, which depend on the preparation conditions, chemical composition, and microstructure of the ferrite. Therefore, it is very important to choose a suitable preparation method to obtain high resistivity properties. At present, the preparation methods of ferrite include traditional ceramic sintering method, microwave sintering method, sol-gel method, hydrothermal method, citric acid precursor method and self-propagating combustion method. The commonly used traditional ceramic sintering method, because it requires high temperature sintering, causes performance degradation, and the synthesis time of this method is long. In recent years, some scholars have studied the magnetic properties, electrical properties and dielectric properties of Ni _1-x Zn _x Fe ₂ O ₄ obtained by self-propagating combustion method, and the dielectric constant and dielectric loss of NiZn ferrite obtained lower than that obtained by traditional sintering methods.

With ferric citrate, zinc nitrate, nickel nitrate and citric acid as the raw materials to prepare ferrite few studies, only Verma.A (A.Verma, T.C.Goel, et al., Journal of Magnetism and MagneticMaterials (208 ) (2000), P13-19) used the above raw materials to prepare ferrite materials. Firstly, citrate precursor was used to make xerogel, and then calcined at a high temperature of 1000°C to obtain ferrite powder precursor. NiZn ferrite is obtained by pressing and sintering. This method requires high-temperature calcination of ferrite powder, which consumes a lot of energy.

Contents of the invention

The object of the present invention is to provide an ultra-low loss and ultra-high resistivity nickel-zinc ferrite material and a preparation method thereof.

The nickel-zinc ferrite material used in the present invention is characterized in that its expression is Ni _0.5 Zn _0.5 Fe ₂ O ₄ .

The preparation method of the nickel-zinc ferrite material adopts a self-propagating combustion method, and the steps are as follows:

1) Take analytically pure ferric citrate, zinc nitrate and nickel nitrate according to the stoichiometric ratio of Ni _0.5 Zn _0.5 Fe ₂ O ₄ , dissolve ferric citrate, nickel nitrate and zinc nitrate in deionized water respectively, mix and add analytical pure lemon acid, stir evenly to obtain a clear precursor solution, the molar ratio of citric acid to ferric citrate is 2 to 3:1;

2) Heating the precursor solution to evaporate the solvent to form a black-red foamy substance, which is self-combusting, and the foamy substance expands to obtain a loose brown powder;

3) Compress the brown powder under a pressure of 5-10 MPa, and sinter at 700-1300°C for 2-5 hours.

Compared with the background technology, the present invention has the beneficial effects that the preparation process of the present invention is simple, and compared with the traditional ceramic sintering method, the nickel-zinc ferrite material produced by the ferric citrate system has an ultra-high DC resistivity ( 10 ¹⁰ Ω·cm) and ultra-low dielectric loss (0.008). The self-propagating combustion method is used to prepare nickel-zinc ferrite materials, which avoids the high-temperature sintering process of powders, low energy consumption, short synthesis time, high output, no environmental pollution, suitable for large-scale production, uniform particle size distribution, and stable performance. Has a good market prospect.

Description of drawings

Fig. 1 is the sintered density of nickel zinc ferrite material;

Fig. 2 is the XRD spectrum of nickel-zinc ferrite material;

Fig. 3 is the SEM figure of nickel-zinc ferrite material;

Fig. 4 is the DC resistivity of nickel-zinc ferrite material;

Figure 5 is a graph showing the AC resistivity of nickel-zinc ferrite material as a function of frequency. Curves (a), (b) and (c) in the figure show that the molar ratio of citric acid to ferric citrate is 2:1, 2.5:1, 3:1 AC resistivity changes with frequency;

Figure 6 is a graph showing the dielectric constant of nickel-zinc ferrite material as a function of frequency. Curves (a), (b) and (c) in the figure show that the molar ratio of citric acid to ferric citrate is 2:1, 2.5:1, 3:1 dielectric constant changes with frequency;

Fig. 7 is the graph that the dielectric loss of nickel-zinc ferrite material changes with frequency; Curves (a), (b) and (c) in the figure are respectively that the molar ratio of citric acid and iron citrate is 2:1, 2.5:1, 3:1 dielectric loss varies with frequency.

Detailed ways

Example 1

Take analytically pure ferric citrate, zinc nitrate and nickel nitrate according to the stoichiometric ratio of Ni _0.5 Zn _0.5 Fe ₂ O ₄ , dissolve ferric citrate, nickel nitrate and zinc nitrate in deionized water respectively, add analytical pure citric acid after mixing, The molar ratio of citric acid and ferric citrate is 2:1, 2.5:1, 3:1 respectively, stir evenly to obtain a clear precursor solution; the precursor solution is heated to evaporate the solvent to form a black-red foamy substance, resulting in Self-combustion, the foamy substance expands to obtain a loose brown powder; the brown powder is pressed into a disc with a diameter of 1.8 cm and a thickness of 1.5 mm under a pressure of 5 MPa, and sintered at 1300 ° C for 2 hours.

The relative density test results of the samples are shown in Figure 1. As can be seen from the figure, when the molar ratio of citric acid to ferric citrate was 3:1, the density of the sample was 4.75, and when the molar ratio of citric acid to ferric citrate was 2.5:1, the density of the sample was 4.6, two The densities of the samples are relatively close. As the amount of citric acid added increases, the sintered density also increases.

Example 2

Take analytically pure ferric citrate, zinc nitrate and nickel nitrate according to the stoichiometric ratio of Ni _0.5 Zn _0.5 Fe ₂ O ₄ , dissolve ferric citrate, nickel nitrate and zinc nitrate in deionized water respectively, add analytical pure citric acid after mixing, The molar ratio of citric acid and ferric citrate is 2:1, 2.5:1, 3:1 respectively, stir evenly to obtain a clear precursor solution; the precursor solution is heated to evaporate the solvent to form a black-red foamy substance, resulting in Self-combustion, the foamy substance expands to obtain a loose brown powder; the brown powder is pressed into a disc with a diameter of 1.8 cm and a thickness of 1.5 mm under a pressure of 7 MPa, and sintered at 700 ° C for 3 hours. The phase structure was analyzed by X-ray diffraction (XRD), and the test results are shown in Figure 2. It can be seen from Figure 2 that the structures of the samples obtained with different amounts of citric acid are all single spinel structures.

Example 3

Take analytically pure ferric citrate, zinc nitrate and nickel nitrate according to the stoichiometric ratio of Ni _0.5 Zn _0.5 Fe ₂ O ₄ , dissolve ferric citrate, nickel nitrate and zinc nitrate in deionized water respectively, add analytical pure citric acid after mixing, The molar ratio of citric acid and ferric citrate is 2:1, 2.5:1, 3:1 respectively, stir evenly to obtain a clear precursor solution; the precursor solution is heated to evaporate the solvent to form a black-red foamy substance, resulting in Self-combustion, the foamy substance expands to obtain a loose brown powder; the brown powder is pressed into a disc with a diameter of 1.8 cm and a thickness of 1.5 mm under a pressure of 10 MPa, and sintered at 1100 ° C for 5 hours. The sintered surface of the sample was studied with a field emission scanning electron microscope, and the test results are shown in Figure 3 (a), (b), (c). Figure (a) is the SEM figure of 2:1 molar ratio of citric acid and ferric citrate respectively, and figure (b) is the SEM figure of 2.5:1 molar ratio of citric acid and ferric citrate respectively, figure (c) It is the SEM picture of the molar ratio of citric acid and ferric citrate being 3:1 respectively. It can be seen from the figure that the sintered sample shows incomplete grains, the grains are relatively small, and the whole is relatively dense. Amorphous phase, particle distribution is relatively uniform.

Example 4

Take analytically pure ferric citrate, zinc nitrate and nickel nitrate according to the stoichiometric ratio of Ni _0.5 Zn _0.5 Fe ₂ O ₄ , dissolve ferric citrate, nickel nitrate and zinc nitrate in deionized water respectively, add analytical pure citric acid after mixing, The molar ratio of citric acid and ferric citrate is 2:1, 2.5:1, 3:1 respectively, stir evenly to obtain a clear precursor solution; the precursor solution is heated to evaporate the solvent to form a black-red foamy substance, resulting in Self-combustion, the foamy substance expands to obtain a loose brown powder; the brown powder is pressed into a disc with a diameter of 1.8 cm and a thickness of 1.5 mm under a pressure of 10 MPa, and sintered at 1100 ° C for 3 hours. Polish the fired ceramic disc, and then coat silver glue on both sides of the disc, then test and calculate the DC resistivity and AC resistivity of the material. The test results are shown in Figure 4 and Figure 5. It can be seen from Fig. 4 that the DC resistivity values of the three citric acid samples are about 10 ⁹ Ω·cm. It can be seen from FIG. 5 that the AC resistivities of the three citric acid samples range from 10 ⁶ to 10 ⁷ Ω·cm.

Example 5

Take analytically pure ferric citrate, zinc nitrate and nickel nitrate according to the stoichiometric ratio of Ni _0.5 Zn _0.5 Fe ₂ O ₄ , dissolve ferric citrate, nickel nitrate and zinc nitrate in deionized water respectively, add analytical pure citric acid after mixing, The molar ratio of citric acid and ferric citrate is 2:1, 2.5:1, 3:1 respectively, stir evenly to obtain a clear precursor solution; the precursor solution is heated to evaporate the solvent to form a black-red foamy substance, resulting in Self-combustion, the foamy substance expands to obtain a loose brown powder; the brown powder is pressed into a disc with a diameter of 1.8 cm and a thickness of 1.5 mm under a pressure of 10 MPa, and sintered at 1100 ° C for 4 hours. Polish the fired ceramic disc, and coat silver glue on both sides of the disc, then test and calculate the relative dielectric constant and dielectric loss of the material. The test results are shown in Figure 6 and Figure 7. It can be seen from Figure 6 that when the molar ratio of citric acid to ferric citrate is 2.5:1, the dielectric constant range of the sample is between 12.5 and 20, and when the molar ratio of citric acid to ferric citrate is 3:1, The dielectric constant of the sample ranges from 14 to 15; when the molar ratio of citric acid to ferric citrate is 2:1, the dielectric constant of the sample ranges from 10.5 to 12. It can be seen from Figure 7 that the dielectric loss can reach as low as 0.008.

Claims (1)

1, the preparation method of nickel-zinc ferrite material is characterized in that the steps are as follows: 1) Take analytically pure ferric citrate, zinc nitrate and nickel nitrate according to the stoichiometric ratio of Ni _0.5 Zn _0.5 Fe ₂ O ₄ , dissolve ferric citrate, nickel nitrate and zinc nitrate in deionized water respectively, mix and add analytical pure lemon acid, stir evenly to obtain a clear precursor solution, the molar ratio of citric acid to ferric citrate is 2 to 3:1; 2) Heating the precursor solution to evaporate the solvent to form a black-red foamy substance, which is self-combusting, and the foamy substance expands to obtain a loose brown powder; 3) Compress the brown powder under a pressure of 5-10 MPa, and sinter at 700-1300°C for 2-5 hours.

Images