CN1255356C - Low loss and temperature coefficient and high magnetic conductivity ferrite material and its preparing method - Google Patents

Abstract

The invention discloses a preparation method of ferrite material with low loss, low temperature coefficient and high magnetic permeability. Its main phase is spinel structure, and its composition calculated by oxide content is: Fe ₂ O ₃ is 43-52mol%; ZnO is 28-42mol%; CuO is 3-12mol%; NiO is 5-12mol%. The steps of the preparation method are: 1) mixing raw materials, 2) pre-calcining, 3) adding impurities, 4) secondary ball milling, and 5) shaping and sintering. The NiZn ferrite material prepared by the invention has uniform grain size, clear grain boundaries, complete grains, no holes and compact structure. The grain size is in the range of 3-5 μm. The present invention uses CuO instead of NiO, and the pre-sintering and sintering temperature is very low, and the energy consumption in the preparation process is smaller. Because of the very low pre-sintering and sintering temperature, the design requirements for equipment are also lower, reducing the Cost of production. Because it has a wide range of pre-firing and sintering temperatures, and does not require atmosphere protection, the process repeatability and product consistency are very good.

Description

Preparation method of ferrite material with low loss, low temperature coefficient and high magnetic permeability

technical field

The invention relates to a preparation method of ferrite material with low loss, low temperature coefficient and high magnetic permeability.

Background technique

NiZn material with high magnetic permeability is the main raw material for preparing radio frequency broadband devices. The application of radio frequency broadband devices in television, communication, radar, instrumentation and automatic control is very common. With the continuous development of these technologies, a large number of new RF broadband components are required, especially now that the digital TV network system is rapidly replacing the original cable TV system, and the transformation of this network system requires a large number of RF broadband components. This provides a large market for RF broadband components. An important development direction of RF broadband devices is to have a wider operating frequency and be able to adapt to different working environments, especially to work normally at different temperatures. This development trend puts forward higher performance requirements for the existing high permeability NiZn ferrite. NiZn ferrite is required to have higher magnetic permeability, lower loss and better temperature coefficient. Therefore, the initial magnetic permeability is greater than 1500, and the market demand for high-conductivity NiZn ferrite with a wider operating temperature range is constantly expanding.

At present, the oxide method is mainly used to prepare NiZn ferrite with high magnetic permeability. The pre-firing temperature is generally controlled at about 1000°C, while the sintering temperature can be controlled at about 1200°C. At such a high sintering temperature, the grains tend to grow abnormally, and the grains become uneven, resulting in loss and deterioration of the temperature coefficient; and such a high sintering temperature has high requirements for the design and manufacture of the sintering furnace, which consumes a lot of energy. It is not conducive to environmental protection and cost reduction. Moreover, due to the high pre-burning temperature, the hardness of the pre-fired material increases, making the pre-fired material difficult to crush during the secondary crushing process, increasing the loss of steel balls in the ball milling process, and easily bringing in a large amount of impurities.

In order to reduce the pre-sintering and sintering temperature, overcome these shortcomings of the existing technology, and improve the performance of the material, the main measures currently taken mainly include the following categories:

1. Invent a new preparation method to replace the original oxide method. For example, co-precipitation method, sol-gel method, sol-gel self-propagating combustion method, hydrothermal method and self-propagating method. Although these methods have their own characteristics and overcome some defects of the oxide method to a certain extent, compared with the oxide method in terms of cost and process stability, there are still many deficiencies, and the technology is not mature enough. Complete.

2. Add flux. In the production process, Bi ₂ O ₃ or V ₂ O ₅ is usually added as a flux, but the method of adding a single flux has no obvious effect on reducing the sintering temperature, and with the addition of flux, the loss of materials increases large, which degrades the performance of the product.

3. Adjust the process and refine the powder. Reducing the average particle size of the powder to the nanometer level increases the specific surface area of the particles and improves the activity of the powder, but simply reducing the particle size will put forward higher requirements for the equipment, which is not conducive to the reduction of cost, and the simple There is also a certain limit to reducing the particle size by adjusting the process. The particle size cannot be reduced infinitely. When the particle size drops to a certain level, it is easy to grow and reunite.

Therefore, using the oxide method, by adjusting the main formula of the NiZn material, adopting the joint addition of various fluxes and improving the existing oxide process parameters, reducing the pre-sintering and sintering temperature is to reduce the cost and improve the NiZn ferrite material. feasible method for performance.

Contents of the invention

The purpose of the present invention is to provide a method for preparing ferrite material with low loss, low temperature coefficient and high magnetic permeability.

Low loss, low temperature coefficient and high permeability ferrite material, its main phase is spinel structure, the composition calculated by oxide content is:

_Fe2O3 is ₄₃ ～52mol%;

ZnO is 28～42mol%;

CuO is 3-12mol%;

NiO is 5 to 12 mol%.

The steps of the preparation method of the ferrite material with low loss, low temperature coefficient and high magnetic permeability are as follows:

1) Raw material mixing:

Select 43-52mol% Fe ₂ O ₃ , 28-42mol% ZnO, 3-12mol% CuO and 5-12mol% NiO as raw materials, put them into a ball mill, add deionized water of equal weight, and ball mill for 5-9 hours;

2) Pre-burning:

Dry the mixed and ground material, put it into the furnace for pre-burning, the pre-burning temperature is 740-800°C, and the pre-burning time is 1-4 hours;

3) Addition of impurities:

Bi ₂ O ₃ and V ₂ O ₅ nanopowder are selected as additives, wherein the percentage of Bi ₂ O ₃ is 0.12wt% to 0.2wt%, and the percentage of V _{2 O5} is 0.16wt% to 0.28 wt%, the weight percentage of Bi ₂ O ₃ and V ₂ O ₅ is: 1:1.2～1.4;

4) Secondary ball milling:

Put the material into a ball mill, add equal weight of deionized water, and ball mill for 3 to 10 hours, so that the average particle size of the calcined material is less than 0.8 μm;

5) Forming and sintering:

Dry the slurry, add 8-15wt% polyvinyl alcohol (PVA), press and shape it, and put it into a furnace for sintering. The sintering temperature is 950-1000° C., and the sintering time is 6-8 hours.

Advantages of the present invention:

The NiZn ferrite material prepared by the invention has uniform grain size, clear grain boundaries, complete grains, no holes and compact structure. The grain size is in the range of 3-5 μm. The present invention uses CuO instead of NiO, and the pre-sintering and sintering temperature is very low, and the energy consumption in the preparation process is smaller. Because of the very low pre-sintering and sintering temperature, the design requirements for equipment are also lower, reducing the Cost of production. Because it has a wide range of pre-firing and sintering temperatures, and does not require atmosphere protection, the process repeatability and product consistency are very good.

Description of drawings

Fig. 1 is the XRD collection of illustrative plates of calcined material;

Fig. 2 is the XRD collection of illustrative plates of embodiment 1 sintered sample;

Figure 3 is a scanning electron micrograph of the sintered sample.

Detailed ways

The invention provides a ferrite material with low loss, low temperature coefficient and high magnetic permeability and a preparation method thereof. By adjusting the composition formula, impurity addition and process parameters, the pre-sintering and sintering temperatures are reduced, the pre-sintering temperature is lower than 800°C, and the sintering temperature is lower than 1000°C, which improves the performance of NiZn ferrite, especially the temperature characteristics, making The prepared NiZn ferrite material has a specific temperature coefficient of less than 3.0×10 ^-6 in the temperature range of 20-65°C, an initial magnetic permeability of 1500, and a specific loss coefficient of less than 10.0 under the test conditions of 100kHz and 0.25mT ×10 ^-6 , and the specific loss coefficient under the test conditions of 500kHz and 0.25mT is less than 45.0×10 ^-6 .

The aforementioned NiZn ferrite material with a specific temperature coefficient of less than 3.0×10 ^-6 in the temperature range of 20-65°C and an initial magnetic permeability of 1500 only exists in the spinel phase without other impurity phases. The size is in the range of 3-5 μm.

The raw materials are industrially pure Fe ₂ O ₃ , ZnO, NiO and CuO. According to the molecular formula of the ingredients, various raw materials are weighed for mixed grinding, and the rolling ball mill is selected as the mixed grinding equipment. During the mixed milling process, add equal weight of deionized water, and ball mill for 5-9 hours, so that the raw materials are evenly mixed.

The temperature range during pre-firing is 740-800°C. Since the main formula is rich in Cu, CuO can form CuFe ₂ O ₄ with Fe ₂ O ₃ at around 700°C, so that spinel ferrite can be processed at a very low temperature. Formation, which is very beneficial to promote the subsequent sintering reaction, and effectively reduce the sintering temperature.

Bi ₂ O ₃ and V ₂ O ₅ were added jointly as added impurities. Although the method of adding a single flux can reduce the sintering temperature to a certain extent, the effect is still not ideal, and the quality factor of ferrite decreases with the increase of the amount of addition. Using an appropriate amount of V ₂ O ₅ as a flux, although it can improve high-frequency characteristics, reduces the quality factor of low-frequency bands; and the addition of an appropriate amount of Bi ₂ O ₃ is the opposite, which is beneficial to reducing loss in low-frequency bands, while reducing high-frequency band losses. Band loss is not good. Therefore, the joint addition of Bi ₂ O ₃ and V ₂ O ₅ is used as a flux, wherein the weight percentage of Bi ₂ O ₃ and V ₂ O ₅ is: 1:1.2~1.4, which can effectively reduce the sintering temperature, so that the sintering temperature is reduced to Below 1000 ℃, and the high frequency and low frequency losses have been greatly improved, with good frequency characteristics.

Secondary ball milling of pre-sintered materials requires the average particle size of the ball milled particles to be less than 0.8 μm, which increases the specific surface area of the particles, greatly improves the reactivity of the powder, and further reduces the sintering temperature.

The Bohr magnetic moment of Cu ²⁺ is smaller than that of Ni ²⁺ , the substitution of Ni ions by Cu ions will reduce the specific saturation magnetization of the material, and μ _i ∝ M _s ² , so the substitution of Cu ions will have an adverse effect on the magnetic permeability, but The higher density of the low temperature sintered body can increase the magnetic moment M _s per unit volume, and the more complete and uniform grains are conducive to the movement of domain walls, which is also very beneficial to increase the magnetic permeability, so it can effectively This adverse effect is reduced, thereby ensuring that the low-temperature sintered body has high initial magnetic permeability.

High density and uniform grain distribution are the main reasons for lower loss of low temperature sintered body. Because in the frequency range below 1MHz, the loss of NiZn ferrite is mainly composed of hysteresis loss, and the mechanism of its magnetization is mainly domain wall movement. The higher sintering density and more uniform grain size will facilitate the movement of domain walls and reduce hysteresis loss.

On the other hand, Cu ions replace Ni ions and occupy octahedral crystal sites, while the ionic radius of Cu ²⁺ is larger than that of Ni ²⁺ , so the unit cell size and oxygen parameters of low-temperature sintered NiZn ferrite increase. and:

${\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; AX</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; a</span>}\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; BX</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 5</span>}}{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Among them, u is the oxygen parameter; a is the unit cell size; d _AX is the bond length between the metal ion and the oxygen ion occupying the tetrahedral crystal site (A site) in the spinel structure; d _BX is the The bond length between the metal ion and the oxygen ion occupying the octahedral crystal site (B site).

From equations (1) and (2), it can be seen that as the oxygen parameter u increases, d _AX increases and d _BX decreases. This shows that when Cu ions replace Ni ions, the oxygen parameter u increases, making the bond length between Zn ions occupying tetrahedral sites and oxygen ions increase, while metal ions occupying octahedral sites and oxygen ions The bond length between them is correspondingly reduced, which enhances the exchange coupling between metal ions and oxygen ions in the octahedron.

Since the non-magnetic ions Zn ²⁺ occupy the A site in the spinel structure, most of the magnetic ions occupy the B site, so the magnetism of NiZn ferrite mainly comes from the gap between the magnetic ions and the O ions in the B site. The exchange coupling of Cu ions into the crystal lattice strengthens the exchange coupling between the magnetic ions and O ions in the B site, which enhances the anti-thermal interference ability of the exchange coupling, so that the material has better thermal stability and uniform The microstructure can effectively reduce the internal demagnetization field, which is another important factor to improve the temperature characteristics.

The NiZn ferrite material with a specific temperature coefficient of less than 3.0×10 ^-6 and an initial magnetic permeability of 1500 in the temperature range of 20-65°C provided by the present invention and its preparation process are specifically described as follows:

1. Selection of raw materials and master formula design: The raw materials of the low-temperature sintered NiZn ferrite material provided by the present invention are selected from industrially pure Fe ₂ O ₃ , ZnO, NiO and CuO. The main composition and content of the ferrite material are calculated as oxides: 43-52 mol% of Fe ₂ O ₃ , 28-42 mol% of ZnO, 3-12 mol% of CuO, and 5-12 mol% of NiO.

2. Mixing of raw materials: Weigh each raw material according to the main formula, put it into a ball mill, add deionized water of equal weight, and ball mill for 5-9 hours.

3. Pre-burning: Dry the mixed and ground raw materials and put them into the furnace for pre-burning. The pre-firing temperature is 740-800°C, the pre-firing time is 1-4 hours, the atmosphere is air, and it is cooled with the furnace after pre-firing. After pre-burning, all raw materials are required to react, and there is only spinel structure in the pre-fired material, and there are no other impurity phases.

4. Impurity addition: select the joint addition of Bi ₂ O ₃ and V ₂ O ₅ as the added impurity. Wherein the percentage content of Bi ₂ O ₃ is: 0.01-0.5 wt%, and the percentage content of V ₂ O ₅ is: 0.01-0.4 wt%. It is required that the weight percentage of Bi ₂ O ₃ and V ₂ O ₅ is: 1:1.2-1.4.

5. Secondary ball milling: Put the calcined material into a ball mill, add deionized water of equal weight, and ball mill for 3-10 hours, so that the average particle size of the calcined material is less than 0.8 μm.

6. Forming and sintering: Dry the pre-fired material, add 8-15wt% polyvinyl alcohol (PVA), mix evenly, use abrasive tools to press and form, and put it into a furnace for sintering. The sintering temperature is 950-1000°C, the sintering time is 6-8 hours, the sintering atmosphere is air, and the furnace is cooled after the sintering is completed.

The NiZn ferrite material prepared by the method of the invention can be sintered in the range of 950°C to 1000°C, the specific temperature coefficient in the temperature range of 20°C to 65°C is less than 3.0×10 ^-6 , and the initial magnetic permeability is greater than 1500, The specific loss coefficient under the test conditions of 100kHz and 0.25mT is less than 10.0×10 ^-6 , and the specific loss coefficient under the test conditions of 500kHz and 0.25mT is less than 45.0×10 ^-6 ; the NiZn prepared by the preparation method provided by the invention In ferrite, due to the large amount of CuO used to replace NiO, the cost of raw materials is greatly reduced, and the prepared pre-sintered material has a good activity, which greatly reduces the sintering temperature and saves energy consumption, which also greatly reduces The cost of the product. The finally prepared NiZn ferrite material with wide temperature range, low loss and initial magnetic permeability greater than 1500 is an excellent raw material for preparing broadband radio frequency devices.

Example 1:

1) Selection of raw materials: The raw materials of the low-temperature sintered NiZn ferrite material provided by the present invention are selected from industrially pure Fe ₂ O ₃ , ZnO, NiO and CuO.

2) Composition design and weighing: Fe ₂ O ₃ , ZnO, CuO and NiO were weighed according to the corresponding weights of 49 mol% Fe ₂ O ₃ , 32 mol% ZnO, 10 mol% CuO, and 9 mol% NiO.

3) Mixing of raw materials: Put the weighed raw materials into a ball mill, add deionized water of equal weight, and ball mill for 5 hours.

4) Pre-burning: Dry the mixed and ground raw materials and put them into the furnace for pre-burning. The pre-firing temperature is 780°C, the pre-firing time is 2 hours, the atmosphere is air, and it is cooled with the furnace after pre-firing. After pre-burning, XRD phase analysis was carried out on the pre-fired material, and it was confirmed that only spinel structure existed in the pre-fired material without other impurity phases.

5) Addition of impurities: the joint addition of Bi ₂ O ₃ and V ₂ O ₅ is selected as the addition of impurities. Wherein the percentage of Bi ₂ O ₃ is 0.15wt%, and the percentage of V ₂ O ₅ is 0.20wt%, and the weight percentage of Bi ₂ O ₃ and V ₂ O ₅ is 1:1.33.

6) Secondary ball milling: put the calcined material into a ball mill, add an equal weight of deionized water, and ball mill for 8 hours, so that the average particle size of the calcined material is less than 0.8 μm.

7) Forming and sintering: Dry the pre-fired material, add 10wt% polyvinyl alcohol (PVA), mix evenly, mix thoroughly, use a 45-mesh sub-sample sieve to granulate, and press into a φ20 sample ring, put it into a box Sintering in the furnace, the sintering temperature is controlled at about 955°C, the holding time is 6h, and it is cooled to room temperature with the furnace.

The magnetic performance test of the prepared sample ring was carried out on the Hp4284A impedance analyzer, and the density of the sample was measured by the buoyancy method. The phase and microstructure of the samples were analyzed by X-ray diffraction analyzer (XRD) and scanning electron microscope (SEM).

The magnetic properties and density test results of the samples are shown in the following table:

Table 1: Test results of magnetic properties and density of sintered samples: serial number Density(kg/m ³ ) Initial permeability (test frequency: 10kHz) Specific temperature coefficient (20～65℃) Specific loss coefficient (tan δ/μ _i ) 100kHz 500kHz sample 1 5.11 1522 1.9×10 ^-6 8.4×10 ^-6 33.5×10 ^-6

The XRD patterns of the pre-sintered material and sintered body of the sample are shown in accompanying drawings 1 and 2. It can be seen from the figure that in the pre-sintered material and sintered body, only spinel structure crystals exist, and there are no other impurity phases.

The microstructural analysis of the samples can be seen in Figure 3. It can be seen from the SEM photo of the sintered sample that the NiZn ferrite material prepared by the preparation method provided by the present invention has clear grain boundaries, uniform grains, complete grains, no holes, dense structure, and a grain size of 3-5 μm .

Example 2:

1) Selection of materials: The raw materials of the low-temperature sintered NiZn ferrite material provided by the present invention are industrially pure Fe ₂ O ₃ , ZnO, NiO and CuO.

2) Composition design and weighing: Fe ₂ O ₃ , ZnO, CuO and NiO were _weighed according to the corresponding weights of 44mol% Fe2O3, 29mol% ZnO, 12mol _% CuO and 5mol% NiO.

3) Mixing of raw materials: Put the weighed raw materials into a ball mill, add deionized water of equal weight, and ball mill for 5 hours.

4) Pre-burning: Dry the mixed and ground raw materials and put them into the furnace for pre-burning. The pre-firing temperature is 740°C, the pre-firing time is 2 hours, the atmosphere is air, and it is cooled with the furnace after pre-firing. After pre-burning, XRD phase analysis was carried out on the pre-fired material, and it was confirmed that only spinel structure existed in the pre-fired material without other impurity phases.

5) Impurity addition: Bi ₂ O ₃ and V ₂ O ₅ are selected as joint addition of impurities. Wherein the percentage of Bi ₂ O ₃ is 0.12wt%, and the percentage of V ₂ O ₅ is 0.16wt%, and the weight percentage of Bi ₂ O ₃ and V ₂ O ₅ is 1:1.33.

6) Secondary ball milling: put the calcined material into a ball mill, add an equal weight of deionized water, and ball mill for 6 hours, so that the average particle size of the calcined material is less than 0.8 μm.

7) Forming and sintering: Dry the pre-fired material, add 10wt% polyvinyl alcohol (PVA), mix evenly, mix thoroughly, use a 45-mesh sub-sample sieve to granulate, and press into a φ20 sample ring, put it into a box Sintering in the furnace, the sintering temperature is controlled at about 950°C, the holding time is 6h, and it is cooled to room temperature with the furnace.

The magnetic performance test of the prepared sample ring was carried out on the Hp4284A impedance analyzer, and the density of the sample was measured by the buoyancy method.

The magnetic properties and density test results of the samples are shown in the following table:

Table 2: Test results of magnetic properties and density of sintered samples: serial number Density(kg/m ³ ) Initial permeability (test frequency: 10kHz) Specific temperature coefficient (20～65℃) Specific loss coefficient (tanδ/μ _i ) 100kHz 500kHz sample 1 5.12 1507 2.7×10 ^-6 9.3×10 ^-6 40.4×10 ^-6

Increasing the content of CuO can reduce the temperature of pre-sintering and sintering and the addition of Bi ₂ O ₃ and V ₂ O ₅ , so the time of secondary ball milling can be correspondingly reduced, but the temperature coefficient and loss increase.

Example 3:

1) Selection of materials: The raw materials of the low-temperature sintered NiZn ferrite material provided by the present invention are industrially pure Fe ₂ O ₃ , ZnO, NiO and CuO.

2) Composition design and weighing: Fe ₂ O ₃ , ZnO, CuO and NiO were weighed according to the weight of 52 mol% of Fe ₂ O 3 , 36 mol% of ZnO, ₃ mol% of CuO and 12 mol% of NiO.

2) Mixing of raw materials: Put the weighed raw materials into a ball mill, add deionized water of equal weight, and ball mill for 5 hours.

4) Pre-burning: Dry the mixed and ground raw materials and put them into the furnace for pre-burning. The pre-firing temperature is 800°C, the pre-firing time is 2 hours, the atmosphere is air, and it is cooled with the furnace after pre-firing. After pre-burning, XRD phase analysis was carried out on the pre-fired material, and it was confirmed that only spinel structure existed in the pre-fired material without other impurity phases.

5) Addition of impurities: the joint addition of Bi ₂ O ₃ and V ₂ O ₅ is selected as the addition of impurities. Wherein the percentage of Bi ₂ O ₃ is 0.20wt%, and the percentage of V ₂ O ₅ is 0.28wt%, and the weight percentage of Bi ₂ O ₃ and V ₂ O ₅ is 1:1.4.

6) Secondary ball milling: put the calcined material into a ball mill, add an equal weight of deionized water, and ball mill for 10 hours, so that the average particle size of the calcined material is less than 0.8 μm.

7) Forming and sintering: Dry the pre-fired material, add 10wt% polyvinyl alcohol (PVA), mix evenly, mix thoroughly, use a 45-mesh sub-sample sieve to granulate, and press into a φ20 sample ring, put it into a box Sintering in the furnace, the sintering temperature is controlled at about 995°C, the holding time is 6h, and it is cooled to room temperature with the furnace.

The magnetic performance test of the prepared sample ring was carried out on the Hp4284A impedance analyzer, and the density of the sample was measured by the buoyancy method.

The magnetic properties and density test results of the samples are shown in the following table:

Table 3: Test results of magnetic properties and density of sintered samples: serial number Density(kg/m ³ ) Initial permeability (test frequency: 10kHz) Specific temperature coefficient (20～65℃) Specific loss coefficient (tan δ/μ _i ) 100kHz 500kHz sample 1 5.08 1531 2.9×10 ^-6 9.8×10 ^-6 43.4×10 ^-6

As the content of Cu decreases, more Bi ₂ O ₃ and V ₂ O ₅ additions and higher pre-sintering and sintering temperatures are required, so the time for secondary ball milling must be extended accordingly, and the density is reduced. The magnetic permeability will also decrease accordingly, the loss will also increase, and the temperature coefficient will also increase.

Claims (1)

1. a kind of low loss, low temperature coefficient and high magnetic permeability ferrite material preparation method, it is characterized in that the step of method is: 1) Raw material mixing: Select 43-52mol% Fe ₂ O ₃ , 28-42mol% ZnO, 3-12mol% CuO and 5-12mol% NiO as raw materials, put them into a ball mill, add equal weight of deionized water, and ball mill for 5-9 hours; 2) Pre-burning: Dry the mixed and ground material, put it into the furnace for pre-burning, the pre-burning temperature is 740~800C, and the pre-burning time is 1~4h; 3) Addition of impurities: Bi ₂ O ₃ and V ₂ O ₅ nanopowder are selected as additives, wherein the percentage of Bi ₂ O ₃ is 0.12wt% to 0.2wt%, and the percentage of V _{2 O5} is 0.16wt% to 0.28 wt%, the weight percentage of Bi ₂ O ₃ and V ₂ O ₅ is: 1:1.2～1.4; 4) Secondary ball milling: Put the material into a ball mill, add equal weight of deionized water, and ball mill for 3 to 10 hours, so that the average particle size of the calcined material is less than 0.8 μm; 5) Forming and sintering: Dry the slurry, add 8-15wt% polyvinyl alcohol, press to shape, put it into a furnace for sintering, the sintering temperature is 950-1000°C, and the sintering time is 6-8 hours.

Images