High-frequency low-temperature coefficient low-loss nickel-zinc ferrite and preparation method thereof

Abstract

The application discloses a high-frequency low-temperature-coefficient low-loss nickel-zinc ferrite and a preparation method thereof, and belongs to the field of ferrite soft magnetic materials. 1‑x Zn x Fe2 O4, wherein 0<=x<=0.5, and one or both of Co2O3 or TiO2 is added during preparation, Co2O3 is 0.3wt%-0.9wt%, and TiO2 is 0.1wt%-1wt%, the specific temperature coefficient of the low-temperature-coefficient low-loss nickel-zinc ferrite material provided by the application is α μr The magnetic permeability frequency stability and the loss are extremely high in a wide temperature range of-55-120 DEG C, the overall performance is much higher than the current industry level, and the high-reliability soft magnetic material production is provided for electronic equipment devices used in harsh temperature environments, thereby providing technical support.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ferrite soft magnetic materials, and particularly relates to a high-frequency low-temperature-coefficient low-loss nickel-zinc ferrite and a preparation method thereof. BACKGROUND

[0002] In recent years, with the rapid upgrading of products in the consumer electronics and household appliance industries and the needs of emerging industries such as new energy, photovoltaic and 5G communication to develop in the direction of high frequency, light weight, miniaturization and integration, soft magnetic materials are required to have the technical characteristics of high frequency, high saturation magnetic flux density and low loss; especially in high-precision and reliable engineering applications, soft magnetic materials are more required to have high reliability, especially the temperature stability of magnetic permeability, to ensure stable performance output when working in space, seabed, plateau, underground and other harsh environments. NiZn ferrite, as a kind of soft magnetic material with high resistivity, excellent high-frequency characteristics and simple process preparation, is widely used in medium and high frequency inductors, filter cores, transformers and other devices; because its magnetic properties are greatly affected by the temperature difference of the use environment, in order to ensure normal work in harsh environments, it is necessary to improve the temperature stability of the product while ensuring the magnetic properties of NiZn ferrite.

[0003] For NiZn ferrite, the magnetic permeability μ i is proportional to the square of M s , and inversely proportional to the product of K1, λ s and σ i . These parameters are affected by changes in external temperature, which directly affects the stability of the magnetic permeability. In order to improve the temperature stability of the magnetic permeability, it is necessary to start from K1 and λ s , take appropriate improvement measures to control the change of K1 and λ s with temperature within a very small range and reduce the absolute value of K1 and λ s , and try to make K1→0 and λ s →0, so as to improve the temperature stability of the magnetic permeability. NiZn ferrite has a relatively low negative K1 value, in order to make K1→0, it is necessary to use ion compensation with positive K1 value; the commonly used compensation ions include Co 2+ , Ti 4+ , Fe 2+ and Sn 4+ ions.

[0004] Chinese patent CN 112466591 A uses main components: Fe2O3: 47-50 mol%, NiO: 13-20 mol%, ZnO: 25-35 mol%, CuO: 5-7 mol%, and a secondary component SnO2, content of 0.2-0.5 wt%, pre-sintering temperature 850±10℃, pre-sintering time 7-9 hours, sintering temperature 1060-1100℃, sintering time 120-150 minutes, to obtain a nickel-zinc ferrite material with low temperature coefficient. Chinese patent CN 103693949 B uses main components with the following contents: Fe2O3: 51-59 mol%, NiO: 10-22 mol%, ZnO: 20-35 mol%, CuO: 0.3-8 mol%; secondary components are selected from two or more components with the following contents: Mn3O4: 0.05-1.0 wt%, SiO2: 0.05-0.9 wt%, Bi2O3: 0.01-0.5 wt%, TiO2: 0.01-0.8 wt%, CaCO3: 0.01-0.6 wt%, Co2O3: 0.01-0.3 wt%, pre-sintering conditions 750℃-1050℃, holding for 0.5-4 hours, sintering conditions 940-1300℃, holding for 2-6 hours, to obtain a ferrite material with low temperature coefficient, small change in permeability with temperature, and low loss in a wide temperature range of -40℃-120℃.

[0005] However, according to the calculation formula of specific temperature coefficient:

[0006]

[0007] T r is the test temperature, T ref is the reference temperature, μ r is the permeability at the test temperature, μ ref is the permeability at the reference temperature, it can be seen from the above formula that, for the same size α μr , the value range of Δμ is larger, i.e. the fluctuation range of permeability with temperature is larger; and for the nickel-zinc ferrite material with smaller μ ref , the value range of Δμ is smaller, i.e. the fluctuation range of permeability with temperature is smaller. refThe range of the value of delta mu is smaller, that is, the range of the change of the permeability with temperature is smaller; in addition, the low permeability nickel-zinc ferrite is usually accompanied by excellent high frequency characteristics, and is generally applied to high frequency scenes (1-500 MHz), and is mainly used as a magnetic core of an impedance transformer, a power divider, a power combiner, a coupler, a power inductor, a transmission line transformer and the like, and is widely applied to short wave / ultra-short wave transmitters, impedance transformers, short wave antennas and the like. The above equipment has a very high reliability requirement for the material, and in particular, the permeability needs to have excellent temperature stability to ensure stable performance output in harsh environments such as space, seabed and plateau. Therefore, it is much more difficult and meaningful to reduce the temperature coefficient of the low permeability nickel-zinc ferrite than to reduce the temperature coefficient of the high permeability nickel-zinc ferrite. In the above two patents, the method for reducing the temperature coefficient of the nickel-zinc ferrite is for the nickel-zinc ferrite with an initial permeability mu i ≥250, which generally belongs to a high-Zn formula, and a large amount of CuO and the like is usually added to control the sintering temperature and the Curie temperature in order to obtain excellent magnetic properties; however, for a low permeability formula, it is verified through experiments that the temperature coefficient of the permeability decreases first and then increases with the increase of the pre-sintering temperature, and the minimum point of the temperature coefficient of the permeability is about 1100 DEG C or even higher. If a large amount of CuO, Bi2O3 and the like is added to the low permeability formula, the temperature coefficient of the permeability will be deteriorated under the same pre-sintering temperature condition, and the pre-sintering will be excessive, the pre-sintering material will be too hard, and the material cannot be ball milled to the required particle size (D 50 ≤2 mu m) range during secondary ball milling. Therefore, the method for reducing the temperature coefficient of the nickel-zinc ferrite in the above two patents is for the nickel-zinc ferrite with an initial permeability mu i ≥250, and is not applicable to the nickel-zinc ferrite material with an initial permeability mu i ≤250, and there is no report on reducing the temperature coefficient of the nickel-zinc ferrite material with an initial permeability mu i ≤250. SUMMARY

[0008] One of the purposes of the present application is to provide a high-frequency low-temperature-coefficient low-loss nickel-zinc ferrite to solve the above problems.

[0009] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: a high-frequency low-temperature-coefficient low-loss nickel-zinc ferrite, the chemical formula of the ferrite is Ni 1-x Zn xFe2O4, wherein: 0≤x≤0.5, and one or both of Co2O3 or TiO2 is added during preparation, Co2O3: 0.3wt%-0.9wt%, TiO2: 0.1-1wt%, the mass percentage is based on the total mass of raw materials Fe2O3, ZnO and NiO, that is, the addition amount of Co2O3 is 0.3wt%-0.9wt% of the mass of raw materials Fe2O3, ZnO and NiO, and so on.

[0010] As a preferred technical solution, the doping amount of Co2O3 is 0.6wt%, and the doping amount of TiO2 is 0.4wt%.

[0011] The second object of the present application is to provide a preparation method of the high-frequency low-temperature coefficient low-loss nickel-zinc ferrite, which comprises the following steps in sequence: batching, mixing, pre-sintering, ball milling, granulation, molding and sintering, wherein the pre-sintering temperature is 1050-1200°C, and the holding time is 2-6 hours.

[0012] As a preferred technical solution, the pre-sintering temperature in the pre-sintering step is 1100°C.

[0013] As a preferred technical solution, one or both of Co2O3 or TiO2 is added in the mixing or ball milling step.

[0014] As a preferred technical solution, the sintering temperature in the sintering step is 1050-1250°C, and the holding time is 2-6 hours.

[0015] As a further preferred technical solution, the sintering temperature is 1150°C.

[0016] More specifically, the raw materials used in the batching step are preferably ferric oxide (Fe2O3) with a purity of 99.5%, zinc oxide (ZnO) and nickel oxide (NiO).

[0017] In the mixing step, the various raw materials weighed in the batching step are mixed and loaded into a ball mill tank, steel balls and deionized water are added, and the raw materials are subjected to one-time wet mixing and ball milling, the ball milling time is 1-6 hours, and the rotation speed is 200-400r / min; it should be noted that the higher the rotation speed, the shorter the ball milling time, and the rotation speed can be reduced by 50r / min and the time can be increased by 1 hour according to the rule.

[0018] In the pre-sintering step, the slurry after the mixing step is dried, the powder is prepared by passing through a 30-100 mesh sample screen, and then placed in a sintering furnace for pre-sintering, the pre-sintering temperature is 1050-1200°C, and the holding time is 2-6 hours; it should be noted that if the pre-sintering temperature is increased, the corresponding holding time can be appropriately reduced.

[0019] In the ball milling step, the powder after the pre-burning step is loaded into a ball mill tank, and one or both of Co2O3 and TiO2 doping ions are added, Co2O3: 0.3wt%-0.9wt%, TiO2: 0.1-1wt% (Note: the dopant can be added during mixing or during the second milling). Steel balls and deionized water are added, preferably balls: material: water = 6:1:1.5, and the second wet ball milling is carried out, the ball milling time is 1-6 hours, the rotation speed is 200r / min-400r / min, to obtain a slurry; it should be noted that the higher the rotation speed, the shorter the ball milling time, which can be set according to the rule of reducing the rotation speed by 50r / min and increasing the time by 1 hour.

[0020] In the granulation step, the slurry after the ball milling step is dried, and then preferably 6wt%-10wt% polyvinyl alcohol adhesive 10wt% is added for granulation, and the intermediate powder is taken after passing through a 40-100 mesh sample screen;

[0021] In the forming step, the powder obtained after the granulation step is placed into a mold for pressing, and the pressing pressure is 100MPa-160MPa, to obtain a material green body;

[0022] In the sintering step, the green body obtained after the forming step is loaded into an air atmosphere furnace for sintering, the sintering temperature is 1050℃-1250℃, and the holding time is 2-6 hours, to obtain a nickel-zinc ferrite core.

[0023] The present application adjusts the ratio of Zn 2+ and Ni 2+ to realize the design of the main formula, uses Co2O3 and TiO2 as doping ions, and avoids the weakening of the regulation of the temperature coefficient of nickel-zinc ferrite by using multiple ion doping. In addition, by adjusting the pre-burning temperature and sintering temperature and other related process conditions, the control of the grain size, porosity, shrinkage, density, defects and the like is realized to reduce the temperature coefficient of the nickel-zinc ferrite, and a kind of high-frequency low-temperature coefficient low-loss nickel-zinc ferrite material (initial permeability μ i =10-250, specific temperature coefficient α μr =1-8×10 -6 .

[0024] The present application tests the electromagnetic performance of the prepared ferrite material according to GJB 1931A-2006 and SJ 20966-2006 (measurement method of soft magnetic ferrite material).

[0025] Compared with the prior art, the present application has the advantages that the specific temperature coefficient α μr of the low-temperature coefficient low-loss nickel-zinc ferrite material provided by the present application is 1-8×10 -6decreased to 1-8*10 -6 It has extremely high magnetic permeability frequency stability and low loss in a wide temperature range of -55-120℃, and the overall performance is much higher than the current industry level, which provides technical support for the production of soft magnetic materials with high reliability for electronic devices in harsh temperature environments. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The complex magnetic permeability spectrum of Example 8;

[0027] Figure 2 The B-H curve of Example 8;

[0028] Figure 3 The μ i -T curve of Example 8 before and after improvement. DETAILED DESCRIPTION

[0029] The application will be further described below with reference to the accompanying drawings.

[0030] Example 1:

[0031] A high-frequency low-temperature coefficient low-loss nickel-zinc ferrite, the preparation method comprising the following steps:

[0032] (1) Formulation design, according to the chemical formula Ni 0.9 Zn 0.1 Fe2 O4 to design the formula;

[0033] (2) Weighing, according to the results of formula design, calculate and weigh the required various raw materials, the raw materials are Fe2O3, NiO and ZnO with a purity of 99.5%;

[0034] (3) Mixing, mix the weighed various raw materials into a ball mill tank, add steel balls and deionized water, and use a planetary ball mill for primary wet mixing and ball milling of the raw materials, the ball milling time is 2 hours and the rotating speed is 350 r / min;

[0035] (4) Pre-burning, dry the slurry, pass through a 30-mesh sample screen to prepare a powder, and then put it into a sintering furnace for pre-burning, the pre-burning temperature is 1050℃ and the holding time is 4 hours;

[0036] (5) Ball milling, put the pre-burned powder into a ball mill tank, add a single or two kinds of Co2O3 and TiO2 doping ions, Co2O3: 0.6wt%, TiO2: 0wt%, add balls and deionized water, and use a planetary ball mill for secondary wet ball milling, the ball milling time is 2 hours (1-6 hours) and the rotating speed is 350 r / min, to obtain a slurry;

[0037] (6) Granulation, drying the slurry after ball milling, then adding 10wt% polyvinyl alcohol adhesive to granulate, and passing through 40-100 mesh sieve.

[0038] (7) Molding, putting the granulated material into a mold to press, with a pressing pressure of 160MPa, to obtain a green body of the material;

[0039] (8) Sintering, putting the green body into an air atmosphere furnace to sinter, with a sintering temperature of 1150℃ and a holding time of 4 hours.

[0040] (9) Testing, testing the electromagnetic properties of the material according to GJB 1931A-2006 and SJ 20966-2006.

[0041] Examples 2-15

[0042] The formula and preparation process parameters are shown in Table 1

[0043] Table 1: Doping amount and process parameters of each example and comparative example

[0044]

[0045] In Table 1, in Examples 2-15, except for the formula, pre-sintering temperature, sintering temperature, Co2O3 doping amount, TiO2 doping amount and other parameters, other process conditions are the same as those of Example 1. After testing, the electromagnetic properties of the ferrite material obtained in each example are shown in Table 2.

[0046] Table 2: Electromagnetic properties of the material of each example and comparative example

[0047]

[0048] From Examples 1-3 in Table 1 and Table 2, it can be obtained that the temperature coefficient of permeability (α μr) with the increase of pre-sintering temperature, the temperature coefficient of the magnetic permeability of the nickel-zinc ferrite shows a trend of first decreasing and then increasing, and the lowest temperature coefficient is obtained when the pre-sintering temperature is about 1100℃; from Examples 4-6, it can be obtained that the temperature coefficient of the magnetic permeability of the nickel-zinc ferrite of the application shows a trend of first decreasing and then increasing with the increase of pre-sintering temperature, and the lowest temperature coefficient is shown when the sintering temperature is about 1150℃; from Examples 7-9, it can be obtained that the temperature coefficient of the magnetic permeability of the nickel-zinc ferrite of the application shows a trend of first decreasing and then increasing with the increase of TiO2 doping amount, and the lowest temperature coefficient is shown when the doping amount is 0.4wt%; from Examples 12-14, it can be obtained that the temperature coefficient of the magnetic permeability of the nickel-zinc ferrite of the application shows a trend of first decreasing and then increasing with the increase of Co2O3 doping amount, and the lowest temperature coefficient is shown when the doping amount is 0.6wt%; from Examples 2, 5, 10, 11, 13, 15, it can be obtained that under the same conditions, the control of the magnetic permeability can be realized by controlling the ratio of Ni 2+ and Zn 2+ .

[0049] From the comparison between Comparative Example 2, Comparative Example 3 and Example 2, it is shown that too high or too low pre-sintering temperature is not conducive to reducing the temperature coefficient of the magnetic permeability; from Comparative Example 4 and Comparative Example 5 and Example 8, too high or too low sintering temperature is not conducive to reducing the temperature coefficient of the magnetic permeability.

[0050] The above Example 8 is taken as a test object, and its magnetic spectrum, B-H curve at room temperature and μ i -T curve are tested respectively, and the test results are shown in Figure 1 , Figure 2 and Figure 3 . The specific test method of the magnetic spectrum is as follows: a standard sample ring with a size of 25x15x7mm is used, the number of turns is 10, the wire diameter is 0.47mm, and an E4991A impedance analyzer is used for testing; the test method of the B-H curve is as follows: a standard sample ring with a size of 25x15x7mm is used, the primary coil is 70 turns, the secondary coil is 10 turns, and a SY-8218B-H tester is used for testing, the test frequency f=10kHz, and H=5000A / m; the test method of the μ i -T curve is as follows: a standard sample ring with a size of 25x15x7mm is used, the number of turns is 40, the wire diameter is 0.47mm, a high-low temperature oven and a digital bridge LCR meter are used for testing, and the test frequency is 10kHz. Figure 1 is the complex magnetic permeability spectrum of Example 8, which has excellent high-frequency characteristics and magnetic permeability frequency stability in the frequency range of f≤50MHz; Figure 2 is the B-H curve of Example 8 at room temperature, and it can be seen that the nickel-zinc ferrite prepared by this method still has a relatively high saturation magnetic induction intensity; Figure 3To improve the initial permeability versus temperature curve, the dotted line is μ i -T curve, the solid line is μ i -T curve, from a comparison of the two, μ i -T curve is almost a straight line, that is, the initial permeability has particularly high temperature stability, while the temperature stability of Comparative Example 1 is very poor.

[0051] The above description is merely preferred embodiments of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A high-frequency low-temperature coefficient low-loss nickel-zinc ferrite, characterized by, The chemical formula of the ferrite is Ni 1- x Zn x Fe2O4, wherein: 0.1≤x≤0.5, and a doping material is added during preparation, the doping material being Co2O3 added alone, or Co2O3 and TiO2 added simultaneously, wherein the added amount of Co2O3 is 0.3wt%-0.9wt%, and the added amount of TiO2 is 0.1wt%-1wt%. The preparation method comprises the steps of batching, mixing, pre-sintering, ball milling, granulating, molding and sintering, wherein the doping material is added in the mixing or ball milling step, the pre-sintering temperature is 1100 DEG C, and the sintering temperature is 1150 DEG C.

2. The high-frequency low-temperature coefficient low-loss nickel-zinc ferrite according to claim 1, characterized by, The doping amount of Co2O3 is 0.6 wt%, and the doping amount of TiO2 is 0.4 wt%.

3. The high-frequency low-temperature coefficient low-loss nickel-zinc ferrite according to claim 1, characterized by, In the pre-sintering step, the temperature is kept for 2-6 hours.

4. The high-frequency low-temperature coefficient low-loss nickel-zinc ferrite according to claim 1, characterized by, In the sintering step, the temperature is kept for 2-6 hours.

Images