CN113990658A - High-remanence-ratio low-porosity hexagonal ferrite thick film and preparation method and application thereof - Google Patents
High-remanence-ratio low-porosity hexagonal ferrite thick film and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a hexagonal ferrite thick film with high remanence ratio and low porosity, a preparation method and application thereof, wherein the preparation method comprises the following steps: (1) mixing BaM powder with organic carrier, grinding to obtain uniformly mixed slurry; (2) coating the paste on Al by screen printing method2O3Forming a thick film on the substrate; (3) placing the thick film and the substrate in a magnetic field, heating, magnetizing and removing glue; (4) to the thick film after magnetizingAnd performing pressure sintering to obtain the hexaferrite thick film. According to the invention, the hexagonal ferrite thick film with high remanence ratio, low porosity, high density and high saturation magnetization is prepared by optimizing the organic carrier, controlling the particle size of BaM powder and improving the film preparation process, and can be applied to a self-biased circulator, and the preparation method can realize low-cost large-scale preparation of BaM thick films and meet the industrial requirements.
Description
Technical Field
The invention relates to the technical field of thin film materials, in particular to a hexagonal ferrite thick film with high remanence ratio and low porosity, and a preparation method and application thereof.
Background
M-type hexaferrite (Ba, Sr) Fe12O19(BaM for short), because of high uniaxial magnetocrystalline anisotropy and moderate saturation magnetization, the magnetic material can be applied to microwave high frequency domain (such as K) under the condition of low bias magnetic field or no bias magnetic fieldaWave band) and millimeter wave band, namely, realizing self-bias application (a higher internal bias magnetic field is still kept after an external field is removed), and further realizing high frequency, miniaturization and integration of the magnetic microwave device.
At present, the preparation technology of barium ferrite films mainly comprises laser pulse deposition (PLD), Liquid Phase Epitaxy (LPE), magnetron sputtering, screen printing and other processes. The BaM film with consistent lattice orientation and high quality can be prepared by PLD and magnetron sputtering, but the prepared film has limited thickness (only a few microns), low growth rate, small surface area, low residual magnetization and no potential of self-bias; compared with the film-making methods such as PLD and the like, the LPE has the advantages that the growth rate is high, the film thickness is large, the crystallization quality of the film is high, but the coercive force of the single crystal structure is very low due to the lack of a large number of defects such as crystal boundaries and the like, and the remanence is low, so that the LPE cannot be applied to self-biased devices; compared with the three preparation methods, BaM thick films are prepared in a screen printing mode, the preparation method is simple, the cost is low, the film forming is easy, the efficiency is high, the film thickness is easy to adjust, and the large-scale industrial production is facilitated, but the performance of BaM thick films prepared by screen printing at present still needs to be improved, and the problems of low remanence ratio, high porosity, low saturation magnetization and the like exist (Ref.: Chenzhongyan, Von zakun, bear dazzling, screen printing and magnetic field orientation preparation of barium ferrite thick films [ J ]. magnetic materials and devices, 2010,41(02):22-24+ 45; yellow liner, Zhanwan, Peng, influence research of organic carriers on barium ferrite thick film microstructures [ J ]. functional materials and device reports, 2011,17(01):69-73), and the application of BaM thick films in self-biased devices is limited by the problems. Therefore, a low-cost method for preparing BaM film with high remanence ratio, low porosity and high saturation magnetization is needed.
Disclosure of Invention
The invention provides a hexagonal ferrite thick film with high remanence ratio and low porosity, a preparation method and application thereof, wherein a BaM thick film with high remanence ratio, low porosity and high saturation magnetization is obtained by optimizing the components and proportion of an organic carrier, reducing the particle size of BaM powder and improving the preparation method, and the performance requirements of a self-biased circulator material are met.
In order to solve the above problems, the present invention provides the following technical solutions:
the invention provides a preparation method of a hexaferrite thick film, which comprises the following steps:
(1) mixing BaM powder with organic carrier, grinding to obtain uniformly mixed slurry;
(2) coating the paste on Al by screen printing method2O3Forming a thick film on the substrate;
(3) placing the thick film and the substrate in a magnetic field, heating, magnetizing and removing glue;
(4) and sintering the magnetized thick film, and cooling to obtain the hexagonal ferrite thick film.
Further, the preparation of the BaM powder comprises the following steps:
s1: mixing the mixed raw materials with ball milling beads and absolute alcohol, and then carrying out ball milling;
s2: drying the ball-milled materials;
s3: grinding the dried materials, and placing the ground materials in air or oxygen atmosphere for pre-burning treatment;
s4: grinding the pre-sintered material into powder, and then placing the powder in a flowing oxygen atmosphere for sintering treatment;
s5: and mixing the sintered powder with glass frit, ball milling beads and absolute ethyl alcohol, and carrying out ball milling and drying treatment to obtain the required BaM powder.
Further, the raw material in S1 contains BaCO3、Fe2O3。
Further, the raw material in S1 may further contain SrCo3。
Further, the molar purity of the components contained in the raw material in S1 was 99.99%.
Further, in S1, the rotation speed of ball milling is preferably 200-300rpm, and the time of ball milling is preferably 12-24 h.
Further, in S2 and S5, the drying temperature is preferably 70-100 ℃, and the drying time is preferably 30-50 min.
Further, the pre-firing treatment in S3 specifically includes: the temperature is raised to 1000 ℃ at the heating rate of 2 ℃/min, and the temperature is kept for 4 h.
Further, after the pre-sintering, the temperature is reduced at the cooling rate of 1-3 ℃/min.
Further, the sintering treatment in S4 specifically includes: heating to 1250 ℃ at the heating rate of 2 ℃/min, and preserving heat for 10 h.
Further, the temperature is reduced at the temperature reduction rate of 2-3 ℃/min after sintering.
Further, in S5, the weight ratio of the glass frit to the BaM powder is 2% -8%, and the ratio of large, medium and small ball grinding beads in the ball grinding beads is 1:1-3: 3-5; wherein the diameter of the large ball grinding bead is 11mm, the diameter of the medium ball grinding bead is 7mm, and the diameter of the small ball grinding bead is 5 mm.
Further, in S5, the rotation speed of the ball milling is preferably 200-300rpm, and the time of the ball milling is preferably 10-80 h.
Further, in the step (1), the BaM powder has an average particle size of 0.3 to 0.7. mu.m.
Further, the organic vehicle comprises the following components in percentage by mass: 10-20% of epoxy resin, 40-60% of curing agent, 15-30% of terpineol, 5-10% of tributyl citrate and other components accounting for 1-3% of the total weight of the epoxy resin, the curing agent and the terpineol; the other components are selected from at least three of polydimethylsiloxane, ethylcellulose, castor oil, lecithin, epoxy acrylate and urethane acrylate.
Further, the epoxy resin is preferably a bisphenol a type epoxy resin, and the curing agent is preferably an aliphatic amine resin.
Further, the other components are preferably ethyl cellulose, castor oil, lecithin.
The organic vehicle is prepared by mixing and dispersing powders with glass powder and other solid powders for binding into paste, and printing on ceramic substrate by screen printing method. The organic carrier consists of an organic solvent, a thickening agent, a flatting agent, a dispersing agent and the like, wherein the organic solvent determines the rheological property, the volatility and the bonding property of the organic carrier, and the organic solvent used by the invention consists of epoxy resin, a curing agent, terpineol and tributyl citrate. In addition, the invention is added with components such as epoxy resin, curing agent and the like. The epoxy resin adjusts the rheological property of the organic carrier, so that the viscosity of the organic carrier is kept moderate, and the organic carrier can be fully mixed with the powder. This ensures that the thick film grains are free to rotate and fully oriented when magnetized. The curing agent improves the adhesive property of the organic vehicle, so that the mixed slurry can be firmly adhered to the substrate. Under the combined action of epoxy resin and curing agent, the thick film can prevent the secondary flow of slurry during heating and magnetizing, and the surface is kept flat and the appearance is complete. In addition, the epoxy resin and the curing agent are added to form the multi-component organic solvent, so that the organic carrier can slowly volatilize in different temperature ranges, the porosity of the thick film is reduced, and the density of the film is improved.
Further, in the step (1), the mass ratio of the BaM powder to the organic carrier is 2-4: 1.
Further, in the step (2), the screen printing operation specifically includes: mixing Al2O3The substrate is placed in a printing template, and slurry is coated on the substrate from the template through a scraper to form a thick film.
Further, in the step (3), the strength of the magnetic field is 8000-; the heating and magnetizing temperature is 150-300 ℃, and the heating and magnetizing time is 20-50 min.
The magnetization orients the easy axis (crystal C axis) of the ferrite particles in the thick film along the external field to obtain high remanence. Wherein the heating in the magnetizing process mainly has the following three functions: the first is that at higher temperatures, the organic vehicle is more mobile to facilitate particle rotation; secondly, the thick film is primarily solidified, and the surface is kept flat; thirdly, the glue can be discharged preliminarily, and a part of the organic carriers can be volatilized. If the heating process is not carried out in the magnetizing process, the thick film paste cannot be completely solidified, and the surface of the thick film paste is uneven. Further, when the slurry is subjected to pressure sintering, the thick film is deformed by squeezing because the slurry is not completely solidified, and thus the thick film cannot be used.
Further, in the step (4), the sintering is preferably pressure sintering.
Further, the specific operation of the pressure sintering is as follows: placing a load on the thick film, placing the thick film in an air atmosphere, heating to a sintering temperature, and sintering for 1-10 h; the load pressure is 0.5-3MPa, the heating rate is 2-3 ℃/min, and the sintering temperature is 900-.
The pressure sintering makes BaM thick film under the combined action of heat energy and stress, promotes the combination of powder particles and the densification of material, and obtains the thick film with higher density. If only ordinary sintering is performed, the density of the thick film is much lower than that of pressure sintering.
Further, the load is preferably Al2O3。
Further, in the step (4), the cooling rate is 2-3 ℃/min.
In the sintering process, the temperature rising or reducing speed of the high-temperature area needs to be slowed down, on one hand, BaM is promoted to grow in the high-temperature area, and crystals are formed; on the other hand, the sample can crack when the temperature is increased or decreased too fast at high temperature. The temperature can be rapidly reduced in a low temperature region, and the sintering is accelerated.
The invention provides a hexaferrite thick film prepared by the preparation method of the first aspect.
Further, the film thickness of the hexaferrite thick film is 0.1-0.4mm, for example: 0.1mm, 0.2mm, 0.3mm, 0.4mm, etc.
In a third aspect, the invention provides a use of the hexaferrite thick film of the second aspect in a self-biased circulator material.
The material requirements for the self-biasing circulator are as follows: remanence ratio (SQ, M)r/Ms) High, preferably SQ ≧ 0.9; the coercive force (Hc) is high, enough coercive force can ensure the working stability of the self-bias field and cannot be easily interfered by the outside, and when Hc is used>3kOe can keep the device stably running; high saturation magnetization (4 π Ms), when the 4 π Ms of the material>3kG can be applied to the self-biased circulator; the thick film has a film thickness of not less than 0.1. mu.m.
Furthermore, the SQ of the hexaferrite thick film is more than or equal to 0.9, Hc is more than 3kOe, and 4 pi Ms is more than 3kG, so that the performance requirement of the self-bias circulator material is met.
The invention has the beneficial effects that:
1. according to the invention, the bonding performance of the organic carrier is improved by reducing the particle size of the powder and optimizing the formula of the organic solvent in the organic carrier, and meanwhile, the composition of the organic carrier is enriched, so that the improvement of the surface flatness of the BaM thick film and the reduction of the porosity of the film are facilitated, and the overall density of the thick film is further improved.
2. The invention provides a preparation process of a screen printing thick film for preparing a self-bias device material, which can prepare BaM thick films in a large scale at low cost, and prepare flat, compact and crack-free BaM thick films by improving the processes such as heating and magnetizing, pressure sintering, sintering temperature rise and temperature reduction rate control and the like.
3. The BaM thick film with high remanence ratio, low porosity, high density and high saturation magnetization is prepared by improving the selection of materials and the preparation process, and the performance requirements of the self-biased circulator material are met.
Drawings
FIG. 1 is a schematic illustration of screen printing to produce thick films;
FIG. 2 is a room temperature XRD test pattern of the example and comparative example samples;
FIG. 3 is a room temperature SEM test image of example and comparative example samples;
fig. 4 is a hysteresis loop image of the example and comparative example.
Detailed Description
The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The experimental methods used in the following examples are conventional methods unless otherwise specified, and materials, reagents and the like used therein are commercially available without otherwise specified.
The BaM powders in the examples and comparative examples were prepared by the following preparation method:
(1) raw material BaCO with the molar purity of 99.99 percent3、Fe2O3The powder medicine is prepared according to the following steps of 1: mixing according to the molar ratio of 12;
(2) and placing the mixed powder into a ball milling tank, placing ball milling beads, adding absolute alcohol to the position with two thirds height of the ball milling tank, placing the ball milling tank into a ball mill, and carrying out ball milling for 18 hours at the rotating speed of 250 r/min.
(3) And taking out the powder subjected to the first ball milling, placing the powder into a mortar, placing the mortar into a dryer for drying, and drying the powder for 40 minutes at 80 ℃.
(4) Grinding the dried medicine, placing the ground medicine into a crucible, placing the crucible into a tube furnace, and pre-burning the medicine in the atmosphere of air or flowing oxygen. Heating according to a certain temperature rate, wherein the heating rate is 2 ℃/min; presintering temperature is 1000 ℃, and presintering time is 4 hours; the cooling rate is 1 to 3 ℃/min.
(5) After the pre-sintering is finished, taking out the sample, and manually grinding the sample in a cleaned mortar for 30 minutes; and putting the ground powder into a clean crucible, and putting the crucible into a tube furnace to perform sintering treatment in a flowing oxygen atmosphere. Heating according to a certain temperature gradient, wherein the heating rate is 2 ℃/min; the sintering temperature is 1250 ℃, and the sintering time is 10 hours; the cooling rate is 2 ℃/min to 3 ℃/min.
(6) Mixing the BaM powder after sintering with a certain proportion of glass frit, wherein the weight ratio of the glass frit to BaM is 4%; then placed in a ball mill jar and placed in a 1: 2: 4, wherein the large-size ball grinding bead is 11mm, the medium-size ball grinding bead is 7mm, and the small-size ball grinding bead is 5 mm; adding absolute alcohol to the position of two thirds of the height of the ball milling tank, putting the ball milling tank into a ball mill, and carrying out ball milling for a certain time at the rotating speed of 250 r/min.
(7) And taking out the sample subjected to the second ball milling, placing the sample into a mortar, placing the mortar into a dryer for drying, and drying the sample at 80 ℃ for 40 minutes to obtain required BaM powder, wherein the particle size of the powder is related to the ball milling time.
Example 1
BaM powder which is subjected to secondary ball milling for 80 hours and has an average particle size of 0.4 mu m and an organic carrier are mixed according to a mass ratio of 3: 1, mixing to obtain mixed slurry, wherein the organic carrier consists of the following components: 19 wt% of bisphenol A type epoxy resin, 58 wt% of fatty amine resin, 16 wt% of terpineol, 9 wt% of tributyl citrate, 2 wt% of ethyl cellulose, 1 wt% of lecithin and 1 wt% of castor oil; on Al by screen printing2O3Forming a thick film on the substrate, and heating for 50min in a 8000Oe magnetic field at 200 deg.C; loading 1MPa pressure on the magnetized thick film, and sintering at 1100 ℃ for 4h to prepare the BaM thick film.
Example 2
BaM powder which is subjected to secondary ball milling for 80 hours and has an average particle size of 0.4 mu m and an organic carrier are mixed according to a mass ratio of 3: 1, mixing to obtain mixed slurry, wherein the organic carrier consists of the following components: 11 wt% of bisphenol A type epoxy resin, 58 wt% of fatty amine resin, 27 wt% of terpineol, 9 wt% of tributyl citrate, 2 wt% of ethyl cellulose, 1 wt% of lecithin and 1 wt% of castor oil; on Al by screen printing2O3Forming a thick film on the substrate, and heating for 50min in a 8000Oe magnetic field at 200 deg.C; loading 1MPa pressure on the magnetized thick film, and sintering at 1100 ℃ for 4h to prepare the BaM thick film.
Example 3
BaM powder which is subjected to secondary ball milling for 50 hours and has an average particle size of 0.5 mu m and an organic carrier are mixed according to a mass ratio of 3: 1, mixing to obtain mixed slurry, wherein the organic carrier consists of the following components: 16 wt% bisphenol A type ringOxygen resin, 50 wt% of fatty amine resin, 23 wt% of terpineol, 7 wt% of tributyl citrate, 2 wt% of ethyl cellulose, 1 wt% of lecithin and 1 wt% of castor oil; on Al by screen printing2O3Forming a thick film on the substrate, and heating for 50min in a 8000Oe magnetic field at 200 deg.C; loading 1MPa pressure on the magnetized thick film, and sintering at 1000 ℃ for 4h to prepare the BaM thick film.
Comparative example 1
BaM powder which is subjected to secondary ball milling for 50 hours and has an average particle size of 0.5 mu m and an organic carrier are mixed according to a mass ratio of 3: 1, mixing to obtain mixed slurry, wherein the organic carrier consists of the following components: 75 wt% of terpineol, 12 wt% of tributyl citrate, 5 wt% of ethyl cellulose, 4 wt% of lecithin and 4 wt% of castor oil; on Al by screen printing2O3Forming a thick film on the substrate, and heating for 50min in a 8000Oe magnetic field at 200 deg.C; loading 1MPa pressure on the magnetized thick film, and sintering at 1100 ℃ for 4h to prepare the BaM thick film.
Comparative example 2
BaM powder which is subjected to secondary ball milling for 6 hours and has an average particle size of 0.8 mu m and an organic carrier are mixed in a mass ratio of 3: 1, mixing to obtain mixed slurry, wherein the organic carrier consists of the following components: 16 wt% of bisphenol A type epoxy resin, 50 wt% of fatty amine resin, 23 wt% of terpineol, 7 wt% of tributyl citrate, 2 wt% of ethyl cellulose, 1 wt% of lecithin and 1 wt% of castor oil; on Al by screen printing2O3Forming a thick film on the substrate, and heating for 50min in a 8000Oe magnetic field at 200 deg.C; loading 1MPa pressure on the magnetized thick film, and sintering at 1100 ℃ for 4h to prepare the BaM thick film.
Comparative example 3
BaM powder which is subjected to secondary ball milling for 6 hours and has an average particle size of 0.8 mu m and an organic carrier are mixed in a mass ratio of 3: 1, mixing to obtain mixed slurry, wherein the organic carrier consists of the following components: 75 wt% of terpineol, 12 wt% of tributyl citrate, 5 wt% of ethyl cellulose, 4 wt% of lecithin and 4 wt% of castor oil; on Al by screen printing2O3On-chip shapeForming a thick film, and heating in 8000Oe magnetic field at 200 deg.C for 50 min; loading 1MPa pressure on the magnetized thick film, and sintering at 1100 ℃ for 4h to prepare the BaM thick film.
Comparative example 4
BaM powder which is subjected to secondary ball milling for 50 hours and has an average particle size of 0.5 mu m and an organic carrier are mixed according to a mass ratio of 3: 1, mixing to obtain mixed slurry, wherein the organic carrier consists of the following components: 16 wt% of bisphenol A type epoxy resin, 50 wt% of fatty amine resin, 23 wt% of terpineol, 7 wt% of tributyl citrate, 2 wt% of ethyl cellulose, 1 wt% of lecithin and 1 wt% of castor oil; on Al by screen printing2O3Forming a thick film on the substrate, and heating for 50min in a 8000Oe magnetic field at 200 deg.C; and sintering the magnetized thick film at 1100 ℃ for 4 hours without pressure to prepare the BaM thick film.
Comparative example 5
BaM powder which is subjected to secondary ball milling for 50 hours and has an average particle size of 0.5 mu m and an organic carrier are mixed according to a mass ratio of 3: 1, mixing to obtain mixed slurry, wherein the organic carrier consists of the following components: 16 wt% of bisphenol A type epoxy resin, 50 wt% of fatty amine resin, 23 wt% of terpineol, 7 wt% of tributyl citrate, 2 wt% of ethyl cellulose, 1 wt% of lecithin and 1 wt% of castor oil; on Al by screen printing2O3Forming a thick film on the substrate, and standing for 50min at normal temperature in a 8000Oe magnetic field; and sintering the magnetized thick film at 1100 ℃ for 4 hours without pressure to prepare the BaM thick film.
Performance testing
The BaM thick films of examples 1-3 and comparative examples 1-5 were characterized by XRD, SEM and hysteresis loop test.
XRD test results: as shown in FIG. 2, in which FIGS. 2a to 2C are XRD patterns of BaM thick films prepared in examples 1 to 3, respectively, and FIGS. 2d to 2h are XRDs of BaM thick films prepared in comparative examples 1 to 5, respectively, it can be seen from FIGS. 2a to 2C that the thick films prepared in examples 1 to 3 by pressure sintering have a sharp peak at (0, 0, 2l) and only a small intensity of (1, 0, 7), which indicates that the thick films prepared in examples 1 to 3 have a strong C-axis orientation; comparative example 1 compared with example 1, the organic vehicle (epoxy resin and curing agent are not contained in organic solvent) is changed, the orientation of the thick film is disordered, and the existence of the miscellaneous peaks such as (1, 0, 7), (1, 1, 4), (2, 0, 11) and the like besides the main peak (0, 0, 2l) can be found from fig. 2 d; compared with example 1, the BaM powder of comparative example 2 has short secondary ball milling time and large particle size, and under the same conditions, as can be seen from fig. 2e, the thick film prepared in comparative example 2 has many mixed peaks at (1, 0, 5), (1, 0, 7), (1, 1, 4), (2, 0, 6) and more disordered crystal orientation although the peak at (0, 0, 2l) is still dominant; comparative example 3 the organic vehicle (the organic solvent does not contain epoxy resin and curing agent) is replaced on the basis of comparative example 2, as shown in fig. 2f, the diffraction peak intensity of the thick film prepared in comparative example 3 is strongest at (1, 0, 5), the intensities of other miscellaneous peaks are correspondingly enhanced, and the intensities of the corresponding diffraction peaks of (0, 0, 2l) are all reduced; comparative example 4 is different from example 1 only in the sintering process, comparative example 4 is not subjected to the pressurization process during sintering, and from fig. 2g, it can be seen that the unpressurized BaM thick film shows a strong C-axis orientation although the peak at (0, 0, 2l) is very distinct, but the hetero peaks occur at (1, 0, 5), (1, 0, 7), (1, 1, 4); fig. 2h shows XRD pattern of comparative example 5, and the BaM thick film prepared in comparative example 5 is different from comparative example 4 in the process only in magnetizing, comparative example 5 is not heated in magnetizing, and the prepared thick film has incomplete orientation, weak peak at (0, 0, 2l), many miscellaneous peaks and high strength.
SEM test results: as shown in fig. 3, in which fig. 3a to 3c are SEM images of BaM thick films prepared in examples 1 to 3, respectively, and fig. 3d to 3h are SEM images of BaM thick films prepared in comparative examples 1 to 5, respectively; 3 a-3 c, the thick films prepared in examples 1-3 have more compact and relatively flat surfaces, which also shows that the crystal grains of the thick film are tightly compressed together through the material optimization and the improvement of the preparation process, further reducing the crystal porosity and increasing the density of the thin film; FIG. 3d is a SEM image of a thick film prepared in comparative example 1, in comparison with example 1, in which the modification of the organic vehicle causes the thick film to have some porosity while generating some cracks upon sintering; FIGS. 3e and 3f are SEM images of thick films prepared by comparative examples 2 and 3, respectively, having a larger particle size of BaM powder, BaM powder having a larger particle size resulting in a film with more pores; as can be seen from fig. 3g, the grains of the thick film prepared in comparative example 4 exhibited a distinct out-of-plane orientation, the grain growth was perfect, and the inter-grain pores were small and small; the larger difference in grain size and the presence of more voids in the thick film prepared in comparative example 5 (as shown in fig. 3 h) is presumed to be due to the lack of heating during magnetization, the organic vehicle is not primarily excluded, and excessive void generation occurs during sintering.
Hysteresis loop test results: as shown in fig. 4, in which fig. 4a to 4c are hysteresis loop test results of BaM thick films prepared in examples 1 to 3, respectively, and fig. 4d to 4h are hysteresis loop test results of BaM thick films prepared in comparative examples 1 to 5, respectively; the test results and relative densities (i.e., the ratio of the actual density to the theoretical density of the thick film) for each of the above samples are summarized in table 1 below:
TABLE 1 respective Performance parameters of the samples
As can be seen from Table 1, the thick films prepared in examples 1 to 3 have a lower particle size and a higher relative density than the comparative examples, and it can be seen from the results of the hysteresis loop test that the magnetic indexes of the thick films prepared in the examples all satisfy the requirements of the self-bias circulator material.
The characterization and test results are combined to obtain:
comparing example 1 with comparative example 1, it can be seen that when the organic solvent is not in the preferable range, the crystal orientation of the thick film has the appearance of a hybrid peak, the micro porosity is increased, the density is reduced, and the SQ value of the prepared thick film is reduced;
comparing the example 1 with the comparative example 2, it can be known that when the particle size of the powder is not in the preferred range, the crystal orientation of the thick film becomes more disordered, the density is reduced due to the increase of porosity, and the SQ value of the prepared thick film is reduced;
comparing comparative example 2 with comparative example 3, it can be seen that when the organic vehicle is not preferable, the crystal orientation of the thick film is more disordered, and the peak is the strongest; the porosity is further increased, the relative density is small, in addition, the saturation magnetization is reduced, the residual magnetization is increased, and the SQ is further reduced;
comparing example 1 with comparative example 4, it can be seen that the hot press sintering can enhance the crystal orientation of BaM thick film, reduce microscopic porosity and enhance the density of thick film, and the relative density of thick film after hot pressing is increased from 0.78 to 0.92, but the remanence ratio (SQ) is slightly decreased from 0.94 to 0.91.
Comparing example 5 with comparative example 4, it can be seen that in the magnetizing process, if there is no heating process, the porosity of the thick film becomes large, the density decreases, and in addition, the saturation magnetization, the residual magnetization and the residual magnetization ratio decrease.
The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.
Claims (10)
1. The preparation method of the hexaferrite thick film is characterized by comprising the following steps of:
(1) mixing BaM powder with organic carrier, grinding to obtain uniformly mixed slurry;
(2) coating the paste on Al by screen printing method2O3Forming a thick film on the substrate;
(3) placing the thick film and the substrate in a magnetic field, heating, magnetizing and removing glue;
(4) and sintering the magnetized thick film, and cooling to obtain the hexagonal ferrite thick film.
2. The method for preparing a hexaferrite thick film according to claim 1, wherein in step (1), the BaM powder has an average particle size of 0.3-0.7 μm.
3. The method for preparing the hexaferrite thick film according to claim 2, wherein the method for controlling the particle size of the BaM powder comprises the following steps: mixing the sintered BaM powder with glass frit, adding ball milling beads and absolute ethyl alcohol, and ball milling for 10-80h at the rotation speed of 200-300 rpm; the weight ratio of the glass frit to the BaM powder is 2% -8%, the ratio of the large, medium and small ball grinding beads in the ball grinding beads is 1:1-3:3-5, wherein the diameter of the large ball grinding bead is 11mm, the diameter of the medium ball grinding bead is 7mm, and the diameter of the small ball grinding bead is 5 mm.
4. The method for preparing the hexaferrite thick film according to claim 1, wherein in the step (1), the mass ratio of the BaM powder to the organic carrier is 2-4: 1; the organic carrier comprises the following components in percentage by mass: 10-20% of epoxy resin, 40-60% of curing agent, 15-30% of terpineol, 5-10% of tributyl citrate and other components accounting for 1-3% of the total weight of the epoxy resin, the curing agent and the terpineol; the other components are selected from at least three of polydimethylsiloxane, ethylcellulose, castor oil, lecithin, epoxy acrylate and urethane acrylate.
5. The method for preparing the hexaferrite thick film according to claim 4, wherein the epoxy resin is bisphenol A type epoxy resin, and the curing agent is aliphatic amine resin.
6. The method for preparing a hexaferrite thick film as claimed in claim 1, wherein in step (3), the intensity of the magnetic field is 8000-10000 Oe; the heating and magnetizing temperature is 150-300 ℃, and the heating and magnetizing time is 20-50 min.
7. The method for preparing the hexaferrite thick film according to claim 1, wherein in the step (4), the sintering is pressure sintering; the specific operation of the pressure sintering is as follows: placing a load on the thick film, placing the thick film in an air atmosphere, heating to a sintering temperature, and sintering for 1-10 h; the load pressure is 0.5-3MPa, the heating rate is 2-3 ℃/min, and the sintering temperature is 900-.
8. The method for preparing the hexaferrite thick film according to claim 1, wherein in the step (4), the temperature reduction rate is 2-3 ℃/min.
9. The hexaferrite thick film prepared by the preparation method of any one of claims 1-8, wherein the thickness of the hexaferrite thick film is 0.1-0.4 mm.
10. Use of a hexaferrite thick film of claim 9 in a self-biasing circulator material.
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| PCT/CN2022/100858 WO2023093025A1 (en) | 2021-11-23 | 2022-06-23 | Hexagonal ferrite thick film with high remanence ratio and low porosity, and preparation method therefor and application thereof |
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