Dielectric ceramic-ferrite composite ceramic substrate and method for manufacturing the same

Abstract

The application relates to a medium ceramic-ferrite composite ceramic substrate and a preparation method thereof. The preparation method comprises the following steps: reacting a metal nitrate solution, an iron nitrate solution and a strong alkali solution to form a suspension; placing the suspension into a reaction kettle to obtain ferrite powder with crystal nucleus; preparing a metal hydroxide solution, a ferrite suspension and a tetrabutyl titanate anhydrous ethanol solution, and centrifuging the three solutions after reaction to obtain composite powder; calcining the composite powder to obtain ferrite-medium ceramic powder with a core-shell structure; adding ferrite-medium ceramic powder, zirconium balls, a solvent, a plasticizer and a dispersant into a ball mill jar in proportion, adding a binder after ball milling for a certain time to obtain slurry; and arranging glue of the slurry green body, sintering and then manufacturing the medium ceramic-ferrite composite ceramic substrate with the core-shell structure. The medium ceramic-ferrite composite ceramic substrate prepared by the application has the advantages of low dielectric loss, high insulation resistivity and high bending strength.

Description

Technical Field

[0001] The present invention belongs to the field of microwave dielectric ceramics for the electronics industry, and in particular relates to a dielectric ceramic-ferrite composite ceramic substrate and a preparation method thereof. Background Art

[0002] Microwave dielectric ceramics specifically refer to novel electronic ceramic materials that can serve as dielectric materials within circuits operating in the microwave frequency band (300MHz-300GHz), achieving one or more functions. With the rapid development of mobile and satellite communications, especially the adoption of microwave dielectric ceramics in GPS, car phones, and pagers, microwave dielectric ceramics have gained increasing attention as a key material in the manufacture of dielectric circulators and isolators.

[0003] Ferrite material is usually a composite oxide ceramic composed of iron and other metal oxides with electromagnetic properties. Due to its high impedance, low dielectric constant, good temperature stability, high reliability and low cost, ferrite has been widely used in microwave devices such as isolators, circulators, and phase shifters. It is the core material for signal separation, filtering, and transmission.

[0004] Circulators and isolators are key components in microwave communications, the Internet of Things, artificial intelligence, and other fields. Existing circulators and isolators have problems such as large size, narrow bandwidth, and high loss, which cannot meet the application scenarios of 5G communications, artificial intelligence, etc. The development of miniaturization, large bandwidth, high power, and low loss for them, utilizing the high dielectric constant and low loss characteristics of dielectric ceramics and adopting the form of dielectric ceramic-ferrite composite, is one of the most feasible solutions to achieve miniaturization, large bandwidth, high power, and low loss of circulators and isolators.

[0005] Traditional sealing methods typically involve creating holes in the substrate surface and then inserting and bonding ferrites to create dielectric ceramic-ferrite composite substrates. This method creates a physical barrier between the ferrite materials at the interface, resulting in a significant dielectric magnetic effect and high dielectric loss. Furthermore, the difference in thermal expansion coefficients between the dielectric ceramic and ferrite leads to stress in the composite substrate after sealing, resulting in low mechanical strength and susceptibility to cracking. Summary of the Invention

[0006] The main purpose of the present invention is to provide a method for preparing a dielectric ceramic-ferrite composite ceramic substrate with low dielectric loss.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a dielectric ceramic-ferrite composite ceramic substrate comprises the following steps:

[0009] (1) Mixing metal nitrate and ferric nitrate and dissolving them in water, then adding a strong alkali solution until the pH value of the solution is alkaline, and the metal nitrate solution, ferric nitrate solution and strong alkali solution react to generate metal and iron hydroxide precipitates to form a suspension;

[0010] (2) placing the suspension into a reactor, heating it at a first preset temperature for a first preset time, causing the metal and iron hydroxide to decompose in the reactor to generate a metal-containing ferrite precipitate, washing the ferrite precipitate with distilled water and anhydrous ethanol and filtering it, and drying it for the first time to obtain a ferrite powder with a crystal core;

[0011] (3) Dispersing ferrite powder in anhydrous ethanol, and ultrasonically dispersing the ferrite surface to fully activate the ferrite to form a ferrite suspension; dropping butyl titanate into ethanol and stirring to mix uniformly to obtain an anhydrous ethanol solution of butyl titanate; adding deionized water to the metal hydroxide, stirring and dissolving at room temperature to obtain a metal hydroxide solution;

[0012] (4) At a second preset temperature, the metal hydroxide solution is dripped into the ferrite suspension while stirring at a first stirring speed so that a layer of OH is attached to the surface of the ferrite particles. - ions to obtain a mixture; adding an anhydrous ethanol solution of butyl titanate dropwise to the mixture under constant temperature conditions, continuing to react at a second stirring speed for a first preset time after the addition is completed, and then centrifuging to obtain a composite powder, then washing the composite powder with distilled water and anhydrous ethanol, performing a second drying, placing the dried composite powder in a tube furnace, and calcining it at a third preset temperature under an inert gas atmosphere to obtain a ferrite-dielectric ceramic powder having a core-shell structure;

[0013] (5) Add ferrite-dielectric ceramic powder, zirconium balls, solvent, plasticizer, dispersant, and adhesive into a ball mill in proportion, mill for a certain period of time, sieve, and remove bubbles in a vacuum to obtain a slurry;

[0014] (6) After the slurry is tape-cast, it is cut into green bodies of certain specifications and sizes. The green bodies are debinded and sintered to form dielectric ceramic-ferrite composite ceramic substrates with a core-shell structure.

[0015] The molar ratio of the dielectric ceramic to the ferrite is (2-5):1.

[0016] The metal nitrate is selected from at least one of nickel nitrate, zinc nitrate, cobalt nitrate, copper nitrate and manganese nitrate; the molar concentration of the metal nitrate solution is 0.2-1 mol / L, the molar ratio of the metal nitrate to ferric nitrate is (0.1-1):2; the molar concentration of the ferric nitrate solution is 0.2-1 mol / L;

[0017] The pH value of the solution is 8-9; the strong alkali solution is one of a sodium hydroxide solution and a potassium hydroxide solution or a mixed solution of the two, and the molar concentration of the strong alkali solution is 1-2 mol / L.

[0018] The reactor is a stainless steel reactor with a polytetrafluoroethylene lining, the first preset temperature is 100-200°C, and the first preset time is 1-2 hours; the first drying temperature is 40-60°C, the first drying time is 9-11 hours, and the filtration is performed 3-5 times.

[0019] The molar concentration of the anhydrous ethanol solution of the ferrite powder is 0.5 to 1 mol / L, the temperature of the ultrasonic dispersion is 25 to 35° C., the time of the ultrasonic dispersion is 20 to 30 minutes, the frequency of the ultrasonic dispersion is 20 to 40 kHz, and the power of the ultrasonic dispersion is 120 to 300 W.

[0020] The stirring temperature of the butyl titanate is 60-70° C., the stirring time of the butyl titanate dripping into ethanol is 30-60 min, the stirring speed is 300-600 r / min, and the molar concentration of the anhydrous ethanol solution of the butyl titanate is 0.5-1 mol / L;

[0021] The metal hydroxide is at least one of calcium hydroxide, magnesium hydroxide and barium hydroxide, the stirring time of adding deionized water to the metal hydroxide is 30 to 60 minutes, the stirring speed is 300 to 600 r / min, and the molar concentration of the metal hydroxide solution is 0.5 to 1 mol / L;

[0022] The molar ratio of the ferrite suspension, the anhydrous ethanol solution of butyl titanate and the metal hydroxide solution is 1:(2-5):(2-5).

[0023] The second preset temperature is 40-60°C, and the stirring time is 1-2h when the first stirring speed is 300-600r / min; the second stirring speed is 300-600r / min, and the first preset time is 30min-2h; the centrifugal speed is 5000-10000r / min, and the centrifugal time is 5-10min; the second drying temperature is 70-90°C, and the second drying time is 9-12h; the calcination temperature is 400-800°C, and the calcination time is 1-2h; the inert gas is Ar gas or nitrogen.

[0024] The mass percentage of the ferrite-dielectric ceramic powder is 35-50%; the mass percentage of the solvent is 20-25%, the mass percentage of the plasticizer is 0-5%, the mass percentage of the dispersant is 14-16%; and the mass percentage of the binder is 15-28%.

[0025] The solvent is selected from at least one of anhydrous ethanol, toluene, xylene, isopropyl alcohol, ethanol, acetone and ethyl acetate;

[0026] The plasticizer is selected from at least one of phthalates, glycerol benzene, dibutyl phthalate and butanediol;

[0027] The dispersant is selected from at least one of triethyl phosphate, polyethylene glycol octylphenyl ether and ammonium polyacrylate;

[0028] The binder is selected from at least one of polyvinyl butyral, polyvinyl alcohol and polypropylene alcohol;

[0029] The mass ratio of the zirconium balls to the ferrite-dielectric ceramic powder is (2-1.5):1, the rotation speed of the ball mill is 100-200 r / min, the ball milling time is 14-24 hours, and the sieve mesh size is 300-500 meshes.

[0030] The binder removal curve of the green compact is:

[0031]

[0032] RT is the room temperature during debinding; T1 is 200-400℃; T2 is 900-1000℃;

[0033] The sintering temperature rise curve of the debinded green body is:

[0034]

[0035] Among them, RT is the room temperature during sintering; T3 is the relatively low temperature section temperature; T4 is the sintering temperature; T3 is 200℃~400℃, and T4 is 1000℃~1100℃.

[0036] The green bodies are stacked in a stack of 1 to 2 pieces, zirconium oxide powder is spread between the pieces, and the green bodies are placed on a setter in a flat manner for debinding. After debinding, the green bodies are stacked in a stack of 1 to 5 pieces, zirconium oxide powder is spread between the pieces, and the green bodies are placed on a setter in a flat manner with a load of 300 to 500 g.

[0037] The dielectric ceramic-ferrite composite ceramic substrate has a core-shell structure after debinding and sintering, wherein the shell of the core-shell structure is at least one of calcium titanate, magnesium titanate and barium titanate, the shell thickness is 5 to 20 nm, and the crystal core is at least one of ferrite crystals containing nickel, zinc, cobalt, copper and manganese, with an average grain size of 1 to 2 μm;

[0038] The size of the cut green body is (50.8±0.2)×(50.8±0.2)×(0.9±0.1 mm).

[0039] The present invention also provides a dielectric ceramic-ferrite composite ceramic substrate, which is prepared according to the above preparation method.

[0040] By means of the above technical solution, the present invention has at least the following advantages:

[0041] 1. The dielectric ceramic-ferrite ceramic substrate prepared by the present invention has low dielectric loss and a high quality factor. The core-shell process of the present invention forms a core-shell structure substrate with a ferrite core and a titanate shell, reducing the impact of physical separation and thereby reducing the dielectric loss of the dielectric ceramic-ferrite ceramic substrate. For example, for a magnesium titanate ceramic substrate, the dielectric loss is reduced from 1% to approximately 0.1% at a frequency of 1 kHz.

[0042] 2. The dielectric ceramic-ferrite composite ceramic substrate prepared by the present invention has high insulation resistivity. In view of the core-shell structure characteristics of the dielectric ceramic-ferrite composite ceramic substrate, the present invention can effectively control the thickness and composition of the dielectric ceramic shell, the composition and grain size of the ferrite core, and the dispersion of the powder by controlling the ratio of dielectric ceramic to ferrite in the composite ceramic powder, the composition and addition amount of the metal nitrate solution, the composition and addition amount of the metal hydroxide solution, the synthesis temperature, the pH value of the solution, the synthesis temperature of the dielectric ceramic-ferrite powder, the debinding and sintering temperature and other parameters. The dielectric ceramic coating layer as an insulating layer can effectively prevent the leakage caused by the seepage of the low-resistivity magnetic phase in the dielectric ceramic-ferrite composite material, thereby improving the insulation resistivity of the dielectric ceramic-ferrite composite ceramic substrate after sintering. Taking the magnesium titanate ceramic substrate as an example, at 500V, the insulation resistivity is increased from the original 2.0×10 10 Ω·cm increased to 5.0×10 13 About Ω·cm.

[0043] 3. The dielectric ceramic-ferrite composite ceramic substrate prepared by the present invention exhibits high flexural strength and reduced cracking. Microwave sintering controls the core-shell microstructure of the substrate, eliminating pores between ceramic grains along the grain boundaries. This increases density and, consequently, the mechanical strength and hardness of the composite substrate. For example, performance tests conducted using a magnesium titanate ceramic substrate according to GB / T6569-2006, "Test Method for Flexural Strength of Fine Ceramics," showed an increase in flexural strength from 200 MPa to 500 MPa.

[0044] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention. DETAILED DESCRIPTION

[0045] To further illustrate the technical means and effects employed by the present invention to achieve its intended objectives, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention is provided in conjunction with preferred embodiments. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0046] Example 1

[0047] A method for preparing a dielectric ceramic-ferrite composite ceramic substrate comprises the following steps:

[0048] (1) nickel nitrate and ferric nitrate are mixed in a molar ratio of 1:2 and dissolved in distilled water. The molar concentration of the nickel nitrate solution is 0.5 mol / L, and the molar concentration of the ferric nitrate solution is 0.6 mol / L. A sodium hydroxide solution with a molar concentration of 1.5 mol / L is added dropwise to the two solutions until the pH value of the solution is 8. The nickel nitrate solution, the ferric nitrate solution and the sodium hydroxide solution react to generate metal and iron hydroxide precipitates to form a suspension;

[0049] (2) Place the suspension in a stainless steel reactor lined with polytetrafluoroethylene and heat at 150°C for 1.5 hours. The metal and iron hydroxides are decomposed by heat in the reactor to generate metal-containing ferrite precipitates. The ferrite precipitates are washed with distilled water and anhydrous ethanol and filtered three times. Dry at 50°C for 10 hours to obtain ferrite powder with crystal nuclei.

[0050] (3) According to the molar concentration of the anhydrous ethanol solution of ferrite powder being 0.8 mol / L, the ferrite powder is dispersed in anhydrous ethanol, and ultrasonically dispersed for 25 minutes at a temperature of 30°C, a frequency of 25 kHz, and a power of 180 W to fully activate the ferrite surface and form a ferrite suspension; butyl titanate is dropped into ethanol, and the stirring temperature is 65°C, the stirring speed is 300 r / min, and the stirring time is 40 minutes. Stir and mix uniformly to obtain an anhydrous ethanol solution of butyl titanate with a molar concentration of 0.8 mol / L; deionized water is added to magnesium hydroxide, and the mixture is stirred at 400 r / min at room temperature for 50 minutes to dissolve, thereby obtaining a magnesium hydroxide solution with a concentration of 0.7 mol / L;

[0051] (4) According to the molar ratio of the ferrite suspension, the anhydrous ethanol solution of butyl titanate and the magnesium hydroxide solution of 1:2:2, the magnesium hydroxide solution is dropped into the ferrite suspension at 50°C, and stirred at a first stirring speed of 400r / min for 1.5h to make a layer of OH attached to the surface of the ferrite particles. -ions to obtain a mixture; slowly and uniformly add an anhydrous ethanol solution of butyl titanate to the mixture under constant temperature conditions, continue to stir at a second stirring speed of 300r / min after the addition is completed, stir and react for 2h, butyl titanate hydrolyzes and complexes with magnesium ions to form titanate, and deposits on the surface of ferrite particles to form a shell of a core-shell structure, and then centrifuge for 10min under the condition of a rotation number of 5000r / min to obtain a composite powder, wash the composite powder with distilled water and anhydrous ethanol three times respectively, put it into a drying oven and dry it at 80°C for 10h, put the dried composite powder in a tube furnace, and calcine it at 600°C under Ar atmosphere for 1.5h to obtain a ferrite-dielectric ceramic powder with a core-shell structure, and the molar ratio of dielectric ceramic to ferrite is 2:1;

[0052] (5) Add ferrite-dielectric ceramic powder, zirconium balls, solvent, plasticizer, dispersant and binder into a ball mill according to the following ratio: the mass ratio of zirconium balls to ferrite-dielectric ceramic powder is 1.5:1. The ball mill is rotated at 100 r / min for 24 hours, and then passed through a 500-mesh sieve. After vacuum degassing, a slurry is obtained.

[0053] The mass percentage of the ferrite-dielectric ceramic powder is 35%; the mass percentage of the solvent anhydrous ethanol is 20%, the mass percentage of the plasticizer phthalate is 5%, the mass percentage of the dispersant triethyl phosphate is 15%; the mass percentage of the binder polyvinyl butyral is 25%;

[0054] (6) After the slurry is tape-casted, it is cut into green bodies with a specification size of 50.8×50.8×0.9mm. The green bodies are stacked in a stack of 2 pieces, and zirconium oxide powder is spread between the pieces. The green bodies are placed on a sintering plate in a flat manner to remove the binder. The green bodies after debinding are stacked in a stack of 3 pieces, and zirconium oxide powder is spread between the pieces. The green bodies are placed on a sintering plate in a flat manner with a load of 300 to 500g. After debinding and microwave sintering, the green bodies are made into a dielectric ceramic-ferrite composite ceramic substrate with a core-shell structure; the shell of the core-shell structure is magnesium titanate with a shell thickness of 10nm, and the crystal core is a nickel-containing ferrite crystal with an average grain size of 2μm;

[0055] The binder removal curve of the green compact is:

[0056]

[0057] RT is the room temperature during debinding; T1 is 300℃; T2 is 950℃;

[0058] The sintering temperature rise curve of the debinded green body is:

[0059]

[0060] Wherein, RT is the room temperature at sintering; T3 is the relatively low temperature section; T4 is the sintering temperature; T3 is 300℃, and T4 is 1050℃.

[0061] Example 2

[0062] A preparation method of a medium ceramic- ferrite composite ceramic substrate, comprising the following steps:

[0063] (1) zinc nitrate and iron nitrate are mixed according to a molar ratio of 0.5:2 and dissolved in distilled water, the molar concentration of the zinc nitrate solution is 0.2 mol / L, the molar concentration of the iron nitrate solution is 0.2 mol / L, sodium hydroxide solution with a molar concentration of 1 mol / L is added dropwise to the solutions of the two, until the pH value of the solution is 9, the zinc nitrate solution, the iron nitrate solution and the strong alkali solution react to generate metal and iron hydroxide precipitates, forming a suspension;

[0064] (2) the suspension is placed in a stainless steel reaction kettle containing a polytetrafluoroethylene lining and heated at 150℃ for 1.5 h, the metal and iron hydroxide are decomposed by heat in the reaction kettle to generate ferrite precipitates containing metal, the ferrite precipitates are washed with distilled water and anhydrous ethanol and suction filtered 4 times, and dried at 60℃ for 9 h to obtain ferrite powder with crystal nucleus;

[0065] (3) the ferrite powder is dispersed into anhydrous ethanol according to a molar concentration of 1 mol / L, ultrasonic dispersion is performed for 30 min under the conditions of a temperature of 35℃, a frequency of 40 KHz and a power of 300 W, so that the surface of the ferrite is fully activated to form a ferrite suspension; butyl titanate is added dropwise into ethanol, stirring is performed at a stirring temperature of 60℃ and a stirring speed of 400 r / min for 60 min, and mixing is uniform, so that an anhydrous ethanol solution of butyl titanate with a molar concentration of 0.5 mol / L is obtained; deionized water is added to calcium hydroxide and barium hydroxide, stirring is performed at 300 r / min at room temperature for 60 min to dissolve, so that a calcium hydroxide solution with a concentration of 1 mol / L and a barium hydroxide solution with a concentration of 1 mol / L are obtained;

[0066] (4) according to a molar ratio of the ferrite suspension, the anhydrous ethanol solution of butyl titanate and the metal hydroxide solution of 1:3:3, the calcium hydroxide solution and the barium hydroxide solution are added dropwise into the ferrite suspension at 40℃, and a first stirring speed of 600 r / min is used to stir for 1 h, so that a layer of OH -ions to obtain a mixture; an anhydrous ethanol solution of butyl titanate is added dropwise to the mixture under constant temperature conditions, and after the addition is completed, the stirring reaction is continued at a second stirring speed of 500 r / min for 1 hour, and then the mixture is centrifuged at a speed of 6000 r / min for 5 minutes to obtain a composite powder, and the composite powder is washed four times with distilled water and four times with anhydrous ethanol, and placed in a drying oven and dried at 70°C for 12 hours. The dried composite powder is placed in a tube furnace and calcined at 800°C under Ar atmosphere for 1 hour to obtain a ferrite-dielectric ceramic powder with a core-shell structure, and the molar ratio of dielectric ceramic to ferrite is in the range of 3:1.

[0067] (5) Add ferrite-dielectric ceramic powder, zirconium balls, solvent, plasticizer, dispersant, and binder into a ball mill according to the following ratio: the mass ratio of zirconium balls to ferrite-dielectric ceramic powder is 2:1. The ball mill is rotated at 175 r / min for 14 h, and then passed through a 400-mesh sieve. After vacuum degassing, a slurry is obtained.

[0068] The mass percentage of the ferrite-dielectric ceramic powder is 40%; the mass percentage of the solvent is 22%, the mass percentage of the plasticizer is 1%, the mass percentage of the dispersant is 16%; and the mass percentage of the binder is 21%.

[0069] The solvent is toluene, xylene and isopropanol, the proportion of the three is optional, and the total mass percentage is 22%;

[0070] The plasticizer is o-phenylenediol;

[0071] The dispersant is polyethylene glycol octylphenyl ether and ammonium polyacrylate, the ratio of the two is optional, and the total mass percentage is 16%;

[0072] The binder is polyvinyl butyral, polyvinyl alcohol and polypropylene alcohol, the proportion of the three is optional, and the total mass percentage is 21%.

[0073] (6) After the slurry is tape-casted, it is cut into green bodies with a specification size of 60×60×1mm. The green bodies are stacked one piece at a time and placed flat on a sintering plate for debinding. After debinding, 5 green bodies are stacked in a stack. Zirconium oxide powder is spread between the sheets. The green bodies are placed flat on a sintering plate with a load of 300 to 500g and sintered. After debinding and microwave sintering, the green bodies are made into a dielectric ceramic-ferrite composite ceramic substrate with a core-shell structure; the shell of the core-shell structure is calcium titanate and barium titanate, the shell thickness is 15nm, the crystal core is a zinc-containing ferrite crystal, and the average grain size is 1.5μm;

[0074] The binder removal curve of the green compact is:

[0075]

[0076] RT is the room temperature during debinding; T1 is 200℃; T2 is 1000℃;

[0077] The sintering temperature rise curve of the debinded green body is:

[0078]

[0079]

[0080] Among them, RT is the room temperature during sintering; T3 is the relatively low temperature section temperature; T4 is the sintering temperature; T3 is 400℃, and T4 is 1100℃.

[0081] Example 3

[0082] A method for preparing a dielectric ceramic-ferrite composite ceramic substrate comprises the following steps:

[0083] (1) mixing metal nitrate and ferric nitrate in a molar ratio of 0.1:2, wherein the metal nitrates are cobalt nitrate and copper nitrate, and dissolving them in distilled water, wherein the molar concentrations of the cobalt nitrate solution and the copper nitrate solution are both 1 mol / L, and the molar concentration of the ferric nitrate solution is 1 mol / L, and dropping a potassium hydroxide solution with a molar concentration of 2 mol / L into the cobalt nitrate solution, the copper nitrate solution, and the ferric nitrate solution until the pH value of the solution reaches 9, wherein the metal nitrate solution, the ferric nitrate solution, and the potassium hydroxide solution react to generate metal and iron hydroxide precipitates, thereby forming a suspension;

[0084] (2) Place the suspension in a stainless steel reactor lined with polytetrafluoroethylene and heat at 100°C for 2 hours. The metal and iron hydroxides are decomposed by heat in the reactor to generate metal-containing ferrite precipitates. The ferrite precipitates are washed with distilled water and anhydrous ethanol and filtered 5 times, and dried at 40°C for 11 hours to obtain ferrite powder with crystal nuclei.

[0085] (3) According to the molar concentration of the anhydrous ethanol solution of ferrite powder being 0.5 mol / L, the ferrite powder is dispersed in anhydrous ethanol, and ultrasonically dispersed for 20 minutes at room temperature of 25°C, a frequency of 20 kHz, and a power of 120 W to fully activate the ferrite surface and form a ferrite suspension; butyl titanate is dissolved in ethanol, and stirred at a temperature of 70°C and a stirring speed of 600 r / min for 30 minutes to mix uniformly to obtain an anhydrous ethanol solution of butyl titanate with a molar concentration of 1 mol / L; deionized water is added to calcium hydroxide, and the mixture is stirred at room temperature at 600 r / min for 30 minutes to dissolve the mixture, thereby obtaining a calcium hydroxide solution with a concentration of 0.5 mol / L;

[0086] (4) According to the molar ratio of the ferrite suspension, the anhydrous ethanol solution of butyl titanate and the metal hydroxide solution of 1:5:5, the calcium hydroxide solution was dropped into the ferrite suspension at 60°C, and stirred at a first stirring speed of 300r / min for 2h to make a layer of OH attached to the surface of the ferrite particles. - ions to obtain a mixture; an anhydrous ethanol solution of butyl titanate is added dropwise to the mixture under constant temperature conditions, and after the addition is completed, the stirring reaction is continued at a second stirring speed of 600 r / min for 30 minutes, and then the mixture is centrifuged at a speed of 10000 r / min for 5 minutes to obtain a composite powder, and the composite powder is washed three times with distilled water and three times with anhydrous ethanol, and placed in a drying oven to dry at 90°C for 9 hours. The dried composite powder is placed in a tube furnace and calcined at 400°C under Ar atmosphere for 2 hours to obtain a ferrite-dielectric ceramic powder with a core-shell structure; the molar ratio of dielectric ceramic to ferrite is 5:1.

[0087] (5) Add ferrite-dielectric ceramic powder, zirconium balls, solvent, plasticizer, dispersant, and binder into a ball mill according to the following ratio: the mass ratio of zirconium balls to ferrite-dielectric ceramic powder is 1.7:1. The ball mill is rotated at 200 r / min for 20 hours, and then passed through a 300-mesh sieve. After vacuum degassing, a slurry is obtained.

[0088] The mass percentage of the ferrite-dielectric ceramic powder is 44%; the mass percentage of the solvent anhydrous ethanol is 25%, the mass percentage of the plasticizer phthalate is 2%, the mass percentage of the dispersant triethyl phosphate is 14%; the mass percentage of the binder polyvinyl butyral is 15%;

[0089] The solvent is isopropyl alcohol;

[0090] The plasticizers are propylene glycol benzene, dibutyl phthalate and butanediol, the proportion of the three is optional, and the total mass percentage is 2%;

[0091] The dispersant is polyethylene glycol octylphenyl ether and ammonium polyacrylate, the ratio of the two is optional, and the total mass percentage is 14%;

[0092] The binder is polyvinyl alcohol.

[0093] (6), after the slurry is cast into a green body with a size of 50.6*50.6*0.8mm, the green body is stacked in two pieces, and zirconia powder is laid between the pieces, and the green body is placed on the supporting plate in a flat form for degreasing and sintering, and the sintered body is stacked in four pieces, and zirconia powder is laid between the pieces, and the sintered body is placed on the supporting plate in a flat form under a weight of 300-500g for sintering, and the green body is degreased and sintered by microwaves to form a dielectric ceramic-ferrite composite ceramic substrate with a core-shell structure; the shell of the core-shell structure is calcium titanate, the shell thickness is 20nm, and the crystal core is a cobalt and copper containing ferrite crystal with an average grain size of 1μm;

[0094] The degreasing curve of the green body is as follows:

[0095]

[0096] wherein RT is the room temperature during degreasing, T1 is 400℃, and T2 is 900℃.

[0097] The sintering temperature rising curve of the degreased sintered body is as follows:

[0098]

[0099] wherein RT is the room temperature during sintering, T3 is the temperature of the relatively low temperature stage, and T4 is the sintering temperature; T3 is 200℃, and T4 is 1000℃.

[0100] Table 1: Comparison of the properties of the various examples with the existing magnesium titanate ceramic substrate

[0101] Project Name Dielectric loss Insulation resistivity Bending strength MPa Example 1 0.6％ <![CDATA[3.8×10 13 Ohm cm]]> 378 Example 2 0.4％ <![CDATA[4.6×10 13 Ohm cm]]> 435 Example 3 0.1％ <![CDATA[5.0×10 13 Ohm cm]]> 500 Existing magnesium titanate ceramic substrate 1％ <![CDATA[2.0×10 10 Ohm cm]]> 200

[0102] wherein the dielectric loss is tested at a frequency of 1kHz, and the insulation resistivity is tested at 500V.

[0103] As can be seen from the performance test indexes in Table 1, the various performance indexes of Example 3 are optimal, because the shell thickness of Example 3 is the thickest, the shell wraps the crystal core particles to form a barrier layer, the shell layer inhibits the growth of the crystal core, the dielectric ceramic shell localizes the charge carriers, reduces the loss tangent, and reduces the conductivity, thereby reducing the dielectric loss of the dielectric ceramic-ferrite ceramic substrate; the coating layer of the dielectric ceramic as an insulation layer can effectively prevent the leakage caused by the low resistivity magnetic phase in the dielectric ceramic-ferrite composite material, thereby improving the insulation resistivity of the dielectric ceramic-ferrite composite ceramic substrate after sintering; the core-shell structure micro-morphology of the substrate is controlled by microwave sintering, which promotes the pores between the ceramic grains to be excluded along the grain boundaries, thereby improving the density and the bending strength of the composite substrate.

[0104] The formation mechanism of the core-shell structure of the present invention is as follows: the metal nitrate and ferric nitrate in the solution react with the added strong base to form metal and iron hydroxides, the metal and iron hydroxides undergo thermal decomposition in the reactor to form metal-containing ferrite powder, the ferrite powder is uniformly dispersed in the ethanol solution, ultrasonic dispersion is performed to fully activate the surface of the ferrite, and then the ferrite is dispersed in the alkaline metal hydroxide aqueous solution, so that a layer of OH is attached to the surface of the ferrite powder. - Ions, under specific temperature conditions, butyl titanate hydrolyzes and compounds with metal ions to form titanate, which is deposited on the surface of ferrite powder. After calcination, a core-shell structure powder with a ferrite core and a titanate shell is finally formed. The powder is formed by tape casting and microwave sintering to maintain the core-shell structure of the substrate.

[0105] The present invention utilizes a liquid phase method and a core-shell process to synthesize a dielectric ceramic-ferrite composite ceramic substrate having a core-shell structure. The preparation method of the present invention uses a dielectric ceramic material as a shell layer to coat ferrite magnetic particles, which can accurately control the chemical composition and reduce the sintering temperature, ultimately reducing the dielectric loss of the substrate and improving the insulation resistivity and bending strength. The preparation method of the present invention can obtain a dielectric ceramic-ferrite composite ceramic substrate with low dielectric loss, high insulation resistivity, and high bending strength.

[0106] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make slight changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a dielectric ceramic-ferrite composite ceramic substrate, characterized in that: The following steps are involved: (1) mixing a metal nitrate and ferric nitrate and dissolving them in water, then adding a strong alkali solution dropwise until the pH value of the solution is alkaline, wherein the metal nitrate solution, the ferric nitrate solution and the strong alkali solution react to generate metal and iron hydroxide precipitates to form a suspension; the metal nitrate is selected from at least one of nickel nitrate, zinc nitrate, cobalt nitrate, copper nitrate and manganese nitrate; (2) placing the suspension into a reactor, heating it at a first preset temperature for a first preset time, causing the metal and iron hydroxide to decompose in the reactor to generate a metal-containing ferrite precipitate, washing the ferrite precipitate with distilled water and anhydrous ethanol and filtering it, and drying it for the first time to obtain a ferrite powder with a crystal core; (3) dispersing ferrite powder into anhydrous ethanol, and ultrasonically dispersing the ferrite surface to fully activate the ferrite to form a ferrite suspension; dropping butyl titanate into ethanol and stirring to mix uniformly to obtain an anhydrous ethanol solution of butyl titanate; adding deionized water to the metal hydroxide, stirring and dissolving at room temperature to obtain a metal hydroxide solution; the metal hydroxide is at least one of calcium hydroxide, magnesium hydroxide and barium hydroxide; (4) At a second preset temperature, the metal hydroxide solution is dripped into the ferrite suspension while stirring at a first stirring speed so that a layer of OH is attached to the surface of the ferrite particles. - ions to obtain a mixture; adding an anhydrous ethanol solution of butyl titanate dropwise to the mixture under constant temperature, continuing to react at a second stirring speed for a second preset time after the addition is completed, and then centrifuging to obtain a composite powder, and then washing the composite powder with distilled water and anhydrous ethanol, performing a second drying, placing the dried composite powder in a tube furnace, and calcining it at a third preset temperature under an inert gas atmosphere to obtain a ferrite-dielectric ceramic powder having a core-shell structure; (5) Add ferrite-dielectric ceramic powder, zirconium balls, solvent, plasticizer, dispersant, and binder into a ball mill in proportion, mill for a certain period of time, sieve, and vacuum degas to obtain a slurry; (6) After the slurry is tape-cast, it is cut into green bodies of certain specifications and sizes. The green bodies are debinded and sintered to form dielectric ceramic-ferrite composite ceramic substrates with a core-shell structure.

2. The preparation method according to claim 1, characterized in that The molar ratio of the dielectric ceramic to the ferrite is 2 to 5:

1.

3. The preparation method according to claim 2, characterized in that The molar concentration of the metal nitrate solution is 0.2-1 mol / L, the molar ratio of the metal nitrate to ferric nitrate is (0.1-1):2; the molar concentration of the ferric nitrate solution is 0.2-1 mol / L; The pH value of the solution is 8-9; the strong alkali solution is one of a sodium hydroxide solution and a potassium hydroxide solution or a mixed solution of the two, and the molar concentration of the strong alkali solution is 1-2 mol / L.

4. The preparation method according to claim 3, characterized in that The reactor is a stainless steel reactor with a polytetrafluoroethylene lining, the first preset temperature is 100-200°C, and the first preset time is 1-2 hours; the first drying temperature is 40-60°C, the first drying time is 9-11 hours, and the filtration is performed 3-5 times.

5. The preparation method according to claim 4, characterized in that The molar concentration of the anhydrous ethanol solution of the ferrite powder is 0.5 to 1 mol / L, the temperature of the ultrasonic dispersion is 25 to 35° C., the time of the ultrasonic dispersion is 20 to 30 minutes, the frequency of the ultrasonic dispersion is 20 to 40 kHz, and the power of the ultrasonic dispersion is 120 to 300 W. The stirring temperature of the butyl titanate is 60-70° C., the stirring time of the butyl titanate dripping into ethanol is 30-60 min, the stirring speed is 300-600 r / min, and the molar concentration of the anhydrous ethanol solution of the butyl titanate is 0.5-1 mol / L; The stirring time of adding deionized water to the metal hydroxide is 30 to 60 minutes, the stirring speed is 300 to 600 r / min, and the molar concentration of the metal hydroxide solution is 0.5 to 1 mol / L; The molar ratio of the ferrite suspension, the anhydrous ethanol solution of butyl titanate and the metal hydroxide solution is 1:(2-5):(2-5).

6. The preparation method according to claim 5, characterized in that The second preset temperature is 40-60°C, and the stirring time is 1-2h when the first stirring speed is 300-600r / min; the second stirring speed is 300-600r / min, and the second preset time is 30min-2h; the centrifugal speed is 5000-10000r / min, and the centrifugal time is 5-10min; the second drying temperature is 70-90°C, and the second drying time is 9-12h; the calcination temperature is 400-800°C, and the calcination time is 1-2h; the inert gas is Ar gas or nitrogen.

7. The preparation method according to any one of claims 1 to 6, characterized in that In step (5), the mass percentage of the ferrite-dielectric ceramic powder is 35-50%, the mass percentage of the solvent is 20-25%, the mass percentage of the plasticizer is 0-5%, the mass percentage of the dispersant is 14-16%, and the mass percentage of the binder is 15-28%; The solvent is selected from at least one of anhydrous ethanol, toluene, xylene, isopropyl alcohol, ethanol, acetone and ethyl acetate; The plasticizer is selected from at least one of phthalates, glycerol benzene, dibutyl phthalate and butanediol; The dispersant is selected from at least one of triethyl phosphate, polyethylene glycol octylphenyl ether and ammonium polyacrylate; The binder is selected from at least one of polyvinyl butyral, polyvinyl alcohol and polypropylene alcohol; The mass ratio of the zirconium balls to the ferrite-dielectric ceramic powder is (2-1.5):1, the rotation speed of the ball mill is 100-200 r / min, the ball milling time is 14-24 hours, and the sieve mesh size is 300-500 meshes.

8. The preparation method according to claim 7, characterized in that The binder removal curve of the green compact is: RT is the room temperature during debinding; T1 is 200-400℃; T2 is 900-1000℃; The sintering temperature rise curve of the debinded green body is: Among them, RT is the room temperature during sintering; T3 is the relatively low temperature section temperature; T4 is the sintering temperature; T3 is 200℃~400℃, and T4 is 1000℃~1100℃.

9. The preparation method according to claim 8, characterized in that The green bodies are stacked in a stack of 1 to 2 pieces, zirconium oxide powder is spread between the pieces, and the green bodies are placed on a setter in a flat manner for debinding. After debinding, the green bodies are stacked in a stack of 1 to 5 pieces, zirconium oxide powder is spread between the pieces, and the green bodies are placed on a setter in a flat manner with a load of 300 to 500 g. The dielectric ceramic-ferrite composite ceramic substrate has a core-shell structure after debinding and sintering, wherein the shell of the core-shell structure is at least one of calcium titanate, magnesium titanate and barium titanate, the shell thickness is 5 to 20 nm, and the crystal core is at least one of ferrite crystals containing nickel, zinc, cobalt, copper and manganese, with an average grain size of 1 to 2 μm; The size of the cut green body is (50.8±0.2)×(50.8±0.2)×(0.9±0.1 mm).

10. A dielectric ceramic-ferrite composite ceramic substrate, characterized in that: It is prepared according to the preparation method according to any one of claims 1 to 9.

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