A microwave dielectric ceramic material with a core-shell structure and a preparation method thereof

Abstract

The present invention belongs to the field of ceramic materials, and particularly relates to a microwave dielectric ceramic material with a core-shell structure and a preparation method thereof. The microwave dielectric ceramic material provided by the present invention comprises: an outer shell and an inner core. The outer shell is formed by bonding an upper shell and a lower shell. The inner core is fixedly bonded in the chamber of the outer shell. The materials of the upper shell and the lower shell are Al2O3, and the material of the inner core is TiO2, CaTiO3 or SrTiO3. The inner core accounts for 0.1-3 wt% of the total mass of the microwave dielectric ceramic material. Based on the design and construction of the macroscopic core-shell structure, with Al2O3 as the outer shell of the microwave dielectric ceramic material and TiO2, CaTiO3 or SrTiO3 selected as the inner core of the microwave dielectric ceramic material, by adjusting the mass percentage of the inner core, a microwave dielectric ceramic material with both low dielectric constant, low dielectric loss and good temperature stability can be finally obtained.

Description

Technical Field

[0001] The present invention belongs to the field of ceramic materials, and particularly relates to a microwave dielectric ceramic material with a core-shell structure and a preparation method thereof. Background Art

[0002] Microwave dielectric ceramic materials are key electronic ceramic materials for microwave components such as resonators and filters widely used in modern microwave communication technologies. With the rapid development of 5G / 6G mobile communication technologies, the operating frequency ranges from the low-frequency band of microwaves to the millimeter-wave range of the high-frequency band, promoting the development of electronic components in communication systems towards high-frequency, miniaturization, integration, low power consumption, etc. The size of the dielectric resonator is negatively correlated with the square root of the material dielectric constant (ε r ). The miniaturization of resonant components requires as high a dielectric constant as possible. However, a higher dielectric constant will make the size of the resonant components too small, bringing new problems such as preparation and processing. At the same time, the phase delay generated by the propagation of electromagnetic waves in the medium is proportional to the square root of the material dielectric constant. A low dielectric constant can effectively improve the signal transmission rate and reduce the time delay. A low dielectric loss (i.e., a high Q×f value, where Q is the quality factor and f is the resonant frequency) can reduce the energy loss during signal transmission, enabling the component to have a high signal-to-noise ratio and good frequency selection characteristics. A near-zero temperature coefficient of resonant frequency (τ f ≤±10 ppm / °C) can enable the component to maintain good performance stability within a relatively wide temperature range.

[0003] Currently, microwave ceramics with a low dielectric constant can have a relatively high Q×f value, but their τ f often has a large negative value, restricting their application in microwave components such as resonators. For the adjustment of near-zero τ f , the traditional method is to introduce a material with a large τ f value with the opposite sign into the matrix material, and achieve it by forming a composite phase or solid solution through mixed sintering. However, it is relatively easy to produce situations such as heterophases due to chemical reactions or local composition inhomogeneity, and the Q×f value deteriorates significantly. It is difficult to adjust the near-zero τ f to the expected value. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a microwave dielectric ceramic material with a core-shell structure and a preparation method thereof. Through the macroscopic core-shell structure design of the microwave dielectric ceramic material, under the condition that the mass percentage of its inner core is a relatively small value, the adjustment of near-zero τ f of the microwave dielectric ceramic material is realized. The provided microwave dielectric ceramic material can have both a low dielectric constant, low dielectric loss, and good temperature stability.

[0005] The present invention provides a microwave dielectric ceramic material with a core-shell structure, comprising: an outer shell and an inner core. The outer shell is formed by bonding an upper shell and a lower shell. The inner core is adhesively fixed in the chamber of the outer shell. The materials of the upper shell and the lower shell are Al2O3, and the material of the inner core is TiO2, CaTiO3 or SrTiO3. The inner core accounts for 0.1 to 3 wt% of the total mass of the microwave dielectric ceramic material.

[0006] Preferably, the inner core accounts for 0.2 to 1.6 wt% of the total mass of the microwave dielectric ceramic material.

[0007] The present invention provides a preparation method of a microwave dielectric ceramic material with a core-shell structure, comprising the following steps:

[0008] Place the inner core in the chamber formed by the upper shell and the lower shell, and use glue to adhesively fix the upper shell, the inner core and the lower shell to obtain a microwave dielectric ceramic material with a core-shell structure.

[0009] The materials of the upper shell and the lower shell are Al2O3, and the material of the inner core is TiO2, CaTiO3 or SrTiO3. The inner core accounts for 0.1 to 3 wt% of the total mass of the microwave dielectric ceramic material.

[0010] Preferably, the preparation steps of the inner core include:

[0011] a) Weigh corresponding raw materials according to the chemical formula of the inner core material to be prepared. After pre-sintering, ball milling, drying and sieving, obtain pre-sintered powder.

[0012] b) Mix and grind the pre-sintered powder with an aqueous binder solution, granulate and sieve to obtain powder particles.

[0013] c) Add the powder particles into a mold for pressing to obtain a ceramic green body.

[0014] d) Sinter the ceramic green body to obtain the inner core.

[0015] Preferably, in step a), if the inner core material to be prepared is TiO2, the raw material is TiO2 powder, the pre-sintering temperature is 950 to 1075 °C, and the pre-sintering time is 2 to 6 h.

[0016] If the inner core material to be prepared is CaTiO3, the raw materials are CaCO3 powder and TiO2 powder, the pre-sintering temperature is 1050 to 1200 °C, and the pre-sintering time is 2 to 6 h.

[0017] If the core material to be prepared is SrTiO3, the raw materials are SrCO3 powder and TiO2 powder, the pre-sintering temperature is 1050 - 1200 °C, and the pre-sintering time is 2 - 6 h.

[0018] Preferably, in step a), the rotation speed of the ball milling is 200 - 400 r / min, and the time is 3 - 6 h; the mesh number of the sieve for sieving is 60 - 120 mesh.

[0019] Preferably, in step b), the binder aqueous solution is a PVA aqueous solution; the concentration of the binder aqueous solution is 3 - 6 wt%; the mesh number of the sieve for sieving is 60 - 120 mesh.

[0020] Preferably, in step d), before the ceramic green body is sintered, it is first kept at 550 - 600 °C for 2 - 6 h to remove the binder.

[0021] Preferably, in step d), if the core material to be prepared is TiO2, the sintering temperature is 1150 - 1350 °C, and the sintering time is 2 - 6 h;

[0022] If the core material to be prepared is CaTiO3, the sintering temperature is 1200 - 1400 °C, and the sintering time is 2 - 6 h;

[0023] If the core material to be prepared is SrTiO3, the sintering temperature is 1200 - 1400 °C, and the sintering time is 2 - 6 h.

[0024] Preferably, the glue is 502 glue.

[0025] Compared with the prior art, the present invention provides a microwave dielectric ceramic material with a core-shell structure and a preparation method thereof. The microwave dielectric ceramic material provided by the present invention includes: an outer shell and a core. The outer shell is formed by bonding an upper shell and a lower shell. The core is bonded and fixed in the chamber of the outer shell. The materials of the upper shell and the lower shell are Al2O3, and the material of the core is TiO2, CaTiO3 or SrTiO3; the core accounts for 0.1 - 3 wt% of the total mass of the microwave dielectric ceramic material. Based on the design and construction of the macroscopic core-shell structure, using Al2O3 as the outer shell of the microwave dielectric ceramic material and selecting TiO2, CaTiO3 or SrTiO3 as the core of the microwave dielectric ceramic material, by adjusting the mass percentage of the core, a microwave dielectric ceramic material with both low dielectric constant, low dielectric loss and good temperature stability can be finally obtained. Compared with the traditional method of using multi-phase mixed sintering to adjust τ fThe method of the present invention makes full use of the designability and processability of the dielectric ceramic structure, can avoid chemical reactions or thermal diffusion between multiple phases, etc., and can achieve nearly zero τ under the condition that the mass percentage of the inner core is a small value. f The adjustment is conducive to realizing the coordinated regulation of the microwave dielectric properties of the dielectric ceramic and has great application value in communication components such as dielectric resonators. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0027] Figure 1 FIG. 11 is a schematic structural diagram of a microwave dielectric ceramic material with the same dimensions of the upper and lower shells provided by an embodiment of the present invention;

[0028] Figure 2 FIG. 15 is a schematic structural diagram of a microwave dielectric ceramic material with different dimensions of the upper and lower shells provided by an embodiment of the present invention.

[0029] Description of the reference numerals: 1 is the upper shell, 2 is the lower shell, 3 is the blind hole, and 4 is the inner core. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The following clearly and completely describes the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] The present invention provides a microwave dielectric ceramic material with a core-shell structure, including: an outer shell and an inner core. The outer shell is composed of an upper shell and a lower shell bonded together. The inner core is bonded and fixed in the cavity of the outer shell. The materials of the upper shell and the lower shell are Al2O3, and the material of the inner core is TiO2, CaTiO3 or SrTiO3.

[0032] In the microwave dielectric ceramic material provided by the present invention, the materials of the upper shell and the lower shell are preferably single crystal (sapphire) Al2O3 or polycrystalline Al2O3.

[0033] In the microwave dielectric ceramic material provided by the present invention, a blind hole for accommodating the inner core is provided on the inner side of the upper shell and / or the lower shell. In some embodiments provided by the present invention, the upper shell and the lower shell have the same dimensions, and blind holes are provided on the inner sides of both, and the structure of the corresponding microwave dielectric ceramic material is as Figure 1 shown. In some embodiments provided by the present invention, the upper shell and the lower shell have different dimensions, and a blind hole is provided only on the inner side of the larger-sized shell, and the structure of the corresponding microwave dielectric ceramic material is as Figure 2 shown.

[0034] In the microwave dielectric ceramic material provided by the present invention, the outer shape of the outer shell is preferably a cylinder; the diameter of the cylinder is preferably 9.5 - 10.5 mm, specifically, it can be 9.5 mm, 9.6 mm, 9.7 mm, 9.8 mm, 9.9 mm, 10 mm, 10.1 mm, 10.2 mm, 10.3 mm, 10.4 mm or 10.5 mm; the height is preferably 4.5 - 6 mm, specifically, it can be 4.5 mm, 4.6 mm, 4.7 mm, 4.8 mm, 4.9 mm, 5 mm, 5.1 mm, 5.2 mm, 5.3 mm, 5.4 mm, 5.5 mm, 5.6 mm, 5.7 mm, 5.8 mm, 5.9 mm or 6 mm.

[0035] In the microwave dielectric ceramic material provided by the present invention, the shape of the inner core is preferably a cube, a cuboid or a cylinder; the length, width and height of the cube and the cuboid are independently preferably 0.5 - 2 mm, specifically, it can be 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm or 2 mm; the diameter of the cylinder is preferably 1 - 5 mm, specifically, it can be 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm, and the height of the cylinder is preferably 0.1 - 1 mm, specifically, it can be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm.

[0036] In the microwave dielectric ceramic material provided by the present invention, the core accounts for 0.1 to 3 wt% of the total mass of the microwave dielectric ceramic material, preferably 0.2 to 1.6 wt%, and specifically may be 0.2 wt%, 0.21 wt%, 0.24 wt%, 0.25 wt%, 0.26 wt%, 0.28 wt%, 0.3 wt%, 0.31 wt%, 0.35 wt%, 0.4 wt%, 0.49 wt%, 0.5 wt%, 0.54 wt%, 0.56 wt%, 0.58 wt%, 0.6 wt%, 0.7 wt%, 0.75 wt%, 0.76 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.03 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.51 wt% or 1.6 wt%.

[0037] In the microwave dielectric ceramic material provided by the present invention, the core is preferably located at the center of the microwave dielectric ceramic material.

[0038] In the microwave dielectric ceramic material provided by the present invention, the amount of glue used for bonding is very small, and its influence on the quality of the microwave dielectric ceramic material can be ignored.

[0039] In the microwave dielectric ceramic material provided by the present invention, the relative dielectric constant ε of the microwave dielectric ceramic material r is preferably 9.2 to 13.0, the Q×f value is preferably 90000 to 322800 GHz, and the resonance frequency temperature coefficient τ f is preferably -50.0 ppm / °C to +250.0 ppm / °C.

[0040] The present invention also provides a preparation method of the microwave dielectric ceramic material according to the above technical solution, comprising the following steps:

[0041] Place the core in the chamber formed by the upper shell and the lower shell, and use glue to bond and fix the upper shell, the core and the lower shell to obtain a microwave dielectric ceramic material with a core-shell structure.

[0042] In the preparation method provided by the present invention, the preparation steps of the core preferably include:

[0043] a) Weigh the corresponding raw materials according to the chemical formula of the core material to be prepared, and obtain pre-sintered powder after pre-sintering, ball milling, drying and sieving;

[0044] b) Mix and grind the pre-sintered powder with an aqueous binder solution, granulate and sieve to obtain powder particles;

[0045] c) Add the powder particles into a mold for pressing to obtain a ceramic green body;

[0046] d) Sinter the green ceramic body to obtain the core.

[0047] In the above-mentioned core preparation steps provided by the present invention, in step a), if the core material to be prepared is TiO2, the raw material is preferably TiO2 powder, the pre-sintering temperature is preferably 950 - 1075 °C, specifically 950 °C, 975 °C, 1000 °C, 1025 °C, 1050 °C or 1075 °C, and the pre-sintering time is preferably 2 - 6 h, specifically 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h.

[0048] In the above-mentioned core preparation steps provided by the present invention, in step a), if the core material to be prepared is CaTiO3, the raw materials are preferably CaCO3 powder and TiO2 powder, the pre-sintering temperature is preferably 1050 - 1200 °C, specifically 1050 °C, 1075 °C, 1100 °C, 1125 °C, 1150 °C, 1175 °C or 1200 °C, and the pre-sintering time is preferably 2 - 6 h, specifically 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h.

[0049] In the above-mentioned core preparation steps provided by the present invention, in step a), if the core material to be prepared is SrTiO3, the raw materials are preferably SrCO3 powder and TiO2 powder, the pre-sintering temperature is preferably 1050 - 1200 °C, specifically 1050 °C, 1075 °C, 1100 °C, 1125 °C, 1150 °C, 1175 °C or 1200 °C, and the pre-sintering time is preferably 2 - 6 h, specifically 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h.

[0050] In the above-mentioned core preparation steps provided by the present invention, in step a), the ball milling is preferably carried out in the presence of zirconia balls and anhydrous ethanol; the rotation speed of the ball milling is preferably 200 - 400 r / min, specifically 200 r / min, 250 r / min, 300 r / min, 350 r / min or 400 r / min; the ball milling time is preferably 3 - 6 h, specifically 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h; the mesh number of the sieve for sieving is preferably 60 - 120 mesh, specifically 60 mesh, 70 mesh, 80 mesh, 100 mesh or 120 mesh.

[0051] In the above-mentioned core preparation steps provided by the present invention, in step b), the aqueous binder solution is preferably an aqueous PVA solution; the concentration of the aqueous binder solution is preferably 3-6 wt%, specifically it can be 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt% or 6 wt%; the mesh number of the sieve for sieving is preferably 60-120 meshes, specifically it can be 60 meshes, 70 meshes, 80 meshes, 100 meshes or 120 meshes.

[0052] In the above-mentioned core preparation steps provided by the present invention, in step d), before the green ceramic body is sintered, it is preferably pre-heated at 550-600 °C for 2-6 h to remove the binder. Among them, the temperature of the heat preservation can specifically be 550 °C, 560 °C, 570 °C, 580 °C, 590 °C or 600 °C; the time of the heat preservation can specifically be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h.

[0053] In the above-mentioned core preparation steps provided by the present invention, in step d), if the core material to be prepared is TiO2, the sintering temperature is preferably 1150-1350 °C, specifically it can be 1150 °C, 1175 °C, 1200 °C, 1225 °C, 1250 °C, 1275 °C, 1300 °C, 1325 °C or 1350 °C, and the sintering time is preferably 2-6 h, specifically it can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h.

[0054] In the above-mentioned core preparation steps provided by the present invention, in step d), if the core material to be prepared is CaTiO3, the sintering temperature is preferably 1200-1400 °C, specifically it can be 1200 °C, 1225 °C, 1250 °C, 1275 °C, 1300 °C, 1325 °C, 1350 °C, 1375 °C or 1400 °C, and the sintering time is preferably 2-6 h, specifically it can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h.

[0055] In the above-mentioned core preparation steps provided by the present invention, in step d), if the core material to be prepared is SrTiO3, the sintering temperature is preferably 1200-1400 °C, specifically it can be 1200 °C, 1225 °C, 1250 °C, 1275 °C, 1300 °C, 1325 °C, 1350 °C, 1375 °C or 1400 °C, and the sintering time is preferably 2-6 h, specifically it can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h.

[0056] In the above-mentioned core preparation steps provided by the present invention, preferably, the following steps are further included: processing the prepared core in terms of size by wire cutting or other means.

[0057] In the preparation method provided by the present invention, there are no special limitations on the sources of the upper shell and the lower shell, which can be commercially available or prepared according to the conventional methods in the art.

[0058] In the preparation method provided by the present invention, the glue is preferably 502 glue; the amount of glue used is very small, and its influence on the quality of the microwave dielectric ceramic material can be ignored.

[0059] The technical solution provided by the present invention is based on the design and construction of a macroscopic core-shell structure. Using Al2O3 as the shell of the microwave dielectric ceramic material, and selecting TiO2, CaTiO3 or SrTiO3 as the core of the microwave dielectric ceramic material. By adjusting the mass percentage of the core, a microwave dielectric ceramic material with both low dielectric constant, low dielectric loss and good temperature stability can be finally obtained. Compared with the traditional method of using multi-phase mixed sintering to adjust τ f The present invention makes full use of the designability and processability of the dielectric ceramic structure, can avoid the occurrence of chemical reactions or thermal diffusion between multiple phases, etc. Under the condition that the mass percentage of the core is a small value, nearly zero τ f can be adjusted, which is beneficial to realizing the coordinated regulation of the microwave dielectric properties of the dielectric ceramic and has great application value in communication components such as dielectric resonators.

[0060] For the sake of clarity, the following is a detailed description through the following examples and comparative examples.

[0061] Comparative Example 1

[0062] (1) Processing of the Al2O3 ceramic shell: Select single-crystal (sapphire) Al2O3 ceramic as the shell, where the thickness of the lower shell is 3 mm and the thickness of the upper shell is 2 mm; Process a square blind hole at the center position of the inner surface of the lower shell, with the length of the blind hole being 3 mm, the width being 3 mm, and the depth being 1 mm.

[0063] (2) Bond the upper shell and the lower shell with 502 glue to obtain a microwave dielectric ceramic with a central hole.

[0064] (3) Test the microwave dielectric properties of the ceramic: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic prepared in step (2).

[0065] Example 1

[0066] (1)Pre-sintering of the core TiO2 raw material: After pre-sintering the TiO2 powder at 1050 °C for 4 h, it was ball-milled for 4 h at a ball-milling speed of 300 r / min. After the powder was dried, it was sieved through a 80-mesh sieve to obtain the pre-sintered powder.

[0067] (2)Preparation of the core TiO2 ceramic particles: The pre-sintered powder obtained in step (1) was added to a 5 wt% PVA aqueous solution. After grinding, granulating, and sieving through an 80-mesh sieve, TiO2 ceramic particles were obtained.

[0068] (3)Preparation of the core TiO2 ceramic green body: The ceramic particles obtained in step (2) were added to a mold and pressed to obtain a ceramic green body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0069] (4)Sintering of the core TiO2 ceramic: The ceramic green body obtained in step (3) was first kept at 600 °C for 4 h to remove the binder, and then sintered at 1250 °C for 4 h to obtain a well-sintered TiO2 ceramic.

[0070] (5)Processing of the core TiO2 ceramic: The ceramic obtained in step (4) was processed into small blocks with a length of 1.5 mm × width of 1.5 mm × height of 1 mm by wire cutting or other methods.

[0071] (6)Processing of the shell Al2O3 ceramic: Single-crystal (sapphire) Al2O3 ceramic was selected as the shell, with the thickness of the lower shell being 3 mm and the thickness of the upper shell being 2 mm; a square blind hole was machined at the center of the inner surface of the lower shell, with the length of the blind hole being 3 mm, the width being 3 mm, and the depth being 1 mm.

[0072] (7)The Al2O3 lower shell, TiO2 core, and Al2O3 upper shell obtained in steps (5) and (6) were sequentially bonded in the order from bottom to top with 502 glue to obtain a microwave dielectric ceramic with a core-shell structure; the structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 0.60 wt%.

[0073] (8)Testing of the microwave dielectric properties of the ceramic: The microwave dielectric properties of the ceramic obtained in step (7) were tested using a network analyzer and a supporting fixture.

[0074] Example 2

[0075] (1)Pre-sintering of the core TiO2 raw material: After pre-sintering the TiO2 powder at 1050 °C for 4 h, it was ball-milled for 4 h at a ball-milling speed of 300 r / min. After the powder was dried, it was sieved through a 80-mesh sieve to obtain the pre-sintered powder.

[0076] (2)Preparation of core TiO₂ ceramic particles: Add the pre-sintered powder obtained in step (1) to a 5wt% PVA aqueous solution. After grinding, granulating, and passing through an 80-mesh sieve, TiO₂ ceramic particles are obtained.

[0077] (3)Preparation of green body of core TiO₂ ceramic: Add the ceramic particles obtained in step (2) into a mold and press to obtain a green body of ceramic with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0078] (4)Sintering of core TiO₂ ceramic: First, keep the green body of ceramic obtained in step (3) at 600 °C for 4 h to remove the binder, and then sinter at 1250 °C for 4 h to obtain a well-sintered TiO₂ ceramic.

[0079] (5)Processing of core TiO₂ ceramic: Process the ceramic obtained in step (4) into small blocks with a length of 1.85 mm × width of 1.85 mm × height of 1 mm by wire cutting or other methods.

[0080] (6)Processing of shell Al₂O₃ ceramic: Select single-crystal (sapphire) Al₂O₃ ceramic as the shell, where the thickness of the lower shell is 3 mm and the thickness of the upper shell is 2 mm; Process a square blind hole at the center position of the inner surface of the lower shell, with the length of the blind hole being 3 mm, the width being 3 mm, and the depth being 1 mm.

[0081] (7)Bond the Al₂O₃ lower shell, TiO₂ core, and Al₂O₃ upper shell obtained in step (5) and step (6) in sequence from bottom to top with 502 glue to prepare a microwave dielectric ceramic with a core-shell structure; The structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 0.76wt%.

[0082] (8)Testing of microwave dielectric properties of ceramic: Use a network analyzer and a matching fixture to test the microwave dielectric properties of the ceramic obtained in step (7).

[0083] Example 3

[0084] (1)Pre-sintering of core TiO₂ raw material: Pre-sinter TiO₂ powder at 1050 °C for 4 h, then ball-mill for 4 h at a ball-mill speed of 300 r / min. After drying the powder, pass it through an 80-mesh sieve to obtain pre-sintered powder.

[0085] (2)Preparation of core TiO₂ ceramic particles: Add the pre-sintered powder obtained in step (1) to a 5wt% PVA aqueous solution. After grinding, granulating, and passing through an 80-mesh sieve, TiO₂ ceramic particles are obtained.

[0086] (3)Preparation of the green body of the core TiO2 ceramic: The ceramic particles obtained in step (2) are added to a mold and pressed to obtain a green body of the ceramic with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0087] (4)Sintering of the core TiO2 ceramic: The green body of the ceramic obtained in step (3) is first kept at 600 °C for 4 h to remove the binder, and then sintered at 1250 °C for 4 h to obtain a well-sintered TiO2 ceramic.

[0088] (5)Processing of the core TiO2 ceramic: The ceramic obtained in step (4) is processed into small blocks with a length of 2 mm × width of 2 mm × height of 1 mm by wire cutting or other means.

[0089] (6)Processing of the shell Al2O3 ceramic: Single crystal (sapphire) Al2O3 ceramic is selected as the shell, with the thickness of the lower shell being 3 mm and the thickness of the upper shell being 2 mm; a square blind hole is processed at the center position of the inner surface of the lower shell, with the length of the blind hole being 3 mm, the width being 3 mm, and the depth being 1 mm.

[0090] (7)The Al2O3 lower shell, TiO2 core, and Al2O3 upper shell obtained in steps (5) and (6) are sequentially bonded in the order from bottom to top with 502 glue to obtain a microwave dielectric ceramic with a core-shell structure; the structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 1.03 wt%.

[0091] (8)Testing of the microwave dielectric properties of the ceramic: The microwave dielectric properties of the ceramic obtained in step (7) are tested using a network analyzer and a supporting fixture.

[0092] Example 4

[0093] (1)Pre-sintering of the core TiO2 raw material: After pre-sintering the TiO2 powder at 1050 °C for 4 h, it is ball-milled for 4 h at a ball-milling speed of 300 r / min. After the powder is dried, it is passed through an 80-mesh sieve to obtain the pre-sintered powder.

[0094] (2)Preparation of the core TiO2 ceramic particles: The pre-sintered powder obtained in step (1) is added to a 5 wt% aqueous PVA solution, and after grinding, granulating, and passing through an 80-mesh sieve, TiO2 ceramic particles are obtained.

[0095] (3)Preparation of the green body of the core TiO2 ceramic: The ceramic particles obtained in step (2) are added to a mold and pressed to obtain a green body of the ceramic with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0096] (4)Sintering of the core TiO2 ceramic: The green ceramic body prepared in step (3) is first kept at 600 °C for 4 h to remove the binder, and then sintered at 1250 °C for 4 h to obtain a well-sintered TiO2 ceramic.

[0097] (5)Processing of the core TiO2 ceramic: The ceramic obtained in step (4) is processed into small blocks with a length of 2.5 mm × width of 2.5 mm × height of 1 mm by wire cutting or other means.

[0098] (6)Processing of the shell Al2O3 ceramic: Single crystal (sapphire) Al2O3 ceramic is selected as the shell, with the thickness of the lower shell being 3 mm and the thickness of the upper shell being 2 mm; a square blind hole is processed at the center position of the inner surface of the lower shell, with the length of the blind hole being 3 mm, the width being 3 mm, and the depth being 1 mm.

[0099] (7)The Al2O3 lower shell, TiO2 core, and Al2O3 upper shell prepared in step (5) and step (6) are sequentially bonded in the order from bottom to top with 502 glue to obtain a microwave dielectric ceramic with a core-shell structure; the structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 1.51 wt%.

[0100] (8)Testing of the microwave dielectric properties of the ceramic: The microwave dielectric properties of the ceramic prepared in step (7) are tested using a network analyzer and a supporting fixture.

[0101] The microwave dielectric properties of the dielectric ceramics prepared in Comparative Example 1 and Examples 1 to 4 are shown in Table 1:

[0102] Table 1

[0103]

[0104] Comparative Example 2

[0105] (1)Processing of the shell Al2O3 ceramic: Polycrystalline Al2O3 ceramic is selected as the shell, with the thickness of the lower shell being 3 mm and the thickness of the upper shell being 2 mm; a square blind hole is processed at the center position of the inner surface of the lower shell, with the length of the blind hole being 3 mm, the width being 3 mm, and the depth being 1 mm.

[0106] (2)The upper shell and the lower shell are bonded with 502 glue to obtain a microwave dielectric ceramic with a central hole.

[0107] (3)Testing of the microwave dielectric properties of the ceramic: The microwave dielectric properties of the ceramic prepared in step (2) are tested using a network analyzer and a supporting fixture.

[0108] Example 5

[0109] (1)Pre-sintering of the core TiO2 raw material: After pre-sintering TiO2 powder at 1050 °C for 4 h, it was ball-milled for 4 h at a rotational speed of 300 r / min. After the powder was dried, it was sieved through a 80-mesh sieve to obtain the pre-sintered powder.

[0110] (2)Preparation of core TiO2 ceramic particles: The pre-sintered powder obtained in step (1) was added to a 5 wt% aqueous PVA solution. After grinding, granulating, and sieving through an 80-mesh sieve, TiO2 ceramic particles were obtained.

[0111] (3)Preparation of the core TiO2 ceramic green body: The ceramic particles obtained in step (2) were added to a mold and pressed to obtain a ceramic green body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0112] (4)Sintering of the core TiO2 ceramic: The ceramic green body obtained in step (3) was first held at 600 °C for 4 h to remove the binder, and then sintered at 1250 °C for 4 h to obtain a well-sintered TiO2 ceramic.

[0113] (5)Processing of the core TiO2 ceramic: The ceramic obtained in step (4) was processed into small blocks with a length of 1.5 mm × width of 1.5 mm × height of 0.75 mm by wire cutting or other means.

[0114] (6)Processing of the shell Al2O3 ceramic: Al2O3 polycrystalline ceramic was selected as the shell, with the thickness of the lower shell being 3 mm and the thickness of the upper shell being 2 mm; a square blind hole was machined at the center of the inner surface of the lower shell, with the length of the blind hole being 3 mm, the width being 3 mm, and the depth being 1 mm.

[0115] (7)The Al2O3 lower shell, TiO2 core, and Al2O3 upper shell obtained in steps (5) and (6) were adhesively bonded in sequence from bottom to top with 502 glue to obtain a microwave dielectric ceramic with a core-shell structure; the structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 0.49 wt%.

[0116] (8)Testing of the microwave dielectric properties of the ceramic: The microwave dielectric properties of the ceramic obtained in step (7) were tested using a network analyzer and a supporting fixture.

[0117] Example 6

[0118] (1)Pre-sintering of the core TiO2 raw material: After pre-sintering TiO2 powder at 1050 °C for 4 h, it was ball-milled for 4 h at a rotational speed of 300 r / min. After the powder was dried, it was sieved through a 80-mesh sieve to obtain the pre-sintered powder.

[0119] (2)Preparation of core TiO2 ceramic particles: The pre-sintered powder obtained in step (1) was added to a 5wt% PVA aqueous solution. After grinding, granulating, and passing through an 80-mesh sieve, TiO2 ceramic particles were obtained.

[0120] (3)Preparation of green body of core TiO2 ceramic: The ceramic particles obtained in step (2) were added to a mold and pressed to obtain a green body of ceramic with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0121] (4)Sintering of core TiO2 ceramic: The green body of ceramic obtained in step (3) was first kept at 600 °C for 4 h to remove the binder, and then sintered at 1250 °C for 4 h to obtain a well-sintered TiO2 ceramic.

[0122] (5)Processing of core TiO2 ceramic: The ceramic obtained in step (4) was processed into small blocks with a length of 1.9 mm × width of 1.9 mm × height of 0.75 mm by wire cutting or other means.

[0123] (6)Processing of shell Al2O3 ceramic: Alumina polycrystalline ceramic was selected as the shell, with the thickness of the lower shell being 3 mm and the thickness of the upper shell being 2 mm; a square blind hole was processed at the center position of the inner surface of the lower shell, with the length of the blind hole being 3 mm, the width being 3 mm, and the depth being 1 mm.

[0124] (7)The Al2O3 lower shell, TiO2 core, and Al2O3 upper shell obtained in steps (5) and (6) were adhesively bonded in sequence from bottom to top with 502 glue to prepare a microwave dielectric ceramic with a core-shell structure; the structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 0.75wt%. (8) Testing of microwave dielectric properties of ceramic: The microwave dielectric properties of the ceramic prepared in step (7) were tested using a network analyzer and a matching fixture.

[0125] Example 7

[0126] (1)Pre-sintering of core TiO2 raw material: The TiO2 powder was pre-sintered at 1050 °C for 4 h, then ball-milled for 4 h at a ball-milling speed of 300 r / min. After the powder was dried, it was passed through an 80-mesh sieve to obtain the pre-sintered powder.

[0127] (2)Preparation of core TiO2 ceramic particles: The pre-sintered powder obtained in step (1) was added to a 5wt% PVA aqueous solution. After grinding, granulating, and passing through an 80-mesh sieve, TiO2 ceramic particles were obtained.

[0128] (3)Preparation of green body of core TiO2 ceramic: The ceramic particles obtained in step (2) were added to a mold and pressed to obtain a green body of ceramic with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0129] (4)Sintering of the core TiO2 ceramic: The green ceramic body prepared in step (3) is first kept at 600 °C for 4 h to remove the binder, and then sintered at 1250 °C for 4 h to obtain a well-sintered TiO2 ceramic.

[0130] (5)Processing of the core TiO2 ceramic: The ceramic prepared in step (4) is processed into small blocks with a length of 2.25 mm × width of 2.25 mm × height of 0.75 mm by wire cutting or other means.

[0131] (6)Processing of the shell Al2O3 ceramic: Select polycrystalline Al2O3 ceramic as the shell, where the thickness of the lower shell is 3 mm and the thickness of the upper shell is 2 mm; a square blind hole is processed at the center position of the inner surface of the lower shell, with the length of the blind hole being 3 mm, the width being 3 mm, and the depth being 1 mm.

[0132] (7)The Al2O3 lower shell, TiO2 core, and Al2O3 upper shell prepared in steps (5) and (6) are sequentially bonded with 502 glue in the order from bottom to top to obtain a microwave dielectric ceramic with a core-shell structure; the structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 1.03 wt%. (8) Testing of the microwave dielectric properties of the ceramic: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic prepared in step (7).

[0133] The microwave dielectric properties of the dielectric ceramics prepared in Comparative Example 2 and Examples 5 to 7 are shown in Table 2:

[0134] Table 2

[0135]

[0136] Example 8

[0137] (1)Pre-sintering of the core CaTiO3 raw materials: Weigh CaCO3 powder and TiO2 powder according to the chemical formula, ball mill for 4 h at a ball mill speed of 300 r / min. After the powder is dried and passed through an 80-mesh sieve, the mixed powder is pre-sintered at 1100 °C for 4 h, then ball milled for 4 h at a ball mill speed of 300 r / min. After the powder is dried and passed through an 80-mesh sieve, the pre-sintered powder is obtained.

[0138] (2)Preparation of the core CaTiO3 ceramic particles: Add the pre-sintered powder prepared in step (1) to a 5 wt% PVA aqueous solution, and after grinding, granulating, and passing through an 80-mesh sieve, the CaTiO3 ceramic particles are obtained.

[0139] (3)Preparation of the core CaTiO3 ceramic green body: The ceramic particles prepared in step (2) are added to a mold and pressed to obtain a ceramic green body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0140] (4) Sintering of the core CaTiO₃ ceramic: The green ceramic body obtained in step (3) is first kept at 600 °C for 4 h to remove the binder, and then sintered at 1300 °C for 4 h to obtain a well-sintered CaTiO₃ ceramic.

[0141] (5) Processing of the core CaTiO₃ ceramic: The ceramic obtained in step (4) is processed into small blocks with a length of 1 mm × width of 1 mm × height of 1 mm by wire cutting or other means.

[0142] (6) Processing of the shell Al₂O₃ ceramic: Single crystal (sapphire) Al₂O₃ ceramic is selected as the shell, with the thickness of the lower shell being 3 mm and the thickness of the upper shell being 2 mm; a square blind hole is processed at the center position of the inner surface of the lower shell, with the length of the blind hole being 3 mm, the width being 3 mm, and the depth being 1 mm.

[0143] (7) The Al₂O₃ lower shell, TiO₂ core, and Al₂O₃ upper shell obtained in steps (5) and (6) are sequentially bonded from bottom to top with 502 glue to obtain a microwave dielectric ceramic with a core-shell structure; the structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 0.24 wt%.

[0144] (8) Testing of the microwave dielectric properties of the ceramic: The microwave dielectric properties of the ceramic obtained in step (7) are tested using a network analyzer and a supporting fixture.

[0145] Example 9

[0146] (1) Pre-sintering of the core CaTiO₃ raw material: CaCO₃ powder and TiO₂ powder are weighed according to the chemical formula, ball-milled for 4 h at a ball-milling speed of 300 r / min, the powder is dried and sieved through a 80-mesh sieve, and then the mixed powder is pre-sintered at 1100 °C for 4 h, followed by ball-milling for 4 h at a ball-milling speed of 300 r / min, the powder is dried and sieved through a 80-mesh sieve to obtain the pre-sintered powder.

[0147] (2) Preparation of the core CaTiO₃ ceramic particles: The pre-sintered powder obtained in step (1) is added to a 5 wt% PVA aqueous solution, and after grinding, granulation, and sieving through an 80-mesh sieve, CaTiO₃ ceramic particles are obtained.

[0148] (3) Preparation of the core CaTiO₃ ceramic green body: The ceramic particles obtained in step (2) are added to a mold and pressed to obtain a ceramic green body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0149] (4)Sintering of the core CaTiO3 ceramic: The green ceramic body prepared in step (3) is first kept at 600 °C for 4 h to remove the binder, and then sintered at 1300 °C for 4 h to obtain a well-sintered CaTiO3 ceramic.

[0150] (5)Processing of the core CaTiO3 ceramic: The ceramic prepared in step (4) is processed into small blocks with a length of 1.25 mm × width of 1.25 mm × height of 1 mm by wire cutting or other means.

[0151] (6)Processing of the shell Al2O3 ceramic: Single crystal (sapphire) Al2O3 ceramic is selected as the shell, with the thickness of the lower shell being 3 mm and the thickness of the upper shell being 2 mm; a square blind hole is processed at the center position of the inner surface of the lower shell, with the length of the blind hole being 3 mm, the width being 3 mm, and the depth being 1 mm.

[0152] (7)The Al2O3 lower shell, TiO2 core, and Al2O3 upper shell prepared in step (5) and step (6) are sequentially bonded in the order from bottom to top with 502 glue to obtain a microwave dielectric ceramic with a core-shell structure; the structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 0.40 wt%.

[0153] (8)Testing of the microwave dielectric properties of the ceramic: The microwave dielectric properties of the ceramic prepared in step (7) are tested using a network analyzer and a matching fixture.

[0154] Example 10

[0155] (1)Pre-sintering of the core CaTiO3 raw materials: CaCO3 powder and TiO2 powder are weighed according to the chemical formula, ball-milled for 4 h at a ball-milling speed of 300 r / min, the powder is dried and passed through an 80-mesh sieve, and then the mixed powder is pre-sintered at 1100 °C for 4 h, followed by ball-milling for 4 h at a ball-milling speed of 300 r / min, and the powder is dried and passed through an 80-mesh sieve to obtain the pre-sintered powder.

[0156] (2)Preparation of the core CaTiO3 ceramic particles: The pre-sintered powder prepared in step (1) is added to a 5 wt% PVA aqueous solution, and after grinding, granulating, and passing through an 80-mesh sieve, CaTiO3 ceramic particles are obtained.

[0157] (3)Preparation of the core CaTiO3 ceramic green body: The ceramic particles prepared in step (2) are added to a mold and pressed to obtain a ceramic green body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0158] (4)Sintering of the core CaTiO3 ceramic: The ceramic green body prepared in step (3) is first kept at 600 °C for 4 h to remove the binder, and then sintered at 1300 °C for 4 h to obtain a well-sintered CaTiO3 ceramic.

[0159] (5)Processing of the core CaTiO3 ceramic: The ceramic obtained in step (4) is processed into small blocks with a length of 1.5 mm × a width of 1.5 mm × a height of 1 mm by wire cutting or other means.

[0160] (6)Processing of the shell Al2O3 ceramic: Single crystal (sapphire) Al2O3 ceramic is selected as the shell, where the thickness of the lower shell is 3 mm and the thickness of the upper shell is 2 mm; a square blind hole is processed at the center position of the inner surface of the lower shell, and the length of the blind hole is 3 mm, the width is 3 mm, and the depth is 1 mm.

[0161] (7)The Al2O3 lower shell, TiO2 core, and Al2O3 upper shell obtained in step (5) and step (6) are sequentially bonded with 502 glue in the order from bottom to top to obtain a microwave dielectric ceramic with a core-shell structure; the structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 0.56 wt%.

[0162] (8)Testing of the microwave dielectric properties of the ceramic: The microwave dielectric properties of the ceramic obtained in step (7) are tested using a network analyzer and a matching fixture.

[0163] The microwave dielectric properties of the dielectric ceramics prepared in Examples 8 to 10 are shown in Table 3:

[0164] Table 3

[0165]

[0166] Comparative Example 3

[0167] (1)Processing of the shell Al2O3 ceramic: Single crystal (sapphire) Al2O3 ceramic is selected as the shell, where the thickness of the lower shell is 3 mm and the thickness of the upper shell is 2 mm; a circular blind hole is processed at the center position of the inner surface of the lower shell, and the diameter of the blind hole is 3 mm and the depth is 1 mm.

[0168] (2)The upper shell and the lower shell are bonded with 502 glue to obtain a microwave dielectric ceramic with a central hole.

[0169] (3)Testing of the microwave dielectric properties of the ceramic: The microwave dielectric properties of the ceramic obtained in step (2) are tested using a network analyzer and a matching fixture.

[0170] Example 11

[0171] (1)Pre-sintering of the core SrTiO3 raw material: Weigh SrCO3 powder and TiO2 powder according to the chemical formula, ball-mill for 4 h at a ball-mill rotation speed of 300 r / min. After drying the powder, sieve it through a 80-mesh sieve. Then pre-sinter the mixed powder at 1100 °C for 4 h, ball-mill for 4 h at a ball-mill rotation speed of 300 r / min again. After drying the powder, sieve it through a 80-mesh sieve to obtain the pre-sintered powder.

[0172] (2)Preparation of the core SrTiO3 ceramic particles: Add the pre-sintered powder obtained in step (1) to a 5 wt% PVA aqueous solution. After grinding, granulating and sieving through a 80-mesh sieve, SrTiO3 ceramic particles are obtained.

[0173] (3)Preparation of the green body of the core SrTiO3 ceramic: Press the ceramic particles obtained in step (2) into a mold to obtain a ceramic green body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0174] (4)Sintering of the core SrTiO3 ceramic: First, keep the ceramic green body obtained in step (3) at 600 °C for 4 h to remove the binder, and then sinter it at 1300 °C for 4 h to obtain a well-sintered SrTiO3 ceramic.

[0175] (5)Processing of the core SrTiO3 ceramic: Process the ceramic obtained in step (4) into small blocks with a length of 0.85 mm × width of 0.85 mm × height of 0.95 mm by wire cutting or other methods.

[0176] (6)Processing of the shell Al2O3 ceramic: Select single-crystal (sapphire) Al2O3 ceramic as the shell, with the thickness of the lower shell being 3 mm and the thickness of the upper shell being 2 mm; Process a circular blind hole at the center position of the inner surface of the lower shell, with the diameter of the blind hole being 3 mm and the depth being 1 mm.

[0177] (7)Bond the Al2O3 lower shell, TiO2 core and Al2O3 upper shell obtained in step (5) and step (6) in sequence from bottom to top with 502 glue to obtain a microwave dielectric ceramic with a core-shell structure; The structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 0.21 wt%.

[0178] (8)Testing of the microwave dielectric properties of the ceramic: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic obtained in step (7).

[0179] Example 12

[0180] (1)Pre-sintering of the core SrTiO3 raw material: Weigh SrCO3 powder and TiO2 powder according to the chemical formula, ball mill them for 4 h at a ball mill rotation speed of 300 r / min. After drying the powder, sieve it through a 80-mesh sieve. Then pre-sinter the mixed powder at 1100 °C for 4 h, followed by ball milling for 4 h at a ball mill rotation speed of 300 r / min. After drying the powder, sieve it through a 80-mesh sieve to obtain the pre-sintered powder.

[0181] (2)Preparation of the core SrTiO3 ceramic particles: Add the pre-sintered powder obtained in step (1) to a 5 wt% PVA aqueous solution. After grinding, granulating, and sieving through a 80-mesh sieve, SrTiO3 ceramic particles are obtained.

[0182] (3)Preparation of the core SrTiO3 ceramic green body: Press the ceramic particles obtained in step (2) into a mold to obtain a ceramic green body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0183] (4)Sintering of the core SrTiO3 ceramic: First, keep the ceramic green body obtained in step (3) at 600 °C for 4 h to remove the binder, and then sinter it at 1300 °C for 4 h to obtain a well-sintered SrTiO3 ceramic.

[0184] (5)Processing of the core SrTiO3 ceramic: Process the ceramic obtained in step (4) into small blocks with a length of 0.93 mm × width of 0.93 mm × height of 0.95 mm by wire cutting or other methods.

[0185] (6)Processing of the shell Al2O3 ceramic: Select single crystal (sapphire) Al2O3 ceramic as the shell, with the thickness of the lower shell being 3 mm and the thickness of the upper shell being 2 mm. Machine a circular blind hole at the center position of the inner surface of the lower shell, with the diameter of the blind hole being 3 mm and the depth being 1 mm.

[0186] (7)Bond the Al2O3 lower shell, TiO2 core, and Al2O3 upper shell obtained in steps (5) and (6) in sequence from bottom to top with 502 glue to prepare a microwave dielectric ceramic with a core-shell structure; the structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 0.26 wt%.

[0187] (8)Testing of the microwave dielectric properties of the ceramic: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic prepared in step (7).

[0188] Example 13

[0189] (1)Pre-sintering of the core SrTiO3 raw material: Weigh SrCO3 powder and TiO2 powder according to the chemical formula, ball mill them for 4 h at a ball mill rotation speed of 300 r / min. After drying the powder, sieve it through a 80-mesh sieve. Then pre-sinter the mixed powder at 1100 °C for 4 h, followed by ball milling for 4 h at a ball mill rotation speed of 300 r / min. After drying the powder, sieve it through a 80-mesh sieve to obtain the pre-sintered powder.

[0190] (2)Preparation of the core SrTiO3 ceramic particles: Add the pre-sintered powder obtained in step (1) to a 5 wt% PVA aqueous solution. After grinding, granulating, and sieving through a 80-mesh sieve, SrTiO3 ceramic particles are obtained.

[0191] (3)Preparation of the core SrTiO3 green body: Press the ceramic particles obtained in step (2) into a mold to obtain a ceramic green body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0192] (4)Sintering of the core SrTiO3 ceramic: First, keep the ceramic green body obtained in step (3) at 600 °C for 4 h to remove the binder, and then sinter it at 1300 °C for 4 h to obtain a well-sintered SrTiO3 ceramic.

[0193] (5)Processing of the core SrTiO3 ceramic: Process the ceramic obtained in step (4) into small blocks with a length of 1 mm × width of 1 mm × height of 0.95 mm by wire cutting or other means.

[0194] (6)Processing of the shell Al2O3 ceramic: Select single-crystal (sapphire) Al2O3 ceramic as the shell, with the thickness of the lower shell being 3 mm and the thickness of the upper shell being 2 mm; Machine a circular blind hole at the center of the inner surface of the lower shell, with the diameter of the blind hole being 3 mm and the depth being 1 mm.

[0195] (7)Bond the Al2O3 lower shell, TiO2 core, and Al2O3 upper shell obtained in steps (5) and (6) in sequence from bottom to top using 502 glue to prepare a microwave dielectric ceramic with a core-shell structure; The structure of the microwave dielectric ceramic is as Figure 2 shown, and the mass percentage of the core is 0.31 wt%.

[0196] (8)Testing of the microwave dielectric properties of the ceramic: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic obtained in step (7).

[0197] The microwave dielectric properties of the dielectric ceramics prepared in Comparative Example 3 and Examples 11 - 13 are shown in Table 4:

[0198] Table 4

[0199]

[0200] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A microwave dielectric ceramic material with a core-shell structure, characterized in that, Including: A shell and a core. The shell is formed by gluing an upper shell and a lower shell. The core is adhesively fixed in the cavity of the shell. The materials of the upper shell and the lower shell are Al2O3, and the materials of the core are TiO2, CaTiO3 or SrTiO3; the core accounts for 0.1~3wt% of the total mass of the microwave dielectric ceramic material.

2. The microwave dielectric ceramic material according to claim 1, wherein The core accounts for 0.2~1.6wt% of the total mass of the microwave dielectric ceramic material.

3. A preparation method of a microwave dielectric ceramic material with a core-shell structure, characterized in that, Including the following steps: Placing the core in the cavity formed by the upper shell and the lower shell, and using glue to adhesively fix the upper shell, the core and the lower shell to obtain a microwave dielectric ceramic material with a core-shell structure; The materials of the upper shell and the lower shell are Al2O3, and the materials of the core are TiO2, CaTiO3 or SrTiO3; the core accounts for 0.1~3wt% of the total mass of the microwave dielectric ceramic material.

4. The preparation method according to claim 3, characterized in that, The preparation steps of the core include: a) Weighing the corresponding raw materials according to the chemical formula of the core material to be prepared, and obtaining pre-sintered powder after pre-sintering, ball milling, drying and sieving; b) Mixing and grinding the pre-sintered powder with an aqueous binder solution, granulating, and sieving to obtain powder particles; c) Adding the powder particles into a mold for pressing to obtain a green ceramic body; d) Sintering the green ceramic body to obtain the core.

5. The preparation method according to claim 4, characterized in that, In step a), if the core material to be prepared is TiO2, the raw material is TiO2 powder, the temperature of the pre-sintering is 950~1075°C, and the time of the pre-sintering is 2~6h; If the core material to be prepared is CaTiO3, the raw materials are CaCO3 powder and TiO2 powder, the temperature of the pre-sintering is 1050~1200°C, and the time of the pre-sintering is 2~6h; If the core material to be prepared is SrTiO3, the raw materials are SrCO3 powder and TiO2 powder, the temperature of the pre-sintering is 1050~1200°C, and the time of the pre-sintering is 2~6h.

6. The preparation method according to claim 4, wherein In step a), the rotation speed of the ball milling is 200~400r / min, and the time is 3~6h; the mesh number of the sieving is 60~120 meshes.

7. The preparation method according to claim 4, wherein In step b), the aqueous binder solution is an aqueous PVA solution; the concentration of the aqueous binder solution is 3~6wt%; the mesh number of the sieving is 60~120 meshes.

8. The preparation method according to claim 4, characterized in that, In step d), before sintering the green ceramic body, it is first kept warm at 550~600°C for 2~6h to remove the binder.

9. The preparation method according to claim 4, characterized in that, In step d), if the core material to be prepared is TiO2, the temperature of the sintering is 1150~1350°C, and the time of the sintering is 2~6h; If the core material to be prepared is CaTiO3, the temperature of the sintering is 1200~1400°C, and the time of the sintering is 2~6h; If the core material to be prepared is SrTiO3, the temperature of the sintering is 1200~1400°C, and the time of the sintering is 2~6h.

10. The preparation method according to claim 3, characterized in that, The glue is 502 glue.

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