Microwave dielectric ceramic material with core-shell structure and preparation method thereof

Abstract

The 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 of the microwave dielectric ceramic material. The microwave dielectric ceramic material provided by the invention comprises a shell and an inner core, the shell is formed by bonding an upper shell and a lower shell, the inner core is bonded and fixed in a cavity of the shell, the upper shell and the lower shell are made of Al2O3, and the inner core is made of TiO2, CaTiO3 or SrTiO3; and the inner core accounts for 0.1-3wt% of the total mass of the microwave dielectric ceramic material. Based on macroscopic core-shell structure design and construction, Al2O3 is used as a shell of the microwave dielectric ceramic material, TiO2, CaTiO3 or SrTiO3 is selected as an inner core of the microwave dielectric ceramic material, and the microwave dielectric ceramic material with low dielectric constant, low dielectric loss and good temperature stability can be finally obtained by adjusting the mass percent of the inner core.

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 has expanded from the low-frequency band of microwaves to the millimeter-wave range of the high-frequency band, prompting the electronic components that make up the communication system to develop in the directions of high frequency, miniaturization, integration, and low power consumption. The size of the dielectric resonator is negatively correlated with the square root of the material's 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's 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 the 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 generate 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, and 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 bonded and fixed in the chamber of the outer shell. The materials of the upper shell and the lower shell are Al 2 O 3 , and the material of the inner core is TiO 2 , CaTiO 3 or SrTiO 3 ; the inner core accounts for 0.1-3 wt% of the total mass of the microwave dielectric ceramic material.

[0006] Preferably, the inner core accounts for 0.2-1.6 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: Place the inner core in the chamber formed by the upper shell and the lower shell, and use glue to bond and fix the upper shell, the inner 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 Al 2 O 3 , and the material of the inner core is TiO 2 , CaTiO 3 or SrTiO 3 ; the inner core accounts for 0.1-3 wt% of the total mass of the microwave dielectric ceramic material.

[0008] Preferably, the preparation steps of the inner core include: a) Weigh the 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; b) Mix and grind the pre-sintered powder with an aqueous binder solution, granulate and sieve to obtain powder particles; c) Add the powder particles into a mold for pressing to obtain a ceramic green body; d) Sinter the ceramic green body to obtain the inner core.

[0009] Preferably, in step a), if the inner core material to be prepared is TiO 2 , the raw material is TiO 2 powder, the pre-sintering temperature is 950-1075 °C, and the pre-sintering time is 2-6 h; If the inner core material to be prepared is CaTiO 3 , the raw materials are CaCO 3 powder and TiO 2 powder, the pre-sintering temperature is 1050-1200 °C, and the pre-sintering time is 2-6 h; If the core material to be prepared is SrTiO 3 , then the raw materials are SrCO 3 powder and TiO 2 powder, the temperature of the pre-sintering is 1050 - 1200 °C, and the time of the pre-sintering is 2 - 6 h.

[0010] 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 meshes.

[0011] 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 meshes.

[0012] 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.

[0013] Preferably, in step d), if the core material to be prepared is TiO 2 , then the sintering temperature is 1150 - 1350 °C, and the sintering time is 2 - 6 h; if the core material to be prepared is CaTiO 3 , then the sintering temperature is 1200 - 1400 °C, and the sintering time is 2 - 6 h; if the core material to be prepared is SrTiO 3 , then the sintering temperature is 1200 - 1400 °C, and the sintering time is 2 - 6 h.

[0014] Preferably, the glue is 502 glue.

[0015] 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 composed of an upper shell and a lower shell which are adhesively joined. The core is adhesively fixed in the cavity of the outer shell. The materials of the upper shell and the lower shell are Al 2 O 3 , and the material of the core is TiO 2 , CaTiO 3 or SrTiO 3 ; 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, the present invention uses Al 2 O 3 as the outer shell of the microwave dielectric ceramic material, and selects TiO 2 , CaTiO3 or SrTiO 3 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 adjusting τ f by multi-phase hybrid sintering, 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, and can achieve near-zero τ f adjustment under the condition that the mass percentage of the core is a small value, which 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

[0016] 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.

[0017] Figure 1 is a schematic structural diagram of a microwave dielectric ceramic material with the same upper and lower shell dimensions provided by an embodiment of the present invention; Figure 2 Schematic structural diagram of a microwave dielectric ceramic material with different upper and lower shell dimensions provided by an embodiment of the present invention.

[0018] Explanation of the reference numerals in the drawings: 1 is the upper shell, 2 is the lower shell, 3 is the blind hole, and 4 is the core. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] 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 of 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.

[0020] The present invention provides a microwave dielectric ceramic material with a core-shell structure, including: an outer shell and a core. The outer shell is composed of an upper shell and a lower shell bonded together. The core is bonded and fixed in the cavity of the outer shell. The materials of the upper shell and the lower shell are Al 2 O 3 , and the material of the core is TiO 2 , CaTiO 3 or SrTiO 3 .

[0021] 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) Al 2 O 3 or polycrystalline Al 2 O 3 .

[0022] In the microwave dielectric ceramic material provided by the present invention, blind holes for accommodating the inner core are provided on the inner sides 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. 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 blind holes are provided only on the inner side of the shell with the larger dimension. The structure of the corresponding microwave dielectric ceramic material is as Figure 2 shown.

[0023] 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 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 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.

[0024] 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 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 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 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.

[0025] 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 can 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%.

[0026] 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.

[0027] 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.

[0028] 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 resonant frequency temperature coefficient τ f is preferably -50.0 ppm / °C to +250.0 ppm / °C.

[0029] The present invention also provides a preparation method of the microwave dielectric ceramic material described in the above technical solution, including the following steps: 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.

[0030] In the preparation method provided by the present invention, the preparation steps of the core preferably include: a) Weigh the corresponding raw materials according to the chemical formula of the core material to be prepared, and obtain the pre-sintered powder after pre-sintering, ball milling, drying and sieving; b) Mix and grind the pre-sintered powder with the binder aqueous solution, granulate, and sieve to obtain powder particles; c) Add the powder particles into a mold for pressing to obtain a green ceramic body; d) Sinter the green ceramic body to obtain the core.

[0031] In the above-mentioned core preparation steps provided by the present invention, in step a), if the core material to be prepared is TiO 2 , the raw material is preferably TiO 2 powder, the temperature of the pre-sintering is preferably 950-1075 °C, specifically 950 °C, 975 °C, 1000 °C, 1025 °C, 1050 °C or 1075 °C, and the time of the pre-sintering 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.

[0032] In the above-mentioned core preparation steps provided by the present invention, in step a), if the core material to be prepared is CaTiO 3 , the raw materials are preferably CaCO 3 powder and TiO 2 powder, the temperature of the pre-sintering is preferably 1050-1200 °C, specifically 1050 °C, 1075 °C, 1100 °C, 1125 °C, 1150 °C, 1175 °C or 1200 °C, and the time of the pre-sintering 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.

[0033] In the above-mentioned core preparation steps provided by the present invention, in step a), if the core material to be prepared is SrTiO 3 , the raw materials are preferably SrCO 3 powder and TiO 2 powder, the temperature of the pre-sintering is preferably 1050-1200 °C, specifically 1050 °C, 1075 °C, 1100 °C, 1125 °C, 1150 °C, 1175 °C or 1200 °C, and the time of the pre-sintering 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.

[0034] 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 absolute 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 time of the ball milling 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.

[0035] In the above-described 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 to 6 wt%, specifically 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 to 120 meshes, specifically 60 meshes, 70 meshes, 80 meshes, 100 meshes or 120 meshes.

[0036] In the above-described 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 to 600 °C for 2 to 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.

[0037] In the above-described core preparation steps provided by the present invention, in step d), if the core material to be prepared is TiO 2 , then the sintering temperature is preferably 1150 to 1350 °C, specifically 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 to 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.

[0038] In the above-described core preparation steps provided by the present invention, in step d), if the core material to be prepared is CaTiO 3 , then the sintering temperature is preferably 1200 to 1400 °C, specifically 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 to 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.

[0039] In the above-described core preparation steps provided by the present invention, in step d), if the core material to be prepared is SrTiO 3 , then the sintering temperature is preferably 1200 to 1400 °C, specifically 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 to 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.

[0040] In the above-mentioned core preparation steps provided by the present invention, it preferably further includes the following steps: processing the prepared core in terms of size by means of wire cutting or the like.

[0041] In the preparation method provided by the present invention, there is no particular limitation 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.

[0042] 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.

[0043] The technical solution provided by the present invention is based on the design and construction of a macroscopic core-shell structure. Using Al 2 O 3 as the outer shell of the microwave dielectric ceramic material, and selecting TiO 2 , CaTiO 3 or SrTiO 3 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 adjusting τ f by multi-phase mixed sintering, 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, the adjustment of nearly zero τ f can be realized, which is conducive to the coordinated regulation of the microwave dielectric properties of the dielectric ceramic and has great application value in communication components such as dielectric resonators.

[0044] For the sake of clarity, the following will be described in detail through the following examples and comparative examples.

[0045] Comparative Example 1 (1) Shell Al 2 O 3 ceramic processing: Select single crystal (sapphire) Al 2 O 3 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, and the length of the blind hole is 3 mm, the width is 3 mm, and the depth is 1 mm.

[0046] (2) Bond the upper shell and the lower shell with 502 glue to obtain a microwave dielectric ceramic with a central hole.

[0047] (3) Microwave dielectric property test of the ceramic: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic prepared in step (2).

[0048] Example 1 (1) Core TiO 2 Raw material pre-sintering: After pre-sintering TiO 2 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 pre-sintered powder.

[0049] (2) Core TiO 2 Ceramic particle preparation: The pre-sintered powder obtained in step (1) was added with 5 wt% PVA aqueous solution. After grinding, granulating, and sieving through an 80-mesh sieve, TiO 2 ceramic particles were obtained.

[0050] (3) Core TiO 2 Green ceramic body preparation: The ceramic particles obtained in step (2) were added to a mold and pressed to obtain a green ceramic body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0051] (4) Core TiO 2 Ceramic sintering: The green ceramic 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 well-sintered TiO 2 ceramics.

[0052] (5) Core TiO 2 Ceramic processing: The ceramics obtained in step (4) were 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 means.

[0053] (6) Shell Al 2 O 3 Ceramic processing: Single crystal (sapphire) Al 2 O 3 ceramics were selected as the shell, where the thickness of the lower shell was 3 mm and the thickness of the upper shell was 2 mm; a square blind hole was machined 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.

[0054] (7) The Al 2 O 3 lower shell, TiO 2 core, and Al 2 O 3 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 0.60 wt%.

[0055] (8)Testing of ceramic microwave dielectric properties: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic prepared in step (7).

[0056] Example 2 (1)Core TiO 2 Pre-sintering of raw materials: After pre-sintering the TiO 2 powder at 1050 °C for 4 h, ball-mill it 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.

[0057] (2)Core TiO 2 Preparation of ceramic particles: Add the pre-sintered powder prepared in step (1) to a 5 wt% PVA aqueous solution. After grinding, granulating, and sieving through an 80-mesh sieve, obtain the TiO 2 ceramic particles.

[0058] (3)Core TiO 2 Preparation of green ceramic bodies: Press the ceramic particles prepared in step (2) into a mold to obtain green ceramic bodies with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0059] (4)Core TiO 2 Ceramic sintering: First, keep the green ceramic bodies prepared in step (3) at 600 °C for 4 h to remove the binder, and then sinter them at 1250 °C for 4 h to obtain well-sintered TiO 2 ceramics.

[0060] (5)Core TiO 2 Ceramic processing: Process the ceramics prepared 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 means.

[0061] (6)Shell Al 2 O 3 Ceramic processing: Select single-crystal (sapphire) Al 2 O 3 ceramics 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.

[0062] (7)Arrange the Al 2 O 3 lower shell, TiO 2 core, and Al 2 O 3 upper shell prepared in step (5) and step (6) in sequence from bottom to top, and bond them with 502 glue to obtain a microwave dielectric ceramic with a core-shell structure; The structure of the microwave dielectric ceramic is as shown in Figure 2As shown, the core mass percentage is 0.76 wt%.

[0063] (8)Testing of ceramic microwave dielectric properties: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic prepared in step (7).

[0064] Example 3 (1)Core TiO 2 Raw material pre-sintering: Pre-sinter the TiO 2 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 the pre-sintered powder.

[0065] (2)Core TiO 2 Ceramic particle preparation: Add the pre-sintered powder prepared in step (1) to a 5 wt% PVA aqueous solution. After grinding, granulating, and passing through an 80-mesh sieve, obtain the TiO 2 ceramic particles.

[0066] (3)Core TiO 2 Green ceramic body preparation: Press the ceramic particles prepared in step (2) into a mold to obtain a green ceramic body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0067] (4)Core TiO 2 Ceramic sintering: First, keep the green ceramic body prepared in step (3) at 600 °C for 4 h to remove the binder, and then sinter it at 1250 °C for 4 h to obtain a well-sintered TiO 2 ceramic.

[0068] (5)Core TiO 2 Ceramic processing: Process the ceramic prepared in step (4) into small blocks with a length of 2 mm × width of 2 mm × height of 1 mm by wire cutting or other methods.

[0069] (6)Shell Al 2 O 3 Ceramic processing: Select single crystal (sapphire) Al 2 O 3 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.

[0070] (7)Combine the Al 2 O 3 lower shell, TiO 2 core, and Al 2 O 3The upper shell is 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 shown in Figure 2 shown, and the mass percentage of the inner core is 1.03 wt%.

[0071] (8) Testing of microwave dielectric properties of ceramics: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramics prepared in step (7).

[0072] Example 4 (1) Pre-sintering of the inner core TiO 2 Raw material pre-sintering: The TiO 2 powder is 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 is dried, it is sieved through an 80-mesh sieve to obtain the pre-sintered powder.

[0073] (2) Preparation of inner core TiO 2 ceramic particles: Add the pre-sintered powder prepared in step (1) to a 5 wt% PVA aqueous solution. After grinding, granulating, and sieving through an 80-mesh sieve, TiO 2 ceramic particles are obtained.

[0074] (3) Preparation of inner core TiO 2 green ceramic body: Press the ceramic particles prepared in step (2) into a mold to obtain a green ceramic body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0075] (4) Sintering of inner core TiO 2 ceramics: First, keep the green ceramic body prepared in step (3) at 600 °C for 4 h to remove the binder, and then sinter it at 1250 °C for 4 h to obtain well-sintered TiO 2 ceramics.

[0076] (5) Processing of inner core TiO 2 ceramics: Process the ceramics prepared in step (4) into small blocks with a length of 2.5 mm × width of 2.5 mm × height of 1 mm by wire cutting or other methods.

[0077] (6) Processing of the shell Al 2 O 3 ceramics: Select single-crystal (sapphire) Al 2 O 3 ceramics 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.

[0078] (7) Combine the Al 2 O 3 lower shell and TiO2 Core, Al 2 O 3 The upper shell is 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 1.51 wt%.

[0079] (8) Testing of microwave dielectric properties of ceramics: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramics prepared in step (7).

[0080] The microwave dielectric properties of the dielectric ceramics prepared in Comparative Example 1 and Examples 1 - 4 are shown in Table 1: Table 1

[0081] Comparative Example 2 (1) Shell Al 2 O 3 Ceramic processing: Select Al 2 O 3 polycrystalline 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 machined 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.

[0082] (2) Bond the upper shell and the lower shell with 502 glue to obtain a microwave dielectric ceramic with a central hole.

[0083] (3) Testing of microwave dielectric properties of ceramics: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramics prepared in step (2).

[0084] Example 5 (1) Core TiO 2 Raw material pre - sintering: Pre - sinter the TiO 2 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 the pre - sintered powder.

[0085] (2) Core TiO 2 Ceramic particle preparation: 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, obtain TiO 2 ceramic particles.

[0086] (3) Core TiO 2 Green body preparation of ceramics: Press the ceramic particles prepared 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.

[0087] (4)Core TiO 2 Ceramic sintering: 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 TiO 2 ceramic.

[0088] (5)Core TiO 2 Ceramic processing: The ceramic prepared in step (4) is processed into small blocks with a length of 1.5 mm × a width of 1.5 mm × a height of 0.75 mm by wire cutting or other means.

[0089] (6)Shell Al 2 O 3 Ceramic processing: Select Al 2 O 3 polycrystalline 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 machined 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.

[0090] (7)The Al 2 O 3 lower shell, TiO 2 core, Al 2 O 3 upper shell 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 0.49 wt%.

[0091] (8)Ceramic microwave dielectric property test: Use a network analyzer and a matching fixture to test the microwave dielectric properties of the ceramic prepared in step (7).

[0092] Example 6 (1)Core TiO 2 Raw material pre-sintering: The TiO 2 powder is 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 is dried, it is sieved through an 80-mesh sieve to obtain the pre-sintered powder.

[0093] (2)Core TiO 2 Ceramic particle preparation: Add the pre-sintered powder prepared in step (1) to a 5 wt% PVA aqueous solution, and after grinding, granulating, and sieving through an 80-mesh sieve, obtain TiO 2 ceramic particles.

[0094] (3)Core TiO 2Preparation of green ceramic body: The ceramic particles obtained in step (2) are added to a mold and pressed to obtain a green ceramic body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0095] (4)Inner core TiO 2 Ceramic sintering: 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 1250 °C for 4 h to obtain a well-sintered TiO 2 ceramic.

[0096] (5)Inner core TiO 2 Ceramic processing: The ceramic obtained in step (4) is 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.

[0097] (6)Shell Al 2 O 3 Ceramic processing: Select polycrystalline Al 2 O 3 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, and the length of the blind hole is 3 mm, the width is 3 mm, and the depth is 1 mm.

[0098] (7)The Al 2 O 3 lower shell, TiO 2 inner core, Al 2 O 3 upper shell 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 inner core is 0.75 wt%. (8) Microwave dielectric property test of ceramic: Use a network analyzer and a matching fixture to test the microwave dielectric properties of the ceramic obtained in step (7).

[0099] Example 7 (1)Inner core TiO 2 Pre-sintering of raw materials: The TiO 2 powder is 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 is dried, it is passed through an 80-mesh sieve to obtain pre-sintered powder.

[0100] (2)Inner core TiO 2 Preparation of ceramic particles: The pre-sintered powder obtained in step (1) is added to a 5 wt% PVA aqueous solution, and after grinding, granulation, and passing through an 80-mesh sieve, TiO 2 ceramic particles are obtained.

[0101] (3) Core TiO 2 Preparation of green ceramic body: The ceramic particles obtained in step (2) are added to a mold and pressed to obtain a green ceramic body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0102] (4) Core TiO 2 Ceramic sintering: 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 1250 °C for 4 h to obtain a well - sintered TiO 2 ceramic.

[0103] (5) Core TiO 2 Ceramic processing: The ceramic obtained 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.

[0104] (6) Shell Al 2 O 3 Ceramic processing: Select polycrystalline Al 2 O 3 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 machined at the center 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.

[0105] (7) The Al 2 O 3 lower shell, TiO 2 core, Al 2 O 3 upper shell 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 1.03 wt%. (8) Microwave dielectric property testing of ceramics: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic obtained in step (7).

[0106] The microwave dielectric properties of the dielectric ceramics prepared in Comparative Example 2 and Examples 5 - 7 are shown in Table 2: Table 2

[0107] Example 8 (1) Core CaTiO 3 Raw material pre - sintering: Weigh CaCO 3 powder and TiO 2The powder is ball-milled for 4 h at a rotation speed of 300 r / min. After the powder is dried, it is sieved through a 80-mesh sieve. Then, the mixed powder is pre-sintered at 1100 °C for 4 h, followed by ball-milling for 4 h at a rotation speed of 300 r / min. After the powder is dried, it is sieved through a 80-mesh sieve to obtain the pre-sintered powder.

[0108] (2) Preparation of core CaTiO 3 Preparation of ceramic particles: The pre-sintered powder obtained in step (1) is added with a 5 wt% aqueous PVA solution. After grinding, granulating, and sieving through a 80-mesh sieve, CaTiO 3 ceramic particles are obtained.

[0109] (3) Preparation of green body of core CaTiO 3 Preparation of 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.

[0110] (4) Sintering of core CaTiO 3 Ceramic sintering: The ceramic green 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 well-sintered CaTiO 3 ceramics.

[0111] (5) Machining of core CaTiO 3 Ceramic machining: The ceramics obtained in step (4) are machined into small blocks with a length of 1 mm × width of 1 mm × height of 1 mm by wire cutting or other means.

[0112] (6) Machining of shell Al 2 O 3 Ceramic machining: Single crystal (sapphire) Al 2 O 3 ceramics are 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 with a length of 3 mm, a width of 3 mm, and a depth of 1 mm is machined at the center position of the inner surface of the lower shell.

[0113] (7) The Al 2 O 3 lower shell, TiO 2 core, and Al 2 O 3 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%.

[0114] (8) Testing of ceramic microwave dielectric properties: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic prepared in step (7).

[0115] Example 9 (1) Core CaTiO 3 Pre-sintering of raw materials: Weigh CaCO 3 powder and TiO 2 powder. After 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. 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. After drying the powder and sieving it through a 80-mesh sieve, the pre-sintered powder is obtained.

[0116] (2) Preparation of core CaTiO 3 ceramic particles: Add the pre-sintered powder prepared in step (1) to a 5 wt% PVA aqueous solution. After grinding, granulating, and sieving through a 80-mesh sieve, CaTiO 3 ceramic particles are obtained.

[0117] (3) Preparation of core CaTiO 3 green ceramic body: Press the ceramic particles prepared in step (2) into a mold to obtain a green ceramic body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0118] (4) Sintering of core CaTiO 3 ceramic: First, keep the green ceramic body prepared 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 CaTiO 3 ceramic.

[0119] (5) Processing of core CaTiO 3 ceramic: Process the ceramic prepared in step (4) 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.

[0120] (6) Processing of shell Al 2 O 3 ceramic: Select single crystal (sapphire) Al 2 O 3 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.

[0121] (7) Combine the Al 2 O 3 lower shell, TiO 2 core, Al 2 O3 The upper shell is 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 shown in Figure 2 and the mass percentage of the inner core is 0.40 wt%.

[0122] (8)Testing of microwave dielectric properties of ceramics: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramics prepared in step (7).

[0123] Example 10 (1)Inner core CaTiO 3 Pre-sintering of raw materials: Weigh CaCO 3 powder and TiO 2 powder according to the chemical formula. After 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. 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. After the powder is dried and sieved through a 80-mesh sieve, pre-sintered powder is obtained.

[0124] (2)Preparation of inner core CaTiO 3 ceramic particles: Add the pre-sintered powder prepared in step (1) to a 5 wt% aqueous PVA solution. After grinding, granulating and sieving through a 80-mesh sieve, CaTiO 3 ceramic particles are obtained.

[0125] (3)Preparation of inner core CaTiO 3 green body: Add the ceramic particles prepared in step (2) to a mold and press to obtain a ceramic green body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0126] (4)Sintering of inner core CaTiO 3 ceramics: First, keep the ceramic green body prepared 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 well-sintered CaTiO 3 ceramics.

[0127] (5)Processing of inner core CaTiO 3 ceramics: Process the ceramics prepared in step (4) into small blocks with a length of 1.5 mm × width of 1.5 mm × height of 1 mm by wire cutting or other means.

[0128] (6)Processing of shell Al 2 O 3 ceramics: Select single crystal (sapphire) Al 2 O 3The ceramic is used as the housing, where the thickness of the lower housing is 3 mm and the thickness of the upper housing is 2 mm; a square blind hole is machined at the center position of the inner surface of the lower housing, and the length of the blind hole is 3 mm, the width is 3 mm, and the depth is 1 mm.

[0129] (7) Combine the Al prepared in steps (5) and (6) 2 O 3 the lower housing, TiO 2 the inner core, Al 2 O 3 the upper housing 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 inner core is 0.56 wt%.

[0130] (8) Microwave dielectric property test of the ceramic: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic prepared in step (7).

[0131] The microwave dielectric properties of the dielectric ceramics prepared in Examples 8 to 10 are shown in Table 3: Table 3

[0132] Comparative Example 3 (1) Housing Al 2 O 3 Ceramic processing: Select single crystal (sapphire) Al 2 O 3 ceramic as the housing, where the thickness of the lower housing is 3 mm and the thickness of the upper housing is 2 mm; a circular blind hole is machined at the center position of the inner surface of the lower housing, and the diameter of the blind hole is 3 mm and the depth is 1 mm.

[0133] (2) Bond the upper housing and the lower housing with 502 glue to obtain a microwave dielectric ceramic with a central hole.

[0134] (3) Microwave dielectric property test of the ceramic: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic prepared in step (2).

[0135] Example 11 (1) Inner core SrTiO 3 Raw material pre-sintering: Weigh SrCO 3 powder and TiO 2 powder according to the chemical formula, ball mill for 4 h at a ball mill speed of 300 r / min, dry the powder and pass it through an 80-mesh sieve, then pre-sinter the mixed powder at 1100 °C for 4 h, then ball mill for 4 h at a ball mill speed of 300 r / min, dry the powder and pass it through an 80-mesh sieve to obtain the pre-sintered powder.

[0136] (2) Core SrTiO 3 Preparation of ceramic particles: The pre-sintered powder obtained in step (1) was added to a 5wt% aqueous PVA solution, ground, granulated, and passed through an 80-mesh sieve to obtain SrTiO 3 ceramic particles.

[0137] (3) Core SrTiO 3 Preparation of green ceramic body: The ceramic particles obtained in step (2) were added to a mold and pressed to obtain a green ceramic body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0138] (4) Core SrTiO 3 Ceramic sintering: The green ceramic body obtained in step (3) was first held at 600 °C for 4 h to remove the binder, and then sintered at 1300 °C for 4 h to obtain a well-sintered SrTiO 3 ceramic.

[0139] (5) Core SrTiO 3 Ceramic processing: The ceramic obtained in step (4) was processed 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 means.

[0140] (6) Shell Al 2 O 3 Ceramic processing: Single crystal (sapphire) Al 2 O 3 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 circular blind hole with a diameter of 3 mm and a depth of 1 mm was machined at the center position of the inner surface of the lower shell.

[0141] (7) The Al 2 O 3 lower shell, TiO 2 core, Al 2 O 3 upper shell were 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 0.21 wt%.

[0142] (8) Testing of microwave dielectric properties of ceramics: The microwave dielectric properties of the ceramic obtained in step (7) were tested using a network analyzer and a matching fixture.

[0143] Example 12 (1) Core SrTiO 3 Pre-sintering of raw materials: SrCO 3 powder and TiO 2The powder is ball-milled for 4 h at a ball-milling speed of 300 r / min. After the powder is dried, it is sieved through a 80-mesh sieve. 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. After the powder is dried, it is sieved through a 80-mesh sieve to obtain the pre-sintered powder.

[0144] (2)Inner core SrTiO 3 Preparation of ceramic particles: The pre-sintered powder obtained in step (1) is added with 5 wt% PVA aqueous solution. After grinding, granulating, and sieving through a 80-mesh sieve, SrTiO 3 ceramic particles are obtained.

[0145] (3)Inner core SrTiO 3 Preparation of green body of ceramic: The ceramic particles obtained in step (2) are 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.

[0146] (4)Inner core SrTiO 3 Sintering of ceramic: The green body of ceramic 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 SrTiO 3 ceramic.

[0147] (5)Inner core SrTiO 3 Processing of ceramic: The ceramic obtained in step (4) is processed 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 means.

[0148] (6)Shell Al 2 O 3 Processing of ceramic: Single crystal (sapphire) Al 2 O 3 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 with a diameter of 3 mm and a depth of 1 mm is processed at the center position of the inner surface of the lower shell.

[0149] (7)The Al 2 O 3 lower shell, TiO 2 inner core, Al 2 O 3 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 inner core is 0.26 wt%.

[0150] (8)Testing of ceramic microwave dielectric properties: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramic prepared in step (7).

[0151] Example 13 (1)Core SrTiO 3 Pre-sintering of raw materials: Weigh SrCO 3 powder and TiO 2 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 and passing it through an 80-mesh sieve, pre-sinter the mixed powder at 1100 °C for 4 h, then ball mill for 4 h at a ball mill rotation speed of 300 r / min. After drying the powder and passing it through an 80-mesh sieve, obtain the pre-sintered powder.

[0152] (2)Preparation of core SrTiO 3 ceramic particles: Add the pre-sintered powder prepared in step (1) to a 5 wt% PVA aqueous solution. After grinding, granulating, and passing it through an 80-mesh sieve, obtain SrTiO 3 ceramic particles.

[0153] (3)Preparation of core SrTiO 3 green ceramic body: Press the ceramic particles prepared in step (2) into a mold to obtain a green ceramic body with a diameter of 10 mm and a thickness of 1 - 1.5 mm.

[0154] (4)Sintering of core SrTiO 3 ceramic: First, keep the green ceramic body prepared 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 SrTiO 3 ceramic.

[0155] (5)Processing of core SrTiO 3 ceramic: Process the ceramic prepared 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 methods.

[0156] (6)Processing of shell Al 2 O 3 ceramic: Select single-crystal (sapphire) Al 2 O 3 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 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.

[0157] (7)Combine the Al 2 O 3 lower shell, TiO 2 core, and Al 2 O 3The upper shell is 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 shown in Figure 2 shown, and the mass percentage of the inner core is 0.31 wt%.

[0158] (8) Testing of microwave dielectric properties of ceramics: Use a network analyzer and a supporting fixture to test the microwave dielectric properties of the ceramics prepared in step (7).

[0159] The microwave dielectric properties of the dielectric ceramics prepared in Comparative Example 3 and Examples 11 to 13 are shown in Table 4: Table 4

[0160] 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 refinements can be made, and these improvements and refinements 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: include: The outer shell is composed of an upper shell and a lower shell bonded together, and the inner core is bonded and fixed in the cavity of the outer shell. The material of the upper shell and the lower shell is Al2O3, and the material of the inner core is TiO2, CaTiO3 or SrTiO3; the inner 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, characterized in that: The core accounts for 0.2-1.6 wt % of the total mass of the microwave dielectric ceramic material.

3. A method for preparing a microwave dielectric ceramic material having a core-shell structure, characterized in that: The following steps are involved: Placing the core in a chamber formed by an upper shell and a lower shell, and using 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; The material of the upper shell and the lower shell is Al2O3, and the material of the inner core is TiO2, CaTiO3 or SrTiO3; the inner 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 kernel include: a) Weighing 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 the pre-sintered powder with a binder aqueous solution, grinding, granulating, and sieving to obtain powder particles; c) adding the powder particles into a mold and pressing them to obtain a ceramic green body; d) sintering the ceramic green body to obtain a 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 pre-sintering temperature is 950-1075°C, and the pre-sintering time is 2-6h; If the core material to be prepared is CaTiO3, the raw materials are CaCO3 powder and TiO2 powder, the pre-sintering temperature is 1050-1200°C, and the pre-sintering time is 2-6h; 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 hours.

6. The preparation method according to claim 4, characterized in that: In step a), the rotation speed of the ball mill is 200-400 r / min, and the time is 3-6 hours; the mesh number of the sieving screen is 60-120 meshes.

7. The preparation method according to claim 4, characterized in that: In step b), the binder aqueous solution is a PVA aqueous solution; the concentration of the binder aqueous solution is 3-6 wt %; and the mesh number of the sieve is 60-120 meshes.

8. The preparation method according to claim 4, characterized in that: In step d), the ceramic green body is kept at 550-600° C. for 2-6 hours before sintering 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 sintering temperature is 1150-1350°C, and the sintering time is 2-6 hours; If the core material to be prepared is CaTiO3, the sintering temperature is 1200-1400°C, and the sintering time is 2-6 hours; If the core material to be prepared is SrTiO3, the sintering temperature is 1200-1400°C, and the sintering time is 2-6 hours.

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

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