Microwave dielectric ceramic with low sintering temperature and high mechanical stability for high-frequency microwave device and preparation method of microwave dielectric ceramic

Abstract

The invention belongs to the field of microwave dielectric ceramic materials, and particularly provides a method for improving the performance of zinc aluminate microwave ceramic based on a CTN (CuO-TiO2-Nb2O5) composite sintering aid, so that the prepared zinc aluminate microwave dielectric ceramic material has a low dielectric constant and a high thermal expansion coefficient, and is suitable for manufacturing a ceramic substrate with excellent performance. According to the invention, a Zn < 0.90 > Co < 0.10 > Al < 2 > O < 4 > system is adopted, a CTN (CuO-TiO2-Nb2O5) composite sintering aid is introduced, and sintering and dielectric properties are optimized through a plurality of mechanisms. CuO forms a liquid phase at low temperature, so that particle rearrangement is promoted, sintering stress is relieved, and generation of microcracks is avoided; tiO accelerates the sintering process by enhancing grain boundary diffusion; nbO inhibits overgrowth of crystal grains, refines the crystal grains and improves the density. The introduction of the composite sintering aid also optimizes the dielectric properties, TiO and Nb O adjust the dielectric constant, and CuO reduces the porosity and reduces the scattering loss. The thermal expansion coefficient of Nb O is close to that of ZnAl O, thermal stress is reduced, and thermal shock resistance is improved. In addition, doping of Cu < 2 + > and Nb < 5 + > enhances lattice distortion and interface bonding strength, and further improves material performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave dielectric ceramic materials, and particularly relates to a microwave dielectric ceramic for high-frequency microwave devices with low sintering temperature and high mechanical stability and a preparation method thereof. Background Art

[0002] Low Temperature Co-fired Ceramic (LTCC) technology is an advanced technology that co-sinters ceramic and metal materials at a relatively low temperature, and is widely used in fields such as electronics, sensors, microwaves, and communications. The key feature of this technology is to sinter different materials (such as ceramics and conductive metals) at low temperature, enabling these materials to be processed simultaneously without the need for separate sintering.

[0003] Zinc aluminate (ZnAl₂O₄) as a spinel-structured material is widely used in high-tech fields such as microwave dielectric ceramics, catalyst carriers, and optical coatings due to its excellent mechanical properties, thermal stability, and corrosion resistance. In microwave dielectric ceramics, ZnAl₂O₄ has low dielectric loss and good dielectric constant, making it an ideal material for high-frequency communication, radar systems, and microwave devices. However, despite its great application potential in these fields, the high sintering temperature (usually exceeding 1500 °C) and the difficulty in regulating dielectric properties of ZnAl₂O₄ are still the main bottlenecks restricting its large-scale industrial application.

[0004] The high sintering temperature requires high energy consumption and may cause irreversible changes in the surface and structure of the material, affecting its performance and preparation efficiency. In addition, the dielectric properties of ZnAl₂O₄, especially the dielectric constant and dielectric loss, are restricted by its microstructure, and it is relatively difficult to regulate this property. Traditional sintering processes cannot achieve low-temperature sintering or precise property regulation without sacrificing material performance.

[0005] In recent years, researchers have become a key way to enhance its industrial application potential by introducing composite sintering aids to optimize the sintering behavior and properties of ZnAl₂O₄. The composite sintering aids can not only significantly reduce the sintering temperature, but also optimize its electrical and mechanical properties by improving grain growth, controlling the microstructure, and adjusting the chemical composition of the material. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for improving the properties of zinc aluminate microwave ceramics based on CTN (CuO-TiO₂-Nb₂O₅) composite sintering aids, so that the prepared zinc aluminate microwave dielectric ceramic material has a low sintering temperature and high mechanical stability, and is suitable for manufacturing ceramic substrates with high mechanical strength. The present invention uses Zn 0.90 Co 0.10In the Al2O4 system, a CTN (CuO-TiO2-Nb2O5) composite sintering aid is introduced to optimize the sintering and dielectric properties through multiple mechanisms. CuO forms a liquid phase at low temperatures, promoting particle rearrangement and reducing the sintering temperature; TiO accelerates the sintering process by enhancing grain boundary diffusion; NbO inhibits excessive grain growth, refines the grains and improves the density. The introduction of the composite sintering aid also optimizes the dielectric properties, with TiO and NbO regulating the dielectric constant, while CuO reduces the porosity and scattering loss. The thermal expansion coefficient of NbO is similar to that of ZnAlO, reducing thermal stress and enhancing thermal shock resistance. In addition, the doping of Cu 2+ and Nb 5+ enhances the lattice distortion and interfacial bonding strength, further improving the material properties.

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

[0008] A microwave dielectric ceramic for high-frequency microwave devices with low sintering temperature and high mechanical stability and its preparation method, characterized by including the following steps:

[0009] a. Using ZnO (99%), CoO (99%) and Al2O3 (99%) as raw materials, according to the stoichiometric ratio of the Zn 0.90 Co 0.10 Al2O4 molecular formula for batching to obtain the main powder;

[0010] b. The main powder is ball-milled once, taken out and dried after ball-milling, and the sieved powder after drying is put into a sintering furnace, heated from room temperature to 1300 °C at a heating rate of 2 °C / min and held for 3 h, and then naturally cooled to room temperature with the furnace to obtain the main material;

[0011] c. Using CuO (99%), TiO2 (99.7%) and Nb2O5 (99.9%) as raw materials, after mixing, ball-mill with deionized water for 12 hours. After drying and sieving, the sintering aid CTN (CuO-TiO2-Nb2O5) powder is obtained.

[0012] d. The CTN (CuO-TiO2-Nb2O5) composite sintering aid is added to the main material obtained in step 2 to form a powder material, which is ball-milled twice, and then the twice-ball-milled material is taken out and dried.

[0013] e. The dried powder is uniformly mixed with polyvinyl alcohol (PVA) and pressed into a cylinder (Φ12 mm × h 6 mm).

[0014] f. The pressed cylindrical green body is held at 510 °C for 2 hours to remove PVA, and then heated to 1050 - 1175 °C at a heating rate of 2 °C / min and sintered for 4 hours to obtain the optimized ZnAl2O4 microwave dielectric ceramic material sample.

[0015] Further, in steps b and d, both the first ball milling and the second ball milling are carried out using the same wet ball milling method. The wet ball milling is performed in a planetary ball mill, using deionized water as the solvent and iron balls as the ball milling medium. Among them, the mass ratio of the raw material, the solvent and the iron balls is 1:1.5:2, the ball milling time is 12 hours, and the ball milling speed is 300 r / min.

[0016] Further, in step c, for the three sintering aid raw materials, weigh them according to the optimal molar ratio of 4:1:2 and ball mill them with deionized water for 12 h.

[0017] Further, in steps b and d, the drying temperature is 80 °C and the drying time is 24 hours.

[0018] Further, in step d, the mass percentage of the sintering aid varies between 2% - 6 wt%, adjusting the sintering temperature and mechanical stability.

[0019] Further, in step e, the dosage of the binder is 12 wt%; the sieving process is as follows: sieve through 40 mesh and 100 mesh in sequence, and take the particles between 40 mesh and 100 mesh; the pressure for compacting and forming is 15 Kg / cm 2 , and the time is 2 minutes to press into a cylindrical green body.

[0020] Based on the above technical solutions, the beneficial effects of the present invention are as follows:

[0021] The present invention provides a method for improving the microwave ceramic properties of zinc aluminate based on a CTN (CuO - TiO2 - Nb2O5) composite sintering aid. Using the solid-phase method, Zn 0.90 Co 0.10 Al2O4 microwave dielectric ceramics are prepared through batching, first ball milling, pre-sintering, second ball milling, granulation and high-temperature sintering; the present invention adopts the Zn 0.90 Co 0.10 Al2O4 system, introduces a CTN (CuO - TiO2 - Nb2O5) composite sintering aid, and optimizes the sintering and mechanical properties through multiple mechanisms. CuO forms a liquid phase at low temperature, promotes particle rearrangement, and reduces the sintering temperature; TiO accelerates the sintering process by enhancing grain boundary diffusion; NbO inhibits excessive grain growth, refines grains and improves the density. The introduction of the composite sintering aid also optimizes the dielectric properties. TiO and NbO adjust the dielectric constant, while CuO reduces the porosity and scattering loss. The thermal expansion coefficient of NbO is close to that of ZnAlO, reducing thermal stress and enhancing the thermal shock resistance. In addition, Cu 2+ and Nb 5+The doping enhances the lattice distortion and interface bonding strength, further improving the material properties; finally, the present invention obtains a microwave dielectric ceramic material with a dielectric constant of 6.36, Q×f=8614GHz, a thermal expansion coefficient of 11.62ppm / ℃, a resonant frequency temperature stability coefficient of -38.18ppm / ℃, and a Young's modulus of 210GPa, which is expected to be used to manufacture ceramic substrates with high mechanical strength; and the microwave dielectric ceramic material prepared by the present invention has stable performance and good consistency, which is conducive to the industrial production of ceramic substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the X-ray diffraction pattern of zinc aluminate microwave dielectric ceramic in the invention example.

[0023] Figure 2 This is the curve of the dielectric constant of zinc aluminate changing with the sintering temperature in the invention example.

[0024] Figure 3 Young's modulus of zinc aluminate doped with 4 wt% CTN at different sintering temperatures in the inventive example. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0026] Example 1

[0027] This embodiment provides a method for improving the performance of zinc aluminate microwave ceramics based on a CTN (CuO-TiO2-Nb2O5) composite sintering aid. The chemical expression of the zinc aluminate microwave dielectric ceramic is: Zn 0.90 Co 0.10 Al2O4, specifically comprising the following steps:

[0028] a. Using ZnO (99%), CoO (99%) and Al2O3 (99%) as raw materials, according to Zn 0.90 Co 0.10 The main powder is prepared by mixing the ingredients in a stoichiometric ratio of the Al2O4 molecular formula;

[0029] b. Ball milling was performed once according to the mass ratio of main powder: water: iron ball = 1:1.5:2, the ball milling time was 12 hours, the ball milling speed was 300r / min, and the powder was taken out after ball milling and dried at 80℃. The powder obtained after drying and sifting was put into a sintering furnace, and the temperature was increased from room temperature to 1300℃ at a heating rate of 2℃ / min and kept at this temperature for 3 hours, and then naturally cooled to room temperature with the furnace to obtain the main material;

[0030] c. Weigh CuO (99%), TiO2 (99.7%) and Nb2O5 (99.9%) according to the optimal molar ratio of 4:1:2, and then ball-mill the sintering aid with deionized water for 12 hours. After drying and sieving, the sintering aid CTN (CuO-TiO2-Nb2O5) powder is obtained.

[0031] d. Add the CTN (CuO-TiO2-Nb2O5) composite sintering aid to the main material obtained in step 2 to form a powder material, where the mass percentage of the sintering aid is 2 wt%. Carry out secondary ball-milling according to the ratio of main powder: water: iron balls = 1:1.5:2, with a ball-milling time of 12 h and a ball-milling speed of 300 r / min; then take out the secondary ball-milled material and dry it at 80 °C.

[0032] e. Uniformly mix the dried powder material with 12 wt% polyvinyl alcohol (PVA) and press it into a cylinder (Φ12 mm × h 6 mm) at 20 MPa.

[0033] f. Keep the pressed cylindrical blank at 510 °C for 2 hours to remove PVA, then heat it up to 1125 °C at a heating rate of 2 °C / min and sinter for 4 hours to obtain the optimized ZnAl2O4 microwave dielectric ceramic material sample.

[0034] The zinc aluminate microwave dielectric ceramic material prepared in this example is tested. Among them, the X-ray diffraction pattern is as Figure 1 shown. In the sample of 2 wt% CTN-1125 °C, the crystallinity of ZnAl2O4 is good, and the formation of ZnTiNb2O8 is also observed, which can effectively reduce the sintering temperature. As Figure 2 shown, the dielectric constant of the zinc aluminate microwave dielectric ceramic material in this example is 5.46 and increases with the increase of the sintering temperature. As Figure 3 shown, the thermal expansion coefficient of the zinc aluminate microwave dielectric ceramic material in this example is 12.23. Among them, Q×f = 6470 GHz, the temperature stability coefficient of the resonant frequency is -36.8 ppm / °C, and the Young's modulus is 137 GPa.

[0035] Example 2

[0036] This example provides a method for improving the performance of zinc aluminate microwave ceramics based on the CTN (CuO-TiO2-Nb2O5) composite sintering aid. The chemical formula of the zinc aluminate microwave dielectric ceramic is: Zn 0.90 Co 0.10 Al2O4, which specifically includes the following steps:

[0037] a. Using ZnO (99%), CoO (99%) and Al2O3 (99%) as raw materials, according to Zn 0.90 Co 0.10Prepare the main powder by proportioning the stoichiometric ratio of the chemical formula of Al2O4.

[0038] b. Conduct primary ball milling in the ratio of main powder: water: iron balls = 1:1.5:2 by mass. The ball milling time is 12 h, the ball milling speed is 300 r / min. After ball milling, take it out and dry it at 80 °C. Put the sieved powder into a sintering furnace, heat it from room temperature to 1300 °C at a heating rate of 2 °C / min and hold for 3 h, then cool it naturally to room temperature in the furnace to obtain the main material.

[0039] c. Weigh CuO (99%), TiO2 (99.7%) and Nb2O5 (99.9%) according to the optimal molar ratio of 4:1:2, and then ball mill the sintering aid with deionized water for 12 hours. After drying and sieving, obtain the sintering aid CTN (CuO - TiO2 - Nb2O5) powder.

[0040] d. Add the CTN (CuO - TiO2 - Nb2O5) composite sintering aid to the main material obtained in step 2 to form a powder. The mass percentage of the sintering aid is 2 wt%. Conduct secondary ball milling in the ratio of main powder: water: iron balls = 1:1.5:2 by mass. The ball milling time is 12 h and the ball milling speed is 300 r / min; then take out the secondary ball milled material and dry it at 80 °C.

[0041] e. Uniformly mix the dried powder with 12 wt% polyvinyl alcohol (PVA) and press it into a cylinder (Φ12 mm × h 6 mm) at 20 MPa.

[0042] f. Keep the pressed cylindrical green body at 510 °C for 2 hours to remove PVA, then heat it to 1175 °C at a heating rate of 2 °C / min and sinter for 4 hours to obtain the optimized ZnAl2O4 microwave dielectric ceramic material sample.

[0043] Test the zinc aluminate microwave dielectric ceramic material prepared in this example. Among them, the X-ray diffraction pattern is as Figure 1 shown. In the sample of 2 wt% CTN - 1175 °C, the crystallinity of ZnAl2O4 is good, and the formation of ZnTiNb2O8 is also observed, which can effectively reduce the sintering temperature. As Figure 2 shown, the dielectric constant of the zinc aluminate microwave dielectric ceramic material in this example is 6.03 and increases with the increase of the sintering temperature. As Figure 3 shown, the thermal expansion coefficient of the zinc aluminate microwave dielectric ceramic material in this example is 11.53. Among them, Q×f = 6723 GHz, the temperature stability coefficient of the resonance frequency is -47.51 ppm / °C, and the Young's modulus is 153 GPa..

[0044] Example 3

[0045] This embodiment provides a method for improving the performance of zinc aluminate microwave ceramics based on a CTN (CuO-TiO2-Nb2O5) composite sintering aid. The chemical expression of the zinc aluminate microwave dielectric ceramic is: Zn 0.90 Co 0.10 Al2O4, specifically comprising the following steps:

[0046] a. Using ZnO (99%), CoO (99%) and Al2O3 (99%) as raw materials, according to Zn 0.90 Co 0.10 The main powder is prepared by mixing the ingredients in a stoichiometric ratio of the Al2O4 molecular formula;

[0047] b. Ball milling was performed once according to the mass ratio of main powder: water: iron ball = 1:1.5:2, the ball milling time was 12 hours, the ball milling speed was 300r / min, and the powder was taken out after ball milling and dried at 80℃. The powder obtained after drying and sifting was put into a sintering furnace, and the temperature was increased from room temperature to 1300℃ at a heating rate of 2℃ / min and kept at this temperature for 3 hours, and then naturally cooled to room temperature with the furnace to obtain the main material;

[0048] c. Weigh CuO (99%), TiO2 (99.7%) and Nb2O5 (99.9%) in an optimal molar ratio of 4:1:2, and then ball-mill the sintering aid with deionized water for 12 hours. After drying and sieving, the sintering aid CTN (CuO-TiO2-Nb2O5) powder is obtained.

[0049] d. CTN (CuO-TiO2-Nb2O5) composite sintering aid is added to the main material obtained in step 2 to form a powder, wherein the mass percentage of the sintering aid is 4wt%. Secondary ball milling is performed in the mass ratio of main powder: water: iron ball = 1:1.5:2, the ball milling time is 12h, and the ball milling speed is 300r / min; then the secondary ball milled material is taken out and dried at 80°C.

[0050] e. The dried powder was uniformly mixed with 12 wt% polyvinyl alcohol (PVA), and pressed into a cylinder (Φ12 mm×h 6 mm) at 20 MPa.

[0051] f. The pressed cylindrical body is kept at 510° C. for 2 hours to remove PVA, then heated to 1050° C. at a heating rate of 2° C. / min, and sintered for 4 hours to obtain the optimized ZnAl 2 O 4 microwave dielectric ceramic material sample.

[0052] The zinc aluminate microwave dielectric ceramic material prepared in this embodiment was tested. Among them, the X-ray diffraction spectrum is as follows Figure 1As shown in the figure, in the 4wt%CTN-1050℃ sample, the crystallinity of ZnAl2O4 is good, and the formation of ZnTiNb2O8 is also observed, which can effectively reduce the sintering temperature. Figure 2 As shown in FIG. 1 , the dielectric constant of the zinc aluminate microwave dielectric ceramic material in this example is 5.92. Figure 3 As shown, the thermal expansion coefficient of the zinc aluminate microwave dielectric ceramic material in this example is 11.23. Where Q×f=6614GHz, the resonant frequency temperature stability coefficient is -30.92ppm / ℃, as shown in FIG. Figure 3 As shown, the Young's modulus is 211 GPa.

[0053] Example 4

[0054] This embodiment provides a method for improving the performance of zinc aluminate microwave ceramics based on a CTN (CuO-TiO2-Nb2O5) composite sintering aid. The chemical expression of the zinc aluminate microwave dielectric ceramic is: Zn 0.90 Co 0.10 Al2O4, specifically comprising the following steps:

[0055] a. Using ZnO (99%), CoO (99%) and Al2O3 (99%) as raw materials, according to Zn 0.90 Co 0.10 The main powder is prepared by mixing the ingredients in a stoichiometric ratio of the Al2O4 molecular formula;

[0056] b. Ball milling was performed once according to the mass ratio of main powder: water: iron ball = 1:1.5:2, the ball milling time was 12 hours, the ball milling speed was 300r / min, and the powder was taken out after ball milling and dried at 80℃. The powder obtained after drying and sifting was put into a sintering furnace, and the temperature was increased from room temperature to 1300℃ at a heating rate of 2℃ / min and kept at this temperature for 3 hours, and then naturally cooled to room temperature with the furnace to obtain the main material;

[0057] c. Weigh CuO (99%), TiO2 (99.7%) and Nb2O5 (99.9%) in an optimal molar ratio of 4:1:2, and then ball-mill the sintering aid with deionized water for 12 hours. After drying and sieving, the sintering aid CTN (CuO-TiO2-Nb2O5) powder is obtained.

[0058] d. CTN (CuO-TiO2-Nb2O5) composite sintering aid is added to the main material obtained in step 2 to form a powder, wherein the mass percentage of the sintering aid is 4wt%. Secondary ball milling is performed in the mass ratio of main powder: water: iron ball = 1:1.5:2, the ball milling time is 12h, and the ball milling speed is 300r / min; then the secondary ball milled material is taken out and dried at 80°C.

[0059] e. The dried powder was uniformly mixed with 12 wt% polyvinyl alcohol (PVA), and pressed into a cylinder (Φ12 mm×h 6 mm) at 20 MPa.

[0060] f. The pressed cylindrical body is kept at 510° C. for 2 hours to remove PVA, then heated to 1100° C. at a heating rate of 2° C. / min, and sintered for 4 hours to obtain the optimized ZnAl 2 O 4 microwave dielectric ceramic material sample.

[0061] The zinc aluminate microwave dielectric ceramic material prepared in this example was tested. The X-ray diffraction pattern is as follows: Figure 1 As shown in the figure, in the sample with 4wt%CTN-1100℃, the crystallinity of ZnAl2O4 is good, and the formation of ZnTiNb2O8 is also observed, which can effectively reduce the sintering temperature. Figure 2 As shown in FIG. 1 , the dielectric constant of the zinc aluminate microwave dielectric ceramic material in this example is 6.36. Figure 3 As shown, the thermal expansion coefficient of the zinc aluminate microwave dielectric ceramic material in this example is 11.62. Where Q×f=8614GHz, the resonant frequency temperature stability coefficient is -38.18ppm / ℃, as shown in FIG. Figure 3 As shown, the Young's modulus is 221 GPa.

[0062] Example 5

[0063] This embodiment provides a method for improving the performance of zinc aluminate microwave ceramics based on a CTN (CuO-TiO2-Nb2O5) composite sintering aid. The chemical expression of the zinc aluminate microwave dielectric ceramic is: Zn 0.90 Co 0.10 Al2O4, specifically comprising the following steps:

[0064] a. Using ZnO (99%), CoO (99%) and Al2O3 (99%) as raw materials, according to Zn 0.90 Co 0.10 The main powder is prepared by mixing the ingredients in a stoichiometric ratio of the Al2O4 molecular formula;

[0065] b. Ball milling was performed once according to the mass ratio of main powder: water: iron ball = 1:1.5:2, the ball milling time was 12 hours, the ball milling speed was 300r / min, and the powder was taken out after ball milling and dried at 80℃. The powder obtained after drying and sifting was put into a sintering furnace, and the temperature was increased from room temperature to 1300℃ at a heating rate of 2℃ / min and kept at this temperature for 3 hours, and then naturally cooled to room temperature with the furnace to obtain the main material;

[0066] c. Weigh CuO (99%), TiO2 (99.7%) and Nb2O5 (99.9%) according to the optimal molar ratio of 4:1:2, and then ball-mill the sintering aid with deionized water for 12 hours. After drying and sieving, the sintering aid CTN (CuO-TiO2-Nb2O5) powder is obtained.

[0067] d. Add the CTN (CuO-TiO2-Nb2O5) composite sintering aid to the main material obtained in step 2 to form a powder material, where the mass percentage of the sintering aid is 6 wt%. Perform secondary ball-milling according to the ratio of main powder:water:iron balls = 1:1.5:2, with a ball-milling time of 12 h and a ball-milling speed of 300 r / min; then take out the secondary ball-milled material and dry it at 80 °C.

[0068] e. Uniformly mix the dried powder material with 12 wt% polyvinyl alcohol (PVA) and press it into a cylinder (Φ12 mm × h 6 mm) at 20 MPa.

[0069] f. Keep the pressed cylindrical green body at 510 °C for 2 hours to remove PVA, then heat it to 1000 °C at a heating rate of 2 °C / min and sinter for 4 hours to obtain the optimized ZnAl2O4 microwave dielectric ceramic material sample.

[0070] The zinc aluminate microwave dielectric ceramic material prepared in this example is tested. Among them, the X-ray diffraction pattern is as Figure 1 shown. In the 6 wt% CTN-1000 °C sample, the crystallinity of ZnAl2O4 is good, and the formation of ZnTiNb2O8 is also observed, which can effectively reduce the sintering temperature. As Figure 2 shown, the dielectric constant of the zinc aluminate microwave dielectric ceramic material in this example is 6.82. As Figure 3 shown, the thermal expansion coefficient of the zinc aluminate microwave dielectric ceramic material in this example is 10.62. Among them, Q×f = 6072 GHz, the resonance frequency temperature stability coefficient is -40.03 ppm / °C, and the Young's modulus is 232 GPa.

[0071] Example 6

[0072] This example provides a method for improving the performance of zinc aluminate microwave ceramics based on the CTN (CuO-TiO2-Nb2O5) composite sintering aid. The chemical formula of the zinc aluminate microwave dielectric ceramic is: Zn 0.90 Co 0.10 Al2O4, which specifically includes the following steps:

[0073] a. Using ZnO (99%), CoO (99%) and Al2O3 (99%) as raw materials, according to Zn 0.90 Co 0.10Prepare the main powder by proportioning the stoichiometric ratio of the chemical formula of Al2O4.

[0074] b. Conduct primary ball milling in the ratio of main powder : water : iron balls = 1 : 1.5 : 2 by mass. The ball milling time is 12 h, the ball milling speed is 300 r / min. After ball milling, take it out and dry it at 80 °C. Put the sieved powder into a sintering furnace, heat it from room temperature to 1300 °C at a heating rate of 2 °C / min and hold for 3 h, then cool it naturally to room temperature in the furnace to obtain the main material.

[0075] c. Weigh CuO (99%), TiO2 (99.7%) and Nb2O5 (99.9%) according to the optimal molar ratio of 4 : 1 : 2, and then ball mill the sintering aid with deionized water for 12 hours. After drying and sieving, obtain the sintering aid CTN (CuO - TiO2 - Nb2O5) powder.

[0076] d. Add the CTN (CuO - TiO2 - Nb2O5) composite sintering aid to the main material obtained in step 2 to form a powder. The mass percentage of the sintering aid is 6 wt%. Conduct secondary ball milling in the ratio of main powder : water : iron balls = 1 : 1.5 : 2 by mass. The ball milling time is 12 h and the ball milling speed is 300 r / min; then take out the secondary ball milled material and dry it at 80 °C.

[0077] e. Uniformly mix the dried powder with 12 wt% polyvinyl alcohol (PVA) and press it into a cylinder (Φ12 mm × h 6 mm) at 20 MPa.

[0078] f. Keep the pressed cylindrical blank at 510 °C for 2 hours to remove PVA, then heat it to 1050 °C at a heating rate of 2 °C / min and sinter for 4 hours to obtain the optimized ZnAl2O4 microwave dielectric ceramic material sample.

[0079] Test the zinc aluminate microwave dielectric ceramic material prepared in this example. Among them, the X-ray diffraction pattern is as Figure 1 shown. In the 6 wt% CTN - 1050 °C sample, the crystallinity of ZnAl2O4 is good, and the formation of ZnTiNb2O8 is also observed, which can effectively reduce the sintering temperature. As Figure 2 shown, the dielectric constant of the zinc aluminate microwave dielectric ceramic material in this example is 7.13. As Figure 3 shown, the thermal expansion coefficient of the zinc aluminate microwave dielectric ceramic material in this example is 11.25. Among them, Q×f = 10952 GHz, the resonance frequency temperature stability coefficient is -36.86 ppm / °C, and the Young's modulus is 263 GPa.

[0080] By comparison, it is found that in Example 4, when the sintering temperature is 1100 °C and the mass percentage of the sintering aid is 4 wt%, the performance of the obtained sample is the best. Its dielectric constant is 6.36, Q×f = 8614 GHz, the coefficient of thermal expansion is 11.62 ppm / °C, the temperature stability coefficient of the resonance frequency is -38.18 ppm / °C, and the Young's modulus is 221 GPa. It shows that the addition of the sintering aid not only reduces the sintering temperature, but also significantly improves its Young's modulus, greatly improving the mechanical properties. At the same time, the dielectric properties and quality factor are also optimized to a certain extent.

[0081] The above are only specific embodiments of the present invention. Any feature disclosed in this specification, unless specifically stated, can be replaced by other equivalent or features with similar purposes; all the features disclosed, or all the steps in any method or process, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A microwave dielectric ceramic for high-frequency microwave devices with low sintering temperature and high mechanical stability and a preparation method thereof, characterized in that It includes the following steps: a. Using ZnO (99%), CoO (99%) and Al2O3 (99%) as raw materials, according to the stoichiometric ratio of the Zn 0.90 Co 0.10 Al2O4 molecular formula for batching, the main powder is prepared; b. The main powder is ball-milled for the first time. After ball-milling, it is taken out and dried. The powder obtained after sieving is put into a sintering furnace and heated from room temperature to 1300 °C at a heating rate of 2 °C / min and held for 3 h, and then cooled naturally to room temperature in the furnace to obtain the main material; c. Using CuO (99%), TiO2 (99.7%) and Nb2O5 (99.9%) as raw materials, after mixing, it is ball-milled with deionized water for 12 hours. After drying and sieving, the sintering aid CTN (CuO-TiO2-Nb2O5) powder is obtained. d. The CTN (CuO-TiO2-Nb2O5) composite sintering aid is added to the main material obtained in step 2 to form a powder, and then ball-milled for the second time, and then the second ball-milled material is taken out and dried. e. The dried powder is uniformly mixed with polyvinyl alcohol (PVA) and pressed into a cylinder (Φ12mm×h 6mm). f. The pressed cylindrical green body is held at 510 °C for 2 hours to remove PVA, and then heated to 1050-1175 °C at a heating rate of 2 °C / min and sintered for 4 hours to obtain the optimized ZnAl2O4 microwave dielectric ceramic material sample.

2. The method for improving the properties of zinc aluminate microwave ceramics based on CTN sintering aids according to claim 1, characterized in that In steps b and d, the first ball-milling and the second ball-milling both adopt the same wet ball-milling. The wet ball-milling is carried out in a planetary ball mill, and deionized water is used as the solvent and iron balls are used as the ball-milling medium for wet ball-milling. Among them, the mass ratio of raw materials, solvent and iron balls is 1:1.5:2, the ball-milling time is 12 hours, and the ball-milling speed is 300 r / min.

3. The method for improving the properties of zinc aluminate microwave dielectric ceramics based on CTN sintering aids according to claim 1, characterized in that, In step c, for the three sintering aid raw materials, they are weighed according to the optimal molar ratio of 4:1:2 and ball-milled with deionized water for 12 h.

4. The method for improving the properties of zinc aluminate microwave dielectric ceramics based on CTN sintering aid according to claim 1, characterized in that In steps b and d, the drying temperature is 80 °C and the drying time is 24 hours.

5. The method for improving the properties of zinc aluminate microwave dielectric ceramics based on the CTN sintering aid according to claim 1, wherein In step d, the mass percentage of the sintering aid varies between 2%-6 wt%, and the sintering temperature and mechanical stability are adjusted.

6. The method for improving the properties of zinc aluminate microwave dielectric ceramics based on CTN sintering aids according to claim 1, characterized in that In step e, the dosage of the binder is 12 wt%; the sieving process is as follows: sieving through 40 mesh and 100 mesh in sequence, and taking the particles between 40 mesh and 100 mesh; the pressure for briquetting is 15 Kg / cm 2 , the time is 2 minutes, and a cylindrical green body is pressed.

Images