A medium-entropy low-dielectric microwave ceramic

Abstract

This invention discloses a medium-entropy low-dielectric microwave ceramic, belonging to the field of electronic ceramic materials technology. Its preparation method includes the following steps: Step 1: Mixing MgO, CoO, and ZnO powders in an equimolar ratio to obtain mixture Z. Using deionized water as the grinding medium, mixture Z is ground in a ball mill using a wet grinding method until the particle size is less than 10 micrometers. The mixture is then dried to obtain a mixed powder. Step 2: Adding citric acid and ethylene glycol to a mixed aqueous solution of MgCl2, CoCl2, and ZnCl2, and heating and stirring, yields a mixed solution C. Step 3: Weighing whisker-based porous silica powder and adding it to the mixed solution C from Step 2, stirring, adjusting the pH with sodium bicarbonate, continuing stirring, heating, and then adding the mixed powder obtained in Step 1. After stirring, the mixture is filtered, pressed into shape, and sintered sequentially to obtain the medium-entropy low-dielectric microwave ceramic. The medium-entropy low-dielectric microwave ceramic prepared by this invention has low dielectric constant and low dielectric loss, exhibiting superior overall performance and meeting application requirements.

Description

Technical Field

[0001] This invention belongs to the field of electronic ceramic materials technology, specifically relating to a medium-entropy low-dielectric microwave ceramic. Background Technology

[0002] Microwaves generally refer to electromagnetic waves with frequencies between 300MHz and 300GHz and wavelengths between 1mm and 1m. Microwave ceramic materials are used in microwave circuits to achieve the transmission, reflection, and absorption of electromagnetic waves, and are widely used in the manufacture of dielectric resonators, dielectric filters, duplexers, and microwave dielectric antennas, among other microwave technologies.

[0003] Among the many microwave ceramic materials, magnesium silicate (Mg2SiO4) has attracted much attention in research both at home and abroad. Magnesium silicate (Mg2SiO4) has a low dielectric constant, but its overall performance is not ideal, which limits its application to a certain extent. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a medium-entropy low-dielectric microwave ceramic, which solves the problems mentioned in the background section.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A medium-entropy low-dielectric microwave ceramic is composed of ternary silicate A2SiO4 and whisker composite porous silicon micropowder, wherein A is composed of equimolar elements Mg, Co and Zn.

[0009] The above-mentioned method for preparing a medium-entropy low-dielectric microwave ceramic includes the following steps:

[0010] Step 1: Mix MgO, CoO and ZnO powders in equimolar ratio to obtain mixture Z. Grind mixture Z in a ball mill with deionized water as the grinding medium using wet grinding method until the particle size is less than 10 micrometers. Dry the mixture to obtain mixed powder.

[0011] Step 2: By weight, add 0.1-0.3 parts citric acid and 1-2 parts ethylene glycol to 50-100 parts of the mixed aqueous solution, heat to 60-80℃, and stir for 0.5-1h to obtain mixed solution C. The solutes in the mixed aqueous solution include MgCl2, CoCl2 and ZnCl2, and the concentrations of MgCl2, CoCl2 and ZnCl2 are all 0.2-0.3 mol / L.

[0012] Step 3: Weigh 5 parts by weight of whisker composite porous silicon micro powder and add it to the mixture C in Step 2. Stir for 20-40 minutes, adjust the pH to 9-10 with sodium bicarbonate, continue stirring for 1-2 hours, heat to 60-80℃, then add 2-4 parts of the mixed powder obtained in Step 1, stir for 10-20 minutes, filter, press into shape, and sinter to obtain medium-entropy low-dielectric microwave ceramic.

[0013] The method for preparing the whisker composite porous silicon micropowder includes the following steps:

[0014] S1. By weight, take 10 parts of silica powder and 0.18-0.22 parts of refined naphthalene, add 30-50 parts of diethyl ether, stir evenly, heat and evaporate to obtain a solid.

[0015] S2. By weight, the solids in S1 are mixed with 6-10 parts of modified Si3N4 powder to obtain solid mixture B. 10-15 parts of solid mixture B are added to 10-15 parts of a 1% polyvinyl alcohol aqueous solution and wet ball milled to obtain a mixed slurry.

[0016] S3. Place the above mixed slurry in a drying oven to dry, then shape and sinter it at a temperature of 1450-1550℃. After cooling to room temperature, crush it and pass it through an 80-120 mesh sieve to obtain whisker composite porous silicon micro powder.

[0017] Furthermore, the preparation method of the modified Si3N4 powder includes the following steps:

[0018] Q1. By weight, add 5 parts of α-Si3N4 powder to 40-60 parts of sodium polyacrylate aqueous solution with a mass concentration of 2-4%, heat to 40-60℃, stir for 10-30 min, then add 0.2-0.4 parts of hydrogen peroxide solution with a mass fraction of 30%, stir for 1-2 h, and filter to obtain pretreated powder;

[0019] Q2. By weight, take 0.3-0.5 parts of phosphoric acid and add it to 10-20 parts of ethanol, then add 0.4-0.6 parts of nano magnesium fluoride, and continue stirring for 5-15 minutes to obtain the modified solution;

[0020] Q3. Add the pretreated powder of Q1 to the modification solution of Q2, stir for 1-2 hours, filter, place in a muffle furnace, calcine for 0.5-1 hours, and cool to room temperature to obtain modified Si3N4 powder.

[0021] Furthermore, the calcination temperature in Q3 is 300–400°C, and the calcination time is 0.5–1 h.

[0022] Furthermore, the sintering temperature in S3 is 1450–1550°C, and the sintering time is 1–2 hours.

[0023] Furthermore, the sintering temperature in step 3 is 1300–1500℃, and the sintering time is 2–6 hours.

[0024] Furthermore, the heating rate of sintering in step 3 is 1 to 10 °C / min.

[0025] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0026] 1. In the preparation of the modified silicon nitride powder of this invention, sodium polyacrylate is added to treat the surface of α-Si3N4 powder, giving it high compatibility. Then, phosphoric acid and nano-magnesium fluoride are added to achieve mutual doping between inorganic powders. The addition of nano-magnesium fluoride can improve the quality factor of the material. Furthermore, during the subsequent formation of Si3N4 whiskers, the nano-magnesium fluoride adheres to the Si3N4 grain boundaries, inhibiting grain growth and thus fixing and strengthening the grain boundaries.

[0027] 2. The whisker composite porous silica powder obtained by combining modified silicon nitride powder with silica, wherein the addition of refined naphthalene creates a porous structure, giving the whisker composite porous silica powder a low dielectric constant. At the same time, the porous structure provides a reaction matrix for silica and metal elements, generating a large amount of ternary silicate (A2SiO4) in situ at the pore interface, avoiding the formation of a second phase, and ensuring the dielectric properties and reaction stability of the generated ternary silicate (A2SiO4). Ultimately, the synergistic effect of the porous structure and modified silicon nitride in the solution is realized, resulting in a ceramic material with excellent properties of low dielectric constant and low dielectric loss. Attached Figure Description

[0028] Appendix Figure 1 The image shows the XRD pattern of the medium-entropy low-dielectric microwave ceramic prepared in Example 1 of this invention. Detailed Implementation

[0029] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] Example 1

[0031] A medium-entropy low-dielectric microwave ceramic is composed of ternary silicate A2SiO4 and whisker composite porous silicon micropowder, wherein A is composed of equimolar elements Mg, Co and Zn.

[0032] First, modified Si3N4 powder is prepared. The method for preparing modified Si3N4 powder includes the following steps:

[0033] Q1. By weight, add 5 parts of α-Si3N4 powder to 50 parts of sodium polyacrylate aqueous solution with a mass concentration of 3%, heat to 50°C, stir for 20 min, then add 0.3 parts of hydrogen peroxide solution with a mass fraction of 30% dropwise at a uniform rate, stir for 1 h, and filter to obtain the pretreated powder;

[0034] Q2. By weight, take 0.4 parts of phosphoric acid and add it to 15 parts of ethanol, then add 0.5 parts of nano magnesium fluoride, and continue stirring for 10 minutes to obtain the modified solution;

[0035] Q3. Add the pretreated powder of Q1 to the modified liquid of Q2, stir for 1.5h, filter, put into a muffle furnace, calcine at 350℃ for 0.7h, cool to room temperature, and obtain modified Si3N4 powder.

[0036] Then, the whisker composite porous silicon micropowder is prepared, including the following steps:

[0037] S1. By weight, take 10 parts of silica powder and 0.20 parts of refined naphthalene, add 40 parts of diethyl ether, stir evenly, heat and evaporate, recover the diethyl ether in the evaporator for reuse, and obtain the remaining solid.

[0038] S2. By weight, the solid in S1 is mixed with 8 parts of modified Si3N4 powder to obtain solid mixture B. 10 parts of solid mixture B are added to 10 parts of polyvinyl alcohol aqueous solution with a mass fraction of 1% and wet ball milling is performed to obtain a mixed slurry.

[0039] S3. Place the above mixed slurry in a drying oven to dry, then shape and sinter it at a temperature of 1500℃ for 1 hour. After cooling to room temperature, crush it and pass it through a 100-mesh sieve to obtain whisker composite porous silicon micro powder.

[0040] A method for preparing medium-entropy low-dielectric microwave ceramics includes the following steps:

[0041] Step 1: Mix MgO, CoO and ZnO powders in equimolar ratio to obtain a solid mixture Z. Grind the mixture Z in a ball mill with deionized water as the grinding medium using a wet grinding method until the particle size is less than 10 micrometers. Dry the mixture to obtain a mixed powder.

[0042] Step 2: By weight, add 0.2 parts citric acid and 1.5 parts ethylene glycol to 100 parts of the mixed aqueous solution, heat to 70°C, and stir for 0.5 h to obtain mixed solution C. The solutes in the mixed aqueous solution include MgCl2, CoCl2 and ZnCl2, and the concentrations of MgCl2, CoCl2 and ZnCl2 are all 0.25 mol / L.

[0043] Step 3: Weigh 5 parts by weight of the whisker composite porous silica powder and add it to the mixture C from Step 2. Stir for 30 minutes, adjust the pH to 9 with sodium bicarbonate, continue stirring for 1 hour, heat to 70°C, then add 3 parts of the mixed powder obtained in Step 1, stir for 15 minutes, and then filter, press into shape, and sinter. After sintering, a medium-entropy low-dielectric microwave ceramic is obtained. The sintering process involves heating to 1400°C at a rate of 5°C / min and then holding at that temperature for 4 hours to obtain the medium-entropy low-dielectric microwave ceramic.

[0044] Example 2

[0045] A medium-entropy low-dielectric microwave ceramic is composed of ternary silicate A2SiO4 and whisker composite porous silicon micropowder, wherein A is composed of equimolar elements Mg, Co and Zn.

[0046] First, modified Si3N4 powder is prepared. The method for preparing modified Si3N4 powder includes the following steps:

[0047] Q1. By weight, add 5 parts of α-Si3N4 powder to 40 parts of sodium polyacrylate aqueous solution with a mass concentration of 2%, heat to 40°C, stir for 10 min, then add 0.2 parts of hydrogen peroxide solution with a mass fraction of 30%, stir for 1 h, and filter to obtain pretreated powder;

[0048] Q2. By weight, add 0.3 parts of phosphoric acid to 10 parts of ethanol, then add 0.4 parts of nano magnesium fluoride, and continue stirring for 5 minutes to obtain the modified solution;

[0049] Q3. Add the pretreated powder of Q1 to the modification solution of Q2, stir for 1 hour, filter, put it into a muffle furnace, calcine at 300℃ for 0.5 hours, and cool to room temperature to obtain modified Si3N4 powder.

[0050] Then, the whisker composite porous silicon micropowder is prepared, including the following steps:

[0051] S1. By weight, take 10 parts of silica powder and 0.18 parts of refined naphthalene, add 30 parts of diethyl ether, stir evenly, heat and evaporate, recover the diethyl ether in the evaporator for reuse, and obtain the remaining solid.

[0052] S2. By weight, the solid in S1 is mixed with 6 parts of modified Si3N4 powder to obtain solid mixture B. 10 parts of solid mixture B are added to 10 parts of a 1% polyvinyl alcohol aqueous solution and wet ball milled to obtain a mixed slurry.

[0053] S3. The above mixed slurry is placed in a drying oven to dry, and then shaped and sintered at a temperature of 1450℃ for 1.5h. After cooling to room temperature, it is crushed and passed through an 80-mesh sieve to obtain whisker composite porous silicon micro powder.

[0054] A method for preparing medium-entropy low-dielectric microwave ceramics includes the following steps:

[0055] Step 1: Mix MgO, CoO and ZnO powders in equimolar ratio to obtain a solid mixture Z. Grind the mixture Z in a ball mill with deionized water as the grinding medium using a wet grinding method until the particle size is less than 10 micrometers. Dry the mixture to obtain a mixed powder.

[0056] Step 2: By weight, add 0.1 parts citric acid and 1 part ethylene glycol to 50 parts of the mixed aqueous solution, heat to 60°C, and stir for 0.5 h to obtain mixed solution C. The solutes in the mixed aqueous solution include MgCl2, CoCl2 and ZnCl2, and the concentrations of MgCl2, CoCl2 and ZnCl2 are all 0.2 mol / L.

[0057] Step 3: Weigh 5 parts by weight of the whisker composite porous silica powder and add it to the mixture C from Step 2. Stir for 20 minutes, adjust the pH to 9 with sodium bicarbonate, continue stirring for 1 hour, heat to 60°C, then add 2 parts of the mixed powder obtained in Step 1, stir for 10 minutes, and then filter, press into shape, and sinter. After sintering, a medium-entropy low-dielectric microwave ceramic is obtained. The sintering process involves heating to 1300°C at a rate of 1°C / min and then holding at that temperature for 2 hours to obtain the medium-entropy low-dielectric microwave ceramic.

[0058] Example 3

[0059] A medium-entropy low-dielectric microwave ceramic is composed of ternary silicate A2SiO4 and whisker composite porous silicon micropowder, wherein A is composed of equimolar elements Mg, Co and Zn.

[0060] First, modified Si3N4 powder is prepared. The method for preparing modified Si3N4 powder includes the following steps:

[0061] Q1. By weight, add 5 parts of α-Si3N4 powder to 60 parts of sodium polyacrylate aqueous solution with a mass concentration of 4%, heat to 60°C, stir for 30 min, then add 0.4 parts of hydrogen peroxide solution with a mass fraction of 30%, stir for 2 h, and filter to obtain pretreated powder;

[0062] Q2. By weight, add 0.5 parts of phosphoric acid to 20 parts of ethanol, then add 0.6 parts of nano magnesium fluoride, and continue stirring for 15 minutes to obtain the modified solution;

[0063] Q3. Add the pretreated powder of Q1 to the modification solution of Q2, stir for 2 hours, filter, place in a muffle furnace, calcine at 400℃ for 1 hour, cool to room temperature, and obtain modified Si3N4 powder.

[0064] Then, the whisker composite porous silicon micropowder is prepared, including the following steps:

[0065] S1. By weight, take 10 parts of silica powder and 0.22 parts of refined naphthalene, add 50 parts of diethyl ether, stir evenly, heat and evaporate, recover the diethyl ether in the evaporator for reuse, and obtain the remaining solid.

[0066] S2. By weight, the solid in S1 is mixed with 10 parts of modified Si3N4 powder to obtain solid mixture B. 15 parts of solid mixture B are added to 15 parts of polyvinyl alcohol aqueous solution with a mass fraction of 1% and wet ball milling is performed to obtain a mixed slurry.

[0067] S3. Place the above mixed slurry in a drying oven to dry, then shape and sinter it at a temperature of 1550℃ for 1 hour. After cooling to room temperature, crush it and pass it through a 120-mesh sieve to obtain whisker composite porous silicon micro powder.

[0068] A method for preparing medium-entropy low-dielectric microwave ceramics includes the following steps:

[0069] Step 1: Mix MgO, CoO and ZnO powders in equimolar ratio to obtain a solid mixture Z. Grind the mixture Z in a ball mill with deionized water as the grinding medium using a wet grinding method until the particle size is less than 10 micrometers. Dry the mixture to obtain a mixed powder.

[0070] Step 2: By weight, add 0.3 parts citric acid and 2 parts ethylene glycol to 100 parts of the mixed aqueous solution, heat to 80°C, and stir for 1 hour to obtain mixed solution C. The solutes in the mixed aqueous solution include MgCl2, CoCl2 and ZnCl2, and the concentrations of MgCl2, CoCl2 and ZnCl2 are all 0.3 mol / L.

[0071] Step 3: Weigh 5 parts by weight of the whisker composite porous silica powder and add it to the mixture C from Step 2. Stir for 40 min, adjust the pH to 10 with sodium bicarbonate, continue stirring for 2 h, heat to 80℃, then add 4 parts of the mixed powder obtained in Step 1, stir for 20 min, and then filter, press into shape, and sinter. After sintering, a medium-entropy low-dielectric microwave ceramic is obtained. The sintering process involves heating to 1500℃ at a rate of 10℃ / min and then holding at that temperature for 6 hours to obtain the medium-entropy low-dielectric microwave ceramic.

[0072] Example 4

[0073] A medium-entropy low-dielectric microwave ceramic is composed of ternary silicate A2SiO4 and whisker composite porous silicon micropowder, wherein A is composed of equimolar elements Mg, Co and Zn.

[0074] First, modified Si3N4 powder is prepared. The method for preparing modified Si3N4 powder includes the following steps:

[0075] Q1. By weight, add 5 parts of α-Si3N4 powder to 45 parts of sodium polyacrylate aqueous solution with a mass concentration of 2.5%, heat to 45°C, stir for 15 min, then add 0.25 parts of hydrogen peroxide solution with a mass fraction of 30%, stir for 1.2 h, and filter to obtain pretreated powder;

[0076] Q2. By weight, add 0.35 parts of phosphoric acid to 12 parts of ethanol, then add 0.45 parts of nano magnesium fluoride, and continue stirring for 8 minutes to obtain the modified solution;

[0077] Q3. Add the pretreated powder of Q1 to the modified liquid of Q2, stir for 1.2 h, filter, put into a muffle furnace, calcine at 320℃ for 0.6 h, cool to room temperature, and obtain modified Si3N4 powder.

[0078] Then, the whisker composite porous silicon micropowder is prepared, including the following steps:

[0079] S1. By weight, take 10 parts of silica powder and 0.19 parts of refined naphthalene, add 35 parts of diethyl ether, stir evenly, heat and evaporate, recover the diethyl ether in the evaporator for reuse, and obtain the remaining solid.

[0080] S2. By weight, the solid in S1 is mixed with 7 parts of modified Si3N4 powder to obtain solid mixture B. 11 parts of solid mixture B are added to 12 parts of polyvinyl alcohol aqueous solution with a mass fraction of 1% and wet ball milling is performed to obtain a mixed slurry.

[0081] S3. Place the above mixed slurry in a drying oven to dry, then shape and sinter it at a temperature of 1480℃ for 1 hour. After cooling to room temperature, crush it and pass it through a 90-mesh sieve to obtain whisker composite porous silicon micro powder.

[0082] A method for preparing medium-entropy low-dielectric microwave ceramics includes the following steps:

[0083] Step 1: Mix MgO, CoO and ZnO powders in equimolar ratio to obtain a solid mixture Z. Grind the mixture Z in a ball mill with deionized water as the grinding medium using a wet grinding method until the particle size is less than 10 micrometers. Dry the mixture to obtain a mixed powder.

[0084] Step 2: By weight, add 0.15 parts citric acid and 1.2 parts ethylene glycol to 60 parts of the mixed aqueous solution, heat to 65°C, and stir for 0.6 h to obtain mixed solution C. The solutes in the mixed aqueous solution include MgCl2, CoCl2 and ZnCl2, and the concentrations of MgCl2, CoCl2 and ZnCl2 are all 0.23 mol / L.

[0085] Step 3: Weigh 5 parts by weight of the whisker composite porous silica powder and add it to the mixture C from Step 2. Stir for 25 min, adjust the pH to 9 with sodium bicarbonate, continue stirring for 1.2 h, heat to 65℃, then add 2.5 parts of the mixed powder obtained in Step 1, stir for 12 min, and then filter, press into shape, and sinter. After sintering, a medium-entropy low-dielectric microwave ceramic is obtained. The sintering process involves heating to 1350℃ at a rate of 4℃ / min, and then holding at that temperature for 3 hours to obtain the medium-entropy low-dielectric microwave ceramic.

[0086] Example 5

[0087] A medium-entropy low-dielectric microwave ceramic is composed of ternary silicate A2SiO4 and whisker composite porous silicon micropowder, wherein A is composed of equimolar elements Mg, Co and Zn.

[0088] First, modified Si3N4 powder is prepared. The method for preparing modified Si3N4 powder includes the following steps:

[0089] Q1. By weight, add 5 parts of α-Si3N4 powder to 55 parts of sodium polyacrylate aqueous solution with a mass concentration of 3.5%, heat to 55°C, stir for 25 min, then add 0.35 parts of hydrogen peroxide solution with a mass fraction of 30%, stir for 1.8 h, and filter to obtain pretreated powder;

[0090] Q2. By weight, take 0.45 parts of phosphoric acid and add it to 18 parts of ethanol, then add 0.55 parts of nano magnesium fluoride, and continue stirring for 14 minutes to obtain the modified solution;

[0091] Q3. Add the pretreated powder of Q1 to the modified liquid of Q2, stir for 1.8h, filter, put into a muffle furnace, calcine at 380℃ for 0.8h, cool to room temperature, and obtain modified Si3N4 powder.

[0092] Then, the whisker composite porous silicon micropowder is prepared, including the following steps:

[0093] S1. By weight, take 10 parts of silica powder and 0.21 parts of refined naphthalene, add 45 parts of diethyl ether, stir evenly, heat and evaporate, recover the diethyl ether in the evaporator for reuse, and obtain the remaining solid.

[0094] S2. By weight, the solid in S1 is mixed with 9 parts of modified Si3N4 powder to obtain solid mixture B. 14 parts of solid mixture B are added to 14 parts of polyvinyl alcohol aqueous solution with a mass fraction of 1% and wet ball milling is performed to obtain a mixed slurry.

[0095] S3. Place the above mixed slurry in a drying oven to dry, then shape and sinter it at a sintering temperature of 1540℃ for 1 hour. After cooling to room temperature, crush it and pass it through a 110-mesh sieve to obtain whisker composite porous silicon micro powder.

[0096] A method for preparing medium-entropy low-dielectric microwave ceramics includes the following steps:

[0097] Step 1: Mix MgO, CoO and ZnO powders in equimolar ratio to obtain a solid mixture Z. Grind the mixture Z in a ball mill with deionized water as the grinding medium using a wet grinding method until the particle size is less than 10 micrometers. Dry the mixture to obtain a mixed powder.

[0098] Step 2: By weight, add 0.25 parts citric acid and 1.8 parts ethylene glycol to 80 parts of the mixed aqueous solution, heat to 75°C, and stir for 0.9 h to obtain mixed solution C. The solutes in the mixed aqueous solution include MgCl2, CoCl2 and ZnCl2, and the concentrations of MgCl2, CoCl2 and ZnCl2 are all 0.28 mol / L.

[0099] Step 3: Weigh 5 parts by weight of the whisker composite porous silica powder and add it to the mixture C from Step 2. Stir for 35 min, adjust the pH to 10 with sodium bicarbonate, continue stirring for 1.8 h, heat to 75 °C, then add 3.5 parts of the mixed powder obtained in Step 1, stir for 18 min, and then filter, press into shape, and sinter. After sintering, a medium-entropy low-dielectric microwave ceramic is obtained. The sintering process involves heating to 1450 °C at a rate of 9 °C / min and then holding at that temperature for 5.5 hours to obtain the medium-entropy low-dielectric microwave ceramic.

[0100] Comparative Example 1

[0101] Unlike Example 1, in the preparation of the medium-entropy low-dielectric microwave ceramic, the modified Si3N4 powder was replaced with the pretreated powder dried material prepared in this comparative example.

[0102] A medium-entropy low-dielectric microwave ceramic is composed of ternary silicate A2SiO4 and whisker composite porous silicon micropowder, wherein A is composed of equimolar elements Mg, Co and Zn.

[0103] First, a pretreated powder dry product is prepared. The method for preparing the pretreated powder dry product includes the following steps:

[0104] Q1. By weight, add 5 parts of α-Si3N4 powder to 50 parts of sodium polyacrylate aqueous solution with a mass concentration of 3%, heat to 50°C, stir for 20 min, then add 0.3 parts of hydrogen peroxide solution with a mass fraction of 30% dropwise at a uniform rate, stir for 1 h, and filter to obtain the pretreated powder;

[0105] Q2. Place the pretreated powder prepared in Q1 into a muffle furnace and calcine it at 350°C for 0.7 h. Then cool it to room temperature to obtain the dried pretreated powder.

[0106] Then, the whisker composite porous silicon micropowder is prepared, including the following steps:

[0107] S1. By weight, take 10 parts of silica powder and 0.20 parts of refined naphthalene, add 40 parts of diethyl ether, stir evenly, heat and evaporate, recover the diethyl ether in the evaporator for reuse, and obtain the remaining solid.

[0108] S2. By weight, the solids in S1 are mixed with 8 parts of pretreated powder dried material to obtain solid mixture B. 10 parts of solid mixture B are added to 10 parts of polyvinyl alcohol aqueous solution with a mass fraction of 1% and wet ball milling is performed to obtain a mixed slurry.

[0109] S3. Place the above mixed slurry in a drying oven to dry, then shape and sinter it at a temperature of 1500℃ for 1 hour. After cooling to room temperature, crush it and pass it through a 100-mesh sieve to obtain whisker composite porous silicon micro powder.

[0110] A method for preparing medium-entropy low-dielectric microwave ceramics includes the following steps:

[0111] Step 1: Mix MgO, CoO and ZnO powders in equimolar ratio to obtain a solid mixture Z. Grind the mixture Z in a ball mill with deionized water as the grinding medium using a wet grinding method until the particle size is less than 10 micrometers. Dry the mixture to obtain a mixed powder.

[0112] Step 2: By weight, add 0.2 parts citric acid and 1.5 parts ethylene glycol to 100 parts of the mixed aqueous solution, heat to 70°C, and stir for 0.5 h to obtain mixed solution C. The solutes in the mixed aqueous solution include MgCl2, CoCl2 and ZnCl2, and the concentrations of MgCl2, CoCl2 and ZnCl2 are all 0.25 mol / L.

[0113] Step 3: Weigh 5 parts by weight of the whisker composite porous silica powder and add it to the mixture C from Step 2. Stir for 30 minutes, adjust the pH to 9 with sodium bicarbonate, continue stirring for 1 hour, heat to 70°C, then add 3 parts of the mixed powder obtained in Step 1, stir for 15 minutes, and then filter, press into shape, and sinter. After sintering, a medium-entropy low-dielectric microwave ceramic is obtained. The sintering process involves heating to 1400°C at a rate of 5°C / min and then holding at that temperature for 4 hours to obtain the medium-entropy low-dielectric microwave ceramic.

[0114] Comparative Example 2

[0115] Unlike Example 1, the preparation method of whisker composite porous silica powder does not include refined naphthalene.

[0116] A medium-entropy low-dielectric microwave ceramic is composed of ternary silicate A2SiO4 and whisker composite porous silicon micropowder, wherein A is composed of equimolar elements Mg, Co and Zn.

[0117] First, modified Si3N4 powder is prepared. The method for preparing modified Si3N4 powder includes the following steps:

[0118] Q1. By weight, add 5 parts of α-Si3N4 powder to 50 parts of sodium polyacrylate aqueous solution with a mass concentration of 3%, heat to 50°C, stir for 20 min, then add 0.3 parts of hydrogen peroxide solution with a mass fraction of 30% dropwise at a uniform rate, stir for 1 h, and filter to obtain the pretreated powder;

[0119] Q2. By weight, take 0.4 parts of phosphoric acid and add it to 15 parts of ethanol, then add 0.5 parts of nano magnesium fluoride, and continue stirring for 10 minutes to obtain the modified solution;

[0120] Q3. Add the pretreated powder of Q1 to the modified liquid of Q2, stir for 1.5h, filter, put into a muffle furnace, calcine at 350℃ for 0.7h, cool to room temperature, and obtain modified Si3N4 powder.

[0121] Then, the whisker composite porous silicon micropowder is prepared, including the following steps:

[0122] S1. By weight, add 10 parts of silica powder to 40 parts of diethyl ether, stir evenly, then heat and evaporate, recover the diethyl ether in the evaporator for reuse, and obtain a solid product in the remainder;

[0123] S2. By weight, the solid in S1 is mixed with 8 parts of modified Si3N4 powder to obtain solid mixture B. 10 parts of solid mixture B are added to 10 parts of polyvinyl alcohol aqueous solution with a mass fraction of 1% and wet ball milling is performed to obtain a mixed slurry.

[0124] S3. Place the above mixed slurry in a drying oven to dry, then shape and sinter it at a temperature of 1500℃ for 1 hour. After cooling to room temperature, crush it and pass it through a 100-mesh sieve to obtain whisker composite porous silicon micro powder.

[0125] A method for preparing medium-entropy low-dielectric microwave ceramics includes the following steps:

[0126] Step 1: Mix MgO, CoO and ZnO powders in equimolar ratio to obtain a solid mixture Z. Grind the mixture Z in a ball mill with deionized water as the grinding medium using a wet grinding method until the particle size is less than 10 micrometers. Dry the mixture to obtain a mixed powder.

[0127] Step 2: By weight, add 0.2 parts citric acid and 1.5 parts ethylene glycol to 100 parts of the mixed aqueous solution, heat to 70°C, and stir for 0.5 h to obtain mixed solution C. The solutes in the mixed aqueous solution include MgCl2, CoCl2 and ZnCl2, and the concentrations of MgCl2, CoCl2 and ZnCl2 are all 0.25 mol / L.

[0128] Step 3: Weigh 5 parts by weight of the whisker composite porous silica powder and add it to the mixture C from Step 2. Stir for 30 minutes, adjust the pH to 9 with sodium bicarbonate, continue stirring for 1 hour, heat to 70°C, then add 3 parts of the mixed powder obtained in Step 1, stir for 15 minutes, and then filter, press into shape, and sinter. After sintering, a medium-entropy low-dielectric microwave ceramic is obtained. The sintering process involves heating to 1400°C at a rate of 5°C / min and then holding at that temperature for 4 hours to obtain the medium-entropy low-dielectric microwave ceramic.

[0129] Comparative Example 3

[0130] Unlike Example 1, in the preparation of medium-entropy low-dielectric microwave ceramics, modified Si3N4 powder is replaced with pretreated dried powder, and refined naphthalene is not added in the preparation method of whisker composite porous silica micropowder.

[0131] A medium-entropy low-dielectric microwave ceramic is composed of ternary silicate A2SiO4 and whisker composite porous silicon micropowder, wherein A is composed of equimolar elements Mg, Co and Zn.

[0132] First, a pretreated powder dry product is prepared. The method for preparing the pretreated powder dry product includes the following steps:

[0133] Q1. By weight, add 5 parts of α-Si3N4 powder to 50 parts of sodium polyacrylate aqueous solution with a mass concentration of 3%, heat to 50°C, stir for 20 min, then add 0.3 parts of hydrogen peroxide solution with a mass fraction of 30% dropwise at a uniform rate, stir for 1 h, and filter to obtain the pretreated powder;

[0134] Q2. Place the pretreated powder prepared in Q1 into a muffle furnace and calcine it at 350°C for 0.7 h. Then cool it to room temperature to obtain the dried pretreated powder.

[0135] Then, the whisker composite porous silicon micropowder is prepared, including the following steps:

[0136] S1. By weight, add 10 parts of silica powder to 40 parts of diethyl ether, stir evenly, heat and evaporate, recover the diethyl ether in the evaporator for reuse, and obtain the remaining solid.

[0137] S2. By weight, the solids in S1 are mixed with 8 parts of pretreated powder dried material to obtain solid mixture B. 10 parts of solid mixture B are added to 10 parts of polyvinyl alcohol aqueous solution with a mass fraction of 1% and wet ball milling is performed to obtain a mixed slurry.

[0138] S3. Place the above mixed slurry in a drying oven to dry, then shape and sinter it at a temperature of 1500℃ for 1 hour. After cooling to room temperature, crush it and pass it through a 100-mesh sieve to obtain whisker composite porous silicon micro powder.

[0139] A method for preparing medium-entropy low-dielectric microwave ceramics includes the following steps:

[0140] Step 1: Mix MgO, CoO and ZnO powders in equimolar ratio to obtain a solid mixture Z. Grind the mixture Z in a ball mill with deionized water as the grinding medium using a wet grinding method until the particle size is less than 10 micrometers. Dry the mixture to obtain a mixed powder.

[0141] Step 2: By weight, add 0.2 parts citric acid and 1.5 parts ethylene glycol to 100 parts of the mixed aqueous solution, heat to 70°C, and stir for 0.5 h to obtain mixed solution C. The solutes in the mixed aqueous solution include MgCl2, CoCl2 and ZnCl2, and the concentrations of MgCl2, CoCl2 and ZnCl2 are all 0.25 mol / L.

[0142] Step 3: Weigh 5 parts by weight of the whisker composite porous silica powder and add it to the mixture C from Step 2. Stir for 30 minutes, adjust the pH to 9 with sodium bicarbonate, continue stirring for 1 hour, heat to 70°C, then add 3 parts of the mixed powder obtained in Step 1, stir for 15 minutes, and then filter, press into shape, and sinter. After sintering, a medium-entropy low-dielectric microwave ceramic is obtained. The sintering process involves heating to 1400°C at a rate of 5°C / min and then holding at that temperature for 4 hours to obtain the medium-entropy low-dielectric microwave ceramic.

[0143] Using the medium-entropy low-dielectric microwave ceramics prepared in the embodiments and comparative examples of this invention as samples, the relative permittivity ε of the samples was measured using the Hakki-Collemon dielectric resonator method and an Agilent Anglient 8753ES 40GHz vector network analyzer. r The temperature coefficient of the sample was tested using the temperature chamber method, along with the quality factor Q×f. The results are shown in Table 1.

[0144]

[0145] Table 1

[0146] As can be seen from the data in Table 1 and Examples 1 to 5, the dielectric constant of the medium-entropy microwave ceramics prepared by this invention is between 6.9 and 7.3, and the quality factor is greater than 1.1 × 10⁻⁶. 5 The medium-entropy low-dielectric microwave ceramic prepared in this invention exhibits excellent loss performance and a temperature coefficient of -10±3, demonstrating that it possesses superior comprehensive performance.

[0147] Combining the data from Comparative Example 1 and Example 1, and the corresponding data in Table 1, it can be seen that the dielectric constant of the medium-entropy low-dielectric microwave ceramic prepared in Comparative Example 1 is 7.46, which is significantly higher than that of the medium-entropy microwave ceramic prepared in Example 1, resulting in a significant increase in loss. Simultaneously, its quality factor is lower than that of Example 1, and its temperature coefficient decreases to -16 ppm / ℃. This indicates that the addition of nano-magnesium fluoride and phosphoric acid can improve the overall performance of the prepared medium-entropy low-dielectric microwave ceramic.

[0148] In Comparative Example 2, without the addition of refined naphthalene, the dielectric constant of the prepared medium-entropy low-dielectric microwave ceramic was significantly higher than 6.94, at 8.12, and the quality factor decreased to 100700. The loss of the medium-entropy low-dielectric microwave ceramic increased, and the temperature coefficient decreased, indicating that its energy storage performance was unstable. Overall, the performance of the medium-entropy low-dielectric microwave ceramic prepared in Comparative Example 2 was reduced. Compared with Example 1, this demonstrates that the addition of refined naphthalene can improve the overall performance of the prepared medium-entropy low-dielectric microwave ceramic.

[0149] Comparative Example 3, based on Comparative Example 1, did not add refined naphthalene in the preparation of the whisker composite porous silica powder. The dielectric constant of the prepared medium-entropy low-dielectric microwave ceramic was higher than that of Comparative Examples 1 and 2, but the quality factor was lower, and the temperature coefficient was also lower. This indicates that the modified Si3N4 prepared by adding phosphoric acid and nano-magnesium fluoride can have a synergistic effect with the introduction of refined naphthalene, synergistically improving the performance of the prepared whisker composite porous silica powder, thereby improving the overall performance of the prepared medium-entropy low-dielectric microwave ceramic.

[0150] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A medium-entropy low-dielectric microwave ceramic, characterized in that: Its constituent materials include ternary silicate A2SiO4 and whisker composite porous silica powder, wherein A is composed of equimolar elements Mg, Co and Zn; The preparation method of the medium-entropy low-dielectric microwave ceramic includes the following steps: Step 1: Mix MgO, CoO and ZnO powders in equimolar ratio to obtain mixture Z. Grind mixture Z in a ball mill with deionized water as the grinding medium using wet grinding method until the particle size is less than 10 micrometers. Dry the mixture to obtain mixed powder. Step 2: By weight, add 0.1-0.3 parts citric acid and 1-2 parts ethylene glycol to 50-100 parts of the mixed aqueous solution, heat to 60-80℃, and stir for 0.5-1h to obtain mixed solution C. The solutes in the mixed aqueous solution include MgCl2, CoCl2 and ZnCl2, and the concentrations of MgCl2, CoCl2 and ZnCl2 are all 0.2-0.3 mol / L. Step 3: Weigh 5 parts by weight of whisker composite porous silica powder and add it to the mixture C in Step 2. Stir for 20-40 minutes, adjust the pH to 9-10 with sodium bicarbonate, continue stirring for 1-2 hours, heat to 60-80℃, then add 2-4 parts of the mixed powder obtained in Step 1, stir for 10-20 minutes, filter, press into shape, and sinter to obtain medium-entropy low-dielectric microwave ceramic. The method for preparing the whisker composite porous silicon micropowder includes the following steps: S1. By weight, take 10 parts of silica powder and 0.18-0.22 parts of refined naphthalene, add 30-50 parts of diethyl ether, stir evenly, heat and evaporate to obtain a solid. S2. By weight, the solids in S1 are mixed with 6-10 parts of modified Si3N4 powder to obtain solid mixture B. 10-15 parts of solid mixture B are added to 10-15 parts of a 1% polyvinyl alcohol aqueous solution and wet ball milled to obtain a mixed slurry. S3. Place the mixed slurry in S2 in a drying oven to dry, shape and sinter, then cool to room temperature, crush, and pass through an 80-120 mesh sieve to obtain whisker composite porous silicon micro powder; The method for preparing the modified Si3N4 powder includes the following steps: Q1. By weight, add 5 parts of α-Si3N4 powder to 40-60 parts of sodium polyacrylate aqueous solution with a mass concentration of 2-4%, heat to 40-60℃, stir for 10-30 min, then add 0.2-0.4 parts of hydrogen peroxide solution with a mass fraction of 30%, stir for 1-2 h, and filter to obtain pretreated powder; Q2. By weight, take 0.3-0.5 parts of phosphoric acid and add it to 10-20 parts of ethanol, then add 0.4-0.6 parts of nano magnesium fluoride, and continue stirring for 5-15 minutes to obtain the modified solution; Q3. Add the pretreated powder of Q1 to the modification solution of Q2, stir for 1-2 hours, filter, place in a muffle furnace, calcine, and cool to room temperature to obtain modified Si3N4 powder.

2. The medium-entropy low-dielectric microwave ceramic according to claim 1, characterized in that: The calcination temperature of Q3 is 300-400℃, and the calcination time is 0.5-1h.

3. The medium-entropy low-dielectric microwave ceramic according to claim 1, characterized in that: The sintering temperature in S3 is 1450-1550℃, and the sintering time is 1-2h.

4. The medium-entropy low-dielectric microwave ceramic according to claim 1, characterized in that: The sintering temperature in step 3 is 1300-1500℃, and the sintering time is 2-6h.

5. The medium-entropy low-dielectric microwave ceramic according to claim 1, characterized in that: The heating rate in step 3 is 1–10 °C / min.

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