A microwave dielectric ceramic material for low ESR capacitors and its preparation method

Abstract

This invention provides a microwave dielectric ceramic material and its preparation method for low ESR capacitors, belonging to the field of ceramic materials technology. By optimizing the composition and ratio of the main material, sintering aid, and modifying additives, this invention achieves both low dielectric constant and low ESR (high Q value) while maintaining an extremely stable temperature coefficient, effectively solving the problem of simultaneously achieving dielectric performance and temperature stability in existing technologies. The microwave dielectric ceramic material provided by this invention can be sintered in a reducing atmosphere and can be used to prepare low ESR, high Q value, and narrow temperature coefficient copper electrode multilayer ceramic capacitors, avoiding silver migration phenomenon in silver-internal electrode MLCCs, effectively improving device reliability and lifespan. It has broad application prospects in high-end fields such as communication base stations, radar, medical equipment, military industry, and AI servers, and the microwave capacitors prepared from it have significant practical value and market application prospects.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, specifically to a microwave dielectric ceramic material for low ESR capacitors and its preparation method. Background Technology

[0002] Radio frequency (RF) microwave capacitors play an indispensable role in solid-state circuits and other critical circuits in the frequency range below 40 GHz, exhibiting excellent high-frequency performance. Their main characteristics include low equivalent series resistance (ESR), high series resonant frequency, and high insulation resistance, making them widely used in various civilian and military fields such as RF power amplifiers, mixers, early warning aircraft, and electronic warfare. However, most existing RF microwave capacitors can only meet low-end requirements, and are almost inadequate in the high-reliability market, especially in the military field where high power and long lifespan are crucial.

[0003] Low-ESR radio frequency microwave multilayer ceramic capacitors (MLCCs) are core components in high-frequency circuits, widely used in high-end fields such as communication base stations, radar, medical equipment, military applications, and artificial intelligence servers. In recent years, their market size has shown a steady growth trend. At low frequencies, dielectric loss Rsd is the main source of ESR; while at high frequencies (greater than 30MHz), capacitor losses mainly originate from metal loss Rsm, which leads to increased ESR and equivalent series inductance (ESL), consequently increasing dielectric loss and decreasing the dielectric's quality factor (Q value). Therefore, selecting electrode materials with low resistivity is crucial. As shown in Table 1, silver (Ag) and copper (Cu) have the lowest resistivity.

[0004] Table 1 Physical properties of existing electrode materials

[0005] Currently, low-ESR RF microwave MLCC products on the market are mainly divided into two categories: silver internal electrode MLCCs and copper internal electrode MLCCs. Silver electrode MLCCs inevitably experience silver migration during use, leading to increased metal loss and ESR, which can severely reduce device reliability or even cause complete failure. In contrast, copper electrode MLCCs avoid these problems. Furthermore, because copper has a higher melting point than silver, the sintering temperature can be increased, and the amount of sintering aids added can be reduced, thereby minimizing the loss of dielectric properties.

[0006] However, the manufacturing process of copper electrode MLCCs involves the co-firing and matching of metallic copper electrodes and ceramic dielectric materials. To suppress the oxidation of metallic copper during high-temperature sintering, MLCC sintering must be carried out in a reducing atmosphere, and the dielectric material used must have good resistance to reduction. However, in existing dielectric materials, oxygen elements easily escape during sintering in a reducing atmosphere, forming a large number of positively charged oxygen vacancies in the crystal lattice. To maintain charge neutrality, electrons are bound around these oxygen vacancies. Under the influence of an external electric field, due to the presence of a large number of mobile electron carriers, the insulation resistivity drops sharply, even becoming semiconductive, resulting in a defect that prevents sintering in a reducing atmosphere and limiting the application of copper electrode MLCCs. Summary of the Invention

[0007] The purpose of this invention is to provide a microwave dielectric ceramic material for low ESR capacitors and a method for its preparation. The microwave dielectric ceramic material provided by this invention can be sintered in a reducing atmosphere, and the prepared microwave dielectric ceramic has a low dielectric constant, low dielectric loss (high Q value) and an extremely stable temperature coefficient.

[0008] To achieve the objectives of this invention, the following technical solutions are provided: A microwave dielectric ceramic material for low ESR capacitors includes a main material, auxiliary materials, sintering aids, and modifying additives: The effective components of the main material include a variety of combinations of CaO, MgO, SrO, TiO2 and SiO2; The auxiliary material is BaZrO3; The sintering aids mentioned are Li2O, BaO, ZnO, B2O3 and SiO2; The modified additive is one or more of MnO2, Dy2O3, Al2O3, Co2O3, Nb2O5 and MgO.

[0009] Preferably, the microwave dielectric ceramic material comprises, by weight, 81-94 parts of main material, 0-9.5 parts of auxiliary material, 5-8 parts of sintering aid, and 0.1-9.5 parts of modifying additive.

[0010] Preferably, the effective components of the main material, by molar percentage, include 22.5-27.5% CaO, 22.5-24% MgO, 0-4% SrO, 2-5% TiO2 and 45-48% SiO2.

[0011] Preferably, the preparation method of the main ingredient includes the following steps: According to the effective component ratio of the main material, CaO, MgO, SrO, TiO2 and SiO2 are ground and mixed, and then calcined to obtain the main material; The calcination temperature is 1100~1200℃, and the time is 2~5h.

[0012] Preferably, the sintering aid comprises, by mass percentage, 5-10% Li2O, 40-45% BaO, 8-10% ZnO, 15-20% B2O3 and 25-30% SiO2.

[0013] Preferably, the preparation method of the sintering aid includes the following steps: The sintering aid is obtained by mixing lithium source, boron source, barium source, zinc source and silicon source, followed by melting, cold quenching and grinding. The melting temperature is 1050℃~1150℃, and the melting time is 1~2h.

[0014] Preferably, the modified additives, by mass parts, include 0.1~0.5 parts of MnO2, 0~1 parts of Dy2O3, 0~5 parts of Al2O3, 0~0.5 parts of Co2O3, 0~1 parts of Nb2O5, and 0~1.5 parts of MgO.

[0015] The present invention also provides a method for preparing the microwave dielectric ceramic material for low ESR capacitors as described in the above technical solution, comprising the following steps: The main material, auxiliary material, sintering aid, and modifying additives are ground, mixed, and refined to obtain the microwave dielectric ceramic material for low ESR capacitors.

[0016] Preferably, the grinding, mixing, and refining process further includes sintering; the sintering is carried out in air and / or a reducing atmosphere.

[0017] Preferably, the sintering temperature is 950~1100℃ and the sintering time is 1~3h.

[0018] This invention provides a microwave dielectric ceramic material for low ESR capacitors, comprising a main material, auxiliary materials, sintering aids, and modifying additives: the effective components of the main material include a combination of CaO, MgO, SrO, TiO2, and SiO2; the auxiliary material is BaZrO3; the sintering aids are Li2O, BaO, ZnO, B2O3, and SiO2; and the modifying additives are one or more of MnO2, Dy2O3, Al2O3, Co2O3, Nb2O5, and MgO. The microwave dielectric ceramic material of this invention uses a calcium-magnesium-strontium-titanium-silicon material system as its main component, exhibiting a low dielectric constant, low ESR, and a small capacity temperature coefficient. The sintering aids used not only effectively cool the main component during sintering but also do not deteriorate the dielectric properties of the material during sintering in a reducing atmosphere (the dielectric constant of the sintering aids in this invention is approximately 6, and the temperature coefficient is approximately +20 ppm / ℃). The addition of auxiliary materials in this invention improves the structural structure of the microwave dielectric ceramic material (inhibiting abnormal grain growth), enhances mechanical strength, and inhibits titanium ion reduction, while simultaneously matching the sintering aids to adjust its dielectric constant and improve the temperature coefficient. Based on this, doping with Si in the main component... 4+ Ti 4+ Low-valence ions (Mn) with similar coordination numbers and ionic radii 2+ Ca 2+ Mg 2+ Y 3+ Dy 3+ (etc.), can effectively suppress the concentration of free electrons, improve the reduction resistance of such materials, and refine the grains, thereby obtaining dielectric ceramic materials with good microwave performance.

[0019] Furthermore, by optimizing the composition and ratio of the main material, sintering aid, and modifying additives, this invention achieves low dielectric constant and low ESR (high Q value) while maintaining an extremely stable temperature coefficient, effectively solving the problem of simultaneously achieving dielectric performance and temperature stability in existing technologies. The microwave dielectric ceramic material provided by this invention can be sintered in a reducing atmosphere and can be used to prepare low ESR, high Q value, and narrow temperature coefficient copper electrode multilayer ceramic capacitors, avoiding the silver migration phenomenon observed in traditional silver internal electrode MLCCs, effectively improving the reliability and lifespan of the devices. The microwave dielectric ceramic material provided by this invention has broad application prospects in high-end fields such as communication base stations, radar, medical equipment, military industry, and AI servers, and the microwave capacitors prepared from it have significant practical value and market application prospects. Detailed Implementation

[0020] This invention provides a microwave dielectric ceramic material for low ESR capacitors, comprising a main material, auxiliary materials, sintering aids, and modifying additives: The effective components of the main material include a variety of combinations of CaO, MgO, SrO, TiO2 and SiO2; The auxiliary material is BaZrO3; The sintering aids mentioned are Li2O, BaO, ZnO, B2O3 and SiO2; The modified additive is one or more of MnO2, Dy2O3, Al2O3, Co2O3, Nb2O5 and MgO.

[0021] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0022] In this invention, the microwave dielectric ceramic material comprises 81-94 parts by mass, and in specific embodiments, it may be 85, 90, or 93 parts; by molar percentage, the main material comprises 23-27.5% CaO, 22.5-24% MgO, 0-4% SrO, 2-5% TiO2, and 45-18% SiO2, and in specific embodiments, it may be 24-25% CaO, 23-23.5% MgO, 0.5-2% SrO, 3-4% TiO2, and 45-48% SiO2, or 24-25% CaO, 23-23.5% MgO, 3-4% TiO2, and 45-48% SiO2.

[0023] In this invention, the effective component CaO in the main material is provided by Ca carbonate, oxide, or hydroxide; the effective component MgO is provided by Mg carbonate, oxide, or hydroxide; the effective component SrO is provided by Sr carbonate, oxide, or hydroxide; the effective component TiO2 is provided by Ti oxide or hydroxide; and the effective component SiO2 is provided by Si oxide or hydroxide. In specific embodiments, it can be CaCO3, Mg(OH)2, SrCO3, TiO2, and SiO2. The main material of the microwave dielectric ceramic material of this invention adopts a calcium-magnesium-strontium-titanium-silicon material system, which has a low dielectric constant (such as that of formulation ZL-2). e r =9.6), low ESR (dielectric loss <0.1×10⁻⁶). -4 It has a small capacity temperature coefficient (-24.7 to -20.0) ppm / ℃.

[0024] In this invention, the preparation method of the main material includes: grinding and mixing raw materials containing Ca, Mg, Sr, Ti and Si according to the effective component ratio of the main material, and calcining them to obtain the main material; the grinding is ball milling; the calcination temperature is 1100~1200℃ and the time is 2~5h.

[0025] In this invention, the microwave dielectric ceramic material comprises 0 to 9.5 parts by mass of auxiliary material, which in specific embodiments may be 0.5, 1, 3, or 5 parts. The auxiliary material is BaZrO3, prepared by ball milling BaCO3 and ZrO2 in a 1:1 molar ratio, followed by drying, sieving, and calcination at 1150–1250°C for 2–5 hours. The addition of this auxiliary material improves the structural structure of the microwave dielectric ceramic material (inhibiting abnormal grain growth), increases mechanical strength, and inhibits the reduction of titanium ions in the main material, while simultaneously matching sintering aids to adjust its dielectric constant and improve its temperature coefficient.

[0026] In this invention, the microwave dielectric ceramic material includes 5-8 parts of sintering aid, which in specific embodiments may be 5.5, 6, or 7 parts; by mass percentage, the sintering aid includes 5-10% Li₂O, 40-45% BaO, 8-10% ZnO, 15-20% B₂O₃, and 25-30% SiO₂. In this invention, the effective component Li₂O in the sintering aid is provided by Li carbonates, oxides, or hydroxides; the effective component BaO is provided by Ba carbonates, oxides, or hydroxides; the effective component B₂O₃ is provided by B acids, oxides, or hydroxides; and the effective component SiO₂ is provided by Si oxides or hydroxides, which in specific embodiments may be 5 wt% Li₂CO₃, 40 wt% BaCO₃, 10 wt% ZnO, 20 wt% H₃BO₃, and 25 wt% SiO₂. The sintering aid of this invention not only has an effective cooling sintering effect on the main material but also does not deteriorate the dielectric properties of the material during sintering in a reducing atmosphere.

[0027] In this invention, the preparation method of the sintering aid includes: mixing a lithium source, a boron source, a barium source, a zinc source, and a silicon source, followed by melting, quenching, and grinding to obtain the sintering aid; the melting and quenching temperature is 1050℃~1150℃, and the melting time is 1~2 hours; the particle size of the sintering aid after grinding is controlled within D... 50 ≤1.0µm, D 97 ≤3.0µm. Due to the low calcination temperature of the sintering aid, there is a possibility of low-melting-point B and Li volatilization during high-temperature sintering. Furthermore, the sintering process is prone to producing an under-sintered MLCC ceramic body, resulting in insufficient density and a whitish color in some chips after firing. The calcined sintering aid structure is also unstable, containing a large amount of B2O3, which can undergo a complexation reaction with PVB in the binder during MLCC formulation, causing a sharp increase in viscosity, even gelling, leading to slurry failure. This invention prepares the sintering aid through melting and cold quenching, reducing the volatilization of low-melting-point substances during sintering, maintaining product performance consistency, and realizing the feasibility of MLCC and LTCC product manufacturing processes.

[0028] In this invention, the microwave dielectric ceramic material includes 0.1 to 9.5 parts of a modifying additive, which in specific embodiments can be 0.2, 0.5, 1, 3, 3.5, or 5 parts. The modifying additive, by mass parts, includes 0.1 to 0.5 parts of MnO2, 0 to 1 part of Dy2O3, 0 to 5 parts of Al2O3, 0 to 0.5 parts of Co2O3, 0 to 1 part of Nb2O5, and 0 to 1.5 parts of MgO, which in specific embodiments can be 0.3 to 0.4 parts of MnO2, 0.2 to 0.3 parts of Dy2O3, 0.5 to 2 parts of Al2O3, 0.1 to 0.3 parts of Co2O3, 0.2 to 0.5 parts of Nb2O5, and 0.1 to 0.5 parts of MgO. This invention achieves this by doping Si in the main material. 4+ Ti 4+ Low-valence ions (Mn) with similar coordination numbers and ionic radii 2+ Ca 2+ Mg 2+ Co 2+ Y 3+ Dy 3+ (etc.), can effectively suppress the concentration of free electrons, improve the reduction resistance of such materials, and refine the grains, thereby obtaining dielectric materials with good microwave performance.

[0029] The present invention also provides a method for preparing the microwave dielectric ceramic material described in the above technical solution, comprising the following steps: The main material, auxiliary material, sintering aid, and modifying additives are ground, mixed, and refined to obtain the microwave dielectric ceramic material for low ESR capacitors.

[0030] In this invention, the grinding method is ball milling; after grinding, the resulting powder is further granulated; the reagent used for granulation is an ethanol solution of polyvinyl butyral; the mass concentration of polyvinyl butyral is 10-15 wt%; this invention also includes pressing the granulated green body into discs and removing the binder in an air furnace, the temperature of the binder removal is 400-500℃, and the time is 4-6 hours; after grinding, mixing and refining, this invention also includes sintering; the sintering is carried out in air and / or a reducing atmosphere. This invention does not have a special limitation on the reducing atmosphere, and any reducing atmosphere known to those skilled in the art can be used. In a specific embodiment, it can be a nitrogen and / or hydrogen atmosphere; the sintering temperature is 950-1100℃, and in a specific embodiment, it can be 1000 or 1030℃, and the time is 1-3 hours. In this invention, the sintering process includes debinding and heating in a reducing atmosphere, high-temperature holding sintering in a reducing atmosphere, cooling to 800°C in a reducing atmosphere, re-oxidation, and cooling. The re-oxidation is carried out in an oxygen-containing atmosphere with an oxygen content of 10-50 ppm, which can be 20-30 ppm in specific embodiments. The re-oxidation temperature is 700-800°C, which can be 750°C or 780°C in specific embodiments, and the holding time is 1-3 hours. After the re-oxidation, the temperature is cooled to room temperature in a reducing atmosphere. The cooling rate of the sintering temperature to the re-oxidation temperature and the temperature required to cool to room temperature can be 2°C-5°C / min.

[0031] The present invention does not specifically limit the application method of the microwave dielectric ceramic material for low ESR capacitors. In a specific embodiment, the microwave dielectric ceramic material may be subjected to the following steps in sequence: batching, casting, printing, stacking, uniform pressing, cutting, plasticizing, sintering, chamfering, end coating, silvering, and surface treatment. The sintering may be carried out in air and / or a reducing atmosphere.

[0032] To further illustrate the present invention, the microwave dielectric ceramic material for low ESR capacitors and its preparation method provided by the present invention are described in detail below with reference to embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0033] Example 1 1) Weigh out CaCO3, Mg(OH)2, SrCO3, TiO2 and SiO2 according to the main material formula in Table 2, add deionized water and zirconium oxide grinding media, and mix according to the weight ratio m 料 :m 水 :m 球 After ball milling the material in a ratio of 1:2:5 for 5 hours, the milled material is dried and sieved, and then calcined at 1100℃~1200℃ for 2~5 hours to obtain the main material, denoted as ZL-1~7.

[0034] Table 2. Molar ratio of main ingredients in the formulation design (mol%)

[0035] 2) Mix BaCO3 and ZrO2 in a 1:1 molar ratio, add deionized water and zirconium oxide grinding media, and adjust the weight ratio by m. 料 :m 水 :m 球 The mixture was ball-milled in a ratio of 1:2:5 for 5 hours. After ball milling, the milled material was dried, sieved, and calcined at 1150℃~1250℃ for 2~5 hours to obtain the by-product (BaZrO3).

[0036] 3) Weigh out 5wt% Li₂CO₃, 40wt% BaCO₃, 10wt% ZnO, 20wt% H₃BO₃, and 25wt% SiO₂, mix the ingredients, pass through a 40-mesh sieve, place in a platinum crucible, heat at 1100℃ for 1 hour to melt, then quench, and ball-mill to obtain the sintering aid (LBZBS). Ball milling controls the particle size D of the sintering aid. 50 ≤1.0µm, D 97 ≤3.0µm.

[0037] 4) Weigh the main materials, auxiliary materials, sintering aids and modifying additives according to the formula and content composition shown in Table 3, and place them in a ball mill jar containing zirconia balls; add deionized water, and then ball mill, dry, grind and sieve to obtain the required ceramic dielectric material; add the sieved mixture to a 10wt% anhydrous ethanol solution of polyvinyl butyral for granulation; press the granulated ceramic green body into a disc green body, remove the binder in an air furnace at 400℃ for 6 h, and then sinter in a reducing atmosphere (H2 / N2 mixed gas) sintering furnace at 1000℃±30℃ for 2~3 h to densify, cool to 700~800℃ at 3℃ / min, keep warm in an air environment with an oxygen content of 10~20ppm for 2 h, and finally cool to room temperature at 3℃ / min to obtain a microwave ceramic disc capacitor sample.

[0038] Examples 1-18 Microwave dielectric ceramic materials were prepared according to the method described in Example 1, with the only difference being that the formulation and content composition of the microwave dielectric ceramic materials are shown in Table 3.

[0039] Table 3 Formulations and content of microwave dielectric ceramic materials in Examples 1-18

[0040] Test case The microwave dielectric ceramic materials obtained in Examples 1-18 were sintered to produce ceramic disc capacitor samples. A portion of the ceramic blanks obtained in step 4) of Examples 1-18 were pressed into discs according to the method described in Example 1. These discs were then subjected to debinding at 400°C for 6 hours in an air furnace, followed by densification at 1000°C ± 30°C for 2-3 hours in an air sintering furnace. Finally, the furnace was cooled to obtain microwave ceramic disc capacitor samples. These samples were then processed into simple disc capacitors through double-sided polishing, diameter and thickness measurement, silver plating, and silver firing. Dielectric loss, insulation resistivity, and capacitance temperature coefficient were tested. Five samples were tested for each example, and the final values ​​are the calculated average values ​​of the samples. The results are shown in Table 4.

[0041] Table 4 Performance of Disc Capacitors Fabricated from Microwave Dielectric Ceramic Materials in Examples 1-18

[0042] Table 4 shows the range for the capacitance temperature coefficient test: -55℃ to 125℃; the capacitance and dielectric loss test conditions: 1MHz, 1V; and the insulation resistance test condition: 500V / 1min.

[0043] As shown in Table 4, the dielectric constant of the disc capacitor samples prepared from the microwave dielectric ceramic material provided by this invention is 6.9~11.5, and the loss is 0.05~2.8×10⁻⁶. -4 Insulation resistivity at room temperature >10 12 Ω·cm can even reach 5×10 13 Ω·cm, the capacity temperature coefficient satisfies C0G within the temperature range of -55℃ to 125℃, i.e., within (0±30)ppm / ℃. Among them, Example 16 has good resistance to reduction, and the performance difference between sintering in air and reducing atmosphere is not significant.

[0044] Application examples Based on the comprehensive performance, the ceramic dielectric material obtained in Example 16 was selected to trial-produce a multilayer ceramic capacitor (imperial size 0805, capacitance 10pF). The inner and outer electrodes of the capacitor were both copper. The capacitor was sintered and densified in a reducing atmosphere at 1000℃±20℃ for 2 hours. After cooling to 700~800℃ and holding in an air environment with an oxygen content of 10~20ppm for 2 hours, the performance of the obtained multilayer ceramic capacitor is shown in Table 5 (ESR test frequency 1GHz).

[0045] Table 5 Electrical properties of multilayer ceramic capacitors

[0046] As shown in Table 5, the prepared multilayer ceramic capacitor has low dielectric loss and low ESR, and a narrower capacitance temperature coefficient (C0F, i.e. (0±15)ppm / ℃), proving that the microwave ceramic dielectric material provided by the present invention can be applied to low ESR and high stability multilayer ceramic capacitors.

[0047] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A microwave dielectric ceramic material for low ESR capacitors, characterized in that, Includes main ingredients, auxiliary ingredients, sintering aids, and modifying additives: The effective components of the main material include a variety of combinations of CaO, MgO, SrO, TiO2 and SiO2; The auxiliary material is BaZrO3; The sintering aids mentioned are Li2O, BaO, ZnO, B2O3 and SiO2; The modified additive is one or more of MnO2, Dy2O3, Al2O3, Co2O3, Nb2O5 and MgO.

2. The microwave dielectric ceramic material according to claim 1, characterized in that, The microwave dielectric ceramic material comprises, by weight, 81-94 parts of main material, 0-9.5 parts of auxiliary material, 5-8 parts of sintering aid, and 0.1-9.5 parts of modifying additive.

3. The microwave dielectric ceramic material according to claim 1, characterized in that, According to molar percentage, the effective components of the main material include 22.5~27.5% CaO, 22.5~24% MgO, 0~4% SrO, 2~5% TiO2 and 45~48% SiO2.

4. The microwave dielectric ceramic material according to claim 3, characterized in that, The preparation method of the main ingredient includes the following steps: According to the effective component ratio of the main material, CaO, MgO, SrO, TiO2 and SiO2 are ground and mixed, and then calcined to obtain the main material; The calcination temperature is 1100~1200℃, and the time is 2~5h.

5. The microwave dielectric ceramic material according to claim 1, characterized in that, The sintering aids, by mass percentage, comprise 5-10% Li2O, 40-45% BaO, 8-10% ZnO, 15-20% B2O3, and 25-30% SiO2.

6. The microwave dielectric ceramic material according to claim 5, characterized in that, The preparation method of the sintering aid includes the following steps: The sintering aid is obtained by mixing lithium source, boron source, barium source, zinc source and silicon source, followed by melting, cold quenching and grinding. The melting temperature is 1050℃~1150℃, and the melting time is 1~2h.

7. The microwave dielectric ceramic material according to claim 1, characterized in that, The modified additives, by mass parts, include 0.1-0.5 parts of MnO2, 0-1 parts of Dy2O3, 0-5 parts of Al2O3, 0-0.5 parts of Co2O3, 0-1 parts of Nb2O5, and 0-1.5 parts of MgO.

8. The method for preparing the microwave dielectric ceramic material for low ESR capacitors according to any one of claims 1 to 7, characterized in that, Includes the following steps: The main material, auxiliary material, sintering aid, and modifying additives are ground, mixed, and refined to obtain the microwave dielectric ceramic material for low ESR capacitors.

9. The preparation method according to claim 8, characterized in that, The grinding, mixing, and refining process further includes sintering; the sintering is carried out in air and / or a reducing atmosphere.

10. The preparation method according to claim 8, characterized in that, The sintering temperature is 950~1100℃ and the time is 1~3h.

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