Method for improving frequency temperature stability of microwave dielectric ceramic

Abstract

The invention discloses a method for improving frequency temperature stability of microwave dielectric ceramic. According to the method, copper molybdate (CuMoO4) is taken as a base material, and through an entropy engineering strategy, two or more metal ions with the radius and coordination number similar to those of Cu < 2 + > ions are introduced into the A site of CuMoO4 for multi-component co-doping. The invention aims to increase the configuration entropy of a system, optimize the lattice stability of the material and effectively inhibit lattice parameter fluctuation caused by temperature change, so that the resonant frequency temperature coefficient of the copper molybdate-based microwave dielectric ceramic material is optimized, and meanwhile, the excellent dielectric constant and high quality factor of the copper molybdate-based microwave dielectric ceramic material are maintained. The prepared material has a low dielectric constant, a high quality factor and excellent frequency temperature coefficient stability, is expected to be used as an ideal substrate material of low temperature co-fired ceramic (LTCC), and has a wide application prospect in the fields of integrated circuits, radio frequency components, electronic packaging and the like.

Description

Technical Field

[0001] This invention relates to the field of microwave dielectric ceramic material preparation technology, and in particular to a method for improving the frequency temperature stability of microwave dielectric ceramics. Background Technology

[0002] Microwave dielectric ceramics are widely used in microwave communication. Electronic components and functional modules in microwave communication systems, such as resonators, filters, dielectric antennas, and dielectric waveguides, are important parts of the communication system. In recent years, 5G+IoT (Internet of Things) has gradually become the trend in civilian wireless communication development, and the era of true interconnection of everything has arrived. High performance, miniaturization, integration, and low cost of devices have always been the goals pursued by communication systems. To meet this demand, low-temperature co-fired ceramic (LTCC) technology has become the mainstream technology for passive integrated packaging.

[0003] Low-temperature co-fired ceramics (LTCC) are currently an ideal technology for achieving miniaturization, integration, lightweighting, and multifunctionality of electronic devices. LTCC is made by creating green ceramic tapes from low-temperature sintered ceramic powder, then fabricating circuit patterns on these tapes through processes such as drilling, slip casting, and printing. Passive components are then embedded in multilayer ceramic substrates and stacked together. The internal and external electrodes can be made of high-conductivity conductors such as silver, copper, and gold. Sintering is carried out at temperatures below 900°C to create a three-dimensional circuit substrate, which can further miniaturize and increase the density of circuits, making it particularly suitable for high-frequency communication components. The LTCC substrate material should have a low dielectric constant (ε). r <10), quality factor (Q×f≥5000GHz) and near-zero resonant frequency temperature coefficient (τ) f ~0).

[0004] Copper molybdate (CuMoO4) microwave dielectric ceramics have attracted much attention due to their excellent dielectric properties, but in practical applications, their temperature coefficient of resonant frequency (τ) is a concern. f The τ value is typically too large, limiting its application over a wide temperature range. In existing technologies, to reduce the τ value of microwave dielectric ceramics... f Common methods used include single doping and solid solution formation. However, these methods often face challenges such as limited controllability, easy introduction of a second phase, or difficulties in optimizing τ. f This presents the challenge of sacrificing other dielectric properties (such as dielectric constant and quality factor). In recent years, entropy engineering, as an emerging materials design concept, has emerged. By increasing the compositional complexity and configurational entropy of a material system, it can effectively control the crystal structure stability, thermal expansion behavior, and defect distribution of the material, thus providing a new approach to optimizing the frequency-temperature characteristics of microwave dielectric ceramics. This invention innovatively introduces an entropy engineering strategy for copper molybdate-based microwave dielectric ceramics, aiming to achieve τ... f Precise regulation. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing materials and provide a method to improve the frequency temperature stability of microwave dielectric ceramics. By performing multi-element high-entropy co-doping at the A-site of copper molybdate-based microwave dielectric ceramics, the crystal structure stability is optimized, and the thermal expansion coefficient is reduced, thereby significantly reducing the temperature coefficient of the resonant frequency to near zero, while maintaining or improving its excellent dielectric properties such as dielectric constant and quality factor.

[0006] This invention provides a method for improving the frequency temperature stability of microwave dielectric ceramics. The preparation method of the copper molybdate-based microwave dielectric ceramic material includes the following steps: (1) Precursor formulation and mixing: according to (Cu 1-x-y-z-w Zn x Mg y Co z Ca w The stoichiometric ratio of MoO4 is 0.5≤x+y+z+w≤0.8. Weigh out at least two of CuO, MoO3, ZnO, MgO, CoCO3 and CaCO3 as precursor raw materials, and ball mill them once to obtain a uniformly mixed powder. (2) Pre-firing treatment: The mixed powder is dried, ground and then pre-firing to obtain pre-firing blocks; (3) Secondary grinding and refining: The pre-burnt block material is ground, sieved, ball-milled twice and dried to obtain fine powder; (4) Granulation and molding: The fine powder is mixed with the binder and granulated; (5) Press molding: Press the granulated powder into a green body; (6) Sintering densification: The green blank is subjected to debinding treatment and then high-temperature sintering to obtain the microwave dielectric ceramic material.

[0007] Preferably, the conditions for the first and second ball milling in steps (1) and (3) are as follows: the weight ratio of the powder, zirconia balls and anhydrous ethanol is 1:(2.5~4):5, and the ball milling time is 10~12h.

[0008] Preferably, the drying temperature in steps (2) and (3) is 60-80℃ and the drying time is 12h; the pre-firing temperature is 500-600℃ and the heat preservation time is 8-12h.

[0009] Preferably, the adhesive used in step (6) is polyvinyl alcohol (PVA), and the amount used is 15~25wt%.

[0010] Preferably, the pressing pressure in step (7) is 6~8MPa and the holding time is 1~3min.

[0011] Preferably, in step (8), the debinding process is held at 550°C for 180 min with a heating rate of 0.5~2°C / min; the high-temperature sintering temperature is 750~850°C with a heating rate of 2~5°C / min, and the process is followed by furnace cooling after holding for 8~12 h.

[0012] This invention utilizes the entropy engineering method described above to control the resonant frequency temperature coefficient of microwave dielectric ceramic materials. The resulting copper molybdate-based microwave dielectric ceramic material exhibits a low dielectric constant, effectively adjusting the frequency temperature coefficient while maintaining its excellent dielectric properties. Ultimately, the copper molybdate microwave dielectric ceramic material achieves a dielectric constant of 7.5–8.5, a Q×f value of 49,000–56,000 GHz, and a frequency temperature coefficient of -10 to -35 ppm / ℃.

[0013] This invention employs an entropy engineering strategy to introduce multi-element high-entropy co-doping into a copper molybdate matrix. This effectively increases the lattice configuration entropy, enhances the stability of the crystal structure to temperature changes, and thus significantly reduces the temperature coefficient of the resonant frequency (τ). f The absolute value of τ is made close to zero. Compared with the prior art, the present invention achieves superior τ. f While maintaining the desired properties, this method also preserves high dielectric constant and quality factor. The resonant frequency temperature coefficient of the copper molybdate-based microwave dielectric ceramic material prepared by this method is effectively optimized from -36 ppm / ℃ to -10 to -15 ppm / ℃, with a dielectric constant of 7.5 to 8.5 and a quality factor of 49,000 to 56,000 GHz. This enables the application of copper molybdate ceramic materials in the fabrication of components for high-performance, miniaturized, and integrated electronic systems; and demonstrates that entropy modulation strategies can effectively reduce the frequency temperature coefficient of materials.

[0014] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the scope of the invention.

[0015] The above description of the invention is not intended to describe every disclosed embodiment or implementation of the invention. Instead, the following description provides more specific examples of exemplary embodiments. Throughout this application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive. Attached Figure Description

[0016] The features, advantages and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0017] Figure 1 The X-ray diffraction patterns are of the copper molybdate-based microwave dielectric ceramic materials prepared in Examples 1-4.

[0018] Figure 2 The image shows the surface microstructure of the copper molybdate-based microwave dielectric ceramic material prepared in Example 1.

[0019] Figure 3 The image shows the surface microstructure of the copper molybdate-based microwave dielectric ceramic material prepared in Example 2.

[0020] Figure 4 The image shows the surface microstructure of the copper molybdate-based microwave dielectric ceramic material prepared in Example 3.

[0021] Figure 5 The image shows the surface microstructure of the copper molybdate-based microwave dielectric ceramic material prepared in Example 4. Detailed Implementation

[0022] Example

[0023] The following embodiments will describe the contents disclosed in this invention in more detail. These examples are for illustrative purposes only. In fact, various adjustments and modifications will be apparent to those skilled in the art without departing from the core content disclosed in this application. Unless otherwise stated, all parts, percentages, and ratios mentioned in the following embodiments are based on weight ratios. Furthermore, all chemical reagents used in the embodiments are either commercially available or synthesized using standard methods and are generally ready for use without further processing. In addition, all instruments and equipment involved in the embodiments are commercially available products.

[0024] Example 1

[0025] The copper molybdate-based microwave dielectric ceramic material prepared in this embodiment includes the following steps: (1) According to (Cu 1-x-y-z-w Zn x Mg y Co z Ca w The stoichiometric ratio of CuO, ZnO, and MoO3 was determined by weighing CuO, ZnO, and MoO3, where 0.5 ≤ x + y + z + w ≤ 0.8. The raw materials were then used for precursor preparation and mixing, followed by pre-calcination to obtain (CuO) 0.5 Zn 0.5 MoO4 pre-fired briquettes; of which (Cu 0.5 Zn 0.5The pre-calcination temperature of MoO4 is 550℃, and the holding time is 12 hours. (2) The (Cu) 0.5 Zn 0.5 The pre-calcined MoO4 blocks were subjected to secondary grinding and refinement. The weight ratio of the powder, zirconium oxide balls, and anhydrous ethanol was 1:3:5, and the ball milling time was 12 hours. The mixture was then dried at 80°C to obtain (Cu... 0.5 Zn 0.5 MoO4 fine powder; (3) Add the binder polyvinyl alcohol (PVA) to the fine powder and granulate it, wherein the amount of binder is 25wt%; after sieving, small granular powder is obtained; (4) The small granular powder is placed in a mold, pressed and shaped at 8MPa, and held under pressure for 1 minute to obtain a green block; (5) The debinding treatment was carried out at 550℃ for 180 min with a heating rate of 1℃ / min; the high-temperature sintering temperature was 750℃ with a heating rate of 3℃ / min, and the temperature was maintained for 12 h before being cooled in the furnace to obtain (Cu 0.5 Zn 0.5 MoO4 ceramics.

[0026] The XRD pattern of the copper molybdate-based microwave dielectric ceramic material prepared in this embodiment is as follows: Figure 1 As shown, no obvious secondary phases were formed except for the CuMoO4 phase. The surface morphology SEM images of the prepared copper molybdate-based microwave dielectric ceramic material are shown below. Figure 2 As shown, the ceramic has large, irregularly shaped grains and a low degree of densification. The copper molybdate microwave dielectric ceramic has a dielectric constant of 7.78, a Q×f value of 54,946 GHz, and a frequency temperature coefficient of -32.01 ppm / ℃.

[0027] Example 2

[0028] The copper molybdate-based microwave dielectric ceramic material prepared in this embodiment includes the following steps: (1) According to (Cu 1-x-y-z-w Zn x Mg y Co z Ca w The stoichiometric ratio of CuO, ZnO, MgO, and MoO3 was determined by weighing CuO, ZnO, MgO, and MoO3, where 0.5 ≤ x + y + z + w ≤ 0.8. The raw materials were then used for precursor preparation and mixing, followed by pre-calcination to obtain (CuO) 1 / 3 Zn 1 / 3Mg 1 / 3 MoO4 pre-fired briquettes; of which (Cu 1 / 3 Zn 1 / 3 Mg 1 / 3The pre-calcination temperature of MoO4 is 550℃, and the holding time is 12 hours. (2) The (Cu) 1 / 3 Zn 1 / 3 Mg 1 / 3 The pre-calcined MoO4 blocks were subjected to secondary grinding and refinement. The weight ratio of the powder, zirconium oxide balls, and anhydrous ethanol was 1:3:5, and the ball milling time was 12 hours. The mixture was then dried at 80°C to obtain (Cu... 1 / 3 Zn 1 / 3Mg 1 / 3 MoO4 fine powder; (3) Add the binder polyvinyl alcohol (PVA) to the fine powder and granulate it, wherein the amount of binder is 25wt%; after sieving, small granular powder is obtained; (4) The small granular powder is placed in a mold, pressed and shaped at 8MPa to obtain a green block, and then held under pressure for 1 minute to obtain a green block. (5) The debinding treatment was carried out at 550℃ for 180 min with a heating rate of 1℃ / min; the high-temperature sintering temperature was 775℃ with a heating rate of 3℃ / min, and the mixture was held at 550℃ for 12 h before being cooled in the furnace to obtain (Cu 1 / 3 Zn 1 / 3 Mg 1 / 3 MoO4 ceramics.

[0029] The XRD pattern of the copper molybdate-based microwave dielectric ceramic material prepared in this embodiment is as follows: Figure 1 As shown, no obvious secondary phases were formed except for the CuMoO4 phase. The surface morphology SEM images of the prepared copper molybdate-based microwave dielectric ceramic material are shown below. Figure 3 As shown, the ceramic grain size is significantly increased, the shape is more uniform, and the porosity is increased, affecting the particle growth and densification process, thus reducing the overall density of the ceramic. The copper molybdate microwave dielectric ceramic has a dielectric constant of 7.55, a Q×f value of 51,202 GHz, and a frequency temperature coefficient of -23.32 ppm / ℃.

[0030] Example 3

[0031] The copper molybdate-based microwave dielectric ceramic material prepared in this embodiment includes the following steps: (1) According to (Cu 1-x-y-z-w Zn x Mg y Co z Ca w The stoichiometric ratio of CuO, ZnO, MgO, CoCO3, and MoO3 was weighed out, where 0.5 ≤ x + y + z + w ≤ 0.8. The raw materials were then used for precursor preparation and mixing, followed by pre-calcination to obtain (CuO) 0.25 Zn0.25 Mg 0.25 Co 0.25 MoO4 pre-fired briquettes; of which (Cu 0.25 Zn 0.25 Mg 0.25 Co 0.25 The pre-calcination temperature of MoO4 is 550℃, and the holding time is 12 hours. (2) The (Cu) 0.25 Zn 0.25 Mg 0.25 Co 0.25 The pre-calcined MoO4 blocks were subjected to secondary grinding and refinement. The weight ratio of the powder, zirconium oxide balls, and anhydrous ethanol was 1:3:5, and the ball milling time was 12 hours. The mixture was then dried at 80°C to obtain (Cu... 0.25 Zn 0.25 Mg 0.25 Co 0.25 MoO4 fine powder; (3) Add the binder polyvinyl alcohol (PVA) to the fine powder and granulate it, wherein the amount of binder is 25wt%; after sieving, small granular powder is obtained; (4) The small granular powder is placed in a mold and pressed into shape at 8MPa. After holding the pressure for 1 minute, a green block is obtained. (5) The debinding treatment was carried out at 550℃ for 180 min with a heating rate of 1℃ / min; the high-temperature sintering temperature was 775℃ with a heating rate of 3℃ / min, and the mixture was held at 550℃ for 12 h before being cooled in the furnace to obtain (Cu 0.25 Zn 0.25 Mg 0.25 Co 0.25 MoO4 ceramics.

[0032] The XRD pattern of the copper molybdate-based microwave dielectric ceramic material prepared in this embodiment is as follows: Figure 1 As shown, no obvious secondary phases were formed except for the CuMoO4 phase. The surface morphology SEM images of the prepared copper molybdate-based microwave dielectric ceramic material are shown below. Figure 4 As shown, the ceramic grains become larger and more uniform, with clearer boundaries, further improving the material density and grain arrangement regularity. Simultaneously, the porosity is significantly reduced, the particle density is higher, and the overall density of the ceramic is increased. The copper molybdate microwave dielectric ceramic has a dielectric constant of 8.1, a Q×f value of up to 55,460 GHz, and a frequency temperature coefficient of -10.88 ppm / ℃.

[0033] Example 4

[0034] The copper molybdate-based microwave dielectric ceramic material prepared in this embodiment includes the following steps: (1) According to (Cu1-x-y-z-w Zn x Mg y Co z Ca w The stoichiometric ratio of CuO, ZnO, MgO, CoCO3, CoCO3, and MoO3 was weighed out, where 0.5 ≤ x + y + z + w ≤ 0.8. The raw materials were then used for precursor preparation and mixing, followed by pre-calcination to obtain (CuO) 0.2 Zn 0.2 Mg 0.2 Co 0.2 Ca 0.2 MoO4 pre-fired briquettes; of which (Cu 0.2 Zn 0.2 Mg 0.2 Co 0.2 Ca 0.2 The pre-calcination temperature of MoO4 is 550℃, and the holding time is 12 hours. (2) The (Cu) 0.2 Zn 0.2 Mg 0.2 Co 0.2 Ca 0.2 The pre-calcined MoO4 blocks were subjected to secondary grinding and refinement. The weight ratio of the powder, zirconium oxide balls, and anhydrous ethanol was 1:3:5, and the ball milling time was 12 hours. The mixture was then dried at 80°C to obtain (Cu... 0.2 Zn 0.2 Mg 0.2 Co 0.2 Ca 0.2 MoO4 fine powder; (3) Add the binder polyvinyl alcohol (PVA) to the fine powder and granulate it, wherein the amount of binder is 25wt%; after sieving, small granular powder is obtained; (4) The small granular powder is placed in a mold and pressed into shape at 8MPa. After holding the pressure for 1 minute, a green block is obtained. (5) The debinding treatment was carried out at 550℃ for 180 min with a heating rate of 1℃ / min; the high-temperature sintering temperature was 775℃ with a heating rate of 3℃ / min, and the mixture was held at 550℃ for 12 h before being cooled in the furnace to obtain (Cu 0.2 Zn 0.2 Mg 0.2 Co 0.2 Ca 0.2 MoO4 ceramics.

[0035] The XRD pattern of the copper molybdate-based microwave dielectric ceramic material prepared in this embodiment is as follows: Figure 1As shown, in addition to the CuMoO4 phase, a secondary phase CaMoO4 is also formed. The SEM image of the surface morphology of the copper molybdate-based microwave dielectric ceramic material prepared in this embodiment is shown below. Figure 5 As shown, the presence of the second phase CaMoO4 creates a significant volume difference between it and the main phase CuMoO4, which easily leads to defects such as pores at the phase interface. This hinders further densification and may even cause the destruction of some existing dense structures, ultimately resulting in a decrease in the overall density of the ceramic. The copper molybdate microwave dielectric ceramic has a dielectric constant of 7.74, a Q×f value of up to 48,968 GHz, and a frequency temperature coefficient of -14.1 ppm / ℃.

[0036] The foregoing description only details the specific embodiments of this application, but the scope of this application is not limited thereto. Any person skilled in the art can make various equivalent modifications or substitutions based on their understanding of the technical content disclosed in this application. These modifications and substitutions should all be considered to be covered within the protection scope of this application. Therefore, the actual protection scope of this application should be determined by the scope explicitly listed in the claims.

Claims

1. A method for improving the frequency temperature stability of microwave dielectric ceramics, characterized in that, The method is used to prepare copper molybdate-based microwave dielectric ceramic materials. It involves synergistic doping of the CuMoO4 matrix by introducing multiple cations at the A-site to control its resonant frequency temperature coefficient. The method includes the following steps: (1) Precursor formulation and mixing: according to (Cu 1-x-y-z-w Zn x Mg y Co z Ca w The stoichiometric ratio of MoO4 is 0.5≤x+y+z+w≤0.

8. Weigh out at least two of CuO, MoO3, ZnO, MgO, CoCO3 and CaCO3 as precursor raw materials, and ball mill them once to obtain a uniformly mixed powder. (2) Pre-firing treatment: The mixed powder is dried, ground and then pre-firing to obtain pre-firing blocks; (3) Secondary grinding and refining: The pre-burnt block material is ground, sieved, ball-milled twice and dried to obtain fine powder; (4) Granulation and molding: The fine powder is mixed with the binder and granulated; (5) Press molding: Press the granulated powder into a green body to obtain a green body; (6) Sintering densification: The green blank is subjected to debinding treatment and then high-temperature sintering to obtain the microwave dielectric ceramic material.

2. The method according to claim 1, characterized in that, The conditions for the first and second ball milling in steps (1) and (3) are as follows: the weight ratio of the powder, zirconia balls and anhydrous ethanol is 1:(2.5~4):5, and the ball milling time is 10~12h.

3. The method according to claim 1, characterized in that, In steps (2) and (3), the drying temperature is 60-80℃ and the drying time is 12h.

4. The method according to claim 1, characterized in that, In step (2), the preheating temperature is 500-600℃, and the temperature is maintained for 8-12 hours.

5. The method according to claim 1, characterized in that, In step (4), the adhesive is polyvinyl alcohol (PVA), and the amount used is 15~25wt%.

6. The method according to claim 1, characterized in that, The pressing pressure in step (5) is 6~8MPa, and the holding time is 1~3min.

7. The method according to claim 1, characterized in that, In step (6), the glue removal process is held at 550℃ for 180 min with a heating rate of 0.5~2℃ / min; the high-temperature sintering temperature is 750~850℃ with a heating rate of 2~5℃ / min, and the temperature is held for 8~12 h before being cooled with the furnace.

8. A microwave dielectric ceramic material with improved frequency-temperature stability prepared by the method according to any one of claims 1-7, characterized in that, The dielectric constant is 7.5~8.5, the quality factor is 49,000~56,000 GHz, and the temperature coefficient of resonant frequency (τ) is... f The value is -10 to -35 ppm / ℃.

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