Modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature and preparation method thereof

Abstract

This invention discloses a modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperatures and its preparation method, belonging to the field of microwave dielectric ceramic production technology. The raw materials for the modified molybdenum-based microwave dielectric ceramic are Al2O3, MoO3, Li2CO3, and V2O5, and its chemical formula is xAl2Mo3O 12 A method for preparing modified molybdenum-based microwave dielectric ceramics using the formula (-(1-x)LiMoVO6), where x = 0.01–0.02, includes the following steps: batching; ball milling, drying, sieving, and pre-firing; batching again, ball milling, drying, and granulation; pressing, debinding, and heat preservation to obtain ultra-low temperature sintered modified molybdenum-based microwave dielectric ceramics. This invention introduces Al2Mo3O into the raw material powder of the LiMoVO6 system. 12 The raw material powders of the system form a two-phase coexistence system, which significantly reduces the temperature stability of the resonant frequency while improving the temperature stability of Al2Mo3O. 12 The sintering temperature of the base ceramic was adjusted, and the system ultimately achieved excellent microwave dielectric properties at a lower sintering temperature (600℃).

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microwave dielectric ceramic production, and particularly relates to a molybdenum-based microwave dielectric ceramic and a preparation method thereof, in particular to a modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature and a preparation method thereof. BACKGROUND

[0002] With the rapid development of the fifth generation mobile communication technology, ceramic dielectric filters will become the preferred solution for 5G base station equipment. Unlike traditional metal cavity filters, in ceramic dielectric filters, electromagnetic waves mainly oscillate in dielectric materials. Due to the excellent microwave dielectric properties of dielectric ceramic materials, such as tunable relative permittivity εr, low dielectric loss tanδ (tanδ = 1 / Q, and the Qxf value reflects the quality factor at a certain resonant frequency), and tunable resonant frequency temperature coefficient τf. Ceramic dielectric filters represent the development direction of high-end radio frequency devices.

[0003] Compared with the 4G communication system, the 5G era adopts large-scale phased array antenna technology, i.e. a multi-channel way to provide higher rates, and the number of channels is increased from 2 channels and 4 channels of 4G to 32 channels and 64 channels of 5G, so the antenna and RRU are combined into AAU. Due to the integration of the antenna, the number of filters required for a set of antenna is greatly increased. Lightweight and small-sized ceramic dielectric filters become an excellent choice for 5G antennas. This requires the ceramic to have high Q value, inexpensive raw materials, and at the same time, the transmission delay and transmission loss of the signal should be considered, and the εr value of the ceramic should also be low (εr≤10). As a new type of three-dimensional integrated packaging interconnection technology, ultra-low temperature cofired ceramic (ULTCC) has the characteristics of small size, light weight, high reliability, good temperature stability, high packaging density, etc., and is widely used in wireless communication electronic components, microwave and millimeter wave substrates, microwave and millimeter wave functional modules, and high-power devices. ULTCC can be sintered at an extremely low temperature of 400℃ to 700℃, making its manufacturing process very energy-saving. On the other hand, low sintering temperature allows a wider range of conductor materials for functionalization, making technology mixing (semiconductor process, polymer-based microcircuit manufacturing) possible.

[0004] Molybdenum-based microwave dielectric ceramic is a new type of glass-free low dielectric constant material system, and the standard product has a chemical formula of Al2Mo3O 12 The sintering temperature of 800℃ of the material is lower than the melting point (961℃) of silver electrode, the material does not need to add glass additives, and is usually a single-phase structure, has the advantages of stable and reliable structure, good repeatability, etc., and can realize low-temperature sintering densification of the ceramic through the low-temperature synthesis characteristics of the phase structure itself. However, pure-phase Al2Mo3O 12The sintering temperature of the ceramic is higher than the melting point (660℃) of the Al electrode, and the temperature stability of the resonant frequency is poor (-59.5ppm / ℃), which cannot be directly applied to the field of ULTCC technology. Therefore, it is necessary to further reduce the sintering temperature of Al2Mo3O 12 It is difficult to simultaneously improve the temperature stability of the resonant frequency of the ceramic sintering temperature.

[0005] Generally speaking, two-phase compounding can regulate the sintering characteristics and microwave dielectric properties, but the effect of regulation still needs to consider the phase composition and micro-morphology in the actual sintering process. From the reported Al2Mo3O 12 From the reported Bi2O3 system, Bi2O3 can effectively reduce the sintering temperature to 650℃, but the τf value is still large, which is -41.2ppm / ℃. Therefore, it is still unknown whether the two-phase compounding technology of increasing Bi2O3 can help the system to achieve excellent resonant frequency temperature stability at a lower temperature. SUMMARY

[0006] The purpose of the present application is to provide a modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature and a preparation method thereof to solve the above problems.

[0007] The present application realizes the above-mentioned purpose by the following technical solutions:

[0008] A modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature, the raw materials of the modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature are Al2O3, MoO3, Li2CO3 and V2O5, and the chemical formula is xAl2Mo3O 12 -(1-x)LiMoVO6, wherein x=0.79-0.80.

[0009] A preparation method of a modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature, comprising the following steps:

[0010] Step 1, first, the raw powder of Al2O3 and MoO3 is dosed according to the chemical formula Al2Mo3O 12 , to obtain the raw powder of the Al2Mo3O 12 system; then, the raw powder of Li2CO3, MoO3 and V2O5 is dosed according to the chemical formula LiMoVO6 to obtain the raw powder of the LiMoVO6 system;

[0011] Step 2, the raw powder of the Al2Mo3O 12 system and the raw powder of the LiMoVO6 system prepared in step 1 are respectively loaded into a ball mill tank, zirconium balls and anhydrous ethanol are selected as the grinding medium for ball milling, and after the ball milling is completed, the mixed slurry is placed in an oven for drying, and then sieved with a 60-100 mesh sieve, and the sieved Al2Mo3O 12The powder of the system is pre-fired in atmospheric atmosphere at 675-700 DEG C for 2-4 hours, and the sieved LiMoVO6 system powder is pre-fired in atmospheric atmosphere at 475-525 DEG C for 2-4 hours;

[0012] Step 3, the Al2Mo3O 12 The pre-fired powder of the system and the pre-fired powder of the LiMoVO6 system are dosed according to the formula xAl2Mo3O 12 (1-x)LiMoVO6, wherein x=0.79-0.80, and then are reloaded into a ball mill tank, zirconium balls and anhydrous ethanol are selected as the grinding medium for ball milling, after the ball milling is completed, the mixed slurry is placed in an oven for drying, and an acrylic acid solution is added to the dried powder as a binder for granulation to prepare ceramic raw material;

[0013] Step 4, the ceramic raw material prepared in step 3 is pressed and formed, and then is degassed at a temperature of 400-450 DEG C for 2-4 hours at a temperature rising rate of 2-5 DEG C / min, and then is heated to 580-600 DEG C at the same rate and is kept for 4-6 hours, to prepare a modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature, which has the formula xAl2Mo3O 12 (1-x)LiMoVO6, x=0.79-0.80.

[0014] Preferably, in step 2, the mass ratio of the raw material powder, zirconium balls and anhydrous ethanol is 1:5:(2-4), and the ball milling time is 4-6 hours; in step 3, the mass ratio of the pre-fired powder, zirconium balls and anhydrous ethanol is 1:5:(1-3), and the ball milling time is 4-6 hours.

[0015] Preferably, the ball milling in steps 2 and 3 is performed by using a planetary ball mill.

[0016] The present application has the following beneficial effects:

[0017] The present application adds Li2CO3 and V2O5 in the raw material, i.e. introduces Al2Mo3O 12 system raw material powder into the LiMoVO6 system, takes LiMoVO6 as the second phase to form a two-phase coexisting system, improves the resonance frequency temperature stability, and greatly reduces the sintering temperature of the Al2Mo3O 12 ceramic, and finally realizes excellent microwave dielectric properties at a lower sintering temperature (600 DEG C): εr is 7.05, tan δ is as low as 1.58*10-3, Q*f value is as high as 8543 GHz (f=13.4 GHz), and τf value is as low as -14.17 ppm / DEG C; the present application fills the gap of the effect of composite ion doping on Al2Mo3O 12The research of the crystal structure and the phase composition of the system is blanked, and the low-temperature sintering characteristics of the system are further improved, the application potential of the system in the field of ULTCC technology is expanded, and the energy saving is promoted. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the XRD pattern of 0.795Al2Mo3O 12 -0.205LiMoVO6 ceramic in the embodiment of the application.

[0019] Figure 2 is the SEM morphology of 0.795Al2Mo3O 12 -0.205LiMoVO6 ceramic. DETAILED DESCRIPTION

[0020] The application will be further described below in combination with the embodiments and the drawings:

[0021] The raw material of the modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature in the application is Al2O3, MoO3, Li2CO3 and V2O5, and the chemical formula is xAl2Mo3O 12 -(1-x)LiMoVO6, wherein x=0.79-0.80.

[0022] The preparation method of the modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature in the application comprises the following steps:

[0023] Step 1, the original powders of Al2O3 and MoO3 are dosed according to the chemical formula Al2Mo3O 12 to obtain the raw material powder of the Al2Mo3O 12 system; the original powders of Li2CO3, MoO3 and V2O5 are dosed according to the chemical formula LiMoVO6 to obtain the raw material powder of the LiMoVO6 system;

[0024] Step 2, the raw material powder of the Al2Mo3O 12 system and the raw material powder of the LiMoVO6 system prepared in step 1 are respectively loaded into a ball mill tank, zirconium balls and anhydrous ethanol are selected as the grinding medium to perform planetary ball milling, the mass ratio of the raw material powder, the zirconium balls and the anhydrous ethanol is 1:5:(2-4), the ball milling time is 4-6 hours, after the ball milling is completed, the mixed slurry is placed in an oven for drying, then the sieved Al2Mo3O 12 system powder is pre-sintered at 675-700 DEG C in an atmospheric atmosphere for 2-4 hours, and the sieved LiMoVO6 system powder is pre-sintered at 475-525 DEG C in an atmospheric atmosphere for 2-4 hours;

[0025] Step 3, the Al2Mo3O 12 The pre-sintered powder of the system and the pre-sintered powder of the LiMoVO6 system are dosed according to the chemical formula xAl2Mo3O 12 (1-x)LiMoVO6, wherein x = 0.79-0.80, and then reloaded into a ball mill tank, zirconium balls and anhydrous ethanol are selected as the grinding medium for planetary ball milling, the total mass ratio of the pre-sintered powder, zirconium balls and anhydrous ethanol is 1:5:(1-3), the ball milling time is 4-6 hours, and after the ball milling is completed, the mixed slurry is placed in an oven for drying, then an acrylic acid solution is added to the dried powder as a binder for granulation to prepare ceramic raw material;

[0026] Step 4, the ceramic raw material prepared in Step 3 is pressed into a shape, then the temperature is raised at a rate of 2℃ / min-5℃ / min to 400℃-450℃ for 2-4 hours for degassing, and then the temperature is raised at the same rate to 580℃-600℃ for 4-6 hours for holding, to prepare a modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature, which has a chemical formula of xAl2Mo3O 12 (1-x)LiMoVO6, x = 0.79-0.80.

[0027] The application will be specifically described below with a preferred embodiment:

[0028] Embodiment:

[0029] The modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature is prepared according to the following steps:

[0030] Step 1, the raw powders of Al2O3 and MoO3 are dosed according to the chemical formula Al2Mo3O 12 to obtain the raw powder of the Al2Mo3O 12 system; the raw powders of Li2CO3, MoO3 and V2O5 are dosed according to the chemical formula LiMoVO6 to obtain the raw powder of the LiMoVO6 system;

[0031] Step 2, the raw powders of the Al2Mo3O 12 system and the LiMoVO6 system dosed in Step 1 are respectively loaded into a ball mill tank, zirconium balls and anhydrous ethanol are selected as the grinding medium for planetary ball milling, the mass ratio of the raw powder, zirconium balls and anhydrous ethanol is 1:5:2, the ball milling time is 6 hours, and after the ball milling is completed, the mixed slurry is placed in an oven for drying, then the sieved Al2Mo3O 12 system powder is pre-sintered at 700℃ in an atmospheric atmosphere for 4 hours, and the sieved LiMoVO6 system powder is pre-sintered at 500℃ in an atmospheric atmosphere for 4 hours;

[0032] Step 3, the Al2Mo3O 12 powder after pre-sintering of the system and the Al2Mo3O 12 LiMoVO6 powder after pre-sintering of the system are proportioned according to the formula 0.795Al2Mo3O 12 -0.205LiMoVO6, and then reloaded into a ball mill tank, zirconium balls and anhydrous ethanol are selected as the grinding medium to carry out planetary ball milling, the mass ratio of the total pre-sintered powder, zirconium balls and anhydrous ethanol is 1:5:1, and the ball milling time is 6 hours; after the ball milling is completed, the mixed slurry is placed in an oven for drying, and then an acrylic acid solution is added to the dried powder as a binder for granulation to prepare ceramic raw material;

[0033] Step 4, the ceramic raw material prepared in step 3 is pressed and formed, and then the temperature is raised at a rate of 2℃ / min to 450℃ for 2 hours to remove the binder, and then the temperature is raised at the same rate to 580℃-600℃ for 6 hours, to prepare a modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature, which has a chemical formula of 0.795Al2Mo3O 12 -0.205LiMoVO6.

[0034] The modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature prepared in this embodiment, 0.795Al2Mo3O 12 -0.205LiMoVO6, is subjected to X-ray diffraction test (i.e. XRD test) and scanning electron microscope observation (i.e. SEM observation) respectively, and the following results are obtained:

[0035] Figure 1 The XRD pattern of the 0.795Al2Mo3O 12 -0.205LiMoVO6 ceramic is obtained, and it can be found from the figure that the peak positions of all diffraction peaks match those of Al2Mo3O 12 and LiMoVO6, and no extra diffraction peaks appear, indicating that no chemical reaction occurs between the two phases at this sintering temperature, and the chemical compatibility is good.

[0036] Figure 2 The SEM morphology of the 0.795Al2Mo3O 12 -0.205LiMoVO6 ceramic is obtained, and it can also be found from the figure that the grain growth of the ceramic is sufficient at this sintering temperature, the grain size is about 2.4μm, and the micro-morphology is dense with low porosity, indicating that the ceramic has good low-temperature sintering characteristics.

[0037] By preparing xAl2Mo3O 12 -(1-x)LiMoVO6 with different proportions of raw materials and different sintering temperatures, the following performance parameter results are obtained:

[0038]

[0039]

[0040] From the table data, when x = 0.795 and the sintering temperature is 600℃, the xAl2Mo3O 12 The dielectric constant of the (1-x)LiMoVO6 ceramic reaches 7.05, and the lowest dielectric loss is 1.58x10 -3 At this time, the Qxf value reaches the best value of 8543GHz, and the τf value reaches the best value of -14.17ppm / ℃; when the Al2Mo3O 12 When the content is increased to 0.80, both the Qxf value and the τf value are poor. Therefore, by compounding the LiMoVO6 phase in the Al2Mo3O 12 system, the sintering temperature of the final ceramic is greatly reduced to 600℃, and the temperature stability of the resonance frequency is improved, and the 0.795Al2Mo3O 12 -0.205LiMoVO6 ceramic has low-temperature sintering characteristics, which expands the application potential of the ceramic in the field of ULTCC technology.

[0041] The above examples are only the preferred embodiments of the present application, and are not a limitation on the technical solutions of the present application. Any technical solutions that can be realized on the basis of the above examples without creative labor should be considered to fall within the protection scope of the present application patent.

Claims

1. A method for preparing a modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperatures, wherein the raw materials for the modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperatures are Al2O3, MoO3, Li2CO3, and V2O5, and its chemical formula is xAl2Mo3O 12 -(1-x)LiMoVO6, where x = 0.79~0.80, is characterized by: The preparation method of the modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature includes the following steps: Step 1: First, mix the raw Al2O3 and MoO3 powders according to the chemical formula Al2Mo3O 12 The ingredients were mixed to obtain Al2Mo3O 12 The raw material powder of the system; then the original powders of Li2CO3, MoO3 and V2O5 are formulated according to the general chemical formula LiMoVO6 to obtain the raw material powder of the LiMoVO6 system; Step 2: Prepare the Al2Mo3O4 mixture from Step 1. 12 The raw material powders of the system and the raw material powders of the LiMoVO6 system were separately loaded into ball mill jars, and ball milling was performed using zirconium balls and anhydrous ethanol as grinding media. After ball milling, the mixed slurry was placed in an oven to dry, and then sieved through a 60-100 mesh sieve. The sieved Al2Mo3O 12 The powder of the system was pre-calcined in an atmospheric atmosphere at 675℃~700℃ for 2~4 hours, and the sieved LiMoVO6 system powder was pre-calcined in an atmospheric atmosphere at 475~525℃ for 2~4 hours. Step 3: Remove the Al2Mo3O from Step 2. 12 The pre-calcined powder of the system and the pre-calcined powder of the LiMoVO6 system were prepared according to the chemical formula xAl2Mo3O 12 -(1-x)LiMoVO6 was prepared as a raw material, where x = 0.79~0.80, and then it was put into a ball mill jar again. Zirconium balls and anhydrous ethanol were selected as grinding media for ball milling. After ball milling, the mixed slurry was placed in an oven to dry, and then acrylic acid solution was added to the dried powder as a binder for granulation to obtain ceramic raw material. Step 4: Press the ceramic raw material obtained in Step 3 into shape, then remove the binder at a temperature of 400℃~450℃ for 2~4 hours at a heating rate of 2℃ / min~5℃ / min. Immediately afterwards, raise the temperature to 580℃ at the same rate and hold for 4~6 hours to obtain a modified molybdenum-based microwave dielectric ceramic sintered at ultra-low temperature, with the chemical formula xAl2Mo3O. 12 -(1-x)LiMoVO6, x = 0.79~0.

80.

2. The method for preparing modified molybdenum-based microwave dielectric ceramics by ultra-low temperature sintering according to claim 1, characterized in that: In step 2, the mass ratio of raw material powder, zirconium balls, and anhydrous ethanol is 1:5:(2~4), and the ball milling time is 4~6 hours; in step 3, the mass ratio of pre-calcined powder, zirconium balls, and anhydrous ethanol is 1:5:(1~3), and the ball milling time is 4~6 hours.

3. The method for preparing modified molybdenum-based microwave dielectric ceramics by ultra-low temperature sintering according to claim 1 or 2, characterized in that: Planetary ball milling is used in both steps 2 and 3.

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