CN111943670B - LiWVO6-K2MoO4 based composite ceramic microwave material and its preparation method - Google Patents

Abstract

The invention discloses LiWVO ₆ ‑K ₂ MoO ₄ The chemical general formula of the composite ceramic can be written into (1-x) LiWVO ₆ ‑xK ₂ MoO ₄ Where x is mass percent (x=60, 65, 70, 75, 80, 90 wt%). K (K) ₂ MoO ₄ The ceramic has excellent microwave performance, low sintering temperature of about 540 deg.c and epsilon _r About 7.5, qf-22300 GHz, but τ _f The value was-70 ppm/. Degree.C. Recently, a vanadate LiWVO was discovered ₆ The material has a monoclinic structure, and dielectric properties obtained by high-temperature sintering at 700 ℃ are as follows: epsilon _r ～11.5，Qf～13260GHz，τ _f +163.8ppm/. Degree.C. The invention prepares densified LiWVO below 200 ℃ by a cold sintering method ₆ ‑K ₂ MoO ₄ Composite ceramic, obtain (1-x) LiWVO of near zero resonance frequency temperature coefficient ₆ ‑xK ₂ MoO ₄ A base composite ceramic microwave material. The composite ceramic material can be widely applied to microwave devices such as resonators, filters and the like.

Description

LiWVO6-K2MoO4 based composite ceramic microwave material and its preparation method

technical field

The invention relates to the technical field of microwave communication electronic circuit device materials and low-carbon energy-saving production, in particular to a LiWVO ₆ -K ₂ MoO ₄ -based composite ceramic microwave material and a low-carbon energy-saving preparation method thereof.

Background technique

Microwave dielectric ceramics are widely used in modern wireless communication systems as resonators, couplers, filters, substrates and capacitors. With the rapid development of mobile communication technology in the direction of millimeter waves, modern electronic communication products are being revolutionized in the direction of generalization, miniaturization, and high efficiency, which has increased the requirements and demands for high-performance microwave materials. Specifically, microwave materials that can be used in modern mobile communication devices must meet the following three conditions. First, they must have a low dielectric constant (ε _r ) to reduce signal delay and speed up signal transmission. Second: have a high quality factor (Qf) for good filtering characteristics and communication quality. Third: It has a resonant frequency temperature coefficient (τ _f ) close to zero to ensure that the device prepared by using the microwave device can maintain stable temperature and work normally in different environments. Now a large number of microwave dielectric ceramics have excellent dielectric properties, but usually have too high sintering temperature or too large temperature coefficient of resonant frequency (τ _f ), which limits its application in actual production and does not meet the national initiative of green Environmentally friendly production. In order to overcome the above problems and reduce production energy consumption, the present invention adopts a sintering process for synthesizing dense ceramics at low temperature (≤200°C) by using water as a transient solvent under uniaxial pressure—cold sintering process (CSP) composite with negative K ₂ MoO ₄ with τ _f value and LiWVO ₆ with positive τ _f value are used to control the temperature coefficient, and (1-x)LiWVO ₆ -xK ₂ MoO ₄ with near zero temperature coefficient is prepared.

Contents of the invention

The object of the present invention is to provide a LiWVO ₆ -K ₂ MoO ₄ based composite ceramic microwave material and a preparation method thereof, to realize the preparation of a densified composite ceramic microwave material with fine and uniform crystal grains and a relative density greater than 92% under the condition of ≤200°C. The dielectric constant (ε _r ) of the composite ceramic microwave material ranges from 6.8 to 8.5, the quality factor Qf ranges from 2050GHz to 7180GHz, and the resonant frequency temperature coefficient _τf ranges from -49.3ppm/°C to +24.8ppm/°C. Compared with traditional high-temperature solid-state sintering (HTCC) and low-temperature co-firing (LTCC) technologies, this method has the characteristics of low sintering temperature, short sintering time, low carbon and energy saving.

In order to achieve the above object, the technical scheme adopted in the present invention is:

LiWVO ₆ -K ₂ MoO ₄ based composite ceramic microwave material, its chemical composition can be expressed by the following general formula: (1-x)LiWVO ₆ -xK ₂ MoO ₄ , where x is the mass percentage (x=60, 65, 70, 75, 80, 90wt%); its dielectric constant _εr ranges from 6.8 to 8.5, the quality factor Qf ranges from 2050GHz to 7180GHz, and the resonant frequency temperature coefficient _τf ranges from -49.3ppm/°C to +24.8ppm/°C .

The present invention also provides a low-carbon and energy-saving preparation method of LiWVO ₆ -K ₂ MoO ₄ -based composite ceramic microwave material, comprising the following steps:

(1) Ingredients: First, according to the stoichiometric ratio of Li, W, and V elements in the general chemical formula LiWVO ₆ , weigh the following experimental raw materials: Li ₂ CO ₃ (99.99%), WO ₃ (99.99%), NH ₄ VO ₃ (99.99%);

(2) Mixing: Pour the weighed above raw materials into a ball milling tank, use absolute ethanol as a ball milling medium, and ball mill in a ball milling tank for 4 hours to obtain a mixed slurry;

(3) Drying: Pour the mixed slurry into a tray covered with plastic wrap, put it in a drying oven and dry it at 80° C. to a constant weight to obtain a dry powder of the mixed material.

(4) Pre-burning: Pass the dry mixture powder obtained in the previous step through a 60-mesh sieve, then put it into a high-temperature furnace, raise the temperature to 700°C at a heating rate of 5°C/min, keep it warm for 6 hours, and then cool naturally. Make the mixed material preliminary reaction synthesis LiWVO ₆ compound;

(5) Secondary ball milling: Pour the initially synthesized LiWVO ₆ into a ball milling tank, and repeat steps (2) and (3).

(6) Ingredients: weigh the synthesized LiWVO ₆ and K ₂ MoO ₄ (purity 99%) raw materials by weight;

(7) Mixing: put the above weighed raw materials into a mortar, add 10 wt% deionized water of the total mass of the mixture, and grind evenly. Obtain different weight ratio LiWVO ₆ -K ₂ MoO ₄ mixture slurry;

(8) Cold sintering: put the above-ground aqueous mixture slurry into a mold, then put the mold into a hot press, heat to 160°C, apply a pressure of 300MPa, and hot press for 60 minutes to obtain a densified sample;

(9) Drying: The densified composite ceramic sample obtained above was further dried for 24 hours in an oven at 120° C. to remove residual moisture to obtain a finished LiWVO ₆ -K ₂ MoO ₄ composite ceramic.

In the above technical solution, the raw materials for preparing composite ceramics are lithium carbonate (LiCO ₃ ), tungsten trioxide (WO ₃ ), ammonium metavanadate (NH ₄ VO ₃ ) and potassium molybdate (K ₂ MoO ₄ ). Its low-carbon and energy-saving preparation method is as follows: firstly, the raw materials (lithium carbonate, tungsten trioxide and silicon dioxide) are weighed at a certain stoichiometric ratio, ball milled evenly, dried, and pre-calcined to synthesize LiWVO ₆ compound; then the prepared LiWVO ₆ and K ₂ MoO ₄ were weighed in a certain weight ratio; 10wt% deionized water was added to mix the LiWVO ₆ and K ₂ MoO ₄ composite powder; the composite mixture was placed in a mold and heated in a hot press at 160°C, Apply a pressure of 300 MPa, heat press for 60 minutes, take out the sample after cooling, and dry it at 120°C for 24 hours to obtain a dense (1-x)LiWVO ₆ -xK ₂ MoO ₄ composite ceramic material. The low-temperature energy-saving preparation method can prepare LiWVO ₆ -K ₂ MoO ₄ -based composite ceramics with fine and uniform crystal grains and a relative density of ≥92% under the low temperature condition of ≤200°C. Compared with the conventional ceramic sintering (HTCC and LTCC) technology, this method can not only achieve densification in a lower temperature range, obtain a composite matrix microwave ceramic material with good temperature stability, but also reduce the time spent in its preparation and processing. Carbon emissions and energy consumption.

In the above technical solution, the two ceramic materials LiWVO ₆ and K ₂ MoO ₄ used in the present invention both have low dielectric constant and high quality factor. The low dielectric constant can shorten the propagation delay time of electromagnetic and other signals and minimize the cross-coupling between conductors, and the high quality factor can reduce the energy loss of the microwave system and expand the frequency selection range of the resonator. At the same time, LiWVO ₆ has a positive temperature coefficient of resonant frequency, and K ₂ MoO ₄ has a negative temperature coefficient of resonant frequency. By combining these two ceramic materials, LiWVO ₆ -K ₂ MoO ₄ base with nearly zero resonant frequency temperature coefficient can be obtained. Composite ceramic microwave materials. The near-zero resonant frequency temperature coefficient can ensure the stability of the operating frequency to temperature changes. Moreover, the present invention adopts cold sintering (CSP) technology to synthesize LiWVO ₆ -K ₂ MoO ₄ -based composite ceramic microwave materials, and realizes densification at a low temperature of ≤ 200°C. The process is simple, and the cycle of preparing ceramics is much shorter than that of traditional sintering methods. , and the preparation process consumes less energy, and the pollutants are also greatly reduced, so that the composite material has great potential in the manufacturing process of wireless communication technology.

The beneficial effects of the present invention are:

(1) The present invention adopts cold sintering technology to synthesize LiWVO ₆ -K ₂ MoO ₄ -based composite ceramic microwave material, and traditional high-temperature sintering technology (CS) and low-temperature co-firing technology (LTCC), its preparation process is simple, only 160 ° C The sintering temperature and sintering time only need 1h, which greatly shortens the preparation cycle of ceramics and reduces carbon emissions.

(2) The present invention does not require a PVA binder, uses deionized water as an instantaneous liquid, mixes the powder and water into a mold, and then sinters to prepare LiWVO ₆ with fine and uniform grains and a relative density ≥ 92% - K ₂ MoO ₄ -based composite ceramics.

Description of drawings

Fig. 1 is the XRD spectrum of the composite ceramic microwave material prepared by Examples 1-6 of the present invention;

Fig. 2 is the SEM accompanying drawing of the composite ceramic microwave material prepared by Examples 1-6 of the present invention;

Fig. 3 is the accompanying drawing of the relative density of the composite ceramic microwave material prepared by Examples 1 to 6 of the present invention;

Fig. 4 is the accompanying drawing of the dielectric constant of the composite ceramic microwave material prepared by Examples 1 to 6 of the present invention;

Fig. 5 is a figure of quality factor of the composite ceramic microwave material prepared by Examples 1-6 of the present invention;

Fig. 6 is the resonant frequency temperature coefficient of the composite ceramic microwave material prepared in Examples 1-6 of the present invention.

The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings.

Detailed ways

The technical solutions provided by the present invention will be further described below in conjunction with the accompanying drawings.

The present invention provides a LiWVO ₆ -K ₂ MoO ₄ -based composite ceramic microwave material and a low-carbon preparation method thereof, for details, refer to the following examples.

Example 1: Preparation of 40wt% LiWVO ₆ -60wt% K ₂ MoO ₄ composite ceramic microwave material

Li ₂ CO ₃ (99.99%) 4.3758g, WO ₃ (99.99%) 27.4597g, NH ₄ VO ₃ (99.99%) 13.8547g were weighed successively. Put the above-weighed material in a ball mill tank with absolute ethanol as the medium for ball milling for 12 hours to obtain a slurry-like raw material; pour the mixed slurry into a tray covered with plastic wrap, put it in a drying box and dry it until Constant weight to obtain the dry powder of the mixture. Grind the dried mixed dry material through a 60-mesh sieve, then put it into a high-temperature furnace, raise the temperature to 700°C at a heating rate of 5°C/min and keep it warm for 6 hours, and then cool down naturally. The mixture was initially reacted to synthesize 40 g of LiWVO ₆ compound.

Then, 0.8000 g of synthesized LiWVO ₆ powder and 1.2121 g of K ₂ MoO ₄ (99%) raw material were weighed sequentially and placed in a mortar to obtain 2.0121 g of LiWVO ₆ , K ₂ MoO ₄ mixed powder. Then take 10wt% deionized water of the total mass of the mixture and add it into the powder and grind it evenly to form a slurry. Choose a steel mold with an inner hole diameter of 12mm. Before using the mold, use degreased cotton dipped in absolute ethanol to wipe the inner wall of the mold, the ejector pin, and the pad. After the mold is dry, weigh an appropriate amount of slurry and put it in In the mold, use a uniaxial press to apply a pressure of 300MPa, and heat the mold to 160°C at a heating rate of 6°C/min, keep it warm for 60min, cool down, eject the mold, and take out the sample. The obtained sample was further dried in an oven at 120° C. for 24 hours to remove residual moisture, and a 40wt% LiWVO ₆ -60wt% K ₂ MoO ₄ composite ceramic microwave material was obtained. Carry out XRD analysis to the product that example 1 prepares, as shown in accompanying drawing 1, the XRD pattern of the product that example 1 prepares comprises LiWVO ₆ and K ₂ MoO ₄ two phases, and there is no mutual reaction between the two, can be very good It matches the standard PDF cards PDF#26-1205 (LiWVO ₆ ) and PDF#29-1021 (K ₂ MoO ₄ ) of the crystal structure database, indicating that Example 1 successfully prepared 40wt% LiWVO ₆ -60wt% K ₂ MoO ₄ composite ceramics microwave material. The product prepared in Example 1 is scanned by SEM image, as shown in accompanying drawing 2, the SEM spectrum of the product prepared in Example 1 shows that the sample crystallization is good, the grain boundaries are clearer, the grain distribution is more uniform, and it shows a relatively dense micro structure. The relative density of the product prepared in Example 1 was calculated, and as shown in Figure 3, the relative density of the product prepared in Example 1 was 92.7%. The dielectric constant (ε _r ) of the product prepared in Example 1 was tested, and as shown in Figure 4, the ε _r of the product prepared in Example 1 was 8.5. The quality factor (Qf) test was carried out on the product prepared in Example 1, as shown in Figure 5, the Qf of the product prepared in Example 1 was 2050 GHz. The resonant frequency temperature coefficient (τ _f ) of the product prepared in Example 1 was tested. As shown in Figure 6, the τ _f of the product prepared in Example 1 was +24.8ppm/°C. As can be seen from the results in the accompanying drawings, the product prepared in Example 1 has a high relative density and good microwave dielectric properties.

Example 2: Preparation of 35wt% LiWVO ₆ -65wt% K ₂ MoO ₄ composite ceramic microwave material

0.7000 g of LiWVO ₆ powder synthesized in Example 1 and 1.3131 g of K ₂ MoO ₄ (99%) raw material were successively weighed and placed in a mortar to obtain 2.0131 g of LiWVO ₆ -K ₂ MoO ₄ mixed powder. Then take 10wt% deionized water of the mass of the mixed powder and add it into the powder and grind it evenly to form a slurry. Choose a steel mold with an inner hole diameter of 12mm. Before using the mold, use degreased cotton dipped in absolute ethanol to wipe the inner wall of the mold, the ejector pin, and the pad. After the mold is dry, weigh an appropriate amount of slurry and put it in In the mold, use a uniaxial press to apply a pressure of 300MPa, and heat the mold to 160°C at a heating rate of 6°C/min, keep it warm for 60min, cool down, eject the mold, and take out the sample. The obtained sample was dried in a drying oven at 120° C. for 24 hours to further remove residual moisture to obtain a 35wt% LiWVO ₆ -65wt% K ₂ MoO ₄ composite ceramic microwave material. Carry out XRD analysis to the product that example 2 prepares, as shown in accompanying drawing 1, the XRD pattern of the product that example 2 prepares comprises LiWVO ₆ and K ₂ MoO ₄ two phases, and there is no mutual reaction between the two, can be very good It matches the standard PDF cards PDF#26-1205 (LiWVO ₆ ) and PDF#29-1021 (K ₂ MoO ₄ ) of the crystal structure database, indicating that Example 2 successfully prepared 20wt% LiWVO ₆ -80wt% K ₂ MoO ₄ composite ceramics microwave material. The product prepared in example 2 is scanned by SEM image, as shown in accompanying drawing 2, the SEM spectrum of the product prepared in example 2 shows that the sample crystallization is good, the grain boundary is clearer, the grain distribution is uniform, and the grain grows to some extent. The microstructure is denser. The relative density of the product prepared in Example 2 is calculated, as shown in Figure 3, the relative density of the product prepared in Example 2 is 94.6%. The dielectric constant (ε _r ) of the product prepared in Example 2 was tested, and as shown in Figure 4, the ε _r of the product prepared in Example 2 was 8.2. The quality factor (Qf) test was carried out on the product prepared in Example 2, as shown in Figure 5, the Qf of the product prepared in Example 2 was 3260 GHz. The resonant frequency temperature coefficient (τ _f ) of the product prepared in Example 2 was tested. As shown in Figure 6, the τ _f of the product prepared in Example 2 was +9.9ppm/°C. As can be seen from the results in the accompanying drawings, the product prepared in Example 2 has a high relative density and good microwave dielectric properties.

Example 3: Preparation of 30wt% LiWVO ₆ -70wt% K ₂ MoO ₄ composite ceramic microwave material

0.6000 g of LiWVO ₆ powder synthesized in Example 1 and 1.3131 g of K ₂ MoO ₄ (99%) raw material were successively weighed and placed in a mortar to obtain 2.0141 g of LiWVO ₆ -K ₂ MoO ₄ mixed powder. Then take 10wt% deionized water of the mass of the mixed powder and add it into the powder and grind it evenly to form a slurry. Choose a steel mold with an inner hole diameter of 12mm. Before using the mold, use degreased cotton dipped in absolute ethanol to wipe the inner wall of the mold, the ejector pin, and the pad. After the mold is dry, weigh an appropriate amount of slurry and put it in In the mold, use a uniaxial press to apply a pressure of 300MPa, and heat the mold to 160°C at a heating rate of 6°C/min, keep it warm for 60min, cool down, eject the mold, and take out the sample. The obtained sample was dried in a drying oven at 120° C. for 24 hours to further remove residual moisture to obtain a 30wt% LiWVO ₆ -70wt% K ₂ MoO ₄ composite ceramic microwave material. Carry out XRD analysis to the product that example 3 prepares, as shown in accompanying drawing 1, the XRD figure of the product that example 3 prepares comprises LiWVO ₆ and K ₂ MoO ₄ two phases, and there is no mutual reaction between the two, can be very good It matches the standard PDF cards PDF#26-1205 (LiWVO ₆ ) and PDF#29-1021 (K ₂ MoO ₄ ) of the crystal structure database, indicating that Example 3 successfully prepared 30wt% LiWVO ₆ -70wt% K ₂ MoO ₄ composite ceramics microwave material. The product prepared in example 3 is scanned by SEM image, as shown in accompanying drawing 2, the SEM spectrum of the product prepared in example 3 shows that the sample crystallization is good, the grain size reduces, the grain boundary is clear, and the gap between the grains decreases, the grain distribution becomes compact. The relative density of the product prepared in Example 3 was calculated, and as shown in Figure 3, the relative density of the product prepared in Example 3 was 95.3%. The dielectric constant (ε _r ) of the product prepared in Example 3 was tested, and as shown in Figure 4, the ε _r of the product prepared in Example 3 was 7.8. The quality factor (Qf) test was carried out on the product prepared in Example 3, as shown in Figure 5, the Qf of the product prepared in Example 3 was 4510 GHz. The resonant frequency temperature coefficient (τ _f ) of the product prepared in Example 3 was tested. As shown in Figure 5, the τ _f of the product prepared in Example 3 was +1.3ppm/°C. As can be seen from the results in the accompanying drawings, the product prepared in Example 3 has a high relative density and good microwave dielectric properties.

Example 4: Preparation of 25wt% LiWVO ₆ -75wt% K ₂ MoO ₄ composite ceramic microwave material

0.5000 g of LiWVO ₆ powder synthesized in Example 1 and 1.5151 g of K ₂ MoO ₄ (99%) raw material were successively weighed and placed in a mortar to obtain 2.0151 g of LiWVO ₆ -K ₂ MoO ₄ mixed powder. Then take 10wt% deionized water of the mass of the mixed powder and add it into the powder and grind it evenly to form a slurry. Choose a steel mold with an inner hole diameter of 12mm. Before using the mold, use degreased cotton dipped in absolute ethanol to wipe the inner wall of the mold, the ejector pin, and the pad. After the mold is dry, weigh an appropriate amount of slurry and put it in In the mold, use a uniaxial press to apply a pressure of 300MPa, and heat the mold to 160°C at a heating rate of 6°C/min, keep it warm for 60min, cool down, eject the mold, and take out the sample. The obtained sample was dried in a drying oven at 120° C. for 24 hours to further remove residual moisture to obtain a 25wt% LiWVO ₆ -75wt% K ₂ MoO ₄ composite ceramic microwave material. Carry out XRD analysis to the product that example 4 prepares, as shown in accompanying drawing 1, the XRD pattern of the product that example 4 prepares comprises LiWVO ₆ and K ₂ MoO ₄ two phases, and there is no mutual reaction between the two, can be very good It matches the standard PDF cards PDF#26-1205 (LiWVO ₆ ) and PDF#29-1021 (K ₂ MoO ₄ ) of the crystal structure database, indicating that Example 4 successfully prepared 40wt% LiWVO ₆ -60wt% K ₂ MoO ₄ composite ceramics microwave material. The product prepared in Example 4 is scanned by SEM image, as shown in Figure 2, the SEM spectrum of the product prepared in Example 4 shows that the sample crystallization is good, the grain size is smaller than that of Example 1, and the grain boundaries are clear. The gap between them is reduced, and the distribution of grains is compact. The relative density of the product prepared in Example 4 was calculated, and as shown in Figure 3, the relative density of the product prepared in Example 4 was 96.6%. The dielectric constant (ε _r ) of the product prepared in Example 4 was tested, and as shown in Figure 4, the ε _r of the product prepared in Example 4 was 7.6. The quality factor (Qf) test was carried out on the product prepared in Example 4, as shown in Figure 4, the Qf of the product prepared in Example 4 was 5315 GHz. The resonant frequency temperature coefficient (τ _f ) of the product prepared in Example 4 was tested. As shown in Figure 6, the τ _f of the product prepared in Example 4 was -12.7ppm/°C. As can be seen from the results in the accompanying drawings, the product prepared in Example 4 has a high relative density and good microwave dielectric properties.

Example 5: Preparation of 20wt% LiWVO ₆ -80wt% K ₂ MoO ₄ composite ceramic microwave material

0.4000 g of LiWVO ₆ powder synthesized in Example 1 and 1.6161 g of K ₂ MoO ₄ (99%) raw material were weighed in turn and placed in a mortar to obtain 2.0161 g of LiWVO ₆ -K ₂ MoO ₄ mixed powder. Then take 10wt% deionized water of the mass of the mixed powder and add it into the powder and grind it evenly to form a slurry. Choose a steel mold with an inner hole diameter of 12mm. Before using the mold, use degreased cotton dipped in absolute ethanol to wipe the inner wall of the mold, the ejector pin, and the pad. After the mold is dry, weigh an appropriate amount of slurry and put it in In the mold, use a uniaxial press to apply a pressure of 300MPa, and heat the mold to 160°C at a heating rate of 6°C/min, keep it warm for 60min, cool down, eject the mold, and take out the sample. The obtained sample was dried in a drying oven at 120° C. for 24 hours to further remove residual moisture to obtain a 20wt% LiWVO ₆ -80wt% K ₂ MoO ₄ composite ceramic microwave material. Carry out XRD analysis to the product that example 5 prepares, as shown in accompanying drawing 1, the XRD figure of the product that example 5 prepares comprises LiWVO ₆ and K ₂ MoO ₄ two phases, and there is no mutual reaction between the two, can be very good It matches the standard crystal structure database PDF card PDF#26-1205 (LiWVO ₆ ) and PDF#29-1021 (K ₂ MoO ₄ ), indicating that Example 5 successfully prepared 50wt% LiWVO ₆ -50wt% K ₂ MoO ₄ composite ceramic microwave Material. The product prepared in Example 5 is scanned by SEM image, as shown in accompanying drawing 2, the SEM spectrum of the product prepared in Example 5 shows that the sample crystallization is good, because K ₂ MoO ₄ crystal grains are small, along with K ₂ MoO ₄ With the increase of the mass fraction, the grain size decreases, the grain boundary is clear, the gap between the grains decreases, and the distribution of the grains is compact, showing a dense microstructure. The relative density of the product prepared in Example 5 was calculated, and as shown in Figure 3, the relative density of the product prepared in Example 5 was 98.5%. The dielectric constant (ε _r ) of the product prepared in Example 5 was tested, and as shown in Figure 4, the ε _r of the product prepared in Example 5 was 7.3. The quality factor (Qf) test was carried out on the product prepared in Example 5, as shown in Figure 5, the Qf of the product prepared in Example 5 was 5965 GHz. The resonant frequency temperature coefficient (τ _f ) of the product prepared in Example 5 was tested. As shown in Figure 6, the τ _f of the product prepared in Example 5 was -20.1ppm/°C. As can be seen from the results in the accompanying drawings, the product prepared in Example 5 has a high relative density and good microwave dielectric properties.

Example 6: Preparation of 10wt% LiWVO ₆ -90wt% K ₂ MoO ₄ composite ceramic microwave material

0.1000 g of LiWVO ₆ powder synthesized in Example 1 and 1.8181 g of K ₂ MoO ₄ (99%) raw material were successively weighed and placed in a mortar to obtain 2.0181 g of LiWVO ₆ -K ₂ MoO ₄ mixed powder. Then take 10wt% deionized water of the mass of the mixed powder and add it into the powder and grind it evenly to form a slurry. Choose a steel mold with an inner hole diameter of 12mm. Before using the mold, use degreased cotton dipped in absolute ethanol to wipe the inner wall of the mold, the ejector pin, and the pad. After the mold is dry, weigh an appropriate amount of slurry and put it in In the mold, use a uniaxial press to apply a pressure of 300MPa, and heat the mold to 160°C at a heating rate of 6°C/min, keep it warm for 60min, cool down, eject the mold, and take out the sample. The obtained sample was dried in a drying oven at 120° C. for 24 hours to further remove residual moisture to obtain a 10wt% LiWVO ₆ -90wt% K ₂ MoO ₄ composite ceramic microwave material. Carry out XRD analysis to the product that example 6 prepares, as shown in accompanying drawing 1, the XRD pattern of the product that example 6 prepares comprises LiWVO ₆ and K ₂ MoO ₄ two phases, and there is no mutual reaction between the two, can be very good It matches the standard crystal structure database PDF card PDF#26-1205 (LiWVO ₆ ) and PDF#29-1021 (K ₂ MoO ₄ ), indicating that Example 6 successfully prepared 60wt% LiWVO ₆ -40wt% K ₂ MoO ₄ composite ceramic microwave Material. The product that example 6 prepares is carried out SEM image scanning, as shown in accompanying drawing 2, the SEM collection of illustrative plates of the product that example 6 prepares shows that sample crystallization is good, and crystal grain grain boundary is clear, and the gap between crystal grain is few, and grain The distribution of particles is compact, showing a dense microstructure. The relative density of the product prepared in Example 6 was calculated, and as shown in Figure 3, the relative density of the product prepared in Example 6 was 98.7%. The dielectric constant (ε _r ) of the product prepared in Example 6 was tested, and as shown in Figure 3, the ε _r of the product prepared in Example 6 was 6.8. The quality factor (Qf) test was carried out on the product prepared in Example 6, as shown in Figure 5, the Qf of the product prepared in Example 6 was 7180 GHz. The resonant frequency temperature coefficient (τ _f ) of the product prepared in Example 6 was tested. As shown in Figure 6, the τ _f of the product prepared in Example 6 was -49.3ppm/°C. As can be seen from the results in the accompanying drawings, the product prepared in Example 6 has a high relative density and good microwave dielectric properties.

The descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (1)

1. LiWVO ₆ -K ₂ MoO ₄ based composite ceramic microwave material, characterized in that: the general formula of the chemical composition of the composite ceramic microwave material is: (1-x)LiWVO ₆ -xK ₂ MoO ₄ , x is the mass percentage ; The dielectric constant _εr of the composite ceramic microwave material ranges from 6.8 to 8.5, the quality factor Qf ranges from 2050GHz to 7180GHz, and the resonant frequency temperature coefficient _τf ranges from -49.3ppm/°C to +24.8ppm/°C; Wherein, x is 60, 65, 70, 75, 80 or 90 wt%; The preparation method of the composite ceramic microwave material comprises the following steps: (1) Ingredients: First, according to the stoichiometric ratio of Li, W, and V elements in the general chemical formula LiWVO ₆ , weigh the following experimental raw materials: Li ₂ CO ₃ , WO ₃ , NH ₄ VO ₃ ; (2) Mixing: Pour the weighed above raw materials into a ball milling tank, use absolute ethanol as a ball milling medium, and ball mill in a ball milling tank to obtain a mixed slurry; (3) Drying: Pour the mixed slurry into a tray covered with plastic wrap, put it into a drying box and dry it to constant weight at 80°C to obtain a dry powder of the mixed material; (4) Pre-burning: pass the dry mixture powder obtained in the previous step through a 60-mesh sieve, then put it into a high-temperature furnace, raise the temperature to 700°C at a heating rate of 5°C/min, keep it warm for 6h, and then cool naturally; make the mixture preliminary Reaction synthesis LiWVO ₆ compound; (5) Secondary ball milling: the initially synthesized LiWVO ₆ is poured into the ball milling tank, and steps (2) (3) are repeated; (6) Ingredients: weigh the synthesized LiWVO ₆ and K ₂ MoO ₄ raw materials by weight; (7) Mixing: put the above weighed raw materials into a mortar, add 10wt% deionized water of the total mass of the mixture, and grind evenly; obtain different weight ratios LiWVO ₆ -K ₂ MoO ₄ mixture slurry, That is, (1-x)LiWVO ₆ -xK ₂ MoO ₄ , x is the mass percentage; (8) Cold sintering: put the above-ground aqueous mixture slurry into a mold, then put the mold into a hot press, heat to 160°C, apply a pressure of 300MPa, and hot press for 60 minutes to obtain a densified sample; (9) Drying: The densified composite ceramic sample obtained above was further dried for 24 hours in an oven at 120°C to remove residual moisture to obtain a finished LiWVO ₆ -K ₂ MoO ₄ composite ceramic; In the above preparation method, the purity of Li ₂ CO ₃ is at least 99.99%; the purity of WO ₃ is at least 99.99%; the purity of NH ₄ VO ₃ is at least 99.99%; the purity of K ₂ MoO ₄ is at least 99%.

Images