CN111499372A - A low-temperature energy-saving method for preparing LiMgPO4 microwave ceramic materials - Google Patents

Abstract

The invention discloses a method for preparing LiMgPO ₄ microwave ceramic material with low temperature and energy saving. LiMgPO ₄ is mixed with water or acetic acid not higher than 20 wt % to form a solid-liquid mixture, and then a hot pressing method is used to adjust the sintering temperature (ST), heat preservation Time (T) and applied pressure (P) to achieve its densification into ceramics, wherein: ST is 150°C, 200°C, 250°C or 300°C; T=30min, 60min or 90min; P=350MPa or 600MPa; obtained by this method The range of the dielectric constant (ε _r ) is 5.1～6.5, the range of quality factor Q×f is 3,600GHz～ _16,000GHz , and the range of temperature coefficient of resonant frequency (TCF) is ‑46.1ppm/℃～‑ 59.5ppm/°C. The LiMgPO ₄ microwave ceramic material prepared by the method can be used as a material for electronic components such as a substrate and a resonant antenna in a microwave radio frequency system (for example, a 5G/6G communication system). Compared with conventional ceramic sintering (HTCC and LTCC) technologies, this method can not only achieve densification in a lower temperature range, but also reduce carbon emissions and energy consumption during its preparation and processing.

Description

A low-temperature energy-saving method for preparing LiMgPO4 microwave ceramic materials

technical field

The invention relates to the technical field of communication electronic circuit component materials and low-carbon energy-saving production, in particular to a low-carbon energy-saving manufacturing method comprising LiMgPO ₄ microwave ceramic material.

Background technique

Microwave dielectric ceramic is a kind of multi-functional dielectric ceramic material with microwave communication application as the background. It is usually used as dielectric antenna, dielectric resonator, dielectric filter, dielectric substrate and microstrip line medium in radio frequency electronic circuit communication system. Component materials used. With the development of 5G/6G mobile communication technology, in order to further provide 5G/6G communication technology with faster and more reliable broadband access, larger capacity and shorter response delay, it is urgent to develop work on 5G/6G High-quality integrated ceramic components in frequency bands. According to the electromagnetic propagation theory, at millimeter-wave frequencies, the delay of signal transmission depends on the dielectric constant of the dielectric material. The lower the dielectric constant of the electromagnetic signal passing through the dielectric material, the smaller the delay of signal transmission and response. In the 5G/6G communication network, the dielectric constant of the communication base station and the terminal dielectric material plays a key role in the overall system signal delay. In addition, the temperature stability and dielectric loss of the device under the working environment temperature are also important parameters to ensure the reliability of the device. Therefore, the microwave dielectric ceramic materials used in these 5G/6G devices should have low dielectric constant, high quality factor, near-zero resonant frequency temperature coefficient, and functions that can be integrated into 5G systems. At this stage, most microwave dielectric ceramics are fabricated using conventional high temperature solid phase sintering (HTCC) and low temperature co-firing (LTCC) techniques and cannot be directly integrated into polymer circuit boards. In order to overcome the above problems and reduce production energy consumption, the present invention uses low temperature hot pressing sintering technology to densify the desired integrated ceramic components at a temperature below the melting point of the polymer (usually <300°C) and co-fire with silver electrodes, In order to obtain microwave ceramic materials that can meet the application of 5G devices.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a low-temperature energy-saving preparation method of LiMgPO ₄ microwave ceramic material, which realizes the preparation of densified ceramics with fine and uniform crystal grains and a relative density of ≥82% under the condition of ≤300°C. The dielectric constant (ε _r ) of the LiMgPO ₄ microwave ceramic material obtained by this method ranges from 5.4 to 6.5, the quality factor Q×f value ranges from 3,600GHz to 16,000GHz, and the temperature coefficient of resonance frequency (TCF) ranges from -46.1ppm. /℃～-59.5ppm/℃. Compared with the traditional high temperature solid phase sintering (HTCC) and low temperature co-firing (LTCC) technologies, this method has the characteristics of low sintering temperature, short sintering time and low energy consumption. At the same time, due to its low-temperature sintering characteristics, impurity phases are not easily generated during the process.

For achieving the above object, the technical scheme adopted in the present invention is as follows:

A method for preparing LiMgPO ₄ microwave ceramic material with low temperature and energy saving. LiMgPO ₄ is mixed with water or acetic acid not higher than 20wt% to form a solid-liquid mixture, and then a hot pressing method is used to adjust the sintering temperature (ST), holding time (T ) and applying pressure (P) to achieve its densification into a ceramic, wherein: ST is 150°C, 200°C, 250°C or 300°C; T=30min, 60min or 90min; P=350MPa or 600MPa; _LiMgPO4 obtained by this method Ceramics, the dielectric constant (ε _r ) ranges from 5.1 to 6.5, the quality factor Q×f ranges from 3,600GHz to 16,000GHz, and the temperature coefficient of resonance frequency (TCF) ranges from -46.1ppm/°C to -59.5ppm/ °C.

The above technical solution involves four process parameters: sintering temperature, holding time, pressure and solvent type. The method is mainly described in the following order of parameters: 1) sintering temperature, lower than 300 °C; 2) sintering time, lower than 1.5 hours; 3) pressure, lower than 600 MPa, and 4) solvent, water and acetic acid. The dielectric constant (ε _r ) of the LiMgPO ₄ microwave ceramic material prepared by this method ranges from 5.1 to 6.5, the quality factor Q×f value ranges from 3,600GHz to 16,000GHz, and the resonant frequency temperature (TCF) ranges from -46.1ppm. /°C～-59.5ppm/°C The material can be used as a substrate, resonant antenna and other electronic component materials in microwave radio frequency systems (such as 5G/6G communication systems).

The preparation raw materials of the ceramics are basic magnesium carbonate ((MgCO ₃ ) _4˙Mg (OH) 2˙5H ₂ O), lithium carbonate (Li _{2 CO 3} ), and ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ). The low-carbon and energy-saving preparation method is as follows: firstly, the raw materials (basic magnesium carbonate, lithium carbonate and ammonium dihydrogen phosphate) are weighed in a certain stoichiometric ratio, ball-milled uniformly, dried, and pre-sintered to synthesize _LiMgPO compound powder; then add 15 wt. % water is mixed evenly; the semi-dry and semi-wet mixture is placed in a mold, heated to a certain temperature in a hot press, pressurized at 600 MPa, hot-pressed for 60 minutes, cooled, taken out and dried at 120 ° C for 24 hours to obtain Dense LiMgPO ₄ ceramic material. The low-temperature energy-saving preparation method can prepare ceramics with fine and uniform crystal grains and a relative density greater than 82% under the low temperature condition of sintering temperature lower than 300 DEG C. Compared with conventional ceramic sintering (HTCC and LTCC) technologies, this method can not only achieve densification in a lower temperature range, but also reduce carbon emissions and energy consumption during its preparation and processing.

As a further improvement scheme, the following steps are further included:

(1) Ingredients: First, according to the stoichiometric ratio of Li, Mg, and P elements in the chemical formula LiMgPO ₄ , weigh each raw material: Li ₂ CO ₃ (purity 99.99%), (MgCO ₃ ) ₄ ˙Mg(OH) ₂ ˙ 5H ₂ O (purity 99.99%), NH ₄ H ₂ PO ₄ (purity 99.99%);

(2) Mixing: pour each raw material into a ball mill tank, use isopropyl alcohol as a ball milling medium, and mix the ball mill for 4 hours to obtain a mud-like raw material;

(3) Drying: pour out the ball-milled slurry, put it in an oven and dry at 80°C to obtain a dry powder of the mixture;

(4) Calcination: The dry powder of the mixture obtained in the previous step was placed in a high-temperature furnace for pre-calcination for 4 hours, and the pre-calcination temperature was 500 °C. The obtained powder was calcined at 800 °C for 4 hours to obtain the final LiMgPO ₄ block , ground and passed through a 300-mesh nylon sieve.

(5) Mixing: add 15wt% deionized water or acetic acid solution (1M) to the above mixture, and mix to form a dough-like aqueous mixture;

(6) Low-temperature sintering: put the water-containing mixture slurry obtained in the previous step into a shape mold, move the mold to a hot press, heat to different sintering temperature points, press 600 MPa, and hot press for 30 minutes, 60 minutes, 90 minutes minutes to obtain densified ceramics;

(7) Drying: The densified ceramic sample obtained in the previous step was further dried in a drying oven at 120° C. for 24 hours to remove residual moisture to obtain a LiMgPO ₄ ceramic product.

In the above technical solutions, the LiMgPO ₄ ceramic materials obtained by the present invention all have low dielectric constant and high quality factor. Low dielectric constant can shorten the propagation delay time of electromagnetic and other signals and minimize the cross-coupling between conductors, and high quality factor can reduce the energy loss of electrical signals and improve the frequency selection accuracy of resonant filters. The invention realizes the densification of LiMgPO4 ceramics, low energy consumption and low pollution within 1.5 hours at a temperature lower than 300 DEG C.

The beneficial effects of the present invention are:

(1) The present invention adopts low-temperature energy-saving technology to sinter the densified _LiMgPO ceramic material. Compared with traditional ceramic high-temperature and low-temperature solid-phase sintering, the present invention has simple preparation process, lower sintering temperature, short time, energy saving and pollution reduction, especially It is Li ⁺ volatilization pollution.

(2) The present invention does not require a PVA binder, uses deionized water as a catalyst, mixes powder and water into a mold, and sinters at a pressure lower than 300 ° C and 600 MPa to prepare fine and uniform crystal grains. LiMgPO ₄ ceramics with relative density ≥ 82%.

Description of drawings

Fig. 1 is the XRD pattern of the prepared LiMgPO ₄ (abbreviated LMP) microwave ceramic material of Examples 1 to 4, 7, and 8 of the present invention;

Fig. 2 is the accompanying drawing of the relative density of the LiMgPO ₄ microwave ceramic material prepared in Examples 1-6 of the present invention;

Fig. 3 is the accompanying drawing of relative density of _LiMgPO microwave ceramic material prepared in Examples 3, 7, and 8 of the present invention;

Fig. 4 is a drawing showing the relative density of the LiMgPO ₄ microwave ceramic materials prepared in Examples 2, 7, 8, 9-11 of the present invention;

FIG. 5 is a drawing of the dielectric constant (ε _r ) of the LiMgPO ₄ microwave ceramic material prepared in Examples 1 to 6 of the present invention;

FIG. 6 is a drawing of the dielectric constant (ε _r ) of the LiMgPO ₄ microwave ceramic material prepared in Examples 3, 7, and 8 of the present invention;

Fig. 7 is a drawing of the dielectric constant (ε _r ) of the LiMgPO ₄ microwave ceramic material prepared in Examples 2, 7, 8, 9-11 of the present invention;

Fig. 8 is the figure of merit (Q×f) of the LiMgPO ₄ microwave ceramic material prepared in Examples 1-6 of the present invention;

Fig. 9 is the figure of merit (Q×f) of the _LiMgPO microwave ceramic material prepared in Examples 3, 7, and 8 of the present invention;

10 is the figure of merit (Q×f) of the LiMgPO ₄ microwave ceramic material prepared in Examples 2, 7, 8, 9-11 of the present invention;

Figure 11 is the accompanying drawing of the temperature coefficient of resonance frequency (TCF) of the _LiMgPO microwave ceramic material prepared in Examples 1 to 6 of the present invention;

Figure 12 is the accompanying drawing of the temperature coefficient of resonance frequency (TCF) of the _LiMgPO microwave ceramic material prepared in Examples 3, 7, and 8 of the present invention;

Figure 13 is the accompanying drawing of the temperature coefficient of resonance frequency (TCF) of the LiMgPO microwave ceramic material prepared in Examples ₂ , 7, 8, 9-11 of the present invention;

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

Detailed ways

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

The present invention provides a microwave ceramic material composed of LiMgPO ₄ and a low-carbon and energy-saving preparation method thereof. For details, refer to the following examples.

Example 1: Preparation of LiMgPO ₄ microwave ceramic material at 150℃-600MPa-30min

Weigh 1.40g of LiMgPO ₄ powder (weigh the successfully prepared LiMgPO ₄ powder in steps 1, 2, 3, and 4), measure deionized water (15% of the mass of LiMgPO ₄ powder, or 0.21 ml), and add LiMgPO ₄ dropwise The powder is uniformly ground to form a water-containing mixture. Use a steel mold with an inner hole diameter of 12mm. Before using the mold, use absorbent cotton dipped in anhydrous ethanol to wipe the mold inner wall, ejector and pad respectively. After the mold is dry, put the water-containing mixture into the mold. Use a uniaxial press to apply a pressure of 600 MPa, and heat the mold to 150 °C at a heating rate of 10 °C/min, keep the temperature for 30 min, cool, demold, and take out the sample. The obtained sample was further dried in a drying oven at 120°C for 24 hours to remove residual moisture to obtain a LiMgPO ₄ ceramic material. XRD analysis was carried out on the product prepared in Example 1. As shown in Figure 1, the XRD pattern of the product prepared in Example 1 only contained pure phase, which could be well matched with the standard PDF card (PDF# of the crystal structure database of LiMgPO ₄ ). 32-0574) match, which indicates that Example 1 successfully prepared LiMgPO ₄ microwave ceramic material. The relative density of the product prepared in Example 1 was calculated. As shown in Figure 2, the relative density of the product prepared in Example 1 was 82%. The dielectric constant (ε _r ) of the product prepared in Example 1 was tested. As shown in FIG. 5 , the ε _r of the product prepared in Example 1 was 5.4. The quality factor (Q×f) test was performed on the product prepared in Example 1. As shown in FIG. 8 , the Q×f of the product prepared in Example 1 was 6,900 GHz. The temperature coefficient of resonance frequency (TCF) test was performed on the product prepared in Example 1. As shown in Figure 11, the TCF of the product prepared in Example 1 was -46.1 ppm/°C. As can be seen from the results of the attached drawings, the product prepared in Example 1 has high relative density and good microwave dielectric properties.

Example 2: Preparation of LiMgPO ₄ microwave ceramic samples at 200℃-350MPa-30min

Weigh 1.40 g of LiMgPO ₄ powder, and then add 15% (ie 0.21 ml) of the mass of the powder with deionized water dropwise and add it to the powder and grind it uniformly to form a slurry. Use a steel mold with an inner hole diameter of 12mm. Before using the mold, use absorbent cotton dipped in anhydrous ethanol to wipe the mold inner wall, ejector and pad respectively. After the mold is dry, weigh an appropriate amount of slurry into the mold. In the mold, a uniaxial press was used to apply a pressure of 350 MPa, and the mold was heated to 200 °C at a heating rate of 10 °C/min, kept for 30 min, cooled, demolded, and the sample was taken out. The obtained samples were dried in a drying oven at 120 °C for 24 hours to further remove residual moisture to obtain LiMgPO ₄ ceramic materials. The product prepared in Example 2 is subjected to XRD analysis, as shown in accompanying drawing 1, the XRD pattern of the product prepared in Example 2 shows that it is a pure phase, which can be well matched with the standard PDF card PDF#32-0574 ( LiMgPO ₄ ) match, indicating that Example 2 successfully prepared the LiMgPO ₄ microwave ceramic material. The relative density of the product prepared in Example 2 was calculated. As shown in Figure 2, the relative density of the product prepared in Example 2 was 85%. The dielectric constant (ε _r ) of the product prepared in Example 2 was tested. As shown in FIG. 5 , the ε _r of the product prepared in Example 2 was 5.6. The quality factor (Q×f) test was performed on the product prepared in Example 2. As shown in FIG. 8 , the Q×f of the product prepared in Example 2 was 14,000 GHz. The temperature coefficient of resonance frequency (TCF) test was performed on the product prepared in Example 2. As shown in Figure 11, the TCF of the product prepared in Example 2 was -52.6 ppm/°C. As can be seen from the results of the attached drawings, the product prepared in Example 2 has high relative density and good microwave dielectric properties.

Example 3: Preparation of LiMgPO ₄ microwave ceramic samples at 250℃-600MPa-30min

Weigh 1.40 g of LiMgPO ₄ powder, and then add 15% (ie 0.21 ml) of the mass of the powder with deionized water dropwise and add it to the powder and grind it uniformly to form a slurry. Use a steel mold with an inner hole diameter of 12mm. Before using the mold, use absorbent cotton dipped in anhydrous ethanol to wipe the mold inner wall, ejector and pad respectively. After the mold is dry, weigh an appropriate amount of slurry into the mold. In the mold, a uniaxial press was used to apply a pressure of 600 MPa, and the mold was heated to 250 °C at a heating rate of 10 °C/min, kept for 30 min, cooled, demolded, and the sample was taken out. The obtained samples were dried in a drying oven at 120 °C for 24 hours to further remove residual moisture to obtain LiMgPO ₄ ceramic materials. The product prepared in Example 3 is subjected to XRD analysis, as shown in accompanying drawing 1, the XRD pattern of the product prepared in Example 3 contains only pure phase, which can be well matched with the standard PDF card PDF#32-0574 ( LiMgPO ₄ ) match, indicating that Example 3 successfully prepared the LiMgPO ₄ microwave ceramic material. The relative density of the product prepared in Example 3 was calculated. As shown in Figure 2, the relative density of the product prepared in Example 3 was 90%. The dielectric constant (ε _r ) of the product prepared in Example 3 was tested. As shown in FIG. 5 , the ε _r of the product prepared in Example 2 was 6.1. The quality factor (Q×f) test was performed on the product prepared in Example 3. As shown in FIG. 8 , the Q×f of the product prepared in Example 3 was 12,000 GHz. The temperature coefficient of resonance frequency (TCF) test was carried out on the product prepared in Example 3. As shown in FIG. 11 , the TCF of the product prepared in Example 3 was -56.0 ppm/°C. As can be seen from the results of the accompanying drawings, the product prepared in Example 3 has high relative density and good microwave dielectric properties.

Example 4: Preparation of LiMgPO ₄ microwave ceramic samples at 300℃-600MPa-30min

Weigh 1.40 g of LiMgPO ₄ powder, and then add 15% (ie 0.21 ml) of the mass of the powder with deionized water dropwise and add it to the powder and grind it uniformly to form a slurry. Use a steel mold with an inner hole diameter of 12mm. Before using the mold, use absorbent cotton dipped in anhydrous ethanol to wipe the mold inner wall, ejector and pad respectively. After the mold is dry, weigh an appropriate amount of slurry into the mold. In the mold, a uniaxial press was used to apply a pressure of 600 MPa, and the mold was heated to 300 °C at a heating rate of 10 °C/min, kept for 30 min, cooled, demolded, and the sample was taken out. The obtained samples were dried in a drying oven at 120 °C for 24 hours to further remove residual moisture to obtain LiMgPO ₄ ceramic materials. The product prepared in Example 4 is subjected to XRD analysis, as shown in accompanying drawing 1, the XRD pattern of the product prepared in Example 4 contains only pure phase, which can be well matched with the standard PDF card PDF#32-0574 ( LiMgPO ₄ ) matching, indicating that Example 4 successfully prepared the LiMgPO ₄ microwave ceramic material. The relative density of the product prepared in Example 4 was calculated. As shown in Figure 2, the relative density of the product prepared in Example 4 was 87%. The dielectric constant (ε _r ) of the product prepared in Example 4 was tested. As shown in FIG. 5 , the ε _r of the product prepared in Example 4 was 6.0. The quality factor (Q×f) test was performed on the product prepared in Example 4. As shown in FIG. 8 , the Q×f of the product prepared in Example 4 was 11,000 GHz. The temperature coefficient of resonance frequency (TCF) test was carried out on the product prepared in Example 4. As shown in FIG. 11 , the TCF of the product prepared in Example 4 was -53.6 ppm/°C. As can be seen from the results of the attached drawings, the product prepared in Example 4 has high relative density and good microwave dielectric properties.

Example 5: Preparation of LiMgPO ₄ microwave ceramic samples at 200℃-350MPa-30min

Weigh 1.40 g of LiMgPO ₄ powder, and then add 15% (ie 0.21 ml) of the mass of the powder with deionized water dropwise and add it to the powder and grind it uniformly to form a slurry. Use a steel mold with an inner hole diameter of 12mm. Before using the mold, use absorbent cotton dipped in anhydrous ethanol to wipe the mold inner wall, ejector and pad respectively. After the mold is dry, weigh an appropriate amount of slurry into the mold. In the mold, a uniaxial press was used to apply a pressure of 350 MPa, and the mold was heated to 200 °C at a heating rate of 10 °C/min, kept for 30 min, cooled, demolded, and the sample was taken out. The obtained samples were dried in a drying oven at 120 °C for 24 hours to further remove residual moisture to obtain LiMgPO ₄ ceramic materials. The product prepared in Example 5 is subjected to XRD analysis, and the XRD pattern of the prepared product contains only pure phases. Referring to Example 2 in Figure 1, it can be well matched with the standard crystal structure database PDF card PDF#32-0574 (LiMgPO ₄ ) Matching, indicating that Example 5 successfully prepared the LiMgPO ₄ microwave ceramic material. The relative density of the product prepared in Example 5 was calculated. As shown in Figure 2, the relative density of the product prepared in Example 5 was 85%. The dielectric constant (ε _r ) of the product prepared in Example 5 was tested. As shown in FIG. 5 , the ε _r of the product prepared in Example 5 was 5.6. The quality factor (Q×f) test was performed on the product prepared in Example 5. As shown in FIG. 8 , the Q×f of the product prepared in Example 5 was 14,000 GHz. The temperature coefficient of resonance frequency (TCF) test was carried out on the product prepared in Example 5. As shown in FIG. 11 , the TCF of the product prepared in Example 5 was -50.3 ppm/°C. As can be seen from the results of the attached drawings, the product prepared in Example 5 has high relative density and good microwave dielectric properties.

Example 6: Preparation of LiMgPO ₄ microwave ceramic samples at 200℃-600MPa-60min

Weigh 1.40 g of LiMgPO ₄ powder, and then add 15% (ie 0.21 ml) of the mass of the powder with deionized water dropwise and add it to the powder and grind it uniformly to form a slurry. Use a steel mold with an inner hole diameter of 12mm. Before using the mold, use absorbent cotton dipped in anhydrous ethanol to wipe the mold inner wall, ejector and pad respectively. After the mold is dry, weigh an appropriate amount of slurry into the mold. In the mold, a uniaxial press was used to apply a pressure of 600 MPa, and the mold was heated to 200 °C at a heating rate of 10 °C/min, kept for 60 min, cooled and demolded, and the sample was taken out. The obtained samples were dried in a drying oven at 120 °C for 24 hours to further remove residual moisture to obtain LiMgPO ₄ ceramic materials. The product prepared in Example 7 is subjected to XRD analysis. The XRD pattern of the product prepared in Example 6 contains only pure phase. Referring to Example 2 in Figure 1, it can be well matched with the crystal structure database standard PDF card PDF#32-0574. (LiMgPO ₄ ) matches, indicating that the LiMgPO ₄ microwave ceramic material was successfully prepared in Example 7. The relative density of the product prepared in Example 7 was calculated. As shown in Figure 2, the relative density of the product prepared in Example 6 was 90%. The dielectric constant (ε _r ) of the product prepared in Example 6 was tested. As shown in FIG. 5 , the ε _r of the product prepared in Example 6 was 6.1. The quality factor (Q×f) test was performed on the product prepared in Example 6. As shown in FIG. 8 , the Q×f of the product prepared in Example 6 was 10,000 GHz. The temperature coefficient of resonance frequency (TCF) test was performed on the product prepared in Example 4. As shown in FIG. 11 , the TCF of the product prepared in Example 4 was -55.8 ppm/°C. As can be seen from the results of the attached drawings, the product prepared in Example 6 has high relative density, good microwave dielectric properties, is compatible with silver electrodes, and has application prospects in devices.

Example 7: Preparation of LiMgPO ₄ microwave ceramic samples at 250℃-600MPa-60min

Weigh 1.40 g of LiMgPO ₄ powder, and then add 15% (ie 0.21 ml) of the mass of the powder with deionized water dropwise and add it to the powder and grind it uniformly to form a slurry. Use a steel mold with an inner hole diameter of 12mm. Before using the mold, use absorbent cotton dipped in anhydrous ethanol to wipe the mold inner wall, ejector and pad respectively. After the mold is dry, weigh an appropriate amount of slurry into the mold. In the mold, a uniaxial press was used to apply a pressure of 600 MPa, and the mold was heated to 250 °C at a heating rate of 10 °C/min, kept for 60 min, cooled, demolded, and the sample was taken out. The obtained samples were dried in a drying oven at 120 °C for 24 hours to further remove residual moisture to obtain LiMgPO ₄ ceramic materials. The product prepared in Example 7 was subjected to XRD analysis. As shown in Figure 1, the XRD pattern of the product prepared in Example 8 contained only pure phase, which could be well matched with the crystal structure database standard PDF card PDF#32-0574 (LiMgPO ₄ ) match, indicating that the example successfully prepared LiMgPO ₄ microwave ceramic material. The relative density of the product prepared in Example 7 was calculated. As shown in Figure 3, the relative density of the product prepared in Example 8 was 93.%. The dielectric constant (ε _r ) of the product prepared in Example 8 was tested. As shown in FIG. 6 , the ε _r of the product prepared in Example 7 was 6.5. The quality factor (Q×f) test was performed on the product prepared in Example 8. As shown in FIG. 9 , the Q×f of the product prepared in Example 7 was 16,000 GHz. The temperature coefficient of resonance frequency (TCF) test was performed on the product prepared in Example 7. As shown in Figure 12, the TCF of the product prepared in Example 7 was -58.0 ppm/°C. As can be seen from the results of the attached drawings, the product prepared in Example 7 has high relative density and good microwave dielectric properties.

Example 8: Preparation of LiMgPO ₄ microwave ceramic samples at 250℃-600MPa-90min

Weigh 1.40 g of LiMgPO ₄ powder, and then add 15% (ie 0.21 ml) of the mass of the powder with deionized water dropwise and add it to the powder and grind it uniformly to form a slurry. Use a steel mold with an inner hole diameter of 12mm. Before using the mold, use absorbent cotton dipped in anhydrous ethanol to wipe the mold inner wall, ejector and pad respectively. After the mold is dry, weigh an appropriate amount of slurry into the mold. In the mold, a uniaxial press was used to apply a pressure of 600 MPa, and the mold was heated to 250 °C at a heating rate of 10 °C/min, kept for 90 min, cooled, demolded, and the sample was taken out. The obtained samples were dried in a drying oven at 120 °C for 24 hours to further remove residual moisture to obtain LiMgPO ₄ ceramic materials. The product prepared in Example 10 was subjected to XRD analysis. As shown in Figure 1, the XRD pattern of the product prepared in Example 8 contained only pure phases, which could be well matched with the crystal structure database standard PDF card PDF#32-0574 (LiMgPO ₄ ) Matching, indicating that Example 8 successfully prepared the LiMgPO ₄ microwave ceramic material. The relative density of the product prepared in Example 9 was calculated. As shown in Figure 3, the relative density of the product prepared in Example 8 was 89%. The dielectric constant (ε _r ) of the product prepared in Example 9 was tested. As shown in FIG. 6 , the ε _r of the product prepared in Example 8 was 6.2. The quality factor (Q×f) test was performed on the product prepared in Example 8. As shown in FIG. 9 , the Q×f of the product prepared in Example 8 was 3,600 GHz. The temperature coefficient of resonance frequency (TCF) test was performed on the product prepared in Example 8. As shown in FIG. 12 , the TCF of the product prepared in Example 8 was -47.0 ppm/°C. As can be seen from the results of the attached drawings, the product prepared in Example 8 has high relative density and good microwave dielectric properties.

Example 9: Preparation of LiMgPO ₄ microwave ceramic sample of 200℃-600MPa-30min-acetic acid

Weigh 1.40 g of LiMgPO ₄ powder, and add 15% (ie 0.21 ml) of acetic acid of the mass of the powder into the powder and grind it uniformly to form a slurry. Use a steel mold with an inner hole diameter of 12mm. Before using the mold, use absorbent cotton dipped in anhydrous ethanol to wipe the mold inner wall, ejector and pad respectively. After the mold is dry, weigh an appropriate amount of slurry into the mold. In the mold, a uniaxial press was used to apply a pressure of 600 MPa, and the mold was heated to 200 °C at a heating rate of 10 °C/min, kept for 30 min, cooled, demolded, and the sample was taken out. The obtained samples were dried in a drying oven at 120 °C for 24 hours to further remove residual moisture to obtain LiMgPO ₄ ceramic materials. The product prepared in Example 6 is subjected to XRD analysis. The XRD pattern of the product prepared in Example 9 contains only pure phase. Referring to Example 3 in Figure 1, it can be well matched with the standard crystal structure database PDF card PDF#32-0574. (LiMgPO ₄ ) match, indicating that Example 6 successfully prepared LiMgPO ₄ microwave ceramic material. The relative density of the product prepared in Example 6 was calculated. As shown in Figure 4, the relative density of the product prepared in Example 9 was 89%. The dielectric constant (ε _r ) of the product prepared in Example 9 was tested. As shown in FIG. 7 , the ε _r of the product prepared in Example 6 was 6.1. The quality factor (Q×f) test was performed on the product prepared in Example 9. As shown in FIG. 10 , the Q×f of the product prepared in Example 9 was 11,000 GHz. The temperature coefficient of resonance frequency (TCF) test was performed on the product prepared in Example 9. As shown in FIG. 13 , the TCF of the product prepared in Example 9 was -54.9 ppm/°C. As can be seen from the results of the accompanying drawings, the product prepared in Example 9 has high relative density and good microwave dielectric properties.

Example 10: Preparation of LiMgPO ₄ microwave ceramic sample of 250℃-600MPa-60min-acetic acid

Weigh 1.40 g of LiMgPO ₄ powder, and then take 15% of the mass of the powder (ie, 0.21 ml) of acetic acid solvent dropwise into the powder and grind it uniformly to form a slurry. Use a steel mold with an inner hole diameter of 12mm. Before using the mold, use absorbent cotton dipped in anhydrous ethanol to wipe the mold inner wall, ejector and pad respectively. After the mold is dry, weigh an appropriate amount of slurry into the mold. In the mold, a uniaxial press was used to apply a pressure of 600 MPa, and the mold was heated to 250 °C at a heating rate of 10 °C/min, kept for 60 min, cooled, demolded, and the sample was taken out. The obtained samples were dried in a drying oven at 120 °C for 24 hours to further remove residual moisture to obtain LiMgPO ₄ microwave ceramic materials. The product prepared in Example 10 is subjected to XRD analysis. The XRD pattern of the product prepared in Example 10 contains only pure phases. Referring to Example 7 in Figure 1, it can be well matched with the crystal structure database standard PDF card PDF#32-0574. (LiMgPO ₄ ) matches, indicating that the LiMgPO ₄ microwave ceramic material was successfully prepared in Example 9. The relative density of the product prepared in Example 10 was calculated. As shown in FIG. 4 , the relative density of the product prepared in Example 10 was 93%. The dielectric constant (ε _r ) of the product prepared in Example 9 was tested. As shown in FIG. 7 , the ε _r of the product prepared in Example 10 was 6.5. The quality factor (Q×f) test was performed on the product prepared in Example 10. As shown in FIG. 10 , the Q×ff of the product prepared in Example 10 was 15,000 GHz. The temperature coefficient of resonance frequency (TCF) test was performed on the product prepared in Example 10. As shown in Figure 13, the TCF of the product prepared in Example 10 was -59.5 ppm/°C. As can be seen from the results of the accompanying drawings, the product prepared in Example 10 has high relative density and good microwave dielectric properties.

Example 11: Preparation of LiMgPO ₄ microwave ceramic samples of 250℃-600MPa-90min-acetic acid

Weigh 1.40 g of LiMgPO ₄ powder, and then take 15% of the mass of the powder (ie, 0.21 ml) of acetic acid solvent dropwise into the powder and grind it uniformly to form a slurry. Use a steel mold with an inner hole diameter of 12mm. Before using the mold, use absorbent cotton dipped in anhydrous ethanol to wipe the mold inner wall, ejector and pad respectively. After the mold is dry, weigh an appropriate amount of slurry into the mold. In the mold, a uniaxial press was used to apply a pressure of 600 MPa, and the mold was heated to 250 °C at a heating rate of 10 °C/min, kept for 90 min, cooled, demolded, and the sample was taken out. The obtained samples were dried in a drying oven at 120 °C for 24 hours to further remove residual moisture to obtain LiMgPO ₄ ceramic materials. XRD analysis was carried out on the product prepared in Example 11. The XRD pattern of the product prepared in Example 11 contained only pure phase. Referring to Example 8 in Figure 1, it can be well matched with the crystal structure database standard PDF card PDF#32-0574. (LiMgPO ₄ ) matches, indicating that Example 11 successfully prepared LiMgPO ₄ microwave ceramic materials. The relative density of the product prepared in Example 11 was calculated. As shown in FIG. 4 , the relative density of the product prepared in Example 11 was 80%. The dielectric constant (ε _r ) of the product prepared in Example 9 was tested. As shown in FIG. 7 , the ε _r of the product prepared in Example 11 was 5.1. The quality factor (Q×f) test was performed on the product prepared in Example 11. As shown in FIG. 10 , the Q×f of the product prepared in Example 11 was 10,000 GHz. The temperature coefficient of resonance frequency (TCF) test was performed on the product prepared in Example 11. As shown in Figure 13, the TCF of the product prepared in Example 11 was -49.0 ppm/°C. As can be seen from the results of the accompanying drawings, the product prepared in Example 11 has high relative density and good microwave dielectric properties.

The descriptions of the above embodiments are only used to help understand the method and the 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, several improvements and modifications can also 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 enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to 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 (2)

1. Low-temperature energy-saving preparation of L iMgPO₄The microwave ceramic material is prepared with L iMgPO₄Mixing with water or acetic acid not higher than 20 wt% to form a solid-liquid mixture, compacting by hot pressing at 150 deg.C, 200 deg.C, 250 deg.C or 300 deg.C, 30min, 60min or 90min, and applying pressure (P) to obtain L iMgPO₄Ceramic having a dielectric constant of_r) The range is 5.1 to 6.5, the range of the quality factor Q × f is 3,600GHz to 16,000GHz, and the range of the temperature coefficient of resonance frequency (TCF) is-46.1 ppm/DEG C to-59.5 ppm/DEG C.

2. The method of claim 1, comprising the steps of:

(1) the ingredients are firstly mixed according to the chemical formula of L iMgPO₄The stoichiometric ratio of L i, Mg and P elements in the raw materials is L i₂CO₃(purity 99.99%), (MgCO)₃)₄˙Mg(OH)₂˙5H₂O (purity 99.99%) and NH₄H₂PO₄(purity 99.99%);

(2) mixing materials: pouring the raw materials into a ball milling tank, using isopropanol as a ball milling medium, and carrying out ball milling and mixing for 4 hours to obtain a slurry raw material;

(3) drying: pouring out the ball-milled slurry, and drying in an oven at 80 ℃ to obtain dry powder of the mixture;

(4) calcining, namely calcining the mixture dry powder obtained in the previous step in a high-temperature furnace for 4 hours at the presintering temperature of 500 ℃, and calcining the obtained powder for 4 hours at the temperature of 800 ℃ to obtain the final L iMgPO₄Block, grinding and sieving with 300 mesh nylon sieve;

(5) mixing materials, weighing L iMgPO₄Adding 15 wt% of deionized water into the powder, and uniformly mixing to form a dough-like aqueous mixture;

(6) and (3) low-temperature sintering: placing the water-containing mixture obtained in the last step into a shape mould, moving the mould into a hot press, heating to a certain sintering temperature point of not more than 300 ℃, applying 600MPa pressure to the mould, and carrying out hot pressing for 30, 60 and 90 minutes to obtain densified ceramic;

(7) drying, namely further drying the densified ceramic sample obtained in the last step in a drying oven at the temperature of 120 ℃ for 24 hours to remove residual moisture to obtain L iMgPO₄And (5) obtaining a ceramic finished product.

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