A low-temperature and low-dielectric-loss microwave dielectric ceramic CoTeMoO 6 and its preparation method

Abstract

The present invention belongs to the field of microwave dielectric ceramic materials, and specifically discloses a low-temperature and low-dielectric-loss microwave dielectric ceramic CoTeMoO6 and a preparation method thereof. Based on the traditional solid-phase method, CoTeMoO6 ceramics with ultra-low loss are synthesized under the condition of ultra-low temperature sintering (only 500-620 °C). This not only significantly reduces energy consumption, but also remarkably shortens the overall cycle from material preparation to finished product; the adoption of this low-temperature sintering technology makes the entire production process more efficient and fast, with a short production cycle, improving production efficiency and reducing production costs; the CoTeMoO6 ceramics prepared by the present invention have good microwave dielectric properties: relative dielectric constant ε r = 11.36-13.88, quality factor and frequency product Q×f = 6849-44110 GHz, temperature coefficient τ f = -90.8-72.4 ppm / °C, and these characteristics provide the possibility for its application in microwave devices.

Description

Technical Field

[0001] The present invention relates to the field of microwave dielectric ceramic materials, in particular to a low-temperature and low-dielectric-loss microwave dielectric ceramic CoTeMoO 6 and a preparation method thereof. Background Art

[0002] ULTCC technology (Ultra Low Temperature Co-fired Ceramics) is a new type of multilayer ceramic technology. With its unique advantages of ultra-low temperature sintering, this technology not only significantly reduces energy consumption and production costs, but also greatly broadens the integration possibilities of conductor materials and semiconductor components. The wide application of ULTCC technology, from sophisticated wireless communication equipment to complex automotive electronic systems to the demanding aerospace field, has demonstrated its unparalleled performance advantages. In the field of communications, ULTCC components have become key components for improving communication efficiency and quality with their high-frequency characteristics and low-loss performance. They are widely used in core components such as filters and antennas, providing strong support for high-speed data transmission and long-distance communication. In the field of automotive electronics, ULTCC technology provides a reliable solution for the manufacture of automotive electronic components with its excellent high temperature resistance, vibration resistance and corrosion resistance. In the field of aerospace, ULTCC technology has become one of the key technologies in the manufacture of aerospace electronic equipment with its outstanding performance and wide range of applications. With its unique advantages and broad application prospects, ULTCC technology is gradually becoming an important force in promoting the development of the electronic component manufacturing industry. With the continuous advancement of technology and the continuous expansion of the market, ULTCC technology will surely usher in a broader development space and a more brilliant future.

[0003] In the current field of microwave dielectric ceramic material preparation, although many advances have been made, traditional methods generally face the challenge of high sintering temperatures. High-temperature sintering not only consumes a lot of energy, but may also affect the microstructure and final performance of the material. Therefore, exploring low-temperature sintering technology to reduce energy consumption and optimize material performance has become a research hotspot in this field. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a low-temperature and low-dielectric-loss microwave dielectric ceramic CoTeMoO 6 and a preparation method thereof.

[0005] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0006] One of the purposes of the present invention is to provide a low temperature and low dielectric loss microwave dielectric ceramic CoTeMoO 6 The preparation method comprises the following steps:

[0007] S1, taking cobalt monoxide powder, tellurium dioxide powder and molybdenum trioxide powder in a molar ratio of 1:1:1, and mixing them uniformly to obtain a mixed powder A;

[0008] S2, adding the mixed powder A into deionized water, and performing the first ball milling to obtain a mixed slurry A;

[0009] S3, drying the mixed slurry A, and passing it through a 40-80 mesh sieve after drying to obtain granular powder of a suitable size, thereby obtaining a mixed powder B;

[0010] S4, heating the mixed powder B to 400°C and pre-sintering for 5.5-6 hours to obtain mixed powder C;

[0011] S5, adding the mixed powder C into deionized water, and performing a second ball milling to obtain a mixed slurry B, drying the mixed slurry B, and passing it through a 40-80 mesh sieve after drying to remove large particles of impurities, thereby obtaining a mixed powder D;

[0012] S6, adding 8 wt % of PVA adhesive to the mixed powder D, grinding thoroughly until uniformly mixed, and passing through an 80-110 mesh sieve to obtain a mixed powder E; pressing the mixed powder E into a shape;

[0013] S7, after the formed block is allowed to stand at room temperature for 8-10 hours, it is placed in a sintering furnace, heated to 480°C, and maintained for 6 hours to volatilize the PVA adhesive; then, the temperature is continued to be raised to 500-620°C and sintered for 2-4 hours, and then cooled to room temperature with the furnace to obtain a low-temperature and low-dielectric-loss microwave dielectric ceramic CoTeMoO 6 .

[0014] Furthermore, the particle sizes of the cobalt monoxide powder, tellurium dioxide powder and molybdenum trioxide powder are all 350-400 meshes, and the purity of the cobalt monoxide powder, tellurium dioxide powder and molybdenum trioxide powder are all 99.0%-99.95%.

[0015] Furthermore, during the first and second ball milling, an appropriate amount of deionized water is added to the ball mill to fully wet the powder, and the powder is allowed to stand for 15-18 hours to promote water penetration between particles; after the gas in the tank is removed, the ball mill is started for 20-24 hours of continuous ball milling to obtain a fine and uniform slurry.

[0016] Preferably, the mixed slurry A and the mixed slurry B are both dried at 80-95°C.

[0017] Preferably, in step S4, heating is performed to 400° C. at a heating rate of 5° C. / min.

[0018] Preferably, in step S6, the material is pressed into a cylindrical block at a pressure of 2 bar.

[0019] Preferably, in the step S7, the sintering temperature is 560 - 600 °C.

[0020] The second object of the present invention is to provide a low-temperature and low-dielectric-loss microwave dielectric ceramic CoTeMoO prepared by the above method 6 .

[0021] Compared with the prior art, on the basis of the traditional solid-phase method, the present invention synthesizes CoTeMoO with ultra-low loss under the condition of ultra-low temperature sintering (only 500 - 620 °C), which not only greatly reduces the energy consumption, but also significantly shortens the overall cycle from material preparation to finished product; the adoption of this low-temperature sintering technology makes the whole production process more efficient and fast, with a short production cycle, improves the production efficiency and reduces the production cost; the CoTeMoO ceramic prepared by the present invention has good microwave dielectric properties: the relative dielectric constant ε 6 = 11.36 - 13.88, the product of quality factor and frequency Q×f = 6849 - 44110 GHz, and the temperature coefficient τ 6 = -90.8 - 72.4 ppm / °C, and these characteristics provide the possibility for its application in microwave devices. r f Description of the Drawings

[0022] Figure 1 It is the X-ray diffraction (XRD) pattern analysis of CoTeMoO 6 ceramic materials at different sintering temperatures in the range of 500 °C to 620 °C.

[0023] Figure 2 It is the SEM microstructural image of CoTeMoO 6 ceramic at the sintering temperature of 500 - 620 °C and the Gaussian fitting curve of its grain size distribution.

[0024] Figure 3 It is the trend of the change of the apparent density and relative density of CoTeMoO 6 ceramic materials in the sintering temperature range of 500 °C to 620 °C. Detailed Embodiments

[0025] In order to make the objects, technical solutions and advantages of the present invention clearer, the following examples are used to further explain the present invention in detail. The specific examples described here are only used to explain the present invention and are not used to limit the invention.

[0026] The test methods in the following examples are all conventional methods unless otherwise specified. Unless otherwise specified, the reagents and materials used can all be obtained through commercial channels.

[0027] Example 1

[0028] I. Raw material selection and mixing

[0029] Raw material selection: Select CoO powder (purity 99.95%) within the particle size range of 350 - 400 mesh, TeO 2 powder (purity 99.9%) and MoO 3 powder (purity 99.9%).

[0030] Ratio and mixing: Weigh CoO powder, tellurium TeO 2 powder and molybdenum MoO 3 powder in a molar ratio of 1:1:1, mix them evenly, and transfer them to a ball mill tank for standby.

[0031] II. Wet grinding refinement and pre - sintering treatment

[0032] Wet grinding preparation: Add an appropriate amount of deionized water to the ball mill tank to fully soak the powder, and let it stand for 15 - 18 hours to promote the penetration of moisture between particles.

[0033] Ball milling refinement: After exhausting the gas in the tank, start the ball mill for continuous ball milling for 20 - 24 hours to obtain a delicate and uniform slurry.

[0034] Drying and screening: Pour out the slurry, place it in an environment of 80 - 95 °C to dry to an appropriate humidity, and then screen it through a 40 - 80 - mesh sieve to obtain particles of appropriate size.

[0035] Pre - sintering: Place the screened powder in a muffle furnace, slowly heat it to 400 °C at a heating rate of 5 °C / min, and pre - sinter it at this temperature for 5.5 - 6 hours to initially promote the chemical reaction between powders and particle rearrangement.

[0036] Secondary ball milling and drying: After the pre - sintering is completed, mix the powder with deionized water again, conduct secondary ball milling for 20 - 24 hours, and then dry and screen (80 - 110 mesh) to obtain a more delicate raw material to be formed.

[0037] III. Molding and low - temperature sintering

[0038] Molding preparation: Add 8 wt% PVA binder to the screened powder, grind it thoroughly until evenly mixed, and screen it again through an 80 - 110 - mesh sieve to ensure the fineness and fluidity of the powder.

[0039] Press molding: Place the treated raw material powder in a mold and press it into a cylindrical block with a diameter of 11.7 mm and a height of 5.45 mm under a pressure of 2 bar.

[0040] Static drying: Let the pressed blocks stand at room temperature for 8 - 10 hours to drain the excess moisture on the surface and inside.

[0041] Ultra - low - temperature sintering: Put the dried blocks into a sintering furnace. First, heat them at a heating rate of 5 °C / min to 480 °C and hold for 6 hours to volatilize the PVA binder. Subsequently, continue to heat to the range of 500 - 620 °C and sinter for 3 hours to densify the blocks and complete the phase transformation at high temperature. Then, cool them to room temperature with the furnace to obtain CoTeMoO 6 Ceramic sample 1.

[0042] Example 2

[0043] The difference from Example 1 is that the sintering temperature is 520 °C, and CoTeMoO 6 Ceramic sample 2 is obtained.

[0044] Example 3

[0045] The difference from Example 1 is that the sintering temperature is 540 °C, and CoTeMoO 6 Ceramic sample 3 is obtained.

[0046] Example 4

[0047] The difference from Example 1 is that the sintering temperature is 560 °C, and CoTeMoO 6 Ceramic sample 4 is obtained.

[0048] Example 5

[0049] The difference from Example 1 is that the sintering temperature is 580 °C, and CoTeMoO 6 Ceramic sample 5 is obtained.

[0050] Example 6

[0051] The difference from Example 1 is that the sintering temperature is 600 °C, and CoTeMoO 6 Ceramic sample 6 is obtained.

[0052] Example 7

[0053] The difference from Example 1 is that the sintering temperature is 620 °C, and CoTeMoO 6 Ceramic sample 7 is obtained.

[0054] Respectively, X - ray diffraction (XRD) pattern analysis was carried out on the CoTeMoO 6 ceramic samples prepared in Examples 1 - 7, and the results are as Figure 1 shown. As can be seen from Figure 1 CoTeMoO 6At sintering temperatures from 500 °C to 620 °C, the main diffraction peaks of the ceramic highly match the standard card PDF#01-089-8181, which conclusively proves the successful synthesis of CoTeMoO with an orthorhombic structure (space group P2 1 2 1 2(18)) crystal phase during the sintering process. However, minor diffraction peaks that match the CoMoO 6 (PDF#01-071-2505) phase also appear in the pattern, revealing that a certain amount of CoMoO 4 secondary phase is inevitably generated during the synthesis process. 4 The presence of this secondary phase is a notable phenomenon as it may have a significant impact on the airtightness characteristics of the final ceramic sample. Specifically, the presence of the CoMoO

[0055] phase may increase the porosity or interfacial defects in the ceramic material, and these factors are usually closely related to the deterioration of dielectric properties, especially the increase in dielectric loss. Therefore, when preparing CoTeMoO 4 ceramics, optimizing the sintering conditions to reduce or eliminate the formation of the CoMoO 6 secondary phase is crucial for improving the airtightness of the ceramic and reducing dielectric loss. 4 Furthermore, scanning electron microscopy (SEM) scans were respectively performed on the CoTeMoO

[0056] ceramic samples prepared in Examples 1 - 7, and the SEM images are as shown in 6 . Figure 2 As can be seen from (a) in

[0057] , the microstructure characteristics of CoTeMoO Figure 2 ceramic sample 1, that is, the grain size is relatively small, and the average grain size (A.G.) is only 0.204 μm, indicating that the current sintering degree has not reached the optimal state and there is still room for further improvement. 6 From the SEM image of (b) in Figure 2 , it can be observed that in CoTeMoO 6 ceramic sample 2, with the increase of the sintering temperature, obvious grain growth behavior occurs. This phenomenon may indicate a reduction in the number of grain boundaries inside the material, because the increase in grain size is usually accompanied by the merger and reduction of grain boundaries. The measured average grain size (A.G.) is 0.423 μm, which is increased compared with the previous observation results, further confirming the trend of grain growth. Figure 2 In (c) of 6 is the SEM image of CoTeMoO Figure 2CoTeMoO presented in (d) 6 The SEM image of ceramic sample 4 clearly shows the microstructure of the ceramic in this example. The grain morphology is relatively prominent and the distribution is relatively uniform. The measured average grain size reaches 0.66 μm. This result not only indicates the effective growth of grains during sintering, but also implies that the material may have good crystallinity and low porosity inside, which may have a positive impact on the physical and dielectric properties of the ceramic. Figure 2 In the SEM image of (e), it can be directly observed that CoTeMoO 6 For ceramic sample 5, the grain size distribution is uniform, the number of pores is significantly reduced, the sintered body has high density, and the average grain size is measured to be 0.73 μm. Figure 2 In the SEM image of the ceramic shown in (f), CoTeMoO 6 The growth state of the grains in ceramic sample 6 shows a certain degree of non-uniformity, which indicates that there may be local differences in the grain growth rate or conditions during sintering. Nevertheless, overall, the average grain size reaches 0.933 μm, showing the significant influence of the sintering process on grain growth. However, the non-uniform grain growth may affect some properties of the material and may deteriorate the dielectric properties of the ceramic sample. Figure 2 In the SEM image of the ceramic shown in (g), CoTeMoO 6 The average grain size of ceramic sample 7 reaches 0.973 μm. However, it is worth noting that due to the too high sintering temperature, some grains show abnormal overgrowth, resulting in non-uniform grain size distribution. This non-uniform grain growth not only affects the aesthetics of the material microstructure, but more importantly, the number of pores between grains increases significantly. These pores exist as defects and are very likely to be the source of dielectric loss, having an adverse impact on the dielectric properties of the ceramic. In Figure 2 In (h), the grain size of the sample increases from 0.204 μm to 0.977 μm, indicating that the sintering temperature can promote grain growth.

[0058] Furthermore, the characterized density and relative density of the CoTeMoO 6 ceramic samples prepared in Examples 1 - 7 were detected respectively, and the results are as Figure 3 shown.

[0059] From Figure 3 it can be seen that for CoTeMoO 6 ceramic sample 1, the characterized density ρ = 4.885 g / cm 3 ; the relative density ρ re = 89.7%; for CoTeMoO 6 ceramic sample 2, the characterized density ρ reaches 4.95 g / cm 3, relative density ρ re also increased to 90.72%, compared with CoTeMoO 6 ceramic sample 1, the compactness has been significantly improved. This change indicates that by adjusting the sintering temperature, not only the grain growth is promoted, but also the microstructure of the material is optimized, improving its density; CoTeMoO 6 The apparent density ρ of ceramic sample 3 is 5.017 g / cm 3 , relative density ρ re = 92.25%; CoTeMoO 6 The apparent density ρ of ceramic sample 4 is 5.13 g / cm 3 , relative density ρ re = 93.65%, and the compactness is significantly improved; CoTeMoO 6 The compactness of ceramic sample 5 reaches the highest level, with an apparent density ρ = 5.247 g / cm 3 , relative density ρ re even as high as 95.94%, indicating that the internal structure of the material is tight and the porosity is low. This high-density characteristic indicates that the material may have low dielectric loss; CoTeMoO 6 The apparent density ρ of ceramic sample 6 is 5.13 g / cm 3 , relative density ρ re = 93.82%, and the compactness of the sample decreases; CoTeMoO 6 The apparent density ρ of ceramic sample 7 decreases to 4.99 g / cm 3 , relative density ρ re also decreases to 91.34%, indicating that the compactness of the ceramic has decreased. It indicates that the dielectric properties of the ceramic may have deteriorated because defects such as pores will intensify the scattering and absorption of electromagnetic waves in the material, thereby increasing the dielectric loss.

[0060] Finally, the dielectric properties of the CoTeMoO 6 ceramic samples prepared in Examples 1-7 were detected respectively, and the detection results are shown in Table 1.

[0061] Table 1

[0062]

[0063] In summary, when the sintering temperature is set in the range of 560 - 600 °C, the performance of CoTeMoO 6 ceramics is particularly prominent. The optimal sintering temperature is 580 °C, and this sintering temperature enables the ceramic material to reach the optimal state in terms of dielectric properties.

[0064] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A method for preparing low-temperature and low-dielectric-loss microwave dielectric ceramic CoTeMoO6, characterized in that: The following steps are involved: S1, taking cobalt monoxide powder, tellurium dioxide powder and molybdenum trioxide powder with a particle size of 350-400 mesh and a purity of 99.0%-99.95% in a molar ratio of 1:1:1, and mixing them uniformly to obtain a mixed powder A; S2. Add the mixed powder A into deionized water and perform the first ball milling to fully wet the powder. Let it stand for 15-18 hours to promote water penetration between particles. After removing the gas in the tank, start the ball mill for 20-24 hours of continuous ball milling to obtain a fine and uniform mixed slurry A. S3, drying the mixed slurry A, and passing it through a 40-80 mesh sieve after drying to obtain a mixed powder B; S4, heating the mixed powder B to 400°C and pre-sintering for 5.5-6 hours to obtain mixed powder C; S5, adding the mixed powder C to deionized water, and performing a second ball milling to fully infiltrate the powder, and standing for 15-18 hours to promote water penetration between particles; after removing the gas in the tank, starting the ball mill for 20-24 hours of continuous ball milling to obtain a fine and uniform mixed slurry B, and drying the mixed slurry B, and after drying, passing it through a 40-80 mesh sieve to obtain a mixed powder D; S6. Add 8 wt % of PVA adhesive to the mixed powder D, grind thoroughly until uniformly mixed, and pass through an 80-110 mesh sieve to obtain a mixed powder E; press the mixed powder E into a shape; S7. After the formed block is allowed to stand at room temperature for 8-10 hours, it is placed in a sintering furnace, heated to 480°C, and maintained for 6 hours to volatilize the PVA adhesive; then, the temperature is continued to be raised to 580°C and sintered for 2-4 hours, and the furnace is cooled to room temperature to obtain a low-temperature and low-dielectric-loss microwave dielectric ceramic CoTeMoO6.

2. The method for preparing the low-temperature and low-dielectric-loss microwave dielectric ceramic CoTeMoO6 according to claim 1, characterized in that: The mixed slurry A and the mixed slurry B are both dried at 80-95°C.

3. The method for preparing the low-temperature and low-dielectric-loss microwave dielectric ceramic CoTeMoO6 according to claim 1, characterized in that: In the step S4, heating is performed to 400° C. at a heating rate of 5° C. / min.

4. The method for preparing the low-temperature and low-dielectric-loss microwave dielectric ceramic CoTeMoO6 according to claim 1, characterized in that: In the step S6, the material is pressed into a cylindrical block at a pressure of 2 bar.

5. A low-temperature, low-dielectric-loss microwave dielectric ceramic CoTeMoO6 prepared by the method according to any one of claims 1 to 4.

Images