A high-temperature resistant, high-absorption ceramic superatom and its preparation method

Abstract

This invention discloses a high-temperature resistant, high-absorption ceramic superatom and its preparation method. The high-temperature resistant, high-absorption ceramic superatom is obtained by high-precision wire cutting of millimeter-wave dielectric ceramic, the composition of which is Ba4Nd. 9.33‑ x Sm x Ti 18‑y Co y O 54‑δ In the formula, x is 3-6, y is 2-3, and δ is 1-1.5. The ceramic superatomic structure provided by this invention is simple and compact, with high temperature stability and tolerance. It is compatible with metamaterial absorbers of different millimeter-wave frequencies and can meet the application requirements of miniaturization, multi-scenario, and especially extreme scenarios of current millimeter-wave technology.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, specifically relating to a high-temperature resistant, high-absorption ceramic superatom and its preparation method. Background Technology

[0002] Metamaterial absorbers have broad application prospects in microwave / millimeter-wave electromagnetic shielding, detection, and imaging. In recent years, with the continuous increase in mobile communication frequencies and the increasing complexity of application environments, ceramic-based metamaterials have attracted widespread attention due to their high reliability and subwavelength response characteristics. The rise of this type of metamaterial has provided a new approach to the development of metamaterial absorbers and is expected to further promote the expansion of metamaterial device application scenarios.

[0003] Currently, the theoretical basis of ceramic-based metamaterial absorbers is the Mie resonance theory and the effective medium theory. High dielectric constant (typically above 100) oxide dielectric ceramics (such as TiO2, SrTiO3, and CaTiO3) are used to prepare particles (ceramic superatoms) to construct metamaterial arrays. Furthermore, based on the 50% load absorption power limit of transmission line theory, perfect absorption is achieved using a reflective backplane mirroring method. However, due to design limitations and the inherent properties of the materials, these ceramic superatoms often exhibit significant temperature drift. The low absorption of ordinary temperature-stable ceramics results in a large period for the metamaterial absorber (typically several times the size of the superatom), which cannot meet the requirements of highly integrated applications such as millimeter-wave Massive MIMO (MIMO) compact antenna arrays, nor can it cope with the complex multi-application requirements of today, such as high-temperature environments.

[0004] Based on the above situation, there is an urgent need to develop new high-temperature resistant and high-absorption ceramic superatoms to match future high-performance metamaterial absorbers. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature resistant, high-absorption ceramic superatom and its preparation method. This ceramic superatom has a simple structure, exhibits absorption close to the theoretical limit of 50%, and good temperature stability. It can effectively expand the high-temperature application scenarios of ceramic-based metamaterial absorbers, while significantly reducing their periodic size, and is expected to be applied in many passive devices such as millimeter-wave large-scale MIMO compact antenna arrays.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] First, based on the impedance matching relationship of the S-parameters, parametric scanning is performed using COMSOL multiphysics simulation software. The approximation relationship between the effective impedance of the S-parameters and the air impedance (approximately 1) is statistically analyzed (the closer to 1, the better), thereby designing and obtaining the desired ceramic material properties.

[0008] Furthermore, according to one embodiment of the present invention, preferably, a millimeter-wave dielectric ceramic for high-temperature resistant, high-absorption ceramic superatoms is prepared, the composition formula of which is Ba4Nd. 9.33-x Sm x Ti 18-y Co y O 54-δ In the formula, x is 3-6, y is 2-3, and δ is 1-1.5; preferably, x is 3-5, specifically 3, 3.5, 4, 4.5 or 5, y is 2.3, 2.5, 2.7 or 2.9, and δ is 1.15, 1.25, 1.35 or 1.45.

[0009] This invention also provides a method for preparing the above-mentioned high-temperature resistant, high-absorption ceramic superatomic millimeter-wave dielectric ceramic, comprising the following steps:

[0010] 1) Mix BaCO3, Sm2O3, Nd2O3, TiO2, and Co2O3 according to the chemical formula Ba4Nd 9.33-x Sm x Ti 18-y Co y O 54-δ Weigh the required raw materials, mix the weighed materials, ball mill, dry, pulverize, and sieve them, then pre-calcine to initially synthesize a single-phase tungsten bronze structure Ba4Nd. 9.33-x Sm x Ti 18-y Co y O 54-δ Dielectric ceramic powder;

[0011] 2) The powder obtained in step 1) is added to polyvinyl butyral and then ball-milled, dried, pulverized and sieved, and then pressed into cylindrical ceramic green bodies using an automatic tablet press.

[0012] 3) Sinter the ceramic green body obtained in step 2) to obtain the millimeter-wave dielectric ceramic.

[0013] Preferably, in step 1), the ball milling further includes adding zirconium oxide balls and anhydrous ethanol for ball milling; the ball milling speed is 400 rpm and the ball milling time is 4-10 h.

[0014] Preferably, in step 1), the drying temperature is 80°C; the sieving process involves first passing the material through a 40-mesh sieve and then through an 80-mesh sieve.

[0015] Preferably, the pre-sintering temperature in step 1) is 1100-1190℃, and the pre-sintering time is 5-8h.

[0016] Preferably, the amount of polyvinyl butyral added in step 2) is 0.9%-1.2% of the powder mass.

[0017] Preferably, the ball milling time in step 2) is 10-14 hours.

[0018] Preferably, the sieving in step 2) is sieving through an 80-mesh sieve.

[0019] Preferably, the ceramic green body in step 2) has a diameter of 10 mm and a thickness of 5 mm.

[0020] Preferably, in step 3), the sintering conditions are sintering at 1270-1360℃ for 4-8 hours, and the specific sintering conditions are as follows: sintering at 1350℃ for 6 hours.

[0021] In this invention, the relative permittivity ε of the ceramic material (millimeter-wave dielectric ceramic) forming the ceramic superatoms is... r The value can be 45-100, the Qf value is 1500-5000GHz, and the temperature coefficient of the resonant frequency τ f It is -3 to 3 ppm / ℃.

[0022] Then, the sintered ceramic sample (millimeter-wave dielectric ceramic) is subjected to high-precision wire cutting to obtain the required high-temperature resistant and high-absorption ceramic superatoms.

[0023] The precision of the high-precision wire cutting is ±5μm.

[0024] In this invention, the ultraatomic dimensions of the high-temperature resistant and high-absorption ceramic are all in the range of 0.7-1.25 mm in length, width, and height.

[0025] According to one embodiment of the present invention, the superatomic size may be 0.85mm × 0.8mm × 0.78mm.

[0026] The high-temperature resistant, high-absorption ceramic superatomic structure ceramic-based metamaterial absorber provided by this invention is comparable to pure-phase Ba4Nd with the same ceramic superatomic size. 9.33 Ti 18 O 54 Table 1 shows the simulation comparison of the period and performance of the ceramic-based metamaterial absorber.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The ceramic superatomic structure provided by this invention is simple and compact, with high temperature stability and tolerance. It is compatible with metamaterial absorbers of different millimeter-wave frequencies and can meet the application needs of today's millimeter-wave technology for miniaturization, multiple scenarios, and especially extreme scenarios. Attached Figure Description

[0029] Figure 1 The millimeter-wave dielectric ceramic (Ba4Nd) obtained in the examples 9.33-x Sm x Ti 18-y Coy O 54-δ SEM images of (x = 4.5, y = 2.5, δ = 1.25). Detailed Implementation

[0030] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0032] Example 1: A high-temperature resistant, high-absorption ceramic superatom and its preparation method

[0033] In this embodiment, the millimeter-wave frequency band is determined by impedance matching based on S-parameters, using COMSOL multiphysics simulation software for parametric scanning (setting the dielectric constant ε). r The Qf value is 1000GHz-5000GHz, and the scan step size is 250GHz. The approximation relationship between the effective impedance of the S-parameters and the air impedance (approximately 1) is statistically analyzed (the closer to 1, the better). This allows for the design of the desired ceramic material properties (dielectric constant ε). r It is 70, and the Qf value is approximately 3000 GHz.

[0034] Furthermore, preferably, the desired millimeter-wave dielectric ceramic is prepared, characterized by its compositional formula being Ba4Nd. 9.33- x Sm x Ti 18-y Co y O 54-δ x is 4.5, y is 2.5, and δ is 1.25.

[0035] The preparation method of the millimeter-wave dielectric ceramic includes the following steps:

[0036] 1) Mix BaCO3, Sm2O3, Nd2O3, TiO2, and Co2O3 according to the chemical formula Ba4Nd 9.33-x Sm x Ti 18-y Co y O 54-δ Weigh the required raw materials, mix the weighed materials, ball mill, dry, pulverize, and sieve them, then pre-calcine to initially synthesize a single-phase tungsten bronze structure Ba4Nd.4.83 Sm 4.5 Ti 15.5 Co 2.5 O 54-δ Dielectric ceramic powder;

[0037] 2) The powder obtained in step 1) is added to polyvinyl butyral and then ball-milled, dried, pulverized and sieved, and then pressed into cylindrical ceramic green bodies using an automatic tablet press.

[0038] 3) The ceramic green body obtained in step 2) is sintered at 1350℃ for 6 hours to obtain the desired millimeter-wave dielectric ceramic sample. The SEM image of the ceramic obtained in this example with x = 4.5, y = 2.5, and δ = 1.25 is shown below. Figure 1 As shown. By Figure 1 It can be seen that the ceramic sample has a dense morphology and good sintering quality under these process parameters.

[0039] In step 1) above, the ball milling also includes adding zirconium oxide balls and anhydrous ethanol for ball milling; the ball milling speed is 400 rpm and the ball milling time is 6 h.

[0040] In step 1) above, the drying temperature is 80℃; the sieving process involves first passing the material through a 40-mesh sieve and then through an 80-mesh sieve.

[0041] In step 1) above, the pre-sintering temperature is 1180℃ and the pre-sintering time is 6h.

[0042] In step 2) above, the amount of polyvinyl butyral added is 1% of the powder mass.

[0043] In step 2) above, the ball milling time is 12 hours.

[0044] In step 2) above, the sieving is done through an 80-mesh sieve.

[0045] In step 2) above, the ceramic green body has a diameter of 10 mm and a thickness of 5 mm.

[0046] Then, the sintered ceramic sample was subjected to high-precision wire cutting (accuracy ±5μm) to obtain the required high-temperature resistant and high-absorption ceramic superatoms (size approximately 0.85mm×0.8mm×0.78mm).

[0047] The relative permittivity ε of the millimeter-wave dielectric ceramic sample obtained in this embodiment is... r The resonant frequency temperature coefficient is approximately 66.5, the Qf value is approximately 3000 GHz, and the temperature coefficient τ of the resonant frequency is... f It is approximately +1.55 ppm / ℃.

[0048] The sample (ceramic superatoms) obtained in this embodiment has a size of approximately 0.85 mm × 0.8 mm × 0.78 mm.

[0049] The absorption performance of the sample (ceramic superatoms) obtained in this embodiment in the waveguide environment is shown in Table 1.

[0050] The method for testing the absorption performance is as follows: using an opposing rectangular waveguide, the ceramic superatomic sample is placed on a wave-transparent refractory material (dielectric constant of about 2) in the center of the waveguide according to the simulation model, and the temperature is controlled by heating the outside of the waveguide using a heating device.

[0051] Table 1. Absorption performance of ceramic superatoms in Example 1

[0052]

[0053] This embodiment utilizes high-temperature resistant, high-absorption ceramic superatoms and pure-phase Ba4Nd with the same ceramic superatom size. 9.33 Ti 18 O 54 (dielectric constant ε) r Ceramic-based metamaterial absorbers were constructed with a Qf value of approximately 9500 GHz and a Qf value of 83.

[0054] The specific construction method is as follows: ceramic superatoms are periodically arranged (using periodic boundary conditions) to form an array. The 0.78mm edge is along the x-axis (electric field direction), the 0.8mm edge is along the y-axis (magnetic field direction), and the 0.85mm edge is along the z-axis (wave vector k direction), with a period of 3.5-6mm.

[0055] The periodicity and performance simulations of the two ceramic-based metamaterial absorbers constructed above were compared, and the results are shown in Table 2.

[0056] Table 2 Comparison of simulation results of metamaterial absorbers in Example 1

[0057]

[0058]

[0059] In Table 2, the BNSTC base represents "Ba4Nd". 9.33-x Sm x Ti 18-y Co y O 54-δ x is 4.5, y is 2.5, and δ is 1.25; BNT base represents "Ba4Nd 9.33 Ti 18 O 54 ".

[0060] As shown in Table 2, under the same geometric dimensions, the metamaterial absorber constructed from BNSTC-based metaatoms has a higher absorption rate at high frequencies; while the metamaterial absorber constructed from BNT-based metaatoms operates at a low frequency and has poor absorption performance. Furthermore, to increase its absorption rate, the period needs to be further extended, which is not conducive to the miniaturization of metamaterial devices.

[0061] The above embodiments are only used to illustrate the present invention. The ceramic materials and parameter settings can be varied. Any equivalent transformations and improvements made on the basis of the technical solution of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A millimeter wave dielectric ceramic having a composition expressed by the formula Ba4Nd 9.33-x Sm x Ti 18-y Co y O 54-δ wherein x is 3-6, y is 2-3, and δ is 1-1.

5.

2. The millimeter wave dielectric ceramic according to claim 1, characterized by: The x is 3-5.

3. The millimeter wave dielectric ceramic according to claim 1 or 2, characterized by: The x is 3, 3.5, 4, 4.5 or 5, the y is 2.3, 2.5, 2.7 or 2.9, and the delta is 1.15, 1.25, 1.35 or 1.

45.

4. A method for preparing the millimeter wave dielectric ceramic according to any one of claims 1-3, comprising the following steps: 1) BaCO3, Sm2O3, Nd2O3, TiO2, Co2O3 are weighed according to the chemical formula Ba4Nd 9.33-x Sm x Ti 18-y Co y O 54-δ The required raw materials are weighed, the weighed materials are mixed, ball-milled, dried, crushed, sieved, then pre-sintered, and a single-phase tungsten bronze structure Ba4Nd 9.33-x Sm x Ti 18-y Co y O 54-δ dielectric ceramic powder; 2) adding the dielectric ceramic powder obtained in step 1) into polyvinyl butyral ester, and then performing ball milling, drying, crushing, sieving, and pressing into a cylindrical ceramic green body; 3) sintering the ceramic green body obtained in step 2) to obtain the millimeter wave dielectric ceramic.

5. The method of claim 4, wherein: In step 1), the ball milling further comprises adding zirconium oxide balls and anhydrous ethanol for ball milling; the rotation speed of the ball milling is 400 rpm, and the ball milling time is 4-10 h; Or, in step 1), the drying temperature is 80°C; the sieving is first passed through a 40-mesh sieve, and then passed through an 80-mesh sieve; Or, in step 1), the pre-sintering temperature is 1100-1190°C, and the pre-sintering time is 5-8 h.

6. The production method according to claim 4 or 5, characterized in that: In step 2), the adding amount of the polyvinyl butyral ester is 0.9%-1.2% of the mass of the powder; Or, in step 2), the ball milling time is 10-14 h; Or, in step 2), the sieving is passed through an 80-mesh sieve; Or, in step 2), the diameter of the ceramic green body is 10 mm, and the thickness is 5 mm; Or, in step 3), the sintering conditions are 1270-1360°C for 4-8 h.

7. A high-temperature-resistant high-absorption ceramic super atom, which is obtained by high-precision wire cutting of the millimeter wave dielectric ceramic according to any one of claims 1-3 or prepared by the method according to any one of claims 4-6.

8. The high-temperature-resistant high-absorption ceramic super atom according to claim 7, characterized in that: The relative dielectric constant ε of the millimeter wave dielectric ceramic r is 45-100, the Qf value is 1500-5000 GHz, and the resonance frequency temperature coefficient τ f is -3-3 ppm / °C; Or, the size of the super atom ranges from 0.7 mm to 1.25 mm in length, width and height.

9. Use of the high-temperature-resistant high-absorption ceramic super atom according to claim 7 or 8 in the preparation of a ceramic-based metamaterial absorber.

10. A ceramic-based metamaterial absorber comprising the high-temperature-resistant high-absorption ceramic super atom according to claim 7 or 8.

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