Ultralow-loss orthogonal strontium-based microwave dielectric ceramic and preparation method thereof

Abstract

The invention relates to the technical field of ceramic materials, in particular to ultralow-loss orthogonal strontium-based microwave dielectric ceramic and a preparation method thereof, the chemical formula of the ultralow-loss orthogonal strontium-based microwave dielectric ceramic is SrYb2O4, and preparation raw materials are SrCO3 and Yb2O3. The preparation method comprises the following steps: firstly, weighing SrCO3 powder and Yb2O3 powder according to a certain proportion, mixing, sequentially carrying out wet grinding treatment and drying treatment, pre-sintering for 4-8 hours in an air atmosphere at the temperature of 1100 DEG C to obtain pre-sintered powder, carrying out secondary ball milling and drying, adding a binder, granulating, carrying out compression molding, and finally sintering for 4-8 hours in an air atmosphere at the temperature of 1400-1500 DEG C to obtain the SrBO3-Yb2O3 composite material. The orthogonal strontium-based microwave dielectric ceramic can be obtained. The orthogonal strontium-based microwave dielectric ceramic has an ultrahigh quality factor, can improve the selectivity of the working frequency of a device, simplifies the heat dissipation design, and is widely used for manufacturing various dielectric antenna substrates, resonators, filters and other microwave devices.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to an ultra-low-loss orthogonal strontium-based microwave dielectric ceramic and a preparation method thereof. Background Art

[0002] Microwave dielectric ceramics (MWDC) refer to ceramics used as dielectric materials in microwave frequency band (300MHz-300 GHz) circuits and perform one or more functions such as microwave waveguide, shielding and resonance. They are key basic materials in modern communication technology fields such as microwave communications, high-speed and high-frequency circuit substrates, satellite positioning and navigation systems, radar detection, etc. They are widely used as components such as resonators, filters, dielectric substrates and dielectric waveguide circuits. The rapid development of modern mobile communications has driven the rapid development of various types of microwave mobile communication terminal equipment towards miniaturization, lightweight, multifunctionality and low cost. With the deepening application of 5G technology, microwave communication technology has extended to the millimeter wave band. Microwave dielectric ceramic filter materials in the extremely high frequency millimeter wave band need to: 1. Have a low dielectric constant (ε r ) to increase the transmission rate of electrical signals; 2. Low dielectric loss, i.e. high quality factor (Q×f, usually requiring Q×f ≥ 100000GHz) to improve the selectivity of the device's operating frequency and reduce the device's energy consumption. Therefore, low dielectric constant and high quality factor microwave dielectric ceramic materials (dielectric constant ε r <20) has been widely explored and studied by researchers at home and abroad in recent years.

[0003] Recently, a series of binary rare earth (RE) oxide microwave ceramic systems have been reported, among which SrY2O4:ε r =14.78, Q×f=84090GHz, τ f =-14.98ppm / ℃, and then the Sr 1+x Y2O 4+x (x=0-0.04) series ceramics have good microwave dielectric properties: ε r =15.41, Q×f=112375GHz, τ f =-17.44ppm / ℃(x=0.2), but non-stoichiometric ratios are usually accompanied by defects that cause lattice distortion and reduce the thermal stability of ceramics. In recent years, ion substitution has become one of the means to optimize material composition and structure and control microwave dielectric properties. For example, Zhou Huanfu et al. used Sm with a large ionic radius on the basis of SrY2O4 ceramics to 3+ and Ho 3+ Replace Y 3+ ions, SrSm2O4 and SrHo2O4 ceramics were obtained at 1400℃ and 1475℃, respectively, and the best microwave dielectric properties were: εr =18.16, Q×f=40646GHz, τ f =-17.6ppm / ℃(SrSm2O4);ε r =14.87, Q×f=24021GHz, τ f =-17.03ppm / ℃(SrHo2O4). Sm with large ion radius 3+ and Ho 3+ The addition of Er caused the Q×f performance of the ceramic to deteriorate. Subsequently, they used the solid phase reaction method to 3+ and Tm 3+ Incorporation of substitution Y 3+ ions to adjust the microwave dielectric properties of the ceramic sample, and the best microwave dielectric properties of the ceramic obtained at 1575 and 1525 ℃ are: ε r =14.44, Q×f=23271GHz, τ f =-21.5ppm / ℃(SrSmEr2O4);ε r =14.49, Q×f=41138GHz, τ f =-36.69ppm / ℃(SrTm2O4) performance, the result is: cations with smaller ionic radius cannot improve its Q×f value. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultra-low loss orthogonal strontium-based microwave dielectric ceramic and a preparation method thereof, aiming to develop a single-phase microwave dielectric ceramic with low loss and ultra-high quality factor.

[0005] To achieve the above objectives, in a first aspect, the present invention provides an ultra-low loss orthogonal strontium-based microwave dielectric ceramic, wherein the orthogonal strontium-based microwave dielectric ceramic has a chemical formula of SrYb2O4 and is prepared from raw materials of SrCO3 and Yb2O3.

[0006] In a second aspect, the present invention further provides a method for preparing an ultra-low loss orthogonal strontium-based microwave dielectric ceramic, characterized in that the preparation method comprises the following steps:

[0007] (1) Weighing SrCO3 and Yb2O3 powders in proportion to obtain raw powders;

[0008] (2) stirring and mixing the raw powder, and sequentially performing wet grinding and drying to obtain dried powder, and pre-calcining the dried powder at 1100° C. in an air atmosphere for 4-8 hours to obtain a pre-sintered powder;

[0009] (3) The pre-sintered powder is subjected to secondary ball milling and drying, and then a binder is added to granulate the powder, and the powder is pressed into a shape. Finally, the powder is sintered at 1400-1500° C. in an air atmosphere for 4-8 hours to obtain an orthorhombic strontium-based microwave dielectric ceramic.

[0010] Preferably, in step (1), the molar ratio of SrCO3 to Yb2O3 is 1:1.

[0011] Preferably, in step (2), the wet milling treatment time is 6 to 12 hours, and the milling medium is anhydrous ethanol.

[0012] Preferably, in step (3), the binder is a polyvinyl alcohol solution with a mass concentration of 5%, and the added mass of the binder accounts for 3% of the total mass of the original powder.

[0013] Preferably, in step (3), the sintering temperature is 1450°C.

[0014] In a third aspect, the present invention also provides an application of an ultra-low loss orthogonal strontium-based microwave dielectric ceramic, wherein the orthogonal strontium-based microwave dielectric ceramic structure is SrYb2O4, which is used to prepare microwave dielectric antenna substrates or resonators or microwave components of filters.

[0015] The beneficial effects are as follows:

[0016] (1) The present invention prepares a SrYb2O4 microwave dielectric ceramic material by wet-grinding the raw powders of SrCO3 and Yb2O3 according to a ratio, drying and pre-sintering to obtain a pre-sintered powder, adding a binder and granulating, pressing and sintering the pre-sintered powder, and preparing the SrYb2O4 microwave dielectric ceramic material. The material has an ultra-high quality factor (Q×f) value (103802~118777GHz) and low dielectric loss; its dielectric constant (ε r ) reaches 15.4~16.1, and the resonant frequency temperature coefficient (τ f ) value is between (-36.1~-31.1ppm / ℃), with good temperature stability, and can be widely used in the manufacture of various microwave devices such as dielectric antenna substrates, resonators and filters.

[0017] (2) The SrYb2O4 microwave dielectric ceramic material prepared by this method has a stable crystal structure and is a single pure phase of SrYb2O4, providing an option for the precise design of controllable microwave dielectric ceramic materials.

[0018] (3) The present invention can produce SrYb2O4 microwave dielectric ceramic material with ultra-high quality factor and low dielectric loss without adding any modifying materials. At the same time, the microwave dielectric ceramic is not easy to deliquesce and is suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 It is a schematic flow chart of the steps of a method for preparing an ultra-low-loss orthogonal strontium-based microwave dielectric ceramic material prepared in Examples 1-5 of the present invention.

[0021] Figure 2 This is the X-ray diffraction (XRD) spectrum of the ultra-low loss orthorhombic strontium-based microwave dielectric ceramic SrYb2O4 prepared in Example 3 of the present invention.

[0022] Figure 3 This is a scanning electron microscope (SEM) surface morphology image of the ultra-low loss orthorhombic strontium-based microwave dielectric ceramic SrYb2O4 prepared in Example 3 of the present invention.

[0023] Figure 4 Graph showing the simulated antenna gain and efficiency of the ultra-low-loss orthogonal strontium-based microwave dielectric ceramic SrYb2O4 prepared in Example 3 of the present invention.

[0024] Figure 5 Graph showing the variation trend of Q×f and total lattice energy of the SrYb2O4 ceramics prepared in Examples 1-5 with temperature. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] See Figure 1 The present invention provides an ultra-low loss orthogonal strontium-based microwave dielectric ceramic, wherein the chemical composition of the orthogonal strontium-based microwave dielectric ceramic is SrYb2O4, and the preparation method thereof comprises the following steps:

[0027] (1) weighing SrCO3 and Yb2O3 powders to obtain raw powders, wherein the molar ratio of SrCO3 to Yb2O3 is 1:1;

[0028] (2) stirring and mixing the raw powder, and sequentially performing wet grinding and drying to obtain dried powder, and pre-calcining the dried powder at 1100° C. in an air atmosphere for 4-8 hours to obtain a pre-sintered powder;

[0029] (3) The pre-sintered powder is subjected to secondary ball milling and drying, and then a binder is added to granulate the powder. The binder is a polyvinyl alcohol solution with a mass concentration of 5%, and the added mass of the binder accounts for 3% of the total mass of the original powder. The powder is then pressed into shape and finally sintered at 1400-1500°C in an air atmosphere for 4-8 hours to obtain an orthorhombic strontium-based microwave dielectric ceramic.

[0030] In order to better understand the present technical solution, the following examples are provided for further explanation:

[0031] Example 1

[0032] A method for preparing an ultra-low-loss orthogonal strontium-based microwave dielectric ceramic material comprises the following steps:

[0033] (1) The original powders of SrCO3 and Yb2O3 with a purity greater than 99.9% were weighed and prepared according to the composition of SrYb2O4, wherein the molar ratio of SrCO3 to Yb2O3 was 1:1;

[0034] (2) wet-milling the raw materials from step (1) for 6 hours using anhydrous ethanol as the milling medium, drying the raw materials, and pre-calcining them in an atmosphere at 1100° C. for 4 hours to obtain a pre-sintered powder;

[0035] (3) The pre-sintered powder is subjected to secondary ball milling and drying, and then a binder is added and granulated, followed by pressing and molding, and finally sintering at 1400°C in an air atmosphere for 4 hours; the binder is a polyvinyl alcohol solution with a mass concentration of 5%, and the amount of polyvinyl alcohol added accounts for 3% of the total mass of the powder.

[0036] Example 2

[0037] A method for preparing an ultra-low-loss orthogonal strontium-based microwave dielectric ceramic material comprises the following steps:

[0038] (1) The original powders of SrCO3 and Yb2O3 with a purity greater than 99.9% were weighed and prepared according to the composition of SrYb2O4, wherein the molar ratio of SrCO3 to Yb2O3 was 1:1;

[0039] (2) wet-milling the raw materials from step (1) for 6 hours using anhydrous ethanol as the milling medium, drying the raw materials, and pre-calcining them in an atmosphere at 1100° C. for 4 hours to obtain a pre-sintered powder;

[0040] (3) The pre-sintered powder is subjected to secondary ball milling and drying, and then a binder is added and granulated, followed by pressing and molding, and finally sintering at 1425°C in an air atmosphere for 4 hours; the binder is a polyvinyl alcohol solution with a mass concentration of 5%, and the amount of polyvinyl alcohol added accounts for 3% of the total mass of the powder.

[0041] Example 3

[0042] A method for preparing an ultra-low-loss orthogonal strontium-based microwave dielectric ceramic material comprises the following steps:

[0043] (1) The original powders of SrCO3 and Yb2O3 with a purity greater than 99.9% were weighed and prepared according to the composition of SrYb2O4, wherein the molar ratio of SrCO3 to Yb2O3 was 1:1;

[0044] (2) wet-milling the raw materials from step (1) for 6 hours using anhydrous ethanol as the milling medium, drying the raw materials, and pre-calcining them in an atmosphere at 1100° C. for 4 hours to obtain a pre-sintered powder;

[0045] (3) The pre-sintered powder is subjected to secondary ball milling and drying, and then a binder is added and granulated, followed by pressing and molding, and finally sintering at 1450°C in an air atmosphere for 4 hours; the binder is a polyvinyl alcohol solution with a mass concentration of 5%, and the amount of polyvinyl alcohol added accounts for 3% of the total mass of the powder.

[0046] Figure 2 This is the X-ray diffraction (XRD) spectrum of the ultra-low-loss orthorhombic strontium-based microwave dielectric ceramic SrYb2O4 prepared in Example 3. As can be seen from the figure, the SrYb2O4 microwave dielectric ceramic has a pure orthorhombic structure, consistent with the SrYb2O4 PDF card PDF#96-200-2245. No impurities are found, indicating that a single-phase material can be obtained. This demonstrates that the method for preparing the ultra-low-loss orthorhombic strontium-based microwave dielectric ceramic is feasible and effective, with simple preparation and low production cost.

[0047] Figure 3 This is a scanning electron micrograph of the ultra-low-loss orthorhombic strontium-based microwave dielectric ceramic (SrYb2O4) prepared in Example 3. The image shows uniform grain size, a dense structure, and the absence of significant pores and secondary phases. This demonstrates the feasibility and effectiveness of the method for preparing an ultra-low-loss orthorhombic strontium-based microwave dielectric ceramic material, demonstrating that this method can produce a relatively dense SrYb2O4 microwave dielectric ceramic material.

[0048] Figure 4 The simulated antenna gain and efficiency diagram of the ultra-low loss orthogonal strontium-based microwave dielectric ceramic SrYb2O4 prepared in Example 3. It can be seen from the figure that the gain of the designed antenna at the center resonant frequency (5.505GHz) is 5.7dBi. 11 The radiation efficiency in the <-10dB region reached 90.69%, demonstrating that the method for preparing an ultra-low-loss orthogonal strontium-based microwave dielectric ceramic is feasible and effective, meeting the operational requirements of C-band 5G communication technology.

[0049] Example 4

[0050] A method for preparing an ultra-low-loss orthogonal strontium-based microwave dielectric ceramic material comprises the following steps:

[0051] (1) The original powders of SrCO3 and Yb2O3 with a purity greater than 99.9% were weighed and prepared according to the composition of SrYb2O4, wherein the molar ratio of SrCO3 to Yb2O3 was 1:1;

[0052] (2) wet-milling the raw materials from step (1) for 6 hours using anhydrous ethanol as the milling medium, drying the raw materials, and pre-calcining them in an atmosphere at 1100° C. for 4 hours to obtain a pre-sintered powder;

[0053] (3) The pre-sintered powder is subjected to secondary ball milling and drying, and then a binder is added and granulated, followed by pressing and molding, and finally sintering at 1475°C in an air atmosphere for 4 hours; the binder is a polyvinyl alcohol solution with a mass concentration of 5%, and the amount of polyvinyl alcohol added accounts for 3% of the total mass of the powder.

[0054] Example 5

[0055] A method for preparing an ultra-low-loss orthogonal strontium-based microwave dielectric ceramic material comprises the following steps:

[0056] (1) The original powders of SrCO3 and Yb2O3 with a purity greater than 99.9% were weighed and prepared according to the composition of SrYb2O4, wherein the molar ratio of SrCO3 to Yb2O3 was 1:1;

[0057] (2) wet-milling the raw materials from step (1) for 6 hours using anhydrous ethanol as the milling medium, drying the raw materials, and pre-calcining them in an atmosphere at 1100° C. for 4 hours to obtain a pre-sintered powder;

[0058] (3) The pre-sintered powder is subjected to secondary ball milling and drying, and then a binder is added and granulated, followed by pressing and molding, and finally sintering at 1500°C in an air atmosphere for 4 hours; the binder is a polyvinyl alcohol solution with a mass concentration of 5%, and the amount of polyvinyl alcohol added accounts for 3% of the total mass of the powder.

[0059] Furthermore, the present invention uses the cylindrical dielectric resonator method to evaluate the microwave dielectric properties. Specifically, the Hakki-Coleman method is used to measure the dielectric constant of solid materials, ε r It can only be measured at a resonant frequency corresponding to the TE011 mode. In order to avoid the problem of conduction and radiation losses, the Q value of microwave dielectric ceramic samples can be measured by the resonant cavity method, where the sample is placed in a low-loss spacer cavity. The resonant frequency temperature coefficient (τ f ) can be used to measure the stability of devices made of materials under different working environments. It represents the "drift" of the resonant frequency as the temperature changes. The relationship between resonant frequency and temperature is as follows:

[0060]

[0061] Where f0 is the initial resonant frequency, Δf is the change in resonant frequency, and ΔT is the temperature change. The properties of the prepared microwave dielectric ceramics are shown in Table 1:

[0062] Table 1 Microwave dielectric properties of ultra-low loss orthogonal strontium-based microwave dielectric ceramics prepared in Examples 1 to 5

[0063] Example composition Sintering temperature (℃) <![CDATA[ε r ]]> Q×f(GHz) <![CDATA[τ f (ppm / ℃)]]> 1 <![CDATA[SrYb2O4]]> 1400 15.4 103802 -35.0 2 <![CDATA[SrYb2O4]]> 1425 15.7 107459 -36.1 3 <![CDATA[SrYb2O4]]> 1450 16.1 118777 -31.3 4 <![CDATA[SrYb2O4]]> 1475 15.8 112973 -34.7 5 <![CDATA[SrYb2O4]]> 1500 15.9 105250 -31.1

[0064] As can be seen from Table 1, an ultra-low loss orthorhombic strontium-based microwave dielectric ceramic material prepared exhibits optimal performance at 1450°C. The sintering temperature changes the bond length of the crystal, thereby affecting the bond valence of each ion, the strength of the "rattling" effect, and the size of the lattice energy, thereby achieving the purpose of regulating microwave dielectric properties. In addition, by adjusting the difference in ionic radius between strontium (Sr) and lanthanide elements (Ln), the "rattling" effect of the cation is reduced, thereby reducing the microwave dielectric loss of SrB2O4 (B=RE,Y) ceramics. Yb with the smallest ionic radius is selected. 3+ ions, which can minimize the unit cell volume of SrB2O4 and lead to Sr 2+ The compressed effect is the strongest, which is expected to significantly reduce the intrinsic polarization and loss, thereby greatly improving the Q×f value and further reducing ε r It has an ultra-high quality factor (Q×f) value (103802~118777GHz) and low dielectric loss. Its dielectric constant reaches 15.4~16.1 and the resonant frequency temperature coefficient τ f The SrYb2O4 microwave dielectric ceramics are single-phase, easy to precisely control in structure, and not prone to deliquesce, making them suitable for mass production.

[0065] like Figure 5 As shown in the figure, the quality factor (Q×f) of the ceramic sample increases first and then decreases with increasing sintering temperature, reaching its maximum at 1450°C, consistent with the variation in total lattice energy. A higher lattice energy results in a more stable structure. Therefore, temperature control makes SrYb2O4 microwave dielectric ceramics prepared at 1450°C more suitable for practical applications.

[0066] The prepared SrYb2O4 microwave dielectric ceramic material has an ultra-high quality factor and low dielectric loss without the need to add modifying materials. It can improve the selectivity of the device's operating frequency and simplify the heat dissipation design. It can be widely used in the manufacture of various microwave devices such as dielectric antenna substrates, resonators and filters. The microwave components include but are not limited to microwave resonators, filters, oscillators or dielectric antennas.

[0067] For SrB2O4 type microwave dielectric ceramics, the present invention converts Yb 3+ ion( CN=6) introduces B position, Yb 3+ The ion radius of the ions is the smallest. The prepared SrYb2O4 microwave dielectric ceramics do not fail to improve their Q×f value as described in the background art, but significantly improve their Q×f value. The Q×f values ​​of the SrYb2O4 microwave dielectric ceramics described in Examples 1 to 5 are all above 100000 GHz. This is because the introduction of Yb 3+ ions can minimize the unit cell volume of SrB2O4 and lead to Sr 2+ The compressed effect is the strongest, which reduces the intrinsic polarization and loss, thereby significantly improving the Q×f value and further reducing ε r .

[0068] The above disclosure is merely a preferred embodiment of an ultra-low-loss orthogonal strontium-based microwave dielectric ceramic and its preparation method of the present invention. It is certainly not intended to limit the scope of the present invention. A person skilled in the art will understand that implementing all or part of the processes of the above embodiment and making equivalent changes in accordance with the claims of the present invention still fall within the scope of the invention.

Claims

1. An ultra-low loss orthogonal strontium-based microwave dielectric ceramic, characterized in that: The chemical formula of the orthorhombic strontium-based microwave dielectric ceramic is SrYb2O4, and the raw materials for preparation are SrCO3 and Yb2O3.

2. The ultra-low loss orthogonal strontium-based microwave dielectric ceramic according to claim 1, characterized in that: The preparation method of the microwave dielectric ceramic comprises the following steps: (1) Weighing SrCO3 and Yb2O3 powders in proportion to obtain raw powders; (2) stirring and mixing the raw powder, and sequentially performing wet grinding and drying to obtain dried powder, and pre-calcining the dried powder at 1100° C. in an air atmosphere for 4-8 hours to obtain a pre-sintered powder; (3) The pre-sintered powder is subjected to secondary ball milling and drying, and then a binder is added to granulate the powder, and the powder is pressed into a shape. Finally, the powder is sintered at 1400-1500° C. in an air atmosphere for 4-8 hours to obtain an orthorhombic strontium-based microwave dielectric ceramic.

3. The ultra-low loss orthogonal strontium-based microwave dielectric ceramic according to claim 2, characterized in that: In the step (1), the molar ratio of SrCO3 to Yb2O3 is 1:

1.

4. The ultra-low loss orthogonal strontium-based microwave dielectric ceramic according to claim 3, characterized in that: In the step (2), the wet grinding treatment time is 6-12 hours, and the ball milling medium is anhydrous ethanol.

5. The ultra-low loss orthogonal strontium-based microwave dielectric ceramic according to claim 4, characterized in that: In the step (3), the binder is a polyvinyl alcohol solution with a mass concentration of 5%, and the added mass of the binder accounts for 3% of the total mass of the original powder.

6. The ultra-low loss orthogonal strontium-based microwave dielectric ceramic according to claim 5, characterized in that: In the step (3), the sintering temperature is 1450°C.

7. Use of the microwave dielectric ceramic according to claim 6, characterized in that: The microwave dielectric ceramic is used for preparing microwave dielectric antenna substrates or microwave components of resonators or filters.

Images