Single-phase La-Bi-B-based microwave dielectric ceramic material and preparation method thereof

Abstract

The invention discloses a single-phase La-Bi-B-based microwave dielectric ceramic material and a preparation method thereof, and belongs to the technical field of functional ceramic materials, the molecular formula is La1-xBixBO3, and x is greater than or equal to 0 and less than or equal to 0.12; the preparation method comprises the following steps: taking La2O3, B2O3 and Bi2O3 as raw materials, carrying out ball milling in water, and drying to obtain raw material powder; heating the raw material powder to 930-960 DEG C for calcining, then ball-milling and uniformly mixing in water, and drying to obtain a pre-sintered material; mixing and granulating the pre-sintered material and an adhesive to obtain green body particles, and carrying out compression molding on the green body particles to obtain a green body; and calcining the green body under the condition of 1050-1100 DEG C, thereby obtaining the product. Pure phase replacement of La < 3 + > by Bi < 3 + > is realized in a LaBO3 ceramic system, excellent microwave dielectric properties are maintained at the sintering temperature lower than the melting point of a copper electrode, and the material can be used as a high-quality substrate material of a leakage mode dielectric resonant cavity antenna in a microwave frequency band.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional ceramic materials, and in particular relates to a single-phase La-Bi-B based microwave dielectric ceramic material and a preparation method thereof. Background Art

[0002] With the development of modern wireless communication technology, high-frequency and long-distance transmission have become urgent needs for the future. Achieving these goals has brought opportunities for the rapid development of antennas as transducer elements for wireless communications. Among the many frequency bands for antenna application, the Ku-band has a natural advantage, which coincides with the development trend of antennas. The Ku-band refers to the radio wave frequency band with a frequency of 12-18 GHz and can be used in fields such as satellite communications, broadcasting, and airport detection radar. Antennas in this frequency band present many problems and challenges, including difficult to control directionality, slow response speed, low efficiency, and poor signal transmission stability. Microwave dielectric ceramics, as antenna substrate materials, show great potential. Their excellent dielectric properties mean there is an opportunity to solve many of the problems exposed by Ku-band antennas.

[0003] Common ceramic systems include molybdates, borates, niobates and vanadates. Among them, LaBO3 ceramics have excellent microwave dielectric properties. Specifically, the microwave dielectric properties exhibited at a sintering temperature of 1200-1300℃ are ε r = 12.5, Q× f = 53000 GHz, τ f = -52 ppm / °C. However, such a high sintering temperature cannot match the metal with high electrical conductivity, and the dielectric resonant antenna used in the microwave band has higher requirements on the sintering temperature and dielectric properties of LaBO3 ceramic materials. Therefore, it is necessary to further pursue higher Q×f Values ​​close to zero τ f value. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a single-phase La-Bi-B based microwave dielectric ceramic material and a preparation method thereof, which realizes Bi 3+ To La 3+ It can be used as a pure phase replacement of copper and maintains excellent microwave dielectric properties at a sintering temperature lower than the melting point of copper electrode, and can be used as a high-quality substrate material for leakage mode dielectric resonant cavity antennas in the microwave frequency band.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention to solve the technical problem is: A single-phase La-Bi-B based microwave dielectric ceramic material, the molecular formula of which is La 1-x Bi x BO3, where 0≤x≤0.12.

[0006] The method for preparing the above-mentioned single-phase La-Bi-B based microwave dielectric ceramic material comprises the following steps: (1) La2O3, B2O3 and Bi2O3 were weighed as raw materials according to the stoichiometric ratio, the raw materials were ball-milled and mixed in deionized water, and dried to obtain raw material powder; (2) The raw material powder is heated to 930-960°C, calcined for 3-5 hours, cooled to room temperature, and then ball-milled in deionized water to mix, and dried to obtain a pre-calcined material; (3) mixing the pre-sintered material with the binder and granulating the mixture to obtain green pellets, and pressing the green pellets into a green body; (4) The green body is calcined at 1060-1090°C for 4-5 hours to obtain the product.

[0007] Furthermore, the drying temperature in step (1) and step (2) is 60-100°C.

[0008] Furthermore, in step (2), the heating rate is 1-3°C / min, and the cooling rate is 1-3°C / min.

[0009] Furthermore, in step (3), the mass ratio of the premix to the adhesive is 87-90:10-13.

[0010] Furthermore, the adhesive in step (3) is polyvinyl alcohol.

[0011] Furthermore, in step (3), the pressing pressure is 15-25 MPa, and the pressing time is 60-120 s.

[0012] Furthermore, in step (4), the heating rate is 1-3°C / min, and the cooling rate is also 1-3°C / min.

[0013] The beneficial effects produced by the present invention are: Based on the good dielectric properties of LaBO3 ceramics, the present invention uses a solid phase reaction method to achieve Bi 3+ To La 3+ The pure phase substitution of the ceramic reduces the sintering temperature and improves the microwave dielectric properties of the ceramic. f Value and better τ f The best microwave dielectric properties at a sintering temperature of 1075°C are as follows: εr = 11.9, Q× f = 39178 GHz, τ f =-34.7 ppm / °C. The prepared material can be used as a high-quality substrate material for leaky-mode dielectric resonant cavity antennas in the microwave band. The antenna exhibits polarization isolation and excellent radiation performance, including S11 = -56.6 dB, VSWR = 1.016, BW = 40 MHz, η = 93%, and G = 8.55 dB. This material effectively solves the problems of microwave dielectric ceramics in antenna applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The process reaction flow chart of the present invention is as follows; Figure 2 The XRD patterns of the ceramic materials in Examples 1-4 and Comparative Example 1 are shown; Figure 3 The SEM images of the ceramic materials in Examples 1-4 and Comparative Example 1 are shown; Figure 4 Graphs showing microwave dielectric properties of ceramic materials in Examples 1-4 and Comparative Example 1; Figure 5 This is a diagram demonstrating the function of the ceramic material in the leakage mode dielectric resonant cavity antenna in Example 3. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, rather than all embodiments.

[0016] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the invention as claimed, but is merely intended to represent selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0017] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0018] The features and performance of the present invention are further described in detail below with reference to the embodiments and drawings.

[0019] Example 1 A single-phase La-Bi-B based microwave dielectric ceramic material, the molecular formula of which is La 0.97 Bi 0.03 BO3, the preparation method thereof comprises the following steps: (1) Weigh 0.485 mol La2O3, 0.5 mol B2O3, and 0.015 mol Bi2O3 as raw materials, respectively, mix them by ball milling in deionized water, and then dry them at 100°C to obtain raw material powders; (2) The raw material powder was heated to 950°C at a rate of 2°C / min, calcined for 4 h, then cooled to room temperature at a rate of 2°C / min, then ball-milled in deionized water and dried at 100°C to obtain a pre-calcined material; (3) mixing the pre-sintered material and polyvinyl alcohol in a mass ratio of 88:12 and granulating the mixture to obtain green pellets, and pressing the green pellets under a pressure of 20 MPa for 120 seconds to obtain a green body; (4) The green body is calcined at 1075°C for 4 hours, and after the temperature drops to 500°C, it is naturally cooled to obtain the product.

[0020] Example 2 A single-phase La-Bi-B based microwave dielectric ceramic material, the molecular formula of which is La 0.94 Bi 0.06 BO3, the preparation method thereof comprises the following steps: (1) Weigh 0.47 mol La2O3, 0.5 mol B2O3, and 0.03 mol Bi2O3 as raw materials, respectively, mix them by ball milling in deionized water, and then dry them at 100°C to obtain raw material powders; (2) The raw material powder was heated to 950°C at a rate of 2°C / min, calcined for 4 h, then cooled to room temperature at a rate of 2°C / min, then ball-milled in deionized water and dried at 100°C to obtain a pre-calcined material; (3) mixing the pre-sintered material and polyvinyl alcohol in a mass ratio of 88:12 and granulating the mixture to obtain green pellets, and pressing the green pellets under a pressure of 20 MPa for 120 seconds to obtain a green body; (4) The green body is calcined at 1075°C for 4 hours, and after the temperature drops to 500°C, it is naturally cooled to obtain the product.

[0021] Example 3 A single-phase La-Bi-B based microwave dielectric ceramic material, the molecular formula of which is La 0.91 Bi 0.09 BO3, the preparation method thereof comprises the following steps: (1) Weigh 0.455 mol La2O3, 0.5 mol B2O3, and 0.045 mol Bi2O3 as raw materials, respectively, mix them by ball milling in deionized water, and then dry them at 100°C to obtain raw material powders; (2) The raw material powder was heated to 950°C at a rate of 2°C / min, calcined for 4 h, then cooled to room temperature at a rate of 2°C / min, then ball-milled in deionized water and dried at 100°C to obtain a pre-calcined material; (3) mixing the pre-sintered material and polyvinyl alcohol in a mass ratio of 88:12 and granulating the mixture to obtain green pellets, and pressing the green pellets under a pressure of 20 MPa for 120 seconds to obtain a green body; (4) The green body is calcined at 1075°C for 4 hours, and after the temperature drops to 500°C, it is naturally cooled to obtain the product.

[0022] Example 4 A single-phase La-Bi-B based microwave dielectric ceramic material, the molecular formula of which is La 0.88 Bi 0.12 BO3, the preparation method thereof comprises the following steps: (1) Weigh 0.44 mol La2O3, 0.5 mol B2O3, and 0.06 mol Bi2O3 as raw materials, mix them by ball milling in deionized water, and then dry them at 100°C to obtain raw material powders; (2) The raw material powder was heated to 950°C at a rate of 2°C / min, calcined for 4 h, then cooled to room temperature at a rate of 2°C / min, then ball-milled in deionized water and dried at 100°C to obtain a pre-calcined material; (3) mixing the pre-sintered material and polyvinyl alcohol in a mass ratio of 88:12 and granulating the mixture to obtain green pellets, and pressing the green pellets under a pressure of 20 MPa for 120 seconds to obtain a green body; (4) The green body is calcined at 1075°C for 4 hours, and after the temperature drops to 500°C, it is naturally cooled to obtain the product.

[0023] Example 5 A single-phase La-Bi-B based microwave dielectric ceramic material, the molecular formula of which is La 0.88 Bi 0.12 BO3, the preparation method thereof comprises the following steps: (1) Weigh 0.44 mol La2O3, 0.5 mol B2O3, and 0.06 mol Bi2O3 as raw materials, mix them by ball milling in deionized water, and then dry them at 60°C to obtain raw material powders; (2) The raw material powder was heated to 960°C at a rate of 3°C / min, calcined for 3 h, then cooled to room temperature at a rate of 3°C / min, then ball-milled in deionized water and mixed, and dried at 60°C to obtain a pre-calcined material; (3) mixing the pre-sintered material and polyvinyl alcohol in a mass ratio of 87:13 and granulating the mixture to obtain green pellets, which were then pressed under a pressure of 25 MPa for 60 seconds to obtain a green body; (4) The green body is calcined at 1060°C for 4 hours, and after the temperature drops to 500°C, it is naturally cooled to obtain the product.

[0024] Example 6 A single-phase La-Bi-B based microwave dielectric ceramic material, the molecular formula of which is La 0.88 Bi 0.12 BO3, the preparation method thereof comprises the following steps: (1) Weigh 0.44 mol La2O3, 0.5 mol B2O3, and 0.06 mol Bi2O3 as raw materials, mix them by ball milling in deionized water, and then dry them at 80°C to obtain raw material powders; (2) The raw material powder was heated to 930°C at a rate of 1°C / min, calcined for 5 h, then cooled to room temperature at a rate of 1°C / min, then ball-milled in deionized water and dried at 100°C to obtain a pre-calcined material; (3) mixing the pre-sintered material and polyvinyl alcohol in a mass ratio of 90:10 and granulating the mixture to obtain green pellets, and pressing the green pellets under a pressure of 15 MPa for 120 seconds to obtain a green body; (4) The green body is calcined at 1090°C for 4 hours, and after the temperature drops to 500°C, it is naturally cooled to obtain the product.

[0025] Comparative Example 1 A single-phase La-B-based microwave dielectric ceramic material, whose molecular formula is LaBO3, and a preparation method thereof comprises the following steps: (1) Weigh 0.5 mol La2O3 and 0.5 mol B2O3 as raw materials, mix them in deionized water by ball milling, and then dry them at 100°C to obtain raw material powders; (2) The raw material powder was heated to 950°C at a rate of 2°C / min, calcined for 4 h, then cooled to room temperature at a rate of 2°C / min, then ball-milled in deionized water and dried at 100°C to obtain a pre-calcined material; (3) mixing the pre-sintered material and polyvinyl alcohol in a mass ratio of 88:12 and granulating the mixture to obtain green pellets, and pressing the green pellets under a pressure of 20 MPa for 120 seconds to obtain a green body; (4) The green body is calcined at 1075°C for 4 hours, and after the temperature drops to 500°C, it is naturally cooled to obtain the product.

[0026] Test example Taking the ceramic materials prepared in Examples 1-4 and Comparative Example 1 as examples, each material was tested separately, and the results are shown in FIG. Figure 2-5 .

[0027] Figure 2 is the XRD pattern of the materials in Examples 1-4 and Comparative Example 1, wherein Figure 2 a is the overall picture, Figure 2 b is the enlarged view of the dotted box. Figure 3 The SEM images of the materials in Examples 1-4 and Comparative Example 1 show that Bi 3+ Replace La in LaBO3 3+ No second phase appears, and Bi 3+ Substitution is beneficial to grain growth.

[0028] Taking the material in Example 3 as an example, the microwave dielectric properties were measured at calcination temperatures of 1050°C and 1100°C. The specific results are shown in Figure 4 , Figure 4 The microwave dielectric properties test results of the materials at different calcination temperatures show that the optimal microwave dielectric properties are shown at a sintering temperature lower than the melting point of the copper electrode. ε r = 11.9, Q× f = 39178 GHz and τ f= -34.7 ppm / °C.

[0029] Using La of Example 3 0.91 Bi 0.09 A dielectric resonant antenna with leakage mode was designed at 12.05 GHz using BO3 ceramic material as the substrate. The structure and simulation results are shown in Figure 5 The antenna exhibits polarization isolation and good radiation performance, including S11 = -56.6 dB, VSWR = 1.016, BW = 40 MHz, η = 93%, and G = 8.55 dB. This demonstrates that the present invention effectively addresses the challenges of microwave dielectric ceramics in antenna applications.

Claims

1. A single-phase La-Bi-B based microwave dielectric ceramic material, characterized in that: Its molecular formula is La 1-x Bi x BO3, where 0≤x≤0.

12.

2. The method for preparing the single-phase La-Bi-B based microwave dielectric ceramic material according to claim 1, characterized in that: The following steps are involved: (1) La2O3, B2O3 and Bi2O3 were weighed as raw materials according to the stoichiometric ratio, the raw materials were ball-milled and mixed in deionized water, and dried to obtain raw material powder; (2) The raw material powder is heated to 930-960°C, calcined for 3-5 hours, cooled to room temperature, and then ball-milled in deionized water to mix, and dried to obtain a pre-calcined material; (3) mixing the pre-sintered material with the binder and granulating the mixture to obtain green pellets, and pressing the green pellets into a green body; (4) The green body is calcined at 1060-1090°C for 4-5 hours to obtain the product.

3. The method for preparing a single-phase La-Bi-B based microwave dielectric ceramic material according to claim 2, wherein: The drying temperature in step (1) and step (2) is 60-100°C.

4. The method for preparing a single-phase La-Bi-B based microwave dielectric ceramic material according to claim 2, wherein: In step (2), the heating rate is 1-3°C / min, and the cooling rate is 1-3°C / min.

5. The method for preparing a single-phase La-Bi-B based microwave dielectric ceramic material according to claim 2, wherein: The mass ratio of the premix to the adhesive in step (3) is 87-90:10-13.

6. The method for preparing a single-phase La-Bi-B based microwave dielectric ceramic material according to claim 2, wherein: The adhesive in step (3) is polyvinyl alcohol.

7. The method for preparing a single-phase La-Bi-B based microwave dielectric ceramic material according to claim 2, wherein: The pressing pressure in step (3) is 15-25 MPa, and the pressing time is 60-120 s.

8. The method for preparing a single-phase La-Bi-B based microwave dielectric ceramic material according to claim 2, wherein: In step (4), the heating rate is 1-3°C / min, and the cooling rate is also 1-3°C / min.

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