Environment-friendly scheelite high-entropy microwave dielectric ceramic material and preparation method thereof

Abstract

The application relates to an environment-friendly scheelite high-entropy microwave dielectric ceramic material and a preparation method thereof. 0.5 (LaPrNdX) 0.5 / N MoO4, wherein X is at least two selected from Bi, Ce, Sm, Eu and Y, N is the sum of the element types of La, Pr, Nd and X. The ceramic material simultaneously has at least five elements of La, Pr, Nd and X in one element position, realizes high-entropy component design, can direct design of dielectric properties of the material through component selection, effectively reduces the sintering temperature of the material under the condition that no sintering aid is added, has reasonable dielectric constant, high quality factor and near-zero resonance frequency temperature coefficient, and exhibits excellent microwave dielectric properties.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic ceramics, and in particular relates to an environmentally friendly scheelite high-entropy microwave dielectric ceramic material and a preparation method thereof. Background Art

[0002] The rapid development of high-frequency communication technology has driven the urgent demand for 5G / 6G communication equipment with larger capacity and faster transmission speed, which in turn has put forward more stringent performance requirements for microwave dielectric ceramic materials. These ceramic materials have a suitable dielectric constant ( ), near-zero temperature coefficient of resonant frequency (TCF) and high quality factor ( Qf ) is characterized by its high dielectric constant and plays a vital role in modern communication systems. It is widely used in fields such as filters, dielectric antennas, substrates and resonators. It is particularly noteworthy that the lower sintering temperature (less than 900°C) can meet the application requirements of low-temperature co-fired ceramics (LTCC) technology; the low dielectric constant can effectively reduce the delay of signal propagation, the high quality factor ensures excellent frequency selectivity and energy efficiency, and the near-zero TCF value ensures the thermal stability of communication equipment under different temperature environments. In addition, the ceramic material formula should be conducive to the process flow and easy to industrialize. Most traditional electronic ceramics cannot meet the material requirements of LTCC technology because the sintering temperature of the ceramics is too high. Therefore, the development of advanced microwave dielectric ceramic materials is crucial to meet the growing demand for communications.

[0003] Existing microwave dielectric ceramic materials typically require the addition of a suitable amount of sintering aid to achieve low-temperature sintering. However, the cooling effect of such additives on the material system is very limited, and additives often deteriorate the performance of the ceramic, requiring repeated trade-offs in parameter selection during development. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, the present invention provides an environmentally friendly scheelite high-entropy microwave dielectric ceramic material and a method for preparing the same. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0005] The embodiment of the present invention provides an environmentally friendly scheelite high entropy microwave dielectric ceramic material, the structural expression of the ceramic material is Na 0.5 (LaPrNdX) 0.5 / N MoO4, wherein X is selected from at least two of Bi, Ce, Sm, Eu, and Y, and N is the sum of the number of element types of La, Pr, Nd, and X.

[0006] In one embodiment of the present invention, the sintering temperature of the ceramic material is 600-740°C.

[0007] In one embodiment of the present application, the ceramic material has a relative dielectric constant of 10-16, a quality factor of 20000-50000 GHz, and a resonance frequency temperature coefficient of -30 to -60 ppm / °C.

[0008] Another embodiment of the present application provides a preparation method of an environment-friendly scheelite high-entropy microwave dielectric ceramic material, comprising the steps of:

[0009] S1, according to the structure expression of the ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4, Na2CO3, La2O3, Pr2O3, Nd2O3, MoO3 and the oxide of element X are weighed as raw materials, wherein X is selected from at least two of Bi, Ce, Sm, Eu and Y, N is the sum of the element types of La, Pr, Nd and X, and the oxide of element X is selected from at least two of Bi2O3, CeO2, Sm2O3, Eu2O3 and Y2O3;

[0010] S2, the raw materials are uniformly mixed by a first ball milling process to obtain a first ball milled powder;

[0011] S3, the first ball milled powder is pre-sintered to obtain a pre-sintered ceramic powder;

[0012] S4, the ceramic powder is secondarily ball milled to obtain a second ball milled powder;

[0013] S5, the second ball milled powder is tabletted and sintered to obtain the ceramic material.

[0014] In one embodiment of the present application, after step S1, the following steps are included:

[0015] La2O3, Pr2O3, Nd2O3 and the oxide of element X are placed in a muffle furnace for pretreatment, and the pretreatment condition is 700-850°C for 3-6h.

[0016] In one embodiment of the present application, step S2 includes:

[0017] The raw materials, zirconium balls and anhydrous ethanol are placed in a ball mill tank for first ball milling at a mass ratio of 1:2:1, and the first ball milling parameters are as follows: speed 200-300r / min, time 3-6h, to obtain the first ball milled powder.

[0018] In one embodiment of the present application, step S3 includes:

[0019] The first ball milled powder is dried, and the dried powder is pre-sintered at 550-650°C for 4-8h to obtain the pre-sintered ceramic powder.

[0020] In one embodiment of the present application, step S4 comprises:

[0021] The ceramic powder is first ground and then put into a ball mill tank for secondary ball milling, and the secondary ball milling parameters include a rotation speed of 200-300 r / min and a time of 3-6 h to obtain the secondary ball milled powder.

[0022] In one embodiment of the present application, step S5 comprises:

[0023] The secondary ball milled powder is dried, and anhydrous ethanol is added to the dried powder for wetting; the wetted powder is first pressed into a ceramic block, and then the ceramic block is tightly pressed; then the anhydrous ethanol is removed, and sintering is performed to obtain the ceramic material.

[0024] In one embodiment of the present application, the weight percentage of the anhydrous ethanol added to the dried powder is 5-8%;

[0025] The pressure for pressing the ceramic block is 100-200 MPa, and the pressure for tightly pressing the ceramic block is 200-300 MPa.

[0026] The temperature for removing the anhydrous ethanol is 90-150°C, and the time is 1-2 h.

[0027] The sintering temperature is 600-740°C, and the time is 6-8 h.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] 1. The high-entropy microwave dielectric ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4 has at least five elements of La, Pr, Nd and X at one element position, realizes high-entropy component design, can be used to directionally design the dielectric properties of the material through component selection, effectively reduces the sintering temperature of the material without adding sintering aids, and the ceramic material has reasonable dielectric constant, high quality factor and near-zero resonance frequency temperature coefficient at a low sintering temperature, exhibits excellent microwave dielectric properties; at the same time, the ceramic material has good stability when placed in air, has the characteristics of simple chemical composition, environmental protection, non-toxicity and no pollution; in addition, the ceramic material is also chemically compatible with the commonly used low-temperature co-fired ceramic metal electrodes Ag or Al, proving the feasibility of improving the microwave dielectric properties of the material through high-entropy component design;

[0030] 2、The preparation method of the present application adopts an improved solid phase reaction method, and anhydrous ethanol is used to replace polyvinyl alcohol in the traditional solid phase reaction method, and the anhydrous ethanol is added to the dried powder and then pressed into a ceramic block, the anhydrous ethanol is easier to remove from the pressed ceramic, not only reduces the influence of the binder polyvinyl alcohol on the ceramic density and loss, improves the performance of the material, but also simplifies the preparation process. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A flowchart of a preparation method of an environment-friendly scheelite high-entropy microwave dielectric ceramic material is provided for the embodiments of the present application.

[0032] Figures 2a-2d The influence of sintering temperature on the density and microwave dielectric properties of Na 0.5 (BiLaPrNdSm) 0.1 MoO4 high-entropy ceramic is shown in the schematic diagram.

[0033] Figure 3 Na 0.5 (BiLaPrNdSm) 0.1 XRD pattern of Na

[0034] Figure 4 XRD patterns of high-entropy ceramics at the best sintering temperature in example 1, example 2 and example 3 are provided for the embodiments of the present application. DETAILED DESCRIPTION

[0035] The present application will be further described in detail below in combination with specific embodiments, but the embodiments of the present application are not limited thereto.

[0036] The present embodiment provides an environment-friendly scheelite high-entropy microwave dielectric ceramic material, and the material has a structural expression of Na 0.5 (LaPrNdX) 0.5 / N MoO4, wherein X is selected from at least two of Bi, Ce, Sm, Eu and Y, and N is the sum of the element types of La, Pr, Nd and X.

[0037] Specifically, the ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4, wherein X is selected from at least two of Bi, Ce, Sm, Eu and Y, i.e. X can be two, three, four or five of Bi, Ce, Sm, Eu and Y, and N can be 5, 6, 7 or 8, so that the ceramic material simultaneously has 5 elements or 6 elements or 7 elements or 8 elements at one element position.

[0038] It can be understood that when X is selected from two of Bi, Ce, Sm, Eu, and Y, the sum N of the number of element types of La, Pr, Nd, and X is 5, for example, Na 0.5 (BiLaPrNdSm) 0.1 MoO4; when X is selected from three of Bi, Ce, Sm, Eu, and Y, the sum N of the number of element types of La, Pr, Nd, and X is 6, for example, Na 0.5 (BiLaPrNdSmEu) 0.5 / 6 MoO4; when X is selected from four of Bi, Ce, Sm, Eu, and Y, the sum N of the number of element types of La, Pr, Nd, and X is 7, for example, Na 0.5 (BiLaPrNdSmEuY) 0.5 / 7 MoO4; when X is selected from five of Bi, Ce, Sm, Eu, and Y, the sum N of the number of element types of La, Pr, Nd, and X is 8, for example, Na 0.5 (BiCeLaPrNdSmEuY) 0.5 / 8 MoO4.

[0039] The ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4, the same element position simultaneously has at least 5 elements of La, Pr, Nd, and X, has high disorder degree, and forms a high-entropy configuration.

[0040] It should be noted that the ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4is not limited to the above examples, and the materials satisfying the above principles all belong to the scope of the ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4.

[0041] Specifically, the ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4has a sintering temperature of 600-740°C and can be sintered at a relatively low sintering range. It should be noted that 600-740°C is the sintering temperature range of the ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4ceramic system to achieve a better performance sintering temperature.

[0042] Specifically, the ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4has a relative dielectric constant of 10-16, a quality factor Qf of 20000-50000 GHz, and a resonance frequency temperature coefficient TCF of -30 to -60 ppm / °C.

[0043] Specifically, the ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4 is environmentally friendly and non-toxic and can be co-fired with Ag electrodes or Al electrodes.

[0044] For example, the environmentally friendly scheelite high entropy microwave dielectric ceramic material is a high entropy ceramic Na 0.5 (BiLaPrNdSm) 0.1 MoO4, this ceramic material is the first successfully prepared high entropy ultra-low temperature co-fired ceramic (ULTCC) microwave dielectric ceramic material, which can be sintered densely at an ultra-low sintering temperature of 600°C and maintain a very high density within 640~880°C, with a density greater than 97%; and Na 0.5 (BiLaPrNdSm) 0.1 MoO4 ceramic material also has excellent microwave dielectric properties: dielectric constant =15.7, quality factor Qf =33000GHz(@8.5GHz), resonant frequency temperature coefficient TCF=-37.8ppm / °C; In addition, Na 0.5 (BiLaPrNdSm) 0.1 MoO4 ceramic materials are also chemically compatible with the metal electrodes Ag or Al used in low-temperature co-fired ceramics (LTCC).

[0045] The high entropy microwave dielectric ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4 has at least five elements, La, Pr, Nd, and X, simultaneously in one element position, realizing high-entropy composition design. The dielectric properties of the material can be directionally designed through composition selection, and the sintering temperature of the material can be effectively reduced without adding sintering aids. The sintering temperature is 600~740°C, which can be lower than 700°C. Moreover, the ceramic material has a reasonable dielectric constant, a high quality factor, and a near-zero resonant frequency temperature coefficient at low sintering temperatures, exhibiting excellent microwave dielectric properties. At the same time, the ceramic material has good stability when placed in the air, and has the characteristics of simple chemical composition, environmental protection, non-toxicity, and pollution-free. In addition, the ceramic material is also chemically compatible with the metal electrodes Ag or Al of commonly used low-temperature co-fired ceramics, proving the feasibility of improving the microwave dielectric properties of the material through high-entropy composition design, thereby meeting the technical requirements of LTCC substrate materials.

[0046] This embodiment also provides a method for preparing a molybdenum-based microwave dielectric ceramic material, which is used to prepare the molybdenum-based microwave dielectric ceramic material described in the above embodiment.

[0047] See Figure 1 , Figure 1A flowchart of a preparation method of an environment-friendly scheelite high-entropy microwave dielectric ceramic material is provided for an embodiment of the present application. The preparation method comprises the following steps:

[0048] S1, according to the structural expression of the ceramic material, Na 0.5 (LaPrNdX) 0.5 / N MoO4, Na2CO3, La2O3, Pr2O3, Nd2O3, MoO3 and the oxide of element X are weighed as raw materials, wherein X is selected from at least two of Bi, Ce, Sm, Eu and Y, N is the sum of the element types of La, Pr, Nd and X, and the oxide of element X is selected from at least two of Bi2O3, CeO2, Sm2O3, Eu2O3 and Y2O3.

[0049] Specifically, the oxide of element X is the oxide of X element Bi, Ce, Sm, Eu and Y, i.e. Bi2O3, CeO2, Sm2O3, Eu2O3 and Y2O3. The molar ratio of X element Bi, Ce, Sm, Eu and Y is 1:1:1:1:1, and the molar ratio of the oxide of element X Bi2O3, CeO2, Sm2O3, Eu2O3 and Y2O3 is 1:2:1:1:1. For example, if X selects Ce and Sm, the oxide of element X is CeO2 and Sm2O3, and the molar ratio of CeO2 and Sm2O3 is 2:1; if X selects Bi, Eu and Sm, the oxide of element X is Bi2O3, Eu2O3 and Sm2O3, and the molar ratio of Bi2O3, Eu2O3 and Sm2O3 is 1:1:1.

[0050] Specifically, Na2CO3, La2O3, Pr2O3, Nd2O3, Bi2O3, CeO2, Sm2O3, Eu2O3, Y2O3 and MoO3 all have analytical purity. For example, the purity of Na2CO3 is 99%, the purity of MoO3 is 99.95%, the purity of La2O3, Pr2O3, Nd2O3, Sm2O3 and Eu2O3 is 99.5%, the purity of Y2O3 is 99%, and the purity of Bi2O3 is 99.9%, and the purity of CeO2 is 99%.

[0051] Further, before use, the oxides La2O3, Pr2O3, Nd2O3, Bi2O3, CeO2, Sm2O3, Eu2O3 and Y2O3 are put into a muffle furnace for pretreatment, and the pretreatment condition is 700-850°C for 3-6h. For example, the oxides are put into a muffle furnace for 4h at 780°C.

[0052] S2, the raw materials are uniformly mixed by a primary ball milling process to obtain a primary ball milled powder.

[0053] Specifically, the raw material, zirconium ball and anhydrous ethanol (ball milling medium) are added into the ball milling tank in a mass ratio of 1:2:1, and after being sealed, they are placed on a planetary ball mill for primary ball milling to mix uniformly. The primary ball milling parameters include a rotation speed of 200-300 r / min and a time of 3-6 h, to obtain the primary ball-milled powder.

[0054] S3, pre-sintering the primary ball-milled powder to obtain a pre-sintered ceramic powder.

[0055] Specifically, the primary ball-milled powder is first dried. For example, the primary ball-milled powder is placed in a general oven and dried at 100°C for 24 h. Then, the dried powder is pre-sintered at 550-650°C for 4-8 h to form the material phase, to obtain the pre-sintered ceramic powder.

[0056] S4, secondary ball milling of the ceramic powder to obtain a secondary ball-milled powder.

[0057] Specifically, the ceramic powder can be first ground finely by a manual grinding method, and then placed in a ball milling tank for secondary ball milling to further refine the particle size of the powder. The secondary ball milling parameters include a rotation speed of 200-300 r / min and a time of 3-6 h, to obtain the secondary ball-milled powder.

[0058] S5, tabletting and sintering of the secondary ball-milled powder to obtain the ceramic material.

[0059] Specifically, the secondary ball-milled powder is dried, and anhydrous ethanol is added to the dried powder for wetting. After wetting, the ceramic bulk is first pressed, and then the ceramic bulk is tightly pressed. Then, the anhydrous ethanol is removed, and sintering is performed to obtain the ceramic material.

[0060] In an alternative embodiment, the secondary ball-milled powder is dried at 100°C for 24 h. Anhydrous ethanol is added to the dried powder in a weight percentage of 5-8% for wetting. After wetting, the ceramic bulk is first pressed by a manual press at a pressure of 100-200 MPa, and then tightly pressed in an isostatic press at a pressure of 200-300 MPa for 3 min. Then, the anhydrous ethanol is removed by heating at 90-150°C for 1-2 h, and finally sintering is performed at 600-740°C for 6-8 h, to obtain an environmentally friendly low-temperature sintering molybdenum-based high-entropy microwave dielectric ceramic material.

[0061] For example, the shape of the ceramic bulk is a cylinder with a diameter of 10 mm and a height of 5 mm.

[0062] Currently, most microwave dielectric ceramic materials are prepared using the traditional solid-phase reaction method, which uses polyvinyl alcohol (PVA) as a binder and then removes it by keeping it at 550°C for 4 hours. However, as the ceramic sintering temperature continues to decrease (<550°C), the PVA introduced during the granulation process cannot be completely eliminated. The residual PVA reduces the density of the ceramic and increases the loss of the ceramic. The preparation method of this embodiment adopts an improved solid-phase reaction method, replacing the polyvinyl alcohol in the traditional solid-phase reaction method with anhydrous ethanol. Anhydrous ethanol is added to the dried powder and then pressed into a ceramic block. Anhydrous ethanol is easily removed from the pressed ceramic. This not only reduces the effect of the binder polyvinyl alcohol on the density and loss of the ceramic, improving the performance of the material, but also simplifies the preparation process and makes the preparation process simple.

[0063] This embodiment further illustrates the molybdenum-based microwave dielectric ceramic material and its preparation method through the following examples.

[0064] Example 1

[0065] The raw materials of analytical purity Na2CO3, Pr2O3, CeO2, Y2O3, La2O3, Nd2O3 and MoO3 were prepared in a molar ratio of 5:1:2:1:1:1:20, and the weighed Pr2O3, CeO2, Y2O3, La2O3 and Nd2O3 were placed in a muffle furnace and kept warm at 780°C for 4 hours. The prepared raw materials, zirconium balls and anhydrous ethanol were then ball milled once in a mass ratio of 1:2:1 to fully mix them. The ball milling speed was 200-300r / min for 4 hours to obtain a primary ball milled powder. The primary ball milled powder was placed in a conventional oven and dried at 100°C for 24 hours. The dried powder was then placed in a crucible and heated at 550 o C for 4 hours to obtain the pre-fired ceramic powder. After the pre-fired ceramic is manually ground, it is put into the ball mill again for secondary ball milling. The secondary ball milling speed is 200~300r / min and the time is 4h to obtain the secondary ball milling powder. The secondary ball milling powder is dried at 100°C for 24h, and then 5% by weight of anhydrous ethanol is added to the dried powder to moisten it. After moistening, it is first pressed into a cylindrical ceramic block with a diameter of 10mm and a height of 5mm under a pressure of 100MPa using a manual press, and then pressed tightly at a pressure of 200MPa in an isostatic press. The tightly pressed ceramic is first pressed at 120 o C for 1 hour to remove the anhydrous ethanol, and then sintered in air at 600-680°C at 600°C, 620°C, 640°C, 660°C, and 680°C for 6 hours to obtain the environmentally friendly low-temperature sintered high-entropy microwave dielectric ceramic material Na 0.5 (PrCeYLaNd) 0.1 MoO4.

[0066] Further, using network analyzer (4990A Agilent) and oven (DELTA 9023, Delta Design), the closed cavity resonance method TE 01δ Mode test Na 0.5 (PrCeYLaNd) 0.1 The microwave dielectric properties of MoO4 ceramic samples, wherein the formula for calculating the resonant frequency temperature coefficient TCF is as follows:

[0067]

[0068] In the formula, is the resonant frequency of the sample at 25°C, unit: GHz, is the resonant frequency of the sample at 85°C, unit: GHz.

[0069] After testing, Na 0.5 (PrCeYLaNd) 0.1 MoO4 ceramic sintered in 660 o C air, the microwave dielectric properties are optimal, the dielectric constant under microwave is ε r is 12.3 (@ 9.9 GHz), the quality factor Q is 1850, Qf is 21000 GHz, the resonant frequency temperature coefficient TCF under microwave is -44 ppm / o C (25~85 o C).

[0070] Example 2

[0071] The analytical purity raw materials Na2CO3, Bi2O3, Pr2O3, La2O3, Nd2O3, Sm2O3 and MoO3 are prepared in a molar ratio of 5:1:1:1:1:1:20, and the weighed Bi2O3, Pr2O3, La2O3, Nd2O3, Sm2O3 are placed in a muffle furnace and kept at 780°C for 4h. Then the prepared raw materials, zirconium balls and anhydrous ethanol are ball milled at a mass ratio of 1:2:1 to fully mix, the ball milling speed is 200-300r / min, and the time is 4h, to obtain the first ball milling powder. The first ball milling powder is placed in a general oven and dried at 100°C for 24h, then the dried powder is placed in a crucible and sintered at 650 oC for 4 hours to obtain the pre-fired ceramic powder. After the pre-fired ceramic is manually ground, it is put into the ball mill again for secondary ball milling. The secondary ball milling speed is 200~300r / min and the time is 4h to obtain the secondary ball milling powder. The secondary ball milling powder is dried at 100°C for 24h, and then 5% by weight of anhydrous ethanol is added to the dried powder to moisten it. After moistening, it is first pressed into a cylindrical ceramic block with a diameter of 10mm and a height of 5mm under a pressure of 100MPa using a manual press, and then pressed tightly at a pressure of 300MPa in an isostatic press. The tightly pressed ceramic is first pressed at 120 o C for 2h to remove the anhydrous ethanol, then select 560~1000℃ o C. 600 o C. 640 o C. 680 o C. 720 o C. 800 o C. 880 o C. 1000 o C at these temperature points are kept in air for 6 hours for sintering, and the environmentally friendly low-temperature sintered high-entropy microwave dielectric ceramic material Na 0.5 (BiLaPrNdSm) 0.1 MoO4.

[0072] Furthermore, the Na 0.5 (BiLaPrNdSm) 0.1 Density, relative density and dielectric properties of MoO4 ceramics. A network analyzer (4990A Agilent) and a temperature chamber (DELTA 9023, Delta Design) were used to analyze the MoO4 ceramics using the closed cavity resonance method (TE). 01δ Mode Test Na 0.5 (BiLaPrNdSm) 0.1 Microwave dielectric properties of MoO4 ceramic samples.

[0073] See Figures 2a-2d , Figures 2a-2d The sintering temperature provided by the embodiment of the present invention has an effect on Na 0.5 (BiLaPrNdSm) 0.1 Schematic diagram of the influence of density and microwave dielectric properties of MoO4 high entropy ceramics, Figure 2a Represents density and relative density maps, Figure 2b Represents the dielectric constant Atlas, Figure 2c Indicates quality factor Qf Atlas, Figure 2d Represents the resonant frequency temperature coefficient TCF spectrum. Figures 2a-2dIt can be seen that the relative density, dielectric constant and Qf values all increase first and then decrease with the increase of sintering temperature, while the TCF value fluctuates less than 5 ppm / ℃ in the whole sintering temperature range of 560℃ to 1000℃. Na 0.5 (BiLaPrNdSm) 0.1 MoO4ceramics are sintered densely at an ultra-low sintering temperature of 600℃ and maintain a very high density in the sintering temperature range of 640~880℃, with a density greater than 97%. Among them, when sintered at 640 o C, Na 0.5 (BiLaPrNdSm) 0.1 MoO4ceramics have the best microwave dielectric properties: a dielectric constant of 16 (@ 8.5 GHz), a quality factor Q of 3900, Qf of 33000 GHz, and a resonance frequency temperature coefficient TCF of -38 pm / o C (25~85 o C).

[0074] Further, Na o (BiLaPrNdSm) 0.5 MoO4sintered densely at 640 0.1 C is co-sintered with metal powder for 30 min, and the XRD after co-sintering is tested. See Figure 3 , Figure 3 Na 0.5 (BiLaPrNdSm) 0.1 MoO4ceramics and commonly used metal electrode materials are co-sintered at 640℃ for 30 min, and the XRD pattern is obtained. From Figure 3 it can be seen that in the XRD pattern of the sample co-sintered with 20% silver powder and aluminum powder by weight, only the diffraction peaks of Na 0.5 (BiLaPrNdSm) 0.1 MoO4and metal are detected, which means that the ceramic does not chemically react with Ag or Al at the sintering temperature.

[0075] Example 3

[0076] The raw materials of analytical purity Na2CO3, Bi2O3, Pr2O3, La2O3, Nd2O3, CeO2 and MoO3 were prepared in a molar ratio of 5:1:1:1:1:2:20, and the weighed Bi2O3, Pr2O3, La2O3, Nd2O3 and CeO2 were placed in a muffle furnace and kept warm at 780°C for 4 hours. The prepared raw materials, zirconium balls and anhydrous ethanol were then ball milled once in a mass ratio of 1:2:1 to fully mix them. The ball milling speed was 200-300r / min for 4 hours to obtain a primary ball milled powder. The primary ball milled powder was placed in a conventional oven and dried at 100°C for 24 hours. The dried powder was then placed in a crucible and heated at 650 o C for 4 hours to obtain the pre-fired ceramic powder. After the pre-fired ceramic is manually ground, it is put into the ball mill again for secondary ball milling. The secondary ball milling speed is 200~300r / min and the time is 4h to obtain the secondary ball milling powder. The secondary ball milling powder is dried at 100°C for 24h, and then 5% by weight of anhydrous ethanol is added to the dried powder to moisten it. After moistening, it is first pressed into a cylindrical ceramic block with a diameter of 10mm and a height of 5mm under a pressure of 100MPa using a manual press, and then pressed tightly at a pressure of 200MPa in an isostatic press. The tightly pressed ceramic is first pressed at 120 o C for 2 hours to remove the anhydrous ethanol, and then sinter at 640-740℃, 640℃, 660℃, 680℃, 700℃, 720℃, and 740℃ for 6 hours to obtain the environmentally friendly low-temperature sintered high-entropy microwave dielectric ceramic material Na 0.5 (BiLaPrNdCe) 0.1 MoO4.

[0077] Furthermore, a network analyzer (4990A Agilent) and a temperature chamber (DELTA 9023, Delta Design) were used to analyze the TE 01δ Mode Test Na 0.5 (BiLaPrNdCe) 0.1 Microwave dielectric properties of MoO4 ceramic samples.

[0078] After testing, Na 0.5 (BiLaPrNdCe) 0.1 MoO4 ceramics at 720 o C is sintered densely in air, and the microwave dielectric properties reach the best, and the dielectric constant under microwave is ε r 15 (@8.8GHz), quality factor Q is 2500, Qf The resonant frequency temperature coefficient TCF under microwave is -32ppm / o C(25~85 o C)。

[0079] See Figure 4 , Figure 4 XRD patterns of high-entropy ceramics at the optimum sintering temperature in Example 1, Example 2 and Example 3 provided by the embodiments of the present application. Figure 4 It can be known that Na 0.5 (PrCeYLaNd) 0.1 MoO4, Na 0.5 (BiLaPrNdSm) 0.1 MoO4 and Na 0.5 (BiLaPrNdCe) 0.1 MoO4 three kinds of crystals are ABO4 scheelite group tetragonal structure, the space group belongs to I41 / a (No. 88), Na + and the statistical average of trivalent cations, random distribution in ABO4 structure A site.

[0080] The Na 0.5 (LaPrNdX) 0.5 / N MoO4 high-entropy ceramic system is the first successfully prepared high-entropy ULTCC microwave dielectric ceramic material, which can realize low sintering temperature and excellent microwave dielectric properties without adding sintering aids, can be chemically compatible with commonly used LTCC metal electrodes Ag or Al, and can improve the microwave dielectric properties of the material through high-entropy component design.

[0081] The above is a further detailed description of the present application in combination with specific preferred embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be regarded as falling within the protection scope of the present application.

Claims

1. An environmentally friendly scheelite high-entropy microwave dielectric ceramic material, characterized in that, The structural expression of the ceramic material is Na 0.5 (LaPrNdX) 0.5 / N MoO4, wherein X is selected from at least two of Bi, Ce, Sm, Eu, Y, N is the sum of the element types of La, Pr, Nd, and X. 2.The environment-friendly scheelite high-entropy microwave dielectric ceramic material according to claim 1, characterized in that, The sintering temperature of the ceramic material is 600-740 DEG C. 3.The environment-friendly scheelite high-entropy microwave dielectric ceramic material of claim 1, characterized in that, The relative dielectric constant of the ceramic material is 10-16, the quality factor is 20000-50000 GHz, and the resonance frequency temperature coefficient is -30--60ppm / DEG C.

4. A method for preparing an environmentally friendly scheelite high-entropy microwave dielectric ceramic material, characterized in that, The method comprises the steps of: S1, according to the structural expression of ceramic material Na 0.5 (LaPrNdX) 0.5 / N MoO4weighing Na2CO3, La2O3, Pr2O3, Nd2O3, MoO3 and the oxide of element X as raw materials, wherein X is selected from at least two of Bi, Ce, Sm, Eu, Y, N is the sum of the element types of La, Pr, Nd, X, and the oxide of element X is selected from at least two of Bi2O3, CeO2, Sm2O3, Eu2O3, Y2O3; S2, uniformly mixing the raw materials by a first ball milling process to obtain a first ball milled powder; S3, pre-sintering the first ball milled powder to obtain a pre-sintered ceramic powder; S4, second ball milling the ceramic powder to obtain a second ball milled powder; S5, tabletting and sintering the second ball milled powder to obtain the ceramic material.

5. The preparation method of the environment-friendly scheelite high-entropy microwave dielectric ceramic material according to claim 4, characterized in that, After step S1, the method comprises: The oxides of La2O3, Pr2O3, Nd2O3 and element X are placed in a muffle furnace for pretreatment, and the pretreatment conditions are 700-850 DEG C for 3-6h.

6. The preparation method of the environment-friendly scheelite high-entropy microwave dielectric ceramic material according to claim 4, characterized in that, Step S2 comprises: The raw materials, zirconium balls and anhydrous ethanol are placed in a ball mill tank for first ball milling at a mass ratio of 1:2:1, and the first ball milling parameters are as follows: speed 200-300r / min, time 3-6h, to obtain the first ball milled powder.

7. The preparation method of the environment-friendly scheelite high-entropy microwave dielectric ceramic material according to claim 4, characterized in that, Step S3 comprises: The first ball milled powder is dried, and the dried powder is pre-sintered at 550-650 DEG C for 4-8h to obtain the pre-sintered ceramic powder.

8. The method for preparing the environmentally friendly scheelite high entropy microwave dielectric ceramic material according to claim 4, characterized in that: Step S4 comprises: The ceramic powder is first ground and then placed in a ball mill tank for second ball milling, and the second ball milling parameters include: speed 200-300r / min, time 3-6h, to obtain the second ball milled powder.

9. The preparation method of the environment-friendly scheelite high-entropy microwave dielectric ceramic material according to claim 4, characterized in that, Step S5 comprises: The second ball milled powder is dried, and anhydrous ethanol is added to the dried powder for wetting; the wetted powder is first pressed into a ceramic block, and then the ceramic block is tightly pressed; then the anhydrous ethanol is removed, and sintering is performed to obtain the ceramic material.

10. The method of claim 9, wherein the method comprises the steps of: preparing a slurry of a white tungsten ore, a high-entropy microwave dielectric ceramic material, and a binder; and sintering the slurry. The weight percentage of anhydrous ethanol added to the dried powder is 5-8%; The pressure for pressing the ceramic block is 100-200MPa; the pressure for tightly pressing the ceramic block is 200-300MPa; The temperature for removing the anhydrous ethanol is 90-150 DEG C, and the time is 1-2h; The sintering temperature is 600-740 DEG C, and the time is 6-8h.

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