La, Mg and Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material and preparation method thereof

Abstract

The invention discloses a La, Mg and Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material and a preparation method thereof, CaSmAlO4 and SrSmAlO4 materials with a negative resonant frequency temperature coefficient (tau f) are compounded with a SrLa (Mg0. 5Ti0. 5) O4 material with a positive tau f, so that the tau f value of the microwave dielectric ceramic material is close to zero; meanwhile, La, Mg and Ti ions in the SrLa (Mg0. 5Ti0. 5) O4 system can be used for co-doping A and B sites of (CaSr) SmAlO4 ceramic to realize regulation and control of material defects and optimization of dielectric loss, so that a novel high-Q-value microwave dielectric ceramic material which has a near-zero temperature coefficient of resonance frequency and ultralow loss is provided. The raw materials are low in cost, easy to obtain, non-toxic and environmentally friendly, the process is simple and easy to operate, influence factors are easy to control, and the method is suitable for large-scale industrial production and beneficial to popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave dielectric ceramic materials, and in particular to a high-Q value doped (CaSr) SmAlO4 microwave dielectric ceramic material and a preparation method thereof. Background Art

[0002] Microwave dielectric ceramics refer to ceramics used as dielectric materials in microwave frequency band (300MHz ~ 3000GHz) circuits and perform one or more functions. They can be made into components such as dielectric resonators, capacitors, filters, dielectric antennas, waveguide transmission lines, dielectric substrates, etc., and are widely used in modern communications, military radar and other fields. With the rapid development of high-frequency communication technology, especially 5G communication technology, the loss of high-frequency signals in the transmission path and the thermal effect of devices have higher requirements for microwave dielectric ceramic materials. There is an urgent need to develop a material with both a suitable dielectric constant (ε r =18~22)、High Q×f(>60000GHz)、With near-zero resonant frequency temperature coefficient (|τ f |<5ppm / ℃) high-performance microwave dielectric material system.

[0003] There are many microwave dielectric ceramic systems with dielectric constants in the existing technology, but they all have shortcomings. For example, Ba(Mg 1 / 3 Ta 2 / 3 )O3 system and (Zr, Sn)TiO4 system microwave dielectric ceramics have high raw material prices, which limits their scope of use; BaTi4O9 and Ba2Ti9O 20 The microwave dielectric ceramics of the system have a high thermal expansion coefficient and low bending strength, and there is a greater risk of cracking when subjected to thermal shock and external force impact.

[0004] CaSmAlO4 and SrSmAlO4, with tetragonal K2NiF4 layered perovskite structures, are an important branch of microwave dielectric ceramics that have emerged in recent years. CaSmAlO4 and SrSmAlO4 system microwave dielectric ceramics have high quality factors, with Q×f usually greater than 60,000 GHz; their composite solid solution 0.7CaSmAlO4-0.3SrSmAlO4 system has a Q×f as high as 130,000 GHz, but its resonant frequency temperature coefficient τ f Negative (generally τ f <-10ppm / ℃), which restricts its application in the field of 5G communication technology. Therefore, how to obtain a near-zero resonant frequency temperature coefficient (|τ f |<5ppm / ℃) (CaSr)SmAlO4 microwave dielectric ceramic materials have become an important research topic in the field of high Q value microwave dielectric ceramic materials. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a La, Mg, Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material by f ) is a negative value of CaSmAlO4, SrSmAlO4 materials, and τ f SrLa(Mg 0.5 Ti 0.5 )O4 materials are compounded to realize the τ f The value is close to zero; at the same time, SrLa(Mg 0.5 Ti 0.5 The La, Mg, and Ti ions in the (CaSr)SmAlO4 system can co-dope the A and B sites of the (CaSr)SmAlO4 ceramic, controlling material defects and optimizing dielectric loss. This provides a novel microwave dielectric ceramic material with a near-zero resonant frequency temperature coefficient, ultra-low loss, and high-Q value. Another object of the present invention is to provide a method for preparing the aforementioned La, Mg, and Ti co-doped (CaSr)SmAlO4 microwave dielectric ceramic material and the resulting product.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The present invention provides a La, Mg, Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material, which is CaSmAlO4, SrSmAlO4, SrLa (Mg 0.5 Ti 0.5 )O4 composite solid solution, its general chemical formula is xCaSmAlO4+ySrSmAlO4+zSrLa(Mg 0.5 Ti 0.5 )O4, where 0.40≤x≤0.60, 0.15≤y≤0.30, 0.20≤z≤0.40, and x+y+z=1.

[0008] In the above solution, the relative dielectric constant ε of the microwave dielectric ceramic material of the present invention is r The quality factor is 19.0~21.5, the quality factor Q×f≥85000GHz, the resonant frequency temperature coefficient is -5~5ppm / ℃, and the bending strength is ≥308MPa.

[0009] Another object of the present invention is achieved through the following technical solutions:

[0010] The preparation method of the La, Mg, and Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material provided by the present invention comprises the following steps:

[0011] (1) Preparation of pre-synthetic precursor powder

[0012] CaCO3, Sm2O3, Al2O3, SrCO3, La2O3, MgCO3, and TiO2 are used as raw materials and the ingredients are prepared according to the stoichiometric amount in the chemical formula. Then, anhydrous ethanol is used as a ball milling medium for a single ball milling process. The ball milled slurry is dried, sieved, and press-formed to obtain a material, which is heated to 1250-1300°C at a rate of 5°C / min and calcined for 150-180 minutes. After cooling in the furnace, the material is ground and sieved to obtain a pre-synthetic precursor powder.

[0013] (2) Preparation of microwave dielectric ceramics

[0014] (2-1) subjecting the pre-synthesized precursor powder to a secondary ball milling treatment, drying, grinding, and sieving the ball milled slurry, and granulating and aging the resulting material to obtain a treated material;

[0015] (2-2) After the treated material is pressed into shape, it is subjected to cold isostatic pressing, and then subjected to binder removal heat treatment to obtain a pre-sintered part;

[0016] (2-3) The pre-sintered part is placed in a high-temperature furnace and heated to 1400-1500°C at a rate of 5°C / min for calcination, with a holding time of 150-180 minutes. The part is cooled in the furnace to obtain a La, Mg, and Ti co-doped (CaSr)SmAlO4 microwave dielectric ceramic material.

[0017] Furthermore, the pressure of the compression molding in step (1) of the preparation method of the present invention is 4 to 6 MPa.

[0018] Furthermore, in the step (2-1) of the preparation method of the present invention, granulation is carried out using an anhydrous ethanol solution of polyvinyl butyral or polyvinyl alcohol with a concentration of 4 to 5 wt% as a binder, and the amount of the binder is 3 to 5 wt% of the material; the pressure of the pressing molding in the step (2-2) is 6 to 8 MPa; the pressure of the cold isostatic pressing is 200 to 300 MPa, and the holding time is ≥90 s; the debinding heat treatment is heating to 630 to 650° C. at a rate of 1° C. / min and keeping warm for 120 to 150 min.

[0019] The product is made using the above-mentioned preparation method of La, Mg, Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material.

[0020] The present invention has the following beneficial effects:

[0021] (1) The present invention adopts the resonant frequency temperature coefficient (τ f ) is negative for the two systems CaSmAlO4 and SrSmAlO4, and τf For positive values ​​of the system SrLa(Mg 0.5 Ti 0.5 )O4 for compounding and regulating the material's τ f value, so that τ f The value is close to zero. At the same time, using SrLa(Mg 0.5 Ti 0.5 The La, Mg, and Ti ions in the )O4 system can co-dope the A and B positions of (CaSr)SmAlO4 ceramics to control the defects of the material, optimize the dielectric loss, and ultimately obtain a co-doped, composite solid solution microwave dielectric ceramic material with excellent performance.

[0022] (2) The microwave dielectric ceramic material of the present invention is a microwave dielectric ceramic material with high Q value and high temperature stability, having a layered perovskite structure and excellent performance. Its relative dielectric constant ε r Adjustable (19.0~21.5), low loss (quality factor Q×f=85000~95000GHz), resonant frequency temperature coefficient τ f Near-zero temperature can be adjusted (-5 to +5ppm / °C) and has high strength (flexural strength ≥ 308MPa).

[0023] (3) The raw materials of the present invention are cheap and easily available, non-toxic and environmentally friendly, the process is simple and easy to operate, and the influencing factors are easy to control. It is suitable for large-scale industrial production and is conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be described in further detail below with reference to the embodiments and accompanying drawings:

[0025] Figure 1 1 is the XRD diagram of the microwave dielectric ceramic materials prepared in the examples and comparative examples of the present invention. DETAILED DESCRIPTION

[0026] Example 1:

[0027] 1. This embodiment is a La, Mg, Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material, which is CaSmAlO4, SrSmAlO4, SrLa (Mg 0.5 Ti 0.5 )O4 composite solid solution, its chemical formula is 0.5CaSmAlO4+0.2SrSmAlO4+0.3SrLa(Mg 0.5 Ti 0.5 )O4.

[0028] 2. The preparation method of the above-mentioned La, Mg, Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material comprises the following steps:

[0029] (1) Preparation of pre-synthetic precursor powder

[0030] CaCO3, Sm2O3, Al2O3, SrCO3, La2O3, MgCO3, and TiO2 with a purity of 99.9% are used as raw materials and the ingredients are prepared according to the stoichiometric ratio in the above chemical formula. Then, anhydrous ethanol is used as the ball milling medium and a ball: material: anhydrous ethanol = 4:1:3 is used. The ball milling treatment is carried out on a planetary ball mill at a speed of 400 r / min for 20 hours. The ball milled slurry is dried, passed through an 80-mesh sieve, and pressed under 4 MPa to obtain a material, which is placed in a sealed crucible and calcined at 5°C / min to 1250°C in an oxidizing atmosphere for 150 minutes. After cooling with the furnace, it is ground and passed through an 80-mesh sieve to obtain a pre-synthetic precursor powder.

[0031] (2) Preparation of microwave dielectric ceramics

[0032] (2-1) The pre-synthesized precursor powder was subjected to a secondary ball milling treatment (same as the primary ball milling treatment). The ball milled slurry was dried, ground, and passed through an 80-mesh sieve. The resulting material was granulated (using a 4 wt % solution of polyvinyl butyral in anhydrous ethanol as a binder, the binder being 4 wt % of the material) and aged for 24 h to obtain a treated material.

[0033] (2-2) The treated material was placed in a mold and pressed at a pressure of 6 MPa to obtain a cylindrical body with a thickness of 6 mm and a diameter of 13 mm; the cylindrical body was placed in a rubber glove, evacuated, and placed in a cold isostatic press for cold isostatic pressing at 200 MPa for 90 seconds; the temperature was then increased to 650°C at a rate of 1°C / min for debinding, the temperature was maintained for 150 minutes, and the body was cooled in the furnace to obtain a pre-sintered part;

[0034] (2-3) The pre-sintered part is placed in a high-temperature furnace and heated to 1450°C at a rate of 5°C / min for calcination. The temperature is kept at this temperature for 180 min and the furnace is cooled to obtain a La, Mg, and Ti co-doped (CaSr)SmAlO4 microwave dielectric ceramic material.

[0035] Example 2:

[0036] The present embodiment provides a method for preparing a La, Mg, and Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material, which differs from the first embodiment in that:

[0037] 1. The general chemical formula of this embodiment is 0.4CaSmAlO4+0.25SrSmAlO4+0.35SrLa(Mg 0.5 Ti 0.5 )O4.

[0038] 2. The calcination temperature in step (1) is 1300°C; the calcination temperature in step (2-3) is 1420°C.

[0039] Example 3:

[0040] The present embodiment provides a method for preparing a La, Mg, and Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material, which differs from the first embodiment in that:

[0041] 1. The general chemical formula of this embodiment is 0.6CaSmAlO4+0.2SrSmAlO4+0.2SrLa(Mg 0.5 Ti 0.5 )O4.

[0042] 2. The calcination temperature in step (1) is 1300°C and the holding time is 180 min; the calcination temperature in step (2-3) is 1480°C and the holding time is 160 min.

[0043] Example 4:

[0044] The present embodiment provides a method for preparing a La, Mg, and Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material, which differs from the first embodiment in that:

[0045] The chemical formula of this embodiment is 0.5CaSmAlO4+0.3SrSmAlO4+0.2SrLa(Mg 0.5 Ti 0.5 )O4.

[0046] Embodiment 5:

[0047] The present embodiment provides a method for preparing a La, Mg, and Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material, which differs from the first embodiment in that:

[0048] The general chemical formula of this embodiment is 0.55CaSmAlO4+0.2SrSmAlO4+0.25SrLa(Mg 0.5 Ti 0.5 )O4.

[0049] Comparative Example 1:

[0050] According to the chemical formula xCaSmAlO4+ySrSmAlO4+zSrLa(Mg 0.5 Ti 0.5 )O4, x=1, y=0, z=0, that is, a microwave dielectric ceramic material with the chemical formula CaSmAlO4 is used as comparative example 1. Its preparation method uses CaCO3, Sm2O3, and Al2O3 with a purity of 99.9% as raw materials, and the remaining steps are the same as those in Example 1.

[0051] Comparative Example 2:

[0052] According to the chemical formula xCaSmAlO4+ySrSmAlO4+zSrLa(Mg 0.5 Ti 0.5 )O4, x = 0.65, y = 0.35, z = 0, that is, the chemical formula is Ca 0.65 Sr 0.35 The microwave dielectric ceramic material of SmAlO4 is used as comparative example 2. Its preparation method uses CaCO3, Sm2O3, Al2O3, and SrCO3 with a purity of 99.9% as raw materials, and the remaining steps are the same as those in embodiment 1.

[0053] The XRD crystal phase patterns of the microwave dielectric ceramic materials of the embodiments of the present invention and the comparative examples are as follows: Figure 1 As shown, the diffraction peaks of the microwave dielectric ceramic materials prepared in various embodiments of the present invention are completely consistent with those of the comparative example, indicating that the materials obtained in the embodiments of the present invention are single crystal phase tetragonal K2NiF4 layered perovskite CaSmAlO4 structural materials.

[0054] The dielectric cavity method is used to test the dielectric constant, dielectric loss and resonant frequency of microwave dielectric ceramic materials. The frequency temperature coefficient is tested in the temperature range of 25 to 85 ° C, and according to the formula τ f =(f 85 -f 25 ) / (f 25 ×60) for calculation, where f 85 and f 25 are the center frequencies of the samples at 85° C. and 25° C., respectively. Table 1 shows the performance test results of the microwave dielectric ceramic materials prepared in the examples of the present invention and the comparative examples.

[0055] Table 1 Properties of microwave dielectric ceramic materials prepared in the embodiments of the present invention and comparative examples

[0056]

Claims

1. A La, Mg, Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material, characterized by: The microwave dielectric ceramic material is CaSmAlO4, SrSmAlO4, SrLa(Mg 0.5 Ti 0.5 )O4 composite solid solution, its general chemical formula is xCaSmAlO4+ySrSmAlO4+zSrLa(Mg 0.5 Ti 0.5 )O4, where 0.40≤x≤0.60, 0.15≤y≤0.30, 0.20≤z≤0.40, and x+y+z=1.

2. The La, Mg, Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material according to claim 1, characterized in that: The relative dielectric constant ε of the microwave dielectric ceramic material r The quality factor is 19.0~21.5, the quality factor Q×f≥85000GHz, the resonant frequency temperature coefficient is -5~5ppm / ℃, and the bending strength is ≥308MPa.

3. The method for preparing the La, Mg, Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material according to claim 1 or 2, characterized in that The following steps are involved: (1) Preparation of pre-synthetic precursor powder CaCO3, Sm2O3, Al2O3, SrCO3, La2O3, MgCO3, and TiO2 are used as raw materials and the ingredients are prepared according to the stoichiometric amount in the chemical formula. Then, anhydrous ethanol is used as a ball milling medium for a single ball milling process. The ball milled slurry is dried, sieved, and press-formed to obtain a material, which is heated to 1250-1300°C at a rate of 5°C / min and calcined for 150-180 minutes. After cooling in the furnace, the material is ground and sieved to obtain a pre-synthetic precursor powder. (2) Preparation of microwave dielectric ceramics (2-1) subjecting the pre-synthesized precursor powder to a secondary ball milling treatment, drying, grinding, and sieving the ball milled slurry, and granulating and aging the resulting material to obtain a treated material; (2-2) After the treated material is pressed into shape, it is subjected to cold isostatic pressing, and then subjected to binder removal heat treatment to obtain a pre-sintered part; (2-3) The pre-sintered part is placed in a high-temperature furnace and heated to 1400-1500°C at a rate of 5°C / min for calcination, with a holding time of 150-180 minutes. The part is cooled in the furnace to obtain a La, Mg, and Ti co-doped (CaSr)SmAlO4 microwave dielectric ceramic material.

4. The method for preparing the La, Mg, Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material according to claim 3, characterized in that: The pressure of the compression molding in the step (1) is 4 to 6 MPa.

5. The method for preparing the La, Mg, Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material according to claim 3, characterized in that: In the step (2-1), granulation is performed using an anhydrous ethanol solution of polyvinyl butyral or polyvinyl alcohol with a concentration of 4-5 wt% as a binder, and the amount of the binder is 3-5 wt% of the material.

6. The method for preparing the La, Mg, Ti co-doped (CaSr) SmAlO4 microwave dielectric ceramic material according to claim 3, characterized in that: The pressure of the pressing molding in the step (2-2) is 6-8 MPa; the pressure of the cold isostatic pressing is 200-300 MPa, and the holding time is ≥90s; the debinding heat treatment is to increase the temperature to 630-650°C at 1°C / min and keep the temperature for 120-150 minutes.

7. A product obtained by the method for preparing La, Mg, Ti co-doped (CaSr)SmAlO4 microwave dielectric ceramic material according to any one of claims 3 to 6.

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