Aluminate microwave dielectric ceramic material and preparation method thereof

Abstract

The invention discloses an aluminate microwave dielectric ceramic material and a preparation method thereof, the chemical composition of the aluminate microwave dielectric ceramic material is (1-x) SrAl2O4-xSr3Al2O6, x is more than or equal to 0.15 and less than or equal to 0.2, the aluminate microwave dielectric ceramic material is prepared from aluminate powder and a sintering aid, the sintering aid is KMgF3 powder, and the addition amount of the KMgF3 powder is 3-5% of the mass of the aluminate powder. According to the preparation method disclosed by the invention, stable synthesis of the reinforced phase Sr3Al2O4 can be realized through a two-step calcining method, KMgF3 is selected as a sintering aid, the SrAl2O4-based microwave dielectric ceramic material with low loss and near zero temperature excursion is obtained, and meanwhile, the sintering temperature of the SrAl2O4-based microwave dielectric ceramic material is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, specifically an aluminate microwave dielectric ceramic material and its preparation method. Background Technology

[0002] In modern high-frequency electronic devices such as 5G millimeter-wave communication, satellite navigation RF front-ends, and high-speed data transmission modules, the performance of microwave dielectric ceramic materials directly determines the miniaturization degree, signal transmission efficiency, and operational stability of the devices. Among these, low dielectric constant (ε) r <10), quality factor (Q×f >50000 GHz), temperature coefficient of near-zero resonant frequency (τ) f The core technical requirement is a performance combination of approximately ±10 ppm / ℃. A low dielectric constant shortens signal transmission delay, adapting to the miniaturization design of high-frequency devices; a high quality factor reduces signal attenuation, ensuring long-distance communication and high sensitivity; and a near-zero temperature coefficient ensures stable device performance in a wide operating temperature range of -40℃ to 85℃, avoiding signal drift caused by temperature fluctuations. However, existing microwave dielectric ceramic materials struggle to simultaneously meet these three performance requirements.

[0003] SrAl2O4 is a promising low-dielectric-constant microwave dielectric ceramic material system with low dielectric constant and high quality factor. However, the high sintering temperature (>1400℃) and large temperature coefficient (>-70ppm℃) of SrAl2O4 limit its further application. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide an aluminate microwave dielectric ceramic material with high quality factor and near-zero temperature coefficient of resonant frequency, and a method for preparing the same.

[0005] The technical solution adopted by this invention to achieve its technical objectives is as follows:

[0006] This invention provides an aluminate microwave dielectric ceramic material with the chemical composition of (1-x)SrAl2O4-xSr3Al2O6, 0.15≤x≤0.2, which is made of aluminate powder and sintering aid. The sintering aid is KMgF3 powder, and the amount of KMgF3 powder added is 3~5% of the mass of aluminate powder.

[0007] Furthermore, the aluminate microwave dielectric ceramic material has a relative permittivity of 7.52~8.77, a quality factor of 58240~72483GHz, and a resonant frequency temperature coefficient of -10~8ppm / ℃.

[0008] The present invention also provides a method for preparing the above-mentioned aluminate microwave dielectric ceramic material, comprising the following steps:

[0009] Step 1: Weigh KF and MgF2 powders according to stoichiometric ratio in a glove box under N2 atmosphere, grind and sieve them;

[0010] Step 2: Take out the material obtained in Step 1 and place it in a tube furnace for calcination under N2 atmosphere and keep warm;

[0011] Step 3: Weigh SrCO3 and Al2O3 powders according to the stoichiometric ratio, mix them evenly by wet ball milling, and then dry them.

[0012] Step four: Place the product obtained in step three into a box-type muffle furnace for two-step calcination and heat preservation;

[0013] Step 5: Mix the powders obtained in Step 2 and Step 4 evenly by wet ball milling, and then dry them;

[0014] Step six: After shaping the powder obtained in step five into a blank, sinter it to obtain an aluminate microwave dielectric ceramic material.

[0015] Furthermore, in step one, the grinding time is 30~60 minutes.

[0016] Furthermore, in step two, the calcination temperature is 750~850℃, and the holding time is 2~4h.

[0017] Furthermore, in step three, the wet ball milling speed is 200~250 r / min, and the time is 12~16 h.

[0018] Furthermore, in step four, the two-step calcination involves first heating to 700-800℃ and holding for 0.5-2 hours, then continuing to heat to 900-1000℃ and holding for 2-4 hours.

[0019] Furthermore, in step five, the wet ball milling speed is 300~350 r / min, and the time is 4~6 h.

[0020] Furthermore, in step six, the sintering temperature is 1050~1150℃, the holding time is 3~5h, after the holding time is completed, the temperature is lowered to 500~600℃ at a rate of 3~5℃, and then allowed to cool naturally.

[0021] Preparation principle: In this invention, (1-x)SrAl2O4-xSr3Al2O6 multiphase ceramic materials were synthesized in situ using a traditional solid-state method. Due to the influence of wet ball milling, the mixed powder of SrCO3 and Al2O3 easily forms Sr3Al2(OH) under high-temperature calcination. 12Since the synthesis temperature of Sr3Al2O6 is lower than that of SrAl2O4, a two-step calcination method can be used to achieve stable synthesis of the reinforcing phase Sr3Al2O6. Sr3Al2O6, as the reinforcing phase, adjusts the temperature coefficient of the ceramic system to near zero. Furthermore, low-melting-point KMgF3 is introduced as a sintering aid into the (1-x)SrAl2O4-xSr3Al2O6 system. Through a liquid-phase sintering mechanism, it alleviates the negative effect of high porosity associated with multiphase ceramics, not only lowering the sintering temperature of the ceramic material but also improving its sintering density and ultimately enhancing the material's quality factor.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0023] 1. The two-step calcination method promotes the stable formation of the reinforcing phase Sr3Al2O6, thereby realizing the in-situ synthesis of (1-x)SrAl2O4-xSr3Al2O6 multiphase ceramic material, which is beneficial to the near-zero temperature coefficient of the resonant frequency of the ceramic system.

[0024] 2. By selecting KMgF3 as a sintering aid, the sintering temperature of the ceramic material was reduced, while its sintering density was improved, enabling the (1-x)SrAl2O4-xSr3Al2O6 multiphase ceramic system to achieve the performance characteristics of low-temperature sintering and high quality factor. Attached Figure Description

[0025] Figure 1 This is the XRD pattern of the aluminate microwave dielectric ceramic material prepared in Example 3 of the present invention;

[0026] Figure 2 This is the XRD pattern of the aluminate microwave dielectric ceramic material prepared in Comparative Example 1 of this invention;

[0027] Figure 3 This is a SEM image of the aluminate microwave dielectric ceramic material prepared in Example 3 of the present invention;

[0028] Figure 4 This is a SEM image of the aluminate microwave dielectric ceramic material prepared in Comparative Example 2 of this invention. Detailed Implementation

[0029] The present invention will now be described in detail with reference to specific embodiments. The following specific embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way.

[0030] Unless otherwise specified, all materials, reagents, and instruments used in the following examples are commercially available. Experimental methods not specifically described in the examples are generally performed under standard conditions or as recommended by the manufacturer.

[0031] Example 1

[0032] A method for preparing an aluminate microwave dielectric ceramic material includes the following steps:

[0033] (1) Weigh KF and MgF2 raw material powders in a glove box under N2 atmosphere according to stoichiometric ratio, and grind and mix KF and MgF2 powders by hand for 30 minutes, and pass them through a 200-mesh sieve.

[0034] (2) After taking the KF and MgF2 mixed powder out of the glove box, place it in a tube furnace and calcine it at 750°C under N2 atmosphere for 2 hours to synthesize sintering aid KMgF3 powder.

[0035] (3) The aluminate ceramic composition is 0.85SrAl2O4-0.15Sr3Al2O6. SrCO3 and Al2O3 raw material powders are weighed according to the stoichiometric ratio, with a total mass of 40g. They are ball-milled at a speed of 200r / min for 12h by wet ball milling.

[0036] (4) After the ball milled powder is dried, it is placed in a high-temperature muffle furnace for two-step calcination: first, the temperature is raised to 800℃ and held for 0.5h, and then the temperature is raised to 1000℃ and held for 2h.

[0037] (5) The powder after calcination in step (4) was mixed with 1.2g of KMgF3 powder by wet ball milling at a speed of 300r / min for 5h.

[0038] (6) After ball milling, the dried powder is pressed into a blank and sintered in a high-temperature muffle furnace at a temperature of 1150℃ for 4 hours. After the holding time is over, the temperature is reduced to 550℃ at a rate of 4℃ / min and then cooled naturally to obtain aluminate microwave dielectric ceramic material.

[0039] Example 2

[0040] A method for preparing an aluminate microwave dielectric ceramic material includes the following steps:

[0041] (1) Weigh KF and MgF2 raw material powders in a glove box under N2 atmosphere according to stoichiometric ratio, and grind and mix KF and MgF2 powders by hand for 40 min, and pass them through a 200 mesh sieve.

[0042] (2) After taking the KF and MgF2 mixed powder out of the glove box, place it in a tube furnace and calcine at 800°C under N2 atmosphere for 3 hours to synthesize sintering aid KMgF3 powder.

[0043] (3) The aluminate ceramic composition is 0.84SrAl2O4-0.16Sr3Al2O6. SrCO3 and Al2O3 raw material powders are weighed according to the stoichiometric ratio, with a total mass of 40g. They are ball-milled for 13h at a speed of 225r / min by wet ball milling.

[0044] (4) After the ball milled powder is dried, it is placed in a high-temperature muffle furnace for two-step calcination: first, the temperature is raised to 750℃ and held for 1 hour, and then the temperature is raised to 950℃ and held for 2 hours.

[0045] (5) The powder after calcination in step (4) was mixed with 1.6g of KMgF3 powder by wet ball milling at a speed of 325r / min for 6h.

[0046] (6) After ball milling, the dried powder is pressed into a blank and sintered in a high-temperature muffle furnace at a temperature of 1100℃ for 5 hours. After the holding time is over, the temperature is reduced to 500℃ at a rate of 5℃ / min and then cooled naturally to obtain aluminate microwave dielectric ceramic material.

[0047] Example 3

[0048] A method for preparing an aluminate microwave dielectric ceramic material includes the following steps:

[0049] (1) Weigh KF and MgF2 raw material powders in a glove box under N2 atmosphere according to stoichiometric ratio, and grind and mix KF and MgF2 powders by hand for 30 minutes, and pass them through a 200-mesh sieve.

[0050] (2) After taking the KF and MgF2 mixed powder out of the glove box, place it in a tube furnace and calcine at 850°C under N2 atmosphere for 4 hours to synthesize sintering aid KMgF3 powder.

[0051] (3) The aluminate ceramic composition is 0.83SrAl2O4-0.17Sr3Al2O6. SrCO3 and Al2O3 raw material powders are weighed according to the stoichiometric ratio, with a total mass of 40g. The powders are ball-milled at a speed of 225r / min for 16h by wet ball milling.

[0052] (4) After the ball milled powder is dried, it is placed in a high-temperature muffle furnace for two-step calcination: first, the temperature is raised to 700℃ and held for 2 hours, and then the temperature is raised to 900℃ and held for 3 hours.

[0053] (5) The powder calcined in step (4) was mixed with 1.6g of KMgF3 powder by wet ball milling at a speed of 350r / min for 4h.

[0054] (6) After ball milling, the dried powder is pressed into a blank and sintered in a high-temperature muffle furnace at a temperature of 1050℃ for 3 hours. After the holding time is over, the temperature is reduced to 600℃ at a rate of 3℃ / min and then cooled naturally to obtain aluminate microwave dielectric ceramic material.

[0055] Example 4

[0056] A method for preparing an aluminate microwave dielectric ceramic material includes the following steps:

[0057] (1) Weigh KF and MgF2 raw material powders in a glove box under N2 atmosphere according to stoichiometric ratio, and grind and mix KF and MgF2 powders by hand for 50 min, and pass them through a 200 mesh sieve.

[0058] (2) After taking the KF and MgF2 mixed powder out of the glove box, place it in a tube furnace and calcine at 800°C under N2 atmosphere for 2 hours to synthesize sintering aid KMgF3 powder.

[0059] (3) The aluminate ceramic composition is 0.82SrAl2O4-0.18Sr3Al2O6. SrCO3 and Al2O3 raw material powders are weighed according to the stoichiometric ratio, with a total mass of 40g. They are ball-milled at a speed of 250r / min for 14h by wet ball milling.

[0060] (4) After the ball milled powder is dried, it is placed in a high-temperature muffle furnace for two-step calcination: first, the temperature is raised to 750℃ and held for 1 hour, and then the temperature is raised to 1000℃ and held for 4 hours.

[0061] (5) The powder calcined in step (4) was mixed with 2.0 g of KMgF3 powder by wet ball milling at a speed of 325 r / min for 6 h.

[0062] (6) After ball milling, the dried powder is pressed into a blank and sintered in a high-temperature muffle furnace at a temperature of 1100℃ for 5 hours. After the holding time is over, the temperature is reduced to 500℃ at a rate of 4℃ / min and then cooled naturally to obtain aluminate microwave dielectric ceramic material.

[0063] Example 5

[0064] A method for preparing an aluminate microwave dielectric ceramic material includes the following steps:

[0065] (1) Weigh KF and MgF2 raw material powders in a glove box under N2 atmosphere according to stoichiometric ratio, and grind and mix KF and MgF2 powders by hand for 60 min, and pass them through a 200 mesh sieve.

[0066] (2) After taking the KF and MgF2 mixed powder out of the glove box, place it in a tube furnace and calcine it at 750°C under N2 atmosphere for 3 hours to synthesize sintering aid KMgF3 powder.

[0067] (3) The aluminate ceramic composition is 0.8SrAl2O4-0.2Sr3Al2O6. SrCO3 and Al2O3 raw material powders are weighed according to the stoichiometric ratio, with a total mass of 40g. They are ball-milled at a speed of 250r / min for 15h by wet ball milling.

[0068] (4) After the ball milled powder is dried, it is placed in a high-temperature muffle furnace for two-step calcination: first, the temperature is raised to 700℃ and held for 0.5h, and then the temperature is raised to 950℃ and held for 4h.

[0069] (5) The powder after calcination in step (4) was mixed with 2.0 g of KMgF3 powder by wet ball milling at a speed of 300 r / min for 5 h.

[0070] (6) After ball milling, the dried powder is pressed into a blank and sintered in a high-temperature muffle furnace at a temperature of 1150℃ for 4 hours. After the holding time is over, the temperature is reduced to 550℃ at a rate of 3℃ / min and then cooled naturally to obtain aluminate microwave dielectric ceramic material.

[0071] Comparative Example 1

[0072] A method for preparing an aluminate microwave dielectric ceramic material includes the following steps:

[0073] (1) Weigh KF and MgF2 raw material powders in a glove box under N2 atmosphere according to stoichiometric ratio, and grind and mix KF and MgF2 powders by hand for 30 min.

[0074] (2) After taking the KF and MgF2 mixed powder out of the glove box, place it in a tube furnace and calcine at 850°C under N2 atmosphere for 4 hours to synthesize sintering aid KMgF3 powder.

[0075] (3) The aluminate ceramic composition is 0.83SrAl2O4-0.17Sr3Al2O6. SrCO3 and Al2O3 raw material powders are weighed according to the stoichiometric ratio, with a total mass of 40g. The powders are ball-milled at a speed of 225r / min for 16h by wet ball milling.

[0076] (4) After the ball milled powder is dried, it is placed in a high-temperature muffle furnace and calcined at 900℃ for 3 hours.

[0077] (5) The calcined powder was mixed with 1.6g of KMgF3 powder by wet ball milling at a speed of 350r / min for 4h.

[0078] (6) After ball milling, the dried powder is pressed into a blank and sintered in a high-temperature muffle furnace at a temperature of 1200℃ for 3 hours. After the holding time is over, the temperature is reduced to 600℃ at a rate of 3℃ / min and then cooled naturally to obtain aluminate microwave dielectric ceramic material.

[0079] Comparative Example 2

[0080] A method for preparing an aluminate microwave dielectric ceramic material includes the following steps:

[0081] (1) Weigh KF and MgF2 raw material powders in a glove box under N2 atmosphere according to stoichiometric ratio, and grind and mix KF and MgF2 powders by hand for 30 min.

[0082] (2) After taking the KF and MgF2 mixed powder out of the glove box, place it in a tube furnace and calcine at 850°C under N2 atmosphere for 4 hours to synthesize sintering aid KMgF3 powder.

[0083] (3) The aluminate ceramic composition is 0.83SrAl2O4-0.17Sr3Al2O6. SrCO3 and Al2O3 raw material powders are weighed according to the stoichiometric ratio, with a total mass of 40g. The powders are ball-milled at a speed of 225r / min for 16h by wet ball milling.

[0084] (4) After the ball milled powder is dried, it is placed in a high-temperature muffle furnace for two-step calcination: first, the temperature is raised to 700℃ and held for 2 hours, and then the temperature is raised to 900℃ and held for 3 hours.

[0085] (5) The calcined powder was ground by wet ball milling at a speed of 350 r / min for 4 h.

[0086] (6) After ball milling, the dried powder is pressed into a blank and sintered in a high-temperature muffle furnace at a temperature of 1250℃ for 3 hours. After the holding time is over, the temperature is reduced to 600℃ at a rate of 3℃ / min and then cooled naturally to obtain aluminate microwave dielectric ceramic material.

[0087] Table 1. Material properties obtained in Examples 1-5 and Comparative Examples 1-2

[0088]

[0089] Examples 1-5 of this invention demonstrate the microwave dielectric properties and sintering properties of aluminate microwave dielectric ceramic materials under different formulations and processing conditions. The ceramic sample prepared in Example 3 exhibits the highest quality factor, a near-zero temperature coefficient of resonant frequency, and the lowest sintering temperature, making it the optimal example. The phase composition is as follows: Figure 1As shown, the chemical formula is 0.83SrAl2O4-0.17Sr3Al2O6. In Comparative Example 1, the two-step calcination process was not introduced during the calcination of SrCO3 and Al2O3 powders, as shown in the figure. Figure 2 As shown, the second phase in the powder transforms from Sr3Al2O6 to Sr3Al2(OH). 12 This is unfavorable because the temperature coefficient of the resonant frequency of ceramic materials is close to zero; in Comparative Example 2, no KMgF3 sintering aid was introduced during the secondary ball milling process, compared to Example 3 (such as...). Figure 3 As shown), the porosity of ceramic materials increases, and their density decreases (e.g. Figure 4 As shown in the figure, this causes a significant decrease in the quality factor of ceramic materials and an increase in sintering temperature.

[0090] Obviously, the above embodiments of the present invention are merely examples to illustrate the present invention more clearly, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all implementation methods here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. An aluminate microwave dielectric ceramic material, the chemical composition of which is (1-x)SrAl2O4-xSr3Al2O6, 0.15≤x≤0.2, is made of aluminate powder and sintering aid, wherein the sintering aid is KMgF3 powder, and the amount of KMgF3 powder added is 3~5% of the mass of aluminate powder.

2. The aluminate microwave dielectric ceramic material according to claim 1, characterized in that, The aluminate microwave dielectric ceramic material has a relative permittivity of 7.52~8.77, a quality factor of 58240~72483GHz, and a resonant frequency temperature coefficient of -10~8ppm / ℃.

3. A method for preparing an aluminate microwave dielectric ceramic material according to claim 1 or 2, comprising the following steps: Step 1: Weigh KF and MgF2 powders according to stoichiometric ratio in a glove box under N2 atmosphere, grind and sieve them; Step 2: Take out the material obtained in Step 1 and place it in a tube furnace for calcination under N2 atmosphere and keep warm; Step 3: Weigh SrCO3 and Al2O3 powders according to the stoichiometric ratio, mix them evenly by wet ball milling, and then dry them. Step four: Place the product obtained in step three into a box-type muffle furnace for two-step calcination and heat preservation; Step 5: Mix the powders obtained in Step 2 and Step 4 evenly by wet ball milling, and then dry them; Step six: After shaping the powder obtained in step five into a blank, sinter it to obtain an aluminate microwave dielectric ceramic material.

4. The preparation method according to claim 3, characterized in that, In step one, the grinding time is 30~60 minutes.

5. The preparation method according to claim 3, characterized in that, In step two, the calcination temperature is 750~850℃, and the holding time is 2~4h.

6. The preparation method according to claim 3, characterized in that, In step three, the wet ball milling speed is 200~250 r / min, and the time is 12~16 h.

7. The preparation method according to claim 3, characterized in that, In step four, the two-step calcination involves first heating to 700-800℃ and holding for 0.5-2 hours, then continuing to heat to 900-1000℃ and holding for 2-4 hours.

8. The preparation method according to claim 3, characterized in that, In step five, the wet ball milling speed is 300~350 r / min, and the time is 4~6 h.

9. The preparation method according to claim 3, characterized in that, In step six, the sintering temperature is 1050~1150℃, and the holding time is 3~5h.

10. The preparation method according to claim 9, characterized in that, In step six, after the heat preservation is completed, the temperature is lowered to 500~600℃ at a rate of 3~5℃, and then allowed to cool naturally.

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