BaAl2O4-based microwave dielectric ceramic material and preparation method thereof

Abstract

The invention provides a BaAl2O4-based microwave dielectric ceramic material and a preparation method thereof, and the chemical composition of the BaAl2O4-based microwave dielectric ceramic material is as follows: 0.005 < = < = 0.02. According to the invention, high quality factor and low-temperature sintering of the BaAl2O4-based microwave dielectric ceramic material are realized by a method of A-site and B-site non-equivalent ion synergistic modification (La / Co); the stability of the microstructure of the BaAl2O4 material is enhanced through a modified raw material premixing process (La2O3 + CoO), and the sintering compactness of the ceramic material is improved, so that the quality factor of the material is further improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic materials, and particularly relates to a BaAl2O4-based microwave dielectric ceramic material and a preparation method thereof. BACKGROUND

[0002] Microwave dielectric ceramic is a new generation of core functional material in the field of information communication, which has the unique performance of high dielectric constant, low dielectric loss and near-zero resonance frequency temperature coefficient, and can realize efficient transmission and accurate control of microwave signals. With the rapid iteration of 5G / 6G communication, Internet of Things and satellite navigation technology, traditional ceramic materials have been difficult to meet the demand of high frequency and miniaturization devices, and the component design, micro-control and performance optimization of new microwave dielectric ceramic have become a research hotspot.

[0003] BaAl2O4 is a microwave dielectric ceramic system with great application potential, which has the performance advantages of low relative dielectric constant and high quality factor. However, the sintering temperature of pure BaAl2O4 ceramic material is too high (>1400 o C), and the quality factor still has a large space for improvement. The mainstream low-temperature sintering method is to add a sintering aid, but this method will greatly reduce the quality factor. SUMMARY

[0004] In order to overcome the deficiencies in the prior art, the application aims to provide a BaAl2O4-based microwave dielectric ceramic material and a preparation method thereof, which takes into account the high quality factor and low-temperature sintering of the BaAl2O4-based microwave dielectric ceramic material.

[0005] The technical scheme adopted by the application to achieve the above-mentioned purpose is:

[0006] The application provides a BaAl2O4-based microwave dielectric ceramic material, which has the following chemical composition: , wherein 0.005<= <=0.02.

[0007] Further, the relative dielectric constant of the BaAl2O4-based microwave dielectric ceramic material is 8.31-9.52, the quality factor is 75242-92561 GHz, and the resonance frequency temperature coefficient is -62--68 ppm / ℃.

[0008] The application also provides a preparation method of the above-mentioned BaAl2O4-based microwave dielectric ceramic material, which comprises the following steps:

[0009] Step one, weigh La2O3 and CoO powders according to the stoichiometric ratio, grind and sieve;

[0010] Step two, the mixed powder of step one (La2O3+CoO) is mixed with BaCO3 and Al2O3 powder weighed according to the stoichiometric ratio by wet ball milling, drying;

[0011] Step three, the powder obtained in step two is placed in a muffle furnace for high temperature calcination;

[0012] Step four, the powder obtained in step three is taken out, mixed uniformly by wet ball milling, drying;

[0013] Step five, the powder obtained by drying in step four is made into a blank, sintered, cooled, to obtain a BaAl2O4-based microwave dielectric ceramic material.

[0014] Further, in step one, La2O3 and CoO powder weighed according to the stoichiometric ratio is mixed uniformly by hand grinding in a mortar, and the grinding time is 20-30 min.

[0015] Further, in step two, the rotation speed of wet ball milling is 150-200 r / min, and the time is 6-8 h.

[0016] Further, in step three, the high temperature calcination temperature is 800-900 DEG C, and the holding time is 2-4 h.

[0017] Further, in step four, the rotation speed of wet ball milling is 250-350 r / min, and the time is 12-16 h.

[0018] Further, in step five, the forming pressure of blank making is 250-300 MPa, and the pressure holding time is 15-30 s.

[0019] Further, in step five, the sintering temperature is 1100-1200 DEG C, and the holding time is 4-6 h.

[0020] Further, in step five, the cooling rate is 1-3 DEG C, and the natural cooling is carried out after being cooled to 750-850 DEG C.

[0021] Preparation principle: in the present application, two kinds of nonequivalent ions La 3+ , Co 2+ replace A-site Ba + and B-site Al 3+ in BaAl2O4 respectively, forming a solid solution structure, and the appropriate La / Co cooperative modification realizes the stability of the crystal structure by the strategy of charge compensation, and also reduces the dielectric loss caused by the non-harmonic term in the crystal by using the local crystal structure distortion, so as to realize the reduction of sintering temperature and quality factor (Q* f). The improvement of the quality factor (Q value). In addition, the premixing of raw materials La2O3 and CoO in the preparation process compensates for the local charge loss caused by the unequal doping and inhibits the formation of cation defects, realizes the stability of the microstructure of BaAl2O4 material, improves the sintering density of the ceramic material, and further improves the quality factor of the material.

[0022] Advantages: Compared with the prior art, the present application has the following remarkable features:

[0023] 1. The method of modifying (La / Co) by A and B site unequal ions realizes high quality factor and low temperature sintering of BaAl2O4-based microwave dielectric ceramic material.

[0024] 2. The modification raw material premixing process (La2O3+CoO) strengthens the stability of the microstructure of BaAl2O4 material, improves the sintering density of the ceramic material, and further improves the quality factor of the material. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the XRD pattern of the BaAl2O4-based microwave dielectric ceramic material prepared in Example 3 of the present application;

[0026] Figure 2 is the SEM pattern of the BaAl2O4-based microwave dielectric ceramic material prepared in Example 3 of the present application;

[0027] Figure 3 is the SEM pattern of the BaAl2O4-based microwave dielectric ceramic material prepared in Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0028] The present application will be described in detail below in conjunction with specific embodiments, and the following specific embodiments are helpful for those skilled in the art to further understand the present application, but do not limit the present application in any form.

[0029] The materials, reagents, instruments, etc. used in the following examples can be obtained from commercial channels unless otherwise specified. The experimental methods in the examples not specified in the specific conditions are usually carried out according to the conventional conditions or according to the conditions recommended by the manufacturer.

[0030] Example 1

[0031] A preparation method of a BaAl2O4-based microwave dielectric ceramic material, comprising the following steps:

[0032] (1) The ceramic components are Ba 0.995 La 0.005 Al 1.995 Co 0.005O4, weigh the La2O3 and CoO raw material powders according to the stoichiometric ratio, grind and mix the La2O3 and CoO powders by hand for 20 minutes, and pass them through a 400-mesh sieve;

[0033] (2) The BaCO3 and Al2O3 powders weighed according to the stoichiometric ratio and the premixed (La2O3+CoO) powder were ball-milled at a speed of 150 r / min for 6 h by wet ball milling.

[0034] (3) After drying the powder obtained by wet ball milling, place it in a high-temperature muffle furnace and calcine it at 800℃ for 2 hours;

[0035] (4) The calcined powder was subjected to a second wet ball milling at a speed of 250 r / min for 12 h.

[0036] (5) After secondary ball milling and drying, the powder is pressed into a green body with a molding pressure of 250 MPa and a holding time of 15 s. The green body is then placed in a high-temperature muffle furnace for sintering at a temperature of 1150 °C and a holding time of 4 h. After the holding time, the temperature is reduced to 750 °C at a cooling rate of 1 °C and then cooled naturally to obtain the BaAl2O4-based microwave dielectric ceramic material of the present invention.

[0037] Example 2

[0038] A method for preparing a BaAl2O4-based microwave dielectric ceramic material includes the following steps:

[0039] (1) The ceramic component is Ba 0.993 La 0.007 Al 1.993 Co 0.007 O4, weigh the La2O3 and CoO raw material powders according to the stoichiometric ratio, grind and mix the La2O3 and CoO powders by hand for 25 minutes, and pass them through a 400-mesh sieve;

[0040] (2) The BaCO3 and Al2O3 powders weighed according to the stoichiometric ratio and the premixed (La2O3+CoO) powder were ball-milled at a speed of 175 r / min for 7 h by wet ball milling.

[0041] (3) After drying the powder obtained by wet ball milling, place it in a high-temperature muffle furnace and calcine it at 820℃ for 3 hours;

[0042] (4) The calcined powder was subjected to a second wet ball milling at a speed of 275 r / min for 14 h.

[0043] (5) After secondary ball milling and drying, the powder is pressed into a green body with a molding pressure of 280 MPa and a holding time of 20 s. The green body is placed in a high-temperature muffle furnace for sintering at a temperature of 1150 ℃ and a holding time of 4 h. After the holding time, the temperature is reduced to 800 ℃ at a cooling rate of 1 ℃ and then naturally cooled to obtain the BaAl2O4-based microwave dielectric ceramic material of the present invention.

[0044] Example 3

[0045] A method for preparing a BaAl2O4-based microwave dielectric ceramic material includes the following steps:

[0046] (1) The ceramic component is Ba 0.99 La 0.01 Al 1.99 Co 0.01 O4, weigh the La2O3 and CoO raw material powders according to the stoichiometric ratio, grind and mix the La2O3 and CoO powders by hand for 30 minutes, and pass them through a 400-mesh sieve;

[0047] (2) The BaCO3 and Al2O3 powders weighed according to the stoichiometric ratio and the premixed (La2O3+CoO) powder were ball-milled at a speed of 200 r / min for 8 h by wet ball milling;

[0048] (3) After drying the powder obtained by wet ball milling, place it in a high-temperature muffle furnace and calcine it at 840℃ for 3 hours;

[0049] (4) The calcined powder was subjected to a second wet ball milling at a speed of 300 r / min for 13 h.

[0050] (5) After secondary ball milling and drying, the powder is pressed into a green body with a molding pressure of 300 MPa and a holding time of 25 s. The green body is then placed in a high-temperature muffle furnace for sintering at a temperature of 1100 ℃ and a holding time of 6 h. After the holding time, the temperature is reduced to 850 ℃ at a cooling rate of 2 ℃ and then cooled naturally to obtain the BaAl2O4-based microwave dielectric ceramic material of the present invention.

[0051] Example 4

[0052] A method for preparing a BaAl2O4-based microwave dielectric ceramic material includes the following steps:

[0053] (1) The ceramic component is Ba 0.985 La 0.015 Al 1.985 Co 0.015 O4, weigh the La2O3 and CoO raw material powders according to the stoichiometric ratio, grind and mix the La2O3 and CoO powders by hand for 20 minutes, and pass them through a 400-mesh sieve;

[0054] (2) The BaCO3 and Al2O3 powders weighed according to the stoichiometric ratio and the premixed (La2O3+CoO) powder were ball-milled at a speed of 175 r / min for 6 h by wet ball milling.

[0055] (3) After drying the powder obtained by wet ball milling, place it in a high-temperature muffle furnace and calcine it at 880℃ for 4 hours;

[0056] (4) The calcined powder was subjected to a second wet ball milling at a speed of 350 r / min for 15 h.

[0057] (5) After secondary ball milling and drying, the powder is pressed into a green body with a molding pressure of 250 MPa and a holding time of 30 s. The green body is then placed in a high-temperature muffle furnace for sintering at a temperature of 1200 ℃ and a holding time of 6 h. After the holding time, the temperature is reduced to 800 ℃ at a cooling rate of 2 ℃ and then cooled naturally to obtain the BaAl2O4-based microwave dielectric ceramic material of the present invention.

[0058] Example 5

[0059] A method for preparing a BaAl2O4-based microwave dielectric ceramic material includes the following steps:

[0060] (1) The ceramic component is Ba 0.98 La 0.02 Al 1.98 Co 0.02 O4, weigh the La2O3 and CoO raw material powders according to the stoichiometric ratio, grind and mix the La2O3 and CoO powders by hand for 25 minutes, and pass them through a 400-mesh sieve;

[0061] (2) The BaCO3 and Al2O3 powders weighed according to the stoichiometric ratio and the premixed (La2O3+CoO) powder were ball-milled at a speed of 150 r / min for 7 h by wet ball milling.

[0062] (3) After drying the powder after wet ball milling, place it in a high-temperature muffle furnace and calcine it at 900℃ for 4 hours;

[0063] (4) The calcined powder was subjected to a second wet ball milling at a speed of 325 r / min for 16 h.

[0064] (5) After secondary ball milling and drying, the powder is pressed into a green body with a molding pressure of 300 MPa and a holding time of 20 s. The green body is then placed in a high-temperature muffle furnace for sintering at a temperature of 1200 ℃ and a holding time of 5 h. After the holding time is completed, the temperature is reduced to 750 ℃ ​​at a cooling rate of 3 ℃ and then cooled naturally to obtain the BaAl2O4-based microwave dielectric ceramic material of the present invention.

[0065] Comparative Example 1

[0066] A method for preparing a BaAl2O4-based microwave dielectric ceramic material includes the following steps:

[0067] (1) The ceramic component is Ba 0.99 La 0.01 Al2O4: BaCO3, Al2O3 and La2O3 powders weighed according to stoichiometric ratio were ball-milled at 200 r / min for 8 h using a wet ball milling method.

[0068] (2) After drying the powder obtained by wet ball milling, place it in a high-temperature muffle furnace and calcine it at 840℃ for 3 hours;

[0069] (3) The calcined powder was subjected to a second wet ball milling at a speed of 300 r / min for 13 h.

[0070] (4) After secondary ball milling and drying, the powder was pressed into a green body at a molding pressure of 300 MPa and a holding time of 25 s. The green body was then placed in a high-temperature muffle furnace for sintering at a temperature of 1250 ℃ and a holding time of 6 h. After the holding time, the temperature was reduced to 850 ℃ at a cooling rate of 2 ℃, and then allowed to cool naturally to obtain La at site A. 3+ Doped BaAl2O4 ceramic sample.

[0071] Comparative Example 2

[0072] A method for preparing a BaAl2O4-based microwave dielectric ceramic material includes the following steps:

[0073] (1) The ceramic composition is BaAl 1.99 Co 0.01 O4, BaCO3, Al2O3 and CoO powders weighed according to stoichiometric ratio were ball-milled at 200 r / min for 8 h by wet ball milling;

[0074] (2) After drying the powder obtained by wet ball milling, place it in a high-temperature muffle furnace and calcine it at 840℃ for 3 hours;

[0075] (3) The calcined powder was subjected to a second wet ball milling at a speed of 300 r / min for 13 h.

[0076] (4) After secondary ball milling and drying, the powder was pressed into a green body at a molding pressure of 300 MPa and a holding time of 25 s. The green body was then placed in a high-temperature muffle furnace for sintering at a temperature of 1300 ℃ and a holding time of 6 h. After the holding time, the temperature was reduced to 850 ℃ at a cooling rate of 2 ℃, and then allowed to cool naturally to obtain Co at the B site. 2+ Doped BaAl2O4 ceramic sample.

[0077] Comparative Example 3

[0078] A method for preparing a BaAl2O4-based microwave dielectric ceramic material includes the following steps:

[0079] (1) The ceramic component is Ba 0.99 La 0.01 Al 1.99 Co 0.01 O4, BaCO3, Al2O3, La2O3 and CoO powders weighed according to stoichiometric ratio were ball-milled at 200 r / min for 8 h by wet ball milling;

[0080] (2) After drying the powder obtained by wet ball milling, place it in a high-temperature muffle furnace and calcine it at 840℃ for 3 hours;

[0081] (3) The calcined powder was subjected to a second wet ball milling at a speed of 300 r / min for 13 h.

[0082] (4) After the powder is dried by secondary ball milling, it is pressed into a green body with a molding pressure of 300 MPa and a holding time of 25 s. The green body is placed in a high-temperature muffle furnace for sintering at a temperature of 1250 ℃ and a holding time of 6 h. After the holding time is completed, the temperature is reduced to 850 ℃ at a cooling rate of 2 ℃ and then cooled naturally to obtain BaAl2O4-based microwave dielectric ceramic material.

[0083] Table 1. Material properties obtained in Examples 1-5 and Comparative Examples 1-3

[0084]

[0085] Examples 1-5 of this invention demonstrate the microwave dielectric properties and sintering properties of BaAl2O4-based microwave dielectric ceramic materials under different formulations and processing conditions. The ceramic sample prepared in Example 3 exhibits the highest quality factor and the best temperature coefficient of resonant frequency, making it the optimal example. The phase composition is as follows: Figure 1 As shown, the main phase is Ba. 0.99 La 0.01 Al 1.99 Co 0.01 O4 solid solution phase. Comparative Example 1 prepared A-site La 3+ Comparative Example 2 shows the preparation of B-site Co in doped BaAl2O4 ceramic samples. 2+ Compared to Example 3, the doped BaAl2O4 ceramic samples prepared in Comparative Examples 1 and 2 exhibited unsatisfactory performance in terms of quality factor and temperature coefficient of resonant frequency due to the enrichment of cation defects, and the sintering temperature was too high. Comparative Example 3 did not incorporate a (La2O3+CoO) powder premixing process during its preparation. Figure 2 (Example 3) and Figure 3 As shown in Comparative Example 3, the introduction of the premixing process is beneficial to the sintering density of ceramic materials and improves the quality factor of ceramic materials.

[0086] 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. A BaAl2O4-based microwave dielectric ceramic material, the chemical composition of which is as follows: ,in, 0.005≤ ≤0.02。 2. The BaAl2O4-based microwave dielectric ceramic material according to claim 1, characterized in that, The relative permittivity of the BaAl2O4-based microwave dielectric ceramic material is 8.31~9.52, the quality factor is 75242~92561 GHz, and the temperature coefficient of resonant frequency is -62~-68 ppm / ℃.

3. A method for preparing a BaAl2O4-based microwave dielectric ceramic material according to claim 1 or 2, comprising the following steps: Step 1: Weigh La2O3 and CoO powders according to the stoichiometric ratio, grind and sieve them; Step 2: Mix the (La2O3+CoO) mixed powder obtained in Step 1 with BaCO3 and Al2O3 powders weighed according to stoichiometric ratio by wet ball milling until homogeneous, and then dry. Step 3: Place the powder obtained in Step 2 into a muffle furnace for high-temperature calcination; Step 4: Take out the powder obtained in Step 3, mix it evenly by wet ball milling, and then dry it. Step 5: Take the powder obtained from step 4 and dry it to form a blank, sinter it, and cool it down to obtain BaAl2O4-based microwave dielectric ceramic material.

4. The preparation method according to claim 3, characterized in that, In step one, the La2O3 and CoO powders weighed according to the stoichiometric ratio are manually ground and mixed evenly in a mortar for 20-30 minutes.

5. The preparation method according to claim 3, characterized in that, In step two, the wet ball milling speed is 150~200 r / min, and the time is 6~8 h.

6. The preparation method according to claim 3, characterized in that, In step three, the high-temperature calcination temperature is 800~900℃, and the temperature is maintained for 2~4 hours.

7. The preparation method according to claim 3, characterized in that, In step four, the wet ball milling speed is 250~350 r / min, and the time is 12~16 h.

8. The preparation method according to claim 3, characterized in that, In step five, the forming pressure of the preform is 250~300MPa, and the holding time is 15~30s.

9. The preparation method according to claim 3, characterized in that, In step five, the sintering temperature is 1100~1200℃, and the holding time is 4~6h.

10. The preparation method according to claim 3 or 9, characterized in that, In step five, the cooling rate is 1~3℃, and the temperature is allowed to cool naturally after reaching 750~850℃.

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