Low-dielectric-constant temperature-stable phosphate microwave dielectric ceramic material for LTCC and preparation method of low-dielectric-constant temperature-stable phosphate microwave dielectric ceramic material

Abstract

The invention discloses a low dielectric constant temperature-stable phosphate microwave dielectric ceramic material for LTCC and a preparation method thereof, the chemical composition formula of the phosphate microwave dielectric ceramic material is A3-xK2x (PO4) 2, A = Ba1-ySry, x is more than or equal to 0.1 and less than or equal to 0.5, y is more than or equal to 0 and less than or equal to 1, and the phosphate microwave dielectric ceramic material comprises two phases of A3 (PO4) 2 and KAPO4; the preparation method comprises the following steps: regulating and controlling the A-site ion radius of A3 (PO4) 2-based ceramic, pre-sintering to directly synthesize complex-phase powder containing phases A3 (PO4) 2 and KAPO4 in situ in one step, then adding H3BO3 powder accounting for 1-5% of the total mass of a base material, and carrying out ball milling, drying, sieving, forming, rubber discharging and sintering to obtain a ceramic sample; the ceramic material has a low sintering temperature (850-950 DEG C), a low dielectric constant (epsilon r = 8.9-12.6), a high quality factor (Q * f = 10186-50213 GHz) and a near-zero temperature resonance frequency coefficient (-7.1-7.2 ppm / DEG C), the preparation process is simple, the cost is low, the raw materials are non-toxic and easy to obtain, and the ceramic material is suitable for being used as an LTCC dielectric substrate material and has important industrial application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of microwave dielectric ceramics, and particularly relates to a low-temperature-stable phosphate microwave dielectric ceramic material with low dielectric constant for LTCC and a preparation method thereof. BACKGROUND

[0002] As a kind of dielectric material that can be used in microwave frequency circuits, microwave dielectric ceramics are widely used in the production of electronic components such as filters, oscillators, attenuators, dielectric antennas and dielectric substrates. With the rapid development of Internet and Internet of Things technology, the fifth generation mobile communication technology (5G) is regarded as a key technology in today's big data, cloud computing and artificial intelligence era due to its ultra-high speed, ultra-low latency, ultra-large connection and ultra-large bandwidth. In order to meet the requirements of 5G network technology for microwave circuits and systems in terms of lightweight, miniaturization, high frequency, integration, low power consumption, multi-function, high performance and high stability, microwave dielectric ceramics with low dielectric constant (ε r ), high quality factor (Qxf) and near-zero resonance frequency temperature coefficient (τ f ) are urgently needed to meet the needs of low latency, low energy loss and stable use in different environmental temperatures; at the same time, a low sintering temperature (≤950℃) can meet the requirements of low-temperature co-fired ceramic (LTCC) technology, reduce production costs and be suitable for industrial mass production.

[0003] There are many kinds of microwave dielectric ceramics with low dielectric constant (ε r ≤15), in recent years, phosphate A3(PO4)2(A=Ba or Sr) ceramics have attracted much attention due to their low dielectric constant, high quality factor and no reaction with internal electrode Ag. In 2012, Guo (T. Guo, W. Wu, Y. Wang, Y. Li, Comparison for the crystal structure, synthesis and microwave dielectric properties of alkaline earth orthophosphates, Materials Chemistry and Physics. 134 (2012) 503-507.) et al. first reported the dielectric properties of Ba3(PO4)2 and Sr3(PO4)2 ceramic systems, both of which have low dielectric constant (10.9-12.3) and high quality factor (15640-19626 GHz). However, their resonance frequency temperature coefficients are non-zero positive numbers (+14-66 ppm / ℃) and the sintering temperature is still high (≥1100℃), which limits their application in the field of LTCC.

[0004] Currently, the τ f values of A3(PO4)2(A = Ba or Sr) ceramics are mainly regulated by traditional composite ceramics preparation with ceramics having opposite temperature coefficients of resonant frequency. This method requires the preparation of two or more groups of base materials with different compositions in advance, and then the preparation of ceramic samples after mixing the multiple groups of base materials. For example, Wang (Z. Wang, J. J. Bian, Low temperature sintering and microwave dielectric properties of Ba3(PO4)2-BaWO4 composite ceramics, Ceramics International. 40 (2014) 8507-8511.) et al. prepared Ba3(PO4)2-BaWO4 composite ceramics by traditional composite ceramics preparation and added B2O3 to reduce the sintering temperature. Although this method can adjust the τ f value to near zero while reducing the sintering temperature. However, the preparation of composite ceramics using this method (traditional composite ceramics preparation) requires the synthesis of two groups of component systems, Ba3(PO4)2 and BaWO4, ceramic base materials with different pre-sintering temperatures, which is complicated and inevitably increases the preparation cost. At the same time, impurities are easily introduced, leading to a decrease in the quality factor. Furthermore, due to the large difference in the density of different phases of ceramics, traditional composite ceramics preparation is prone to poor quality stability due to uneven mixing, which is also detrimental to the performance of the material.

[0005] In 2024, Bian (J. J. Bian, H. Wang, High-performance SiO2-Sr3(PO4)2 low-ε dielectric ceramics for MW / THz applications, Journal of the European Ceramic Society. 45 (2025) 116861.) et al. prepared Sr3(PO4)2-SiO2 composite ceramics with a high quality factor and a τ f value close to zero, but the sintering temperature was still high (1150°C), which could not meet the technical requirements of the LTCC process. To further reduce the sintering temperature of the ceramic, low-melting-point glass (with a large dielectric loss) is often doped, which inevitably damages the microwave dielectric properties of the dielectric material. Therefore, the development of ceramic materials with a simple preparation process, excellent comprehensive dielectric properties, and the ability to meet the LTCC process has become a technical problem that needs to be solved in the development of the 5G wireless communication industry. SUMMARY

[0006] In order to overcome the defects and deficiencies existing in the above-mentioned technology, the present application aims to provide a low dielectric constant temperature stable phosphate microwave dielectric ceramic material for LTCC and a preparation method thereof, which is designed in composition, introduces K + The two-phase ceramic containing two phases can be directly generated at a lower sintering temperature, and the temperature coefficients of the two phases are opposite, so that the temperature coefficient of the resonance frequency of the ceramic can be adjusted to near zero.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] Firstly, the present application provides a low dielectric constant temperature stable phosphate microwave dielectric ceramic material for LTCC, which has a chemical composition formula of A 3-x K 2x (PO4)2, wherein A=Ba 1-y Sr y , 0.1≤x≤0.5, 0≤y≤1, and the subscripts in the chemical formula are molar ratios; the phosphate microwave dielectric ceramic material contains two phases of A3(PO4)2 and KAPO4(A=Ba 1-y Sr y , 0≤y≤1), and the mass ratio of the two phases is about 7:3-4:6; in the microstructure, the two phases do not have solid solution reaction, but only have interface bonding, and together form a composite ceramic material.

[0009] Further, the low dielectric constant temperature stable phosphate microwave dielectric ceramic material for LTCC has a low dielectric constant, and the dielectric constant is less than 13, preferably 8.9-12.6, and further preferably 9.9-11.5.

[0010] The τ f value of the low dielectric constant temperature stable phosphate microwave dielectric ceramic material for LTCC is -7.1-7.2 ppm / ℃.

[0011] Preferably, the quality factor of the low dielectric constant temperature stable phosphate microwave dielectric ceramic material for LTCC is 10186-50213 GHz, and further preferably 27316-50213 GHz.

[0012] Secondly, the present application provides a preparation method of the low dielectric constant temperature stable phosphate microwave dielectric ceramic material for LTCC, which specifically comprises the following steps:

[0013] Step one, preparing A 3-x K 2x (PO4)2 powder:

[0014] BaCO3, SrCO3, K2CO3, NH4H2PO4 as raw materials, and the raw materials are weighed according to the molar stoichiometric ratio of the target chemical formula A 3-x K 2x The raw materials are weighed according to the molar stoichiometric ratio of the target chemical formula A 1-y Sr y , 0.1≤x≤0.5, 0≤y≤1, and after mixing, ball milling, drying, sieving, and pre-sintering, A 3-x K 2x (PO4)2 ceramic powder base I is obtained.

[0015] The purity of the above-mentioned BaCO3, SrCO3, K2CO3, and NH4H2PO4 raw materials is greater than 99%.

[0016] Step two, preparation of A 3-x K 2x (PO4)2+H3BO3 mixture:

[0017] A 3-x K 2x (PO4)2 ceramic powder base I is weighed, then H3BO3 powder in an amount of a wt.% (1≤a≤5) of the mass of the ceramic powder base I is added, and secondary ball milling is performed. The secondary ball milling is performed while the pre-sintered A 3-x K 2x (PO4)2 ceramic powder base is being pulverized, so as to fully and uniformly mix the base with the H3BO3 powder, and then drying and sieving are performed to obtain ceramic powder base II. Then, a binder is added, granulation, tabletting, and sintering are performed to obtain a low-temperature co-fired ceramic (LTCC) low-dielectric-constant temperature-stable phosphate microwave dielectric ceramic material.

[0018] The purpose of the ball milling in step one is to fully stir and uniformly mix the weighed powder raw materials. The purpose of the ball milling in step two is to pulverize the pre-sintered A 3-x K 2x (PO4)2 ceramic powder base while fully and uniformly mixing the base with the H3BO3 powder. The parameters of the two ball milling processes can be the same or different. For example, the ball milling speed is 100-150 rpm, and the ball milling time is 12-36 h. In the embodiments of the present application, the ball milling processes in steps one and two are dry three-dimensional rotary ball milling, the ball milling bead material is ZrO2, the ball milling time is 24 h, and the ball milling speed is 150 rpm.

[0019] The purpose of the drying step is to ensure that the powder is completely dry. The parameters of the two drying processes can be the same or different. For example, the drying temperature is 80-120℃, and the drying time is 12-24 h. In the embodiments of the present application, the drying temperature in steps one and two is preferably 80℃, and the drying time is 24 h.

[0020] Preferably, the sieve used in the sieving in step one is a 60 mesh standard sieve, and the sieve used in the sieving in step two is an 80 mesh standard sieve. The sieving in step one is to separate the powder adhered to the ball milling beads and the free powder after the powder is ball milled once, and the sieving is for subsequent use. The step does not require the original particle size of the powder, and considering the efficiency and the diameter of the ball milling beads, the 60 mesh sieve is preferred. The sieving in step two is to control the particle size of the sieved powder to be below a certain mesh number, so that the powder has a certain activity and is convenient for subsequent forming and sintering. Therefore, in an embodiment of the present application, the 80 mesh sieve is preferred.

[0021] Preferably, the pre-sintering temperature in step one is 800℃, the heating rate is 5℃ / min, the pre-sintering holding time is 6h, and the furnace is cooled after the holding time ends. The pre-sintering temperature is a main factor affecting whether the ceramic powder can synthesize the target phase. If the pre-sintering temperature is too low, the powder raw materials cannot react completely, the expected phase nucleus cannot be completely synthesized, and intermediate phases may exist, which affects the subsequent ceramic sintering and dielectric properties. If the pre-sintering temperature is too high, the ceramic powder has a large particle size, and the powder activity is poor, which is also not conducive to subsequent sintering. Therefore, in an embodiment of the present application, the pre-sintering temperature is preferably 800℃.

[0022] Preferably, the binder used in step two is a polyvinyl alcohol (PVA) aqueous solution with a concentration of 8wt.%, and the amount of the polyvinyl alcohol (PVA) aqueous solution added is 10wt.% of the mass of the ceramic powder base II.

[0023] The sintering refers to heating the green body to 550℃ at a heating rate of 1-2℃ / min, holding for 2-4h (to remove the binder); then heating to 850-950℃ at a heating rate of 5℃ / min, holding for 2-6h (to ensure that the ceramic material can be densified), and then cooling in the furnace. In an embodiment of the present application, the green body is first heated to 550℃ at a heating rate of 1.5℃ / min, held for 2h, then heated to 850-950℃ at a heating rate of 5℃ / min, held for 5h, and then cooled in the furnace.

[0024] Preferably, the tabletting in step two refers to using a cylindrical mold with a diameter of 10mm to perform die pressing forming at a pressure of 100-150MPa.

[0025] Compared with the existing preparation technology of the composite ceramic, the composite ceramic provided by the application does not need to pre-synthesize a plurality of different components and base materials of the process, simplifies the process while avoiding the introduction of impurities. At the same time, through reasonable selection and proportioning of components, the problems of the A3(PO4)2 system microwave dielectric ceramic, such as too high intrinsic sintering temperature, too large positive value of resonance frequency temperature coefficient, and complicated traditional composite preparation process and poor quality stability, are effectively solved. The prepared composite material has the characteristics of low sintering temperature, low dielectric constant and low dielectric loss, can effectively improve the signal response speed, reduce heat loss, and enhance the system stability, and can meet the demand of LTCC dielectric substrate material. Compared with the prior art, the advantages and beneficial effects of the application are embodied in:

[0026] (1) The application adopts a dry three-dimensional rotary ball milling method for mixing, which can avoid the problem of microsolubility between the raw materials NH4H2PO4 and HBO3 and solvents such as alcohol or deionized water in the wet ball milling process, and can more accurately ensure the stoichiometric ratio, thereby improving the quality stability.

[0027] (2) The application introduces K ions with larger ionic radius by partially replacing A-site ions of the A3(PO4)2 system ceramic, and generates KAPO4 phase with lower melting point and opposite τ f value than the main phase in situ during the first pre-sintering, which can reduce the sintering temperature and control the τ f value of the A3(PO4)2 system ceramic. The wave dielectric ceramic material has low sintering temperature (850-950℃), low dielectric constant (ε r = 8.9-12.6), high quality factor (Qxf = 10186-50213 GHz) and near-zero temperature resonance frequency coefficient (-7.1-7.2 ppm / ℃), which can effectively improve the signal response speed, reduce heat loss and enhance the system stability, and is very suitable for use as an LTCC dielectric substrate material.

[0028] (3) The application generates KAPO4 phase in situ in one step by ion regulation method, and generates the second phase in situ based on the ion regulation method. Compared with the traditional composite ceramic, the application does not need to synthesize a plurality of different component systems and ceramic powder base materials with different pre-sintering temperatures in advance, simplifies the preparation process, reduces the cost and energy consumption, and reduces the impurities introduced in the production process. The phase distribution is uniform, the quality stability is higher, the raw material cost is low and non-toxic, and it is suitable for industrial mass production. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The physical photos of the 1-5 number microwave dielectric ceramic material prepared in Example 1 of the application before and after sintering.

[0030] Figure 2 XRD pattern of the microwave dielectric ceramic sample material No. 2 prepared in Example 1-3 of the present application.

[0031] Figure 3 SEM backscattered micro-morphology pattern of the microwave dielectric ceramic material No. 2 prepared in Example 2 of the present application. DETAILED DESCRIPTION

[0032] The present application will be further described in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are intended to explain, and not to limit, the present application.

[0033] The raw materials BaCO3, SrCO3, K2CO3, NH4H2PO4, etc. used in the examples were purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd., and the purity of each was greater than 99%. The raw material ratios involved in the examples were all after purity conversion.

[0034] The formula of the LTCC low dielectric constant temperature-stable phosphate microwave dielectric ceramic material comprises a base material and a sintering aid; the base material is A 3-x K 2x (PO4)2, wherein A = Ba 1-y Sr y , 0.1≤x≤0.5, 0≤y≤1; the sintering aid is H3BO3 powder at a wt.% (1≤a≤5) relative to the total mass of the base material.

[0035] Table 5 Composition formula of the mixture

[0036]

[0037]

[0038] The three-dimensional rotary mixer was purchased from Shanghai Binlai Instrument and Equipment Co., Ltd., SYH-0.5 type.

[0039] The vector network analyzer was purchased from Agilent Company, USA, N5244A type.

[0040] Example 1

[0041] The preparation method of the LTCC low dielectric constant temperature-stable phosphate microwave dielectric ceramic material in the present example comprises the following steps:

[0042] First step, batching: the raw materials were weighed according to the requirements of each component described in Table 1 and were batched respectively.

[0043] Second step, first ball milling: the weighed powder was moved into the ball milling tank after being stirred thoroughly and placed in the three-dimensional rotary mixer for first ball milling, with zirconium dioxide as the milling ball, the mass ratio of the powder to the milling ball being 1:5, the ball milling time being 24 h, and the ball milling rotation speed being 150 rpm.

[0044] Third step, pre-sintering: the mixed material after ball milling was dried (dried at 80℃ for 24 h), sieved through a 60-mesh sieve, and then loaded into an alumina ceramic crucible, heated to 800℃ at a heating rate of 5℃ / min, kept for 6 h, and then cooled with the furnace to obtain the pre-sintered ceramic powder base I.

[0045] Fourth step, second ball milling: the ceramic powder base I obtained by pre-sintering was ground, and then mixed powder of the base and H3BO3 powder was prepared according to the requirements of the components in Table 1 and subjected to second ball milling, with the specific process being the same as that of the first ball milling.

[0046] Fifth step, granulation and press forming: the ceramic powder obtained by second ball milling was dried at 80℃ for 24 h, and then sieved through an 80-mesh sieve to obtain ceramic powder base II; 10wt.% PVA aqueous solution (concentration: 8wt.%) was added as a binder to the ceramic powder base II to perform granulation, and then the granulated material was pressed into a green body sample with a diameter of 10 mm and a height of about 5 mm under a pressure of 150 MPa (using a cylindrical mold with a diameter of 10 mm).

[0047] Sixth step, glue removal and sintering: the green body was heated to 550℃ at a heating rate of 2℃ / min, kept for 2 h, and then heated to 850℃ at a heating rate of 5℃ / min, kept for 5 h, and then cooled with the furnace to obtain LTCC low dielectric constant temperature-stable phosphate microwave dielectric ceramic material sample 1 # -1- sample 5 # -1.

[0048] The LTCC low dielectric constant temperature-stable phosphate microwave dielectric ceramic material prepared in this example was subjected to microwave dielectric performance test according to the "open cavity" method of the "Test method for microwave complex permittivity of solid dielectric" (GB / T7265.2-1987 standard) using a vector network analyzer, and the test results are shown in Table 2.

[0049] Table 2 Microwave dielectric performance of the microwave dielectric ceramic material prepared in Example 1

[0050]

[0051] The 1-5 microwave dielectric ceramic material prepared in this example ((1 # -1)~(5 # -1)) before and after sintering is shown in the actual photos of the ceramic samples Figure 1As shown, the sample maintains the appearance of a complete cylinder before and after sintering, and shows a certain size shrinkage after sintering. The XRD pattern of the microwave dielectric ceramic material No. 2 prepared in this embodiment (2 # -1) is shown in FIG. 2. Figure 2 As shown, the phase composition of the ceramic material is Ba3(PO4)2and KBaPO4, and there is no other impurity phase.

[0052] Example 2

[0053] The preparation method of the low dielectric constant temperature stable phosphate microwave dielectric ceramic material for LTCC in this embodiment includes the following steps:

[0054] First step, batching: the raw materials are weighed according to the requirements of each component described in Table 1 and are respectively batched.

[0055] Second step, primary ball milling: the weighed powder is thoroughly stirred and then moved into a ball milling tank and placed in a three-dimensional rotary mixer for primary ball milling, with zirconium dioxide as the milling ball, the mass ratio of the powder to the milling ball being 1:5, the ball milling time being 24 h, and the ball milling speed being 150 rpm.

[0056] Third step, pre-sintering: the mixed material after ball milling is dried (dried at 80℃ for 24 h), sieved through a 60 mesh sieve, and then loaded into an alumina ceramic crucible and heated to 800℃ at a heating rate of 5℃ / min, kept for 6 h, and then cooled with the furnace to obtain a pre-sintered ceramic powder base I.

[0057] Fourth step, secondary ball milling: the ceramic powder base I obtained by pre-sintering is ground, and the mixed powder of the base and H3BO3 powder is prepared according to the requirements of each component described in Table 1 and is subjected to secondary ball milling, with the same process as the primary ball milling.

[0058] Fifth step, granulation and compression molding: the ceramic powder obtained by secondary ball milling is dried at 80℃ for 24 h, sieved through an 80 mesh sieve to obtain base II, 10wt.% of PVA aqueous solution (concentration of 8wt.%) with a weight equal to that of the base II is added as a binder for granulation, and the granulation is compressed into a green body sample with a diameter of 10 mm and a height of about 5 mm under a pressure of 150 Mpa.

[0059] Sixth step, degreasing and sintering: the green body is heated to 550℃ at a heating rate of 2℃ / min and kept for 2 h, and then heated to 900℃ at a heating rate of 5℃ / min and kept for 5 h, and then cooled with the furnace to obtain a low dielectric constant temperature stable phosphate microwave dielectric ceramic material for LTCC 1 # -2~5 # -2.

[0060] The low dielectric constant temperature stable phosphate microwave dielectric ceramic material for LTCC prepared in the embodiment was tested for microwave dielectric properties by a vector network analyzer according to the "open cavity" method of "Test Method for Microwave Complex Permittivity of Solid Dielectric" (GB / T7265.2-1987 standard), and the test results are shown in Table 3.

[0061] Table 3 Microwave dielectric properties of the microwave dielectric ceramic material prepared in Example 2

[0062]

[0063] The XRD pattern and SEM backscattered micro-morphology of the microwave dielectric ceramic material No. 2 prepared in the embodiment (2 # -2) are shown in Figs. 2 and 3, respectively. As can be seen from the figures, the phase composition of the ceramic material is Ba3(PO4)2 and KBaPO4, and there is no other impurity phase. The ceramic grains are uniformly distributed, and the grain boundaries have no obvious pores, showing high density. Figure 2 and Figure 3

[0064] Example 3

[0065] The preparation method of the low dielectric constant temperature stable phosphate microwave dielectric ceramic material for LTCC in the embodiment comprises the following steps:

[0066] First step, batching: the raw materials are weighed according to the requirements of each component described in Table 1 and then batched.

[0067] Second step, primary ball milling: the weighed powder is thoroughly stirred and then moved into a ball milling tank and placed in a three-dimensional rotary mixer for primary ball milling. Zirconium dioxide is used as the milling ball, the mass ratio of the powder to the milling ball is 1:5, the ball milling time is 24 h, and the ball milling speed is 150 rpm.

[0068] Third step, pre-sintering: the mixed material after ball milling is dried (dried at 80 ℃ for 24 h), sieved through a 60 mesh sieve, and then loaded into an alumina ceramic crucible. The temperature is raised to 800 ℃ at a heating rate of 5 ℃ / min, and then held for 6 h before cooling with the furnace to obtain a pre-sintered ceramic powder base I.

[0069] Fourth step, secondary ball milling: the pre-sintered ceramic powder base I is ground, and then the mixed powder of the base and H3BO3 powder is prepared according to the requirements of each component described in Table 1 and then subjected to secondary ball milling. The specific process is the same as that of the primary ball milling.

[0070] ​Fifth step, granulation and compression molding: the ceramic powder obtained by secondary ball milling was dried at 80℃ for 24h, and then sieved through an 80-mesh screen to obtain base II. 10wt.% of a PVA aqueous solution (concentration: 8wt.%) was added to base II as a binder to perform granulation, and the granulated product was compressed into a green sample with a diameter of 10mm and a height of about 5mm under a pressure of 150Mpa.

[0071] Sixth step, degreasing and sintering: the green sample was heated to 550℃ at a heating rate of 2℃ / min, and then heated to 950℃ at a heating rate of 5℃ / min, and then held for 5h. After cooling in the furnace, a low-temperature-stable phosphate microwave dielectric ceramic material 1 for LTCC was obtained. # -3~5 # -3.

[0072] The microwave dielectric properties of the low-temperature-stable phosphate microwave dielectric ceramic material for LTCC prepared in this example were tested by a vector network analyzer according to the "open cavity" method of the "Test method for microwave complex permittivity of solid dielectric" (GB / T7265.2-1987 standard), and the test results are shown in Table 4.

[0073] Table 4 Microwave dielectric properties of the microwave dielectric ceramic material prepared in Example 3

[0074]

[0075] The XRD pattern of the No. 2 microwave dielectric ceramic material (2 # -3) prepared in this example is shown in Figure 2 Table 5, and it can be seen that the phase composition of the ceramic material is Ba3(PO4)2 and KBaPO4, and there is no other impurity phase.

[0076] The above description is only some specific embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A low-dielectric-constant, temperature-stable phosphate microwave dielectric ceramic material for LTCC, characterized in that, The ceramic material has the molecular formula A. 3-x K 2x (PO4)2, where A=Ba 1-y Sr y , 0.1≤x≤0.5, 0≤y≤1; the phosphate microwave dielectric ceramic material is composed of two phases, A3(PO4)2 and KAPO4.

2. The low dielectric constant temperature-stable phosphate microwave dielectric ceramic material for LTCC according to claim 1, characterized in that, The ceramic material has a dielectric constant of 8.9~12.6, a quality factor of 10186~50213 GHz, and a τ value. f The value is -7.1~7.2 ppm / ℃.

3. The low dielectric constant temperature-stable phosphate microwave dielectric ceramic material for LTCC according to claim 2, characterized in that, The ceramic material has a dielectric constant of 9.9 to 11.5 and a quality factor of 27316 to 50213 GHz.

4. The method for preparing the low dielectric constant temperature-stable phosphate microwave dielectric ceramic material for LTCC as described in claim 1, characterized in that, The specific steps are as follows: 1) Using BaCO3, SrCO3, K2CO3, and NH4H2PO4 as raw materials, according to chemical formula A 3-x K 2x Weigh out the raw materials (PO4)2, where A = Ba 1-y Sr y , 0.1≤x≤0.5, 0≤y≤1, after mixing, the mixture is subjected to ball milling I, drying I, sieving I, and pre-sintering in sequence to obtain ceramic powder base material I; 2) Add H3BO3 to the ceramic powder base material I obtained in step 1), mix and then perform ball milling II, drying II and sieving II in sequence to obtain ceramic powder base material II; then add binder, granulate and press into tablets, obtain green body and sinter to obtain the ceramic material; the mass of added H3BO3 is 1%-5% of the mass of ceramic powder base material I.

5. The preparation method according to claim 4, characterized in that, Step 1) Pre-sintering refers to a temperature of 800~1000℃, a holding time of 6h, and a heating rate of 5℃ / min; Step 2) Sintering refers to heating the green blank to 550℃ at a heating rate of 1-2℃ / min and holding it for 2-4h; then heating it to 850~950℃ at a heating rate of 5℃ / min and holding it for 2-6h, and then cooling it in the furnace.

6. The preparation method according to claim 4, characterized in that, Step 1) The ball milling I refers to dry three-dimensional rotary ball milling with a milling speed of 100~150 rpm and a milling time of 12~36h; Step 2) The ball milling II refers to dry three-dimensional rotary ball milling with a milling speed of 100~150 rpm and a milling time of 12~36h.

7. The preparation method according to claim 4, characterized in that, Step 1) Drying I refers to drying at 80~120℃ for 12~24h; Step 2) Drying II refers to drying at 80~120℃ for 12~24h.

8. The preparation method according to claim 4, characterized in that, The adhesive used in step 2) is an aqueous solution of polyvinyl alcohol.

9. The preparation method according to claim 4, characterized in that, Step 1) Sieving I refers to passing through a 60-mesh sieve, and Step 2) Sieving II refers to passing through an 80-mesh sieve.

10. The preparation method according to claim 8, characterized in that, The polyvinyl alcohol aqueous solution has a mass concentration of 8%, and its addition amount is 10% of the mass of ceramic powder base material II.

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