A low-sintering-temperature dual-phase high-entropy silicate-based microwave dielectric material and a preparation method thereof

Abstract

The application discloses a low-sintering-temperature dual-phase high-entropy silicate-based microwave dielectric material, and belongs to the field of microwave electronic ceramic materials and manufacturing thereof. 0.4 Zn 0.4 (Ni 1 / 2 Co 1 / 2 ) 0.8‑x Li 0.4+x ]SiO4, wherein 0<=x<=0.8; the application further discloses a preparation method of the material, which comprises the following steps: weighing, ball milling, drying, calcining, secondary ball milling, drying, granulating, forming, degassing and sintering; the microwave dielectric material provided by the application has low dielectric constant (4.86-6.50) and low sintering temperature (925 DEG C), and has high application prospect in the field of new-generation mobile communication and LTCC low-temperature co-firing.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave electronic ceramic materials, in particular to a dual-phase high-entropy silicate-based microwave material with low sintering temperature and a preparation method thereof. BACKGROUND

[0002] With the rapid development of the new generation of mobile communication, low temperature co-fired ceramic (LTCC) plays an important role in the fields of mobile devices, satellites, telecommunication base stations and transportation systems. At the same time, high-entropy materials have attracted much attention due to their special properties. Such materials are usually formed by the mutual solid solution of multiple components in equal or near-equal proportions, which have different structural characteristics and performance characteristics from traditional materials, and are expected to be widely used in the fields of aerospace, new energy electronic devices, nuclear energy applications, etc.

[0003] Silicates are known for their low ε r and high Qxf values because of their relatively high covalent bonds (Rui Peng, Yuanxun Li, et al. Improved sintering and microwave dielectric properties of Li2CaSiO4 ceramic with magnesium atom substitution. Ceramics International 46 (2020) 8869-8876). Kui Liu et al. (Kui Liu, Huaiwu Zhang, et al. Crystal structure and microwave dielectric properties of (Mg 0.2 Ni 0.2 Zn 0.2 Co 0.2 Mn 0.2 )2SiO4-A novel high-entropy ceramic. Ceramics International 48 (2022) 23307-23313) prepared high-entropy silicates (Mg r Ni f Zn 0.2 Co 0.2 Mn 0.2 )2SiO4 with the best performance of ε 0.2 = 8.02, τ 0.2 = -38.2 ppm / ℃ of olivine type by solid state reaction method. However, its sintering temperature is 1250℃.

[0004] Mg2SiO4 and Zn2SiO4 have ultra-high quality factors and low dielectric constants, 210000 GHz, 6.8 and 240000 GHZ, 6.6, respectively, but their sintering temperatures are relatively high for LTCC applications. Although Li + substituting Mg 2+ for 2+ Zn 0.6-x can reduce the sintering temperature of Mg2SiO4 and Zn2SiO4, the densification temperature of Li2MgSiO4 and Li2ZnSiO4 also reaches 1250℃, which still does not meet the practical application requirements of LTCC (Maofeng Zhong, Hua Su, et al. Crystal structure and microwave dielectric properties of Li2Mg x Co 0.4 Zn 0.4 SiO4 ceramic for LTCC applications. Ceramics International 46 (2020) 13095-13101).

[0005] Adding low-melting oxides or glasses is an effective method to reduce the densification temperature, but the dielectric properties of the composite ceramics will deteriorate to some extent. Therefore, how to reduce the sintering temperature of the ceramic while maintaining the microwave dielectric properties is a problem to be solved. SUMMARY

[0006] The purpose of the present application is to provide a low-sintering-temperature dual-phase high-entropy silicate-based microwave dielectric material to solve the above problems.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0008] The chemical composition is: [Mg 0.4 Zn 0.4 (Ni 1 / 2 Co 1 / 2 ) 0.8-x Li 0.4+x ]SiO4, wherein 0≤x≤0.8.

[0009] In view of the above problems, the inventors propose to replace Mg + in Mg2SiO4 with Li 2+ , Co 2+ , Ni 2+ , and Zn 2+ ions to ultimately obtain a dual-phase high-entropy silicate-based microwave ceramic with cheap raw materials, simple preparation process, and low sintering temperature.

[0010] The preparation method of the above material comprises the following steps:

[0011] (1) According to the formula of [Mg 0.4 Zn 0.4 (Ni 1 / 2 Co 1 / 2 ) 0.8-x Li 0.4+x ]SiO4, wherein 0≤x≤0.8, the raw materials MgO, ZnO, NiCO3, CoCO3, Li2CO3 and SiO2 are weighed, primary ball-milled, and dried to obtain a mixed and dried powder.

[0012] (2) The mixed and dried powder is ground, and a pre-sintered material is obtained through pre-sintering.

[0013] (3) The pre-sintered material is secondary ball-milled, and dried for standby use.

[0014] (4) The secondary ball-milled powder is mixed with a binder solution for granulation and compression molding.

[0015] (5) The sample after compression molding is subjected to degassing treatment to obtain a green body, and then the green body is sintered to obtain the required material.

[0016] As a preferred technical solution, in step (1), the weighed raw materials are placed in a ball mill tank, deionized water is used as the ball milling medium, the mass ratio of the powder to the deionized water is 1:0.8-1.5, the difference between the maximum mass and the minimum mass of the four ball mill tanks is not more than 2g, the ball milling speed is 250-300rpm, and the ball milling time is 4-12h, so that the raw materials are mixed uniformly, and the powder is dried to constant weight for standby use.

[0017] As a preferred technical solution, the specific conditions of the pre-sintering treatment in step (2) are as follows: the pre-sintering temperature is 900-1000℃, the pre-sintering treatment heating rate is 2-10℃ / min, the holding time is 2-6h; the pre-sintering treatment cooling rate is 5℃ / min, and the temperature is cooled to room temperature after cooling to 500℃.

[0018] As a preferred technical solution, the binder solution in step (4) is a PVA solution, the concentration of which is 5-10wt%, and the added mass percentage is 5wt%-20wt%, and the compression molding specific conditions are as follows: the pressure is 10-20MPa, the diameter of the compression molded cylinder is 12mm, and the thickness is 5-7mm.

[0019] In step (3), the secondary ball milling process parameters are consistent with those in step (1).

[0020] As a preferred technical scheme, the specific conditions of the glue removal treatment in step (5) are as follows: the treatment temperature is 400-600 DEG C, the temperature rising rate of the glue removal treatment is 2-5 DEG C / min, and the holding time is 2-6 h.

[0021] As a preferred technical scheme, the specific conditions of the sintering treatment in step (5) are as follows: the sintering temperature is 925 DEG C, the temperature rising rate is 2-5 DEG C / min, the holding time is 2-6 h, the sintering reaction cooling rate is 5 DEG C / min, and the temperature is cooled to room temperature after being cooled to 500 DEG C.

[0022] The application is based on [Mg 0.4 Zn 0.4 (Ni 1 / 2 Co 1 / 2 ) 0.8-x Li 0.4+x ]SiO4 stoichiometric ratio, when Li2CO3, MgO, ZnO, NiCO3, CoCO3 and SiO2 are mixed and reacted according to the corresponding ratio, the main phase of the product is (Mg 2 / 3 Ni 2 / 3Co 2 / 3 )SiO4 and Li2ZnSiO4, and a low-sintering-temperature dual-phase high-entropy silicate microwave dielectric ceramic is generated through a solid-phase reaction method.

[0023] According to the value of x, the generated sample is also different. When x<=0.4, the sample mainly contains (Mg 2 / 3 Ni 2 / 3Co 2 / 3 )SiO4 phase; when x>=0.6, with the increase of the content of Li + , the sample mainly contains Li2ZnSiO4 phase.

[0024] Compared with the prior art, the application has the advantages that the material has a low sintering temperature of 925 DEG C, can be used in LTCC low-temperature co-fired ceramic, and also has a low dielectric constant of 4.86-6.50 and continuous adjustment. Since Li2CO3, NiCO3 and CoCO3 are decomposed into Li2O, NiO and CoO in the sintering process, and Li2O, NiO, CoO and ZnO can reduce the sintering temperature of the sample to a certain extent, the low sintering temperature is possibly realized by the synergistic effect of Li2O, NiO, CoO and ZnO, and it is not necessary to add other low-melting-point oxides or glass. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1X-ray diffraction (XRD) patterns of sintered samples with different x values at 925℃ in Example 1; "PDF#84-1990" "PDF#24-2677" in the figure are the standard card numbers of crystal phase.

[0026] Figure 2 Dielectric constant and quality factor of materials with different x values when sintered at 925℃ in Example 1. DETAILED DESCRIPTION

[0027] The application will be further described below with reference to the accompanying drawings.

[0028] Example 1:

[0029] A low-sintering-temperature dual-phase high-entropy silicate-based microwave dielectric material, and a preparation method thereof, the preparation method comprising the following steps:

[0030] Step 1: raw materials are weighed according to a molar ratio of SiO2:MgO:ZnO:NiCO3:CoCO3:Li2CO3:=5:2:2:(2-2.5x):(2-2.5x):(1+2.5x) (x=0-0.8), a millionth electronic balance is used to weigh the raw materials, and the weighing value is ensured to have an error of no more than 0.0005g from the theoretical calculation value; the weighed raw materials are placed in a ball mill tank, zirconium balls are used as grinding balls, and deionized water is used as a ball milling medium, the ball milling is carried out at a speed of 250rpm for 4h, and after the ball milling is completed, the slurry is placed in a constant-temperature drying box and dried to a constant weight for standby.

[0031] Step 2: the agglomerated mixed powder after drying obtained in step 1 is crushed in a mortar, is placed in a crucible and is compacted, is raised to 100℃ at a temperature raising rate of 2℃ / min, is then raised to 1000℃ at a rate of 10℃ / min and is kept for 4h, is reduced to 500℃ at a rate of 5℃ / min, and is then cooled to room temperature along with the furnace to obtain [Mg 0.4 Zn 0.4 (Ni 1 / 2 Co 1 / 2 ) 0.8-x Li 0.4+x ]SiO4 pre-sintered material, the pre-sintered material is further placed in a ball mill tank for secondary ball milling, the ball milling process is the same as the first ball milling, and after the ball milling is completed, the pre-sintered material is dried to a constant weight for standby.

[0032] Step 3: the agglomerated pre-sintered material after drying obtained in step 2 is crushed in a mortar, 10wt% PVA solution is added as a binder, the granulation material is ground and sieved through 40-mesh and 120-mesh sieves at the same time, and the granulation material in the middle (i.e., the 120-mesh sieve) is uniaxially dry-pressed into a cylindrical green body with a diameter of 12mm and a thickness of 6mm under a pressure of 20MPa.

[0033] Step 4: Put the cylindrical green body sample obtained in step 3 into a high-temperature sintering furnace, and increase the temperature to 100℃ at a rate of 2℃ / min, then increase the temperature to 600℃ at a rate of 10℃ / min and keep for 4h to remove the PVA organic binder, then decrease the temperature to 500℃ at a rate of 5℃ / min and cool to room temperature with the furnace, to obtain the degassed green body sample.

[0034] Step 5: Put the degassed green body sample obtained in step 4 into a high-temperature sintering furnace again, and increase the temperature to 100℃ at a rate of 2℃ / min, then increase the temperature to 925℃ at a rate of 10℃ / min and keep for 4h for sintering, then decrease the temperature to 500℃ at a rate of 5℃ / min and cool to room temperature with the furnace, to obtain the low-sintering-temperature dual-phase high-entropy silicate-based microwave dielectric ceramic.

[0035] The XRD patterns of the materials with different x values are shown in Figure 1 From Figure 1 which it can be seen that the sample contains the characteristic peaks of (Mg 2 / 3 Ni 2 / 3Co 2 / 3 )SiO4 and Li2ZnSiO4.

[0036] The ε r values and Qxf values of the obtained samples corresponding to different x values are shown in Figure 2 From Figure 2 which it can be seen that when x = 0-0.8, ε r = 4.86-6.50, Qxf = 12000-27500 GHz. And when x = 0.2, ε r = 6.50, Qxf = 27500 GHz.

[0037] Example 2

[0038] Compared with example 1, only the sintering temperature of step 5 is changed from 925℃ to 950℃, and the rest is the same as example 1. The ε r values and Qxf values of the obtained sample are as follows: when x = 0-0.8, ε r = 4.82-6.44, Qxf = 15000-28100 GHz.

[0039] Example 3

[0040] Compared with example 1, x = 0.2 is fixed, and the sintering temperature is changed to 900-975℃. The rest is the same as example 1. The ε r values and Qxf values of the obtained sample are as follows: ε r = 4.73-6.50, Qxf = 18100-28100 GHz.

[0041] Example 4

[0042] This embodiment is compared with Example 1, x = 0 is fixed, and the sintering temperature is changed from 900 to 975°C. The rest is the same as Example 1, and the obtained sample has ε r value and Qxf value, ε r = 4.76-5.42, Qxf = 11000-26100 GHz.

[0043] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a low sintering temperature dual-phase high-entropy silicate-based microwave dielectric material having a chemical composition of: [Mg 0.4 Zn 0.4 (Ni 1 / 2 Co 1 / 2 ) 0.8-x Li 0.4+x ]SiO4, wherein, A low sintering temperature two-phase high-entropy silicate-based microwave dielectric material with 0≤x<0.8, characterized in that it comprises the following steps: (1) according to the ratio of [Mg 0.4 Zn 0.4 (Ni 1 / 2 Co 1 / 2 ) 0.8-x Li 0.4+x ]SiO4, the raw materials MgO, ZnO, NiCO3, CoCO3, Li2CO3 and SiO2 are weighed, once ball milled, and the dried powder after mixing is obtained. (2) grinding the mixed and dried powder, and obtaining pre-sintered material after pre-sintering; (3) performing secondary ball milling on the pre-sintered material, drying after ball milling, and reserving; (4) mixing the powder after secondary ball milling with a binder solution, granulating, and compression molding; (5) performing degassing treatment on the compression molded sample to obtain a green body, and then sintering the green body to obtain the required material.

2. The production method according to claim 1, characterized by, The specific conditions of the pre-sintering treatment in step (2) are as follows: the pre-sintering temperature is 900-1000℃, the pre-sintering treatment heating rate is 2-10℃ / min, the holding time is 2-6h; the pre-sintering treatment cooling rate is 5℃ / min, and the temperature is cooled to room temperature after cooling to 500℃.

3. The preparation method according to claim 1, characterized in that, The binder solution in step (4) is a PVA solution with a concentration of 5-10wt%, and the added mass percentage is 5wt%-20wt%; the compression specific conditions are as follows: the pressure is 10-20MPa, the diameter of the compression molded cylinder is 12mm, and the thickness is 5-7mm.

4. The method of claim 1, wherein, The specific conditions of the degassing treatment in step (5) are as follows: The treatment temperature is 400-600℃, the degassing treatment heating rate is 2-5℃ / min, and the holding time is 2-6h.

5. The preparation method according to claim 1, characterized in that, The specific conditions of the sintering treatment in step (5) are as follows: the sintering temperature is 925℃, the heating rate is 2-5℃ / min, and the holding time is 2-6h; after sintering is completed, the cooling rate is 5℃ / min, and the temperature is cooled to room temperature after cooling to 500℃.

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