A high-temperature-stable orthotitanate microwave ceramic material and a preparation method thereof

Abstract

The application discloses a high-temperature-stability orthotitanate microwave ceramic material and a preparation method thereof, and belongs to the field of microwave electronic ceramic materials and preparation thereof. 1 / 2 Zn 1 / 2 ) 0.4+x Li 0.4 (Co 1 / 2 Ni 1 / 2 ) 0.4‑x )2TiO 4， Wherein, 0<=x<=0.4, and the preparation method comprises the steps of primary ball milling, pre-sintering, secondary ball milling, granulation, high-temperature sintering and the like, wherein the sintering temperature is 1300-1400 DEG C; the material can reach a resonance frequency temperature coefficient of -27 ppm / DEG C, a dielectric constant of 15-17, and a Qf value of 106000 GHz; the material has a wide application prospect in a new generation of wireless mobile communication and microwave communication; and the material is low in cost, simple in preparation process, easy to operate and easy to industrialize.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microwave electronic ceramic materials and its preparation, in particular to a high-temperature-stability orthotitanate microwave ceramic material and a preparation method thereof. BACKGROUND

[0002] With the innovation of new generation wireless communication network technology, the environment for the use of electronic components is increasingly complex, and higher requirements are put forward for the stability of microwave components. The temperature coefficient of resonant frequency (τ f ), as an important indicator of the temperature stability of microwave dielectric ceramics, the closer the absolute value is to 0, the better the temperature stability of the ceramic. Therefore, the demand for microwave dielectric ceramics with a resonant frequency temperature coefficient tending to zero is increasingly urgent in the field of communication equipment.

[0003] In order to improve the temperature stability of the ceramic, a large number of scholars use positive τ f materials as resonant frequency temperature coefficient compensators. Two-phase composite is a common method for improving the τ f of the ceramic by temperature coefficient compensation. The τ f value of 0.94Mg2TiO4-0.06SrTiO3 composite ceramic is -3.3 ppm / ℃, but the Qf value is 70 900 GHz, and the different crystal structures of Mg2TiO4 and SrTiO3 cause them to coexist as different phases, which may cause changes in the dielectric properties of the composite material.

[0004] Ion substitution is a common method for improving the performance of microwave dielectric ceramics, but most ion substitutions optimize the quality factor of the ceramic. Xu et al. used ion substitution to replace Ca 2+ in the A site with Ce 2+ and replaced Nb 6+ in the B site with W 5+ , which optimized the resonant frequency temperature coefficient. (Ce 0.85 Ca 0.15 )(Nb 0.85 W 0.15 )O4 has ε r = 19.7, Qf = 35,450 GHz, τ f = 0.8 ppm / °C. However, due to the scarcity and high price of Ce and Nb metals, it is difficult to be widely used in engineering production.

[0005] Titanate has been widely concerned due to its superior performance. Mg2TiO4, as a member of the titanate system, has good dielectric properties: ε r=14.51, Qf = 161 570 GHz, Mg2TiO4-based microwave dielectric ceramic devices can reduce the dielectric loss of microwave devices, but they have poor resonant frequency temperature coefficient (τ f = -50 ppm / ℃), which limits its wide application in microwave communication systems. SUMMARY

[0006] One of the purposes of the present application is to provide a high-temperature-stable orthotitanate microwave ceramic material to solve the above problems.

[0007] In order to achieve the above purpose, the technical solution adopted by the present application is as follows: a high-temperature-stable orthotitanate microwave ceramic material, the chemical composition of the material is: [(Mg 1 / 2 Zn 1 / 2 ) 0.4+x Li 0.4 (Co 1 / 2 Ni 1 / 2 ) 0.4-x ]2TiO 4， Wherein, 0≤x≤0.4.

[0008] The τ f of Mg2TiO4 microwave ceramic is about -50 ppm / ℃, the inventors propose a material that is low in cost, simple in preparation process, easy to operate and can greatly optimize the τ f of the material, which mainly adds Zn, Li, Co, Ni and other low-cost metal ions to realize the optimization of τ f through multi-ion coupling adjustment.

[0009] As a preferred technical solution, 0.1≤x≤0.3, in this range, the resonant frequency temperature coefficient of the material is closer.

[0010] The above microwave dielectric ceramic further controls the sintering temperature at 1300-1400 ℃, when x=0.2, the resonant frequency temperature coefficient can reach -27 ppm / ℃, the dielectric constant is between 15-17, and the Qf value can reach 106000 GHz; it has a wide application prospect in the new generation of wireless mobile communication and microwave communication.

[0011] The second purpose of the present application is to provide a preparation method of the above-mentioned high-temperature-stable orthotitanate microwave ceramic material, which comprises the following steps:

[0012] (1) Taking MgO, ZnO, CoCO3, NiCO3, Li2CO3 and TiO2 as raw materials, according to the proportion of each raw material in the chemical composition, the raw materials are weighed and then ball milled once, and then the dried materials are obtained;

[0013] (2) pre-sintering the dried material obtained in step (1) to obtain a pre-sintered material;

[0014] (3) putting the pre-sintered material obtained in step (2) into a ball mill tank for secondary ball milling to obtain a slurry;

[0015] (4) drying the slurry obtained in step (3) to a constant weight, and then granulating and pressing into a sample;

[0016] (5) placing the sample obtained in step (4) in a high-temperature sintering furnace, and raising the temperature to 400-600 ℃ at a rate of 3-6 ℃ / min and maintaining for 2-6 h, and finally cooling to room temperature with the furnace to obtain a green sample after degassing;

[0017] (6) placing the green sample obtained in step (5) in a high-temperature sintering furnace, and raising the temperature to 1300-1400 ℃ at a rate of 3-6 ℃ / min and maintaining for 2-6 h, and finally cooling to room temperature with the furnace to obtain a titanate microwave dielectric material with optimized resonance frequency temperature coefficient.

[0018] As a preferred technical solution, in steps (1) and (3), zirconia balls are used as the grinding balls, and deionized water is used as the ball milling medium.

[0019] As a preferred technical solution, in step (2), the pre-sintering method is as follows: the dried material is put into an alumina crucible and compacted, and the raw material is raised to 1100 ℃ at a rate of 3-6 ℃ / min, and then the material is maintained for 2-6 h, and then cooled to room temperature with the furnace.

[0020] As a preferred technical solution, in step (4), 10 wt% PVA solution is added as a binder during granulation.

[0021] As a preferred technical solution, in step (4), the pressure during tabletting is 20 MPa, and the size of the cylindrical sample pressed is: diameter 12 mm x thickness 4-6 mm.

[0022] As a preferred technical solution, in step (6), the sintering temperature is 1400 ℃. At this temperature, the material has better performance, and its τ f value can reach -28.7 ppm / ℃, ε r = 16.113, and Qf = 106 0000 GHz.

[0023] Compared with the prior art, the material has the advantages that the material of the application regulates the resonance frequency temperature coefficient of the ceramic through multi-element coupling, so that the resonance frequency temperature coefficient reaches -27 ppm / ℃, the dielectric constant is between 15-17, the Qf value can reach 106000 GHz (without significant deterioration), and the material has a wide application prospect in the new generation of wireless mobile communication and microwave communication; and the material has low cost, simple preparation process, easy operation, and is easy to industrialize. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 X-ray diffraction (XRD) pattern of the sample of [(Mg

[0025] Figure 2 Dielectric property diagram of the sample of [(Mg 1 / 2 Zn 1 / 2 ) 0.4+x Li 0.4 (Co 1 / 2 Ni 1 / 2 ) 0.4-x ]2TiO4 wherein x = 0 of example 2 sintered at 1300-1400 ℃.

[0026] Figure 3 Dielectric property diagram of the sample of [(Mg 1 / 2 Zn 1 / 2 ) 0.4+x Li 0.4 (Co 1 / 2 Ni 1 / 2 ) 0.4-x ]2TiO4 wherein x = 0 of example 2 sintered at 1300-1400 ℃.

[0027] Figure 4 Dielectric property diagram of the sample of (Mg 0.25 Zn 0.2 Co 0.25 Ni 0.25 )2TiO4 of example 3 sintered at 1300-1350 ℃. DETAILED DESCRIPTION

[0028] The application will be further described below in combination with examples.

[0029] A high-temperature-stable orthotitanate microwave ceramic material, and a preparation method thereof, the preparation method comprising the following steps:

[0030] Step 1: according to the formula of [(Mg 1 / 2 Zn 1 / 2 ) 0.4+x Li 0.4 (Co 1 / 2Ni 1 / 2 ) 0.4-x ]2TiO4wherein x = 0.0~0.4; the prepared raw materials were placed in a ball mill tank containing zirconium balls, deionized water was used as the ball milling medium, the rotation speed of the ball mill was set to 250 rpm, the ball milling time was set to 4 h, and after the ball milling was completed, the slurry was placed in a constant temperature drying oven and dried to constant weight for standby use;

[0031] Step 2: The agglomerated powder after drying in step 1 was separately crushed in a mortar, and was placed in a crucible and compacted, and was first raised to 100 ℃ at a temperature raising rate of 5 ℃ / min, and then was pre-fired at 1100 ℃ at a temperature raising rate of 10 ℃ / min; then the material was divided and was kept for 4 h, and then was reduced to 500 ℃ at a temperature reducing rate of 5 ℃ / min, and was cooled to room temperature with the furnace, to obtain a pre-fired material, which was placed in a ball mill tank for secondary ball milling mixing;

[0032] Step 3: The powder obtained in step 2 was added into a 10 wt% PVA solution as a binder, granulation was performed, and uniaxial dry pressing was performed at 20 MPa to form a cylinder with a diameter of 12 mm and a thickness of 6 mm;

[0033] Step 4: The green body sample obtained in step 3 was placed in a high-temperature sintering furnace, was raised to 100 ℃ at a temperature raising rate of 5 ℃ / min, was then raised to 600 ℃ at a temperature raising rate of 10 ℃ / min and was kept for 4 h, and finally was reduced to 500 ℃ at a temperature reducing rate of 5 ℃ / min and was cooled to room temperature with the furnace, to obtain a green body sample after degassing;

[0034] Step 5: The green body sample after degassing in step 4 was again placed in a high-temperature sintering furnace, was raised to 100 ℃ at a temperature raising rate of 5 ℃ / min, was then raised to 1000 ℃ at a temperature raising rate of 10 ℃ / min, was sintered at 1400 ℃ at a temperature raising rate of 5 ℃ / min and was kept for 4 h, and finally was reduced to 500 ℃ at a temperature reducing rate of 5 ℃ / min and was cooled to room temperature with the furnace, to obtain a τ f Significant improvement of titanate microwave dielectric materials;

[0035] Figure 1 The XRD pattern of the sample sintered at 1400 ℃ for the material with different x values in this embodiment, from Figure 1 It can be seen from the XRD pattern that the sample is M2TiO4(M is Mg, Zn, Co, Ni and Li) phase and NiO phase.

[0036] [(Mg 1 / 2 Zn 1 / 2 ) 0.4+x Li 0.4 (Co 1 / 2 Ni 1 / 2 ) 0.4-xThe microwave dielectric properties of the 2TiO4 are shown in Table 1. Figure 2 As can be seen from Table 1, with the increase of x, τf Figure 2 increases first and then decreases, τf f = -27~ -44 ppm / ℃, when x = 0.3, τf f = -28.7 ppm / ℃, Qf = 106 000 GHz, εr = 16.13, and when x = 0.2, τf f = -27 ppm / ℃. r f

[0037] Example 2:

[0038] A positive titanate microwave ceramic material with high temperature stability, the preparation method comprising the following steps:

[0039] Step 1: The raw materials are weighed and configured according to the ratio of [(Mg 1 / 2 Zn 1 / 2 ) 0.4+x Li 0.4 (Co 1 / 2 Ni 1 / 2 ) 0.4-x ]2TiO4; the prepared raw materials are respectively placed in a ball mill tank containing zirconium balls, deionized water is used as the ball milling medium, the rotation speed of the ball mill is set to 250 rpm, the ball milling time is set to 4 h, and after the ball milling is completed, the slurry is placed in a constant temperature drying box and dried to constant weight for standby.

[0040] Step 2: The agglomerated powder after drying in step 1 is respectively crushed in a mortar, and is placed in a crucible and compacted, first raised to 100 ℃ at a temperature rising rate of 5 ℃ / min, and then pre-fired at a temperature rising rate of 10 ℃ / min to 1100 ℃; then the material is divided and kept for 4 h, then reduced to 500 ℃ at a temperature rising rate of 5 ℃ / min, and then cooled to room temperature with the furnace, to obtain a pre-fired material, which is placed in a ball mill tank for secondary ball milling;

[0041] Step 3: The powder obtained in step 2 is added to a 10 wt% PVA solution as a binder, granulated, and uniaxially dry-pressed at 20 MPa into a cylinder with a diameter of 12 mm and a thickness of 6 mm;

[0042] Step 4: The green sample obtained in step 3 is placed in a high-temperature sintering furnace, raised to 100 ℃ at a temperature rising rate of 5 ℃ / min, then raised to 600 ℃ at a temperature rising rate of 10 ℃ / min and kept for 4 h, and finally reduced to 500 ℃ at a temperature rising rate of 5 ℃ / min and then cooled to room temperature with the furnace, to obtain a green sample after degassing;

[0043] ​​Step 5: Place the green sample after debinding in Step 4 back into the high-temperature sintering furnace. Increase the temperature to 100℃ at a rate of 5℃ / min, then to 1000℃ at a rate of 10℃ / min. Sinter one sample at 1300℃, and sinter the other two samples at 1350℃ and 1400℃ respectively at rates of 5℃ / min, holding each at these temperatures for 4 hours. After holding, reduce the temperature to 500℃ at a rate of 5℃ / min, then cool it to room temperature in the furnace to obtain τ. f Improve titanate microwave dielectric materials.

[0044] [(Mg) at different sintering temperatures 1 / 2 Zn 1 / 2 ) 0.4+x Li 0.4 (Co 1 / 2 Ni 1 / 2 ) 0.4-x The microwave dielectric properties of 2TiO4 (x = 0.3) are as follows: Figure 3 As shown. From Figure 3 It can be seen from this that when the sintering temperature is 1300 ℃~1400 ℃, τ f Between -40 ppm / ℃ and -27 ppm / ℃, Qf is between 2500 GHz and 106000 GHz, ε r Between 16.13 and 17.02, when the sintering temperature is 1400 ℃, τ f = -28.7 ppm / ℃, Qf = 106 000 GHz, ε r = 16.13.

[0045] Example 3:

[0046] A microwave ceramic material with high temperature stability of orthotitanate is prepared by the following steps:

[0047] Step 1: According to (Mg 0.25 Zn 0.2 Co 0.25 Ni 0.25 Weigh and prepare the raw materials according to the ratio of 2TiO4; place the prepared raw materials into a ball mill jar containing zirconium balls, use deionized water as the ball milling medium, set the ball mill speed to 250 rpm, and set the ball milling time to 4 h. After the ball milling is completed, place the slurry in a constant temperature drying oven and dry it to constant weight for later use.

[0048] Step 2: Crush the agglomerated powder from Step 1 in a mortar, compact it in a crucible, raise the temperature to 100 ℃ at a rate of 5 ℃ / min, and then raise it to 1100 ℃ at a rate of 10 ℃ / min for pre-firing; then keep the material at the preheated temperature for 4 h, and then lower it to 500 ℃ at a rate of 5 ℃ / min and cool it to room temperature in the furnace to obtain the pre-fired material, and put it into a ball mill jar for secondary ball milling and mixing;

[0049] Step 3: Add 10 wt% PVA solution to the powder obtained in Step 2 as a binder, granulate, and dry press it into a cylinder of 12 mm (diameter) × 6 mm (thickness) under uniaxial pressure at 20 MPa;

[0050] Step 4: Place the green sample obtained in Step 3 into a high-temperature sintering furnace, raise the temperature to 100℃ at a heating rate of 5℃ / min, raise the temperature to 600℃ at a heating rate of 10℃ / min and hold for 4 hours, and finally lower the temperature to 500℃ at a heating rate of 5℃ / min and cool it to room temperature with the furnace to obtain the green sample after debinding.

[0051] Step 5: Place the green sample after debinding in Step 4 back into the high-temperature sintering furnace, raise the temperature to 100 ℃ at a rate of 5 ℃ / min, then raise it to 1000 ℃ at a rate of 10 ℃ / min. Sinter the two pieces at 1300 ℃ and 1350 ℃ respectively at a rate of 5 ℃ / min, and hold for 4 h. After holding, lower the temperature to 500 ℃ at a rate of 5 ℃ / min and then cool it to room temperature with the furnace to obtain the titanate microwave dielectric material.

[0052] (Mg) at different sintering temperatures 0.25 Zn 0.2 Co 0.25 Ni 0.25 The microwave dielectric properties of 2TiO4 are as follows: Figure 4 As shown. From Figure 4 As can be seen from this, when the sintering temperature is 1300 ℃, τ f -46 ppm / ℃, Qf is 50800 GH, ε r It is 16.6. At a sintering temperature of 1350℃, τ f -41 ppm / ℃, Qf is 45800 GH, ε r It is 17.1.

[0053] This embodiment also demonstrates that the addition of Li ions plays a crucial role in improving the material's performance.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high temperature stable orthotitanate microwave ceramic material, characterized in that, The chemical composition of the material is: [(Mg 1 / 2 Zn 1 / 2 ) 0.4+x Li 0.4 (Co 1 / 2 Ni 1 / 2 ) 0.4-x ]2TiO4, wherein 0.2≤x≤0.3, and the preparation method comprises the following steps: (1) Taking MgO, ZnO, CoCO3, NiCO3, Li2CO3 and TiO2 as raw materials, the raw materials are weighed according to the proportion of each raw material in the chemical composition, then once ball milling is carried out, and the dried material is obtained after drying; (2) The dried material obtained in step (1) is pre-fired to obtain a pre-fired material; (3) The pre-fired material obtained in step (2) is put into a ball mill tank for secondary ball milling to obtain a slurry; (4) The slurry obtained in step (3) is dried to constant weight, then granulated, and pressed into a sample; (5) The sample obtained in step (4) is placed in a high-temperature sintering furnace, and the temperature is raised to 400-600℃ at a rate of 3-6 ℃ / min and kept for 2-6 h, and finally cooled to room temperature with the furnace, to obtain a green sample after degassing; (6) The green sample obtained in step (5) is placed in a high-temperature sintering furnace, and the temperature is raised to 1400℃ at a rate of 3-6 ℃ / min and kept for 2-6 h, and finally cooled to room temperature with the furnace, to obtain a titanate microwave dielectric material with optimized resonant frequency temperature coefficient.

2. The high temperature stable orthotitanate microwave ceramic material according to claim 1, characterized in that, In steps (1) and (3), zirconia balls are used as grinding balls, and deionized water is used as the ball milling medium.

3. The high temperature stable orthotitanate microwave ceramic material according to claim 1, characterized in that, In step (2), the pre-firing method is as follows: the dried material is placed in an alumina crucible and compacted, the temperature is raised to 1100℃ at a rate of 3-6 ℃ / min, then the material is kept for 2-6 h, and then cooled to room temperature with the furnace.

4. The high temperature stable orthotitanate microwave ceramic material according to claim 1, characterized in that, In step (4), 10 wt% PVA solution is added as a binder during granulation.

5. The high temperature stable orthotitanate microwave ceramic material according to claim 1, wherein, In step (4), the pressure during pressing is 20 MPa, and the size of the cylindrical sample pressed is: diameter 12 mm x thickness 4-6 mm.

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