A ZnO-TiO2 based microwave dielectric ceramic material and its preparation method

Abstract

The present invention belongs to the field of electronic ceramics and their manufacturing, and relates to a ZnO-TiO2-based microwave dielectric ceramic material and a preparation method thereof. The general chemical formula of the ceramic material is: (Zn 0.98‑x Mg x ) 1‑y (Mn 1 / 2Ni 1 / 2 ) y Ti 1+z O3, where x= 0.02~0.05; y =0.01~0.03; z =0.06~0.1; prepared by sol-gel method, its main crystal phase is ZnTiO3, sintering temperature is 825 o C~900 o C. By adopting a sol-gel preparation process, the ZnTiO3 phase can be synthesized at a low temperature range (825-900°C), solving the problem of easy decomposition into Zn2TiO4 and TiO2 phases during high-temperature sintering (>900°C). This invention improves the ceramic-forming properties of microwave dielectric ceramic materials, achieving a high quality factor and near-zero temperature coefficient.

Description

Technical Field

[0001] The invention belongs to the field of electronic ceramics and their manufacture, and is a ZnO-TiO2 based microwave dielectric ceramic material and a preparation method thereof. Background Art

[0002] With the rapid development of mobile communication technology, high-performance microwave dielectric materials have become an indispensable key component in electronic communications, radar systems, and various microwave devices. These materials must possess excellent electromagnetic properties, such as high dielectric constant, high quality factor, and good thermal stability, to meet the growing technological demands.

[0003] Zn-TiO2 is a very important microwave dielectric ceramic material. In the ZnO-TiO2 system, there are three stable phases, namely zinc titanate (Zn2TiO4), zinc metatitanate (ZnTiO3) and zinc titanate (Zn2Ti3O8). Among them, the zinc titanate Zn2Ti3O8 phase structure is a defective distorted spinel structure. Studies have shown that the stable temperature range of the Zn2Ti3O8 phase is relatively narrow (750-800 o C), when the temperature exceeds 800 o C, it will transform into ZnTiO3 phase, and then further transform into Zn2TiO4, so the temperature range of Zn2Ti3O8 phase is relatively low (≤820 o C), the reaction process is difficult to control. Zinc titanate Zn2TiO4 is a high-temperature phase with good stability, but its quality factor in the microwave band is very small and cannot meet the application of microwave and millimeter wave devices. Zinc metatitanate ZnTiO3 belongs to the ABO3 type hexagonal phase ilmenite. In the Zn-TiO2 system, only the zinc metatitanate phase has relatively good microwave dielectric properties: dielectric constant 19, quality factor greater than 30,000 GHz, frequency temperature coefficient -55 ppm / o C. However, the synthesis temperature range of ZnTiO3 ceramics is narrow, and high temperature sintering (>900 o C) It is easy to decompose into Zn2TiO4 phase, which is not conducive to the preparation of microwave dielectric ceramic materials with better dielectric properties. Therefore, the optimal preparation temperature of ZnTiO3 microwave ceramic materials is 820~900 o C.

[0004] Microwave dielectric ceramic materials are generally prepared by solid phase method, but a large number of research reports show that it is difficult to prepare single phase ZnTiO3 ceramic materials using traditional solid phase sintering method, and the resonant frequency temperature coefficient of ZnTiO3 ceramic materials is large, which does not meet the requirements of practical applications (generally, the frequency temperature coefficient is required to be closer to 0 ppm / oC) For microwave dielectric ceramic materials, the smaller the absolute value of the frequency temperature coefficient, the better the material's temperature stability. Numerous studies have focused on Zn-TiO2-based microwave dielectric ceramics, but achieving both high-quality dielectric properties and a near-zero frequency temperature coefficient for the material system remains a pressing challenge.

[0005] Many researchers at home and abroad have made various attempts on this issue in order to obtain pure phase materials and good ceramic properties. Lei Shenhui et al. studied the preparation of pure ZnTiO3 ceramics by pre-firing, cold isostatic pressing, sintering, and then introducing nano ZnO into the ZnO-TiO2 precursor, and then forming and sintering it again. The sintering temperature is above the phase transition temperature, and the preparation process is complicated and difficult to control. Hou Yudong, HT Kim et al. found through the traditional oxide solid phase reaction method that the addition of MgO can stabilize the hexagonal phase of ilmenite in a wide sintering range, but when the sintering temperature exceeds the appropriate temperature (>900 o C), phase decomposition will occur, the density of the ceramic will decrease, and the dielectric properties of the ceramic will be poor. More scholars have synthesized ZnO-TiO2 based powders in the solid phase, and then added glass, low temperature compounds, low temperature oxides, etc. to reduce the ceramic forming temperature in order to obtain better microwave dielectric properties. For example, Wang Jing et al. reduced the solid phase synthesis (Zn 0.9 Mg 0.1 )TiO3 sintering temperature. With the addition of glass, although the sintering temperature reaches below the ZnO-TiO2 phase transition temperature, the quality factor (Qf) of the material decreases significantly. Hu Yuanyun et al. added low melting point oxides and glass to modify ZnO-TiO2 microwave dielectric ceramics. The quality factor and frequency-temperature characteristics of the final prepared material were poor. o C sintering, quality factor 21700, frequency temperature coefficient -13 ppm / o C. Zhang Wu et al. added 5wt.% zinc-boron glass and 15wt.% TiO2 to adjust the frequency temperature coefficient of ceramic materials by compounding Zn and Mg, 925 o C sintering, dielectric constant 27.2, quality factor 49772, frequency temperature coefficient 5.4 ppm / o C, the addition of a large amount of TiO2 leads to a decrease in the quality factor and the temperature coefficient does not reach near zero. Zhao Qishu et al. synthesized (Zn / Mg)TiO3 in different proportions of Zn, Mg, and Ti in the solid phase, and lowered the sintering temperature by adding different low-temperature compounds. They also adjusted the temperature coefficient of ZnO-TiO2-based ceramics by adding CaTiO3, and finally obtained a dielectric constant of 25, a quality factor of 10391, and a dielectric constant temperature coefficient of 6×10 -6 ppm / oC. The addition of large amounts of CaTiO3 deteriorates the ceramic's quality factor. The above studies, using methods such as high-temperature solid-phase synthesis and the addition of low-temperature additives, have failed to produce Zn-TiO2-based microwave dielectric ceramics with high quality factors and good temperature stability due to phase transitions, deteriorated ceramic-forming properties, and increased losses.

[0006] The sol-gel method is an advanced material preparation technology that can precisely control the chemical composition and microstructure. Salavati-Niasari M et al. used Zn(CH3COO)2·2H2O and Ti(OC4H9)4 as raw materials and prepared single-phase ZnTiO3 powder by the sol-gel method. However, they explored the photocatalytic degradation performance of ZnTiO3 and did not study the microwave dielectric properties. Li Junsheng et al. used the hydrothermal-assisted sol-gel method to prepare nano zinc titanate, mainly studying its photocatalytic properties. Yu Lifang, Yu Youhua et al. used tetrabutyl titanate and zinc nitrate hexahydrate as raw materials and prepared ZnTiO3 powder by the sol-gel method. When the Zn:Ti ratio was 1:1 and the synthesis temperature was 800 o C, hexagonal ilmenite ZnTiO3 powder can be produced, but the microwave dielectric properties of ZnTiO3 and how to obtain ceramic materials with high quality factor and good temperature stability have not been studied. Summary of the Invention

[0007] The purpose of the present invention is to: ZnTiO3 ceramics have a narrow synthesis temperature range and high temperature sintering (> 900 o C) is easily decomposed into Zn2TiO4 phase and TiO2 phase, which is not conducive to the preparation of microwave dielectric ceramic materials with better dielectric properties. The present invention proposes a ZnO-TiO2 based microwave dielectric ceramic material and a preparation method thereof, which can meet the application requirements of electronic devices.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A ZnO-TiO2 based microwave dielectric ceramic material, characterized in that the general chemical formula of the ceramic material is: (Zn 0.98-x Mg x ) 1-y (Mn 1 / 2 Ni 1 / 2 ) y Ti 1+z O3, where x = 0.02~0.05; y = 0.01~0.03; z = 0.06~0.1; prepared by sol-gel method, its main crystal phase is ZnTiO3, sintering temperature is 825~900 o C.

[0010] Furthermore, when x = 0.04, y = 0.02 and z = 0.1, at 875 o The dielectric constant of the material at sintering temperature of C is 26.5@10GHz, and the dielectric loss is 1.21×10 -4 @10GHz, Q×f value 77998 GHz, -40~85 o The frequency temperature coefficient is 3.5 ppm / o C.

[0011] Furthermore, the method for preparing the above-mentioned low-temperature sintered microwave dielectric ceramic material comprises the following steps:

[0012] Step 1: Prepare the raw materials of Zn, Mg, Ti, Mn and Ni according to the chemical formula (Zn 0.98-x Mg x ) 1-y (Mn 1 / 2 Ni 1 / 2 ) y Ti 1+z O3 is used for batching, x = 0.02~0.05; y = 0.01~0.03; z = 0.06~0.1;

[0013] Step 2: Add weighed ZnO and MgO powders to deionized water and stir to form a suspension; dilute concentrated nitric acid and deionized water in a volume ratio of 1:1; add the diluted nitric acid to the suspension and stir thoroughly until it is completely dissolved and becomes clear, thereby forming an inorganic solution;

[0014] Step 3: Measure tetrabutyl titanate C 16 H 36 The O4Ti solution was placed in a beaker, and anhydrous ethanol was added at a volume ratio of 1:1. The solution was stirred for 10 to 30 minutes for pre-hydrolysis to form an organic solution.

[0015] Step 4: Slowly add the inorganic solution prepared in step 2 to the organic solution prepared in step 3, stir for 10 to 30 minutes, then add weighed Mn(NO3)2 and Ni(NO3)2, and continue stirring for 1 to 3 hours to form a gel;

[0016] Step 5: Seal the gel prepared in step 4 into a 60 o C oven aging for 4 to 10 hours, then put it in 80 to 100 o C oven drying, and then the dry gel was heated at 500~700 o C pre-fire in air atmosphere for 2 to 5 hours;

[0017] Step 6: The powder pre-sintered in step 5 is ball-milled according to the mass ratio of powder: zirconium ball: deionized water of 1:5:1, and the ball-milling particle size D50 is 0.5~2μm. 80~100 o C drying, adding 10-20wt.% acrylic emulsion binder to the obtained powder for granulation to obtain ceramic raw material;

[0018] Step 7: Press the ceramic raw material obtained in step 6 into a shape and heat it in a muffle furnace at 0.5~2 o C / min to 450℃ and keep it for 2 hours to remove the binder. o C / min to 825~900 o C is kept warm for 1~2 hours and sintered to obtain (Zn 0.98-x Mg x ) 1-y (Mn 1 / 2 Ni 1 / 2 ) y Ti 1+z O3 microwave dielectric ceramic material.

[0019] Furthermore, in step 7, the ceramic raw material obtained in step 6 is pressed into shape 15mm, 7mm high cylinder, in muffle furnace 1 o C / min to 450 o C for 2 hours to remove the glue, o C / min to 825~900 o C is kept warm for 1 hour and sintered to obtain (Zn 0.98-x Mg x ) 1-y (Mn 1 / 2 Ni 1 / 2 ) y Ti 1+z O3 microwave dielectric ceramic material.

[0020] In summary, the present invention provides a modified ZnO-TiO2 based ceramic material, the chemical formula of which is (Zn 0.98- x Mg x ) 1-y (Mn 1 / 2 Ni 1 / 2 ) y Ti 1+z O3, through the sol-gel preparation process, can be prepared in a low temperature range (825~900 o C) synthesize ZnTiO3 phase, solve the problem of high temperature sintering (>900 oC) is easy to decompose into Zn2TiO4 phase and TiO2 phase; it adopts non-stoichiometric chemical ratio, by adjusting the molar content of each doping ion, especially controlling the molar content of Zn to be lower than Ti, on the one hand, suppressing the generation of Zn2TiO4 and Zn2Ti3O8, on the other hand, 2+ This ratio is beneficial to make Mn with smaller ionic radius 2 + 、Ni 2+ Replace Zn 2+ , reduce the generation of oxygen vacancies, enhance the stability of ionic crystals, and improve the order of cations, thereby improving the quality factor and temperature stability of ZnO-TiO2 based microwave dielectric ceramics, and the resonant frequency temperature coefficient is 3.5 ppm / o C. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 XRD diffraction patterns of the corresponding embodiments;

[0022] Figure 2 Corresponding SEM morphology image of Example 9. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] A method for preparing a low-temperature sintered microwave dielectric ceramic material, comprising the following steps:

[0025] Step 1: Prepare the raw materials of Zn, Mg, Ti, Mn and Ni according to the chemical formula (Zn 0.98-x Mg x ) 1-y (Mn 1 / 2 Ni 1 / 2 ) y Ti 1+z O3 ( x = 0.02~0.05; y = 0.01~0.03; z = 0.06~0.1) for accurate calculation and weighing;

[0026] Step 2: Add weighed ZnO and MgO powders to deionized water and stir to form a suspension. Dilute concentrated nitric acid with deionized water at a ratio of 1:1. Slowly add the diluted nitric acid to the suspension and stir thoroughly until it is completely dissolved and clear, forming an inorganic solution.

[0027] Step 3: Accurately measure analytically pure tetrabutyl titanate C 16 H 36Put the O4Ti solution into a beaker, add anhydrous ethanol at a volume ratio of 1:1, and stir for 10-30 minutes for pre-hydrolysis to form an organic solution;

[0028] Step 4: Add the inorganic solution prepared in step 2 to the organic solution prepared in step 3, stir for 10 to 30 minutes, then add weighed Mn(NO3)2 and Ni(NO3)2, and continue stirring for 2 hours to form a gel;

[0029] Step 5: Seal the gel prepared in step 4 into a 60 o C oven aging for 4 to 10 hours, then put it in 80 to 100 o C oven drying, and then the dry gel was heated at 500~700 o C pre-fire in air atmosphere for 2 to 5 hours;

[0030] Step 6: The powder pre-sintered in step 5 is ball-milled according to the mass ratio of powder: zirconium ball: deionized water of 1:5:1, with a ball milling particle size of D50: 0.8μm, and 80~100 o C drying, adding 10-20wt.% acrylic emulsion binder to the obtained powder to make granules;

[0031] Step 7: Press the ceramic raw material obtained in step 6 into shape 15mm, 7mm high cylinder, heated to 450℃ in a muffle furnace at 1℃ / min and kept for 2 hours to remove binder, o C / min to 825~900 o C is kept warm for 1 hour and sintered to obtain (Zn 0.98- x Mg x ) 1-y (Mn 1 / 2 Ni 1 / 2 ) y Ti 1+z O3 microwave dielectric ceramic material.

[0032] The above methods were implemented, as shown in Table 1 and Table 2:

[0033] Table 1: Composition and sintering temperature of Examples 1 to 12

[0034]

[0035] Table 2: Dielectric properties of Examples 1 to 12

[0036]

[0037] From Table 1 and Table 2, we can see that x = 0.04, y = 0.02 andz = 0.06, 0.08, 0.1, sintering temperature is between 825~900 o C, the resonant frequency temperature coefficient τ of the ceramic sample f All values ​​are within ±5 ppm / o C, are very good, and at z = 0.1 and sintering temperature 875 o C (Example 9) (Zn 0.98-x Mg x ) 1-y (Mn 1 / 2 Ni 1 / 2 ) y Ti 1+z O3 ceramics have the best microwave dielectric properties: ε r = 26.5 (@10GHz), tanδ = 1.21×10 -4 (@10GHz), Q×f = 77998 GHz, τ f =3.5 ppm / o C, which is superior to existing technical reports and can be applied to microwave and millimeter wave passive integrated devices.

[0038] Figure 1 The XRD diffraction patterns of Examples 7, 8, and 9 are shown. The main crystalline phases of the ceramic samples in the three different examples are ZnTiO3 (JCPDS #58-0547), Mg 2+ 、Mn 2+ 、Ni 2+ Each doping ion is dissolved into the cation lattice to form a solid solution of ZnTiO3 structure. NiTiO3 has a positive frequency temperature coefficient (115 ppm / o C), can improve the temperature characteristics of ZnTiO3 solid solution. In addition, as z increases, excess Ti 4+ On the one hand, the formation of isomeric phases such as zinc titanate Zn2TiO4 is suppressed. On the other hand, excessive Ti forms TiO2. Since TiO2 has a positive temperature coefficient of 465 ppm / o C. The presence of a small amount of TiO2 can significantly improve the frequency temperature coefficient of ZnO-TiO2 based microwave dielectric ceramic materials.

[0039] Figure 2 The SEM morphology of the cross section of the sample in Example 9 shows that the grains of the ceramic sample have grown sufficiently and the grain boundaries are clearly visible, indicating that the sample was sintered at low temperature (<900 o C) Densification can be achieved, with only some micropores at the grain boundaries.

[0040] In summary, this embodiment adopts the sol-gel method to prepare ZnO-TiO2 based microwave dielectric ceramic materials, and introduces Mg2+ 、Mn 2+ 、Ni 2+ ions, achieving uniform synergistic modification of ZnTiO3 during synthesis, thereby obtaining ZnO-TiO2 based microwave dielectric ceramic materials with excellent microwave dielectric properties and good temperature stability.

[0041] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A ZnO-TiO2 based microwave dielectric ceramic material, characterized in that: The general chemical formula of the ceramic material is: (Zn 0.98- x Mg x ) 1-y (Mn 1 / 2 Ni 1 / 2 ) y Ti 1+z O3, where x = 0.02~0.05; y = 0.01~0.03; z = 0.06~0.1; It is prepared by sol-gel method, the main crystal phase is ZnTiO3, and the sintering temperature is 825 ~900 o C.

2. The ZnO-TiO2 based microwave dielectric ceramic material according to claim 1, characterized in that: when x = 0.04, y = 0.02 and z = 0.1, at 875 o The dielectric constant of the material at sintering temperature of C is 26.5@10GHz, and the dielectric loss is 1.21×10 -4 @10GHz, Q×f value 77998 GHz, -40~85 o The frequency temperature coefficient is 3.5 ppm / o C.

3. A method for preparing a ZnO-TiO2-based microwave dielectric ceramic material, characterized in that: The following steps are involved: Step 1: Prepare the raw materials of Zn, Mg, Ti, Mn and Ni according to the chemical formula (Zn 0.98-x Mg x ) 1-y (Mn 1 / 2 Ni 1 / 2 ) y Ti 1+z O3 is used for batching, x = 0.02~0.05; y = 0.01~0.03; z = 0.06~0.1; Step 2: Add weighed ZnO and MgO powders to deionized water and stir to form a suspension; dilute concentrated nitric acid and deionized water in a volume ratio of 1:1; add the diluted nitric acid to the suspension and stir thoroughly until it is completely dissolved and becomes clear, thereby forming an inorganic solution; Step 3: Measure tetrabutyl titanate C 16 H 36 The O4Ti solution was placed in a beaker, and anhydrous ethanol was added at a volume ratio of 1:

1. The solution was stirred for 10 to 30 minutes for pre-hydrolysis to form an organic solution. Step 4: Add the inorganic solution prepared in step 2 to the organic solution prepared in step 3, stir for 10 to 30 minutes, then add weighed Mn(NO3)2 and Ni(NO3)2, and continue stirring for 1 to 3 hours to form a gel; Step 5: Seal the gel prepared in step 4 into a 60 o C oven aging for 4 to 10 hours, then put it in 80 to 100 o C oven drying, and then the dry gel was heated at 500~700 o C pre-fire in air atmosphere for 2 to 5 hours; Step 6: The powder pre-sintered in step 5 is ball-milled according to the mass ratio of powder: zirconium ball: deionized water of 1:5:1, and the ball-milling particle size D50 is 0.5~2μm. 80~100 o C drying, adding 10-20wt.% acrylic emulsion binder to the obtained powder for granulation to obtain ceramic raw material; Step 7: Press the ceramic raw material obtained in step 6 into a shape and heat it to 450℃ in a muffle furnace at a speed of 0.5~2℃ / min. o C keep warm for 2 hours to remove glue, 2~8 o C / min to 825~900℃ and keep it for 1~2 hours, then sinter it to get (Zn 0.98-x Mg x ) 1-y (Mn 1 / 2Ni 1 / 2 ) y Ti 1+z O3 microwave dielectric ceramic material.

4. The method for preparing a ZnO-TiO2 based microwave dielectric ceramic material according to claim 3, characterized in that: In step 7, the ceramic raw material obtained in step 6 is pressed into shape 15mm, 7mm high cylinder, in muffle furnace 1 o C / min to 450 o C for 2 hours to remove the glue, o C / min to 825~900 o C is kept warm for 1 hour and sintered to obtain (Zn 0.98-x Mg x ) 1-y (Mn 1 / 2 Ni 1 / 2 ) y Ti 1+z O3 microwave dielectric ceramic material.

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