Preparation method of low dielectric loss high Qxf value lithium titanate-based microwave dielectric ceramic material and product thereof

Abstract

The application discloses a preparation method of low-dielectric-loss high Q × f value lithium titanate-based microwave dielectric ceramic material and a product thereof.The application takes Li2CO3, TiO2, Sc2O3 and Nb2O5 as raw materials, substitutes Ti in Li2TiO3 with (Sc 1 / 2Nb 1 / 2 ) 4+ , forms a lithium titanate-based microwave dielectric ceramic material with a chemical formula of Li2Ti 4+ (Sc 1‑x Nb 1 / 2 ) 1 / 2 x O3, effectively adjusts the phase structure of the microwave dielectric ceramic, optimizes the temperature frequency characteristics and dielectric loss, and obtains excellent comprehensive microwave dielectric performance with moderate dielectric constant, super high Q × f value and near-zero resonance frequency temperature coefficient, so that the lithium titanate-based microwave dielectric ceramic material has great application potential in the fields of next-generation mobile communication and satellite communication.

Description

Technical Field

[0001] This invention relates to the field of microwave dielectric ceramic materials technology, and in particular to a method for preparing lithium titanate-based microwave dielectric ceramic materials and its products. Background Technology

[0002] Microwave dielectric ceramics, as key materials in next-generation communication technologies, effectively support the miniaturization and high performance of high-frequency components due to their excellent dielectric properties and thermal stability. Their applications in 5G base stations, millimeter-wave communications, and satellite systems have significantly improved the operating frequency and quality factor of devices, providing a solid material foundation for the development of communication equipment towards higher frequencies, more compact designs, and lower losses. Specifically, the dielectric constant is approximately 20, and the bulk density is approximately 3.1 g / cm³. 3 Li₂TiO₃ ceramics, with their moderate dielectric constant, achieve an optimal balance between device miniaturization and ensuring low-latency, high-speed signal transmission. However, Li₂TiO₃ ceramics face two major limitations: first, their large temperature coefficient of positive resonant frequency (TCF = +34.3 ppm / ℃) leads to frequency drift and high-frequency instability; second, their low dielectric constant... Q × f The value (~31,430 GHz) cannot meet the demanding application requirements. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low dielectric loss and high dielectric strength. Q × f The preparation method of lithium titanate-based microwave dielectric ceramic material, through (Sc 1 / 2 Nb 1 / 2 ) 4+ Replace Ti 4+ This allows for effective control of the dielectric properties of Li2TiO3-based microwave dielectric ceramics. Another objective of this invention is to provide a method utilizing the aforementioned low dielectric loss and high dielectric strength... Q × f The product obtained by the preparation method of lithium titanate-based microwave dielectric ceramic material.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] This invention provides a low dielectric loss high Q × f A method for preparing lithium titanate-based microwave dielectric ceramic materials, wherein the chemical formula of the lithium titanate-based microwave dielectric ceramic material is Li₂Ti. 1-x (Sc 1 / 2 Nb 1 / 2 ) x O3, where 0 < x ≤0.5; The preparation method includes the following steps:

[0006] (1) According to the chemical formula, Li2CO3, TiO2, Sc2O3 and Nb2O5 are weighed as raw materials and ball-milled with anhydrous ethanol as medium to obtain a mixture;

[0007] (2) After drying the mixture, it is heated to 950-1000℃ at a rate of 3℃ / min for pre-calcination, held for 2-4 hours, and then cooled to 200-300℃ at a rate of 3℃ / min and allowed to cool naturally to room temperature to obtain the pre-calcined material.

[0008] (3) The pre-burned material is subjected to secondary ball milling, secondary drying, granulation and pressing to obtain a green body;

[0009] (4) The blank is subjected to debinding treatment, and then the temperature is raised to 1180~1210℃ at a rate of 3℃ / min for sintering treatment, held for 2~4h, and then cooled to 200~300℃ at a rate of 3℃ / min, and then naturally cooled to room temperature to obtain lithium titanate-based microwave dielectric ceramic material.

[0010] Furthermore, in step (3) of this invention, 5% PVA solution is added to the powder obtained after secondary drying for mixing and granulation to obtain granular powder with a particle size of 0.125-0.25 mm. The pressing pressure is uniaxial pressure of 100-200 MPa, and the holding time is 1-3 min.

[0011] Furthermore, in step (4) of the present invention, the glue removal process involves heating to 450-600°C at a rate of 2°C / min and holding for 4-6 hours.

[0012] Utilizing the above-mentioned low dielectric loss and high Q × f The product obtained by the preparation method of lithium titanate-based microwave dielectric ceramic material is characterized by: the dielectric constant of the lithium titanate-based microwave dielectric ceramic material. ε r The values ​​range from 17.4 to 20.7. Q × f The values ​​range from 50,240 to 122,360 GHz, and the TCF values ​​range from +25.9 to -22.7 ppm / ℃.

[0013] The present invention has the following beneficial effects:

[0014] (1) This invention uses Sc 3+ With Nb 5+ Formation of complex ions (Sc) 1 / 2 Nb 1 / 2 ) 4+ Ti replacing Li2TiO3 4+An ionic approach was employed to successfully induce the transformation of a cationic ordered monoclinic structure to a cationic disordered cubic structure at high temperatures by introducing high-valence ions at the B-site to form a +4 average valence complex. This unique dual-phase coexistence structure is maintained at room temperature and effectively balances the TCF (transformative dielectric flow rate) of the monoclinic and cubic phases, achieving near-zero TCF. Furthermore, this alternative method effectively suppresses lattice defects and, combined with the phase transition effect, significantly reduces dielectric loss and improves dielectric efficiency. Q × f value.

[0015] (2) Li2Ti prepared in this invention 1-x (Sc 1 / 2 Nb 1 / 2 ) x O3 microwave dielectric ceramic, introduced (Sc) 1 / 2 Nb 1 / 2 ) 4+ It can effectively suppress the generation of lattice defects (such as oxygen vacancies) and induce the formation of reconstructed superstructures, namely, the formation of a biphase structure at room temperature where a cationic ordered monoclinic phase and a cationic disordered cubic phase coexist. This synergistic effect significantly reduces dielectric loss and improves... Q × f Value. When the amount of replacement x When = 0.1, Q × f The value was increased to 122,360 GHz, compared to the Li2TiO3 matrix ( Q × f =31,430 GHz) is nearly 3.89 times higher; when the replacement amount x At a TCF of 0.25, near-zero TCF (~ -2.3ppm / °C) was achieved, while maintaining extremely high TCF. Q × f Values ​​(~102,330 GHz). This invention synergistically optimizes the dielectric properties of lithium titanate-based microwave dielectric ceramics, giving them enormous application potential in next-generation mobile communications, satellite communications, and other fields. Attached Figure Description

[0016] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0017] Figure 1 This refers to the TCF value of the lithium titanate-based microwave dielectric ceramic prepared in the embodiments of the present invention;

[0018] Figure 2 The dielectric constant of the lithium titanate-based microwave dielectric ceramic prepared in the embodiments of the present invention;

[0019] Figure 3 The lithium titanate-based microwave dielectric ceramic prepared according to the embodiments of the present invention isQ × f value. Detailed Implementation

[0020] Example 1:

[0021] This embodiment features a low dielectric loss high Q × f The preparation method of lithium titanate-based microwave dielectric ceramic material, the chemical formula of which is Li₂Ti 0.9 (Sc 1 / 2 Nb 1 / 2 ) 0.1 O3; the preparation method and steps are as follows:

[0022] (1) According to the above chemical formula, Li2CO3 (purity of 99.99%), TiO2 (purity of 99.9%), Sc2O3 (purity of 99.99%) and Nb2O5 (purity of 99.5%) were weighed as raw materials and ball-milled with anhydrous ethanol for 4 hours (speed of 380 r / min) to obtain a mixture;

[0023] (2) After the above mixture is dried, it is heated to 950°C at a rate of 3°C / min for pre-calcination treatment, and the holding time is 2h. Then it is cooled to 200°C at a rate of 3°C / min and then naturally cooled to room temperature to obtain the pre-calcined material.

[0024] (3) After the above pre-burned material is subjected to secondary ball milling and secondary drying, 5% PVA solution is added for granulation to obtain granular powder with a particle size of 0.125-0.25 mm. Then, it is pressed into shape under 200 MPa uniaxial pressure to obtain a green body.

[0025] (4) The above-mentioned blank is heated to 550°C at a rate of 2°C / min for debinding treatment and held for 4 hours; then heated to 1200°C at a rate of 3°C / min for sintering treatment and held for 2 hours; then cooled to 200°C at a rate of 3°C / min and allowed to cool naturally to room temperature to obtain lithium titanate-based microwave dielectric ceramic material.

[0026] Example 2:

[0027] This embodiment features a low dielectric loss high Q × f The preparation method of lithium titanate-based microwave dielectric ceramic material differs from that in Example 1 in that:

[0028] The chemical formula of lithium titanate-based microwave dielectric ceramic material is Li₂Ti. 0.85 (Sc 1 / 2 Nb 1 / 2 ) 0.15 O3.

[0029] Example 3:

[0030] This embodiment features a low dielectric loss high Q × f The preparation method of lithium titanate-based microwave dielectric ceramic material differs from that in Example 1 in that:

[0031] The chemical formula of lithium titanate-based microwave dielectric ceramic material is Li₂Ti. 0.80 (Sc 1 / 2 Nb 1 / 2 ) 0.20 O3.

[0032] The preheating temperature in step (2) is 975℃.

[0033] Example 4:

[0034] This embodiment features a low dielectric loss high Q × f The preparation method of lithium titanate-based microwave dielectric ceramic material differs from that in Example 1 in that:

[0035] The chemical formula of lithium titanate-based microwave dielectric ceramic material is Li₂Ti. 0.75 (Sc 1 / 2 Nb 1 / 2 ) 0.25 O3.

[0036] The preheating temperature in step (2) is 975℃.

[0037] Example 5:

[0038] This embodiment features a low dielectric loss high Q × f The preparation method of lithium titanate-based microwave dielectric ceramic material differs from that in Example 1 in that:

[0039] The chemical formula of lithium titanate-based microwave dielectric ceramic material is Li₂Ti. 0.70 (Sc 1 / 2 Nb 1 / 2 ) 0.30 O3.

[0040] The preheating temperature in step (2) is 1000℃.

[0041] Example 6:

[0042] This embodiment features a low dielectric loss high Q × f The preparation method of lithium titanate-based microwave dielectric ceramic material differs from that in Example 1 in that:

[0043] The chemical formula of lithium titanate-based microwave dielectric ceramic material is Li₂Ti.0.60 (Sc 1 / 2 Nb 1 / 2 ) 0.40 O3.

[0044] The preheating temperature in step (2) is 1000℃.

[0045] Example 7:

[0046] This embodiment features a low dielectric loss high Q × f The preparation method of lithium titanate-based microwave dielectric ceramic material differs from that in Example 1 in that:

[0047] The chemical formula of lithium titanate-based microwave dielectric ceramic material is Li₂Ti. 0.50 (Sc 1 / 2 Nb 1 / 2 ) 0.50 O3.

[0048] The preheating temperature in step (2) is 1000℃.

[0049] Performance testing:

[0050] The microwave dielectric properties of the lithium titanate-based microwave dielectric ceramic material prepared in the embodiments of the present invention were tested using the cavity method. The dielectric properties were tested using an Agilent 8720B network analyzer, a metal closed cavity, and a high-low temperature test chamber, with TE... 01δ The resonant mode was tested at room temperature. The sample was a cylinder with a diameter of 10 × 5 mm. The test results are shown in Table 1.

[0051] Table 1 Dielectric properties of lithium titanate-based microwave dielectric ceramic materials in the embodiments of the present invention.

[0052] Dielectric property examples <![CDATA[ ε r ]]> ×(Ghz) TCF (ppm / ℃) Example 1 20.7 122,360 25.9 Example 2 20.2 113,630 19.4 Example 3 19.4 104,930 11.3 Example 4 18.6 102,330 -2.3 Example 5 18.4 81,630 -12.6 Example 6 17.5 68,310 -22.2 Example 7 17.4 50,240 -22.7

[0053] The TCF value of the microwave dielectric ceramic material in this embodiment of the invention is +25.9 to -22.7 ppm / ℃. For example... Figure 1 As shown, with x As the value increases, the TCF value changes from positive to negative. x When the TCF value was 0.25, a near-zero TCF value (-2.3) was obtained, indicating a significant improvement in the TCF value.

[0054] The dielectric constant of the microwave dielectric ceramic material in the embodiments of the present invention ε r The value is 17.4–20.7, indicating that the chemical formula of this invention is Li₂Ti. 1-x (Sc 1 / 2 Nb 1 / 2 ) xO3-based lithium titanate microwave dielectric ceramics belong to the K20 series of microwave dielectric ceramics. For example... Figure 2 As shown, its dielectric constant ε r Follow x The value decreases linearly as it increases.

[0055] Microwave dielectric ceramic materials of the present invention Q × f The value ranges from 50,240 to 122,360 GHz. For example... Figure 3 As shown, in x When the value is 0.10, the maximum value is obtained. Q × f Value (122,360), Q × f The value has been greatly improved; when x When >0.10, Q × f Value follows x The value decreases as it increases.

Claims

1. A low dielectric loss high Q × f The method for preparing lithium titanate-based microwave dielectric ceramic materials is characterized by: The chemical formula of the lithium titanate-based microwave dielectric ceramic material is Li₂Ti. 1-x (Sc 1 / 2 Nb 1 / 2 ) x O3, where 0 < x ≤0.5; The preparation method includes the following steps: (1) According to the chemical formula, Li2CO3, TiO2, Sc2O3 and Nb2O5 are weighed as raw materials and ball-milled with anhydrous ethanol as medium to obtain a mixture; (2) After drying the mixture, it is heated to 950-1000℃ at a rate of 3℃ / min for pre-calcination, held for 2-4 hours, and then cooled to 200-300℃ at a rate of 3℃ / min and allowed to cool naturally to room temperature to obtain the pre-calcined material. (3) The pre-burned material is subjected to secondary ball milling, secondary drying, granulation and pressing to obtain a green body; (4) The blank is subjected to debinding treatment, and then the temperature is raised to 1180~1210℃ at a rate of 3℃ / min for sintering treatment, held for 2~4h, and then cooled to 200~300℃ at a rate of 3℃ / min, and then naturally cooled to room temperature to obtain lithium titanate-based microwave dielectric ceramic material.

2. The low dielectric loss high dielectric material according to claim 1 Q × f The method for preparing lithium titanate-based microwave dielectric ceramic materials is characterized by: In step (3), 5% PVA solution is added to the powder obtained after secondary drying and mixed and granulated to obtain granular powder with a particle size of 0.125 to 0.25 mm.

3. The low dielectric loss high dielectric loss according to claim 1 Q × f The method for preparing lithium titanate-based microwave dielectric ceramic materials is characterized by: In step (3), the pressing pressure is 100-200 MPa uniaxial pressure, and the holding time is 1-3 min.

4. The low dielectric loss high dielectric material according to claim 1 Q × f The method for preparing lithium titanate-based microwave dielectric ceramic materials is characterized by: In step (4), the glue removal process involves heating the temperature to 450-600℃ at a rate of 2℃ / min and holding it at that temperature for 4-6 hours.

5. Utilizing the low dielectric loss and high dielectric strength described in any one of claims 1-4 Q × f The product obtained by the method for preparing lithium titanate-based microwave dielectric ceramic material is characterized by: The dielectric constant of the lithium titanate-based microwave dielectric ceramic material ε r The values ​​range from 17.4 to 20.

7. Q × f The values ​​range from 50,240 to 122,360 GHz, and the TCF values ​​range from +25.9 to -22.7 ppm / ℃.

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