A method for preparing a low-loss temperature-stable lithium titanate-based microwave dielectric ceramic material and the product obtained

Abstract

The present invention discloses a method for preparing a low-loss temperature-stable lithium titanate-based microwave dielectric ceramic material and the product obtained, using Li2CO3, TiO2, Fe2O3, and Nb2O5 as raw materials, and (Fe 1 / 2 Nb 1 / 2 ) 4+ Replace Ti 4+ , forming a chemical formula of Li2Ti 1‑x (Fe 1 / 2 Nb 1 / 2 ) x O3 lithium titanate-based microwave dielectric ceramic materials significantly reduce the oxygen vacancy content caused by electrostatic compensation, thereby reducing dielectric loss and improving the Q value of microwave dielectric ceramics. At the same time, it can change the unit cell parameters to affect the temperature coefficient of dielectric constant to adjust the TCF value, thereby effectively improving the dielectric properties of Li2TiO3-based microwave dielectric ceramics.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave dielectric ceramic materials, and in particular to a preparation method of a lithium titanate-based microwave dielectric ceramic material and a product obtained therefrom. Background Art

[0002] Microwave dielectric ceramics are a type of high-performance dielectric materials designed specifically for microwave frequencies. They are widely used in key components such as microwave resonators, filters, dielectric substrates, and dielectric antennas. These materials stand out for their outstanding properties, including a moderate dielectric constant (usually between 10 and 100), extremely low dielectric loss, and a near-zero resonant frequency temperature coefficient. These properties are crucial to the success of microwave communication technology. With the rapid development of communication technology, the performance requirements for microwave dielectric ceramics are also increasing. They must exhibit higher stability and efficiency at higher frequencies and in more complex application environments to meet the growing demand for future communication technology. As a representative of new electronic functional materials, the widespread application of microwave dielectric ceramics in the field of modern wireless communications has played a key role in promoting the vigorous development of the communications industry. Research and development of materials with an ideal dielectric constant (ε r Microwave dielectric ceramic materials with excellent Qf values ​​and near-zero temperature coefficient of resonant frequency (TCF) have become a hot topic in this research field. The development of these materials will not only promote the advancement of communications technology but also open up new possibilities for the future of the communications industry.

[0003] Li2TiO3 ceramics have a low density (3.44g / cm 3 ), low cost, and good dielectric properties, thus showing great research and application potential. However, the problems faced by Li2TiO3 ceramics during high-temperature sintering mainly include: the volatilization of Li elements leads to an increase in pores inside the material, which significantly increases the non-intrinsic loss and affects the overall performance of the material, and Ti 4+ At high temperature, Ti 3+ The conversion of increases oxygen vacancies, which further leads to an increase in dielectric loss, and the large positive TCF value limits its practical application. Generally speaking, there are two ways to improve the dielectric properties of Li2TiO3-based microwave dielectric ceramics: (1) inhibiting the TiO2-induced dielectric loss by appropriate ion doping. 4+ (2) Add sintering aids to improve the sintering process. However, the existing technology still cannot effectively solve the problem that the dielectric loss of Li2TiO3-based microwave dielectric ceramics is too high and the large forward TCF value cannot meet the practical application. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a low-loss temperature-stable lithium titanate-based microwave dielectric ceramic material. 1 / 2 Nb 1 / 2 ) 4+ Replace Ti 4+ , so as to effectively improve the dielectric properties of Li2TiO3-based microwave dielectric ceramics. Another object of the present invention is to provide a product made by the above-mentioned method for preparing low-loss temperature-stable lithium titanate-based microwave dielectric ceramics.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a method for preparing a low-loss temperature-stable lithium titanate-based microwave dielectric ceramic material, wherein the chemical formula of the lithium titanate-based microwave dielectric ceramic material is Li2Ti 1-x (Fe 1 / 2 Nb 1 / 2 ) x O3, wherein 0≤x≤0.4; the preparation method comprises the following steps:

[0007] (1) According to the chemical formula, Li2CO3, TiO2, Fe2O3, and Nb2O5 are weighed as raw materials, and ball milled with anhydrous ethanol as a medium to obtain a mixture;

[0008] (2) After drying the mixed material, heating it to 900-1000° C. at a rate of 3° C. / min for pre-sintering, and keeping the temperature for 1-3 hours to obtain a pre-sintered material;

[0009] (3) subjecting the pre-sintered material to secondary ball milling, secondary drying, granulation and press molding to obtain a green body;

[0010] (4) The green body is subjected to a binder removal treatment, and then the temperature is raised to 1100-1225° C. at a rate of 3° C. / min for sintering, and the temperature is kept for 1-3 hours to obtain a lithium titanate-based microwave dielectric ceramic material.

[0011] Furthermore, in step (3) of the present invention, a PVA solution is added to the powder obtained after secondary drying, and the mixture is granulated to obtain a granular powder with a particle size of 0.125 to 0.25 mm. The pressing pressure is a uniaxial pressure of 8 to 12 MPa, and the holding time is 1 to 3 minutes.

[0012] Furthermore, in step (4) of the present invention, the binder removal treatment is performed by heating the temperature to 450-600° C. at a rate of 2° C. / min and keeping the temperature for 4-6 hours.

[0013] The product is made by the method for preparing the above-mentioned low-loss temperature-stable lithium titanate-based microwave dielectric ceramic material, the dielectric constant ε of the lithium titanate-based microwave dielectric ceramic material is r The values ​​are 19.3 to 23.9, Q×f value is 31,560 to 65,320 GHz, and TCF value is 28.5 to 1.8 ppm / °C.

[0014] The present invention has the following beneficial effects:

[0015] (1) The present invention uses Nb 5+ with Fe 3+ Formation of complex ions (Fe 1 / 2 Nb 1 / 2 ) 4+ Replace Ti in Li2TiO3 4+ The ion method introduces high-valent ions at the B position to form complex ions with an average valence of +4, which can significantly reduce the oxygen vacancy content caused by electrostatic compensation, thereby reducing dielectric loss and improving the Q value of microwave dielectric ceramics. In addition, this alternative method can also change the unit cell parameters to affect the temperature coefficient of dielectric constant to adjust the TCF value, effectively improving the dielectric properties of Li2TiO3-based microwave dielectric ceramics.

[0016] (2) Li2Ti described in the present invention 1-x (Fe 1 / 2 Nb 1 / 2 ) x O3 microwave dielectric ceramics, when the substitution amount x = 0.05, a small amount of high-valent ions Nb 5+ The introduction of Ti 4+ The reduction of oxygen vacancies reduces the generation of oxygen vacancies, lowers the dielectric loss, and increases the Q×f value to 65320GHz, which is nearly doubled compared to the Li2TiO3 matrix (Q×f=31,430GHz). When the substitution amount x=0.30, (Fe 1 / 2 Nb 1 / 2 ) 4+ Replace Ti 4+ By changing the unit cell parameters, the crystal structure was transformed from a monoclinic structure to a cubic structure, and a Li2Ti with a TCF value close to zero (TCF = 1.8 ppm / ℃) was obtained. 0.7 (Fe 1 / 2 Nb 1 / 2 ) 0.3 O3 microwave dielectric ceramics while maintaining a high Qf value (31,560GHz). BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be described in further detail below with reference to the embodiments and accompanying drawings:

[0018] Figure 1is the dielectric constant of the lithium titanate-based microwave dielectric ceramic prepared in the embodiment of the present invention;

[0019] Figure 2 is the Q×f value of the lithium titanate-based microwave dielectric ceramic prepared in the embodiment of the present invention;

[0020] Figure 3 is the TCF value of the lithium titanate-based microwave dielectric ceramic prepared in the embodiment of the present invention. DETAILED DESCRIPTION

[0021] Example 1:

[0022] This embodiment provides a method for preparing a low-loss temperature-stable lithium titanate-based microwave dielectric ceramic material. The chemical formula of the lithium titanate-based microwave dielectric ceramic material is Li2Ti 0.95 (Fe 1 / 2 Nb 1 / 2 ) 0.05 O3; the preparation method comprises the following steps:

[0023] (1) According to the above chemical formula, Li2CO3 (purity: 99.99%), TiO2 (purity: 99.9%), Fe2O3 (purity: 99%), and Nb2O5 (purity: 99.5%) were weighed as raw materials, and ball milled with anhydrous ethanol for 4 h (rotation speed: 380 r / min) to obtain a mixture;

[0024] (2) After the mixed material is dried, it is pre-fired at 950°C for 2 hours to obtain a pre-fired material;

[0025] (3) After the pre-sintered material is subjected to a secondary ball milling treatment and secondary drying, a 5% PVA solution is added to granulate the material to obtain a granular powder with a particle size of 0.125 to 0.25 mm, which is then pressed under a uniaxial pressure of 10 MPa to obtain a green body;

[0026] (4) The green body was kept at 550° C. for 4 hours for debinding treatment, and then sintered at 1100° C. for 2 hours to obtain a lithium titanate-based microwave dielectric ceramic material.

[0027] Example 2:

[0028] This embodiment provides a method for preparing a low-loss, temperature-stable lithium titanate-based microwave dielectric ceramic material, which differs from the first embodiment in that:

[0029] The chemical formula of lithium titanate-based microwave dielectric ceramic material is Li2Ti 0.90 (Fe 1 / 2 Nb 1 / 2 ) 0.10 O3.

[0030] The sintering temperature of step (4) is 1125° C. and the holding time is 1.5 h.

[0031] Example 3:

[0032] This embodiment provides a method for preparing a low-loss, temperature-stable lithium titanate-based microwave dielectric ceramic material, which differs from the first embodiment in that:

[0033] The chemical formula of lithium titanate-based microwave dielectric ceramic material is Li2Ti 0.80 (Fe 1 / 2 Nb 1 / 2 ) 0.20 O3.

[0034] The pre-firing temperature of step (3) is 900° C. and the holding time is 3 h.

[0035] The sintering temperature in step (4) is 1150°C.

[0036] Example 4:

[0037] This embodiment provides a method for preparing a low-loss, temperature-stable lithium titanate-based microwave dielectric ceramic material, which differs from the first embodiment in that:

[0038] The chemical formula of lithium titanate-based microwave dielectric ceramic material is Li2Ti 0.70 (Fe 1 / 2 Nb 1 / 2 ) 0.30 O3.

[0039] The debinding treatment temperature in step (4) is 500° C. and the holding time is 5 h.

[0040] The sintering temperature of step (4) is 1175°C.

[0041] Performance testing:

[0042] The dielectric properties of the low-loss, temperature-stable lithium titanate-based microwave dielectric ceramic material prepared in accordance with the present invention were tested using an Agilent 8720B network analyzer and a metal closed cavity. The test results are shown in Table 1.

[0043] Table 1 Dielectric properties of microwave dielectric ceramic materials according to embodiments of the present invention

[0044]

[0045] The dielectric constant ε of the microwave dielectric ceramic material according to the embodiment of the present invention r is 19.3 to 23.9, indicating that the chemical formula of the present invention is Li2Ti 1-x (Fe 1 / 2 Nb 1 / 2 ) xO3 lithium titanate matrix microwave dielectric ceramics belong to the K20 series microwave dielectric ceramics. Figure 1 As shown in the figure, when x = 0.05, the maximum dielectric constant (23.9) is obtained; when x > 0.5, ε r It decreases as the value of x increases.

[0046] The Q×f value of the microwave dielectric ceramic material of the embodiment of the present invention is 31,560 to 65,320 GHz. Figure 2 As shown in the figure, when x=0.05, the maximum Q×f value (65,320) is obtained, and the Q×f value is effectively improved; when x>0.05, the Q×f value decreases with the increase of x value.

[0047] The TCF value of the microwave dielectric ceramic material of the embodiment of the present invention is 28.5-1.8 ppm / °C. Figure 3 As shown in FIG, as the x value increases, the TCF value changes from positive to negative. When x = 0.30, a TCF value of nearly zero (1.8) is obtained, and the TCF value is effectively improved.

Claims

1. A method for preparing a low-loss, temperature-stable lithium titanate-based microwave dielectric ceramic material, characterized by: The chemical formula of the lithium titanate-based microwave dielectric ceramic material is Li2Ti 1-x (Fe 1 / 2 Nb 1 / 2 ) x O3, where 0<x≤0.4; The preparation method comprises the following steps: (1) According to the chemical formula, Li2CO3, TiO2, Fe2O3, and Nb2O5 are weighed as raw materials, and ball milled with anhydrous ethanol as a medium to obtain a mixture; (2) After drying the mixed material, heating it to 900-1000° C. at a rate of 3° C. / min for pre-sintering, and keeping the temperature for 1-3 hours to obtain a pre-sintered material; (3) performing secondary ball milling, secondary drying, granulation and press molding on the pre-sintered material to obtain a green body; (4) The green body is subjected to a binder removal treatment, and then the green body is sintered at a temperature of 1100-1225° C. at a rate of 3° C. / min and kept at this temperature for 1-3 hours to obtain a lithium titanate-based microwave dielectric ceramic material.

2. The method for preparing a low-loss, temperature-stable lithium titanate-based microwave dielectric ceramic material according to claim 1, characterized in that: In the step (3), 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 method for preparing the low-loss temperature-stable lithium titanate-based microwave dielectric ceramic material according to claim 1, characterized in that: The pressure for the compression molding in step (3) is a uniaxial pressure of 8 to 12 MPa, and the holding time is 1 to 3 minutes.

4. The method for preparing a low-loss, temperature-stable lithium titanate-based microwave dielectric ceramic material according to claim 1, characterized in that: The debinding treatment in step (4) is to heat the temperature to 450-600° C. at a rate of 2° C. / min and keep the temperature for 4-6 hours.

5. A product produced by the method for producing a low-loss, temperature-stable lithium titanate-based microwave dielectric ceramic material according to any one of claims 1 to 4, characterized in that: The dielectric constant ε of the lithium titanate-based microwave dielectric ceramic material r The values ​​are 19.3 to 23.9, Q×f value is 31,560 to 65,320 GHz, and TCF value is 28.5 to 1.8 ppm / °C.

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