Microwave dielectric ceramic with temperature stability in wide temperature range, preparation method and application thereof

Abstract

The application belongs to the technical field of ceramic materials, and provides a microwave dielectric ceramic with temperature stability in a wide temperature range, a preparation method and application thereof.The chemical formula of the microwave dielectric ceramic is as follows: (1-x-y)Mg 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 ; wherein x = 0.13-0.16, y = 0.04-0.1, 0.75 <= (1-x-y) <= 0.80, the microwave dielectric ceramic has a dielectric constant (K) = 21+ / -1, a quality factor (Qf) > 70000, and a resonance frequency temperature coefficient (τf) less than + / -4ppm / ℃ in the range of -40-140℃, and has not only a high quality factor, but also a wide temperature stability, can withstand a large temperature difference, and can be well applied to the field of microwave communication.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, and more specifically, to a microwave dielectric ceramic with temperature stability over a wide temperature range, its preparation method, and its application. Background Technology

[0002] As microwave communication technology develops towards higher frequencies (millimeter waves), high quality factor (Qf) requirements are placed on microwave components such as dielectric ceramic resonators and filters used in this field (Qf is required to be greater than 50,000 at the resonant frequency). At the same time, in order to meet the application needs in different climatic environments, excellent temperature stability is required over a wide temperature range (-40-140℃) (near-zero temperature coefficient of resonant frequency τf < ±4ppm / ℃).

[0003] MgTiO3-CaTiO3 (MCT) materials, which utilize CaTiO3 with a positive resonant frequency temperature coefficient as a temperature supplement, have become the preferred material for microwave communication technology due to their high quality factor and low cost. However, the strong nonlinearity of the resonant frequency temperature coefficient of CaTiO3 over a wide temperature range (-40-140℃), i.e., its strong temperature dependence, leads to a typical high-low temperature "seesaw" phenomenon in the resonant frequency temperature coefficient of MCT materials. That is, when the resonant frequency at high temperatures (25-140℃) is adjusted to near zero, the resonant frequency temperature coefficient at low temperatures (-40-25℃) increases significantly (τf>10ppm / ℃); conversely, if the resonant frequency temperature coefficient at low temperatures is adjusted to near zero, the resonant frequency temperature coefficient at high temperatures will exceed the application requirements.

[0004] Therefore, there is an urgent need to develop a microwave dielectric ceramic that not only has a high quality factor, but also maintains a stable temperature coefficient of resonant frequency over a wide temperature range of -40 to 140°C. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a microwave dielectric ceramic with wide temperature stability over a wide temperature range, its preparation method, and its applications. The microwave dielectric ceramic provided by this invention has a resonant frequency temperature coefficient of less than ±4ppm / ℃ over a wide temperature range of -40-140℃, exhibiting not only a high quality factor but also excellent temperature stability.

[0006] A first aspect of the present invention provides a microwave dielectric ceramic that is temperature stable over a wide temperature range.

[0007] Specifically, a microwave dielectric ceramic that is temperature stable over a wide temperature range, the chemical formula of which is shown below:

[0008] (1-xy)Mg 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 ;

[0009] Where x = 0.13 - 0.16, y = 0.04 - 0.1, and 0.75 ≤ (1 - xy) ≤ 0.80.

[0010] This invention relates to CaTiO3 in Ca 2+ Location introduction La 3+ This reduces the nonlinearity of the temperature coefficient of the resonant frequency of CaTiO3, thus lowering its temperature dependence. Furthermore, to improve its quality factor, the matrix material MgTiO3 was structurally modified using nonstoichiometry to form a Rulldesden-Popper layered perovskite structure. Additionally, a nonstoichiometric Zn2SiO4-based material with an ultra-high quality factor was introduced. 1.8 SiO 3.8 Using a material (quality factor of approximately 200,000) as an auxiliary agent, the sintering temperature and dielectric properties were adjusted; ultimately, a microwave dielectric ceramic with a wide temperature stability and high quality factor was obtained, characterized by a dielectric constant (K) of 21 ± 1, a quality factor (Qf) > 70,000, and a resonant frequency temperature coefficient (τf) of less than ±4 ppm / ℃ in the range of -40 to 140℃.

[0011] A second aspect of the present invention provides a method for preparing microwave dielectric ceramics that are temperature-stable over a wide temperature range.

[0012] A method for preparing a temperature-stable microwave dielectric ceramic over a wide temperature range includes the following steps:

[0013] (1) Mg 1.2 TiO 3.2 Ca 0.61 La 0.26 TiO3 and Zn 1.8 SiO 3.8 Samples were taken and mixed according to the chemical formula of the base material to obtain the first mixture; the chemical formula of the base material is (1-xy)Mg. 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 Where x = 0.13 - 0.16, y = 0.04 - 0.1, and 0.75 ≤ (1 - xy) ≤ 0.80;

[0014] (2) The first mixture and the sintering aid are mixed to obtain the second mixture;

[0015] (3) Mix the second mixture with the binder, then granulate it, and then press it into shape to obtain a ceramic blank;

[0016] (4) The ceramic blank is debonded and then sintered to obtain the microwave dielectric ceramic.

[0017] Preferably, in step (2), when the first mixture is 100 parts by weight, the amount of the sintering aid is 0.3-1.5 parts.

[0018] Preferably, in step (2), the sintering aid includes Al2O3 and / or SiO2.

[0019] More preferably, in step (2), the sintering aid comprises 0.1-0.5 parts Al2O3 and 0.2-1.0 parts SiO2 by weight.

[0020] Preferably, in step (3), the adhesive is polyvinyl alcohol (PVA).

[0021] Preferably, in step (1), MgO and TiO2 are used as raw materials, and Mg is added according to the ratio of Mg to TiO2. 1.2 TiO 3.2 Samples were taken according to the specified ratio, mixed evenly, and then subjected to a first calcination to obtain Mg. 1.2 TiO 3.2 .

[0022] Preferably, the temperature of the first calcination is 1100-1200℃, and / or the time of the first calcination is 3-7h.

[0023] Preferably, in step (1), CaCO3, La2O3 and TiO2 are used as raw materials, according to Ca 0.61 La 0.26 TiO3 samples were taken according to the specified ratio, mixed evenly, and then subjected to a second calcination to obtain Ca. 0.61 La 0.26 TiO3.

[0024] Preferably, the second calcination temperature is 1150-1200℃, and / or the second calcination time is 2-6h.

[0025] Preferably, in step (1), ZnO and SiO2 are used as raw materials, and Zn... 1.8 SiO 3.8 Samples were taken according to the specified ratio, mixed evenly, and then subjected to a third calcination to obtain Zn. 1.8 SiO 3.8 .

[0026] Preferably, the temperature of the third calcination is 1150-1200℃, and / or the time of the third calcination is 2-6 hours.

[0027] Preferably, in step (1), the mixing method is ball milling, and / or the mixing time is 12-24 hours.

[0028] Preferably, in step (3), the pressure used for pressing is 160-300 MPa.

[0029] Preferably, in step (4), the sintering temperature is 1300-1340℃, and / or the sintering time is 3-8h.

[0030] A third aspect of the present invention provides an application of microwave dielectric ceramics that are temperature-stable over a wide temperature range.

[0031] Application of a temperature-stable microwave dielectric ceramic over a wide temperature range in the fabrication of microwave communication equipment.

[0032] Preferably, the microwave communication device is a dielectric filter or a dielectric resonator.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] The chemical formula of the microwave dielectric ceramic provided by this invention is as follows: (1-xy)Mg 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 Where x = 0.13-0.16, y = 0.04-0.1, 0.75 ≤ (1-xy) ≤ 0.80, and the present invention relates to CaTiO3 in Ca 2+ Location introduction La 3+ Furthermore, the matrix material MgTiO3 was structurally modified using non-stoichiometry to form a Rulldesden-Popper layered perovskite structure; in addition, a non-stoichiometric Zn2SiO4-based material with an ultra-high quality factor was introduced (Zn 1.8 SiO 3.8 The material (quality factor of approximately 200,000) is used as an auxiliary agent to adjust its sintering temperature and dielectric properties; ultimately, the dielectric constant (K) of the microwave dielectric ceramic of this invention is 21 ± 1, the quality factor (Qf) is > 70,000, and the temperature coefficient of resonant frequency (τf) is less than ± 4 ppm / ℃ in the range of -40 to 140℃. It not only has a high quality factor, but also has wide temperature stability and can withstand large temperature differences, so it can be well applied in the field of microwave communication. Detailed Implementation

[0035] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0036] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0037] Example 1

[0038] A microwave dielectric ceramic, the chemical formula of which is shown below:

[0039] (1-xy)Mg 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 Where x = 0.13, y = 0.1, and 1 - xy = 0.77.

[0040] A method for preparing microwave dielectric ceramics includes the following steps:

[0041] (1) Using MgO and TiO2 as raw materials, according to Mg 1.2 TiO 3.2 The chemical formula was used to measure the raw materials, which were then mixed, ball-milled, dried, and calcined at 1150℃ for 5 hours to obtain the synthetic material Mg. 1.2 TiO 3.2 Using CaCO3, La2O3, and TiO2 as raw materials, according to Ca... 0.61 La 0.26 TiO3 was prepared according to the chemical formula, mixed and ball-milled, dried, and then calcined at 1200℃ for 3 hours to obtain the synthesized material Ca. 0.61 La 0.26 TiO3; using ZnO and SiO2 as raw materials, according to Zn 1.8 SiO 3.8 The materials were prepared according to the chemical formula, mixed and ball-milled, dried, and then calcined at 1200℃ for 2 hours to obtain the synthetic Zn. 1.8 SiO 3.8 ;

[0042] (2) Using the three synthetic materials obtained in (1) above as raw materials, according to (1-xy)Mg 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8(Where x = 0.13, y = 0.1, 1 - xy = 0.77) The materials are mixed according to the ratio to obtain a mixture. Taking the mass of the mixture as 1, 0.2 wt% SiO2 and 0.5 wt% Al2O3 are added to the mixture as sintering aids and mixed to obtain ceramic powder. The ceramic powder is ball-milled and polyvinyl alcohol (PVA mass accounts for 1.5 wt% of the ceramic powder mass) is added as a binder. After granulation, granulated material is obtained.

[0043] (3) The granulated material obtained in (2) is dry-pressed at a pressure of 200MPa to obtain a ceramic blank;

[0044] (4) After removing the binder from the ceramic blank in (3), it is sintered at 1300℃ for 4 hours to obtain microwave dielectric ceramic.

[0045] Example 2

[0046] A microwave dielectric ceramic, the chemical formula of which is shown below:

[0047] (1-xy)Mg 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 Where x = 0.145, y = 0.075, and 1 - xy = 0.78.

[0048] A method for preparing microwave dielectric ceramics includes the following steps:

[0049] (1) Using MgO and TiO2 as raw materials, according to Mg 1.2 TiO 3.2 The chemical formula was used to measure the raw materials, which were then mixed, ball-milled, dried, and calcined at 1175℃ for 4 hours to obtain the synthetic material Mg. 1.2 TiO 3.2 Using CaCO3, La2O3, and TiO2 as raw materials, according to Ca... 0.61 La 0.26 TiO3 was prepared according to the chemical formula, mixed and ball-milled, dried, and then calcined at 1175℃ for 5 hours to obtain the synthesized material Ca. 0.61 La 0.26 TiO3; using ZnO and SiO2 as raw materials, according to Zn 1.8 SiO 3.8 The materials were prepared according to the chemical formula, mixed and ball-milled, dried, and then calcined at 1175℃ for 4 hours to obtain the synthetic Zn. 1.8 SiO 3.8 ;

[0050] (2) The three synthetic materials obtained in (1) above are combined according to (1-xy)Mg1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 (Where x = 0.145, y = 0.075, 1-xy = 0.78) The chemical formula is used to measure and mix the materials to obtain a mixture. Taking the mass of this mixture as 1, 0.6 wt% SiO2 and 0.3 wt% Al2O3 are added to the mixture to obtain ceramic powder. The ceramic powder is ball-milled and polyvinyl alcohol (PVA) (accounting for 1.5 wt% of the ceramic powder mass) is added as a binder. After granulation, granulated material is obtained.

[0051] (3) The granulated material obtained in (2) is dry-pressed at a pressure of 260 MPa to obtain a ceramic green body;

[0052] (4) After removing the binder from the ceramic blank in (3), it is sintered at 1320℃ for 3 hours to obtain microwave dielectric ceramic.

[0053] Example 3

[0054] A microwave dielectric ceramic, the chemical formula of which is shown below:

[0055] (1-xy)Mg 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 Where x = 0.16, y = 0.05, and 1 - xy = 0.79.

[0056] A method for preparing microwave dielectric ceramics includes the following steps:

[0057] (1) Using MgO and TiO2 as raw materials, according to Mg 1.2 TiO 3.2 The chemical formula was used to measure the raw materials, which were then mixed, ball-milled, dried, and calcined at 1150℃ for 7 hours to obtain the synthetic material Mg. 1.2 TiO 3.2 Using CaCO3, La2O3, and TiO2 as raw materials, according to Ca... 0.61 La 0.26 TiO3 was prepared according to the chemical formula, mixed and ball-milled, dried, and then calcined at 1150℃ for 6 hours to obtain the synthesized material Ca. 0.61 La 0.26 TiO3; using ZnO and SiO2 as raw materials, according to Zn 1.8 SiO 3.8 The chemical formula was used to measure the raw materials, which were then mixed, ball-milled, dried, and calcined at 1150℃ for 6 hours to obtain the synthetic Zn.1.8 SiO 3.8 ;

[0058] (2) The three synthetic materials obtained in (1) above are combined according to (1-xy)Mg 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 (Where x = 0.16, y = 0.05, 1-xy = 0.7) The chemical formula is used to mix the materials to obtain a mixture. Taking the mass of the mixture as 1, 0.6 wt% SiO2 and 0.3 wt% Al2O3 are added to the mixture to obtain ceramic powder. The ceramic powder is ball-milled and mixed, and polyvinyl alcohol (PVA) (accounting for 1.5 wt% of the ceramic powder mass) is added as a binder. After granulation, granulated material is obtained.

[0059] (3) The granulated material obtained in (2) is dry-pressed at a pressure of 300 MPa to obtain a ceramic blank;

[0060] (4) After removing the glue from the ceramic blank in (3), it is sintered at 1340℃ for 3 hours to obtain microwave dielectric ceramic.

[0061] Comparative Example 1

[0062] A microwave dielectric ceramic differs from Example 1 in that it has different component contents, as shown in Table 1.

[0063] Comparative Example 2

[0064] A microwave dielectric ceramic differs from Example 1 in that it has different component contents, as shown in Table 1.

[0065] Comparative Example 3

[0066] A microwave dielectric ceramic with the structural formula 0.77Mg 1.2 TiO 3.2 -0.13Ca 0.61 Sm 0.26 TiO3-0.1Zn 1.8 SiO 3.8 .

[0067] Comparative Example 4

[0068] A microwave dielectric ceramic with the structural formula 0.77Mg 1.2 TiO 3.2 -0.13Ca 0.7 La 0.2 TiO3-0.1Zn 1.8 SiO 3.8 .

[0069] The preparation methods of microwave dielectric ceramics provided in Comparative Examples 1-4 above are the same as those in Example 1, except that in Comparative Example 3, La2O3 is replaced with Sm2O3.

[0070] Comparative Example 5

[0071] A microwave dielectric ceramic with the structural formula 0.95MgTiO3-0.05CaTiO3 is prepared as follows:

[0072] MgO, CaCO3, and TiO2 were selected as raw materials. The MgTiO3 and CaTiO3 were stoichiometrically formulated according to the above structural formulas, mixed by ball milling, and then calcined at 1100-1200℃ for 2-6 hours to obtain a composite material of MgTiO3 and CaTiO3. Then, the composite material was ball-milled and mixed again according to a molar ratio of MgTiO3 / CaTiO3 = 0.95 / 0.05. Polyethylene (PVA) was added as a binder, and the mixture was pressed into shape. After debinding, it was sintered at 1330-1350℃ for 3-5 hours to obtain a microwave dielectric ceramic.

[0073] Comparative Example 6

[0074] A microwave dielectric ceramic with the structural formula 0.81MgTiO3-0.19Ca 0.6 Sm 0.8 / 3 TiO3 is prepared by the following method:

[0075] Using MgO, CaCO3, Sm2O3, and TiO2 as raw materials, respectively according to the above structural formulas for MgTiO3 and Ca... 0.6 Sm 0.8 / 3 The stoichiometric proportions of TiO3 were ball-milled and then calcined at 1170-1200℃ for 2-6 hours to obtain MgTiO3 and Ca. 0.6 Sm 0.8 / 3 TiO3 synthesis material. Then, according to MgTiO3 / Ca... 0.6 Sm 0.8 / 3 The microwave dielectric ceramic is prepared by ball milling and mixing the TiO3 with a molar ratio of 0.81 / 0.19, adding polyvinyl alcohol (PVA) as a binder, pressing and molding the mixture, removing the adhesive, and sintering it at 1350-1370℃ for 3-5 hours.

[0076] Product effectiveness test

[0077] 1. Testing Method

[0078] The microwave dielectric ceramics prepared in the above embodiments and comparative examples were tested for performance according to "GBT 5597-1999 Test method for microwave complex permittivity of solid dielectric".

[0079] 2. Test Results

[0080] Table 1. Key parameters and performance test results of microwave dielectric ceramics in each embodiment and comparative example.

[0081]

[0082]

[0083] As shown in the table above, the microwave dielectric ceramics provided in Examples 1-3 of the present invention have a dielectric constant (K) of 21 ± 1 and a quality factor (Qf) > 70000. In a wide temperature range of -40 to 140°C, the temperature coefficient of its resonant frequency (τf) remains within the range of ±4 ppm / °C, indicating that it not only has a high quality factor but also wide temperature stability.

[0084] Compared with Example 1, when x is less than 0.13, it cannot meet the requirements of temperature stability over a wide temperature range. For example, its τf at high temperature (25-140℃) increases significantly to -8.4ppm / ℃.

[0085] In Comparative Example 2, when y is greater than 0.1, its high-temperature (25-140℃) τf increases to -7.5ppm / ℃, which cannot meet the requirements for wide-temperature stability.

[0086] Comparative Example 3, which replaces La with Sm, reveals that microwave dielectric ceramics cannot meet the requirements for temperature stability over a wide temperature range, with its high-temperature (25-140℃) τf changing to -10.1ppm / ℃.

[0087] In Comparative Example 4, increasing the La content resulted in a decrease in Qf to 54709, which failed to meet the requirements for temperature stability over a wide temperature range. However, the τf at high temperatures (25-140℃) increased to 8.2 ppm / ℃.

[0088] Comparative Example 5 uses pure CaTiO3 as a temperature compensator, which cannot simultaneously meet the requirements for temperature stability over a wide temperature range; at low temperatures, τf > 10 ppm / ℃.

[0089] Comparative Example 6, using pure MgTiO3 as the base material, achieved temperature stability over a wide temperature range, but its quality factor was low. However, this invention provides non-stoichiometric Zn... 1.8 SiO 3.8 As an auxiliary additive, the composition of microwave dielectric ceramics was adjusted, thus ensuring good wide-temperature stability and high quality factor while maintaining the dielectric constant in an adjustable range of 20-22, which is beneficial for the design and manufacturing of devices of different specifications.

Claims

1. A microwave dielectric ceramic, characterized in that, The chemical formula of the microwave dielectric ceramic is shown below: (1-xy)Mg 1.2 Uncle 3.2 -xCa 0.61 The 0.26 TiO3-yZn 1.8 SiO 3.8 ; Where x = 0.13 - 0.16, y = 0.04 - 0.1, and 0.75 ≤ (1 - xy) ≤ 0.

80.

2. A method for preparing microwave dielectric ceramics, characterized in that, Includes the following steps: (1) Mg 1.2 TiO 3.2 Ca 0.61 La 0.26 TiO3 and Zn 1.8 SiO 3.8 Samples were taken and mixed according to the chemical formula of the base material to obtain the first mixture; the chemical formula of the base material is (1-xy)Mg. 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 ; Where x = 0.13 - 0.16, y = 0.04 - 0.1, and 0.75 ≤ (1 - xy) ≤ 0.80; (2) The first mixture and the sintering aid are mixed to obtain the second mixture; (3) Mix the second mixture with the binder, then granulate it, and then press it into shape to obtain a ceramic blank; (4) The ceramic blank is debonded and then sintered to obtain the microwave dielectric ceramic.

3. The preparation method according to claim 2, characterized in that, In step (2), when the first mixture is 100 parts by weight, the amount of the sintering aid is 0.3-1.5 parts.

4. The preparation method according to claim 2, characterized in that, In step (2), the sintering aid includes Al2O3 and / or SiO2.

5. The preparation method according to claim 4, characterized in that, In step (2), the sintering aid comprises 0.1-0.5 parts Al2O3 and 0.2-1.0 parts SiO2 by weight.

6. The preparation method according to claim 2, characterized in that, In step (1), MgO and TiO2 are used as raw materials, according to Mg 1.2 TiO 3.2 Samples were taken according to the specified ratio, mixed evenly, and then subjected to a first calcination to obtain Mg. 1.2 TiO 3.2 .

7. The preparation method according to claim 2, characterized in that, In step (1), CaCO3, La2O3 and TiO2 are used as raw materials, according to Ca 0.61 La 0.26 TiO3 samples were taken according to the specified ratio, mixed evenly, and then subjected to a second calcination to obtain Ca. 0.61 La 0.26 TiO3.

8. The preparation method according to claim 2, characterized in that, In step (1), ZnO and SiO2 are used as raw materials, and Zn... 1.8 SiO 3.8 Samples were taken according to the specified ratio, mixed evenly, and then subjected to a third calcination to obtain Zn. 1.8 SiO 3.8 .

9. The preparation method according to claim 2, characterized in that, In step (4), the sintering temperature is 1300-1340℃, and / or the sintering time is 3-8h.

10. The application of the microwave dielectric ceramic of claim 1 or the microwave dielectric ceramic prepared by any one of claims 2-9 in the preparation of microwave communication equipment.

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