Microwave dielectric ceramic with stable temperature in wide temperature range as well as preparation method and application of microwave dielectric ceramic

Abstract

The invention belongs to the technical field of ceramic materials, and provides a microwave dielectric ceramic with stable temperature in a wide temperature range and a preparation method and application thereof. The chemical formula of the microwave dielectric ceramic provided by the invention is as follows: (1-x-y) Mg < 1.2 > TiO < 3.2-x > Ca < 0.61 > La < 0.26 > TiO < 3-y > Zn < 1.8 > SiO < 3.8 >, wherein x is equal to 0.13-0.16, y is equal to 0.04-0.1, (1-x-y) is larger than or equal to 0.75 and smaller than or equal to 0.80, the dielectric constant (K) of the microwave dielectric ceramic is equal to 21 + / -1, and the quality factor (Qf) is gt; the temperature coefficient of resonance frequency (tau f) is smaller than + / -4ppm / DEG C within the range of-40 DEG C to 140 DEG C. The microwave dielectric ceramic has high-quality factors and wide-temperature stability, can bear large temperature difference and can be well applied to the field of microwave communication, and the temperature coefficient of resonance frequency (tau f) is smaller than + / -4ppm / DEG C within the range of-40 DEG C to 140 DEG C.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and more specifically to a microwave dielectric ceramic with stable temperature within a wide temperature range, and a preparation method and application thereof. Background Art

[0002] As microwave communication technology develops towards high frequency (millimeter wave), high quality factor (Qf) requirements are put forward for microwave components such as dielectric ceramic resonators and filters used therein (the test requires Qf to be greater than 50,000 at the resonant frequency). At the same time, in order to meet the application requirements in different climatic environments, it is required to have excellent temperature stability (near-zero resonant frequency temperature coefficient τf <±4ppm / ℃) within a wide temperature range (-40-140℃).

[0003] MgTiO3-CaTiO3 (MCT) series materials use CaTiO3 with a positive resonant frequency temperature coefficient as a temperature supplement. MCT series materials have high quality factors and low cost, so they have become the preferred materials for microwave communication technology. However, due to the strong nonlinearity of the resonant frequency temperature coefficient of CaTiO3 in a wide temperature range (-40-140℃), that is, the resonant frequency temperature coefficient has a strong temperature dependence, resulting in the resonant frequency temperature coefficient of MCT series materials in a wide temperature range showing a typical high and low temperature "seesaw" phenomenon, that is, when the high temperature (25-140℃) resonant frequency is adjusted to near zero, the low temperature (-40-25℃) resonant frequency temperature coefficient will increase significantly (τf>10ppm / ℃); conversely, if the low temperature resonant frequency temperature coefficient is adjusted to near zero, the high temperature resonant frequency temperature coefficient 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 resonant frequency temperature coefficient at a stable level within a wide temperature range of -40-140°C. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a microwave dielectric ceramic with stable temperature in a wide temperature range and a preparation method and application thereof. The microwave dielectric ceramic provided by the present invention has a resonant frequency temperature coefficient of less than ±4ppm / ℃ in a wide temperature range of -40-140℃, and has not only a high quality factor but also good 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 with stable temperature in a wide temperature range, the chemical formula of the microwave dielectric ceramic is as follows:

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

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

[0010] The present invention is based on the Ca of CaTiO3 2+ Position introduction La 3+ , reducing the nonlinearity of the temperature coefficient of the CaTiO3 resonant frequency and its temperature dependence; and in order to improve its quality factor, the matrix material MgTiO3 was structurally modified by non-stoichiometric method to form a Rulldesden-Popper layered perovskite structure; in addition, the ultra-high quality factor non-stoichiometric Zn2SiO4 matrix (Zn 1.8 SiO 3.8 ) material (quality factor of about 200000) is used as an auxiliary agent to adjust its sintering temperature and dielectric properties; finally, a microwave dielectric ceramic with a wide temperature stability and high quality factor is obtained, with a dielectric constant (K) = 21±1, a quality factor (Qf) > 70000, and a resonant frequency temperature coefficient (τf) less than ±4ppm / ℃ in the range of -40-140℃.

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

[0012] A method for preparing a microwave dielectric ceramic with stable temperature within a wide temperature range comprises 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 According to the chemical formula of the base material, samples are taken and mixed to obtain a first mixed material; 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 ; Wherein, x=0.13-0.16, y=0.04-0.1, 0.75≤(1-xy)≤0.80;

[0014] (2) mixing the first mixed material and a sintering aid to obtain a second mixed material;

[0015] (3) mixing the second mixed material and a binder, granulating the mixture, and pressing the mixture into a shape to obtain a ceramic blank;

[0016] (4) Debinding the ceramic green body and then sintering it to obtain the microwave dielectric ceramic.

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

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

[0019] Further preferably, in step (2), the sintering aid comprises 0.1-0.5 parts of Al2O3 and 0.2-1.0 parts of SiO2 in parts 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 the 1.2 TiO 3.2 The sample is taken in proportion, then mixed evenly, and then the first calcination is performed to obtain Mg 1.2 TiO 3.2 .

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

[0023] Preferably, in step (1), CaCO3, La2O3 and TiO2 are used as raw materials, and the Ca 0.61 La 0.26 TiO3 is sampled in proportion, then mixed evenly, and then calcined for the second time to obtain Ca 0.61 La 0.26 TiO3.

[0024] Preferably, the temperature of the second calcination is 1150-1200° C., and / or the time of the second calcination is 2-6 hours.

[0025] Preferably, in step (1), ZnO and SiO2 are used as raw materials, and Zn 1.8 SiO 3.8 The sample is taken in proportion, then mixed evenly, and then calcined for the third time to obtain Zn 1.8 SiO 3.8 .

[0026] Preferably, the temperature of the third calcination is 1150-1200° C., 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 the compression molding is 160-300 MPa.

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

[0030] A third aspect of the present invention provides an application of a microwave dielectric ceramic that is temperature-stable within a wide temperature range.

[0031] The invention discloses an application of a microwave dielectric ceramic with stable temperature in a wide temperature range in the preparation 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 the present 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 ; wherein x = 0.13-0.16, y = 0.04-0.1, 0.75≤(1-xy)≤0.80, wherein the present invention in CaTiO3 Ca 2+ Position introduction La 3+ The matrix material MgTiO3 was modified by non-stoichiometric method to form a Rulldesden-Popper layered perovskite structure. In addition, a non-stoichiometric Zn2SiO4 matrix (Zn 1.8 SiO 3.8 ) material (quality factor of about 200000) is used as an auxiliary agent to adjust its sintering temperature and dielectric properties; finally, the microwave dielectric ceramic of the present invention has a dielectric constant (K) of 21±1, a quality factor (Qf)>70000, and a resonant frequency temperature coefficient (τf) of less than ±4ppm / ℃ in the range of -40-140℃. It not only has a high quality factor, but also has wide temperature stability, can withstand large temperature differences, and can be well applied to the field of microwave communications. DETAILED DESCRIPTION

[0035] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0036] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or 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 ; Among them, x=0.13, y=0.1, 1-xy=0.77.

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

[0041] (1) Using MgO and TiO2 as raw materials, according to Mg 1.2 TiO 3.2 The materials were mixed and milled according to the chemical formula, dried, and calcined at 1150℃ for 5h 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 The TiO3 chemical formula was used to prepare the material, which was mixed and ball-milled, dried, and calcined at 1200℃ for 3h to obtain the synthetic 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 mixed and milled according to the chemical formula, dried, and calcined at 1200℃ for 2h to obtain the synthetic material Zn 1.8 SiO 3.8 ;

[0042] (2) The three synthetic materials obtained in (1) above are used as raw materials, and (1-xy)Mg 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8(wherein, x=0.13, y=0.1, 1-xy=0.77) mix the materials in a proportion to obtain a mixture, and taking the mass of the mixture as 1, add 0.2wt% of SiO2 and 0.5wt% of Al2O3 as sintering aids to the mixture, and mix to obtain a ceramic powder; ball-mill the ceramic powder, and add polyvinyl alcohol (the mass of PVA accounts for 1.5wt% of the mass of the ceramic powder) as a binder, and granulate to obtain a granulated material;

[0043] (3) dry-pressing the granulated material obtained in (2) at a pressure of 200 MPa to obtain a ceramic green body;

[0044] (4) After debinding, the ceramic green body prepared in (3) is sintered at 1300°C for 4 hours to obtain microwave dielectric ceramics.

[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 ; Among them, x=0.145, y=0.075, 1-xy=0.78.

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

[0049] (1) Using MgO and TiO2 as raw materials, according to Mg 1.2 TiO 3.2 The materials were mixed and milled, dried, and calcined at 1175℃ for 4h 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 The TiO3 chemical formula was used to prepare the material, which was mixed and ball-milled, dried, and calcined at 1175℃ for 5h to obtain the synthetic 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 mixed and milled, dried, and calcined at 1175℃ for 4h to obtain the synthetic material Zn 1.8 SiO 3.8 ;

[0050] (2) The three synthetic materials obtained in (1) above were mixed according to (1-xy)Mg1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 (wherein, x=0.145, y=0.075, 1-xy=0.78) chemical formula ratio, mixing, obtaining a mixture, and taking the mass of the mixture as 1, adding 0.6wt% of SiO2 and 0.3wt% of Al2O3 into the mixture to obtain a ceramic powder; ball milling the ceramic powder, adding polyvinyl alcohol PVA (accounting for 1.5wt% of the mass of the ceramic powder) as a binder, and granulating to obtain a granulated material;

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

[0052] (4) After debinding, the ceramic blank prepared in (3) is sintered at 1320°C for 3 hours to obtain microwave dielectric ceramics.

[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 ; Among them, x=0.16, y=0.05, 1-xy=0.79.

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

[0057] (1) Using MgO and TiO2 as raw materials, according to Mg 1.2 TiO 3.2 The materials were mixed and milled, dried, and calcined at 1150℃ for 7h 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 The TiO3 chemical formula was used to prepare the material, which was mixed and ball-milled, dried, and calcined at 1150℃ for 6h to obtain the synthetic 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 mixed and milled, dried, and calcined at 1150℃ for 6h to obtain the synthetic material Zn1.8 SiO 3.8 ;

[0058] (2) The three synthetic materials obtained in (1) above were mixed according to (1-xy)Mg 1.2 TiO 3.2 -xCa 0.61 La 0.26 TiO3-yZn 1.8 SiO 3.8 (wherein, x=0.16, y=0.05, 1-xy=0.7) chemical formula, mixing materials to obtain a mixture, and taking the mass of the mixture as 1, adding 0.6wt% of SiO2 and 0.3wt% of Al2O3 to the mixture to obtain a ceramic powder; ball milling the ceramic powder, adding polyvinyl alcohol PVA (accounting for 1.5wt% of the mass of the ceramic powder) as a binder, and granulating to obtain a granulated material;

[0059] (3) dry-pressing the granulated material obtained in (2) at a pressure of 300 MPa to obtain a ceramic green body;

[0060] (4) After debinding, the ceramic blank prepared in (3) is sintered at 1340°C for 3 hours to obtain microwave dielectric ceramics.

[0061] Comparative Example 1

[0062] A microwave dielectric ceramic, which is different from Example 1 in that the component contents are different, as shown in Table 1.

[0063] Comparative Example 2

[0064] A microwave dielectric ceramic, which is different from Example 1 in that the component contents are different, as shown in Table 1.

[0065] Comparative Example 3

[0066] A microwave dielectric ceramic, the structural formula of which is 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, the structural formula of which is 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 the microwave dielectric ceramics provided in the above Comparative Examples 1-4 are consistent with that in Example 1, wherein La2O3 is replaced by Sm2O3 in Comparative Example 3.

[0070] Comparative Example 5

[0071] A microwave dielectric ceramic, whose structural formula is 0.95MgTiO3-0.05CaTiO3, and whose preparation method is as follows:

[0072] MgO, CaCO3 and TiO2 are selected as raw materials, and the stoichiometric proportions of MgTiO3 and CaTiO3 in the above structural formula are respectively prepared, and after ball milling and mixing, calcination is performed at 1100-1200°C for 2-6h to obtain a composite material of MgTiO3 and CaTiO3. Then, the composite materials of the two are ball milled and mixed according to the proportion of MgTiO3 / CaTiO3=0.95 / 0.05 (molar ratio), and polyethylene (PVA) is added as a binder, and after compression molding, the composite materials are sintered at 1330-1350°C for 3-5h after debinding to obtain microwave dielectric ceramics.

[0073] Comparative Example 6

[0074] A microwave dielectric ceramic, the structural formula of which is 0.81MgTiO3-0.19Ca 0.6 Sm 0.8 / 3 TiO3, its preparation method is as follows:

[0075] MgO, CaCO3, Sm2O3 and TiO2 were selected as raw materials, and MgTiO3 and CaCO3 in the above structural formula were respectively 0.6 Sm 0.8 / 3 The chemically measured ingredients of TiO3 are ball-milled and mixed, and then calcined at 1170-1200℃ for 2-6h to obtain MgTiO3 and Ca 0.6 Sm 0.8 / 3 TiO3 synthetic material. Then according to MgTiO3 / Ca 0.6 Sm 0.8 / 3 The ratio of TiO3=0.81 / 0.19 (molar ratio) is used. The above two synthetic materials are ball-milled and mixed, and then polyvinyl alcohol (PVA) is added as a binder. After pressing and molding, the materials are sintered at 1350-1370°C for 3-5h after debinding to obtain microwave dielectric ceramics.

[0076] Product effect testing

[0077] 1. Test methods

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

[0079] 2. Test results

[0080] Table 1 Important parameters and performance test results of microwave dielectric ceramics of various embodiments and comparative examples

[0081]

[0082]

[0083] It can be seen from the above table that the microwave dielectric ceramics provided in Examples 1-3 of the present invention have a dielectric constant (K) = 21 ± 1, a quality factor (Qf) > 70000, and a resonant frequency temperature coefficient (τf) within a wide temperature range of -40-140°C, all maintained within the range of ±4ppm / °C, indicating that they not only have a high quality factor, but also have wide temperature stability.

[0084] In Comparative Example 1, when x is less than 0.13, it cannot meet the requirement of temperature stability in a wide temperature range. For example, its τf at high temperature (25-140° C.) increases significantly to -8.4 ppm / ° C.

[0085] In comparative example 2, when y is greater than 0.1, its τf at high temperature (25-140° C.) increases to -7.5 ppm / ° C., which cannot meet the requirement of wide temperature stability.

[0086] In Comparative Example 3, La is replaced by Sm. It can be found that the microwave dielectric ceramic cannot meet the requirement of temperature stability in a wide temperature range, and its τf at high temperature (25-140°C) changes to -10.1ppm / °C.

[0087] In Comparative Example 4, the La content is increased, and it can be found that Qf is reduced to 54709, and the temperature stability requirement cannot be met in a wide temperature range, and its τf at high temperature (25-140°C) increases to 8.2ppm / °C.

[0088] Comparative Example 5 uses pure CaTiO3 as a temperature compensating agent, which cannot simultaneously meet the requirements of temperature stability within a wide temperature range, and τf>10ppm / °C at low temperatures.

[0089] Comparative Example 6 uses pure MgTiO3 as the base material. Although it achieves temperature stability in a wide temperature range, its quality factor is low. 1.8 SiO 3.8 As an auxiliary additive, the composition of microwave dielectric ceramics has been adjusted. Therefore, the dielectric constant can be maintained in an adjustable range of 20-22 while ensuring good wide temperature stability and high quality factor, which is beneficial to the design and manufacture of devices of different specifications.

Claims

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

80.

2. A method for preparing a microwave dielectric ceramic, characterized in that: The steps include: (1) Mg 1.2 TiO 3.2 , Ca 0.61 La 0.26 TiO3 and Zn 1.8 SiO 3.8 According to the chemical formula of the base material, samples are taken and mixed to obtain a first mixed material; 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 ; Wherein, x=0.13-0.16, y=0.04-0.1, 0.75≤(1-xy)≤0.80; (2) mixing the first mixed material and a sintering aid to obtain a second mixed material; (3) mixing the second mixed material and a binder, granulating the mixture, and pressing the mixture into a shape to obtain a ceramic blank; (4) Debinding the ceramic green body and then sintering it to obtain the microwave dielectric ceramic.

3. The preparation method according to claim 2, characterized in that: In step (2), based on weight parts, when the first mixed material is 100 parts, the amount of the sintering aid used 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 includes 0.1-0.5 parts of Al2O3 and 0.2-1.0 parts of SiO2 in parts by weight.

6. The preparation method according to claim 2, characterized in that: In step (1), MgO and TiO2 are used as raw materials, and Mg 1.2 TiO 3.2 The sample is taken in proportion, then mixed evenly, and then the first calcination is performed 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, and the Ca 0.61 La 0.26 TiO3 is sampled in proportion, then mixed evenly, and then calcined for the second time 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 The sample is taken in proportion, then mixed evenly, and then calcined for the third time 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° C., and / or the sintering time is 3-8 hours.

10. Use of the microwave dielectric ceramic according to claim 1 or the microwave dielectric ceramic prepared by the preparation method according to any one of claims 2 to 9 in preparing microwave communication equipment.

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