CN114213125A - Microwave dielectric ceramic and preparation method thereof - Google Patents

Microwave dielectric ceramic and preparation method thereof Download PDF

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CN114213125A
CN114213125A CN202111641898.7A CN202111641898A CN114213125A CN 114213125 A CN114213125 A CN 114213125A CN 202111641898 A CN202111641898 A CN 202111641898A CN 114213125 A CN114213125 A CN 114213125A
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nandmgwo
microwave dielectric
dielectric ceramic
sintering
ball milling
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刘兵
沙柯
周梦飞
林峰立
宋开新
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Hangzhou Dianzi University
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Abstract

The invention discloses a microwave dielectric ceramic and a preparation method thereof. According to the preparation method of the microwave dielectric ceramic, oxide powder with relatively low price is used as a raw material in the preparation process, the preparation process is a standard solid-phase reaction method, the stoichiometric ratio is accurately controlled in the preparation process, the process is simple, the repeatability is good, the synthesized phase is stable and single, and no second phase exists. NaNdMgWO prepared by the preparation method of the invention6The microwave dielectric ceramic has excellent microwave dielectric property.

Description

Microwave dielectric ceramic and preparation method thereof
Technical Field
The invention relates to the technical field of functional electronic ceramic materials, in particular to a microwave dielectric ceramic and a preparation method thereof.
Background
The microwave dielectric ceramic is used as a passive device in a microwave communication system in a microwave frequency band (300 MHz-300 GHz) circuitCritical dielectric materials for components such as resonators, filters, antennas, etc. The three most important performance evaluation indexes of the microwave dielectric ceramic are respectively the dielectric constant of the ceramic
Figure DEST_PATH_IMAGE001
Quality factor ofQfValue and temperature coefficient of resonance frequencyτ f . Wherein the dielectric constant
Figure 62858DEST_PATH_IMAGE001
The size is closely related to the miniaturization of the device size; the quality factor being the inverse of the dielectric loss, i.e.QfThe larger the value, the lower the dielectric loss; the temperature coefficient of the resonant frequency represents the drift degree of the resonant frequency of the material along with the outside temperature.
In recent decades, with the rapid development of wireless communication technology, microwave dielectric ceramics have attracted much attention. In addition, with the increasing requirements of people on information transmission content, speed, quality and the like, new generation information technologies such as 5G mobile communication, internet of things (IoT) technology and the like are emerging, and the microwave communication frequency gradually develops towards the direction of a higher microwave frequency band. As known from classical dispersion theory of dielectrics, dielectric loss gradually increases with increasing frequency. Therefore, in order to meet the application requirements of microwave dielectric ceramics, academic circles and industrial circles put higher demands on the comprehensive properties, especially low loss, of microwave dielectric ceramics. Scientists are actively developing low loss microwave dielectric ceramics (i.e., high quality factor Qf)>10000 GHz) to suppress signal energy attenuation; while paying attention to the dielectric constant
Figure 682058DEST_PATH_IMAGE001
To achieve miniaturization of the device.
At present, tungstate-based microwave dielectric ceramics are widely researched, wherein the researched components mainly comprise Li2WO4And MWO4(M = Mg, Ca, Sr, etc.) as the main, for example, Chinese patent CN201110416939.2 discloses a low dielectric constant microwave dielectric ceramic and its preparation method, the ceramic material composition is: al (Al)2O3+awt%BaLa2(Zr0.1Ti0.9)4O12+bwt%BaWO4+cwt%[xBaO+yWO3]Respectively synthesizing the above-mentioned additive BaLa from correspondent oxide and carbonate according to a certain mole ratio2(Zr0.1Ti0.9)4O12And BaWO4Then, it is mixed with Al2O3、BaCO3And WO3The porcelain is prepared by wet grinding and mixing the raw materials according to the composition of the porcelain in the scheme, drying, adding polyvinyl alcohol (PVA) for compression molding, and sintering in a box furnace or a tunnel furnace for 1-4 h. The dielectric constant of the microwave dielectric ceramic is between 9 and 12, and the dielectric constant is low (generally epsilon)r<10) The demand for miniaturization of the device cannot be satisfied well.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a microwave dielectric ceramic and a preparation method thereof.
In order to solve the problems, the invention adopts the following technical scheme:
the invention provides a microwave dielectric ceramic, wherein the chemical composition expression of the microwave dielectric ceramic is NaNdMgWO6The crystal structure is a monoclinic structure, and the space group is C2/m.
Further, the relative dielectric constant of the microwave dielectric ceramic
Figure 11408DEST_PATH_IMAGE001
14.5 to 15.7, quality factorQf10850-20500 GHz, temperature coefficient of resonance frequencyτ f Is-56 ppm/DEG C to-42 ppm/DEG C.
The invention also provides a preparation method of the microwave dielectric ceramic, which comprises the following steps:
(1) preparing materials: mixing raw material Na2CO3、Nd2O3、MgO、WO3According to NaNdMgWO6The stoichiometric ratio of (A) is used for proportioning;
(2) mixing materials: carrying out wet ball milling on the mixed material obtained by burdening and absolute ethyl alcohol to obtain a slurry-like raw material;
(3) drying: drying the slurry raw material to constant weight to obtain a dry mixture;
(4) pre-burning: sieving and dispersing the mixture, and then pre-sintering to obtain NaNdMgWO6Powder;
(5) ball milling: to the NaNdMgWO6Adding anhydrous ethanol into the powder, and grinding for the second time to obtain NaNdMgWO6Sizing agent;
(6) drying: the NaNdMgWO6Drying the slurry to constant weight to obtain NaNdMgWO6A compound powder;
(7) tabletting: the NaNdMgWO6Sieving compound powder, and pressing the sieved material into a green body;
(8) and (3) sintering: sintering the green body to obtain NaNdMgWO6Microwave dielectric ceramics;
(9) grinding and polishing the ceramic surface: the NaNdMgWO obtained after sintering6And grinding and polishing the surface of the microwave dielectric ceramic.
Preferably, in the step (4), the pre-sintering treatment temperature is 1100-1200 ℃ and the time is 1-4 h.
Preferably, in the step (8), the sintering treatment temperature is 1500-1600 ℃ and the time is 1-4 h.
Further, in the step (4), the temperature rise rate of the pre-sintering treatment is 5 ℃/min to 10 ℃/min, and the pre-sintering treatment is followed by natural cooling to room temperature.
Further, in the step (8), the temperature rise rate of the sintering treatment is 1 ℃/min to 5 ℃/min.
Furthermore, in the step (8), after the sintering treatment, the temperature is reduced to 1100-1200 ℃ at a speed of 1-5 ℃/min, and then the temperature is naturally cooled to the room temperature.
Preferably, in the step (2) and the step (5), the ball milling beads are ZrO2。
Preferably, the mixture, ZrO2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3.
Compared with the prior art, the invention has the technical effects that:
the microwave dielectric ceramic has excellent microwave dielectric property and can meet the requirements of passive devices in a microwave communication system. The dielectric constant of the microwave dielectric ceramic is higher than that of common Li2WO4And MWO4And (M = Mg, Ca, Sr and the like) tungstate system is beneficial to realizing the miniaturization of the device.
According to the preparation method of the microwave dielectric ceramic, oxide powder with relatively low price is used as a raw material in the preparation process, the preparation process is a standard solid-phase reaction method, the stoichiometric ratio is accurately controlled in the preparation process, the process is simple, the repeatability is good, the synthesized phase is stable and single, and no second phase exists.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
It will be appreciated by those skilled in the art that the objects and advantages that can be achieved with the present invention are not limited to the specific details set forth above, and that these and other objects that can be achieved with the present invention will be more clearly understood from the detailed description that follows.
Drawings
FIG. 1 shows a microwave dielectric ceramic NaNdMgWO according to embodiment 1 of the present invention6The XRD pattern of (A) and the refined result thereof;
FIG. 2 shows a microwave dielectric ceramic NaNdMgWO according to embodiment 1 of the present invention6The crystal structure of (1);
FIG. 3 is a microwave dielectric ceramic NaNdMgWO provided in embodiment 4 of the present invention6Scanning electron micrographs of (a).
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
It is to be understood that the processing equipment or apparatus not specifically identified in the following examples is conventional in the art.
Furthermore, it is to be understood that one or more method steps mentioned in the present invention does not exclude that other method steps may also be present before or after the combined steps or that other method steps may also be inserted between these explicitly mentioned steps, unless otherwise indicated; moreover, unless otherwise indicated, the numbering of the various method steps is merely a convenient tool for identifying the various method steps, and is not intended to limit the order in which the method steps are arranged or the scope of the invention in which the invention may be practiced, and changes or modifications in the relative relationship may be made without substantially changing the technical content.
The embodiment of the invention provides a microwave dielectric ceramic, and the chemical composition expression of the microwave dielectric ceramic is NaNdMgWO6The crystal structure is a monoclinic structure, and the space group is C2/m.
Further, the relative dielectric constant of the microwave dielectric ceramic
Figure 272625DEST_PATH_IMAGE001
14.5 to 15.7, quality factorQf10850-20500 GHz, temperature coefficient of resonance frequencyτ f Is-56 ppm/DEG C to-42 ppm/DEG C.
The embodiment of the invention also provides a preparation method of the microwave dielectric ceramic, which comprises the following steps:
(1) preparing materials: mixing raw material Na2CO3、Nd2O3、MgO、WO3According to NaNdMgWO6The stoichiometric ratio of (A) is used for proportioning; preferably, high-purity chemical raw materials with the purity of Na respectively are selected2CO3 （99.9%）、Nd2O3（99.99%）、MgO（99.99%）、WO3（99.99%）。
(2) Mixing materials: carrying out wet ball milling on the mixed material obtained by burdening and absolute ethyl alcohol to obtain a slurry-like raw material; the ball milling uses a planetary ball mill, the rotating speed range is 150 r/min-200 r/min, the ball milling beads are ZrO2. Mixed material, ZrO2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is preferably 1:6: 3.
(3) Drying: putting the slurry raw material into a drying oven to be dried to constant weight to obtain a dry mixture;
(4) pre-burning: the mixture is screened and dispersed and then is put into a high-temperature furnace for presintering treatment to prepare NaNdMgWO6Powder; the pre-sintering temperature can be 1100-1200 deg.C, such as 1120 deg.C, 1160 deg.C, 1180 deg.C, etc.; the pre-sintering treatment time is 1-4 h, such as 2h and 3 h. The temperature rising rate of the pre-sintering treatment can be selected to be 5-10 ℃/min, and the pre-sintering treatment is carried out and then the product is naturally cooled to the room temperature.
(5) Ball milling: to NaNdMgWO6Adding anhydrous ethanol into the powder, and placing the powder in a ball mill for secondary grinding to form NaNdMgWO6Sizing agent; the rotating speed range of the ball mill is 150 r/min-200 r/min, and the ball milling beads are ZrO2。NaNdMgWO6Powder, ZrO2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is preferably 1:6: 3.
(6) Drying: mixing NaNdMgWO6The slurry is placed in an oven to be dried to constant weight to obtain NaNdMgWO6A compound powder;
(7) tabletting: mixing NaNdMgWO6Sieving compound powder, and pressing the sieved material into a cylindrical green body;
(8) and (3) sintering: sintering the cylindrical green body to obtain NaNdMgWO6Microwave dielectric ceramics; the sintering temperature can be 1500-1600 deg.C, such as 1525 deg.C, 1550 deg.C, 1575 deg.C; the time is 1-4 h, such as 2h and 3 h. The temperature rise rate of the sintering treatment can be selected to be 1-5 ℃/min. After sintering treatment, the temperature is reduced to 1100-1200 ℃ at the speed of 1-5 ℃/min, and then the mixture is naturally cooled to room temperature.
(9) Grinding and polishing the ceramic surface: the NaNdMgWO obtained after sintering6And grinding and polishing the surface of the microwave dielectric ceramic.
The microwave dielectric ceramic has excellent microwave dielectric property and can meet the requirements of passive devices in a microwave communication system. The dielectric constant of the microwave dielectric ceramic is higher than that of common Li2WO4And MWO4And (M = Mg, Ca, Sr and the like) tungstate system is beneficial to realizing the miniaturization of the device.
According to the preparation method of the microwave dielectric ceramic, oxide powder with relatively low price is used as a raw material in the preparation process, the preparation process is a standard solid-phase reaction method, the stoichiometric ratio is accurately controlled in the preparation process, the process is simple, the repeatability is good, the synthesized phase is stable and single, and no second phase exists.
The following is a further description with reference to specific examples.
Example 1
Embodiment 1 of the invention provides a microwave dielectric ceramic NaNdMgWO6The preparation method comprises the following steps:
(1) preparing materials: mixing raw material Na2CO3(purity 99.9%) and Nd2O3(purity 99.99%), MgO (purity 99.99%), WO3(purity 99.99%) according to NaNdMgWO6The stoichiometric ratio of (A) is used for proportioning;
(2) mixing materials: the material obtained by proportioning and ZrO2Ball milling beads and absolute ethyl alcohol are placed in a ball mill according to a preset mass ratio for wet ball milling to obtain slurry raw materials, a planetary ball mill is used for ball milling, the rotating speed is 150r/min, and the materials and ZrO are mixed2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3;
(3) drying: putting the slurry raw material in the step (2) into an oven to be dried to constant weight to obtain a dry mixture;
(4) pre-burning: sieving and dispersing the mixture obtained in the step (3), then placing the mixture into a high-temperature furnace, raising the temperature to 1100 ℃ at the speed of 10 ℃/min, pre-sintering for 3 hours, and naturally cooling to room temperature after pre-sintering to obtain NaNdMgWO6Powder;
(5) ball milling: mixing the NaNdMgWO obtained in the step (4)6Adding anhydrous ethanol into the powder, and placing inSecondarily grinding in a ball mill at the rotating speed of 150r/min to form NaNdMgWO6Sizing agent; NaNdMgWO6Powder, ZrO2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3;
(6) drying: drying the slurry obtained in the step (5) in an oven to constant weight to obtain NaNdMgWO6A compound powder;
(7) tabletting: sieving the powder obtained in the step (6), and pressing the sieved material into a cylindrical green body;
(8) and (3) sintering: heating the cylindrical green body to 1500 ℃ at the speed of 5 ℃/min for sintering for 3h, then cooling to 1100 ℃ at the speed of 2 ℃/min, and finally naturally cooling for sintering to obtain NaNdMgWO6Microwave dielectric ceramics;
(9) grinding and polishing the ceramic surface: the surface of the ceramic obtained after sintering is ground and polished.
As shown in the following Table 1, the microwave dielectric ceramic NaNdMgWO of the present example6Has a relative density of 91.6%, a dielectric constant of 14.5, a quality factor of 10850GHz, and a temperature coefficient of resonance frequency of-56 ppm/DEG C.
FIG. 1 shows a microwave dielectric ceramic NaNdMgWO of the present embodiment6XRD pattern and refined result of the said product. As can be seen from the figure, NaNdMgWO was successfully synthesized in this example6Phase, and from the refinement results: excellent reliability parameters (R p =7.07%, R wp =9.63%，R exp =5.88%，χ2= 2.68) it can be seen that no other second phase is present in this example. In addition, FIG. 2 also shows the corresponding crystal structure of the fine modification, from which it can be seen that NaNdMgWO6The crystal structure is a monoclinic structure, and the space group is C2/m.
The microwave dielectric ceramic NaNdMgWO of the following examples6The XRD pattern of (A) is the same as that of the present embodiment, and is not described in detail later.
Example 2
Embodiment 2 of the invention provides a microwave dielectric ceramic NaNdMgWO6The preparation method comprises the following steps:
(1) preparing materials: mixing raw material Na2CO3(purity 99.9)%）、Nd2O3(purity 99.99%), MgO (purity 99.99%), WO3(purity 99.99%) according to NaNdMgWO6The stoichiometric ratio of (A) is used for proportioning;
(2) mixing materials: the material obtained by proportioning and ZrO2Ball milling beads and absolute ethyl alcohol are placed in a ball mill according to a preset mass ratio for wet ball milling to obtain slurry raw materials, a planetary ball mill is used for ball milling, the rotating speed is 150r/min, and the materials and ZrO are mixed2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3;
(3) drying: putting the slurry raw material in the step (2) into an oven to be dried to constant weight to obtain a dry mixture;
(4) pre-burning: sieving and dispersing the mixture obtained in the step (3), then placing the mixture into a high-temperature furnace, raising the temperature to 1100 ℃ at the speed of 10 ℃/min, pre-sintering for 3 hours, and naturally cooling to room temperature after pre-sintering to obtain NaNdMgWO6Powder;
(5) ball milling: mixing the NaNdMgWO obtained in the step (4)6Adding absolute ethyl alcohol into the powder, placing the powder into a ball mill for secondary grinding at the rotating speed of 150r/min to form NaNdMgWO6Sizing agent; NaNdMgWO6Powder, ZrO2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3;
(6) drying: drying the slurry obtained in the step (5) in an oven to constant weight to obtain NaNdMgWO6A compound powder;
(7) tabletting: sieving the powder obtained in the step (6), and pressing the sieved material into a cylindrical green body;
(8) and (3) sintering: heating the cylindrical green body to 1525 ℃ at the speed of 5 ℃/min for sintering for 3h, then cooling to 1100 ℃ at the speed of 2 ℃/min, and finally naturally cooling for sintering to obtain NaNdMgWO6Microwave dielectric ceramics;
(9) grinding and polishing the ceramic surface: the surface of the ceramic obtained after sintering is ground and polished.
As shown in the following Table 1, the microwave dielectric ceramic NaNdMgWO of the present example6Has a relative density of 92.5%, a dielectric constant of 14.9, a quality factor of 13570GHz, and a temperature coefficient of resonance frequency of-52.5 ppm/DEG C.
Example 3
Embodiment 3 of the invention provides a microwave dielectric ceramic NaNdMgWO6The preparation method comprises the following steps:
(1) preparing materials: mixing raw material Na2CO3(purity 99.9%) and Nd2O3(purity 99.99%), MgO (purity 99.99%), WO3(purity 99.99%) according to NaNdMgWO6The stoichiometric ratio of (A) is used for proportioning;
(2) mixing materials: the material obtained by proportioning and ZrO2Ball milling beads and absolute ethyl alcohol are placed in a ball mill according to a preset mass ratio for wet ball milling to obtain slurry raw materials, a planetary ball mill is used for ball milling, the rotating speed is 150r/min, and the materials and ZrO are mixed2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3;
(3) drying: putting the slurry raw material in the step (2) into an oven to be dried to constant weight to obtain a dry mixture;
(4) pre-burning: sieving and dispersing the mixture obtained in the step (3), then placing the mixture into a high-temperature furnace, raising the temperature to 1100 ℃ at the speed of 10 ℃/min, pre-sintering for 3 hours, and naturally cooling to room temperature after pre-sintering to obtain NaNdMgWO6Powder;
(5) ball milling: mixing the NaNdMgWO obtained in the step (4)6Adding absolute ethyl alcohol into the powder, placing the powder into a ball mill for secondary grinding at the rotating speed of 150r/min to form NaNdMgWO6Sizing agent; NaNdMgWO6Powder, ZrO2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3;
(6) drying: drying the slurry obtained in the step (5) in an oven to constant weight to obtain NaNdMgWO6A compound powder;
(7) tabletting: sieving the powder obtained in the step (6), and pressing the sieved material into a cylindrical green body;
(8) and (3) sintering: heating the cylindrical green body to 1550 ℃ at the speed of 5 ℃/min for sintering for 3h, then cooling to 1100 ℃ at the speed of 2 ℃/min, and finally naturally cooling for sintering to obtain the NaNdMgWO6Microwave dielectric ceramics;
(9) grinding and polishing the ceramic surface: the surface of the ceramic obtained after sintering is ground and polished.
As shown in the following Table 1, the microwave dielectric ceramic NaNdMgWO of the present example6Has a relative density of 93.2%, a dielectric constant of 15.1, a quality factor of 16570GHz, and a temperature coefficient of resonance frequency of-49 ppm/DEG C.
Example 4
Embodiment 4 of the invention provides a microwave dielectric ceramic NaNdMgWO6The preparation method comprises the following steps:
(1) preparing materials: mixing raw material Na2CO3(purity 99.9%) and Nd2O3(purity 99.99%), MgO (purity 99.99%), WO3(purity 99.99%) according to NaNdMgWO6The stoichiometric ratio of (A) is used for proportioning;
(2) mixing materials: the material obtained by proportioning and ZrO2Ball milling beads and absolute ethyl alcohol are placed in a ball mill according to a preset mass ratio for wet ball milling to obtain slurry raw materials, a planetary ball mill is used for ball milling, the rotating speed is 150r/min, and the materials and ZrO are mixed2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3;
(3) drying: putting the slurry raw material in the step (2) into an oven to be dried to constant weight to obtain a dry mixture;
(4) pre-burning: sieving and dispersing the mixture obtained in the step (3), then placing the mixture into a high-temperature furnace, raising the temperature to 1100 ℃ at the speed of 10 ℃/min, pre-sintering for 3 hours, and naturally cooling to room temperature after pre-sintering to obtain NaNdMgWO6Powder;
(5) ball milling: mixing the NaNdMgWO obtained in the step (4)6Adding absolute ethyl alcohol into the powder, placing the powder into a ball mill for secondary grinding at the rotating speed of 150r/min to form NaNdMgWO6Sizing agent; NaNdMgWO6Powder, ZrO2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3;
(6) drying: drying the slurry obtained in the step (5) in an oven to constant weight to obtain NaNdMgWO6A compound powder;
(7) tabletting: sieving the powder obtained in the step (6), and pressing the sieved material into a cylindrical green body;
(8) and (3) sintering: heating the cylindrical green body to 1575 ℃ at the speed of 5 ℃/min for sintering for 3h, then cooling to 1100 ℃ at the speed of 2 ℃/min, and finally naturally cooling for sintering to obtain NaNdMgWO6Microwave dielectric ceramics;
(9) grinding and polishing the ceramic surface: the surface of the ceramic obtained after sintering is ground and polished.
As shown in the following Table 1, the microwave dielectric ceramic NaNdMgWO of the present example6The relative density of (A) is 95.2%, the dielectric constant is 15.4, the quality factor is 20500GHz, and the temperature coefficient of the resonant frequency is-43 ppm/DEG C.
As shown in FIG. 3, the microwave dielectric ceramic NaNdMgWO of the present embodiment is6The scanning electron micrograph of (2) shows that the microwave dielectric ceramic NaNdMgWO of the embodiment6A dense microstructure is obtained with a uniform grain size distribution.
Example 5
Embodiment 5 of the invention provides a microwave dielectric ceramic NaNdMgWO6The preparation method comprises the following steps:
(1) preparing materials: mixing raw material Na2CO3(purity 99.9%) and Nd2O3(purity 99.99%), MgO (purity 99.99%), WO3(purity 99.99%) according to NaNdMgWO6The stoichiometric ratio of (A) is used for proportioning;
(2) mixing materials: the material obtained by proportioning and ZrO2Ball milling beads and absolute ethyl alcohol are placed in a ball mill according to a preset mass ratio for wet ball milling to obtain slurry raw materials, a planetary ball mill is used for ball milling, the rotating speed is 150r/min, and the materials and ZrO are mixed2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3;
(3) drying: putting the slurry raw material in the step (2) into an oven to be dried to constant weight to obtain a dry mixture;
(4) pre-burning: sieving and dispersing the mixture obtained in the step (3), then placing the mixture into a high-temperature furnace, raising the temperature to 1100 ℃ at the speed of 10 ℃/min, pre-sintering for 3 hours, and naturally cooling to room temperature after pre-sintering to obtain NaNdMgWO6Powder;
(5) ball milling: will step withNaNdMgWO of step (4)6Adding absolute ethyl alcohol into the powder, placing the powder into a ball mill for secondary grinding at the rotating speed of 150r/min to form NaNdMgWO6Sizing agent; NaNdMgWO6Powder, ZrO2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3;
(6) drying: drying the slurry obtained in the step (5) in an oven to constant weight to obtain NaNdMgWO6A compound powder;
(7) tabletting: sieving the powder obtained in the step (6), and pressing the sieved material into a cylindrical green body;
(8) and (3) sintering: heating the cylindrical green body to 1600 ℃ at the speed of 5 ℃/min, sintering for 3h, cooling to 1100 ℃ at the speed of 2 ℃/min, and finally naturally cooling for sintering to obtain NaNdMgWO6Microwave dielectric ceramics;
(9) grinding and polishing the ceramic surface: the surface of the ceramic obtained after sintering is ground and polished.
As shown in the following Table 1, the microwave dielectric ceramic NaNdMgWO of the present example6Has a relative compactness of 96.0%, a dielectric constant of 15.7, a quality factor of 19850GHz, and a temperature coefficient of resonance frequency of-42 ppm/DEG C.
The relative density of the samples in the above examples was measured by Archimedes drainage method, and the microwave dielectric properties at the resonant frequency of the cylindrical ceramic were measured by a dielectric resonator method proposed by Hakki-Coleman, the specific performance parameters being shown in Table 1 below.
Figure 3821DEST_PATH_IMAGE002
As seen from the above Table 1, in the above five examples, the microwave dielectric ceramic NaNdMgWO prepared in example 56The relative density and dielectric constant of (a) are highest, with values of 96.0% and 15.7, respectively; example 4 the microwave dielectric ceramic NaNdMgWO prepared6The figure of merit of (2) is preferably 20500 GHz.
The present invention is not limited to the above-described specific embodiments, and various modifications and variations are possible. Any modifications, equivalents, improvements and the like made to the above embodiments in accordance with the technical spirit of the present invention should be included in the scope of the present invention.

Claims (10)

1. The microwave dielectric ceramic is characterized in that the chemical composition expression of the microwave dielectric ceramic is NaNdMgWO6。
2. A microwave dielectric ceramic according to claim 1, wherein the microwave dielectric ceramic has a relative dielectric constant
Figure DEST_PATH_IMAGE002
14.5 to 15.7, quality factorQf10850-20500 GHz, temperature coefficient of resonance frequencyτ f Is-56 ppm/DEG C to-42 ppm/DEG C.
3. A method of producing a microwave dielectric ceramic as claimed in claim 1 or 2, comprising the steps of:
(1) preparing materials: mixing raw material Na2CO3、Nd2O3、MgO、WO3According to NaNdMgWO6The stoichiometric ratio of (A) is used for proportioning;
(2) mixing materials: carrying out wet ball milling on the mixed material obtained by burdening and absolute ethyl alcohol to obtain a slurry-like raw material;
(3) drying: drying the slurry raw material to constant weight to obtain a dry mixture;
(4) pre-burning: sieving and dispersing the mixture, and then pre-sintering to obtain NaNdMgWO6Powder;
(5) ball milling: to the NaNdMgWO6Adding anhydrous ethanol into the powder, and grinding for the second time to obtain NaNdMgWO6Sizing agent;
(6) drying: the NaNdMgWO6Drying the slurry to constant weight to obtain NaNdMgWO6A compound powder;
(7) tabletting: the NaNdMgWO6Sieving the compound powder, and pressing the sieved material into raw materialBlank;
(8) and (3) sintering: sintering the green body to obtain NaNdMgWO6Microwave dielectric ceramics;
(9) grinding and polishing the ceramic surface: the NaNdMgWO obtained after sintering6And grinding and polishing the surface of the microwave dielectric ceramic.
4. The method for preparing microwave dielectric ceramic according to claim 3, wherein in the step (4), the pre-sintering treatment temperature is 1100-1200 ℃ and the time is 1-4 h.
5. The method for preparing microwave dielectric ceramic according to claim 3, wherein in the step (8), the sintering treatment temperature is 1500-1600 ℃ and the time is 1-4 h.
6. The method for preparing microwave dielectric ceramic according to claim 4, wherein in the step (4), the temperature rise rate of the pre-sintering treatment is 5 ℃/min to 10 ℃/min, and the pre-sintering treatment is followed by natural cooling to room temperature.
7. The method for preparing microwave dielectric ceramic as claimed in claim 5, wherein in the step (8), the temperature rise rate of the sintering treatment is 1 ℃/min to 5 ℃/min.
8. The method for preparing microwave dielectric ceramic according to claim 7, wherein in the step (8), the temperature is reduced to 1100-1200 ℃ at a speed of 1-5 ℃/min after the sintering treatment, and then the ceramic is naturally cooled to room temperature.
9. A microwave dielectric ceramic preparation method as claimed in claim 3, wherein in step (2) and step (5), the ball milling beads are ZrO2。
10. According to claimA method for preparing a microwave dielectric ceramic as claimed in claim 9, characterized in that the mixture of materials, ZrO2The mass ratio of the ball milling beads to the absolute ethyl alcohol solvent is 1:6: 3.
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