CN117229056A - High-dielectric aluminum-doped perovskite structure high-entropy microwave dielectric ceramic and preparation method thereof - Google Patents
High-dielectric aluminum-doped perovskite structure high-entropy microwave dielectric ceramic and preparation method thereof Download PDFInfo
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Abstract
The application discloses a high-entropy microwave dielectric ceramic with a high dielectric aluminum doped perovskite structure and a preparation method thereof, and belongs to the technical field of ceramic materials in the field of communication. The chemical general formula of the high-entropy microwave dielectric ceramic is (Zn 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1‑ x Al x O 3 Wherein: x=0-0.1. The method introduces the high entropy concept into the perovskite structure microwave dielectric ceramic to try to regulate and control the dielectric property for the first time based on the unique effect of the high entropy, and successfully synthesizes the aluminum doped high entropy microwave dielectric ceramic by controlling the sintering temperature, the reaction time, the doping content and other technological parameters. The dielectric constant is 74-91, the dielectric loss is 0.001-0.002, the temperature coefficient of resonance frequency is 175-217 ppm/DEG C, and excellent microwave dielectric performance is obtained. The high-dielectric microwave dielectric ceramic obtained by the application is expected to be applied to displacementA mobile terminal, a communication base station, and the like.
Description
Technical Field
The application belongs to the technical field of ceramic materials in the communication field, and particularly relates to a high-entropy microwave dielectric ceramic with a high dielectric aluminum-doped perovskite structure and a preparation method thereof.
Background
In recent years, mobile communication technologies such as satellite communication, positioning navigation and 5G technology are rapidly developed, and microwave dielectric ceramics are widely used as functional materials in microwave frequency band circuits for automobile phones, satellite direct broadcast televisions, satellite communication, medical diagnosis instruments and the like. Meanwhile, the material is taken as a key material of microwave components and is paid attention to by more researchers, performance requirements such as high frequency, integration, miniaturization and intelligence are also provided for the microwave dielectric ceramic material, and the size and the dielectric constant of the microwave dielectric ceramic material have inverse proportion, so that the larger the dielectric constant is more beneficial to the miniaturization of products, the material with smaller dielectric constant has good application at present, but for high dielectric constant, a basic conflict exists on the basic physical layer of the material, namely, the atomic polarization process necessary for realizing the high dielectric constant inevitably causes dielectric loss and the temperature dependence of the dielectric constant. Therefore, the development of microwave dielectric ceramics with high dielectric constant and proper performance is an urgent need of the electronic market, and the exploration of new systems is still in the primary stage.
The high-entropy ceramic is a brand new ceramic material after high-entropy alloy, and a large number of students are attracted due to the unique effect of the high-entropy ceramic. The high-entropy perovskite oxide has the advantages that the high-entropy perovskite oxide allows larger tolerance factors, is rich in crystal structure variety, so that the high-entropy perovskite oxide is widely researched, and the selectivity of high-entropy components, the adjustability of component concentration and the diversity of performance provide a new way for the performance regulation of microwave dielectric ceramics. The existing high-entropy perovskite ceramics are concentrated on thermoelectric, ferroelectric and energy storage, and no research on the high-dielectric high-entropy ceramics in the field of microwave media is currently studied.
Disclosure of Invention
In view of the above research background, the present application aims to apply the high entropy concept to perovskite ceramics for the first time, and try to explore a microwave dielectric ceramic with high dielectric constant. Therefore, the application provides a high-entropy microwave dielectric ceramic with a high dielectric aluminum doped perovskite structure and a preparation method thereof.
In order to achieve the above purpose, the present application provides the following technical solutions:
a high-entropy microwave dielectric ceramic with a high dielectric aluminum-doped perovskite structure, which has a chemical general formula of (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 Wherein: x=0-0.1. x may preferably be 0, 0.02, 0.04, 0.06, 0.08, 0.1.
The application also provides a preparation method of the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure, which comprises the following steps:
1) Weighing ZnO and CaCO as raw materials according to stoichiometric ratio 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 And Al 2 O 3 Adding a solvent, and performing ball milling to obtain mixed slurry;
2) Drying the mixed slurry, presintering the obtained powder, performing secondary ball milling, and continuing drying to obtain dry powder;
3) Granulating the dry powder, and sequentially placing the granulated dry powder into a hydraulic press and a cold isostatic press to be pressed into ceramic green bodies;
4) Sintering the ceramic green body in a protective gas atmosphere to obtain (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 And (3) carrying out mechanical processing on the high-entropy ceramic block, and then cleaning and drying to obtain the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure.
Further, the raw material ZnO, caCO 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 And Al 2 O 3 The purity of (2) is more than 99.5%.
Further, the raw material ZnO, caCO 3 、BaCO 3 SrO and La 2 O 3 The mol ratio of the Zn, ba, ca, sr, la elements is 1:1:1:1:2.
Further, in the ball milling process of the step 1) and the step 2), the grinding medium is agate balls, the organic solvent is ethanol, a star-type ball mill is adopted, the ball-material ratio is 6:1, the ball milling time is 8 hours, the rotating speed is 300r/min, and the ball milling process is carried out for 10 minutes every 30 minutes.
Further, the pre-sintering in the step 2) refers to pre-sintering for 2 hours at 1000 ℃. The drying is performed at 80 ℃ for 10 hours.
Further, the parameters set by the hydraulic machine in the step 3) are as follows: the pressure is 150-200MPa, and the pressure holding time is 3-5min; the parameters set by the cold isostatic press are as follows: the pressure is 250-300MPa, and the pressure holding time is 15-20min. And the diameter of the grinding tool used in the pressing process is 10mm.
Further, the binder used in the granulation process in step 3) is a 5wt% PVA aqueous solution, and the binder is used in an amount of 8% by volume of the dry powder.
Further, the sintering in the step 4) means that the temperature is kept at 1325-1400 ℃ for 4 hours. The machining refers to machining the high-entropy ceramic block into a sample with the size of 5mm high and the diameter of 8.5 mm.
The application is based on C-M theory by doping Al with low ion polarization rate 3+ High polarization ratio of the de-substituted ions Ti 4 + The temperature coefficient of the resonant frequency of the traditional perovskite is reduced while maintaining a high dielectric constant and a lower dielectric loss, and the fit of the grain size is used to prove the influence on the dielectric loss.
Compared with the prior art, the application has the following advantages and technical effects:
the method introduces the high entropy concept into the perovskite structure microwave dielectric ceramic to try to regulate and control the dielectric property for the first time based on the unique effect of the high entropy, and successfully synthesizes the aluminum doped high entropy microwave dielectric ceramic by controlling the sintering temperature, the reaction time, the doping content and other technological parameters. The dielectric constant is 74-91, the dielectric loss is 0.001-0.002, the temperature coefficient of resonance frequency is 175-217 ppm/DEG C, and excellent microwave dielectric performance is obtained. The high-dielectric microwave dielectric ceramic obtained by the application is expected to be applied to mobile terminals, communication base stations and the like.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
FIG. 1 is an X-ray diffraction diagram of a high-entropy microwave dielectric ceramic with a high dielectric aluminum-doped perovskite structure prepared in examples 1-6 of the present application;
FIG. 2 is an SEM microstructure of the high-entropy microwave dielectric ceramic with a high dielectric aluminum-doped perovskite structure prepared in examples 1-6 of the present application; wherein (a) is example 1, (b) is example 2, (c) is example 3, (d) is example 4, (e) is example 5, and (f) is example 6;
FIG. 3 is a histogram of the grain size frequency distribution of the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure prepared in examples 1-6 of the present application; wherein (a) is example 1, (b) is example 2, (c) is example 3, (d) is example 4, (e) is example 5, and (f) is example 6;
FIG. 4 is a graph showing the dielectric constant of the high-entropy microwave dielectric ceramics with the perovskite structure doped with high dielectric aluminum prepared in examples 1-6 of the present application;
FIG. 5 is a Qf diagram of the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure prepared in examples 1-6 of the present application;
FIG. 6 is a temperature coefficient diagram of the resonant frequency of the high-entropy microwave dielectric ceramic with perovskite structure doped with high dielectric aluminum prepared in examples 1-6 of the present application.
Detailed Description
Various exemplary embodiments of the application will now be described in detail, which should not be considered as limiting the application, but rather as more detailed descriptions of certain aspects, features and embodiments of the application.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the application. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the application described herein without departing from the scope or spirit of the application. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present application. The specification and examples of the present application are exemplary only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.
The "room temperature" as used herein is calculated as 25.+ -. 2 ℃ unless otherwise indicated.
The raw materials used in the following examples of the present application are all commercially available.
The application provides a high-entropy microwave dielectric ceramic with a high dielectric aluminum doped perovskite structure, which has a chemical general formula of (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 Wherein: x=0-0.1. x may preferably be 0, 0.02, 0.04, 0.06, 0.08, 0.1.
The application also provides a preparation method of the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure, which comprises the following steps:
step (1): znO and CaCO are mixed 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 、Al 2 O 3 According to the target product (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 Stoichiometric ratio of (x=0, 0.02, 0.04, 0.06, 0.08, 0.1), wherein the molar ratio of Zn, ba, ca, sr, la metal elements is 1:1:1:2, adding solvent and ball milling in planetary ball mill to obtain mixed slurry;
step (2): placing the mixed slurry obtained in the step (1) in an electrothermal blowing drying oven for drying to obtain dried powder;
step (3): presintering the dried powder obtained in the step (2), performing secondary ball milling, and repeating the operation of the step (2);
step (4): granulating the dried powder obtained in the step (3), and then sequentially putting the granulated powder into a hydraulic press and a cold isostatic press to obtain a ceramic green body; the granulation in the step is to mix the dry powder with the PVA binder;
step (5): sintering the ceramic green body obtained in the step (4) in an atmosphere sintering furnace to obtain (Zn) 1/6 Ba 1/ 6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 And (3) carrying out mechanical processing on the high-entropy ceramic block, and then cleaning and drying to obtain the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure.
In the following example step (1) of the present application, the raw materials ZnO, caCO 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 And Al 2 O 3 The purity of (2) is more than 99.5%.
In the ball milling process of the step (1) and the step (3), the grinding medium is agate balls, the organic solvent is ethanol, a star ball mill is adopted, the ball-material ratio is 6:1, the ball milling time is 8h, the rotating speed is 300r/min, and the ball mill has a rest for 10min every 30min during ball milling.
In the steps (2) and (3) according to some preferred embodiments of the present application, the drying refers to drying at 80 ℃ for 10 hours.
In some preferred embodiments of the present application, in step (3), the pre-firing means pre-firing for 2 hours at 1000 ℃.
In step (4) of some preferred embodiments of the present application, the parameters set by the hydraulic machine are: the pressure is 150-200MPa, preferably 150MPa, and the pressure holding time is 3-5min, preferably 3min; the parameters set by the cold isostatic press are as follows: the pressure is 250-300MPa, preferably 250MPa, and the pressure holding time is 15-20min, preferably 15min. And the diameter of the grinding tool used in the pressing process is 10mm. The binder used in the granulation process is a 5wt% PVA aqueous solution, and the binder is used in an amount of 8% by volume of the dry powder.
In step (5) of some preferred embodiments of the present application, the sintering means: firstly, preserving heat for 2 hours at 500 ℃, then raising the temperature to 1200 ℃ at the speed of 5 ℃/min, raising the temperature of the blank to 1325-1400 ℃ at the speed of 2 ℃/min, and preserving heat for 4 hours; cooling to 1200 ℃ at a speed of 2 ℃/min after the heat preservation is finished, cooling to 500 ℃ at a speed of 5 ℃/min, and cooling to room temperature along with the furnace. The machining refers to machining the high-entropy ceramic block into a sample with the size of 5mm high and the diameter of 8.5 mm.
The application is based on the fact that traditional perovskite has high dielectric constant, and attempts to introduce the concept of high entropy into the exploration of high dielectric microwave dielectric ceramics are further described below.
Example 1
Step (1): znO and CaCO are mixed 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 、Al 2 O 3 According to the target product (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 (x=0, i.e. the formula (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )TiO 3 ) Wherein Zn, ba, ca,The molar ratio of the Sr to the La is 1:1:1:1:2, the powder is mixed and placed in a planetary ball milling tank, agate balls are used as grinding media, ethanol is used as dispersing agent for ball milling, and the ball-material ratio is 6:1. The rotating speed of the planetary ball mill is 300r/min, the alternate running time is 30min, the alternate running time is 10min, and the planetary ball mill is operated for 13 times alternately;
step (2): placing the mixed slurry obtained by ball milling in an electrothermal blowing drying oven, and drying for 10 hours at 80 ℃;
step (3): placing the dried powder in a muffle furnace, heating to 1000 ℃ at a heating rate of 5 ℃/min for presintering, preserving heat for 2 hours, and cooling to room temperature along with the furnace;
step (4): placing the presintered powder into a planetary ball mill, running at a speed of 300r/min for 8h, wherein the alternate running time is 30min, the alternate running interval is 10min, and then drying at 80 ℃ for 10h to obtain dry powder;
step (5): placing the dry powder into an agate mortar, and dropwise adding 5wt% of PVA water solution while grinding until the powder and PVA are uniformly mixed, wherein the dosage of the adhesive is 8% of the volume of the dry powder;
step (6): placing the treated high-entropy ceramic powder into a die with the diameter of 10mm, applying pressure to 150Mpa by utilizing a hydraulic press, and maintaining the pressure for 3min; then placing the ceramic green body in a cold isostatic press, boosting the pressure to 250MPa at 50MPa/min, maintaining the pressure for 15min, and reducing the pressure to 0MPa at 50MPa/min to obtain the ceramic green body;
step (7): placing the ceramic green body in a muffle furnace, heating to 500 ℃ at a speed of 2 ℃/min, preserving heat for 2 hours for discharging glue, heating to 1200 ℃ at a speed of 5 ℃/min, heating to 1400 ℃ at a speed of 2 ℃/min, and preserving heat for 4 hours; cooling to 1200 ℃ at a speed of 2 ℃/min after the heat preservation is finished, cooling to 500 ℃ at a speed of 5 ℃/min, and cooling with a furnace. The ceramic blocks were each sanded and cleaned with 200-1200 mesh sandpaper (first 200 mesh sandpaper, then 800 mesh sandpaper, and finally 1200 mesh sandpaper). Finally, the high-entropy microwave dielectric ceramic with the high dielectric aluminum doped perovskite structure is obtained and is marked as (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )TiO 3 (labeled ZBCSL1400 ℃ in fig. 1).
The high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure prepared in the embodiment has a dielectric constant of 84.2, a dielectric loss of 0.0018 (4.14 GHz) and a resonant frequency temperature coefficient of 217 ppm/DEG C.
Example 2
Step (1): znO and CaCO are mixed 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 、Al 2 O 3 According to the target product (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 The stoichiometric ratio of (x=0.02) is used for proportioning, wherein the molar ratio of Zn, ba, ca, sr, la metal elements is 1:1:1:2, powder is mixed and placed in a planetary ball milling tank, agate balls are used as grinding media, ethanol is used as dispersing agent for ball milling, and the ball-material ratio is 6:1. The rotating speed of the planetary ball mill is 300r/min, the alternate running time is 30min, the alternate running time is 10min, and the planetary ball mill is operated for 13 times alternately;
step (2) to step (7) are the same as in example 1. The obtained high-dielectric aluminum-doped perovskite structure high-entropy microwave dielectric ceramic is named as (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 0.98 Al 0.02 O 3 。
The high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure prepared in the embodiment has a dielectric constant of 90.82, a dielectric loss of 0.0013 (@3.89 GHz) and a resonant frequency temperature coefficient of 199 ppm/DEG C.
Example 3
Step (1): znO and CaCO are mixed 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 、Al 2 O 3 According to the target product (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 Stoichiometric ratio of (x=0.04), wherein Zn, ba, ca, sr, la metals are compoundedThe mol ratio of the elements is 1:1:1:1:2, the powder is mixed and placed in a planetary ball milling tank, agate balls are used as grinding media, ethanol is used as dispersing agent for ball milling, and the ball-material ratio is 6:1. The rotating speed of the planetary ball mill is 300r/min, the alternate running time is 30min, the alternate running time is 10min, and the planetary ball mill is operated for 13 times alternately;
step (2) to step (7) are the same as in example 1. The obtained high-dielectric aluminum-doped perovskite structure high-entropy microwave dielectric ceramic is named as (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 0.96 Al 0.04 O 3 。
The high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure prepared in the embodiment has a dielectric constant of 85.018, a dielectric loss of 0.0013 (4.02 GHz) and a resonant frequency temperature coefficient of 196 ppm/DEG C.
Example 4
Step (1): znO and CaCO are mixed 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 、Al 2 O 3 According to the target product (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 The stoichiometric ratio of (x=0.06) is used for proportioning, wherein the molar ratio of Zn, ba, ca, sr, la metal elements is 1:1:1:2, powder is mixed and placed in a planetary ball milling tank, agate balls are used as grinding media, ethanol is used as dispersing agent for ball milling, and the ball-material ratio is 6:1. The rotating speed of the planetary ball mill is 300r/min, the alternate running time is 30min, the alternate running time is 10min, and the planetary ball mill is operated for 13 times alternately;
step (2) to step (7) are the same as in example 1. The obtained high-dielectric aluminum-doped perovskite structure high-entropy microwave dielectric ceramic is named as (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 0.94 Al 0.06 O 3 。
The high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure prepared in the embodiment has a dielectric constant of 78.42, a dielectric loss of 0.0014 (4.2 GHz) and a resonant frequency temperature coefficient of 194 ppm/DEG C.
Example 5
Step (1): znO and CaCO are mixed 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 、Al 2 O 3 According to the target product (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 The stoichiometric ratio of (x=0.08) is used for proportioning, wherein the molar ratio of Zn, ba, ca, sr, la metal elements is 1:1:1:2, powder is mixed and placed in a planetary ball milling tank, agate balls are used as grinding media, ethanol is used as dispersing agent for ball milling, and the ball-material ratio is 6:1. The rotating speed of the planetary ball mill is 300r/min, the alternate running time is 30min, the alternate running time is 10min, and the planetary ball mill is operated for 13 times alternately;
step (2) to step (7) are the same as in example 1. The obtained high-dielectric aluminum-doped perovskite structure high-entropy microwave dielectric ceramic is named as (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 0.92 Al 0.08 O 3 。
The high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure prepared in the embodiment has a dielectric constant of 74.46, a dielectric loss of 0.0013 (4.31 GHz) and a resonant frequency temperature coefficient of 184 ppm/DEG C.
Example 6
Step (1): znO and CaCO are mixed 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 、Al 2 O 3 According to the target product (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 The stoichiometric ratio of (x=0.1) is used for proportioning, wherein the molar ratio of Zn, ba, ca, sr, la metal elements is 1:1:1:2, powder is mixed and placed in a planetary ball milling tank, agate balls are used as grinding media, ethanol is used as dispersing agent for ball milling, and the ball-material ratio is 6:1. The rotating speed of the planetary ball mill is 300r/min, the alternating running time is 30min, and the planetary ball mill alternately runs in the forward and reverse directions at intervalsThe stop time of the alternate operation interval is 10min, and the alternate operation is performed for 13 times;
step (2) to step (7) are the same as in example 1. The obtained high-dielectric aluminum-doped perovskite structure high-entropy microwave dielectric ceramic is named as (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 0.9 Al 0.1 O 3 。
The high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure prepared in the embodiment has a dielectric constant of 75.26, a dielectric loss of 0.0011 (4.25 GHz) and a resonant frequency temperature coefficient of 175 ppm/DEG C.
FIG. 1 is an X-ray diffraction diagram of the high-entropy microwave dielectric ceramic with perovskite structure with high dielectric aluminum doping prepared in examples 1-6 of the application, wherein x=0, 0.02, 0.04, 0.06, 0.08, 0.1; as can be seen from fig. 1, all the synthesized high-entropy ceramics have a perovskite structure, and no second phase is generated.
FIG. 2 shows the SEM microstructure of the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure prepared in examples 1-6 of the present application; as can be seen from FIG. 2, the synthesized high-entropy ceramic has clear grain boundaries, uniform size and high compactness.
Fig. 3 is a histogram of grain size frequency distribution of the high-entropy microwave dielectric ceramics with high dielectric aluminum-doped perovskite structure prepared in examples 1-6 according to the present application, and it can be seen from fig. 3 that the grain size of the synthesized high-entropy ceramic gradually decreases with increasing Al content.
Fig. 4 is a dielectric constant diagram of the high-entropy microwave dielectric ceramics with the perovskite structure with the high-dielectric aluminum doping type prepared in the embodiments 1-6, and as can be seen from fig. 4, the dielectric constants of the synthesized high-entropy ceramics are all larger than 70.
Fig. 5 is a Qf diagram of the high-entropy microwave dielectric ceramic with high dielectric aluminum-doped perovskite structure prepared in examples 1-6 according to the present application, and it can be seen from fig. 5 that the dielectric loss of the synthesized high-entropy ceramic gradually decreases with the increase of Al content.
Fig. 6 is a graph of the temperature coefficient of resonance frequency of the high-entropy microwave dielectric ceramic with perovskite structure with high dielectric aluminum doping prepared in examples 1-6 according to the present application, and it can be seen from fig. 6 that the temperature coefficient of resonance frequency gradually decreases with increasing Al content.
As can be illustrated by the above embodiments and the accompanying drawings, the dielectric constants of the high-entropy microwave dielectric ceramics with the high-dielectric aluminum-doped perovskite structure synthesized by the method are all larger than 70, the high-entropy microwave dielectric ceramics belong to the range of the high-dielectric microwave dielectric ceramics, have medium quality factors, and compared with the traditional perovskite, the temperature coefficient of the resonant frequency is greatly reduced, and still have room for improvement, so that the high-entropy microwave dielectric ceramics are expected to be applied to mobile terminals, communication base stations and the like.
Example 7
Step (1) to step (6) are the same as in example 1.
Step (7): placing the ceramic green body in a muffle furnace, heating to 500 ℃ at a speed of 2 ℃/min, preserving heat for 2 hours for discharging glue, heating to 1200 ℃ at a speed of 5 ℃/min, heating to 1350 ℃ at a speed of 2 ℃/min, and preserving heat for 6 hours; cooling to 1200 ℃ at a speed of 2 ℃/min after the heat preservation is finished, cooling to 500 ℃ at a speed of 5 ℃/min, and cooling with a furnace. Coarse grinding is carried out by using 200-mesh sand paper, fine grinding is carried out by using 800-mesh sand paper, and finally polishing is carried out by using 1200-mesh sand paper, and then cleaning is carried out. The finally obtained high-dielectric aluminum-doped perovskite structure high-entropy microwave dielectric ceramic is named as (Zn) 1/6 Ba 1/6 Ca 1/6 Sr 1/ 6 La 1/3 )TiO 3 。
The high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure prepared in the embodiment has a dielectric constant of 78.937, a dielectric loss of 0.0024 (@ 4.199 GHz) and a resonant frequency temperature coefficient of 229 ppm/DEG C.
Comparative example 1
As in example 6, the difference is that Al 2 O 3 Replaced with NiO.
The high-entropy microwave dielectric ceramic with the nickel-doped perovskite structure prepared in the comparative example has a dielectric constant of 68.884, a dielectric loss of 0.0018 (@ 4.527 GHz) and a resonant frequency temperature coefficient of 189 ppm/DEG C.
Comparative example 2
As in example 6, the difference is that Al 2 O 3 Replaced by Co 3 O 4 。
The high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure prepared in the comparative example has a dielectric constant of 73.077, a dielectric loss of 0.0019 (4.389 GHz) and a resonant frequency temperature coefficient of 217 ppm/DEG C.
The present application is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present application are intended to be included in the scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.
Claims (8)
1. The high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure is characterized by having a chemical general formula (Zn 1/6 Ba 1/6 Ca 1/6 Sr 1/6 La 1/3 )Ti 1-x Al x O 3 Wherein: x=0-0.1.
2. A method for preparing the high-entropy microwave dielectric ceramic with the high dielectric aluminum-doped perovskite structure according to claim 1, which comprises the following steps:
weighing ZnO and CaCO as raw materials according to stoichiometric ratio 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 And Al 2 O 3 Adding a solvent, and performing ball milling to obtain mixed slurry;
drying the mixed slurry, presintering the obtained powder, performing secondary ball milling, and continuing drying to obtain dry powder;
granulating the dry powder, and then placing the granulated powder into a hydraulic press and a cold isostatic press to be pressed into ceramic green bodies;
sintering the ceramic green body in a protective gas atmosphere to obtain the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure.
3. The method for preparing the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure according to claim 2, wherein the raw materials ZnO and Ca are as followsCO 3 、BaCO 3 、SrO、La 2 O 3 、TiO 2 And Al 2 O 3 The purity of (2) is more than 99.5%.
4. The method for preparing the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure according to claim 2, wherein the process of ball milling is performed at intervals in forward and reverse directions, wherein the ball-material ratio is 6:1, the ball milling time is 8h, the rotating speed is 300r/min, the alternating operation time is 30min, and the interval is stopped for 10min.
5. The method for preparing the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure according to claim 2, wherein the pre-sintering is performed at 1000 ℃ for 2 hours.
6. The method for preparing the high-entropy microwave dielectric ceramic with the high-dielectric aluminum-doped perovskite structure according to claim 2, wherein the parameters set by the hydraulic press are as follows: the pressure is 150-200MPa, and the pressure holding time is 3-5min; the parameters set by the cold isostatic press are as follows: the pressure is 250-300MPa, and the pressure holding time is 15-20min.
7. The method for preparing high-entropy microwave dielectric ceramic with high dielectric aluminum doped perovskite structure according to claim 2, wherein the binder used in the granulating process is 5wt% PVA aqueous solution, and the binder amount is 8% of the dry powder volume.
8. The method for preparing high-entropy microwave dielectric ceramic with high dielectric aluminum doped perovskite structure according to claim 2, wherein the sintering is to keep the temperature at 1325-1400 ℃ for 4h.
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| CN117447197B (en) * | 2023-12-25 | 2024-02-27 | 上海南极星高科技股份有限公司 | Preparation method of high-entropy pseudobrookite titanate ceramic |
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