A high dielectric constant and low loss ferroelectric capacitor

Abstract

The present invention discloses a high dielectric constant and low loss ferroelectric capacitor and a preparation method thereof, relating to the technical field of ceramic capacitors. The preparation raw materials include a dielectric ceramic composition, and the dielectric ceramic composition contains at least one of (BimAnBpCq)FeO3 and Bi(FemDnEpFq)O3, wherein A, B, and C are independently selected from one or more of Nd, La, Sm, Eu, Er, Dy, Al, and B; D, E, and F are independently selected from one or more of Ru, Sc, Al, Ga, Y, and In; m + n + p + q = 1, 0 ≤ m ≤ 1, 0 ≤ n ≤ 1, 0 ≤ p ≤ 1, 0 ≤ q ≤ 1. The high dielectric constant and low loss ferroelectric capacitor disclosed by the present invention has a high dielectric constant and a low dielectric loss.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic capacitors, and particularly relates to a high-dielectric-constant and low-loss ferroelectric capacitor based on entropy design. Background Art

[0002] As one of the most widely used passive electronic components, ceramic capacitors have many excellent characteristics such as large specific capacitance, good resistance to damp heat, small dielectric loss, small series equivalent resistance, and a wide selection range of capacitance-temperature coefficients compared with other types of capacitors. They are widely used in high-power electronics, electrical appliances and other fields, such as energy storage, inversion, filtering, bypass, coupling and other fields in hybrid electric vehicles, aerospace, oil drilling, national defense, and sustainable distributed energy power systems. In recent years, with the growth of consumer markets such as smart phones, tablet computers, and 3D TVs, the demand for ceramic capacitors has been increasing year by year.

[0003] Ferroelectric ceramic materials have a very high dielectric constant and are a very important type of dielectric material, which are widely used in the preparation of ceramic capacitors in the electronics industry. Bismuth ferrite (BiFeO 3 ) As a common ferroelectric ceramic material, due to its room-temperature multiferroicity (ferroelectric Curie temperature is 1103K, antiferromagnetic Néel temperature is 643K), its strong ferroelectricity makes it a promising dielectric. However, pure bismuth ferrite is not easy to synthesize, and although bismuth ferrite as a strong ferroelectric has a large polarization, its saturated polarization characteristics result in a not very high dielectric constant, and its large switching hysteresis leads to large losses. In addition, the leakage current caused by oxygen vacancies due to the variable valence of iron ions and bismuth vacancies caused by the volatilization of bismuth atoms hinders the practical device application of bismuth ferrite.

[0004] To solve the above problems, the Chinese invention patent with the authorization announcement number CN103936408B discloses a barium and chromium co-doped bismuth ferrite ceramic with room-temperature multiferroicity and its preparation method, belonging to the field of materials science. The chemical molecular formula of the ceramic material is: Bi 1-x Ba x Fe 1-y Cr y O 3 , 0 < x ≤ 0.2, 0 < y ≤ 0.1. Mix the raw materials BaCO 3 , Bi 2 O 3 , Cr 2 O 3 and Fe 2 O 3Mix and ball-mill according to the stoichiometric ratio, calcine at 800 - 840 °C for 2 hours after drying; ball-mill the powder again, add polyvinyl alcohol solution after drying, grind thoroughly and then press into flakes under a pressure of 472 MPa using a tablet press; degrease at 560 °C for 2 h and calcine at 890 - 920 °C for 2 hours to form ceramics. The multiferroic ceramics prepared by this invention have excellent ferroelectric and ferromagnetic properties at room temperature. However, its dielectric constant needs to be further improved and the loss needs to be further reduced. Summary of the Invention

[0005] The purpose of this invention is to provide a ferroelectric capacitor with high dielectric constant and low dielectric loss to overcome the deficiencies of the prior art.

[0006] To achieve the above purpose, the technical solution adopted by this invention is: a ferroelectric capacitor with high dielectric constant and low loss, whose preparation raw materials include a dielectric ceramic composition, and the dielectric ceramic composition contains at least one of (Bi m A n B p C q )FeO 3 , Bi(Fe m D n E p F q )O 3 , where A, B, and C are independently selected from one or more of Nd, La, Sm, Eu, Er, Dy, Al, and B; D, E, and F are independently selected from one or more of Ru, Sc, Al, Ga, Y, and In; m + n + p + q = 1, 0 ≤ m ≤ 1, 0 ≤ n ≤ 1, 0 ≤ p ≤ 1, 0 ≤ q ≤ 1.

[0007] Another purpose of this invention is to provide a preparation method for the ferroelectric capacitor with high dielectric constant and low loss, including the following steps:

[0008] Step S1: Prepare dielectric ceramics by the solid-state reaction method: Mix oxide or carbonate powders containing Bi, A, B, C, D, E, F, and Fe respectively according to the stoichiometric ratio, ball-mill after mixing, then dry the sample and calcine, naturally cool to room temperature, and then ball-mill and screen the calcined powder again to obtain dielectric ceramic powder;

[0009] Step S2: Prepare ceramic wafers: Add a binder to the dielectric ceramic powder prepared in Step S1, mix evenly and press into a disc, then sinter at a certain temperature for 1 - 3 h, and naturally cool to room temperature to obtain ceramic wafers;

[0010] Step S3: Preparation of ferroelectric capacitor: Apply silver on the upper and lower surfaces of the ceramic sheet made in Step S2, and sinter at 780 - 820 °C for 13 - 20 min under the protection of inert gas to form a ferroelectric capacitor.

[0011] Preferably, in Step S1, the calcination temperature is 800 - 850 °C, and the calcination time is 3 - 5 h.

[0012] Preferably, in Step S1, an appropriate amount of deionized water and zirconia beads are added during the ball milling process, and the ball milling time is 2 - 7 h.

[0013] Preferably, in Step S1, the sieving is through a sieve with 800 - 1500 meshes.

[0014] Preferably, in Step S2, the mass ratio of the dielectric ceramic powder to the binder is 100:(0.1 - 0.3).

[0015] Preferably, in Step S2, the binder is PVA 098 - 05 binder.

[0016] Preferably, in Step S2, the certain temperature is 1000 - 1150 °C.

[0017] Preferably, in Step S3, the inert gas is any one of nitrogen, helium, neon, and argon.

[0018] Preferably, in Step S3, the thickness of the silver coating is 0.1 - 0.2 μm; the thickness of the ceramic sheet is 0.6 - 0.8 μm.

[0019] Due to the application of the above technical solutions, the present invention has the following beneficial effects: By reasonably selecting the composition and formula of the high-entropy bismuth ferrite component in the dielectric ceramic composition, the present invention not only ensures the valence balance but also increases the local heterogeneity; through the multi-component high-entropy design at the Bi site or Fe site, the purpose of improving the local disorder degree, reducing the remanent polarization, enhancing the polarization, and reducing the material loss is achieved. Through the reasonable selection of the preparation process parameters and the combined action with the composition formula, the ferroelectric capacitor made has a high dielectric constant and a low dielectric loss. Description of the Drawings

[0020] Figure 1 It is a cross-sectional scanning electron microscope image of Embodiment 1 of the present invention. Detailed Description of the Invention

[0021] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations.

[0022] Embodiment 1

[0023] Figure 1 As shown, a high dielectric constant and low loss ferroelectric capacitor, the preparation raw materials of which include a dielectric ceramic composition, and the dielectric ceramic composition includes (Bi 0.5 La 0.2 Sm 0.2 Nd 0.1 )FeO 3 .

[0024] A preparation method of the high dielectric constant and low loss ferroelectric capacitor includes the following steps:

[0025] Step S1: Prepare the dielectric ceramic by the solid-phase reaction method: Mix bismuth oxide, lanthanum oxide, samarium oxide, neodymium oxide, and iron oxide powders according to the stoichiometric ratio, ball mill after mixing, then dry the sample and calcine it, naturally cool it to room temperature, and then ball mill and screen the calcined powder again to obtain the dielectric ceramic powder;

[0026] Step S2: Prepare the ceramic sheet: Add a binder to the dielectric ceramic powder prepared in Step S1, mix evenly and press it into a disc, then sinter it at a certain temperature for 1 h, and naturally cool it to room temperature to obtain the ceramic sheet;

[0027] Step S3: Prepare the ferroelectric capacitor: Coat silver on the upper and lower surfaces of the ceramic sheet prepared in Step S2 respectively, and sinter it at 780 °C for 13 min under the protection of an inert gas to form the ferroelectric capacitor.

[0028] The calcination temperature in Step S1 is 800 °C, and the calcination time is 3 h; In the ball milling process in Step S1, an appropriate amount of deionized water and zirconia beads are added, and the ball milling time is 2 h; The sieving in Step S1 is through an 800-mesh sieve.

[0029] The mass ratio of the dielectric ceramic powder to the binder in Step S2 is 100:0.1; The binder in Step S2 is PVA 098-05 binder; The certain temperature in Step S2 is 1000 °C; The inert gas in Step S3 is nitrogen; The thickness of the silver coating in Step S3 is 0.1 μm; The thickness of the ceramic sheet is 0.6 μm.

[0030] Example 2

[0031] A high dielectric constant and low loss ferroelectric capacitor, the preparation raw materials of which include a dielectric ceramic composition, and the dielectric ceramic composition contains Bi(Fe 0.25 Sc 0.25 Ru 0.1 Al 0.4 )O 3 .

[0032] A preparation method of the high dielectric constant and low loss ferroelectric capacitor includes the following steps:

[0033] Step S1: Prepare the dielectric ceramic by the solid-state reaction method: Mix bismuth oxide, scandium oxide, ruthenium oxide, aluminum oxide, and iron oxide powders according to the stoichiometric ratio. After mixing, ball-mill the mixture, then dry the sample and calcine it. Naturally cool it to room temperature, and then ball-mill and screen the calcined powder again to obtain the dielectric ceramic powder;

[0034] Step S2: Prepare the ceramic sheet: Add a binder to the dielectric ceramic powder prepared in Step S1, mix evenly and press it into a disc. Then sinter it at a certain temperature for 1.5 h, and naturally cool it to room temperature to obtain the ceramic sheet;

[0035] Step S3: Prepare the ferroelectric capacitor: Brush silver on the upper and lower surfaces of the ceramic sheet prepared in Step S2, and sinter it at 790 °C for 15 min under the protection of inert gas to form the ferroelectric capacitor.

[0036] In Step S1, the calcination temperature is 820 °C and the calcination time is 3.5 h; in the ball-milling process in Step S1, an appropriate amount of deionized water and zirconia beads are added, and the ball-milling time is 4 h; the sieving in Step S1 is through a 1000-mesh sieve.

[0037] In Step S2, the mass ratio of the dielectric ceramic powder to the binder is 100:0.15; the binder in Step S2 is PVA 098-05 binder; the certain temperature in Step S2 is 1050 °C; the inert gas in Step S3 is helium; the thickness of the silver brushing in Step S3 is 0.12 μm; the thickness of the ceramic sheet is 0.65 μm.

[0038] Example 3

[0039] A high dielectric constant and low loss ferroelectric capacitor, the preparation raw materials of which include a dielectric ceramic composition, and the dielectric ceramic composition contains (Bi 0.5 Er 0.1 Dy 0.3 B 0.1 )FeO 3 .

[0040] A preparation method of the high dielectric constant and low loss ferroelectric capacitor includes the following steps:

[0041] Step S1: Prepare the dielectric ceramic by the solid-state reaction method: Mix bismuth oxide, erbium oxide, dysprosium oxide, boron oxide, and iron oxide powders according to the stoichiometric ratio. After mixing, ball-mill the mixture, then dry the sample and calcine it. Naturally cool it to room temperature, and then ball-mill and screen the calcined powder again to obtain the dielectric ceramic powder;

[0042] Step S2: Prepare the ceramic sheet: Add a binder to the dielectric ceramic powder prepared in Step S1, mix evenly, press it into a disc, then sinter it at a certain temperature for 2 h, and naturally cool it to room temperature to obtain the ceramic sheet;

[0043] Step S3: Prepare the ferroelectric capacitor: Brush silver on the upper and lower surfaces of the ceramic sheet prepared in Step S2 respectively, and sinter it at 800 °C for 17 min under the protection of inert gas to form the ferroelectric capacitor.

[0044] The calcination temperature in Step S1 is 830 °C, and the calcination time is 4 h; In the ball milling process in Step S1, an appropriate amount of deionized water and zirconia beads are added, and the ball milling time is 4 h; The sieving in Step S1 is through a 1300-mesh sieve.

[0045] The mass ratio of the dielectric ceramic powder to the binder in Step S2 is 100:0.2; The binder in Step S2 is PVA 098-05 binder; The certain temperature in Step S2 is 1100 °C; The inert gas in Step S3 is neon; The thickness of the silver coating in Step S3 is 0.15 μm; The thickness of the ceramic sheet is 0.7 μm.

[0046] Example 4

[0047] A high dielectric constant and low loss ferroelectric capacitor, the preparation raw materials of which include a dielectric ceramic composition, and the dielectric ceramic composition contains Bi(Fe 0.4 Ga 0.25 Y 0.15 In 0.2 )O 3 .

[0048] A preparation method of the high dielectric constant and low loss ferroelectric capacitor comprises the following steps:

[0049] Step S1: Prepare the dielectric ceramic by the solid-phase reaction method: Mix bismuth oxide, iron oxide, gallium oxide, yttrium oxide, and indium oxide powders according to the stoichiometric ratio, ball mill the mixture after mixing, then dry the sample and calcine it, naturally cool it to room temperature, and then ball mill and sieve the calcined powder again to obtain the dielectric ceramic powder;

[0050] Step S2: Prepare the ceramic sheet: Add a binder to the dielectric ceramic powder prepared in Step S1, mix evenly, press it into a disc, then sinter it at a certain temperature for 2.5 h, and naturally cool it to room temperature to obtain the ceramic sheet;

[0051] Step S3: Prepare the ferroelectric capacitor: Brush silver on the upper and lower surfaces of the ceramic sheet prepared in Step S2 respectively, and sinter it at 810 °C for 19 min under the protection of inert gas to form the ferroelectric capacitor.

[0052] In step S1, the calcination temperature is 840 °C and the calcination time is 4.5 h; in step S1, an appropriate amount of deionized water and zirconia beads are added during the ball milling process, and the ball milling time is 6 h; in step S1, the sieving is through a 1400-mesh sieve; in step S2, the mass ratio of the dielectric ceramic powder to the binder is 100:0.25; in step S2, the binder is PVA 098-05 binder; in step S2, the certain temperature is 1130 °C; in step S3, the inert gas is argon; in step S3, the thickness of the silver coating is 0.18 μm; the thickness of the ceramic sheet is 0.75 μm.

[0053] Example Five

[0054] A high dielectric constant and low loss ferroelectric capacitor, the preparation raw materials of which include a dielectric ceramic composition, and the dielectric ceramic composition contains (Bi 0.6 Er 0.1 Nd 0.2 Al 0.1 )FeO 3 .

[0055] A preparation method of the high dielectric constant and low loss ferroelectric capacitor includes the following steps:

[0056] Step S1: Prepare a dielectric ceramic by the solid-phase reaction method: Mix bismuth oxide, erbium oxide, neodymium oxide, aluminum oxide, and iron oxide powders according to the stoichiometric ratio, ball mill the mixture after mixing, then dry the sample and calcine it, naturally cool it to room temperature, and then ball mill and sieve the calcined powder again to obtain a dielectric ceramic powder;

[0057] Step S2: Prepare a ceramic sheet: Add a binder to the dielectric ceramic powder prepared in step S1, mix it evenly and press it into a disc, then sinter it at a certain temperature for 3 h, and naturally cool it to room temperature to obtain a ceramic sheet;

[0058] Step S3: Prepare a ferroelectric capacitor: Coat silver on the upper and lower surfaces of the ceramic sheet prepared in step S2 respectively, and sinter it at 820 °C for 20 min under the protection of an inert gas to form a ferroelectric capacitor.

[0059] In step S1, the calcination temperature is 850 °C and the calcination time is 5 h; in step S1, an appropriate amount of deionized water and zirconia beads are added during the ball milling process, and the ball milling time is 7 h; in step S1, the sieving is through a 1500-mesh sieve; in step S2, the mass ratio of the dielectric ceramic powder to the binder is 100:0.3; in step S2, the binder is PVA 098-05 binder; in step S2, the certain temperature is 1150 °C; in step S3, the inert gas is argon; in step S3, the thickness of the silver coating is 0.2 μm; the thickness of the ceramic sheet is 0.8 μm.

[0060] Comparative Example 1

[0061] A high dielectric constant, low loss ferroelectric capacitor and its preparation method are basically the same as those in Example 1, except that BiFeO 3 is used to replace (Bi 0.5 La 0.2 Sm 0.2 Nd 0.1 )FeO 3 .

[0062] In order to further illustrate the beneficial technical effects of the high dielectric constant, low loss ferroelectric capacitors involved in the embodiments of the present invention, the high dielectric constant, low loss ferroelectric capacitors involved in Examples 1-5 and Comparative Examples 1-2 are tested for relevant dielectric properties (dielectric constant, loss) at a frequency of 1 kHz under an LCR bridge according to the conventional method in the industry, and the hysteresis loop test is carried out under a Radiant ferroelectric meter to extract the maximum polarization (100 kV cm -1 ), and the remanent polarization. The results are shown in Table 1.

[0063] Table 1

[0064]

[0065]

[0066] It can be seen from the data in Table 1 that the high dielectric constant, low loss ferroelectric capacitors involved in the embodiments of the present invention have higher dielectric constants and lower dielectric losses than the products of the comparative examples.

[0067] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It should not be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A high dielectric constant, low loss ferroelectric capacitor, characterized in that: The raw materials for its preparation include a dielectric ceramic composition, wherein the dielectric ceramic composition is composed of (Bi m A n B p C q )FeO3、Bi(Fe m D n E p F q )O3, wherein A is selected from any one of La and Er; B is selected from any one of Sm, Dy, and Nd; C is selected from any one of Nd, B, and Al; D is selected from any one of Sc and Ga; E is selected from any one of Ru and Y; F is selected from any one of Al and In; m+n+p+q=1, 0.25≤m≤0.6, 0.1≤n≤0.25, 0.1≤p≤0.3, 0.1≤q≤0.

4.

2. A method for preparing a high dielectric constant, low loss ferroelectric capacitor according to claim 1, characterized in that: The steps include: Step S1, preparing dielectric ceramics by a solid phase reaction method: mixing oxide or carbonate powders containing Bi, A, B, C, D, E, F, and Fe respectively according to a stoichiometric ratio, ball milling after mixing, then drying and calcining the sample, cooling it naturally to room temperature, and then ball milling and sieving the calcined powder again to obtain dielectric ceramic powder; Step S2, preparing a ceramic sheet: adding a binder to the dielectric ceramic powder prepared in step S1, mixing well and pressing into a disc, then sintering at a certain temperature for 1-3 hours, and naturally cooling to room temperature to obtain a ceramic sheet; Step S3, preparation of ferroelectric capacitor: silver is applied to the upper and lower surfaces of the ceramic sheet prepared in step S2, respectively, and sintered at 780-820° C. for 13-20 min under the protection of an inert atmosphere to form a ferroelectric capacitor.

3. The method for preparing a high dielectric constant, low loss ferroelectric capacitor according to claim 2, characterized in that: The calcination temperature in step S1 is 800-850° C., and the calcination time is 3-5 hours.

4. The method for preparing a high dielectric constant, low loss ferroelectric capacitor according to claim 2, characterized in that: In the ball milling process in step S1, an appropriate amount of deionized water and zirconium oxide beads are added, and the ball milling time is 2-7 hours; the sieving in step S1 is sieving through a 800-1500 mesh sieve.

5. The method for preparing a high dielectric constant, low loss ferroelectric capacitor according to claim 2, characterized in that: The mass ratio of the dielectric ceramic powder to the adhesive in step S2 is 100:(0.1-0.3).

6. The method for preparing a high dielectric constant, low loss ferroelectric capacitor according to claim 2, characterized in that: The adhesive in step S2 is PVA 098-05 adhesive.

7. The method for preparing a high dielectric constant, low loss ferroelectric capacitor according to claim 2, characterized in that: The certain temperature in step S2 is 1000-1150°C.

8. The method for preparing a high dielectric constant, low loss ferroelectric capacitor according to claim 2, characterized in that: The inert atmosphere in step S3 is any one of nitrogen, helium, neon and argon.

9. The method for preparing a high dielectric constant, low loss ferroelectric capacitor according to claim 2, characterized in that: The thickness of the silver coating in step S3 is 0.1-0.2 μm; the thickness of the ceramic sheet is 0.6-0.8 μm.

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