Method for manufacturing a capacitor element having a dielectric ceramic film, a slip for manufacturing a dielectric ceramic film, and a capacitor element having a dielectric ceramic film

Abstract

The present invention relates to a method (1) for manufacturing a capacitor element having a dielectric ceramic film (9), a slip for manufacturing the dielectric ceramic film (9), and a capacitor element having the dielectric ceramic film (9). In a slip preparation step, a slip is prepared from a ceramic powder and an organic medium. For the ceramic powder, at least oxides Bi2O3, TiO2, ZrO2, and Al2O3, and at least carbonates Na2CO3, BaCO3, and CaCO3, or precursors of said oxides and / or carbonates are used in a stoichiometric ratio in order to synthesize (1 - x)[0.8(0.94Na 0.5 Bi 0.5 TiO3·0.06BaTiO3)·0.2CaZrO3]·xBiAlO3 (where x represents 0.5, 1, 1.5, 2, 4, and 8 mol%). The slip is cast as a film in a film casting step, in an electrode application step, an electrode (10) is applied to the cast film, and in a sintering step, the cast film provided with the electrode (10) is sintered at an elevated temperature. The organic medium contains at least one liquid solvent containing at least 1-butanol, at least one plasticizer containing tributyl acetyl citrate, at least one dispersant, and at least one binder.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a capacitor (capacitor) element having a dielectric ceramic film. In the step of preparing a slip, the slip is produced from ceramic powder and an organic medium. Here, for the ceramic powder, (1 - x)[0.8(0.94Na 0.5 Bi 0.5 TiO3·0.06BaTiO3)·0.2CaZrO3]·xBiAlO3 (where x = 0.5, 1, 1.5, 2, 4, and 8 mol%) is synthesized. To do this, at least the oxides Bi2O3, TiO 2、 ZrO2, and Al2O3, and at least the carbonates Na2CO3, BaCO3, and CaCO3, or in any case, the precursors of the oxides and / or carbonates are used in a stoichiometric ratio with respect to the ceramic powder. Here, in the film casting step, the slip is cast as a film, in the electrode application step, an electrode is applied to the cast film, and in the sintering step, the cast film provided with the electrode is sintered at an elevated temperature to remove the organic medium from the structure and convert the cast film into a dielectric ceramic film. Here, the dielectric ceramic film contains at least (1 - x)[0.8(0.94Na 0.5 Bi 0.5 TiO30.06BaTiO3)·0.2CaZrO3]·xBiAlO3, where x = 0.5, 1, 1.5, 2, 4, and 8 mol%.

[0002] The present invention also relates to a slip for manufacturing a dielectric ceramic film, the slip containing a ceramic powder and an organic medium, the ceramic powder containing at least the oxides Bi2O3, TiO2, ZrO ) and Al2O3, and at least the carbonates Na2CO3, BaCO3, and CaCO3, or the respective precursors of the oxides and / or carbonates.

[0003] The present invention also relates to a dielectric ceramic film containing at least (1 - x)[0.8(0.94Na 0.5 Bi 0.5 TiO3·0.06BaTiO3)·0.2CaZrO3]·xBiAlO3, where x = 0.5, 1, 1.5, 2, 4, and 8 mol%, wherein the dielectric ceramic film has electrodes, the ceramic film is manufactured from a slip, and the slip contains ceramic powder and an organic medium.

[0004] Capacitors are passive electronic components and are used in almost all electronic devices. Capacitors are used not only in the aerospace and automotive industries but also in portable household appliances. A capacitor is composed of at least one capacitor element and other connection parts and lines necessary for contact with the capacitor element. The capacitor element has a dielectric in the form of a dielectric film and electrodes disposed on the dielectric film. A film is any thin layer having dimensions suitable for shielding the electrodes of the capacitor element as a dielectric component, and with the help of this capacitor element, charge and associated energy can be statically stored in the electric field of the capacitor. As part of an electrical circuit, the capacitor element needs to have as stable characteristics as possible over a wide temperature range and high applied voltages, and at the same time, there is a need for capacitor elements with smaller dimensions having constant or improved performance. Higher requirements are also imposed on the reliability and durability of these passive electronic components, including capacitor elements.

[0005] As dielectric films, capacitor elements using aluminum films, thin aluminum oxide films, or polymer films are often used. Due to the structure and properties of these dielectric films, such passive components can usually only be used up to a certain upper limit temperature not exceeding 120°C. When exceeding this upper limit temperature, dielectric ceramic films are usually used. This type of capacitor element is provided with one or more dielectric ceramic films as dielectrics instead of thermosensitive polymer films or aluminum films.

[0006] To shift the upper limit temperature to a temperature far exceeding 120 °C, several systems are technically known. For example, Na 0.5 Bi 0.5 TiO3 (NBT)-based systems or BaTiO3 (BT)-based systems or their solid solutions are considered promising materials that meet the requirements of high-temperature capacitor elements (Ren, P., He, J., Sun, L., Froemling, T., Wan, Y., Yang, S., Zhao, G. (2019), Journal of the European Ceramic Society, 39(14), 4160 - 4167). However, due to the complex defect chemistry of NBT-based materials and their solutions, materials with a stable capacitance with a dielectric loss tanδ of less than 2% in the industrially important temperature range of -50 °C to ≥ 300 °C could not be found for a long time (Zeb, A., & Milne, S. J. (2015), Journal of Materials Science: Materials in Electronics, 26(12), 9243 - 9255). Recently, a material system that meets the temperature range set by the industry has become known. This includes the material system of (1 - x)[0.8(0.94Na 0.5 Bi 0.5 TiO3·0.06BaTiO3)·0.2CaZrO3]-xBiAlO3. This material system contains oxides of bismuth sodium titanate, barium titanate, calcium zirconate, and bismuth aluminate (Hoang, A. P., Steiner, S., Yang, F., Li, L., Sinclair, D. C., & Froemling, T. (2021), Journal of the European Ceramic Society, 41(4), 2587 - 2595).

[0007] Capacitor elements are usually fabricated from slips. A slip is understood to be a mixture of ceramic powder and an organic medium. For this purpose, the ceramic powder can contain air-resistant extracts such as oxides and / or carbonates and their mixtures, which are weighed in appropriate stoichiometric ratios and sintered by solid-state reactions to form the desired dielectric ceramic film.

[0008] The organic medium enables an optimal mixing of the components of the ceramic powder before sintering. After production, the slip can be cast as a thin film in a film casting process.

[0009] The properties of the sintering slip are greatly influenced by the composition of the slip, the preparation steps carried out to prepare the slip, and the parameters used during preparation, thus determining to a great extent the final properties of the capacitor element.

Prior Art Documents

Non-Patent Documents

[0010]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0011] A method known from the prior art for manufacturing a capacitor element having a dielectric ceramic film, a slip for manufacturing a dielectric ceramic film, and improving a capacitor element having a dielectric ceramic film are the subject of the present invention.

Means for Solving the Problem

[0012] According to the present invention, this problem is solved by a method for manufacturing a capacitor element having a dielectric ceramic film, wherein the organic medium includes at least one liquid solvent containing at least 1-butanol, at least one plasticizer containing tributyl acetylcitrate, at least one dispersant, and at least one binder.

[0013] According to the present invention, a capacitor element having particularly advantageous properties having a dielectric ceramic film made from the slip according to the present invention can be manufactured. The material system optimized by this synthesis is particularly suitable for use at elevated temperatures or under increasing temperature fluctuations, and under high voltages during operation. Furthermore, in the temperature range under consideration, it provides a high energy storage density and high efficiency with low dielectric losses.

[0014] The properties of the resulting dielectric ceramic film are determined in particular by the slip preparation step. Preferably, the oxides Bi2O3, TiO2, ZrO2, and Al2O3, and the carbonates Na2CO3, BaCO3, and CaCO3 are weighed in stoichiometric ratios to each other, and this slip can be sintered to (1 - x)[0.8(0.94Na 0.5 Bi 0.5 TiO3·0.06BaTiO3)·0.2CaZrO3]·xBiAlO3 in the sintering step. The optimal properties shown here are given in the range of x = 0.5, 1, 1.5, 2, 4, and 8 mol%. However, particularly preferably, the ceramic powder is 0.995[0.8(0.94Na 0.5 Bi 0.5(TiO3·0.06BaTiO3)·0.2CaZrO3]·0.005BiAlO3 is weighed so that it is produced. The dielectric ceramic film produced from this slip shows a stable relative permittivity in the range from -83°C to 550°C, with a slight variation of ≦15%, and shows a maximum value of 630 at 1 kHz. The dielectric loss tanδ≦0.02 is stable in the range from -68°C to 391°C, and the maximum applicable range as a capacitor element is from -68°C to 391°C.

[0015] As already described, the composition and ratio of the materials used in the slip are crucial for the properties of the dielectric ceramic film produced therefrom. In the slip preparation step, an organic medium is added in addition to the ceramic powder. The organic medium includes at least one liquid solvent including at least 1-butanol. By using 1-butanol as compared with solvents known from the prior art such as ethanol and / or butan-2-one, since 1-butanol evaporates more slowly than the aforementioned solvents, there is an advantage that the ceramic powder has sufficient time to settle after being mixed with the organic medium, and a packing with the highest possible density of individual particles of the ceramic powder can be formed. However, in addition to 1-butanol, other solvents can also be used, particularly solvents that exist in liquid form at the synthesis temperature range, i.e., room temperature, and have an evaporation rate similar to that of 1-butanol at room temperature. The rapid evaporation of ethanol or butan-2-one may lead to the formation of voids due to the resulting limited sedimentation, and may also lead to an increase in the generation of secondary phases after the sintering step due to non-uniform filling and thus non-uniform distribution. Since such secondary phases cannot be removed or require excessive labor to remove, such secondary phases may significantly degrade the properties of the final dielectric ceramic film.

[0016] It is advantageous to use tributyl acetyl citrate as a plasticizer. The plasticizer serves to maintain the flexibility of the cast film after casting. As plasticizers, for example, polyethylene glycol is known from the prior art. In contrast to the hygroscopic polyethylene glycol, tributyl acetyl citrate is non-hygroscopic. When using a hygroscopic plasticizer, during the preparation of the slip or during the storage period, water may accumulate in the plasticizer itself, even if only on the surface, or penetrate deep into the structure of the slip. The water molecules deposited on the surface or present within the structure may evaporate during the sintering stage of the slip and leave pores when leaving the structure, which can, on the one hand, locally disrupt the structure and, on the other hand, change and decrease the final density of the components, thus potentially reducing the desired properties. On the other hand, since tributyl acetyl citrate does not accumulate a large amount of water, the use of this plasticizer does not significantly affect the final density of the components. In addition to the use of tributyl acetyl citrate, other non-hygroscopic plasticizers can also be used. Furthermore, in contrast to, for example, the widely used phthalates, the use of tributyl acetyl citrate is biologically harmless and can thus be a more environmentally friendly option.

[0017] A dispersant is typically a molecular compound that can prevent aggregation over a period of time by adhering to dissolved particles, in this case particles of ceramic powder. This is achieved by the fact that the molecules of the dispersant bind to the first particle and thus prevent direct adhesion, i.e., direct contact between the first particle and a further second particle, and the overall adhesion of the dispersant sterically prevents the aggregation of the individual particles. From the prior art, a number of dispersants are known that contain, for example, oleic acid and / or its derivatives. However, oleic acid and / or its derivatives have only slight resistance to oxidation under normal conditions. The decomposition of these non-acid-resistant oleic acid and / or derivatives can lead to decomposition products that critically limit the final density of the cast film and can cause changes in the properties of the final dielectric ceramic film. For this reason, preferably, a dispersant is used that is characterized by extremely high stability, does not attack the cast film during storage, and / or is not itself decomposed by external influences. Thus, advantageously, the dispersant has a structure that effectively supports the separation of the individual particles during slipping or in the slurry, for example, by a particularly sterically demanding arrangement of chains and / or side chains. Furthermore, as already mentioned, the dispersion medium used should be thermodynamically and chemically stable. Additionally, the dispersant preferably binds as strongly as possible to the individual ceramic particles and does not detach from their surface prematurely. It has been shown in tests that Solsperse® M387 from Lubrizol in particular can be advantageously used.

[0018] Due to its structure, the binder deterministically specifies the arrangement of ceramic particles during the slip preparation step, and the components of the slip are arranged relative to each other. The binder is burned in the sintering step, oxidized into volatile gas components, and removed from the structure. Due to its three-dimensional structure, the binder determines the arrangement of individual particles and their relative positions. After the sintering step, only the dielectric ceramic film produced from the ceramic powder remains, and its structure is almost determined by the binder. Preferably, a binder that binds to the particle surface due to its size and properties and thus also functions as a dispersant can be used. PVB Mowital® LP BX860 from Kuraray Europe GmbH has proven to be particularly advantageous as a binder.

[0019] An organic medium containing at least a liquid solvent containing 1-butanol, at least one plasticizer containing at least tributyl acetyl citrate, at least one dispersant, and at least one binder can be mixed with the ceramic powder in the slip preparation step until a sufficiently homogeneous mixture is obtained. The ceramic powder itself can be produced from the aforementioned oxides and carbonates. On the one hand, it is also possible to pre-blend the oxides and / or carbonates to form a mixture and then combine it with the organic medium, or to add the oxides and carbonates and blend them simultaneously with the organic medium.

[0020] Furthermore, for example, in the sintering step of the reaction to (1-x)[0.8(0.94Na 0.5 Bi 0.5 TiO3·0.06BaTiO3)·0.2CaZrO3·xBiAlO3, it is arbitrarily assumed that instead of directly using carbonates and / or oxides, precursors of oxides and / or carbonates are used, and this precursor has the oxides according to the present invention as an intermediate step. Furthermore, the carbonates and / or oxides can be prepared from the precursors before being added to the organic medium in the slip preparation step. For example, ZrO2 can be obtained from ZrSiO4 at an elevated temperature.

[0021] To achieve the desired composition, the oxides and / or carbonates and / or their precursors used should preferably be of the highest purity possible. In particular, they should be included with a purity of ≧99.975% for Bi2O3, ≧99.6% for TiO2, ≧99.5% for ZrO2, ≧99.95% for Al2O3, ≧99.5% for Na2CO3, ≧99.8% for BaCO3, and ≧99.5% for CaCO3.

[0022] Optionally, 55 to 65% by mass of ceramic powder, 24 to 37% by mass of solvent, 0.28 to 0.38% by mass of dispersant, 3.0 to 5.5% by mass of plasticizer, and 4.5 to 5.5% by mass of binder are used to prepare a slip in the slip preparation step, and it is assumed that the mass percentages add up to 100% by mass. To obtain the above-mentioned advantages of the dielectric ceramic film, it is particularly advantageous to use the above-mentioned ratios of the components of the slip.

[0023] In an alternative embodiment of the concept of the present invention, it is assumed that at least polyvinyl butyral is used as the binder. With this binder, the individual particles of the ceramic powder are particularly advantageously arranged relative to each other. The polyvinyl butyral can also have different contents of polyvinyl alcohol and polyvinyl acetate. However, it is particularly advantageous that the content of polyvinyl alcohol is 18 to 21% by mass and the content of polyvinyl acetate is 8 to 14% by mass.

[0024] In an alternative embodiment example, in the slip preparation step, it is provided that the oxide and / or carbonate is subjected to heat treatment in order to obtain an anhydrous oxide and / or carbonate. In order to obtain the desired composition of the dielectric ceramic film during synthesis, it is particularly advantageous if the reactants used are weighed as accurately as possible in stoichiometric ratios. Stoichiometric weighing is facilitated by the fact that the oxides and / or carbonates used are in anhydrous form and thus in a precisely defined state. Anhydrous state means a state that does not contain a significant amount of water of crystallization (hydrate) in the crystal structure, or an oxide and / or carbonate to which no significant amount of water molecules are attached to the particles of the oxide and / or carbonate. By doing so, it becomes possible to synthesize the oxide and / or carbonate by weighing as accurately and stoichiometrically as possible. This is because oxides and / or carbonates can absorb or bind an uncertain amount of water, especially during long-term storage in the atmosphere, which complicates the weighing according to the present invention due to the change in mass.

[0025] One way to maintain the anhydrous state of the oxide and / or carbonate during heat treatment is to expose the oxide and / or carbonate powder to an elevated temperature for a long time so that the attached water and water of crystallization are removed from the structure. To prepare anhydrous oxides, the oxides TiO2, ZrO2, Al2O3 can be heated to a temperature of 800 °C for an appropriate time, for example 8 hours, and Bi2O3 can be heated to a temperature of 300 °C. The carbonate Na2CO3 can be treated at a temperature of 300 °C to 200 °C for 20 hours for BaCO3 and CaCO3 to achieve conversion to the anhydrous form. Furthermore, in all embodiments of anhydrous oxides and / or carbonates, it is irrelevant whether the temperature is raised as part of a temperature gradient before reaching the desired final temperature, or whether the oxide and / or carbonate is directly treated at the desired temperature in a preheating oven.

[0026] Preferably, the carbonate and / or oxide, which is currently anhydrous, is used directly for synthesis after drying or stored in an anhydrous atmosphere before being used for synthesis. If the oxides and / or carbonates are not used directly for synthesis but rather are their precursors, they can also be converted to the anhydrous form as part of the heat treatment. Alternatively, the anhydrous modified forms of the oxides and / or carbonates can also be produced by converting a suitable precursor to the oxide and / or carbonate and leaving it anhydrous as part of the heat treatment.

[0027] Furthermore, in the slip preparation step, the ceramic powder and the organic medium can be ground to form a slurry. For this purpose, the ceramic powder and the organic medium can be ground in a ball mill to form a slurry. The ceramic powder and the organic medium can be mixed either before being added to the ball mill or only inside the ball mill. By grinding the components in a ball mill, particularly fine grinding of the ceramic powder, and thus reduction in particle size, optimal and homogeneous mixing are achieved, leading to a higher purity of the final product.

[0028] In an alternative embodiment of the present invention, in the film casting step (film casting step), it is provided that the slip is cast onto a biaxially oriented polyester film. The biaxially oriented polyester film is a polyester film mainly composed of polyethylene terephthalate, and is understood to be a polyester film stretched in the longitudinal direction and in the transverse direction extending in the direction transverse to the longitudinal direction. The polyester film designed in this way can be made particularly tear-resistant, smooth and flexible due to the stretching process, which means that the slip can be cast onto the polyester film in a simple manner. The slip can be applied to the polyester film to a desired thickness by an appropriate method such as the "doctor blade method". After the film is cast, it can be peeled off from the polyester film and further processed. Mylar (registered trademark) film as the biaxially oriented polyester film has been shown by tests to be particularly advantageous for this purpose.

[0029] Furthermore, it is assumed that the slip is subjected to heat treatment in a drying step following the film casting step in order to remove the volatile organic medium from the structure before the sintering step is carried out. By performing the heat treatment before the actual sintering step of sintering the slip to form the dielectric ceramic film, there is an advantage that not only the volatile components of the organic medium but also other volatile components such as the residual amount of water can be removed from the structure and thus from the slip. It should be noted that in this heat treatment step, the actual sintering of the slip is not carried out. The volatile components of the organic medium are the aforementioned residual amount of water present in the ceramic powder and / or in the solvents, plasticizers, dispersants or binders used.

[0030] It is particularly advantageous that the volatile components of the slip are slowly and uniformly removed from the structure during the heat treatment. For this purpose, the cast film can be exposed to room temperature or a temperature slightly higher than that, and this temperature is preferably increased in a gradient manner from room temperature to the desired final temperature of the heat treatment, so that there is no rapid swelling or gas formation of the volatile components, and thus there is no risk of destroying the already cast film. The removal of the volatile components can also be carried out at the start of the sintering process. For this purpose, the temperature curve can also remain at a plateau (steady state) during the sintering step, or the removal of the volatile organic components can also be carried out directly during an extended heating process.

[0031] Also, in the electrode application step, it is also envisaged to print the electrodes on the cast film. By printing on the electrodes, it becomes easier to apply the electrodes to the cast film and / or the dielectric ceramic film. The printing can be carried out mechanically or manually.

[0032] Furthermore, in the lamination step, before the sintering step is carried out, in order to form a multilayer capacitor element as a component, a plurality of formed films each having an electrode are provided to be laminated on each other. A multilayer capacitor element refers to an element in which a plurality of dielectric ceramic films provided with electrodes are laminated in one direction such that the electrodes and the dielectric ceramic films are arranged alternately.

[0033] The laminated cast film provided with electrodes can be pre-pressed by applying pressure before the actual sintering step. This can be carried out, for example, at a pressure of one digit of kN for several seconds before increasing the pressure as required and performing cold isostatic pressing. In this way, an optimal bond between the individual films and between the electrodes and the formed films can be achieved.

[0034] In an alternative embodiment of the process according to the invention, in order to counteract the swelling of the cast film, it is provided that the laminated film is pressurized during the sintering step. In addition to the volatile components of the organic medium in the drying step, the remaining components of the organic medium can be combusted and removed from the structure during the sintering step. Combustion can be carried out directly during the sintering step or before the actual sintering step in combustion at elevated temperatures, provided that these temperatures do not yet allow sintering of the cast film. In order to address excessive degassing of the volatile components at elevated temperatures, ceramic powder can be added to the sintering step.

[0035] In order to counteract the rapid swelling of the cast film, it is advantageous to gradually increase the temperature from room temperature to the desired final temperature to counteract the rapid evaporation of the organic components or residual water from the structure. In addition, it is advantageous to apply pressure to the film during the sintering step to maintain the original shape of the film and counteract swelling.

[0036] Optionally, it is provided that the sintering step is carried out before the lamination step, in which a plurality of dielectric ceramic films provided with electrodes are laminated to each other to form a multilayer capacitor element as a component. In addition to the procedure already described, in which each cast film provided with an electrode is first laminated and then subjected to a sintering step in which the step film is sintered to form a dielectric ceramic film, according to the invention it is also envisaged that the individual cast films provided with electrodes are first sintered so that a dielectric ceramic film is formed in a sintering step carried out before they are laminated to form a multilayer capacitor element.

[0037] The problem described at the beginning is also solved by a slip for manufacturing a dielectric ceramic film, which comprises at least one solvent in which the organic medium contains at least 1-butanol, at least one plasticizer containing at least tributyl acetylcitrate, at least one dispersant, and at least one binder. The organic medium thus constituted in combination with the ceramic powder enables a slip that can be particularly preferably used for the synthesis of a dielectric ceramic film containing at least (1-x)[0.8(0.94Na 0.5 Bi 0.5 TiO3·0.06BaTiO3)·0.2CaZrO3]·xBiAlO3 (where x represents 0.5, 1, 1.5, 2, 4, and 8 mol%). Particularly advantageously, a capacitor element having the dielectric ceramic film according to any one of claims 1 to 10 can be manufactured using such a slip.

[0038] Optionally, it is provided that the slip contains 55 to 65% by mass of ceramic powder, 24 to 37% by mass of solvent, 0.28 to 0.38% by mass of dispersant, 3 to 5.5% by mass of plasticizer, and 4.5 to 5.5% by mass of binder, and the % by mass is added up to 100% by mass. In order to obtain the above-mentioned advantages of the dielectric ceramic film, it is particularly advantageous to use a slip consisting of the above-mentioned ratios of the individual components of the slip according to the present invention.

[0039] According to an alternative embodiment of the present invention, it is assumed that at least one binder contains polyvinyl butyral. Polyvinyl butyral can act as a binder on the one hand and also as a dispersant on the other hand.

[0040] The problem listed at the beginning is also solved by a capacitor element having a dielectric ceramic film, and in this capacitor element, a slip according to one of claims 1 to 10 is shown. A capacitor element having particularly advantageous characteristics can be obtained by the slip according to the present invention.

[0041] Optionally, the capacitor element comprises a plurality of dielectric ceramic films each having an electrode for forming a multilayer capacitor element as a component.

[0042] A method for manufacturing a capacitor element having a dielectric ceramic film, a slip for manufacturing a dielectric ceramic film, and a more advantageous embodiment of a capacitor element having a dielectric ceramic film will be described with reference to the following drawings:

Brief Description of the Drawings

[0043]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

[0044] Figures 1 to 3 show different embodiments of Method 1 according to the present invention for manufacturing a capacitor element having a dielectric ceramic film.

Embodiments for Carrying Out the Invention

[0045] Figure 1 schematically shows Method 1 according to the present invention for manufacturing a capacitor element having a dielectric ceramic film, and shows the steps of the individual methods.

[0046] In the first slip preparation step 2, a slip is prepared from the oxides Bi2O3, TiO2, ZrO2 and Al2O3, the carbonates Na2CO3, BaCO3 and CaCO3 and an organic medium. The organic medium includes 1-butanol as a liquid solvent, tributyl acetylcitrate as a plasticizer, a dispersant and a binder. The ceramic powder and the organic medium are mixed together in the slip preparation step and ground in a ball mill until a homogeneous slip is prepared.

[0047] In the film casting step 3 following the slip preparation step 2, the slip is applied (coated) preferably onto a biaxially oriented polyester film with a film thickness of 250 μm.

[0048] Subsequently, in the electrode application step 4, an electrode made of a silver-palladium electrode material is provided on the cast film, with a metal content of 55% and a silver-palladium ratio of 70:30. To dry the printed electrode, the cast film and the electrode are dried in a drying oven at 75 °C for 20 minutes, and then the volatile components of the solvent and the electrode material are completely evaporated and dried at 90 °C. After drying, the cast film with the electrode can be removed from the film.

[0049] The film with the electrode is pressurized in the sintering step 5. To burn and remove all organic components, it is first heated from room temperature to a temperature of 600 °C within 20 hours, and then the temperature is further raised from 600 °C to 1100 °C at a heating rate of 5 °C / min and maintained at this temperature for 2 hours, and then cooled to room temperature at a cooling rate of 5 °C / min. In this sintering step 5, the slip is sintered to (1 - x)[0.8(0.94Na 0.5 Bi 0.5 TiO3·0.06BaTiO3)·0.2CaZrO3]·xBiAlO3, (where x = 0.5, 1, 1.5, 2, 4, and 8 mol%).

[0050] Thereafter, in order to form a capacitor from the capacitor element, additional contacts can be provided as external electrodes on the capacitor element.

[0051] Figure 2 shows a modification of the manufacturing method 1 of the capacitor element including the dielectric ceramic film based on Figure 1, and the process is extended by the drying step 6 and the lamination step 7.

[0052] In the drying step 6 following the film casting step 2, before the sintering step 5 is carried out, the cast film is subjected to heat treatment to remove the volatile organic medium from the structure. This makes it possible to remove the volatile components of the organic medium, and also other volatile components, for example, the residual amount of water that may cause the slip film to rupture in the sintering step 5 in the case of rapid evaporation, from the slip.

[0053] To manufacture a multilayer capacitor element, a plurality of cast films provided with electrodes are stacked on top of each other in a stacking step to form a laminate (stack). A multilayer capacitor element is an element composed of a plurality of ceramic films provided with electrodes, which are stacked in one direction with respect to each other, and it is understood that the electrodes and the dielectric ceramic films are stacked alternately. The stacking step 7 is performed after the electrode application step 4 and before the sintering step 5.

[0054] The laminate of alternately formed films and electrodes is pressed at 6 kN and pre-pressed. Then, in order to optimize the bonding between individual films and between the film and the electrode, the laminate is cold isostatically pressed and laminated in an oil bath at 153 MPa. The pressed laminate is placed in a ceramic crucible between two aluminum oxide foam plates. The sacrificial powder of the ceramic powder prevents excessive outgassing of the volatile components of the ceramic at elevated temperatures. Then, the sintering step 5 is carried out as described above.

[0055] Figure 3 shows Method 1 according to the present invention from Figure 2, where the sintering step 5 is carried out before the stacking step 7.

[0056] Figures 4 to 6 each show different design variations of the temperature program according to the present invention during the manufacture of the dielectric ceramic film. In each case, the temperature program shows the progression of temperature as a function of time. The graphs shown are merely for displaying the temperature profile, and the scale is not shown.

[0057] Figure 4 shows the temperature program of the sintering step 5. The cast film and the applied electrode or laminate are first heated from room temperature to a temperature of 600 °C within 20 hours in order to burn off all organic components, and then the temperature is further raised from 600 °C to 1100 °C at a heating rate of 5 °C / min, held at this temperature for 2 hours, and then cooled to room temperature at a cooling rate of 5 °C / min.

[0058] FIG. 5 shows the temperature profile of Method 1 of FIG. 2 including the drying step 6 and the subsequent sintering step 5, and in FIG. 6, the drying step 6 is part of the sintering step 5.

[0059] FIG. 7 is a schematic diagram of the multilayer capacitor element 8, in which the dielectric ceramic film 9 and the electrodes 10 located therebetween are alternately arranged.

[0060] FIG. 8 shows an exemplary composition of the components in the slip according to the present invention. This slip contains 60.75% by mass of ceramic powder, 30.38% by mass of 1-butanol, 0.36% by mass of Solsperse M387 as a dispersant, 3.16% by mass of tributyl acetylcitrate as a plasticizer, and 5.35% by mass of PVB Mowital LP BX860 as a binder. The dielectric ceramic film 9 of this composition surprisingly exhibits optimal properties and is therefore particularly suitable for use under high temperatures, severe temperature fluctuations, and high electric field applications. This dielectric ceramic film shows a stable relative permittivity with fluctuations (variations) ≤ 15% in the range of -83°C to 550°C and a maximum value of 630 at 1 kHz. The dielectric loss tanδ ≤ 0.02 in the high temperature region is stable between -68°C and 391°C. As a result, the maximum applicable range when used as a capacitor element or a multilayer capacitor element is -68°C to 391°C.

[0061] FIG. 9 shows the microstructure of the composition of the dielectric ceramic film 12 according to the present invention and the multilayer capacitor element 8 made from the dielectric ceramic film 9 and the applied electrodes 10 in the prior art 11 by SEM images. In particular, compared with the prior art 11, a more homogeneous structure and improved density are observed, and as a result, the above-mentioned advantages are obtained.

[0062] Figure 10 shows the heat resistance of the composition of the dielectric ceramic film 12 according to the present invention compared with Reference 13 (Hoang, A. P., Steiner, S., Yang, F., Li, L., Sinclair, D. C., & Froemling, T. (2021), Journal of the European Ceramic Society, 41(4), 2587 - 2595), and is compared with the current prior art 11. The dielectric constant and the loss factor tanδ are plotted as functions of temperature. The composition of the dielectric ceramic film according to the present invention results in lower dielectric losses, especially in the high - temperature region, compared with the prior art 11, and thus the dielectric properties in the selected temperature range are almost the same.

[0063] Figures 11 and 12 show further advantageous properties of the capacitor element based on the slip composition according to the present invention. Figure 11 shows the polarization of the ceramic dielectric film 12 with respect to the applied electric field, and Figure 12 shows the efficiency of the polarization process as a function of the electric field. Compared with competing technologies, a very high energy storage density of 2.66 J / cm 3 (at 32 kV / mm) and an efficiency > 86% was achieved. Therefore, the capacitor element and the multilayer capacitor element 8 are suitable for use as over - voltage protection and intermediate - circuit capacitors. They can suppress the voltage peak and keep the voltage constant. In particular, the applied electric field of 32 kV / mm impressively shows the reliability in the high - voltage region.

[0064] Figure 13 shows the resistance of the composition of the dielectric ceramic film 12 according to the present invention with respect to the electric field and temperature. The capacitance is plotted against the electric field (electric field) and various temperatures from 25 °C to 125 °C. The maximum change of approximately 13% at an electric field of 20 kV / mm and simultaneously at an actual temperature of 125 °C impressively shows the stability of the dielectric ceramic film 12 according to the present invention with respect to both factors.

[0065] List of reference numbers 1 Method for manufacturing a capacitor element 2 Slip preparation step 2 Film Casting Step 4 Electrode Application Step 5 Sintering Step 6 Drying Step 7 Laminating Step 8 Multilayer Capacitor Element 9 Dielectric Ceramic Film 10 Electrode 11 Prior Art 12 Composition of Dielectric Ceramic Film According to the Present Invention 13 References

Claims

1. A method (1) for manufacturing a capacitor element having a dielectric ceramic film (9), wherein, In slip preparation step (2), a slip is prepared from ceramic powder and an organic medium. For the ceramic powder, (1 - x)[0.8(0.94Na ０．５ Bi ０．５ TiO ３ ·0.06BaTiO ３ ).0.2CaZrO ３ ·xBAlO ３ (where x represents 0.5, 1, 1.5, 2, 4, and 8 mol%) is synthesized by using at least Bi ２ O ３ , TiO ２ , ZrO ２ and Al ２ O ３ as oxides, and at least Na ２ CO ３ , BaCO ３ and CaCO ３ as carbonates, or the respective precursors of the oxides and / or carbonates are used in stoichiometric ratios, and The slip is cast as a film in the film casting step (3), and In the electrode application step (4), the electrode (10) is applied to the cast film, and In order to remove the organic medium from the structure and convert the cast film into a dielectric ceramic film (9), the cast film is sintered at an elevated temperature in a sintering step (5), and The dielectric ceramic film (9) contains at least (1-x)[0.8(0.94Na] ０．５ Bi ０．５ TiO ３ ・0.06BaTiO ３ )・0.2CaZrO ３ ]・xBiAlO ３ This includes, where x = 0.5, 1, 1.5, 2, 4 and 8 mol%, In method (1), The method (1) is characterized in that the organic medium comprises at least one liquid solvent containing at least 1-butanol, at least one plasticizer containing tributyl acetylcitrate, at least one dispersant, and at least one binder.

2. The method according to claim 1 (1), characterized in that, for the preparation of the slip in the slip preparation step (2), 55 to 65% by mass of ceramic powder, 24 to 37% by mass of solvent, 0.28 to 0.38% by mass of dispersant, 3.0 to 5.5% by mass of plasticizer, and 4.5 to 5.5% by mass of binder are used, and the total mass percentage is 100% by mass.

3. The method according to claim 1 or 2 (1), characterized in that at least polyvinyl butyral is used as a binder.

4. The method according to claim 1 or 2 (1), characterized in that in the slip preparation step (2), the oxide and / or the carbonate is subjected to heat treatment to obtain anhydrous oxide and / or carbonate.

5. The method according to claim 1 or 2 (1), characterized in that in the slip manufacturing step (2), the ceramic powder and the organic medium are pulverized to form a slurry.

6. The method according to claim 1 or 2 (1), characterized in that in the film casting step (3), the slip is cast onto a biaxially oriented polyester film.

7. The method according to claim 1 or 2 (1), characterized in that, before the sintering step (5) is carried out, the slip is subjected to heat treatment in a drying step (6) following the film casting step (3) in order to remove the volatile organic medium from the structure.

8. The method according to claim 1 (1), characterized in that in the electrode application step (4), the electrode (10) is printed on the cast film.

9. The method according to claim 1 (1), characterized in that, in the lamination step (7), before the sintering step (5) is carried out, a plurality of cast films, each having an electrode (10), are laminated to form a multilayer capacitor element (8) as a component.

10. The method according to claim 9 (1), characterized in that pressure is applied to the laminated film during the sintering step (5) in order to counteract the swelling of the cast film.

11. The sintering step (5) is performed before the lamination step (7), The method according to claim 1 (1), characterized in that in the lamination step (7), a plurality of dielectric ceramic films (9) having electrodes (10) are laminated to form a multilayer capacitor element (8) as a component.

12. A slip for manufacturing a dielectric ceramic film (9), Here, the slip comprises ceramic powder and an organic medium. Here, the ceramic powder is at least Bi as an oxide ２ O ３ , TiO ２ , ZrO ２ and Al ２ O ３ , and at least Na as a carbonate ２ CO ３ BaCO ３ and CaCO ３ , or a slip comprising the respective precursors of the oxide and / or carbonate, The slip is characterized in that the organic medium comprises at least one solvent containing at least 1-butanol, at least one plasticizer containing at least tributyl acetylcitrate, at least one dispersant, and at least one binder.

13. The slip according to claim 12, characterized in that it comprises 55 to 65% by mass of ceramic powder, 24 to 37% by mass of solvent, 0.28 to 0.38% by mass of dispersant, 3.0 to 5.5% by mass of plasticizer, and 4.5 to 5.5% by mass of binder, the total mass percentage of which is 100% by mass.

14. The slip according to claim 12 or 13, characterized in that at least one binder contains polyvinyl butyral.

15. At least (1-x)[0.8(0.94Na] ０．５ Bi ０．５ TiO ３ ・0.06BaTiO ３ )・0.2CaZrO ３ ]・xBiAlO ３ A capacitor element comprising a dielectric ceramic film (9) containing (where x represents 0.5, 1, 1.5, 2, 4 and 8 mol%), A capacitor element wherein the dielectric ceramic film (9) includes an electrode (10), and the ceramic film (9) is manufactured from a slip, characterized in that the slip comprises ceramic powder and an organic medium, and the slip is as described in claim 1 or 2.

16. The capacitor element according to claim 15, characterized in that it comprises a plurality of dielectric ceramic films (9) each having an electrode (10), and a multilayer capacitor element is formed as a component.

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