EP2013888A2

EP2013888A2 - Method for the production of a coating of a porous, electrically conductive support material with a dielectric, and production of capacitors having high capacity density with the aid of said method

Info

Publication number: EP2013888A2
Application number: EP07728137A
Authority: EP
Inventors: Florian Thomas
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2006-04-26
Filing date: 2007-04-16
Publication date: 2009-01-14
Also published as: TW200809884A; US20090168299A1; JP2009534862A; CN101432831A; WO2007125026A2; WO2007125026A3

Abstract

The invention relates to a method for producing a coating of a porous, electrically conductive support material (1) with a dielectric (2) by means of a solution of precursor compounds of the dielectric at a concentration of less than 10 percent by weight relative to the proportion of the dielectric in the total weight of the solution. Also disclosed is the production of capacitors with the aid of said method.

Description

Process for producing a coating of a porous, electrically conductive carrier material with a dielectric and production of capacitors of high capacitance density using this process

description

The present invention relates to a method for producing a closed and poorly flawed coating on a porous, electrically conductive carrier material with a dielectric and the production of high capacity capacitors density using this method.

The storage of energy in various applications is the subject of ongoing development work. The progressive miniaturization of electrical and electronic circuits leads to the demand for ever fewer or ever smaller components in order to achieve this storage. For capacitors, therefore, ever higher capacitance densities are required.

After the capacitor formulas

E = ^_1/2 C ^■ U ² and C = ε ^■ ε ₀ ^■ A / d,

where: E = energy

C = capacity

U = voltage ε = dielectric constant of the dielectric εo = dielectric constant of the vacuum

A = electrode area d = electrode spacing

high capacitance densities can be achieved by the use of dielectrics with a high dielectric constant as well as by large electrode surfaces and small electrode spacings. Furthermore, the use of high dielectric strength dielectrics is desirable to achieve high operating voltages.

Tantalum capacitors consist of a base made of sintered tantalum powder. They therefore have quite large electrode surfaces, but are due to their electrochemical preparation on tantalum pentoxide as a dielectric with only a low dielectric constant (ε = 27) set. The electrochemical manufacturing process also limits the size of the capacitors to a few millimeters, so that an elaborate parallel connection of the capacitors is necessary to provide greater capacity (so-called. "Multi-anode" capacitors). Multilayer Ceramic Capacitors (MLCCs) tolerate high voltages and ambient temperatures due to the use of a ceramic dielectric. Furthermore, ceramic dielectrics with high dielectric constants are available. However, the requirement for large electrode surfaces requires a large number of layers (> 500) with a very small layer thickness (<1 μm). Therefore, the production of such capacitors is complex and often faulty with decreasing thickness of the layers. It also can not produce capacitors with larger dimensions, as this would lead to stress cracking and thus failure of the component in the manufacture of the layer structure.

For example, tantalum or ceramic multilayer capacitors have typical capacitance densities of 10 mF / cm ³ at a nominal voltage of about 6V.

DE-A-0221498 describes a ceramic capacitor with high energy density, which consists of an inert porous support, on which a first electrically conductive layer, a second layer of barium titanate and a further electrically conductive layer are applied. For this purpose, an inert porous support made of a material such. As alumina, coated by vapor deposition or electroless plating with a metallization. In a second step, the dielectric is produced by infiltration with a titanium titanate nanodispersion and subsequent sintering at 900-1100 ° C.

Such a process can be problematic because of the complex production and the low thermal resistance of the metallization. The production of the dielectric requires temperatures of 900 - 1 100 ° C. At these temperatures, many metals already have a very high mobility which, together with the high surface tension of the metals, can cause the metallization layer to contract to form fine droplets. This is especially observed in metallization with silver or copper. In addition, infiltration with the barium titanate nanodispersion may result in uneven coating or clogging of the pores in the second step if the dispersion contains larger particles or agglomerates. An uneven coating does not allow the full interior surface of the porous support to be used, thereby reducing the useful capacitance of the capacitor and greatly increasing the risk of short circuits.

DE patent application no. 102004052086.0 describes a process for producing a capacitor in which a porous conductive support is completely coated (on its inner and outer surface) with a thin film of a ceramic dielectric. The preferred materials are oxides such as barium titanate (BaTiOa). The BaTiθ3 is applied by infiltration of the porous support with a solution containing alkoxides, carboxylates, or barium and titanium contains. After infiltration, the solution is thermally treated (one or more stages at temperatures up to about 800 ° C) to calcine the dissolved precursor compounds to the oxide. Here, the use of the most concentrated solution (according to the examples of 20 wt .-% and more) is sought in order to transport in the infiltration a lurch as high amount of material in the interior of the porous support.

Although this approach has advantages over the prior art described above, the disadvantages, in particular the possible deposition of the ceramic dielectric in the interior rather than on the walls of the pores, can not be completely eliminated. Such material is not in intimate contact with the conductive support and is therefore not used for energy storage in the capacitor. It may also occur instead of forming a dense film for the deposition of particulate material on the pore walls. The resulting defects in the film lead to short circuits in the capacitor, so to an inferior quality of the component.

The object of the invention was therefore the development of a method for producing a closed and poorly performing coating of a porous, electrically conductive carrier material with a dielectric. The coating should be able to reach the entire inner and outer surface of the substrate, but avoid clogging or unnecessary filling of the pores. The process should be economical and in particular suitable for the production of coatings which can be used in capacitors with high capacity density.

The object has been achieved by using a solution of precursor compounds of the dielectric with a concentration of less than 10% by weight, based on the proportion of the dielectric in the total weight of the solution, when coating the porous, electrically conductive carrier material.

The invention accordingly provides a process for producing a coating of a porous, electrically conductive carrier material with a dielectric using a solution of precursor compounds of the dielectric with a concentration of less than 10% by weight, based on the proportion of the dielectric in the total weight of the solution ,

The invention furthermore relates to the use of this method for producing a coating as a dielectric in a capacitor and to such a capacitor itself, its manufacture and its use in electrical and electronic circuits. It has surprisingly been found that, contrary to the obvious approaches described above, the use of low-concentration solutions leads to an improved coating quality.

If solutions containing the precursor compounds of the material to be deposited in a concentration of less than 10% by weight, based on the proportion of the dielectric in the total weight of the solution, are used to prepare the coatings, a preferred deposition of the material is possible after the thermal after-treatment determine the walls of the porous carrier. The coating material separates as a tightly closed film on the pore walls, the deposition of particulate material is suppressed. There are thus no more unnecessary and harmful deposits in the interior of the pores more noticeable. To set the desired layer thickness of the coating process can be repeated many times, without the unwanted deposits described arise.

The dielectric layers produced in this way have a high thermal, mechanical and electrical resistance and are therefore particularly suitable for use in capacitors with high capacitance density.

When using electrically conductive carrier materials also offers the advantage that no additional coating of the carrier for metallization is necessary by the already existing electrical conductivity of the carrier. The process becomes simpler and more economical, the capacitors become more robust and less susceptible to defects.

Suitable supports preferably have a specific surface area (BET surface area) of from 0.01 to 10 m ² / g, more preferably from 0.1 to 5 m ² / g.

Such carriers can be, for example, from powders having specific surface areas (BET surface area) of 0.01 to 10 m ² / g by pressing or hot pressing at pressures of 1 to 100 kbar and / or sintering at temperatures of 500 to 1600 ° C, preferred 700 to 1300 ° C, produce. The pressing or sintering is advantageously carried out under an atmosphere of air, inert gas (eg argon or nitrogen) or hydrogen or mixtures thereof at an atmospheric pressure of 0.001 to 10 bar.

The pressure used for the pressing and / or the temperature used for the thermal treatment depend on the materials used and the desired material density. Desirable is a density of 30 to 50% of the theoretical value, sufficient mechanical stability of the capacitor for the desired application and at the same time a sufficient Ensure porosity for the subsequent coating with the dielectric.

It is possible to use powders of all metals or alloys of metals which have a sufficiently high melting point of preferably at least 900 ° C., more preferably greater than 1200 ° C., and do not undergo any reactions with the ceramic dielectric during further processing.

Advantageously, the supports comprise at least one metal, preferably Ni, Cu, Pd, Ag, Cr, Mo, W, Mn or Co and / or at least one metal alloy on the basis thereof.

Advantageously, the carrier is made entirely of electrically conductive materials.

According to a further advantageous variant, the carrier consists of at least one pulverulent non-metallic material, which is enveloped by at least one metal or at least one metal alloy, as described above. Preference is given to a non-metallic material which is enveloped in such a way that no reactions take place between the non-metallic material and the dielectric, which lead to a deterioration of the properties of the capacitor.

Such non-metallic materials may be, for example, Al 2 O 3 or graphite. However, SiO 2, TiO 2, ZrO 2, SiC, Si 3 N 4 or BN are also suitable. All materials are suitable which, by virtue of their thermal stability, prevent further reduction of the porosity by sintering of the metallic material during the thermal treatment of the dielectric.

The carriers used according to the invention can have a wide variety of geometries, for example cuboids, plates or cylinders. Such carriers can be produced in various dimensions, advantageously from a few mm to several dm, and thus perfectly adapted to the particular application. In particular, the dimensions can be matched to the required capacity of the capacitor.

The carriers are connected to a contact. Advantageously, the contacting can take place by introducing an electrically conductive wire or strip directly in the production of the carrier described above. Alternatively, the contacting can also be carried out by producing an electrically conductive connection of an electrically conductive wire or strip with a surface of the carrier, for example by soldering or welding. The porous, electrically conductive carriers used according to the invention serve as a first electrode and at the same time as a carrier of the dielectric.

All materials which can usually be used as dielectrics can be used.

The dielectric used should have a dielectric constant greater than 100, preferably greater than 500.

Advantageously, the dielectric contains oxide ceramics, preferably of the perovskite type, having a composition which can be characterized by the general formula A _x B _y θ3. Here, A and B mean mono- to hexavalent cations or mixtures thereof, preferably Mg, Ca, Sr, Ba, Y, La, Ti, Zr, V, Nb, Ta, Mo, W, Mn, Zn, Pb or Bi, as well as x is a number from 0.9 to 1, 1 and y is a number from 0.9 to 1.1. A and B differ from each other.

BaTiCh is particularly preferably used. Further examples of suitable dielectrics are SrTiO 3, (Ba _x Sr _x ) TiO 3 and Pb (Zr _x Ti _x ) θ 3, where x is a number between 0.01 and 0.99.

In addition, to improve specific properties such as dielectric constant, resistivity, dielectric strength or resistance to aging, the dielectric may contain dopants in the form of their oxides in concentrations between preferably 0.01 and 10 atom%, preferably 0.05 to 2 atom%. Suitable doping elements are z. B. elements of the 2nd main group, in particular Mg and

Ca, and the 4th and 5th period of the subgroups, for example Sc, Y, Ti, Zr, V, Nb, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag and Zn, of the Periodic Table, and lanthanides such as La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

The dielectric is deposited according to the invention from a solution of precursor compounds of the dielectric on the carriers (so-called sol-gel method, also referred to as chemical solution deposition). Particularly advantageous over the use of a dispersion is the presence of a homogeneous solution, so that even with larger carriers can not come to a clogging of pores and an uneven coating. The porous supports are infiltrated with the solutions that can be prepared by dissolving the corresponding elements or their salts in solvents.

Examples of suitable salts are oxides, hydroxides, carbonates, halides, acetylacets or derivatives thereof, carboxylates of the general formula M (R-COO) _x where R = H, methyl, ethyl, propyl, butyl or 2-ethylhexyl and x = 1 , 2, 3, 4, 5 or 6, alcoholates of the general formula M (RO) _x with R = methyl, ethyl, propyl, isopropyl, butyl, sec. Butyl, isobutyl, tert-butyl, 2-ethylhexyl, 2-hydroxyethyl, 2-aminoethyl, 2-methoxyethyl, 2-ethoxyethyl, 2-butoxyethyl, 2-hydroxypropyl or 2-methoxypropyl and x = 1, 2, 3, 4, 5 or 6 of the elements described above (referred to herein as M) or mixtures of these salts. Alcoholates and / or carboxylates of barium and titanium are advantageously used.

The solvents used may preferably be water, carboxylic acids of the general formula R-COOH where R = H, methyl, ethyl, propyl, butyl or 2-ethylhexyl, alcohols of the general formula R-OH where R = methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, isobutyl, tert-butyl or 2-ethylhexyl, glycol derivatives of the general formula

R ⁱ -O- (C ₂ H ₄ -O) _x -R ² with R ¹ and R ² = H, methyl, ethyl or butyl and x = 1, 2, 3 or 4, 1, 3-dicarbonyl compounds such as acetylacetone or acetoacetic esters, aliphatic or aromatic hydrocarbons, for example pentane, hexane, heptane, benzene, toluene or xylene, ethers, such as diethyl ether, dibutyl ether or tetrahydrofuran, or mixtures of these solvents. Glycol ethers, such as methyl glycol or butyl glycol, are particularly preferably used.

According to the invention, the solution of the precursor compounds of the dielectric used has a concentration of less than 10% by weight, preferably less than 6% by weight, particularly preferably from 2 to 6% by weight, based in each case on the proportion of the dielectric in the total weight of the solution. The proportion of the dielectric in the total weight of the solution is calculated as the amount of remaining material after calcination, for example, BaTiθ3, based on the amount of the solution used.

The infiltration of the carrier can be done by immersing the carrier in the solution, by pressure impregnation or by spraying. In this case, a complete wetting of the inner and outer surface of the carrier should be ensured.

The fully impregnated with the solution carriers are then in the usual way in the oven at a temperature of 500 to 1500 ° C, preferably from 600 to 1000 ° C, more preferably at about 700 to 900 ° C, thermally treated to the dissolved Calcining precursor compounds to the oxide.

Inert gases (for example argon, nitrogen), hydrogen, oxygen or water vapor or mixtures of these gases at an atmospheric pressure of 0.001 to 10 bar can be used as the atmosphere.

In this way, thin films of preferably 5 to 30 nm in thickness are obtained on the entire inner and outer surfaces of the porous supports. In so doing, as much as possible, the complete inner and outer surfaces should be included to ensure maximum capacitance of the capacitor. To set the desired layer thickness of advantageously 50 to 500 nm, particularly preferably 100 to 300 nm, the coating process is repeated if necessary several times, for example up to 20 times. To save time and energy, the coating need not be fully calcined at each high temperature repeat such as 800 ° C. A comparable quality of the coating is also achieved if the coating initially only at low temperature, for example at 200 to 600 ° C, more preferably at about 400 ° C, annealed and only after completion of all repetitions of the coating process at high temperature, as above described completely calcined.

In order to improve the electrical properties of the dielectric, it may be necessary to carry out a further temperature treatment after sintering at a temperature between 200 and 600 ° C under an atmosphere with an oxygen content of 0.01% to 25%.

In an exemplary embodiment, the coating according to the invention of a porous, electrically conductive carrier material with a dielectric is carried out as follows:

The precursor compounds of the dielectric to be used according to the invention are dissolved in the usual manner at the same time or sequentially or first individually, optionally with cooling or with heating, in the solvent (s). The preparation of such solutions is described in the literature, for example in R. Schwartz "Chemical Solution Deposition of Ferroelectric Thin Films" in Materials Engineering 28, Chemical Processing of Ceramics, 2nd ed., 2005, pp. 713-742 Advantageously, the reaction is carried out at room temperature, after which any excess solvent is distilled off, for example by means of a rotary evaporator, until the desired concentration of the solution has been established Finally, the solution for removing suspended particles is advantageously filtered.

In this solution, the porous moldings are immersed. In addition, a vacuum of 0.1 to 900 mbar, preferably of about 100 mbar, can be applied over 0.5 to 10 minutes, preferably about 5 minutes, and then re-aerated to remove trapped air bubbles. The impregnated moldings are removed from the solution and excess solution is drained off. The shaped articles are then usually dried first, preferably for 5 to 60 minutes at 50 to 200 ° C., and then hydrolyzed for 5 to 60 minutes at 300 to 500 ° C., for example under moist nitrogen. Finally, over 10 to 120 minutes at the temperatures given above, advantageously calcined under dry nitrogen. The sequence of impregnation / drying / calcining is repeated if necessary until the desired layer thickness is reached.

The coatings prepared by the method described above have a closed and low-defect layer of the dielectric on almost the entire inner and outer surface of the substrate.

For the purposes of this invention, a coating is lacking in definition if the specific resistance of the coating is more than 10 ⁸ Ω-cm, preferably more than 10 ¹¹ Ω-cm. The resistance of the coating can be determined, for example, via impedance spectroscopy. With a known specific surface of the support (usually determined by BET measurement) and known layer thickness of the coating (usually determined by electron microscopy), the measured resistance can be converted into the specific resistance in a manner known to the person skilled in the art.

The coatings of the invention can be used as a dielectric in a capacitor.

On the dielectric according to the invention a second electrically conductive layer is applied as a counter electrode. This may be according to the prior art, any electrically conductive material commonly used for these purposes. For example, manganese dioxide or electrically conductive polymers such as polythiophenes, polypyrroles, polyanilines or derivatives of these polymers are used. Better electrical conductivity and thus lower internal resistance (ESR, equivalent

Series Resistance) of the capacitors is achieved by applying metal layers as a counter electrode, for example copper according to DE-A-10325243.

The contacting of the counterelectrode from the outside can likewise be carried out according to the prior art by any technique usually used for this purpose. For example, the contacting can be effected by graphitization, application of conductive silver and / or soldering. The contacted capacitor can then be encapsulated for protection against external influences.

The capacitors produced according to the invention have a porous, electrically conductive carrier, on whose almost complete inner and outer surface a closed and lack of defects layer of a dielectric and an electrically conductive layer are applied. The scheme of such a capacitor is shown by way of example in FIG.

The capacitors produced according to the invention show a comparison with the conventional tantalum capacitors or ceramic multilayer capacitors Improved capacity density and are thus suitable for the storage of energy in a variety of applications, especially in those that require a high capacity density. Their manufacturing processes allow a simple and economical production of capacitors with significantly larger dimensions and correspondingly high capacity.

Such capacitors may be used, for example, as smoothing or storage capacitors in electrical engineering, as coupling, screening or low-storage capacitors in microelectronics, as replacement for secondary batteries, as main energy storage units for mobile electrical appliances, e.g. Power tools, telecommunications applications, portable computers, medical devices, for uninterruptible power supplies, for electric vehicles, as complementary energy storage units for electric vehicles or hybrid vehicles, for electric elevators, as buffer energy storage units to cover power fluctuations for wind, solar , Solar thermal or other power plants.

The invention will be explained in more detail with reference to the following embodiments, but without thereby making a corresponding limitation.

Examples

Example 1: Preparation of the carrier material

- In a metal plate with cuboidal cavities of dimensions 10 x 10 x 2 mm, a nickel wire and nickel powder (Inco type T255) were filled and compacted mechanically evenly. The mixture was then sintered for 30 minutes at 800 ° C. under a hydrogen atmosphere. A solid support having a pore volume fraction of about 70% and a BET surface area of 0.1 m ² / g was obtained. Figure 2 shows an electron micrograph of the uncoated nickel support.

Example 2:

10.0 g of barium oxide were dissolved in portions under ice cooling in 30 minutes in 100 ml of methanol. A small amount of solid was removed by filtration. To the

Solution were successively added dropwise 50 g of methyl glycol and 18.5 g of titanium tetraisopropylate and stirred for 30 min. Subsequently, a solution of 4.7 g of water in 50 g of methyl glycol was added dropwise in 15 minutes and stirred for a further 4 h at room temperature. On a rotary evaporator, methanol and isopropanol were distilled off at 40 ° C. and 200 mbar. The resulting solution was mixed with methyl glycol on a

Content of 4% by weight BaTiCh set. The solution was then filtered through a 0.2 μm filter to remove suspended particles. - The porous moldings prepared according to Example 1 were immersed in the solution described above. A vacuum of 100 mbar was applied for 5 minutes and then re-aerated to remove trapped air bubbles. The impregnated shaped bodies were removed from the solution and excess solution was drained off. Thereafter, the moldings were first dried for 25 min at 150 ° C, then hydrolyzed for 30 min at 400 ° C under humid nitrogen and finally calcined at 800 ° C for 20 min under dry nitrogen.

The sequence of impregnation / drying / calcining was carried out a total of 20 times. The result was a closed and defect-poor BaTiθ3 coating of about 200 nm thickness on the inner and outer surfaces of the moldings. Figure 3 shows an electron micrograph of a closed and defect-poor BaTiθ3 coating from a 4% solution.

Example 3:

20.6 g of barium oxide were dissolved in portions in 45 minutes under ice-bath cooling in 212 ml of methanol. A small amount of solid was removed by filtration. To the clear filtrate, a solution of 17.9 g of ethanolamine in 100 ml of butyl glycol was added and the pale yellow solution stirred for 2.5 h at room temperature. The rotary evaporator was distilled off at a pressure of 2 mbar and 55 ° C methanol. 45.2 g of titanium tetrabutoxide were dissolved in 392 ml of butyl glycol and added dropwise 26.8 g of acetylacetone. The intense yellow clear solution was heated to reflux for 2 h. After cooling to room temperature, the barium aminoethylate

Solution added and stirred for 1 h. The solution was adjusted with butyl glycol to a content of 4% by weight (based on BaTiCh).

- The solution was continued as in Example 2 on. One also obtained a closed and defect-poor BaTiθ3 coating.

Example 4:

The coated moldings from Example 3 were immersed in a 30% solution of manganese (II) nitrate hydrate in water. The completely soaked moldings were removed from the solution and in each case 10 minutes at first

150 ° C and then annealed at 250 ° C in air. The sequence impregnation / tempering was carried out a total of 10 times.

- Subsequently, the moldings were first dipped for contacting in a graphite and then in a silver dispersion and each for 1 h at 150 ° C ge dries. The resulting capacitors had a capacity of 1 mF. The resistivity of the BaTiC ^ layer was> 10 ⁹ Ω-cm.

Example 5: Comparative Example

A solution having a concentration of 12% by weight (based on BaTiCh) was prepared analogously to Example 2 and this solution was used to coat moldings according to Example 1. The result was a defect rich BaTiCV coating with significant BaTiC ^ - shares without contact to the pore wall. Figure 4 shows an electron micrograph of a defect-rich BaTiCh

Coating with BaTiC ^ parts without contact to the pore wall from a 12 göige solution.

Example 6: Comparative Example

The procedure was analogous to Example 4 with the coated moldings from Example 5. The resulting capacitors had a capacity of 0.1 mF. The resistivity of the BaTiC ^ layer was <10 ⁷ Ω-cm.

Claims

claims

A method of making a coating of a porous, electrically conductive substrate with a dielectric using a solution of precursor compounds of the dielectric having a concentration of less than 10% by weight, based on the proportion of the dielectric in the total weight of the solution.

2. The method according to claim 1, characterized in that the coating is carried out by infiltration of the porous carrier material with the solution and subsequent thermal aftertreatment.

3. The method according to claim 1 or 2, characterized in that the coating is repeated several times until the desired layer thickness.

4. The method according to any one of claims 1 to 3, characterized in that the carrier material used has a specific surface area of 0.01 to 10 m ² / g.

5. The method according to any one of claims 1 to 4, characterized in that the carrier material used contains at least one metal or at least one metal alloy having a melting point of at least 900 ° C.

6. The method according to any one of claims 1 to 5, characterized in that the carrier material used contains Ni, Cu, Pd, Ag, Cr, Mo, W, Mn or Co and / or at least one metal alloy on the basis thereof.

7. The method according to any one of claims 1 to 6, characterized in that the carrier consists of at least one powdery non-metallic material, which is enveloped by at least one metal or at least one metal alloy exists.

8. The method according to claim 1 or 7, characterized in that the non-metallic material is Al2O3 or graphite.

9. The method according to any one of claims 1 to 8, characterized in that a dielectric having a dielectric constant of greater than 100 is used.

10. The method according to any one of claims 1 to 9, characterized in that the dielectric used contains a perovskite type oxide ceramic having the composition AχB _y θ3, wherein A and B mono- to hexavalent cations or mixtures thereof, and x is a number from 0.9 to 1, 1 and y is a number from 0.9 to 1.1.

1 1. A method according to any one of claims 1 to 10, characterized in that the dielectric used contains BaTiθ3.

12. The method according to any one of claims 1 to 11, characterized in that the dielectric used contains one or more doping elements in the form of their oxides in concentrations between 0.01 and 10 atom%.

13. Use of the coating prepared according to the method of any one of claims 1 to 12 as a dielectric in a capacitor.

14. A capacitor, characterized in that it comprises a porous, electrically conductive carrier, on whose inner and outer surface a first layer of a

Dielectric, produced by a method according to one of claims 1 to 12, and a second electrically conductive layer are applied contains.

15. A process for the preparation of capacitors, characterized in that on a provided with a contact porous, electrically conductive carrier on the inner and outer surface of a first layer of a dielectric, prepared by a method according to any one of claims 1 to 12, and a second contacted layer of an electrically conductive material are applied.

16. Use of the capacitors according to claim 14 in electrical and electronic circuits.