DE3538440A1 - Composition for preparing a ceramic dielectric and process for preparing a ceramic dielectric - Google Patents

Abstract

The composition according to the invention is characterised in that it comprises: (a) particles which essentially consist of a virtually cubic perovskite compound and essentially have a particle size of no more than approximately 1 mu m, the perovskite compound containing at least one A group element of the group consisting of Mg, Ca, Sr, Ba and Pb, and at least one B group element of the group consisting of Ti, Zr, Hf and Sn, and (b) powders of a glassy material melting at temperatures of no more than approximately 1100 DEG C. The composition according to the invention is sinterable at temperatures as low as approximately 1100 DEG C and less, producing in the process a densely sintered ceramic dielectric, so that the composition is advantageously suitable, for example, for fabricating a multi-layer capacitor, and enables the use of metals which can be fused at low temperatures and are less expensive, such as Ag, as the inner electrodes, instead of the conventional electrodes made from noble metals such as Pd or Pt.

Description

Mass for the production of a ceramic dielectric and

Method for Manufacturing a Ceramic Dielectric The invention relates to a mass for producing a sintered, ceramic dielectric and a method of manufacturing a ceramic dielectric using the crowd. In particular, the invention relates to a mass which contains particles which are composed of an essentially cubic perovskite compound and have a particle size of no more than about 1 µm and at low temperatures Are sinterable to a densely sintered, ceramic dielectric with outstanding to form dielectric properties, which for example practically no piezoelectricity in contrast to previously known dielectrics, which, for example, have piezoelectricity show, and the invention also relates to a method of manufacture such a ceramic dielectric using the mass.

The perovskite compound is a compound that resembles calcium titanate (Perovskite) has a similar structure, and when it is shaped and sintered, the connection forms a dielectric ceramic body, which dielectric, Has piezoelectricity and semiconductor properties. Such a ceramic Dielectric has a wide application today in communication apparatus, computers and other electronic devices as a condenser, wave filter, lighting element, Thermistors, etc.

The perovskite compound is conventionally made by mixing a carbonate or an oxide of at least one element selected from group consisting of Mg, Ca, Sr, Ba and Pb, these elements being hereinafter are designated as A group elements, with an oxide of at least one element, selected from the group consisting of Ti, Zr, Hf and Sn, these elements hereinafter referred to as B group elements, calcining the Mixing at temperatures not lower than about 1000 OC, wet pulverization, Filtration and subsequent drying made. According to this procedure however, in the calcination stage, the perovskite compound aggregates into cakes, which is difficult to even produce fine particles with a size smaller than about 1 μm can be pulverized by wet pulverization using a drum, and further the particles have an irregular shape. Hence the so obtained Particles of the perovskite compound produced by the conventional calcination method inferior in sinterability, and normally they must at temperatures of about 1300 OC or higher can be sintered to have a ceramic dielectric leveling dielectric properties suitable for practical use are to get. However, the particles inevitably grow into larger grains from about 5 µm to 10 µm in size during the sintering process.

A specific example of a capacitor in which the ceramic Dielectric is used is the well-known multilayer capacitor. The multilayer capacitor is made of sintered, ceramic dielectrics and metal electrodes one after the other in Layers combined, and sintered barium metatitanate (BaTi03) is typically used as a ceramic dielectric.

However, as described above, a conventional particle grows the perovskite connection to large grains during sintering. The size of these grains is very far from the optimal grain size for capacitor dielectrics, which is known to be in the range of about 0.5-1 µm.

Furthermore, the particles must be made from conventional perovskite compounds how BaTiO3 can be sintered at temperatures as high as about 1300-1400 OC to form a highly sintered and dense body because the particles are large.

In the manufacture of multilayer capacitors, at which the particles of the perovskite compound to high temperatures, as mentioned above, are heated together with the metal electrodes, therefore, the use of expensive Precious metals with high melting points such as Pt or Pd are inevitable as metal electrodes, which results in high manufacturing costs.

Therefore z. B. already by K. R. Chowary et al., Ferroelectrics, 1981, Vol. 37, pp. 689-692 and Japanese Patent Application Laid-Open No. 54-66450 proposed low temperature fusible glass powder and the particles to mix the perovskite compound and then at relatively low temperatures to sinter.

This procedure enables the use of at relatively lower Temperature fusible and less expensive metals such as Ag as a material for the inner electrodes in multilayer capacitors. With this procedure However, the perovskite compound also aggregates into larger grains during sintering, so that the multilayer capacitors obtained have the satisfactory properties not own.

The object of the present invention is therefore to provide a improved composition for the manufacture of sintered ceramic dielectrics and a method of manufacturing a ceramic dielectric using a such a mass, whereby the sintering of the connection is possible in a wide range is.

Based on extensive research into the production of the perovskite compound as well as sintering the joint in a wide range, it has been found that a finely divided powder consisting essentially of a practically cubic perovskite compound and which has a particle size of not more than about 1 µm in terms of the sinterability is excellent and that the sintering of such particles temperatures as low as about 1100 OC or less in a liquid phase one at low temperature fusible, vitreous material is possible to obtain a ceramic dielectric that is finely divided Particles of the sintered, cubic perovskite compound encloses and thus outstanding possesses dielectric properties. Because of the superiority of the particles, as before described in the sinterability compared to conventional particles of perovskite compounds enables the first-mentioned particles to be used in the manufacture of Multi-layer capacitors as internal electrodes are meltable at low temperatures Use metal like Ag, thereby reducing the production cost of multilayer capacitors can be significantly reduced.

It was further found that the sintered material formed from the particles Dielectric has practically no piezoelectricity and that it also has a possesses electrostatic capacity, which is essentially independent or only very much is less dependent on temperature changes and also has better dielectric properties such as a high insulation resistance and a low dielectric loss angle (Loss tangent).

The object of the invention is therefore used to achieve the object of the invention A composition characterized in that it comprises: (a) particles which are substantially consist of a practically cubic perovskite compound and essentially one Particle size not greater than about 1 µm, the perovskite compound at least one A group element selected from the group consisting of Mg, Ca, Sr, Ba and Pb and at least one B group element selected from the group consisting of Ti, Zr, Hf and Sn contains, and (b) powder of a material which melts at temperatures not exceeding about 1100 OC, vitreous material.

The composition according to the invention therefore comprises a finely divided powder, that essentially consists of practically cubic Perovskite compound with a particle size of not more than 1 t, and a powder one at low temperature fusible, vitreous material used in the manufacture of a densely sintered, ceramic dielectric can be used, the superior possesses dielectric properties compared to previously known dielectrics, wherein the ceramic dielectric by sintering the mass at temperatures of no more than about 1100 OC. According to the invention is also a ceramic Capacitor and a mass for manufacturing such a ceramic capacitor provided that has practically no piezoelectricity, but rather a higher one Has insulation resistance and a small dielectric loss angle and moreover has an electrostatic capacity which is essentially independent or is only slightly dependent on the temperature and therefore compared to previously known, ceramic dielectrics, which have piezoelectricity, for example, advantageous is.

The invention further relates to a method for producing a such ceramic dielectric, the method being characterized in that that a mixture is sintered at temperatures not exceeding about 1100 OC, which consists of: (a) Particles, which consist essentially of a practically cubic Perovskite compound exist and essentially have a particle size of no more than about 1 µm, the perovskite compound having at least one A group element the group consisting of Mg, Ca, Sr, Ba and Pb and at least one B group element the group consisting of Ti, Zr, Hf and Sn, and (b) powder one at temperatures of no more than about 1100 OC melting vitreous material.

The invention is explained in more detail with reference to the drawing; in the drawing are: 1 shows an electron micrograph at 20,000 times magnification of BaTiO3 particles, which after a hydrothermal Reaction were established; Fig. 2 is an X-ray diffraction diagram of a ceramic Dielectric made by sintering the mass according to the invention; Fig. 3 is a diagram showing the temperature dependence of some ceramic dielectrics reproduces according to the invention; and FIG. 4 shows an electron micrograph at 20,000 times magnification of BaTiO3 particles, which according to the conventional Calcining processes were produced.

The particles of perovskite compound used according to the invention include the perovskite compound, which is a practically cubic, crystallographic Has structure and it contains at least one A group element selected from the group consisting of Mg, Ca, Sr, Ba and Pb, and at least one B group element, selected from the group consisting of Ti, Zr, Hf and Sn, furthermore have Particles have a particle size practically no more than about 1 µm.

The particles of the perovskite compound, which is practically cubic, are, as already known, by mixing a hydroxide of at least one A group element, as mentioned before, with a hydroxide of at least one B group element, as mentioned before, and then performing a hydrothermal reaction prepared in an aqueous reaction medium.

The mixture of the aforementioned hydroxides can be carried out in a simple manner be produced, e.g. B. by mixing a hydroxide of the A group element with a hydroxide des-B group element. Furthermore, the mixture the hydroxides by mixing an A group element salt and a salt of the B group element and then reaction of the mixture obtained with an alkaline one Compound or by mixing a hydroxide (or a salt) of the A group element with a salt (or a hydroxide) of the B group element and then reacting the obtained mixture with an alkaline compound or by reaction of a hydroxide (or an alkoxide) of the A group element with an alkoxide (or a hydroxide) of the B group element or by mixing an alkoxide of the A group element with an alkoxide of the B group element and subsequent hydrolysis of the obtained Mixture can be produced.

Depending on the way and the conditions under which the mixture of hydroxides is prepared, the mixture obtained can partially a perovskite compound or its precursor compound, which is on the way to a fully crystallized perovskite compound is included. Hence can the mixture of hydroxides is partly a perovskite compound or its precursor contain. Furthermore, the mixture of the hydroxides can be a mixture of the perovskite compound with a low degree of crystallinity overall.

The finely divided particles, which essentially consist of practical cubic perovskite compound with a particle size no greater than about 1 ßm exist, as they are used according to the invention, are obtainable by that the aforementioned mixture of hydroxides is subjected to the hydrothermal reaction is. The hydrothermal reaction is already well known, this is where the mixture becomes the hydroxide is heated under alkaline conditions in an aqueous medium. There the mixture of hydroxides is inherently alkaline, the addition of an alkaline one Compound to the mixture is not required, however, an alkaline compound can be used in addition to the mix, if if so desired, added will.

Preferably, the mixture of hydroxides is heated to a temperature in Range from about 100 OC to temperatures less than the critical temperature of the reaction medium used heated. When the temperature of the hydrothermal If the reaction is less than about 100 "C, the reaction of the hydroxides only proceeds so insufficient that the perovskite compound cannot be obtained in high yields will. The higher the reaction temperature, the faster the reaction rate for the formation of the perovskite compound, while at all the higher reaction temperatures also the more expensive reaction vessels are required and the cost of the required energy increase. Therefore the temperature is the hydrothermal Reaction from a practical point of view is not more than about 300 OC and is usually in the range of about 120-300 OC, after the hydrothermal reaction will the slurry of the reaction mixture is filtered and the resulting solid is filtered is dried to give finely divided particles of practically cubic perovskite compound having a particle size of no more than about 1 µm.

If necessary, the degree of alkalinity, i. H. the degree of Excess of alkali or the concentration thereof in the aqueous medium is adjusted will. The greater the excess amount of the alkaline compound, the less is generally the particle size of the perovskite compound obtained. The bigger the concentration of the hydroxide, the smaller the particle size of the obtained perovskite compound. Therefore, the size of the perovskite compound obtained by the alkalinity and / or the concentration of the hydroxides in the hydrothermal Response can be controlled.

The particles of the hydrothermal in the previously described reaction obtained perovskite compound is essentially spherical and they exist practically made of cubic perovskite compound and have a particle size usually in the range of 1-0.01 Am, being different from the particles of that previously described Calcination process differentiate the perovskite compound. The spherical or spherical particles of the perovskite compound, which after the hydrothermal Process produced still have a uniform particle size distribution and a large surface energy due to the finely divided spherical shape.

The finely divided particles of practically cubic perovskite compound can also be done by methods other than the hydrothermal method described above be produced, as is known per se, for example according to the so-called Solution process, the metal alkoxide process, or a mixed precipitation process like this in Kino Zairyo (Functional Material), December 1982, pp. 1-8.

In the metal alkoxide method, a mixture of an alkoxide becomes at least an A group element and an alkoxide of at least one B group element hydrolyzed by water to form the perovskite compound, or an alkoxide of an A group element is hydrolyzed by a hydroxide of a B group element. The co-precipitation process usually includes a hydroxide co-precipitation process and a method of an organic acid salt. In the hydroxide mixed precipitation process becomes a mixture of a salt of an A group element and either a salt or a hydroxide of the B group element with an alkaline compound among Formation of a mixture of the hydroxides of the A group element and the B group element reacted, and the mixture is then at 500-900 OC to form the perovskite compound calcined. For example, the addition of an aqueous solution of titanium tetrachloride results to an aqueous solution of Barium hydroxide, what excess amounts of sodium hydroxide herein, the cubic perovskite compound. Be the procedure using a salt of an organic acid becomes a mixture of a salt of the A group element and a salt of the B group element with an organic one Acid converted to a water-insoluble complex salt of the organic acid, which containing the A and B group elements, and the complex salt is made by Heating to 500-900 OC decomposes to form the perovskite compound. For example For example, oxalic acid or citric acid can be used as the organic acid.

As previously described, the particles which are essentially from practically cubic perovskite compound with a particle size of no more as 1 am, made by any of the methods previously described be, d. H. according to the hydrothermal process, the metal alkoxide process and the Mixed precipitation processes, and any such particles of the perovskite compound, as previously described can be used in accordance with the invention. Under these However, particles are particles of the perovskite compound which are produced by the hydrothermal process according to the invention, since these particles are practically spherical or spherical so that they give higher packing when molded so that the sinterability is greatly improved during the sintering process and thereby a highly sintered one and dense, ceramic dielectric is obtained. Furthermore, the particles have the advantage that they are fusible at low temperature during sintering Glass, as will be described later, a uniform dispersion of the sintered particles in a matrix of the glass.

When making the perovskite joint after the conventional one however, hydrothermal processes generally find it difficult to complete the reaction, ', nd this has the consequence that unreacted connections of the B group element, z. B. titanium compounds, remain as solids in the reaction mixture while unreacted compounds of the A group element, e.g. B.

Barium compounds, left behind and in the water after the hydrothermal Reaction remain resolved. Therefore, if the reaction mixture with water after the Reaction is washed, the water-soluble compound is removed therefrom, and the obtained perovskite compound is from the B group element in larger amounts as the stoichiometric amounts corresponding to the perovskite compound, or the A group element in amounts less than the stoichiometric amount. Therefore, such a perovskite compound does not give a sintered one after the sintering process Body that has an atomic ratio of the A group element to the B group element, d. H. has an A / B ratio with the exact value desired. For example it is difficult to find a BaTiO3 sintered ceramic dielectric with a Ba / Ti ratio of exactly 1.00.

As the rate of conversion of the mixture of hydroxides to the perovskite compound In addition, as each response varies, it is difficult to get the A / B ratio control of the obtained perovskite compound and therefore are according to the conventional, Perovskite compounds produced by hydrothermal reaction are often unsuitable for use in the manufacture of high performance ceramic dielectrics.

In contrast to the conventional, previously described, hydrothermal The aforementioned metal alkoxide process and the mixed precipitation process make it possible to Manufacture particles, which are practically composed of cubic perovskite compound and are no more than about 1 µm in size and beyond have a precisely controlled A / B ratio and therefore these give rise to particles a ceramic dielectric with superior dielectric properties such as relative Dielectric constant. However, the particles have the Barium hydroxide, which contains excess amounts of sodium hydroxide therein, the cubic perovskite compound. In the method using an organic acid salt, a Mixture of a salt of the A group element and a salt of the B group element reacted with an organic acid to form a water-insoluble complex salt of the organic acid containing the A and B group elements, and the complex salt is produced by heating to 500-900 OC to form the perovskite compound decomposed. For example, oxalic acid or citric acid can be used as the organic acid be used.

As previously described, the particles which are essentially from practically cubic perovskite compound with a particle size of no more than 1 µm, made by any of the methods previously described be, d. H. according to the hydrothermal process, the metal alkoxide process and the Mixed precipitation processes, and any such particles of the perovskite compound, as previously described can be used in accordance with the invention. Under these However, particles are particles of the perovskite compound which are produced by the hydrothermal process according to the invention, since these particles are practically spherical or spherical so that they give a higher packing when molded so that the sinterability is greatly improved during the sintering process and thereby a highly sintered one and dense, ceramic dielectric is obtained. Furthermore, the particles have the advantage that they are fusible at low temperature during sintering Glass, as will be described later, a uniform dispersion of the sintered particles in a matrix of the glass.

When making the perovskite joint after the conventional one however, hydrothermal processes generally make it difficult to complete the reaction, and this has the consequence that unreacted compounds of the B group element, z. B. titanium compounds, remain as solids in the reaction mixture while unreacted compounds of the A group element, e.g. B.

Barium compounds, left behind and in the water after the hydrothermal Reaction remain resolved. Therefore, if the reaction mixture with water after the Reaction is washed, the water-soluble compound is removed therefrom, and the obtained perovskite compound is from the B group element in larger amounts as the stoichiometric amounts corresponding to the perovskite compound, or the A group element in amounts less than the stoichiometric amount. Therefore, such a perovskite compound does not give a sintered one after the sintering process Body that has an atomic ratio of the A group element to the B group element, d. H. has an A / B ratio with the exact value desired. For example it is difficult to find a BaTi03 sintered ceramic dielectric with a Ba / Ti ratio of exactly 1.00.

As the rate of conversion of the mixture of hydroxides to the perovskite compound In addition, as each response varies, it is difficult to get the A / B ratio control of the obtained perovskite compound and therefore are according to the conventional, Perovskite compounds produced by hydrothermal reaction are often unsuitable for use in the manufacture of high performance ceramic dielectrics.

In contrast to the conventional, previously described, hydrothermal The aforementioned metal alkoxide process and the mixed precipitation process make it possible to Manufacture particles, which are practically composed of cubic perovskite compound and have a size of no more than about 1; im and beyond have a precisely controlled A / B ratio and therefore these give rise to particles a ceramic dielectric with superior dielectric properties such as relative Dielectric constant. However, the particles have the Perovskite compound, which were produced by the alkoxide process or the mixed precipitation process, on the other hand disadvantage in that they tend to coagulate easily when in be sintered at a lower temperature fusible glass, so that the sintered Particles are not uniformly dispersed or distributed in the glass matrix.

Therefore, the perovskite compound used according to the invention particularly preferably produced by a process which comprises: (a) implementation a hydrothermal reaction in an aqueous reaction medium on a mixture a hydroxide of at least one A group element selected from Mg; Ca, Sr, Ba and Pb and a hydroxide of at least one B group element the group consisting of Ti, Zr, Hf and Sn; (b) adding an insolubilizing agent Means to the reaction mixture obtained for the insolubilization of water-soluble, Compounds of the unreacted A group element dissolved in the aqueous medium for setting the ratio of the A group element to the B group element in a resulting compound to a desired A / B ratio; or (c) filtering, Washing with water and drying the obtained reaction mixture for recovery of a solid reaction product, dispersing the reaction product in an aqueous Medium for forming a slurry, adding a water-soluble compound of the A group element to the slurry and then adding an insolubilizing agent Means to the slurry to insolubilize the water-soluble compound of the A group element to set the ratio of the A group element to the B group element in an emerging compound to a desired A / B ratio; and (d) filtering, washing and drying the resulting mixture to provide the perovskite compound with the desired A / B ratio.

This procedure is described in the applicant's patent application P 35 26 674.0 fully described. According to the procedure, the insolubilized remains Compound in the reaction product after washing the product of the hydrothermal Reacts with water back, and as a result provides drying and calcining of the reaction product finely divided and spherical particles of practical cubic perovskite compound with the exact, desired A / B ratio.

The insolubilizing agent usually becomes the reaction mixture after the hydrothermal reaction to insolubilize or fix the water-soluble Compound of the unreacted A group element added herein. The amount of the unreacted A group element in the reaction mixture can be removed by removing a small amount of the reaction mixture as a sample and then washing the sample with water, filtering out the solids from the sample and analyzing the amounts of A-group elements or B-group elements are determined herein.

An example of other procedures is that the reaction mixture filtered and then with water to remove the water-soluble compounds of the unreacted A group element is washed and the solid reaction product obtained is analyzed herein to determine the A / B ratio. On the basis of the so determined ratio becomes the required amount of the A group element for setting the A / B ratio of the resulting connection to a predetermined one Value fixed 'and a water-soluble compound of the A group element is with mixed with the reaction product, this is followed by the insolubilization of the compound of the A group element. Alternatively, a water-insoluble compound can also be used of the A group element are added to the slurry of the reaction product, to reduce the A / B ratio in the resulting compound desired Set A / B ratio.

The insolubilizing agent is one such material or one Compound that they are water-insoluble, solid materials or compounds of the A group element forms, which are easily decomposed by sintering, so that it is in a sintered body of the mass does not remain, e.g. B. carbon dioxide / carbonate one Alkali metal, alkaline earth metal or ammonia such as sodium carbonate and ammonium carbonate, an alkali metal salt of an organic carboxylic acid such as lauric acid, myristic acid, Palmitic acid and stearic acid, an organic polybasic carboxylic acid like Oxalic acid, ketomalonic acid, tartaric acid, maleic acid, malonic acid and succinic acid, an alkali metal salt of these polybasic carboxylic acids, cation exchange resins such as methacrylic acid resins (trade name Amberlite IRC-50), carboxylic acid resins (trade name Dekation H-70), phenolic carboxylic acid resins (trade name Duolite CS-100) and acrylic acid resins (Trade name Duolite CS-101).

As an insolubilizing agent, which is water-insoluble, solid materials -The A group element forms, which in a obtained, sintered body of the Remaining connection, but no undesirable properties -in the sintered Bodies result, be for example silicon dioxide such as zeolites and inorganic ones Called ion exchange resins.

After fixing the A-group element, as described above, the reaction mixture of the hydrothermal reaction is filtered, washed with water and dried, usually at temperatures of about 100-200 OC in the usual way, around the particles of practically cubic perovskite compound with any, Gain the desired A / B ratio.

The practically cubic perovskite compound particles thus obtained are finely divided spheres with a diameter of no more than about 1 µm and also have exactly the desired A / B ratio. Hence these are Particles in terms of packing, dispersibility and sinterability superior and form a densely sintered body when at relatively low Temperatures are sintered. Another advantage is that the particles are thin Form dielectric, which has a more stable performance than dielectrics shows which of particles are produced by the conventional hydrothermal process Perovskite connection were made.

It is already known that when sintering the perovskite compound Generally the addition of additives to the mixture allows particle growth and the electrical properties of the sintered ceramic part obtained steer. According to the invention, such an additive can also be used during manufacture of the sintered ceramic dielectric can be used. The additives include Compounds of B, Bi, pron alkali and alkaline earth metals-z .. Na, K and Li, from rare earth metals, e.g. B. Y, Dy, Ce and Sm, of transition metals, e.g. B. Fe, Mn, Co, Ni and Nb and furthermore Si or Al. The additives can be at any Stage of production of the perovskite compound or the sintered, ceramic Dielectric can be added. This means that the additive at the stage the preparation of the hydroxide mixture for the hydrothermal reaction, in the case of the hydrothermal reaction Reaction of the mixture or in the stage of fixation or insolubilization of the A group element or remaining unreacted in the reaction mixture can be added in the sintering stage of the composition according to the invention. the The mass according to the invention is explained in more detail below.

The mass according to the invention for the manufacture of a ceramic Dielectric comprises the particles of the perovskite compound as described herein and a powder one at temperatures not higher than about 1100 ° C and preferably in the range of about 400-1000 OC fusible, vitreous material. The glassy material that is meltable at low temperature is usually a compound of inorganic oxides and preferred oxides which are according to the invention are applicable include oxides of Bi, B, Pb or W, which are at temperatures are preferably meltable in the range of about 400-1000 OC.

As can be seen from the description given above, the mass according to the invention the additive described above in addition to the particles the perovskite compound and the powder of the low-temperature meltable Glass included.

A ceramic dielectric is made by sintering the previously described Mass made at temperatures no greater than about 1100 "C in accordance with the invention. The mass used is preferably granulated before sintering so that it is light can be sintered. It is known that in general when sintering the perovskite compound in the presence of a glass fusible at a low temperature, the higher the temperature Quantities of the glass the more strongly the mass is sintered, while the dielectric constant of the dielectric obtained is the lower.

Therefore, the amount of the low-temperature meltable glass becomes in the mass precisely with regard to the degree of sintering and the desired. Dielectric constant selected. However, the amount of the low-temperature meltable glass is in the mass preferably in the range of about 1-30% by weight and preferably in the range of about 3-15% by weight, based on the weight of the perovskite compound used in the mass.

As previously described, the composition of the invention closes the particles a, which consist essentially of practically cubic perovskite compound and have a particle size of no more than about 1 µm. Therefore, if the particles in a liquid phase of the glassy, meltable at low temperature Material, which is the other component of the mass, at temperatures of not more than about 1100 "C are sintered, the mass results in a highly sintered, dense, ceramic dielectric, which has practically no piezoelectricity.

The ceramic dielectric also has a high insulation resistance and a low, dielectric loss angle, but has an electrostatic Capacity, which is practically independent or only slightly dependent on the temperature is.

Since the mass according to the invention also at such low temperatures such as about 1100 OC or below to form a highly sintered and dense, ceramic dielectric can be sintered, the mass is particularly suitable for production of multilayer capacitors suitable, with the use of one at lower Temperature fusible material such as silver is possible as an inner electrode and as a result, the production costs of the inner electrode and also the energy costs for heating can be decreased.

The composition of the invention forms when they are after a hydrothermal Processes made perovskite compounds include, in general, in particular a highly sintered, ceramic dielectric, as the particles are spherical or are spherical and therefore opposite in terms of dispersibility and packing particles produced by other methods are advantageous.

In contrast, the use results in one after the metal alkoxide process or the mixed precipitation process produced a ceramic perovskite compound Dielectric, which in particular with regard to the relative Dielectric constant is excellent, for example because the particles have a precisely controlled A / B ratio own.

However, particles are one made by the hydrothermal process Perovskite compound, in which the unreacted compounds of the A group element were insolubilized after the reaction, particularly preferred because the particles are not only have a precisely set A / B ratio, but also with regard to sinterability are superior, and the particles are moreover uniform in the matrix of the glass be dispersed when the particles are in a liquid phase of the at lower Temperature fusible glass to be sintered. Therefore a mass forms which the particles of the perovskite compound produced by the improved hydrothermal process includes, successfully a much thinner, ceramic dielectric than previously known Dielectrics and it is particularly useful, for example, for making a compact ceramic .capacitor with small dimensions with stable and high performance suitable.

The invention is illustrated in more detail by means of the following examples.

Example 1 A quantity of 139 g of an aqueous titanium chloride solution, which includes partially hydrolyzed titanium tetrachloride, the titanium chloride has the formula TiCl2.36 (OH) 1.64 and the solution has 16.5% by weight titanium (0.48 mol) and contains 28.8% by weight of chlorine, was mixed with 1250 ml of water at a temperature of 40 ° C., and 483 ml of a 5.0% strength by weight were added to the resulting solution Ammonia solution in water was added over 30 minutes to make a slurry of To produce titanium hydroxide. The titanium hydroxide was washed with water and filtered, then 151.4 g were added thereto under a nitrogen atmosphere Ba (OH) 2.8H20 (Ba = 0.48 mol) was added, followed by the addition of water to the reaction mixture to make a slurry of a mixture of titanium hydroxide and barium hydroxide in a concentration of 0.8 mol / l, based on BaTiO3.

A 600 ml quantity of the slurry was placed in a 1 liter autoclave Stainless steel (Hasteloy) entered, taking it to about 200 OC for 90 minutes Stirring heated at a speed of 700-900 rpm, and the hydrothermal Subjected to reaction at about 200.degree. C. for 5 hours. After the reaction it was the slurry was washed with water and filtered to obtain BaTiO3 particles.

Fig. 1 is an electron micrograph at 20,000 times Magnification showing that the particles of BaTi03 thus obtained are spherical and are uniform in diameter, and based on this photograph the mean diameter of the particles was determined to be about 0.1 µm. An X-ray diffraction diagram of the particles showed that this corresponds to that of cubic BaTiO3.

A quantity of 3.95 g of powdered boron oxide (B203) and 94.20 g of powdered Bismuth oxide (Bi203) were mixed together in a mortar, the obtained Mixture was placed in a platinum crucible and allowed to melt to about 700 ° C the mixture heated. The molten mixture was poured into water for rapid solidification poured. The solid obtained was placed in a mortar and then in a ball mill pulverized to make a powder of a low-temperature melting glass B 203 -Bi 203 to get.

The glass powder described above was mixed with the BaTiO3 in amounts of 5% by weight, 10% by weight or 15% by weight, based on the BaTi03, mixed in a mortar, this was followed by the addition of an 8% strength by weight aqueous polyvinyl alcohol solution.

The obtained mixture was granulated and then made into green pellets of 20 mm diameter is deformed under a pressure of 981 bar (1000 kg / cm2). The green Pellets were then heated to about 400 ° C. for 3 hours to decompose the polyvinyl alcohol heated, and at temperatures as listed in the table for 1 hour sintered to produce a sintered ceramic body. The density is also indicated in the table.

The sintered ceramic body was polished on both surfaces, so that it had a thickness of about 1.0 mm, and it was made with Ag with the aid coated by an ion coater. The relative dielectric constant, the dielectric Loss angle and specific resistance were measured. The relative dielectric constant and the dielectric loss angle were measured at 1 kHz with an LF impedance meter (4192A, Yokagawa-Hullet Packard) was measured, and the resistivity was found at 20 OC, based on a current after 1 minute after application of a direct voltage of 2 V measured with a picoammeter (4140 B, Yokagawa-Hullet Packard). the Results are also shown in the table. From this it can be seen that the mass according to the invention provides a ceramic dielectric, which a better Has sinterability and better dielectric properties.

Fig. 2 is an X-ray diffraction diagram of a sintered ceramic Dielectric of approach 4 in the table. 3 shows the temperature dependency the ceramic dielectrics of batches 1, 4 and 7 as representative dielectrics according to the invention.

A direct voltage of 3 kV / mm was applied to the ceramic dielectric of approaches 1, 4 and 7 applied for 30 minutes to a polarization therein and the electromechanical union coefficients or Kp values were measured. All dielectrics have been found to have a Kp of practically Own zero, d. H. that they show no piezoelectricity.

Comparative Experiment A High purity barium carbonate and titanium dioxide were used mixed together in equimolar amounts, and the mixture was at a temperature Calcined at 1200 "C for 2 hours, wet-milled in a ball mill to get BaTiO3 particles with an average particle size of 1.6 m. Figure 4 is a electron micrograph at 20,000 times magnification of the particles.

The BaTiO3 particles thus obtained were with the one prepared in Example 1, Low-temperature meltable glass powder in an amount of 5% by weight, based on on the BaTi03, mixed in a mortar. The obtained mixture became one sintered ceramic body in the same manner as in the example.

The values for density and dielectric properties are indicated in the table, the dielectric has only a low density and one low resistivity and a much larger dielectric loss angle than the dielectrics of the invention.

Comparative experiment B Commercially available, high-purity BaTiO3 particles with an average particle size of 1.3 µm were prepared with the in Example 1, Low-temperature meltable glass powder in an amount of 5% by weight, based on on the BaTiO3, mixed in a mortar. The obtained mixture became one sintered ceramic body in the same manner as in Example 1.

The density and dielectric properties are in the table indicated, the dielectric is with that of the previous comparative experiment A regarding the Properties comparable.

Example 2 A slurry of BaTi03 obtained in the same manner as in Example 1, it was washed with water and filtered.

The filtrate was analyzed by atomic absorption spectroscopy, the conversion of barium was found to be 98.3%, the conversion being of barium is defined as follows: / (Mol Ba in hydroxide mixture) - (Mol Ba im Filtrate) ~ / x x 100 (%) mol Ba in the hydroxide mixture that filtered off as a cake, solid reaction product was redispersed in the filtrate, and it became carbon dioxide blown into the slurry to adjust the pH of the slurry to 6.5. The resulting slurry was washed with water until no more chloride ions could be detected, filtered and dried at 110 OC to get spherical Get BaTiO3 particles 0.1 µm in diameter. By fluorescence analysis it was found that the BaTiO3 had a Ba / Ti ratio of 1.00.

The BaTiO3 particles thus obtained were similar to that in Example 1 prepared low-temperature fusible glass powder in an amount of 5 wt .-%, based on the BaTi03, mixed in a mortar. The mixture obtained was molded into a ceramic sintered body in the same manner as in Example 1.

Example 3 A quantity of 76.7 g of barium isopropoxide (Ba = 0.30 mol) and 85.3 g of titanium isopropoxide (Ti = 0.30 mol) were placed in 320 ml of isopropyl alcohol a nitrogen atmosphere mixed and the resulting solution became refluxed for 2 hours. Then 65 ml was freed from carbon dioxide Water dropwise to the solution over 30-30 minutes to hydrolyze the alkoxides added, then it was cooled to room temperature and more water added to the reaction mixture to form a slurry of a mixture of titanium hydroxide and barium hydroxide with a concentration of 0.5 mol / l, calculated as BaTiO3, to obtain.

The slurry was subjected to the hydrothermal reaction in the same way as in Example 1 for the production of BaTiO3. The BaTiO3 was used to manufacture a sintered ceramic dielectric in the same way as in the example 1 sintered. The density and electrical properties are shown in the table.

Example 4 An amount of 37.1 g of a 30% strength by weight aqueous solution of SrCl2, (Sr = 0.060 mol), 255.5 g of a 26% strength by weight aqueous solution of BaCl2.2H20 (Ba = 0.24 mol) and 87.1 g of the titanium chloride solution (Ti = 0.30 mol) were under one Nitrogen atmosphere mixed together. The aqueous solution obtained was then to 184 g of a 35% strength by weight aqueous sodium hydroxide solution at one temperature of 60 ° C. was added over the course of 1 hour, followed by the addition of water to the slurry to form a slurry of a mixture of the hydroxides of titanium, Strontium and barium in a concentration of 0.5 mol / l, calculated as Ba0.8Sr0.2TiO3, to obtain.

The slurry was subjected to the hydrothermal reaction in the same way as in Example 1 for the preparation of the perovskite compound of the aforementioned formula subjected.

The compound was in the same manner as in Example 1 with the Glass powder mixed and sintered, being a sintered, ceramic dielectric was obtained. the Density and electrical properties are compiled in the table.

Example 5 A quantity of 12 g of germanium oxide (GeO2) and 42.7 g of lead oxide (PbO) were mixed in a mortar, the obtained mixture was put in a platinum crucible entered and heated to about 800 OC to melt the mixture. The melted one Mixture was poured into water and rapidly solidified, the resulting solid was' in a mortar and then in a ball mill to obtain a powder a low temperature meltable, vitreous material of the formula Pb5Ge3011 pulverized.

The glass powder was made with the BaTi03 particles obtained in Example 1 in an amount of 10% by weight, based on the BaTiO3, mixed in a mortar, this was followed by the same further processing as in Example 1 for production of green pellets.

The green pellets were allowed to decompose at about 400 OC for 3 hours of the polyvinyl alcohol, and at a temperature as shown in the table is listed, sintered for 30 minutes to form a sintered ceramic body obtain. The density and dielectric properties are given in the table.

Comparative experiments C and D The Pb5Ge30 11 powder was mixed with the in BaTi03 particles obtained in comparison tests A and B in an amount of 10 % By weight, based on the BaTiO3, mixed in a mortar, followed by the same Further processing as in Example 1 for the production of green pellets.

The green pellets were then prepared in the same manner as in Example 4 Formation of a sintered ceramic body sintered. The concentration and the dielectric properties are shown in the table.

The dielectric of Comparative Experiment C, made using that prepared according to the calcining process described in Comparative Experiment A Perovskite compound has a noticeably larger dielectric loss angle and a lower density than the corresponding dielectric of Example 5 according to FIG the invention.

The dielectric of Comparative Experiment D, made using the perovskite compound with an average diameter of 1.3 µm in the comparative experiment B, when compared with the dielectric of the comparative test, is C in its properties better, however, it is obviously inferior in its properties in comparison to the dielectric of Example 5, which under the same conditions except the perovskite compound used was established.

Table approach glass material Amount of sintered sintered ceramic Dielectric glass tempe- density tg # relative dielectric spec. Counter-material temperature (g / cm²) constant (weight%) * (° C) ** room maximum (ohm cm) temperature Ex. 1 1 Bi2O3-B2O3 5 900 4.87 2.0 830 872 1.9 x 1011 2 10 900 5.25 1.5 800 811 4.4 x 1012 3 15 900 5.37 1.3 792 811 7.5 x 1012 4 5 1000 5.60 1.4 1425 1815 2.3 x 1011 5 10 1000 5.62 1.0 1359 1705 2.3 x 1012 6 15 100 5.68 0.8 1203 1632 9.6 x 1012 7 5 1100 5.62 1.2 1811 2925 2.1 x 1011 8 9 10 1100 5.65 1.2 1690 277 4.2 x 1012 9 15 1100 5.70 0.78 1305 2619 1.5 x 1013 Ex. 2 10 Bi2O3-B2O3 5 1000 5.62 1.2 1439 1773 8.9 x 1011 Ex. 3 11 Bi2O3-B2O3 5 1000 5.62 1.3 1398 1671 5.6 x 1011 Comp. Vers. A. 12 Bi2O3-B2O3 5 1000 4.25 8.7 888 1011 2.2 x 109 Compare version B 13 Bi2O3-B2O3 5 1000 3.97 7.4 879 998 1.3 x 109 Table (continued) Approach glass material Amount of sintered sintered ceramic dielectric glass tempe- density tg # relative dielectric spec. Adverse material temperature (g / cm²) constant (weight%) * (° C) ** Room maximum (Ohm cm) temperature e.g. 4 14 Bi2O3-B2O3 5 1000 5.17 1.2 2215 2432 9.2 x 1012 Ex. 5 15 Pb5Ge3O11 10 900 5.49 1.1 1219 3461 7.7 x 1012 16 10 1000 5.72 2.5 1502 6009 2.5 x 1013 Compare Vers. C 17 Pb5Ge3O11 10 900 4.66 9.8 875 1462 2.4 x 1012 18 10 100 5.21 12.3 1015 3469 8.7 x 1012 Comp. Vers. D Pb5Ge3O11 10 900 4.74 2.9 927 2115 8.1 x 1012 20 10 1000 5.64 3.8 1211 3517 1.2 x 1013 *) Based on the weight of the perovskite compound **) the sintering time is when using from Bi2O3-B3O2 1 hour and when using Pb5Ge3O1130 minutes.

All information and characteristics disclosed in the documents, in particular the disclosed spatial arrangement, insofar as they are used individually or in combination are new compared to the prior art, claimed as essential to the invention.

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Claims (19)

Composition for the production of a ceramic dielectric and method for the production of a ceramic dielectric Claims 1. Composition for production a ceramic dielectric, characterized in that it comprises: (a) particles, which essentially consists of a. practically cubic perovskite compound exist and substantially have a particle size of no more than about 1 µm, wherein the perovskite compound has at least one A group element selected from Mg, Ca, Sr, Ba and Pb and at least one B group element selected from Ti, Zr, Hf and Sn, and (b) powder one at temperatures of not more than about 1100 OC melting, vitreous material. 2. Mass according to claim 1, characterized in that the glass-like Material of at least one oxide of an element selected from those consisting of Bi, B, Pb and W. Group that is meltable at temperatures of about 400-1000 "C. 3. Composition according to claim 1 or 2, characterized in that the amount of the vitreous material in the range of about 1-30% by weight on the weight of the perovskite compound. 4. Composition according to claim 1, characterized in that it is a perovskite compound contains, which has been produced by a hydrothermal process. 5. Composition according to claim 1, characterized in that it is a perovskite compound contains, which has been produced by a metal alkoxide process. 6. Composition according to claim 1, characterized in that it is a perovskite compound contains, which has been produced by a mixed precipitation process. 7. Composition according to claim 4, characterized in that it is a perovskite compound which has been obtained by a hydrothermal reaction which comprises: (a) Carrying out a hydrothermal reaction in an aqueous reaction medium on a mixture of a hydroxide of at least one A group element from the Mg, Ca, Sr, Ba and Pb and a hydroxide of at least one B group element from the group consisting of Ti, Zr, Hf and Sn; (b) adding an insolubilizing agent Means to the reaction mixture obtained for the insolubilization of water-soluble, Compounds of the unreacted A group element dissolved in the aqueous medium to adjust the ratio of the A group element to the B group element in a resulting compound to a desired A / B ratio; or (c) filtering, washing with water and drying the resulting reaction mixture for obtaining a solid reaction product, dispersing the reaction product in an aqueous medium to form a slurry, adding a water-soluble one Adding the A group element to the slurry and then adding an insolubilizing agent Means to the slurry to insolubilize the water-soluble compound of the A group element to set the ratio of the A group element to the B group element in an emerging compound to a desired A / B ratio; and (d) filtering, washing and drying the resulting mixture to provide the perovskite compound with the desired A / B ratio. 8. The mass of claim 1, characterized in that the mass continues at least one additive selected from among B, Bi, alkaline earth metals, metals the group consisting of rare earths, transition metals, Si and Al. 9. A method for producing a ceramic dielectric, thereby characterized in that it comprises: sintering at temperatures not greater than about 1100 ° C of a mixture of: (a) Particles consisting essentially of a practically cubic perovskite compound and essentially one particle size of no more than about 1 µm, with the perovskite compound at least an A group element of the group consisting of Mg, Ca, Sr, Ba and Pb and at least contains a B group element of the group consisting of Ti, Zr, Hf and Sn, and (b) Powder of a vitreous one which melts at temperatures not exceeding about 1100 OC Materials. 10. The method according to claim 9, characterized in that as a vitreous Material at least one oxide fusible at temperatures of about 400-1000 OC an element selected from the group consisting of Bi, B, Pb and W is used. 11. The method according to claim 9, characterized in that the glass-like Material is used in such an amount that it is in the mixture in the area from about 1-30 weight percent based on the weight of the perovskite compound. 12. The method according to claim 9, characterized in that the perovskite compound has been produced by a hydrothermal process. 13. The method according to claim 9, characterized in that the perovskite compound has been prepared by a metal alkoxide process. 14. The method according to claim 9, characterized in that the perovskite compound has been produced by a mixed precipitation process. 15. The method of claim 9, wherein the perovskite compound according to a hydrothermal reaction, characterized in that: (a) a mixture of a hydroxide of at least one A group element selected from that of Mg, Ca, Sr, Ba and Pb and a hydroxide of at least one B group element from the group consisting of Ti, Zr, Hf and Sn of a hydrothermal reaction in is subjected to an aqueous reaction medium; (b) an insolubilizing one Agent is added to the resulting reaction mixture to put in the aqueous medium dissolved, water-soluble compounds of the unreacted A group element to insolubilize to the ratio of the A group element to the B group element adjust to a desired A / B ratio in an obtained compound; or (c) the reaction mixture obtained is filtered, washed with water and dried is to obtain a solid reaction product, the reaction product in one aqueous medium is dispersed to form a slurry, to the slurry a water-soluble compound of the A group element is added and then to an insolubilizing agent is added to the slurry to make it water-soluble To insolubilize compound of the A group element and the ratio of the A group element to the B group element in a compound obtained to a desired A / B ratio to discontinue; and (d) the resulting mixture is filtered, washed and dried to obtain the perovskite compound with the desired A / B ratio. 16. Ceramic dielectric, characterized in that it is produced has been made by sintering at temperatures no greater than about 1100 oC Mixture of: (a) particles consisting essentially of a substantially cubic Perovskite compound exist and essentially have a particle size of no more than about 1 µm, the perovskite compound having at least one A group element the group consisting of Mg, Ca, Sr, Ba and Pb, and at least one B group element the group consisting of Ti, Zr, Hf and Sn, and (b) powder one that melts at temperatures not exceeding about 1100 OC Materials. 17. Ceramic dielectric according to claim 16, characterized in that that the vitreous material at least one at temperatures of about 400-1000 OC fusible oxide of an element selected from the group consisting of Bi, B, Pb and W, is. 18. Ceramic dielectric according to claim 16 or 17, characterized in that that it has been made from a mixture containing the vitreous material in an amount of about 1-30% by weight, based on the weight of the perovskite compound, contains. 19. Use of the compositions according to any one of claims 1 to 8 for production a ceramic dielectric.