MXPA00012848A - Barium titanate dispersions - Google Patents

Abstract

The invention provides slurries, dispersions, or slips of barium titanate-based particles in a non-aqueous medium and methods of their production. The particles have a coating comprising a metal oxide, metal hydrous oxide, metal hydroxide or organic acid salt of a metal other than barium or titanium. At least 90 percent of the particles have a particle size less than 0.9 micrometer when the coated particles are dispersed by high shear mixing.

Description

DISPERSIONS OF BARITO TITANATE Field of the Invention The present invention relates to dispersions of barium titanate and, more particularly, to dispersions of barium titanate in a non-aqueous medium.

Background of the Invention Ak The superior dielectric constant of materials based on barium titanate, make them suitable for multilayer ceramic capacitors, commonly referred to as "MLC's". MLC's comprise alternative layers of dielectric and electrical conductive materials. U.S. Patent Nos. 3,612,963 and 4,435,738 describe examples of MLC's. Palladium, silver, palladium-silver, copper and nickel alloys are common electrical conductive materials used in MLC's. The layers • Dielectrics of an MLC, usually are prepared from a dispersion of superior solid, known in the art as a "detachment". Said landslides normally comprise material based on barium titanate powder and a polymeric linker in an aqueous or non-aqueous solvent. Bond-stabilized powder films made by casting or coating with a release are dried to provide a layer of colored ceramic dielectric material "green". The green layers are coated with conductive materials in a pattern, and are subsequently stacked to provide a lamination of alternating layers of dielectric material and green ceramic conductor. The piles are cut into cubes of MLC, which are heated to burn organic materials such as linker and dispersant, and then ignited to sinter particles of material based on barium titanate to form a capacitor structure with laminate, layers of material Dielectric and dense ceramic conductor. The sintering temperatures are usually within the range from about 1000 ° C and 1500 ° C. During sintering, the increased density of ceramic dielectric material is achieved as a result of the fusion and consolidation of the particles to form grains. Even with the use of grain growth inhibitors, the size of the ceramic grain in a layer dielectric MLC, is usually larger, for example, by a factor of 3 to 5, than the size of the original primary particles. In addition, all porosity is not removed during the sintering process. Normally, between approximately 2% and 10% porosity remain in the MLC dielectric layers. These pores, or hole defects, in the dielectric layer, tend to be larger in larger grain size ceramics. Certain critical capacitor properties such as DC voltage and dispersion are influenced by dielectric thickness, grain size and porosity defects. By For example, it is considered that the effective dielectric layers need to be of several grain thicknesses, for example at least 3 to 5 grain thicknesses. Because a defect in any of the layers of an MLC can be fatal to its performance, the MLC's are manufactured with a sufficient dielectric layer thickness to effectively reduce the impact of ceramic defects which can be caused by random large grains or pores, which adversely affect the properties of the MLC.

With the demand that exists in the market to miniaturize the design of electronic devices, there is a need in the MLC industry for ceramic materials that will allow thinner dielectric layers without incurring the catastrophic effects of large grains and pore sizes relative to the thickness dielectric.

Barium titanate powders produced by known processes, for example calcination or hydrothermal processes, have large particles and / or fine particles agglomerated in resistant form of a size substantially greater than 1 miera. These particles and agglomerates are not easily manageable for the production of MLC's with ultra thin dielectric layers of fine granules, for example, less than 4-5 microns. Therefore, it could represent an advance in the art, providing a material based on barium titanate, and dispersion, which would be suitable for making MLC's with thinner dielectric ceramic layers of, for example, less than 4 microns, with acceptable electrical properties or exceptional, including CD dispersion and disruptive stress without the need for extended ball grinding.

»Adding it from Invention 5 In one aspect, the present invention provides a paste, dispersion or release comprising particles based on barium titanate dispersed in a non-aqueous medium. The particles include a coating comprising a metal oxide, oxide hydrous metal, metal hydroxide or an organic acid salt of a metal other than barium or titanium, where at least 90% of the particles have a particle size of less than 0.9 micrometers, when they are dispersed by the upper cut mixture. As used in the present invention, the term "based on in barium titanate ", refers to barium titanate, barium titanate having another metal oxide coating, and other barium and titanate-based oxides having the general structure ABO3, wherein A represents one or more divalent metals such as barium, calcium, lead, strontium, magnesium and zinc, and B represents one or more tetravalent metals such as titanium, tin, zirconium and hafnium. In another aspect, the present invention provides a method for forming a paste, dispersion or release. The method includes the step of dispersing particles based on barium titanate in a non-aqueous medium, by means of superior cutting mixture until 90% of the particles have a particle size less than 0.9 microns. The particles have a coating comprising a metal oxide, a hydrous metal oxide, a metal hydroxide or an organic acid salt of a metal other than barium or titanium. In another aspect, the present invention provides another method for forming a paste, dipping, or stripping. The method includes the formation of a paste of particles based on barium titanate in an aqueous medium through a hydrothermal process. The method further includes the formation of a coating on the particles, including a metal oxide, a hydrous metal oxide, a metal hydroxide, or an organic acid salt of a metal other than barium or titanium. The method further includes replacing the aqueous medium with a non-aqueous medium, and dispersing the particles based on barium titanate in a non-aqueous medium by means of a top-cut mixture.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 A, 1 B and 1 C are graphs of the particle size distribution of a modality of the barium titanate particles of the present invention, after top-cutting mixing for 45 minutes. minutes, after further mixing in a medium horizontal mill for 30 minutes, and after further mixing in a medium horizontal mill for 45 minutes; and Figures 2A and 2B are graphs of the particle size distribution of another embodiment of the barium titanate particles of the present invention, after upper cut mixing for 10 minutes, and after superior cutting mixing for 30 minutes. Other new features and aspects of the present invention will be appreciated, from the detailed description of the present invention that is presented below, when this is considered in conjunction with the accompanying Figures, and from the appended Claims.

Detailed Description of the Invention The present invention is directed to pastes, dispersions or detachments of particles based on barium titanate dispersed in a non-aqueous medium. The particles include a coating on at least a part of the surface of the particle. The coating comprises a metal oxide, a hydrous metal oxide, a metal hydroxide, or an organic acid salt of a metal other than barium or titanium, or mixtures thereof. The coated particles have a particle size of less than 0.9 microns when they are dispersed by a top-cut mixture. The barium titanate-based particles can be dispersed, without the need for ball milling, into submicron dispersions in a non-aqueous medium, which is convenient in the manufacture of MLC's without thin dielectric layers having submicron grain sizes. and a higher disruptive voltage.

Top-cut mixing is effective in reducing the size of particle agglomerates based on barium titanate, and comprises the deagglomeration or separation of agglomerates into smaller coated particles without ball milling, which includes the impact of the particles with media of hard ball milling, such as rods, ball particles or similar zircons. Since the ball grind can divide the particles into a size smaller than the size of the primary particle resulting in particles not equiaxially shaped with an uncoated surface (s), exposed, in a preferred embodiment the particles of the present invention are not ball milling and the particles have a main part of the surface coated by the coating. In another aspect of the present invention, the unground particles are split in equiaxial or spherical form. The barium titanate-based particles are useful for providing monolithic capacitors comprising a ceramic body having a grain size of less than 0.3 microns. Preferred MLC's exhibit a temperature capacitance coefficient X7R or Y5V, and have a dielectric thickness of less than 5 microns and a dielectric strength of at least 50 volts per meter. The size of the primary particle of particles based on barium titanate can be determined by methods known to those skilled in the art. Examples of such methods use an electron scattering microscope (SEM) or an electron transmission microscope (TEM). While it is understood that the barium titanate-based particles may comprise primary particles of various sizes, the coated barium titanate-based particles have an average primary particle size of less than 0.6 microns. Preferably, the particles have a primary particle size less than 0.5 microns; more preferably, less than 0.4 microns; and more preferably, the particles have a primary particle size less than 0.3 microns; more preferably, the particles have a primary particle size of less than 0.2 microns. Barium titanate-based particles can exist in forms other than the primary particles, for example in the form of aggregates of primary particles, and / or agglomerates of primary particle aggregates. The SEM and TEM methods are not effective in distinguishing the size distribution between primary particles, aggregates of primary particles, and agglomerates of aggregates of primary particles. Particle size distribution analysis, for example through light scattering techniques, is a preferred method for particle size characterization of particles based on barium titanate, provided that the preparation for the analysis is not include a treatment that could change the distribution of the aggregated or agglomerated particles, such as by deagglomeration due to an ultrasonic treatment, mixing of upper cut or ground. Said automatic light scattering technique employs a HORIBA LA-910 ™ laser light scattering particle size analyzer or similar apparatus. Said analyzes usually present the volume fraction, normalized for frequency, of independent particle sizes including primary particles, aggregates and 5 agglomerates in ten groupings or deciles. Therefore, as used in the present invention the term "particle size" refers to individual particles in the powder and can include primary particles, aggregates of primary particles, agglomerates of aggregates, and mixtures thereof. . In one aspect of In accordance with the present invention, at least 90% of the particles based on barium titanate, coated with metal oxide in a particle dispersion based on barium titanate, have a particle size of less than 0.8 microns; and preferably, less than 0.7 microns; more preferably less than 0.6 microns. In more aspects Preferred of the present invention, at least 90% of the particles in a barium titanate dispersion have a particle size of less than 0.5 microns; preferably, less than 0.4 microns; and more preferably, less than 0.3 microns. The characteristics of the particle size distribution include D90, which is the smallest particle size in the largest particle decile; D50, which represents the median diameter; and D-io, which is the largest particle size in the smallest particle decile. The D90 / D10 ratio is a convenient feature to identify the width of the curve particle size distribution. In various aspects of the present invention, the particle size distribution is narrow, preferably has a Dgo / D-io ratio less than 4, more preferably, the D90 / D ratio is less than 3; and more preferably the proportion of D90 / D? 0 is less than 2.5. As used in the present invention, the term "Dispersion" refers to two phase systems of solid particles suspended in a non-aqueous medium. In a preferred embodiment, the stability of the dispersion or the resistance of the solid particles suspended for settlement can be increased by the use of a dispersing agent. Except when the context is clear that only significant metal oxide, as used in the present invention, the term "metal oxide" is used to describe metal oxide coatings, metal hydroxides, metal oxides, hydrous metal, and organic acid metal salts. Said organic acid salt can be converted to an oxide or hydroxide, by • example by thermal decomposition which occurs during heating to burn the ceramic linker and / or sinter the ceramic. As used in the present invention, the term "top-cut mixing" means mixing in a liquid medium that imparts sufficient energy to separate the agglomerates of the coated particles into smaller particles, without the impact of a solid agent. such as rods, cylinders or hard spherical media, such as zirconia spheres. Hard media is used in certain top-cut mixing equipment, when the medium-sized medium is used to create a cut without impact. Although high-cut mixing can be effected through various equipment, as will be described later, it is difficult to precisely define the force applied to separate the agglomerates in the upper cutting mix. As defined above, the term "based on barium titanate" refers to barium titanate, barium titanate having another metal oxide coating, and other oxides based on barium and titanate having the general structure AOB3, in where A represents one or more divalent metals such as barium, calcium, lead, strontium, magnesium and zinc, and B represents one or more tetravalent metals such as titanium, tin, zirconium and hafnium. A preferred barium titanate-based material, which can normally be used in Y5V applications, has the structure Ba (- |. X) A? O * Ti (iy) By O2, where X and Y can be within the range of 0 to 1, wherein A represents one or more divalent metals other than barium such as lead, calcium or strontium, and B represents one or more tetravalent metals other than titanium such as tin, zirconium and hafnium. When the other metals are present in the form of impurities, the value of X and Y will be small, for example less than 0.1. In other cases, another metal or metals may be introduced to provide a significantly identifiable compound such as calcium-barium titanate, strontium-barium titanate, zirconate-barium titanate, and the like. In still other cases, when X or Y is 1, the barium or titanium can be replaced by another suitable valence metal to provide a compound such as lead titanate or barium zirconate. In still other cases, the compound may have multiple partial substitutions of barium or titanium. An example of a multiply partial substitute composition is represented by the structural formula Ba (1.? X '.? ") PbxCaX'SrX" O'Ti (i.y.y'.y ") SnyZry? Fy" O2 where x, x ', x ", y, y', y y", are each > that 0, y (x + x '+ x ") is < that 1, y (y + y' + y") is < what 1 In many cases, the material based on barium titanate will be placed with a perovskite crystal structure, and it is preferred that the barium titanate material have a perovskite structure. Although the barium titanate particles produced in hydrothermal form are conventionally dried in powders, the particles are formed into agglomerated particles in a relatively resistant form which are not effectively deagglomerated by simple top-cutting mixing. Dispersions made from said agglomerated, dried barium titanate-based particles, which have a primary submicron particle size, require a substantially long duration of impact milling to provide particles within the range of microns, and the longer the grinding of the submicron particles is more intense. In contrast, agglomerated metal oxide-coated barium titanate-based particles, having a primary particle size of submicrons, can be deagglomerated for the submicron size range of the coated particles through moderate mixing action. Superior cutting of pastes, dispersions or detachments comprising said particles in a non-aqueous medium. The pastes, dispersions or nonaqueous detachments of particles based on barium titanate of the present invention can be prepared from particles based on titanate Barium produced in hydrothermal form, are maintained in an aqueous environment such as an aqueous paste, at least until the particles are supplied with a coating, after which, the aqueous phase is replaced with a non-aqueous phase, such as it will be described further below. A particle paste based on submicron barium titanate can be prepared by a hydrothermal process, for example as described in US Pat. Nos. 4,822,939; 4,829,033; and 4,863,833. In this hydrothermal process, an excessive amount, above about 20 moles of The excess percentage of the barium hydroxide solution is usually added to a hydrous and heated titanium oxide paste, usually at a temperature in the range of about 100 ° C to 200 ° C, to create submicron particles with crystalline structure of perovskite. The particle size and the The particle size distribution can be manipulated by controlling different variable processes, such as paste temperatures and solutions, range of addition, and range of heating and cooling range from the perovskite formation temperature. The selection of the process variables for a desired particle product can be easily determined by those skilled in the art following the general principles of crystallization. For example, the larger particles may be prepared by adding barium hydroxide relatively more slowly to a pulp maintained at a relatively low temperature, for example about 35 ° C; while the smaller particles can be prepared by adding barium hydroxide relatively more rapidly to a pulp maintained at a relatively high temperature, for example about 95 ° C. Good agitation is important to prepare uniform particles. Once the perovskite structure is imparted to the barium titanate particles by thermal treatment of a paste, the particles are preferably washed to remove non-reactivated metal species such as barium ions. The washing can be carried out with ammonia-deionized water at a pH of 10 to avoid dissolving the barium of the particles. The washing water can be removed by filtering or decanting the settled particles. The number of wash cycles, will be determined through the desired purity in the aqueous phase, such as to provide a paste with a low ionic strength having a conductivity of less than 5 milliSiemens, preferably less than 1 milliSiemens. It has been found that four to five wash cycles are suitable for reducing the ion content of the water phase to a low level characterized by a conductivity no greater than about 100 microSiemens. The barium titanate particles can be maintained in an aqueous state until after the coating process. As mentioned above, particles based on barium titanate can include a coating comprising an oxide, a hydrous oxide, a hydroxide or an organic acid salt of at least one metal other than barium or titanium. Coated ones can be provided by adding to a stirred paste of particles based on barium titanate, an aqueous solution (s) of salts, such as nitrates, borates, oxalates, and the like, of metals corresponding to the desired coating. The precipitation for the coating is promoted by an appropriate pH. The salt solutions can be added either in the form of a salt mixture to form a homogeneous single layer coating, or consecutively separated to form layers Individual oxide, hydrous oxide, hydroxide or organic acid salt. In the case of metals of relatively higher solubility, such as cobalt and nickel, the oxide-coated ones tend to be more difficult to apply and to be maintained without resolubilization. Therefore, it is often preferred to apply oxide coatings to these more soluble metals in the form of a top coating on the deposited metal oxide layers more easily. An alkaline environment also minimizes the solubilization of barium and easily provides particles with a titanium and barium free coating. The particle coatings intended for the application of ceramic capacitor typically have a thickness of less than 10% of the diameter of the particle, often less than 20 nanometers thick and preferably not greater than between 5 nanometers and 10 nanometers thick. 4fc Useful organic acid salt coatings include which are organic salts of metals that have a low solubility. Examples of such organic acid salt coatings are metal salts of oxalic acid (eg, niobium oxalate), citric acid, tartaric acid and palmitic acid. It is considered that the organic acid salt will be converted to a metal oxide during the burner of the linker. The metal selection is made based on the increase imparted to the processing or ownership of the MLC's. He F metal in coated, is usually selected from bismuth, lithium, magnesium, calcium, strontium, scandium, zirconium, hafnium, vanadium, niobium, tantalum, tungsten, manganese, cobalt, nickel, zinc, boron, silicon, antimony, tin, trio, lanthanum, lead, and the elements of Lantanida. Preferably, the barium titanate particles have a barium and titanium free metal oxide coating. When ceramic capacitors with X7R dielectric properties are desired, it is useful to supply the barium titanate particles with dopantings such as niobium oxide, tantalum oxide, or neodymium oxide, in combination with nickel oxide, or cobalt oxide. When it is desired to provide ceramic capacitors that are sintered at relatively low temperatures, for example within the range of about 1000 ° C and 1200 ° C, compared to about 1300 ° C and 1600 ° C, it is useful to supply the barium titanate particles with a dopanto that promotes sintering at low temperature. Said low temperature sintering aids include bismuth oxide, zinc oxide, zinc borate, zinc vanadate, lithium borate and combinations thereof. The sintering metal oxides with temperature reduction and dielectric modification can be effectively added to the particles based on barium titanate after the particles have been washed and before the formation of the dispersible wet paste. After the coating is applied to the barium titanate-based particles produced in hydrothermal form, the paste can be washed and the content of the paste can be reduced to provide a concentrated paste, a wet paste or powder. In addition, the wet paste or powder can be treated with a dispersing agent to provide a dispersion and can be further treated with a linker and other additives to provide a release. The water is preferably removed by means of avoiding or at least minimizing information of agglomerated particles in a resistant form., such as in calcination. Because they are not calcined or dried, certain metal oxide coated ones may tend to remain in the form of a hydrated metal oxide, which can be soluble if it is not kept at a near pH for the minimum solubility for said oxide. metal. For example, nickel oxide or cobalt oxides tend to be somewhat soluble if they are not maintained at a pH close to 10. Therefore, to maintain a properly coated particle, the pH of an aqueous component is preferably maintained within the range from 9 to 1 1. The aj particles of particles based on barium titanate coated by Oxides of metal are conveniently produced at a relatively low solid level, for example less than 30% by weight of particles based on barium titanate. A higher solids level is normally preferred for the production of MLC's. Therefore, in the case where a paste of the present invention will be used directly in the manufacture of MLC's, it is useful to concentrate the paste, for example by stirring the water as by F filtration, up to at least 40% by weight of solids; preferably at least 50% by weight of solids; more preferably at least 55% by weight of solids; and even more preferably within the range of at least about 60 or 75% by weight solids. A dispersing agent or linker can be added to the concentrate paste to provide a stable release or dispersion of the particles based on barium titanate.

As noted above, once the particles based on barium titanate have been coated, the aqueous phase can be replaced with a non-aqueous phase. The aqueous phase can be replaced with an organic liquid phase by solvent exchange or distillation. In the solvent exchange process, a filtration apparatus can be used. In a preferred embodiment, the filtration apparatus is a Funda ™ filter that includes flat trays, delineated with an ultrafiltration membrane, which are mounted on a support tube central. The liquid flows through the FU N DA ™ filter, and is removed through this central support tube. Once the filtration operation is finished, the filter paste is centrifuged from the trays using centrifugal force. Subsequently, the solids fall through a valve to the next processing step. He ultrafiltration membrane material, is used due to the size of the submicron particle of hydrothermal barium titanate. In operation, the solvent exchange process first comprises pumping an aqueous paste of barium titanate particles into the filter apparatus. Water is removed through of the ultrafiltration membrane. Once most of the water has been removed, an organic solvent lacking anhydrous water, such as methyl ethyl ketone (MEK) or toluene (to be described later), is introduced into the filter apparatus. This solvent that lacks water, is added and removed from the filter apparatus through the ultrafiltration membrane material, until the water content of the barium titanate filter paste decreases to a desired value. Once the water has been removed from the filter paste using the solvent soluble in water, a solvent not soluble in water is added. Sufficient amount of water-insoluble solvent is added and removed through the ultrafiltration material to dilute the concentration of the water-soluble solvent to a desired value. Subsequently, the barium titanate is centrifuged from the ultrafiltration material, and is poured into a mixing tank placed under the filter apparatus. Once the barium titanate enters the mixing tank located below the filter apparatus, a dispersant is added and the contents of the container mixed until a homogeneous paste is obtained. Designates, such as activated alumina, can be added if a low water content is desired. The dispersed paste is subsequently pumped for grinding and packing. Another method to achieve solvent exchange is through a distillation process. The process comprises a mixed bath distillation plug, a condensing heat exchanger, and a phase separation tank. In operation, the aqueous barium titanate paste is pumped into the distillation tank, and the desired organic solvent is added. If the desired organic solvent is not miscible in water, you can add a small amount of solvent miscible with water, such as a high molecular weight alcohol. Subsequently, the components are mixed for an emulsion and heated. The dissoliation process is preferably used with high molecular weight solvents, which have a higher boiling point than water. The heating of the mixture removes the water selectively leaving the barium titanate dispersed in the organic medium. The phase separation tank, located in the downstream of a condensing unit, separates the water from any solvent, which could also be removed during the distillation. Subsequently, the solvent is pu back to the distillation vessel, and the water is pu to waste. A vacuum could also be used with the phase separation tank to force the distillation to occur at a lower teature. During the distillation process, the dispersant can be added to prevent the paste from solidifying in the distillation bottle. Once the desired water content is achieved, the solvent is no longer recycled, and then the mixture is concentrated by distillation to achieve the desired percentage of solids. Similar to the ultrafiltration process described above, if a low water content is desired, the mixture in the distillation tank can be fed through a bed containing a desicant, such as activated silica or activated alum. It will also be noted that the thermodynamic efficiency of the distillation process can be improved by adding a downstream to the ultrafiltration modules to feed the aqueous barium titanate paste into the distillation tablet. These ultrafiltration modules would remove most of the water from the aqueous barium titanate paste, before being introduced to the distillation process. A non-aqueous paste can also be concentrated, for example by filtration, to provide a solid wet paste, which is a non-flowing solid comprising particles based on barium titanate coated with oxide and liquid. A non-aqueous wet paste may be in a solid state with about 60% by weight of solids mixed with a non-aqueous solution. More preferably, the wet pulp will comprise at least 65% by weight of solids; and more preferably, at least 70% by weight of solids. The wet pulp may comprise up to about 85% by weight solids. In a non-aqueous wet paste the non-aqueous solution must have a pH greater than 8 to inhibit the dissolution of metal. A preferred pH range is between about 8 and 12; more preferably, the pH range is between about 9 and 11. The wet paste of particles based on barium titanate is a colloidal dispersion precursor. That is, the wet paste can be dispersed, for example by mixing it with a dispersing agent. It requires a bit of an additional liquid medium to transform a wet paste from a solid state to a fluid dispersion. At least in the case of the non-aqueous wet pulp, the particles in the pulp will remain agglomerated in a weak manner for a relatively long time, as long as the pulp is maintained with a liquid content of at least 15% by weight; more preferably as long as the pulp is maintained with a liquid content of at least 20% by weight; and more preferably, as long as the pulp is maintained at a liquid content of at least 25% by weight. Preferably, the wet paste is encapsulated in a moisture barrier to inhibit the loss of water content, which could promote the formation of agglomerated particles in a resistant form, which are not easily deagglomerated. said moisture barrier, such as polyethylene bags, or fiber drums coated with polyethylene, can provide an extended shelf life of at least one day or more; preferably, an extended shelf life of at least 3 days; more preferably, an extended shelf life of at least 30 days; and more preferably, a shelf life extended for at least 90 days. These characteristics facilitate the storage and transportation of the wet paste modality F of the present invention. The wet paste is easily transformed into a fluid dispersion, incorporating in the paste a dispersing agent without a significant fluid addition. Although fluid can be added to the pulp, the amount of dispersing agent required to transform a solid pulp into a fluid dispersion is remarkably small, for example usually less than 2% by weight, based on the weight of the titanate-based material. of barium. In In some cases, an additional fluid other than the flow volume of the dispersing agent is not required to transform a wet paste into a fluid dispersion. The contemplated dispersing agents are polyelectrolytes which include organic polymers with anionic or cationic functional groups. Polymers functionalized in anionic form include carboxylic acid polymers, such as polystyrene sulfonic acid and polyacrylic acid; Polymers functionalized in cationic form include polyimides such as polyetherimide and polyethyleneimine. Polyacrylic acids are preferred for many applications. Although the polymeric acid groups can be protonated, it is preferable that said acid groups have a counter cation, which would prevent the reduction of dispersion pH to a level that would promote the dissolution of the barium species or other metal species, such as they would be present in dopanto-coated ones. For capacitor applications, a preferred cation is the ammonium ion. In some cases, it may be feasible to employ dopanto metals in the counter cation form for the polymeric acid dispersant. Without taking into account the selected dispersion agent, the appropriate amount of dispersing agent can be easily determined by those skilled in the art, through a grinding process. When the amount of dispersion agent selected is the amount that provides the lowest viscosity for the dispersion, the concentration of dispersing agent can be reduced in the use of the dispersion, such as by dilution or interaction with additives, to cause the viscosity rises to an undesirable high level. Therefore, for many applications it is desirable to employ a "viscosity minimizing amount" of dispersing agents. It has been found that a preferred dispersion agent for use in colloidal d ispersions intended for capacitor applications and for such testing will be an ammoniated polyacrylic acid having a number average molecular weight of about 8000. For example, has discovered that 0.75% by weight of said polyacrylic acid ammoniated (such as 40% by weight of aqueous solution), it will be useful to transform the wet paste into a liquid dispersion. The incorporation of the dispersing agent can be carried out by suitable means, such as dispersant mixture mechanically in the wet paste. When the mixing of In the upper cut, the excess dispersion agent is consumed through a new particle surface area exposed by f deagglomeration. Therefore, it is desirable to add dispersion agent in an increased manner in the course of upper cutting mixing. 20 Wet pulp differs from pulps, dispersions, slides and dry powders in that the wet pulp is a solid that does not flow, while the pulps, dispersions and slides are fluid liquids and the dry powders are flowing solids. Wet powders may or may not flow depending on the amount of liquid present. The more liquid is removed, the wet powder becomes progressively drier. However, it is understood that dry powder is not necessarily completely dehydrated. Spray drying, freeze-drying and vacuum-assisted drying at low temperature are preferred methods for providing dry powders of particles based on covered barium titanate, which remain in merely dispersible form by mixing them in a solution containing a dispersing agent, for example, with upper cut mixed aj. Therefore, the dry powders of Coated barium titanate-based particles are surprisingly dispersible in dispersions of submicron particles without the need for long-lasting impact grinding. Unlike the known materials, grinding of higher energy for several hours is not required to reduce the particle size to a point where the dispersions or detachments of the particles based on barium titanate, F can be used to make capacitors with thin dielectric layers in the form of fine grains and high-voltage d isruptive. Another aspect of the present invention provides methods to elaborate a dispersion of particles based on barium titanate coated with submicrons in a solution, deagglomerating a dispersion of large particles (greater than 1 miera), based on barium titanate, coated with weakly agglomerated metal oxide, until that substantially all the particles are minors to 1 miera. In a preferred method of the present invention, the higher solid dispersions, which comprise between about 30% by weight and 75% by weight of particles, are deagglomerated by top-cutting mixing with a dispersing agent. The optimum time for upper cutting mixing is easily determined through routine experimentation. The top cutting mixing can be carried out in a centrifugal pump deagglomeration mill, commercially available for example, in Silverson Machine I nc. (East Longmeadow, MA). Other useful devices for providing the deagglomerated dispersions include those which are known as supermolinos, colloid mills, and cavitation mills. The super-mills have a grinding chamber filled with a medium with high-speed rotating discs on a central shaft, and are commercially available for example at Premier Mili (Reading, PA). Colloidal mills have a grinding gap between the extended surfaces of a high speed rotor and a fixed stator, and are also commercially available for example in Premier Mili. In cavitation mills, which are commercially available for example in Arde Barinco I nc. (Norwood, NJ), the fluid is pumped through a series of rapidly opening and closing chambers, which rapidly compress and decompress the fluid, imparting a high frequency cutting effect that can deagglomerate the particles. It is expected that the paste, dispersions, wet paste, wet powder or dry powder, concentrates will work equally well at the time of providing detachments for the manufacture of high performance capacitors, depending on the facilities or methods to manufacture a single capacitor. f A test to determine the effective amount of dispersion agent for particles based on weakly agglomerated coated barium titanates, comprises the use of a top-cut mixer, such as a Silverson Model L4R top-cut laboratory mixer, equ ipado with a screen of áj upper cut and square hole to mix with upper cut a sample of 500 grams of a dispersion comprising 70% by weight of the coated particles in a non-aqueous alkaline solution at a temperature in the range between 25 ° C and 30 ° C, a pH at which the coating does not will dissolve, and which contains an effective amount of dispersing agent for an effective time of deagglomeration of coated particles. An effective amount of dispersing agent is sufficient to keep agglomerates and aggregates separated in the smaller particle sizes without agglomerating again. An effective amount of dispersing agent will vary depending on factors such as the size of the particles, the nature of the coating and the powder of the dispersing agent. An effective amount of dispersing agent and an effective time can be easily determined with some routine experiments performed by those skilled in the art, observing the effect of the variables, such as concentration of the dispersing agent and upper cutting mixing time, in reducing the magnitude of the particle size distribution. An effective amount of said variables will allow an analysis of the particle size that reflects the real effect of the upper cut mixing in the deagglomeration. It has been found that for many cases an effective amount of ammoniated polyacrylic acid dispersion agent (number average molecular weight of about 8000) is about 1% by weight of dispersion agent per total weight of dispersion agent particles. , and an effective upper cutting mixing time is approximately 1 minute. Barium titanate-based particles, coated, prepared by hydrothermal processes are substantially spherical and trimmed in an equi-axial fashion in appearance. Said particles remain substantially spherical at one after the reduction in size by mixing top cut. Occasionally, substantially spherical particles may be duplicated. It is rare that the occurrence of duplicate particles is desired. The use of spherical particles, compared to non-spherical ground powders, provides characterized powders with an exceptionally superior surface area, having a BET surface area of at least about 4m2 / g; preferably the spherical particles have a BET surface area of at least about 8 m2 / g, more preferably, the spherical particles have a BET surface area of at least 12 m2 / g.

Barium titanate particles coated with submicrons can be suspended with a wide variety of binders, dispersants and release agents, using non-aqueous solvents to provide ceramic melt slides. The barium titanate-based particles are dispersed in an organic solvent containing a dissolved polymeric linker and, optionally, other dissolved materials such as plasticizers, release agents, dispersing agents, separation agents, anti-approach agents and agents of wetting Useful organic solvents have low boiling points and include benzene, ethyl methyl ketone, acetone, xylene, methanol, ethanol, propanol, 1,11-trichloroethane, tetrachlorethylene, amyl acetate, 2,2,4-triethyl pentanodol. -1, 3-monoisobutyrate, toluene, methylene chloride, turpentine, ethyl alcohol, bromochloromethane, butanol, diacetone, isobutyl methyl ketone, cyclohexanone, methyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, n-alcohol octyl, benzyl alcohol, glycerol, ethylene glycol, benzaldehyde, propionic acid, n-octanoic acid, ethylacetate, butylbutyrate, n-hexane, and the like, and includes mixtures thereof and mixtures with water, such as methanol / water mixtures. In addition, various mixtures of azeotropic organic solvent have low boiling points that can be used as carrier vehicles. Solvent mixtures may include, for example, 72% trichlorethylene / 28% ethyl alcohol, 66% ethyl methyl ketone / 34% ethyl alcohol, 70% ethyl methyl ketone / 30% ethyl alcohol, 59% ketone of ethyl methyl / 41% ethyl alcohol, 50% ethyl methyl ketone / 50% ethyl alcohol, 80% toluene / 20% ethanol, 80% toluene / 20% ethyl alcohol, 70% toluene / 30% ethyl alcohol, 60% toluene / 40% ethyl alcohol, 70% isopropyl alcohol / 30% ethyl methyl ketone, 40% ethyl methyl ketone / 60% ethyl alcohol, and mixtures thereof. In addition to those described above, dispersants (deflocculants / wetting agents) useful in non-aqueous dispersions of barium titanate particles coated with submicron metal oxide, include for example, phosphate ester, glycol trioleate, ethoxylate, 2-amino-2-methyl-1 - Propane, Hiroxyethylimidazoline of its chemical wood pulp product, oleic hydroxyethylimidazoline, fatty acids such as glycerol trioleate, lanolin fatty acids, poly (vinyl butyral), sodium bis (tridecyl) sulfosuccinate, diisobutyl sodium sulfosuccinate, sulfosuccinate sodium dioctyl, ethoxylated alkylguanidine amine, sodium dihexylsulfosuccinate, sodium diisobutylsulfosuccinate, benzenesulfonic acid, oil soluble sulfonates, poly (ethylene glycol) alkyl ether, ethylene oxide adduct of oleic acid, sorbitan trioleate, ethylene oxide adduct of steric acid amide, polyaryl alkylaryl alcohols, ethyl ether of poly (ethylene glycol), phenyl ethyl glycol, polyoxyl acetate Ethylene, polyoxyethylene ester, and the like. Preferred dispersing agents for suspensions of organic solvents and detachments include fish oil, corn oil, polyethyleneimine, and polyacrylic acid ammoniated. Among the polymeric bonding materials useful in non-aqueous detachments, for example, are poly (vinyl butyral), poly (vinyl acetate), poly (vinyl alcohol), cellulosic polymers such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, cellulose methylhydroxyethyl, cellulose acetate butyrate, nitrocellulose, acryl polypropylene, polyethylene, silicone polymers such as Poly (siloxane methyl) and poly (silyxane methylphenyl), polystyrene, butadiene / styrene copolymer, poly (vinyl pyrollidone), polyamides, polyethers, poly (ethylene oxide-propylene oxide), polyacrylamides, and acrylic polymers such as polyacrylate sodium, poly (methyl acrylate), poly (methyl methacrylate), polyacrylate esters, and Copolymers, such as copolymers of ethyl methacrylate and methyl acrylate, poly (vinyl alcohol), poly (vinyl chloride), vinyl chloride acetate, poly (tetrafluoroethylene), poly (α-methylstyrene), and the like. Polymer linkers are usually useful in the range of from about 5 to 20% by weight. A polymer The commercially available preferred is the acrylate polymer ACRYLOI D ™ B-7 (Rohm &Haas Co., Philadelphia, PA). Frequently, the organic medium will also contain a small amount of plasticizer to lower the glass transition temperature (Tg) of the linker polymer. The choice of The plasticizers are mainly determined by the polymer which must be modified and may include phthalate esters (and mixed phthalate esters) such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, phthalate dioctyl, benzyl butyl phthalate, alkyl phosphates. , poly (alkylene glycol), polyethylene glycol, glycerol, poly (ethylene oxides), hydroxyethylated alkyl phenol, dialkyl dithiophosphonate, poly (isobutylene), butyl stearate, methyl abietate, tricresyl phosphate, dipropyl glycol dibenzoate, and Similar. In one embodiment, a release based on an organic JE solvent of the present invention, comprises 100 parts per weight of particles based on barium titanate: 25 to 40 parts of organic solvent, 2 to 5 parts of dispersing agent, 5 to 20 parts of polymeric linker, and 0 to 15 parts of plasticizer. 15 The dispersion of particles based on barium titanate in different non-aqueous solvents can be promoted with the F application of several coatings, such as coupling agents to the surface of the particles. The wide range of available silane coupling agents provide, in particular, a means for adapting the surface of the particle to the carrier vehicle of choice. The coating of particles based on barium titanate derived hydrothermally with a silane coupling agent, they could be useful not only for dry powders, but also for the particles that remain in the solution. Although the silane coupling agents can be applied to the surface of the powders with or without drying process, the coupling agent would be preferably applied after drying the particles to aid in their dispersion in the carrier vehicle. In addition, drying the powders provides an easy mechanism for determining whether a complete coating is achieved by attempting to disperse the treated powder in water. Uncoated or partially coated powders will be completely or partially dispersed in water, while fully coated particles will float on the surface of the water even with agitation. The particles can be coated in a carrier vehicle and subsequently transferred to another carrier vehicle, by means of solvent exchange processing (as described above), or by a distillation process. Although silane coupling agents can be applied to the surface of the powders before or after a solvent exchange, it is preferable to apply the coating after solvent exchange processing. Silane coupling agents can be adhered to a particle surface, to aid dispersion in a desired carrier vehicle, and to assist in appeasing the surface of the particle. The general formula of an organosilane, RnSiX (.n), shows two kinds of functionality. The group X, is included in the reaction with the inorganic substrate. The bond between X and the silicone atom in coupling agents is replaced by a bond between the inorganic substrate and the silicone atom. X is a hydrolyzable group, usually alkoxy, acyloxy, amine or chlorine. The most common alkoxy groups are methoxy and ethoxy, which provide methanol and ethanol in the form of by-products during coupling reactions. Since chlorosilanes generate hydrogen chloride in the form of a by-product during coupling reactions, they are generally less used than alkoxysilanes. R is a non-hydrolysable organic radial that has a functionality that makes it possible for the coupling agent to bond with resins and organic polymers. Most widely used organosilanes have an organic substituent. In most cases, the silane is subjected to hydrolysis before surface treatment. After the In the case of hydrolysis, a reactive silanol group is formed, which can be condensed with other silanol groups, for example those which are on the surface of silicon fillers, to form siloxane bonds. The stable condensation products are also formed with other oxides such as those of aluminum, zirconium, tin, titanium and nickel. Less stable bonds are formed with boron, iron, and carbon oxides. The alkali metal oxides and carbonates do not form stable bonds with Si-O-. Water for hydrolysis can come from several sources. HE It can be added, it can be present on the surface of the substrate or it can come from the atmosphere. The reaction of these silanes comprises the four steps shown below, with a hydrolysable trimetoxy group X. 1 . Initially, the hydrolysis of the three responsible X groups adhered to the silicone RSi (OMe) 3 + 3H2O R S i (OH) 3 + 3MeOH occurs 2. Condensation for the oligomers as indicated below: 10 R R R I I I 3RSi (OH) 3 - HO- Si-O-Si-0-S¡-OH + 2H2O I I I OM OH OH 3. Subsequently oligomers bind hydrogens with OH groups of the substrate: + 2HiO 4. Finally, during drying or curing, a covalent bond is formed with the substrate with concomitant loss of water. 25 R R R HO- S II- O-S i-0-S i¡.- OH? R R l l l l l l .0. .0 .0 OK- Si- O- SJ -? - Si- OH + 2H? O H H K K H K O O O H V V V I I I H- or l_ In the interface, normally there is only one bond from each organosilane silicone to the surface of the substrate. é The two remaining silanol groups are present either linked to other silicone atoms of the coupling agent or are in free form. With organic solvent based detachments, green ribbons can be formed on conveyor surfaces by methods known to those skilled in the art. Observe 15 for example, J. C. Williams on page 173 to 197 of the Publication of Ceramic Manufacturing Processes, Volume 9 of the F Treaty on Materials Science and Technology, Academic Press (1976), and in US Patent Nos. 3,717,487 and 4,640,905, which are incorporated herein by reference. In addition, there is a variety of techniques to convert the landslides into thin films, green layers and ceramics. It is considered that the dispersions of the present invention will find application, with minor modifications, by example in the selection of a preferred suspension medium and linker, in the dilution to a desired fluid viscosity, etc. , in several ceramic processes to make dielectric layers for MLC 's. Releases can be formed in the films by spraying, forming layers in a moving sheet from a cascade or die (such as a doctor blade) and other methods used in the MLC industry. When a sufficient quantity of the non-aqueous liquid is removed from the film, a cohesive solid "green" color film is provided, which can be coated on a pattern registered on one or both sides with a material The conductor or precursor of conductive material, such as ink containing fine particles of palladium, silver, nickel, or palladium and silver alloys. Such conductive inks may contain fine particles of metal and ceramic. The green film sheets are usually stacked, for example up to 250 layers or more, and are cut into cubes of MLC, which are ignited to burn the polimeric and dispersant linker, sintered to form a dense multilayer capacitor structure with dielectric layers of fine grain structure. The conductive metal applied to the ends, can connect the alternative conductive interlayers, forming the MLC. The unique properties of the particle size of the barium titanate-based particles of the present invention are expected to allow the production of new MLC's having ultrathin layers of dielectric ceramic having grains of submicras. These dielectric materials should facilitate significant increases in volumetric capacitance. In addition, it is expected that the MLC 's will have a high disruptive voltage not expected. The absence of large particles, for example greater than I microns, F should allow commercial production in high productions, for example greater than 98% of MLC's comprising multiple dielectric layers, for example greater than 40. The particles of the present invention are expected to be preferably used to produce MLC's that have a dielectric ceramic layer F with a maximum grain size of 0.9 microns or less; plus Preferably, the maximum grain size is less than 0.8 microns; more preferably, the grain size is 0.7 microns or less.

Other aspects of the present invention provide X7R or Y5V capacitors comprising more than 20 dielectric layers of material based on barium titanate, sintered in ceramic structure wherein said layers are less than 5 microns thick, for example within the range of 2 to 4 microns thick. A higher number of dielectric layers, for example 250 or 500, may be preferred, depending on the MLC design. Thin dielectric layers allow MLC 's to be used with a number increments of dielectric layers in an MLC or MLC's of standard size with a fixed number of layers, to fit in smaller size packages. The result is that the capacitance of the standard size MLC package can easily be increased by a factor of 5 to 10 or more.

To provide monolithic MLC's X7R, the particles used to make the dielectric layers are preferably coated with niobium, cobalt, nickel and manganese oxides. For the low fire capacity, for example sintering at less than 1200 ° C, a preferred metal oxide coating may also contain bismuth oxide. To achieve ultrathin dielectric layers with a thickness less than 4 microns, the particles preferably have a primary particle size less than 0.3 microns, more preferably within the range of 0.1 to 0.2 microns. A fine, uniform grain size, for example less than 0.3 micrometers, in ultra-thin dielectric layers provides a superior dielectric strength in excess of 100 volts per micrometer, and a low dissipation factor. These properties provide increased reliability for high voltage and high capacitance ceramic capacitors. The ability to provide thin dielectric layers has allowed the production of capacitors that have 5 to 10 times the capacitance for a standard box size. Said MLC's, preferably comprise a monolithic ceramic body, for example, of barium titanate composed of metal oxide, two groups of interdigitated electrodes buried in said body and extending respectively to the opposite ends of said body and two conductive terminations. contacting said two groups respectively at said opposite ends. MLC's with X7R characteristics, have a capacitance temperature coefficient in a temperature range from -55 ° C to 125 ° C, which does not vary more than ± 15% of the capacitance at 25 ° C. In a preferred aspect of the present invention, the ceramics in an MLC X7R have a grain size of less than 0.3 microns, and comprise from 93 to 98% by weight of the barium titanate-based ceramic and from 2 to 7% by weight of other metal oxides. The following examples are not intended to establish limitations for the scope of the present invention. EXAMPLE 1 To determine the dispersion effectiveness of particles based on barium titanate in a non-aqueous solvent, the lower ignition X7R particles derived in hydrothermal form, after drying are dispersed in a solution of 80 toluene / 20 ethanol with a phosphate ester dispersant. A wet paste of barium titanate derived hydrothermally by X7R formulated, containing 72% by weight of solids and 28% by weight of water, was dried at a temperature of 200 ° C in a rotary drying unit, with vacuum applied. 9,072kg. of the barium titanate particles derived in hydrothermal form by dry formulated X7R, and subsequently were mixed with 3.039 kg. (3041.8 grams) of a solvent mixture of 80 toluene / 20 ethanol to form a paste. Subsequently, the paste was mixed with a DISPERSATOR ™ top cut mixer (Premier Mili), for 45 minutes while 0.3628kg was added. of a phosphate ester dispersant RHODAFAC RS-410 T The particle size distribution of the resulting paste (Sample 1) was subsequently measured and the results are presented below and are polished F in Figure 1 A. Subsequently, the paste was mixed in a PREMI ER ™ horizontal medium mill for 30 minutes (Premier Mili). The particle size distribution of the resulting paste (Sample 2) was subsequently measured, and the results are presented below and are illustrated in Figure 1 B. 10 Subsequently, the pulp was mixed in a medium horizontal mill PREM I ER ™ for an additional 15 minutes (45 minutes total). The particle size distribution of the resulting paste (Sample 3) was subsequently measured and the results are presented below and are illustrated in Figure 1 C. The load final solids, was determined to be 78% by weight.

The above experimental results illustrate that X7R powder derived in dry hydrothermal form can be dispersed in a solvent mixture of 80 toluene / 20 ethanol, using a dispersant of phosphate ester. This demonstrates the ability to create a paste with particles having a ratio (D9o / D10) of less than 3 X7R powder derived hydrothermally in a non-aqueous solvent with the selection of an appropriate dispersant. It is considered that alternative solvents (such as, for example, those described above), with an appropriate dispersant, can be used to create pastes with particles having a ratio (D90 / D-10) of less than 3.

Although the results indicate that a wet paste of barium titanate derived in hydrothermal form by X7R formulated can be dried and dispersed again in a non-aqueous solvent to form a paste with particles having a proportion (D90 / D10) of less than 3, dry particles formed in the agglomerated particles in a relatively resistant form which are not effectively deagglomerated through upper cutting mixing. Dispersions made from such dried agglomerated barium titanate based particles, which have a primary submicron particle size, required a substantially long duration of milling of the medium to provide particles in the submicron range. Likewise, it is considered that the heating used to dry the wet pulp, particularly if it is carried out under a high temperature and / or long period of time, can potentially effect a coating on the barium titanate-based particle. Such potential negative effects include, for example, the binding of a hydrous oxide coating layer between particles that could become difficult to separate without peeling or scraping the coating layer from some of the particles based on barium titanate. EXAMPLE 2 To determine the dispersion effectiveness of the particles based on barium titanate in a non-aqueous solvent, the particles Lower ignition X7R derived in hydrothermal form, were subjected to a solvent exchange process, followed by dispersion with a phosphate ester dispersant. Particles X7R of the lower ignition derived hydrothermally, were initially in water. The water was displaced by a solvent mixture of 80 toluene / 20 ethanol. One kilogram (1 kg) of a wet paste of barium titanate derived hydrothermally by X7R formulated, which contains 72% by weight of solids and 28% by weight of water, was made into pulp with one kilogram (1 kg) of ethanol. Subsequently, the paste was placed in a Buchner funnel containing a membrane of F ultrafiltration which was subsequently used in the form of a filter medium. The ethanol filtered through the wet paste formed and the cracks that formed, were eliminated in the mechanics. Once the first filtration was near its end, one kilogram (1 kg) of ethanol was filtered and filtered through the wet paste. This step was repeated once the second filtration was near its term. After the ethanol filtration was completed, it was added one kilogram (1 kg) of toluene and filter through the wet paste. Subsequently, the moisture paste was left to dry for a solids loading of 75% by weight. The resulting wet paste (859.3 grams) was subsequently mixed with a DISPERSATOR ™ top cut mixer (Premier Mili), with 26.81 grams of phosphate ester dispersant RHODAFAC RS-410 ™ (Rhone-Poulenc). The cutting mixer The top was left to mix the wet paste for a period of 10 minutes (Sample 4), and a period of 30 minutes (Sample 5). Subsequently, the particle size distributions were measured, and the results are presented below and are illustrated in Figure 2A and Figure 2B.

SAMPLE Di or D5o D90 D90 / D10 .10 Min. Cutting Mixer 0.381 0.869 1 .908 5.0 .30 Min. Cutting Mixer 0.351 0.764 1 .805 5.1 The above experimental results illustrate that the solvent exchange can be used to replace aqueous solvents with non-aqueous solvents if desired, followed by the addition of an appropriate dispersant to achieve an acceptable ratio (D90 / D10). The solvent exchange process provides dispersions that have much narrower particle size distributions, with higher cut mixes only (without a horizontal media mill) in less time than the resulting dispersions from dry powder (such as is shown in EXAMPLE 1, Sample 1). In addition, it is considered that a ratio (D9o / D-? 0) of less than 3 from the powder X7R derived hydrothermally in a non-aqueous solvent (from solvent exchange) with the selection of an appropriate dispersant f, can be achieved with less subsequent processing in horizontal media mill and (depending on other factors such as lot size). It is considered that alternative solvents (such as, for example, those described above), with an appropriate dispersant, can be used to create pastes with particles having acceptable proportions (Dg0 / D? 0).

In addition to the above, the solvent exchange process avoids the potential negative effects from drying the wet pulp in the coating layer on the barium titanate based particle, particularly under a high temperature and / or a period of time long.

EXAMPLE 3 ™ To determine the effectiveness of the use of silane coupling agents to promote the dispersion of barium titanate-based particles in a non-aqueous solvent, a derivatized X7R powder was covered in hydrothermal form using Methyltrimethoxysilane in the form of the coupling agent.

The methyltrimethoxysilane provides a hydrophobic coating, and was placed on the surface of the BaTiO3 particles derived in hydrothermal form by formulated X7R, as indicated below: 1. 95 ml of ethanol were mixed with 5 ml of deionized water. The pH of the solution was adjusted to 4 using 0.1 M HNO3. Methyltrimethoxysilane (5 grams) was added to the acidified ethanol / water solution and stirred for 5 minutes to allow hydrolysis of the three responsible methoxyl groups. 2. BaTi03 wet paste formulated by X7R (70% by weight solids) was diluted with 250 ml of ethanol and emulsified at 7000 rpm for 1 minute. 3. The ethanol / water solution containing the hydrolyzed silane coupling agent was added to the paste containing hydrothermal particles formulated by X7R, and emulsified for 30 seconds at 7000 rpm. 4. The resulting paste was allowed to air dry for 24 hours to remove the excess conveyor. Subsequently, the resulting material was placed in a vacuum drying oven at a temperature of 80 ° C for 12 hours, to dry the powder completely. Dilution of the wet paste formulated by X7R with ethanol resulted in a very viscous suspension at the time of emulsification. The resulting dry powder was tested using a sump / water flotation test to determine whether a hydrophobic coating successfully adhered to the surface of the powder. The powder was generously ground in a mortar and pestle, and was subsequently sprayed on top of the water contained in a container. The particles floated on the water surface initially, but when they were stirred, some of them went to the solution. Therefore, when the wet paste formulated by X7R was initially diluted with ethanol, only a partial coating of the surface was achieved. It's partial coating is probably a result of the high viscosity that resulted when the X7R wet paste was initially diluted with ethanol. The high viscosity resulted in a coating of agglomerates that tend to break when mixed in the sump / flotation test.

EXAMPLE 4 To determine the effectiveness of the use of silane coupling agents to promote the dispersion of the barium titanate-based particles in a non-aqueous solvent, an X7R powder derived in hydrothermal form was coated using methyltrimethoxysilane in the coupling agent form.

The methyltrimethoxysilane provides a hydrophobic coating, and was placed on the surface of the BaTiO3 particles derived in hydrothermal form and formulated by X7R, as indicated below: 1 . 95 ml of methanol was mixed with 5 ml of deionized water. The pH of the solution was adjusted to 4 using 0.1 M H NO3. Methyltrimethoxysilane (5 grams) was added to the acidified methanol / water solution and stirred for 5 minutes to allow hydrolysis of the three responsible methoxyl groups. 2. The BaTiO3 wet paste formulated by X7R (70% by weight solids) was diluted with 250 ml of methanol and emulsified at 7000 rpm for 1 minute. 3. The methanol / water solution containing the hydrolyzed silane coupling agent was added to the paste containing hydrothermal particles formulated by X7R and emulsified for 30 seconds at 7000 rpm. 4. The resulting paste was allowed to air dry for 24 hours to remove the excess carrier. Subsequently, the material The resultant was placed in a vacuum drying oven at a temperature of 80 ° C for 12 hours to dry the powder completely.

The resulting dry powder was tested using a sump / flotation test to determine if the hydrophobic coating successfully adhered to the surface of the powder. The dust was F was generously ground in a mortar and pestle, and was subsequently sprayed on top of the water contained in a container. The particles floated on the surface of water, and remained on the surface even during the agitation. For the Thus, when the wet paste formulated by X7R was initially diluted with methanol, complete surface coverage was achieved. Dilution of the wet paste formulated by X7R with methanol resulted in a well dispersed paste with low viscosity. When the solution of the hydrolyzed silane coupling agent was added it made it possible to complete the coating of the particles. Those skilled in the art will readily appreciate that all the parameters described in the present invention are by way of example and that the actual parameters will depend on the specific application for the methods and apparatus of the present invention that are used. Therefore, it is to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended Claims and equivalents thereof, the present invention may be practiced in another manner than that described in specific.

F

Claims (38)

1. R E I V I N D I C A C I O N E S Having described the present invention, it is considered as a novelty and, therefore, the property contained in the following CLAIMS is claimed as property:

   1 .- A paste, dispersion or detachment comprising particles based on barium titanate dispersed in a non-aqueous medium, said particles having a coating comprising a metal oxide, a hydrous oxide of metal, a metal hydroxide or a salt of organic acid of a metal other than barium or titanium, wherein at least 90% of said particles have a particle size less than 0.9 microns when they are dispersed by upper cutting mixing.
2. 2. The paste, dispersion or detachment as described in claim 1, further characterized in that said

   F particles have a particle size distribution ratio Dgo / D-io less than 4.
3. 3. The paste, dispersion or detachment as described in claim 1, further characterized in that said particles have a decile proportion of the particle size distribution Dg0 / D10 less than 3.

   25
4. 4. - The paste, dispersion or detachment as described in Claim 1, further characterized in that said particles have a decile proportion of the particle size distribution Dg0 / D10 less than 2.5.
5. 5. - The paste, dispersion or detachment as described in Claim 1, further characterized in that at least 90% of said particles have a particle size of less than 0.8 microns, when said particles are dispersed by upper cutting mixing.
6. 6. - The paste, dispersion or detachment as described in Claim 1, further characterized in that at least 90% of said particles have a particle size of less than 0.7 microns, when said particles are dispersed by upper cutting mixing.
7. 7. - The paste, dispersion or detachment as described in Claim 1, further characterized in that at least 90% of said particles have a particle size of less than 0.6 microns, when said particles are dispersed by upper cutting mixing.
8. 8. - The paste, dispersion or detachment as described in Claim 1, further characterized in that at least 90% of said particles have a particle size of less than 0.5 micrometers, when said particles are dispersed by upper cutting mixing. F
9. 9. The paste, dispersion or detachment as described in Claim 1, further characterized in that at least 90% of said particles have a particle size of less than 0.4 microns, when said particles are dispersed f by mixing upper cut.

   10
10. 10. - The paste, dispersion or detachment as described in claim 1, further characterized in that at least 90% of said particles have a particle size of less than 0.3 micrometers, when said particles are dispersed by means of upper cutting mixing. .

    1 .- The paste, dispersion or detachment as described in claim 1, further characterized in that it comprises at least 50% by weight of said particles.

    twenty

    12. - The paste, dispersion or detachment as described in claim 1, further characterized in that it comprises at least 60% by weight of said particles.

    13. - The paste, dispersion or detachment as described in Claim 1, further characterized in that it comprises at least 75% by weight of said particles. F

    14. The paste, dispersion or detachment as described in Claim 1, further characterized in that it comprises a dispersant.

    15. - The paste, dispersion or detachment as it is

    10 described in Claim 1, further characterized in that said particles include a coating with a coupling agent on the surface of said particles.

    16. - The paste, dispersion or detachment as it is

    15 described in Claim 15, further characterized in that the coupling agent comprises an organosilane. F

    7. The paste, dispersion or detachment as described in claim 1, further characterized in that it additionally comprises between 3 and 20% by weight of a linker composition comprising a polymer that forms a film, suspended or dissolved .

    18. - The paste, dispersion or detachment as it is

    25 described in Claim 1, further characterized in that substantially all of said particles are cut in an equiaxed or spherical manner.

    F 19. The paste, dispersion or detachment as described in Claim 1, further characterized in that said particles are produced in hydrothermal form.

    20. - The paste, dispersion or detachment as it is

    F describes in Claim 1, further characterized in that said

    10 coating covers an important part of the surface of the particles.

    21 .- The paste, dispersion or detachment as described in Claim 1, further characterized in that said

    The coating comprises at least one metal selected from the group consisting of bismuth, lithium, magnesium, calcium, strontium, scandium, zirconium, hafnium, vanadium, niobium, tantalum, tungsten, manganese, cobalt, nickel, zinc, boron, silicone, antimony, tin, trio, lanthanum, lead, or a lanthanide element. 22. The paste, dispersion or detachment as described in Claim 1, further characterized in that the non-aqueous medium comprises an organic solvent.

    23. - The paste, dispersion or detachment as described in Claim 22, further characterized in that the non-aqueous medium comprises a mixture of organic solvent and

    F water.

    24. - The paste, dispersion or detachment as described in Claim 22, further characterized in that the organic solvent is selected from the group consisting of

    F benzene, ethyl methyl ketone, acetone, xylene, methanol, ethanol,

    10 propanol, 1, 1, 1 -trichloroethane, tetrachlorethylene, amyl acetate, 2,2,4-triethyl pentanediol-1,3-monoisobutyrate, toluene, methylene chloride, turpentine, ethyl alcohol, bromochloromethane, butanol, diacetone, isobutyl ketone of methyl, cyclohexanone, methyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, n-octyl alcohol,

    15 benzyl alcohol, glycerol, ethylene alcohol, benzaldehyde, propionic acid, n-octanoic acid, ethylacetate, butylbutyrate, n-hexane and mixtures thereof.

    25. - The paste, dispersion or detachment as it is

    20 described in Claim 24, further characterized in that the organic solvent is ethanol.

    26. - The paste, dispersion or detachment as described in Claim 1, further characterized in that the non-aqueous medium comprises a mixture of more than one organic solvent.

    i 27.- The paste, dispersion or detachment as it is

    5 described in Claim 26, further characterized in that said mixture is selected from the group consisting of 72% trichlorethylene / 28% ethyl alcohol, 66% methyl ethyl ketone / 34% ethyl alcohol, 70% ethyl methyl ketone. / 30% ethyl alcohol, 59% methyl ethyl ketone / 41% ethyl alcohol, 50%

    10 methyl ethyl ketone / 50% ethyl alcohol, 80% toluene / 20% ethanol, 80% toluene / 20% ethyl alcohol, 70% toluene / 30% ethyl alcohol, 60% toluene / 40% Ethyl Alcohol, 70% Isopropyl Alcohol / 30% Ethyl Methyl Ketone, 40% Ethyl Methyl Ketone / 60% Ethyl Alcohol, and Mixtures of the

    15 same.

    28. - The paste, dispersion or detachment as described in Claim 27, further characterized in that the non-aqueous medium is 80% toluene / 20% ethanol. 20 29.- A method for forming a paste, dispersion or detachment comprising: forming a paste of particles based on barium titanate in an aqueous medium by means of a hydrothermal process;

    forming a coating on said particles comprising a metal oxide, hydrous metal oxide, metal hydroxide or an organic acid salt of a metal f other than barium or titanium; replacement of the aqueous medium with a non-aqueous medium; and dispersing said particles in the non-aqueous medium by means of upper cutting mixing.

    30. - The method as described in Claim 29,

    10 further characterized in that said particles are dispersed in the non-aqueous medium by top-cutting mixing until 90% of said particles have a particle size less than 0.9 microns.

    31.- The method as described in claim 29, further characterized in that the replacement of the aqueous medium with a

    F non-aqueous medium comprises a solvent exchange process.

    32. - The method as described in Claim 31,

    20 further characterized in that the solvent exchange process comprises: filtering the paste of the barium titanate-based particles in the aqueous medium; and introducing the filtered particles in a non-aqueous medium.

    25

    33. - The method as described in claim 29, further characterized in that the replacement of the medium with a non-aqueous medium, comprises a distillation process. F

    The method as described in claim 33, further characterized in that the distillation process comprises:

    add the non-aqueous medium to the paste of particles based on barium titanate in the aqueous medium; and f evaporate the aqueous medium. The method as described in claim 29, further characterized in that it additionally comprises applying a coupling agent to the surface of said particles after replacing the aqueous medium with an aqueous non-M 15 medium.

    36. The method as described in claim 29, further characterized in that it additionally comprises applying a coupling agent to the surface of said particles after forming a coating on said particles, and before replacing the aqueous medium with a medium. io non-aqueous.

    37. The method as described in the Claims

    35 or 36, further characterized in that the coupling agent comprises organosilane.

    5 38.- A method for forming a paste, dispersion or detachment comprising: dispersing the particles based on barium titanate in a non-aqueous medium by mixing upper cut, I until 90% of said particles have a size of

    10 particles smaller than 0.9 microns, said particles having a coating comprising a metal oxide, a hydrous metal oxide, a metal hydroxide or an organic acid salt of a metal other than barium or titanium.

    F