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WO1988008830A1 - Ceramique dielectrique ayant des constantes dielectriques elevees, des facteurs de dissipation faibles et des coefficents de temperature stables - Google Patents

Ceramique dielectrique ayant des constantes dielectriques elevees, des facteurs de dissipation faibles et des coefficents de temperature stables Download PDF

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WO1988008830A1
WO1988008830A1 PCT/US1987/002907 US8702907W WO8808830A1 WO 1988008830 A1 WO1988008830 A1 WO 1988008830A1 US 8702907 W US8702907 W US 8702907W WO 8808830 A1 WO8808830 A1 WO 8808830A1
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Terence C. Dean
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
    • C04B35/462—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates
    • C04B35/465—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates
    • C04B35/468—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates based on barium titanates
    • C04B35/4682—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates based on barium titanates based on BaTiO3 perovskite phase
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B18/00—Layered products essentially comprising ceramics, e.g. refractory products
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
    • C04B2237/30—Composition of layers of ceramic laminates or of ceramic or metallic articles to be joined by heating, e.g. Si substrates
    • C04B2237/32—Ceramic
    • C04B2237/34—Oxidic
    • C04B2237/345—Refractory metal oxides
    • C04B2237/346—Titania or titanates
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
    • C04B2237/50—Processing aspects relating to ceramic laminates or to the joining of ceramic articles with other articles by heating
    • C04B2237/68—Forming laminates or joining articles wherein at least one substrate contains at least two different parts of macro-size, e.g. one ceramic substrate layer containing an embedded conductor or electrode
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
    • C04B2237/50—Processing aspects relating to ceramic laminates or to the joining of ceramic articles with other articles by heating
    • C04B2237/70—Forming laminates or joined articles comprising layers of a specific, unusual thickness
    • C04B2237/704—Forming laminates or joined articles comprising layers of a specific, unusual thickness of one or more of the ceramic layers or articles

Definitions

  • the present invention relates to ceramic dielectric compositions which have high dielectric constants (K), e.g., between about 4900 and about 5400; low dissipation factors (DF), e.g., below about 2%; high insulation resistance (R) capacitance (C) products (RC) , e.g., above about 7000 ohm-farads at 25°C and above about 3000 ohm-farads at 125°C; and stable temperature coefficient (TC) characteristics in which the dielectric constant does not alter from its base value at 25°C by more than about plus or minus 15% over a temperature range from - 55°C to 125°C.
  • K dielectric constants
  • DF low dissipation factors
  • RC high insulation resistance
  • RC capacitance
  • TC stable temperature coefficient
  • Multilayer ceramic capacitors are commonly made by casting or otherwise forming insulating layers of dielectric ceramic powder; placing thereupon conducting metal electrode layers, usually a palladium/silver alloy in the form of metallic paste; stacking the resulting elements to form the multilayer capacitor; and firing to densify the material, thus forming a multilayer ceramic capacitor.
  • conducting metal electrode layers usually a palladium/silver alloy in the form of metallic paste
  • firing to densify the material, thus forming a multilayer ceramic capacitor.
  • Other processes for forming MLC's are described in U.S. Patents Nos. 3,697,950 and 3,879,645 and in U.S. Patent Application Serial No. 730,711, which is incorporated herein by reference.
  • a high dielectric constant is important, because it allows a manufacturer to build smaller capacitors for a given capacitance.
  • the electrical properties of many dielectric ceramic compositions may vary substantially as the temperature increases or decreases, however, and the variation of the dielectric constant and the insulation resistance with temperature and the dissipation factor, are also important factors to be considered in preparing ceramic compositions for use in multilayer capacitors.
  • the dielectric constant does not change from its base value at 25°C (room temperature) by more than about plus or minus 15%.
  • the insulation resistance and capacitance product of such a composition should be more than 1000 ohm-farads at 25°C and more than 100 ohm-farads at maximum working temperature, 125°C in most cases.
  • the dissipation factor should be as close to 0% as possible.
  • the method commonly used to produce such temperature stable capacitors consists of firing BaTiO-., used because of its high dielectric constant, together with minor ceramic oxide additives (dopants) which comprise minor amounts of elements or compounds which control the final dielectric properties.
  • dopants minor ceramic oxide additives
  • the degree of distribution of the ceramic oxide dopants throughout the barium titanate in the unfired state will determine such things as the extent of solid solution development during firing, grain growth, and the composition of the final fired grain and grain boundary.
  • the efficiency of mixing is a key factor in the process to achieve the desired electrical properties in the finished multilayer ceramic capacitor.
  • the very minor amounts of ceramic oxide dopants have been very difficult to distribute in a homogeneous fashion throughout the blended ceramic dielectric composition.
  • the particles of the ceramic oxide dopants of a dielectric composition must be in finely divided form to ensure adequate mixing of the ceramic oxide dopants with the BaTiO.,.
  • the minor components must disperse themselves such that the environment around each barium titanate grain is the same throughout the bulk of the composition and such that the environment within each barium titanate grain is the same throughout the bulk of the composition.
  • barium titanate powder of approximately 1.0 micron average particle size is mixed with niobium pentoxide and cobalt oxide of approximately 0.1 micron particle size, and assuming that these particles are perfectly spherical and uniformly distributed, it can be calculated that a unit of mix would contain 400 particles of barium titanate, 5000 particles of niobium pentoxide and 1000 particles of cobalt oxide. Thus for each barium titanate particle there would be approximately thirteen niobium pentoxide particles and three cobalt oxide particles. It would therefore be expected that compositional development during sintering would occur much more efficiently and the effectiveness of the ceramic oxide dopant additives would be greatly enhanced compared to that achieved by mixing 1 micron particles of the minor components.
  • ceramic oxide particles can be reduced in size to about 1 micron by milling techniques. It has however been impossible to mill finely divided powders on the order of 0.1 microns because milling techniques incur the risk of increasing the contamination levels of undesirable species, present in the milling media, and because milling efficiencies are significantly reduced as the particle size of the powder reaches submicron levels.
  • the process described in this invention provides a means for enhancing uniformity of distribution of minor component dopants in a ceramic mixture before firing, and thus a means for enhancing the compositional development during sintering. This is done by precipitating minor component dopants in a finely divided form, of approximately 0.1 micron average particle size, in a controlled manner such that they are associated with major ceramic component particles.
  • the term "associated” identifies the heterocoagulation of unlike particles produced by precipitation in accordance with the invention as disclosed herein.
  • the zeta potential of a species of particles can be determined by analysis of the behavior of the particles in suspension in a medium of a specific pH, using an electrophoresis cell in which the particle velocity is measured as a function of the applied potential gradient. The particle velocity is proportional to the zeta potential.
  • a zeta potential curve relating zeta potential and pH, which will indicate both the sign and magnitude of the surface charge of the particles in suspension over a range of pH values.
  • IEP isoelectric point
  • This effect of heterocoagulation of species is important because it provides a means for associating dopant particles with major ceramic component particles and, is equally important because it prevents the homocoagulation of "like" particles. Furthermore, when the dopant particles are precipitated such that the 0.1 micron dopant particles associate in this manner with the 1.0 micron particles of the major ceramic component, then the major ceramic component particles become coated with the dopant particles. Consequently, prior to the sintering stage in the production of a multilayer ceramic capacitor, the dopant particles are precisely in the position desired to produce a uniform, dopant rich grain boundary phase surrounding a major ceramic component core grain during the sintering of the composite.
  • the isoelectric point of the niobium pentoxide precipitated in the process of this invention is at pH 3.1 and the isoelectric point of the barium titanate is at pH 9.0.
  • the niobium pentoxide particles are positively charged, and at pH values higher than 3.1 the niobium pentoxide particles are negatively charged.
  • the barium titanate particles are negatively charged and at pH values lower than 9.0 the barium titanate particles are positively charged.
  • the niobium pentoxide particles will be negatively charged and the barium titanate particles will be positively charged. This condition favors association of the two different charged species with each other, while at the same time it causes like charged species to repel each other, and thus avoids homocoagulation which can cause uneven grain size.
  • the preferred pH condition would be one in which the species are oppositely charged and the magnitude of the difference between the zeta potentials of the major component particles and the dopant particles is as large as possible. This would cause the greatest attraction between the two different species, and simultaneously it would cause the greatest repulsion of like species, providing a very desirable state of dispersion of the dopant particles throughout the major component particles.
  • this preferred condition would occur at pH 7, where the zeta potential of the barium titanate is +30 milivolts, and the zeta potential of the niobium pentoxide is -45 milivolts.
  • the advantage of precipitating the niobium pentoxide particles using the preferred pH conditions, such that the 0.1 micron particles of niobium pentoxide are associated with the 1.0 micron particles of the barium titanate and not with themselves, is that this places the niobium pentoxide particles precisely in the position desired to produce a uniform niobium pentoxide rich grain boundary phase surrounding a barium titanate core grain. This positioning of the niobium pentoxide enables it to control grain growth during the sintering of the ceramic, and the electrical properties of the dielectric ceramic capacitor are thus enhanced.
  • niobium pentoxide diffuses very slowly at the sintering temperatures used in the production of MLC's containing barium titanate and niobium pentoxide, i.e., approximately 1300°C. Consequently, if the niobium pentoxide is not distributed uniformly around the barium titanate particles in suspension during the mixing stage, then, during the sintering stage, the slow diffusion rate will lead to non-uniformly distributed niobium pentoxide in the developing microstructure, causing uneven grain growth and consequently inferior dielectric properties.
  • Non-uniform distribution can occur when 1.0 micron particles of niobium pentoxide and 1.0 micron particles of barium titanate are mixed in a conventional manner by dry or wet mixing the ingredients in a mill jar or the like, or when the niobium pentoxide is precipitated under conditions where homocoagulation of the barium titanate or niobium pentoxide is favored.
  • niobium pentoxide and cobalt oxalate are precipitated in a suspension of barium titanate
  • the cobalt oxide formed from the cobalt oxalate during firing, is present as an additive to compensate for the electronic charge imbalance created by the addition of the niobium pentoxide to the barium titanates and not as a grain growth inhibitor.
  • Cobalt oxide diffuses very quickly at the sintering temperatures used to produce MLC's and, therefore, as illustrated in the examples, its effectiveness is not necessarily reduced by its being present as a 1.0 micron powder.
  • the process described in this invention has the advantage of producing ceramic oxide particles of the order of 0.1 microns without the problems associated with current milling techniques.
  • a second advantage of the process is the production of ceramic dielectric compositions with improved electrical properties, i.e., higher dielectric constants, lower dissipation factors and higher insulation resistance capacitance products than those processed by conventional mixing techniques.
  • the higher dielectric constant achieved as a result of this process has the important advantage of allowing capacitor manufacturing companies to produce multilayer ceramic capacitors with higher capacitance values for a given chip size, or the same capacitance values at a reduced chip size, given that the number of active insulating layers and the thickness of each insulating layer are constants. The benefits are thus reduced cost and/or miniaturization.
  • the first stated object is achieved by the present invention, which provides a process for producing a mixture of ceramic oxides, including a major ceramic oxide component and one or more minor component dopants, wherein at least one of the minor ceramic oxide dopants must be, and the other dopant(s) may be, precipitated and wherein the process conditions are controlled such that the precipitated dopant particles are charged oppositely to, and are associated with, the particles of the major ceramic oxide component.
  • the present invention provides a process for producing a ceramic composition having high dielectric constant, low dissipation factor, and stable TC characteristics including a major component, preferably comprising high purity barium titanate, and minor component dopants, preferably comprising niobium pentoxide and cobalt oxide, wherein the niobium pentoxide dopant must be, and the cobalt oxide dopant may be, precipitated to provide the small particles of the present invention.
  • Dielectric ceramic compositions chosen for processing according to this invention contain the major component preferably barium titanate, which comprises from about 98.5 to about 98.8 per cent by weight and the minor component dopants, preferably niobium pentoxide and cobalt oxide, which comprise from about 1.0 to about 1.1 per cent by weight and from about 0.2 to about 0.3 per cent by weight respectively.
  • major component preferably barium titanate, which comprises from about 98.5 to about 98.8 per cent by weight and the minor component dopants, preferably niobium pentoxide and cobalt oxide, which comprise from about 1.0 to about 1.1 per cent by weight and from about 0.2 to about 0.3 per cent by weight respectively.
  • the process described in this invention provides a method for making a dielectric ceramic having dopant particles uniformly dispersed therein comprising: dispersing major component particles in a liquid medium; precipitating dopant particles from a liquid medium containing a precursor of the dopant; dispersing the dopant particles throughout the major component particles so that dopant particles are associated with the major component particles; removing the liquid medium; and sintering.
  • the process described in this invention provides a method for making a dielectric ceramic having dopant particles uniformly dispersed therein comprising: dispersing major component particles in a liquid medium; precipitating dopant particles from a liquid medium containing a precursor of the dopant; controlling the conditions such that the major component particles are charged oppositely to the dopant particles; dispersing the dopant particles throughout the major component particles so that the dopant particles are associated with the major component particles; removing the liquid medium; and sintering.
  • the invention also provides a dielectric ceramic comprising: a sintered mass of precipitated dopant particles dispersed throughout major component particles such that the dopant particles are associated with the major component particles.
  • the invention also provides a multilayer ceramic capacitor comprising: a plurality of dielectric ceramic layers wherein the dielectric ceramic comprises precipitated dopant particles associated with major component particles such that the dopant particles are in fixed proportion to the major component particles and such that the dielectric ceramic, when fired, has a dielectric constant between about 4900 and 5400, a dissipation factor of below about 2.0%, an insulation resistance capacitance product above about 7000 ohm- farads at 25°C and above about 3000 ohm-farads at 125°C and a temperature stable temperature coefficient in which the dielectric constant does not vary more than plus or minus 15% from its value at 25°C over the temperature range from -55°C to 125°C; and a plurality of electrodes between the dielectric layers.
  • dopant precursor means the species of dopant or dopant ion present in the liquid medium prior to the precipitation step.
  • the method of producing a ceramic dielectric comDosition of the present invention has several advantages which result in substantial technological advancement and cost savings while enhancing desirable physical and electrical properties.
  • the present invention provides a novel method of producing a dielectric composition having a dielectric constant between 4900 and 5400, a dissipation factor of less than 2.0%, and with stable TC characteristics.
  • This process differs substantially from those disclosed in the prior art in which conventional mixing techniques are used and in which desirable dielectric properties, such as a higher dielectric constant, are sacrificed in order to obtain materials which have stable TC characteristics.
  • desirable dielectric properties such as a higher dielectric constant
  • the process described in this invention provides a means for enhancing the uniformity of the distribution of the dopants in the ceramic mixture before firing by using major component powder of approximately 1.0 micron average particle size, and by precipitating one or both of the dopants in a finely divided form, approximately 0.1 micron average particle size, in a controlled manner, such that the dopant particles are associated with the major ceramic component particles.
  • major component powder of approximately 1.0 micron average particle size
  • precipitating one or both of the dopants in a finely divided form, approximately 0.1 micron average particle size in a controlled manner, such that the dopant particles are associated with the major ceramic component particles.
  • the process of the invention involves precipitating a dopant from a liquid medium and mixing the precipitated dopant with a slurry of the major component such that the dopant particles are uniformly dispersed throughout the major component particles.
  • the major component of the ceramic composition is slurried in liquid media followed by the addition of a precise amount of a solution containing a precursor of a dopant.
  • the major component can be slurried in a solution containing a precursor of a dopant.
  • the dopant is then precipitated from the solution in a finely divided form in a controlled manner such that intimate contact between the major component particles and the dopant is achieved. This procedure can be used to introduce one or more dopants.
  • the major component is preferably chosen from the group of perovskite forming metal oxides.
  • the major component of the ceramic composition is slurried in liquid media followed by the addition of a precise amount of a solution containing a precursor of a dopant.
  • the major component can be slurried in a solution containing a precursor of a dopant.
  • the dopant is then precipitated from the solution in a finely divided form while the charges of the major ceramic component particles and the dopant particles are controlled such that intimate contact between the major component particles and the dopant is achieved. This procedure can be used to introduce one or more dopants.
  • the major component is preferably chosen from the group of perovskite forming metal oxides.
  • the major component is barium titanate (BaTiO.,), which is slurried in water and the two dopants are niobium pentoxide and cobalt oxide.
  • the niobium pentoxide is precipitated in the presence of the barium titanate, while the cobalt oxide may be introduced to the slurry either in powder form or as a precipitate.
  • the precursor solution of niobium pentoxide is a solution of niobium pentachloride in ethanol and the niobium pentoxide is precipitated with concentrated ammonium hydroxide.
  • the intimate mixture of components may be mixed with a suitable binder composition; cast into a sheet using standard methods; formed into a multilayer capacitor structure with internal electrodes such as 70% paladium/30% silver; and fired at about 1280°C to about 1350°C for about 2 hours.
  • a suitable binder composition which is compatible with the other materials used and which simply provides a vehicle for dispersing the ceramic particles and holding them together when the solvent is removed, may be used with this invention.
  • Suitable binder compositions are described in "Ceramic Process Before Firing", G.Y. Onoda Jr., et al. John Wiley and Sons (1978) chapter 19. Corn syrup and polyvinyl alcohol are examples of suitable binder compositions.
  • the fired dielectric composition of this invention is processed into a multilayer ceramic capacitor with high dielectric constant between about 4900 and about 5400, low dissipation factors below 2%, and insulation resistance products at 25°C, 50 VDC/mil of greater than 7000 ohm-farads and at 125°C, 50 VDC/mil of greater than 3000 ohm-farads and with stable TC characteristics such that the dielectric constant does not vary by more than plus or minus 15% of the reference value at 25°C.
  • high purity, barium titanate (99.9 to 99.95% pure) of fine particle size (.8 to 1.3 microns) is stirred in de-ionized water.
  • Cobalt oxide of fine particle size .8 to 1.3 microns is added and the mixture is stirred continuously for 30 minutes to 33 hours to ensure adequate mixing of the two reagents.
  • a solution of niobium pentachloride in ethanol is added to the barium titanate/cobalt oxide slurry.
  • the ratio of barium titanate, cobalt oxide and niobium pentachloride is such that the ratio of barium titanate: niobium pentoxide : cobalt oxide in the resulting ceramic composition is 9871 : 107 : 22.
  • the resulting slurry is stirred for 10 to 60 minutes and concentrated ammonium hydroxide is added to precipitate hydrous niobium pentoxide.
  • the composite slurry is filtered and washed with deionized water until the washings when tested with silver nitrate/nitric acid solution, show a complete absence of silver chloride precipitate.
  • the washed mixture of ceramic oxides is then dried in a laboratory oven at 110°C.
  • the uniformly blended ceramic composition is then charged into a ball mill together with a binder solution made by uniformly mixing dioctylphthalate "NUOSTABE V-1444 m ",_i/ ethanol, toluene and "BUTVAR B-76 TH "2./ vinyl resin.
  • the ratio of ceramic composition to binder is 400 : 218.
  • the slurry is mixed for 5 to 20 hours, discharged and filtered through a 44 micron screen. This slurry, having a viscosity of about 1500 centipoise, is then de-aired and
  • NUOSTABE V-1444 IK is an alkali ion free organic solvent dispersing agent available from Nuodex Co. Inc., New Jersey.
  • BUTVAR B-76 ra is a binder comprising a mixture of polyvinyl butyral, polyvinyl alcohol and polyvinyl acetate available from Monsanto Corp. cast, in accordance with standard techniques, into a tape with a thickness of about 1.5 mils.
  • the tape is converted into a multi-layer ceramic capacitor having 70% paladium/30% silver electrodes via conventional processes well known in the industry.
  • the capacitors are preheated to 260°C for 48 hours, placed on zirconia setters and sintered at 1280°C to 1340°C for 1 to 3 hours.
  • the sintered capacitors have 10 active dielectric layers with dielectric thickness of about 1.1 to about 1.2 mil.
  • Termination electrodes of DupontTM silver paint number 4822 which is a mixture of silver and glass frit in a binder, are applied at opposite ends of the multi-layer capacitor to connect alternate electrode layers and these capacitors are fired at 815°C in a tunnel furnace.
  • the resulting multi-layer capacitor has a dielectric constant of approximately 5400 and a dissipation factor of approximately 1.57% measured at lKHz at 1VRMS, and TC characteristics such that the dielectric constant does not vary from its value at 25°C by more than about ⁇ 9.9% between -55°C and +125°C.
  • the composite slurry was filtered and washed with deionized water until the washings when tested with silver nitrate/nitric acid solution, showed a complete absence of silver chloride precipitate.
  • the washed mixture of ceramic oxides were then dried in a laboratory oven at 110°C.
  • This slurry was mixed for 16 hours, discharged and filtered through a 44 micron screen. This slurry having a viscosity of about 1500 centipoise was then de-aired and cast, in accordance with standard techniques, into a tape with a thickness of about 1.5 mils.
  • the tape was converted into a multilayer ceramic capacitor having 70 percent palladium/30 percent silver electrodes via conventional processes well known in the industry.
  • the capacitors were preheated to 260°C for 48 hours, placed on zirconia setters and sintered at 1280°C to 1340°C for 2 hours.
  • the sintered capacitors had 10 active dielectric layers with dielectric thickness of about 1.1 - 1.2 mil. Termination electrodes of DupontTM silver paint No.
  • Table 1 shows the weight percent additions of niobium pentoxide and cobalt oxide to barium titanate for a series of compositions prepared according to the method described in Example 1 along with a similar series of compositions (A - H) which were prepared by the conventional mixing of 1 micron ceramic powders.
  • the surface area, expressed as meters squared per gram, and the average particle size (d50), as determined using the Micromeritics SedigraphTM, are given for both compositional series and illustrate the apparent difference in the physical properties of the compositions prepared by the method described in this invention and by the conventional mixing of 1 micron ceramic oxide particles.
  • Example 7 500 g of high purity barium titanate was stirred in a solution of 500 mis of cobalt acetate solution containing the equivalent of 2.1674 gram of cobalt oxide (CoO) per litre of deionized water. Stirring was continued for a further 30 minutes and 30 mis of a solution of oxalic acid containing 30.3 g oxalic acid dihydrate ([CO OH]2 2H20) per 500 mis of deionized water were added to precipitate cobalt oxalate in a finely divided form.
  • CoO cobalt oxide
  • Multilayer ceramic capacitors were prepared from the composite slurry as described in Example 1.
  • the electrical test results are shown in Table 3 along with those obtained for Example 8 which was prepared in similar fashion to Example 7 except that 500 mis of cobalt acetate solution containing the equivalent of 2.0798 grams cobalt oxide per litre of water was used with 179.25 mis of niobium pentachloride in ethanol solution containing the equivalent of 28.08 grams niobium pentoxide per litre of water.
  • Multilayer ceramic capacitors were prepared as described in Example 1. The electrical results are shown in Table 4 and are compared with those obtained from conventional
  • DARVAN CTM is an alkali ion free aqueous dispersing agent comprising a mixture of polyelectrolytes, ammonia and sulfur available from W.P. Vanderbllt Co., Conn. mixing of 500 g of the same barium titanate with 1.0 micron cobalt oxide and niobium pentoxide in the same proportions.
  • compositions prepared using conventional mixing processes and approximately 1.0 micron ceramic oxide powders.
  • Table 2 lKHz TC(%) at RC 50 VDC
  • Example 1VRMS K DF% -55°C -30°C + 85 °c +125°C at 25°C 125°C
  • Example 10 500 g of high purity barium titanate and 5.2453 g of fine particles size (1.0 micron) niobium pentoxide was added to 500 ml of cobalt acetate solution containing the equivalent of 2.1674 g of cobalt oxide (CoO) per litre of deionized water and stirred continuously for 3 hours to ensure adequate mixing of the reagents.
  • 30 is of a solution of oxalic acid containing 30.3 g oxalic acid dihydrate ([COOH_ 2 " 2H 2 0) per 500 mis of deionized water were added to precipitate cobalt oxalate in a finely divided form.
  • the composite slurry was filtered, washed and dried in an oven at 110°C.
  • Multilayer ceramic capacitors were prepared from the composite slurry as described in Example 1.
  • the electrical test results are shown in Table 5 along with those obtained for Example 11 which was prepared in a similar, fashion to Example 10 except that 500 g of high purity barium titanate and 5.0331 g of fine particle size (1.0 micron) niobium pentoxide were added to 500 mis of cobalt acetate solution containing the equivalent of 2.0798 g of cobalt oxide per 500 is of deionized water.

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  • Fixed Capacitors And Capacitor Manufacturing Machines (AREA)

Abstract

L'invention concerne des compositions céramiques pour la préparation de condensateurs multicouche, ayant des constantes diélectriques élevées entre 4900 et 5400 environ, des facteurs de dissipation inférieure à 2,0 % environ, des produits de capacitance de résistance d'isolation élevés et des coefficients de température stables. Le procédé de préparation consiste à mélanger un composant céramique principal avec un ou plusieurs composants de dopage précipité. En régulant les conditions du système, des particules dopantes précipitées sont chargées avec une charge opposée à celle des particules des composants céramiques principaux et sont donc associées aux particules des composants céramiques principaux.
PCT/US1987/002907 1986-11-03 1987-11-03 Ceramique dielectrique ayant des constantes dielectriques elevees, des facteurs de dissipation faibles et des coefficents de temperature stables Ceased WO1988008830A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
AT88309243T ATE133001T1 (de) 1987-11-03 1988-10-04 Dielektrische keramik mit hoher dielektrizitätskonstante, niedrigem verlustfaktor und flachem temperaturkoeffizienten
EP88309243A EP0315324B1 (fr) 1987-11-03 1988-10-04 Céramique diélectrique à constante diélectrique élevée, à faible facteur de dissipation et à coefficient de température plat
DE3854889T DE3854889T2 (de) 1987-11-03 1988-10-04 Dielektrische Keramik mit hoher Dielektrizitätskonstante, niedrigem Verlustfaktor und flachem Temperaturkoeffizienten

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US92659586A 1986-11-03 1986-11-03
US926,595 1986-11-03

Publications (1)

Publication Number Publication Date
WO1988008830A1 true WO1988008830A1 (fr) 1988-11-17

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PCT/US1987/002907 Ceased WO1988008830A1 (fr) 1986-11-03 1987-11-03 Ceramique dielectrique ayant des constantes dielectriques elevees, des facteurs de dissipation faibles et des coefficents de temperature stables

Country Status (2)

Country Link
JP (1) JP2656091B2 (fr)
WO (1) WO1988008830A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0315324A3 (en) * 1987-11-03 1990-01-31 Tam Ceramics Inc. Dielectric ceramic with high k, low df and flat tc
US5084424A (en) * 1988-05-11 1992-01-28 Sakai Chemical Industry Co., Ltd. Ceramic dielectrics and compositions therefor
EP0517725A4 (en) * 1990-02-28 1993-04-21 E.I. Du Pont De Nemours And Company Improved ceramic dielectric composition and method of preparation
EP0517738A4 (en) * 1990-02-28 1993-05-12 E.I. Du Pont De Nemours And Company Improved ceramic dielectric compositions and method for enhancing dielectric properties
WO1993015031A1 (fr) * 1990-06-29 1993-08-05 E.I. Du Pont De Nemours And Company Compositions a constante dielectrique k elevee avec granulometrie fine
US5296259A (en) * 1989-04-21 1994-03-22 E. I. Du Pont De Nemours And Company Process for making electrically conductive patterns
WO2007059130A3 (fr) * 2005-11-14 2007-10-11 Kemet Electronics Corp Condensateur ceramique multi-couche cog
US7670981B2 (en) 2005-04-07 2010-03-02 Kemet Electronics Corporation C0G multi-layered ceramic capacitor
CN111747745A (zh) * 2020-05-20 2020-10-09 四会市康荣新材料有限公司 一种5g滤波器用介质粉体及其制备方法

Citations (2)

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Publication number Priority date Publication date Assignee Title
US3983077A (en) * 1975-05-02 1976-09-28 Texas Instruments Incorporated Process for making ceramic resistor materials
GB1527060A (en) * 1976-08-03 1978-10-04 Siemens Ag Capacitor dielectrics

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61275164A (ja) * 1985-05-03 1986-12-05 タム　セラミツクス　インコ−ポレイテツド 誘電体セラミック組成物
JPS623005A (ja) * 1985-06-28 1987-01-09 Ube Ind Ltd 粉末分散湿式法による易焼結性ペロブスカイト原料粉末の製造法
JPS62139801A (ja) * 1985-12-16 1987-06-23 Toyo Soda Mfg Co Ltd 焼結方法
JPS62143861A (ja) * 1985-12-18 1987-06-27 株式会社日本自動車部品総合研究所 セラミツク焼結体の製造方法

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3983077A (en) * 1975-05-02 1976-09-28 Texas Instruments Incorporated Process for making ceramic resistor materials
GB1527060A (en) * 1976-08-03 1978-10-04 Siemens Ag Capacitor dielectrics

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0315324A3 (en) * 1987-11-03 1990-01-31 Tam Ceramics Inc. Dielectric ceramic with high k, low df and flat tc
US5084424A (en) * 1988-05-11 1992-01-28 Sakai Chemical Industry Co., Ltd. Ceramic dielectrics and compositions therefor
US5296259A (en) * 1989-04-21 1994-03-22 E. I. Du Pont De Nemours And Company Process for making electrically conductive patterns
EP0517725A4 (en) * 1990-02-28 1993-04-21 E.I. Du Pont De Nemours And Company Improved ceramic dielectric composition and method of preparation
EP0517738A4 (en) * 1990-02-28 1993-05-12 E.I. Du Pont De Nemours And Company Improved ceramic dielectric compositions and method for enhancing dielectric properties
WO1993015031A1 (fr) * 1990-06-29 1993-08-05 E.I. Du Pont De Nemours And Company Compositions a constante dielectrique k elevee avec granulometrie fine
US7670981B2 (en) 2005-04-07 2010-03-02 Kemet Electronics Corporation C0G multi-layered ceramic capacitor
US7916451B2 (en) 2005-04-07 2011-03-29 Kemet Electronics Corporation C0G multi-layered ceramic capacitor
US7923395B2 (en) 2005-04-07 2011-04-12 Kemet Electronics Corporation C0G multi-layered ceramic capacitor
WO2007059130A3 (fr) * 2005-11-14 2007-10-11 Kemet Electronics Corp Condensateur ceramique multi-couche cog
CN111747745A (zh) * 2020-05-20 2020-10-09 四会市康荣新材料有限公司 一种5g滤波器用介质粉体及其制备方法

Also Published As

Publication number Publication date
JPH02137759A (ja) 1990-05-28
JP2656091B2 (ja) 1997-09-24

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