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WO1993016012A1 - Method for preparing a mixed metal oxide powder suitable for producing electrical capacitors - Google Patents

Method for preparing a mixed metal oxide powder suitable for producing electrical capacitors Download PDF

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Publication number
WO1993016012A1
WO1993016012A1 PCT/EP1993/000271 EP9300271W WO9316012A1 WO 1993016012 A1 WO1993016012 A1 WO 1993016012A1 EP 9300271 W EP9300271 W EP 9300271W WO 9316012 A1 WO9316012 A1 WO 9316012A1
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WO
WIPO (PCT)
Prior art keywords
solution
powder
process according
metals
barium titanate
Prior art date
Application number
PCT/EP1993/000271
Other languages
French (fr)
Inventor
Henri Wautier
Marianne Van Cauwenbergh
Original Assignee
Solvay S.A.
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Filing date
Publication date
Application filed by Solvay S.A. filed Critical Solvay S.A.
Publication of WO1993016012A1 publication Critical patent/WO1993016012A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G4/00—Fixed capacitors; Processes of their manufacture
    • H01G4/002—Details
    • H01G4/018—Dielectrics
    • H01G4/06—Solid dielectrics
    • H01G4/08—Inorganic dielectrics
    • H01G4/12—Ceramic dielectrics
    • H01G4/1209—Ceramic dielectrics characterised by the ceramic dielectric material
    • H01G4/1218—Ceramic dielectrics characterised by the ceramic dielectric material based on titanium oxides or titanates
    • H01G4/1227—Ceramic dielectrics characterised by the ceramic dielectric material based on titanium oxides or titanates based on alkaline earth titanates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
    • C01B13/14—Methods for preparing oxides or hydroxides in general
    • 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
    • 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
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B

Definitions

  • the invention relates to a process for the manufacture of mixed metal oxide powders suitable for the production of electrical capacitors of high capacity and its use for obtaining a powder intended for the manufacture of capacitors in accordance with standard X7R (ANSI / EIA-198-C-1983 standard),
  • Mixed metal oxide compositions suitable for producing high-capacity electric capacitors are usually prepared by mixing powders of previously ground metal oxides such as, for example, BaTiO ⁇ , Nb2 ⁇ -5, Bi2 ⁇ 3, TJO2, Sn ⁇ 2, Mn ⁇ 2- PbO, ZnO and CoO. (patent US-4499521 in the name of North American PHILIPS Corp.)
  • the powders obtained by known conventional methods generally have morphologies typical of ground powders, with average diameters greater than ⁇ m and, therefore, no longer allow the thickness of the dielectric layers to be reduced.
  • the invention aims to overcome the drawbacks of known methods by providing a method capable of producing submicron powders suitable for the manufacture of ultra-thin dielectric layers for high-capacity multilayer capacitors.
  • the invention relates to a process for the fabrication of a powder of mixed metal oxides suitable for the production of high capacity electric capacitors according to which a submicron powder of barium titanate and one or several metal oxides of groups Ilb, IVa, IVb, Va, Vb, Vllb and VlIIb.
  • the previously calcined barium titanate powder is suspended in a solution containing the metals in the dissolved state, the barium titanate powder is impregnated with the solution, the solution is evaporated and the powder obtained is subjected to pressing followed by sintering.
  • mixed metal oxide powder is meant a powder comprising oxides of at least two different metals.
  • the high capacitance electric capacitors which can be manufactured according to the process of the invention are condens
  • the submicron barium titanate powder which is used according to the invention can be obtained by any suitable method making it possible to obtain barium titanate grains of regular particle size whose average diameter is below
  • the submicron barium titanate powder is prepared by coprecipitation resulting from the mixture of an alcoholic solution of oxalic acid and titanium alcoholate with a solution
  • methanol as solvent for oxalic acid and titanium alcoholate.
  • the submicron barium titanate powder is prepared by hydrolysis of a titanium alcoholate in the presence of a hydrated barium hydroxide and a carboxylic acid containing more of 6 carbon atoms in its molecule as it was
  • the carboxylic acid will preferably be selected from aliphatic acids with a linear carbon chain. Oleic acid has given excellent results.
  • the metals of groups Ilb, IVa, IVb, Va, Vb, Vllb and VlIIb of the periodic table of the elements will advantageously be chosen from silicon, niobium, bismuth, manganese, and cobalt. It is imperative to use at least one and preferably at least two of these metals. Excellent results have been obtained using three different metals chosen from the five preferred metals mentioned above. The best results have been obtained with a mixture of Nb, Bi and Mn.
  • the metals are used in the dissolved state in a solution.
  • this solution is an alcoholic solution of one or more alcoholates and / or acetates of these metals.
  • the preferred solvent is an optionally substituted aliphatic or alicyclic alcohol or a mixture of two or more of these alcohols which are miscible with each other in large proportions.
  • Saturated linear aliphatic alcohols called "lower”, that is to say those having 1 to 6 carbon atoms in their hydrocarbon chain are well suited.
  • Alcohols having from 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl alcohols are most suitable. Among these, methyl alcohol has given excellent results.
  • metallic alcoholate is intended to denote a compound of formula R-0-Me, in which Me is a metal atom and in which R denotes a linear or branched aromatic, alicyclic or aliphatic hydrocarbon group, saturated or comprising a or several unsaturations, unsubstituted or carrying one or more hydrocarbon substituents optionally comprising one or more heteroatoms in their main chain.
  • Metal alcoholates derived from an optionally substituted saturated linear aliphatic alcohol are preferred such as, for example, alcoholates derived from a lower aliphatic alcohol having less than 5 carbon atoms, such as those where R is a methyl, ethyl, n-propyl, isopropyl, n-butyl or iso-butyl group.
  • R is a methyl, ethyl, n-propyl, isopropyl, n-butyl or iso-butyl group.
  • the alcoholic solution of the metals is a solution of a mixture of alcoholates or acetates of niobium, bismuth and manganese in a lower aliphatic alcohol.
  • a solution of manganese acetate, bismuth acetate and a mixture of niobium ethylate and propylate in methyl alcohol gave the best results.
  • the quantities of metals to be used in the dissolved state are such that after impregnation and evaporation of the solution, the total content of metals other than Ti and Ba in the powder is greater than 0.5 X by weight and preferably greater than 1 X. This content should also be less than 10 and preferably less than 8 X.
  • the alcoholic solution of the metals can advantageously contain one or more carboxylic acids. Aliphatic carboxylic acids such as formic, acetic and propionic acids are well suited. Acetic acid has given good results, especially in methanolic solutions of metals.
  • the sintering of the powder is carried out at a temperature sufficient for the particles of barium titanate powder impregnated with the acetates or the alcoholates of metals to give rise to the formation of oxides of these metals at the periphery. particles.
  • This temperature will not however be too high so as to slow the diffusion of the oxides of these metals towards the core of the particles.
  • the sintering temperature will be between 1050 ° C and 1350 ° C.
  • the invention also relates to the use of the process of the invention for obtaining a powder intended for the manufacture cation of capacitors conforming to standard X7R.
  • the X7R standard designates a standard characterizing an electric capacitor whose dielectric constant does not vary by more than 15 X on either side of its value at 25 ° C in an operating temperature range from -55 ° C to + 125 ° C.
  • Example 1R (not in accordance with the invention)
  • a solution of Ti isopropylate and oleic acid was introduced into the same solvent mixture so as to achieve a molar ratio of oleic acid / Ti 0.7 and a 0.0847 M solution of Ti isopropylate.
  • a solution of Nb alcoholate in methanol previously prepared as described below was then added and a solution of manganese acetate in methanol in an amount adjusted so that the Nb / Ti molar ratio of the solution is equal to 0 , 02 and the Mn / Ti molar ratio at 0.002.
  • a solution of hydrated barium hydroxide in the methanol / isopropanol equivolumic mixture was then added with stirring in an amount adjusted so that the Ba / Ti molar ratio was equal to 1.02.
  • the precipitate formed was then dried and then calcined to 860 ° C.
  • the particles obtained were submicron (90 Y. of these had a diameter of less than 1 ⁇ m) and had an average diameter of 0.5 ⁇ m.
  • FIG. 1 The variation of the dielectric properties of the powder obtained as a function of the temperature has been plotted in graph in FIG. 1 showing on the ordinates the evolution of the dielectric constant ⁇ as a function of the temperature (in degrees C) plotted on the abscissa, the measurement being carried out with alternating current at a frequency of 1.5 kHz.
  • Figure 2 illustrates the relative variation, expressed in Z, of the capacity as a function of the temperature (dC / C25 °).
  • the ordinates of Figure 2 represent the relative variation of the capacity (dC / C25 °) and are graduated in% and the abscissas represent the temperature and are graduated in degrees Centigrade. It can be seen that the variations in the dielectric constant as a function of the temperature are too great for the powder to be usable in the manufacture of electrical capacitors conforming to the X7R standard.
  • Nb alcoholate solution 1 l of methanol and 34 g of bCls were introduced into a glass flask previously put under dry nitrogen pressure. 68.5 ml of propylene oxide were then added. so as to produce a propylene oxide / Nb molar ratio equal to 7.7 and by controlling the temperature so that it does not exceed 32 ⁇ C, after which 1 ml of triethylamine has been added. It was allowed to react at room temperature for 2 days, then the solution was heated to 40 ° C for 2 hours.
  • Example 2 (according to the invention)
  • the solution was then evaporated under reduced pressure, and the powder obtained was sintered at 1175 ° C. for 1 hour.
  • the powder obtained had an Nb / BaTi ⁇ 3 molar ratio of 0.025, a Bi / BaTi ⁇ 3 molar ratio of 0.025 and an Mn / BaTi ⁇ 3 molar ratio of 0.002.
  • the dielectric properties of the powder obtained as a function of the temperature have been plotted in graphs in FIGS. 3 and 4 showing the evolution of the dielectric constant ⁇ as a function of the temperature (in degrees C) and the variation relative capacity (in X) as a function of temperature, the measurement being carried out using alternating current at frequencies of 1.5 and 10 kHz.
  • the abscissas and the ordinates of FIG. 3 represent the same quantities as in FIG. 1 and those of FIG. 4, the same as in FIG. 2.
  • the curves in solid lines represent the properties measured at 1.5 kHz and the dashed lines, the properties measured at 10 kHz.
  • the maximum dielectric constant measured at 1.5 kHz is 2043 and corresponds to a temperature of 19 ° C, that measured at 10 kHz is 2020 and corresponds to 102 ° C. At 25 ° C, these dielectric constants are worth 2042 (at 1.5 kHz) and 2003 (at 10 kHz).
  • Example 2 was reproduced by modifying the contents of Nb, Bi and Mn so as to produce powders the contents of which follow:

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
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  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
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Abstract

A method for preparing a mixed metal oxide powder suitable for producing electrical capacitors, wherein a submicronic barium titanate powder is suspended in a solution containing one or more dissolved metals from groups IIb, IVa, IVb, Va, Vb, VIIb and VIIIb, the previously calcined barium titanate powder is impregnated with the solution, the solution is evaporated off, and the resulting powder is pressed then sintered. The method may be used to prepare mixed metal oxide powders for producing capacitors which comply with standard X7R.

Description

Procédé pour la fabrication d'une poudre d'oxydes métalliques mixtes convenant pour la réalisation de condensateurs électriques. Process for the manufacture of a powder of mixed metal oxides suitable for the production of electric capacitors.
L'invention concerne un procédé pour la fabrication de poudres d'oxydes métalliques mixtes convenant pour la réalisation de condensateurs électriques de capacité élevée et son utili¬ sation pour l'obtention d'une poudre destinée à la fabrication de condensateurs conformes à la norme X7R (Norme ANSI/EIA-198-C-1983), Les compositions d'oxydes métalliques mixtes convenant pour la réalisation de condensateurs électriques de capacité élevée sont habituellement préparées par mélange de poudres d'oxydes métalliques préalablement broyés tels que, par exemple, BaTiOβ, Nb2<-5, Bi2Û3, TJO2 , Snθ2, Mnθ2- PbO, ZnO et CoO. (brevet US-4499521 au nom de North American PHILIPS Corp.)The invention relates to a process for the manufacture of mixed metal oxide powders suitable for the production of electrical capacitors of high capacity and its use for obtaining a powder intended for the manufacture of capacitors in accordance with standard X7R (ANSI / EIA-198-C-1983 standard), Mixed metal oxide compositions suitable for producing high-capacity electric capacitors are usually prepared by mixing powders of previously ground metal oxides such as, for example, BaTiOβ , Nb2 <-5, Bi2Û3, TJO2, Snθ2, Mnθ2- PbO, ZnO and CoO. (patent US-4499521 in the name of North American PHILIPS Corp.)
La fabrication de condensateurs multicouches de haute capacité exige cependant des poudres de plus en plus fines en vue de pouvoir réaliser des couches diélectriques de plus en plus minces nécessaires à l'obtention d'une capacité élevée.The manufacture of high-capacity multilayer capacitors, however, requires increasingly fine powders in order to be able to produce increasingly thin dielectric layers necessary for obtaining a high capacity.
Les poudres obtenues par les méthodes conventionnelles connues présentent généralement des morphologies typiques des poudres broyées, avec des diamètres moyens supérieurs au μm et, de ce fait, ne permettent plus la diminution de l'épaisseur des couches diélectriques.The powders obtained by known conventional methods generally have morphologies typical of ground powders, with average diameters greater than μm and, therefore, no longer allow the thickness of the dielectric layers to be reduced.
L'invention vise à remédier aux inconvénients des procédés connus en fournissant un procédé capable de produire des poudres submicroniques aptes à la fabrication de couches diélectriques ultra-minces pour condensateurs multicouches de capacité élevée. A cet effet, l'invention concerne un procédé pour la fabri¬ cation d'une poudre d'oxydes métalliques mixtes convenant pour la réalisation de condensateurs électriques de haute capacité selon lequel on met en oeuvre une poudre submicronique de titanate de baryum et un ou plusieurs oxydes de métaux des groupes Ilb, IVa, IVb, Va, Vb, Vllb et VlIIb. Selon l'invention, on met en suspension la poudre de titanate de baryum préalablement calcinée dans une solution contenant les métaux à l'état dissous, on imprègne la poudre de titanate de baryum avec la solution, on évapore la solution et on soumet la poudre obtenue à un pressage suivi d'un frittage. 5 Par poudre d'oxydes métalliques mixtes, on entend désigner une poudre comprenant des oxydes d'au moins deux métaux différents.The invention aims to overcome the drawbacks of known methods by providing a method capable of producing submicron powders suitable for the manufacture of ultra-thin dielectric layers for high-capacity multilayer capacitors. To this end, the invention relates to a process for the fabrication of a powder of mixed metal oxides suitable for the production of high capacity electric capacitors according to which a submicron powder of barium titanate and one or several metal oxides of groups Ilb, IVa, IVb, Va, Vb, Vllb and VlIIb. According to the invention, the previously calcined barium titanate powder is suspended in a solution containing the metals in the dissolved state, the barium titanate powder is impregnated with the solution, the solution is evaporated and the powder obtained is subjected to pressing followed by sintering. By mixed metal oxide powder is meant a powder comprising oxides of at least two different metals.
Les condensateurs électriques de capacité élevée qui peuvent être fabriqués selon le procédé de l'invention sont des conden-The high capacitance electric capacitors which can be manufactured according to the process of the invention are condens
10 sateurs multicouches dont chacune des couches est constituée d'un matériau diélectrique dont la constante diélectrique ε à 25 °C est supérieure à environ 1800 et, de préférence, supérieure à environ 2000. Cette constante diélectrique à 25 °C peut être très élevée. En pratique, elle ne dépasse le plus souvent pas une10 multilayer sators each of which layers is made of a dielectric material whose dielectric constant ε at 25 ° C is greater than approximately 1800 and, preferably, greater than approximately 2000. This dielectric constant at 25 ° C can be very high. In practice, it usually does not exceed one
15 valeur d'environ 5000. 15 value of about 5000.
La poudre submicronique de titanate de baryum que l'on met en oeuvre selon l'invention peut être obtenue par toute méthode adéquate permettant d'obtenir des grains de titanate de baryum de granulométrie régulière dont le diamètre moyen se situe en-deçàThe submicron barium titanate powder which is used according to the invention can be obtained by any suitable method making it possible to obtain barium titanate grains of regular particle size whose average diameter is below
~~ du μm.~~ μm.
Dans un mode de réalisation de l'invention qui est préféré, on prépare la poudre submicronique de titanate de baryum par coprécipitation résultant du mélange d'une solution alcoolique d'acide oxalique et d'alcoolate de titane avec une solutionIn a preferred embodiment of the invention, the submicron barium titanate powder is prepared by coprecipitation resulting from the mixture of an alcoholic solution of oxalic acid and titanium alcoholate with a solution
~- d'hydroxyde ou d'acétate de baryum telle qu'elle a été décrite dans la demande de brevet belge No. 9100836 au nom de SOLVAY & Cie (Société Anonyme).~ - barium hydroxide or acetate as described in Belgian patent application No. 9100836 in the name of SOLVAY & Cie (Société Anonyme).
Avantageusement, on choisira le méthanol pour solvant de l'acide oxalique et de l'alcoolate de titane.Advantageously, choose methanol as solvent for oxalic acid and titanium alcoholate.
30 Dans un autre mode de réalisation de l'invention qui est également préféré, on prépare la poudre submicronique de titanate de baryum par hydrolyse d'un alcoolate de titane en présence d'un hydroxyde de baryum hydraté et d'un acide carboxylique contenant plus de 6 atomes de carbone dans sa molécule telle qu'elle a étéIn another embodiment of the invention which is also preferred, the submicron barium titanate powder is prepared by hydrolysis of a titanium alcoholate in the presence of a hydrated barium hydroxide and a carboxylic acid containing more of 6 carbon atoms in its molecule as it was
35 décrite dans la demande de brevet français No. 87.09116 au nom de SOLVAY & Cie (Société Anonyme). Selon cet autre mode de réalisation de l'invention, on sélectionnera de préférence l'acide carboxylique parmi les acides aliphatiques à chaîne carbonée linéaire. L'acide oléique a donné d'excellents résultats. Les métaux des groupes Ilb, IVa, IVb, Va, Vb, Vllb et VlIIb du tableau périodique des éléments seront avantageusement choisis parmi le silicium, le niobium, le bismuth, le manganèse, et le cobalt. Il est impératif de mettre en oeuvre au moins un et, de préférence, au moins deux de ces métaux. D'excellents résultats ont été obtenus en mettant en oeuvre trois métaux différents choisis parmi les cinq métaux préférés cités plus haut. Les meilleurs résultats ont été obtenus avec un mélange de Nb, de Bi et de Mn.35 described in French patent application No. 87.09116 in the name of SOLVAY & Cie (Société Anonyme). According to this other embodiment of the invention, the carboxylic acid will preferably be selected from aliphatic acids with a linear carbon chain. Oleic acid has given excellent results. The metals of groups Ilb, IVa, IVb, Va, Vb, Vllb and VlIIb of the periodic table of the elements will advantageously be chosen from silicon, niobium, bismuth, manganese, and cobalt. It is imperative to use at least one and preferably at least two of these metals. Excellent results have been obtained using three different metals chosen from the five preferred metals mentioned above. The best results have been obtained with a mixture of Nb, Bi and Mn.
Selon l'invention, les métaux sont mis en oeuvre à l'état dissous dans une solution. De préférence, cette solution est une solution alcoolique d'un ou de plusieurs alcoolates et/ou acétates de ces métaux. Le solvant préféré est un alcool ali- phatique ou alicyclique éventuellement substitué ou un mélange de deux ou plusieurs de ces alcools miscibles l'un dans l'autre dans de larges proportions. Les alcools aliphatiques linéaires saturés dits "inférieurs", c'est-à-dire ceux comportant 1 à 6 atomes de carbone dans leur chaîne hydrocarbonée conviennent bien. Les alcools comportant de 1 à 4 atomes de carbone, tels que les alcools méthylique, éthylique, n-propylique, isopropylique, n-butylique et isobutylique conviennent le mieux. Parmi ces derniers, l'alcool méthylique a donné d'excellents résultats.According to the invention, the metals are used in the dissolved state in a solution. Preferably, this solution is an alcoholic solution of one or more alcoholates and / or acetates of these metals. The preferred solvent is an optionally substituted aliphatic or alicyclic alcohol or a mixture of two or more of these alcohols which are miscible with each other in large proportions. Saturated linear aliphatic alcohols called "lower", that is to say those having 1 to 6 carbon atoms in their hydrocarbon chain are well suited. Alcohols having from 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl alcohols are most suitable. Among these, methyl alcohol has given excellent results.
Selon l'invention, par alcoolate métallique, on entend désigner un composé de formule R-0-Me, dans laquelle Me est un atome de métal et où R désigne un groupement hydrocarboné aromatique, alicyclique ou aliphatique linéaire ou ramifié, saturé ou comportant une ou plusieurs insaturations, non substitué ou portant un ou plusieurs substituants hydrocarbonés comportant éventuellement un ou plusieurs hétéroatomes dans leur chaîne principale. Les alcoolates métalliques dérivés d'un alcool aliphatique linéaire saturé, éventuellement substitué, sont préférés tels que, par exemple, les alcoolates dérivés d'un alcool aliphatique inférieur comportant moins de 5 atomes de carbone, comme ceux où R est un groupement méthyle, éthyle, n-propyle, isopropyle, n-butyle ou iso-butyle. On peut, de manière indifférente, utiliser un seul alcoolate métallique ou un mélange de plusieurs alcoolates,According to the invention, by metallic alcoholate is intended to denote a compound of formula R-0-Me, in which Me is a metal atom and in which R denotes a linear or branched aromatic, alicyclic or aliphatic hydrocarbon group, saturated or comprising a or several unsaturations, unsubstituted or carrying one or more hydrocarbon substituents optionally comprising one or more heteroatoms in their main chain. Metal alcoholates derived from an optionally substituted saturated linear aliphatic alcohol are preferred such as, for example, alcoholates derived from a lower aliphatic alcohol having less than 5 carbon atoms, such as those where R is a methyl, ethyl, n-propyl, isopropyl, n-butyl or iso-butyl group. One can, indifferently, use a single metal alcoholate or a mixture of several alcoholates,
Dans un mode de réalisation préféré du procédé selon l'invention, la solution alcoolique des métaux est une solution d'un mélange d'alcoolates ou d'acétates de niobium, de bismuth et de manganèse dans un alcool aliphatique inférieur. Une solution d'acétate de manganèse, d'acétate de bismuth et d'un mélange d'éthylate et de propylate de niobium dans l'alcool méthylique a donné les meilleurs résultats.In a preferred embodiment of the process according to the invention, the alcoholic solution of the metals is a solution of a mixture of alcoholates or acetates of niobium, bismuth and manganese in a lower aliphatic alcohol. A solution of manganese acetate, bismuth acetate and a mixture of niobium ethylate and propylate in methyl alcohol gave the best results.
Dans le procédé de l'invention, les quantités de métaux à mettre en oeuvre à l'état dissous sont telles qu'après impré- gnation et evaporation de la solution, la teneur totale en métaux autres que le Ti et le Ba dans la poudre soit supérieure à 0,5 X en poids et, de préférence, supérieure à 1 X . Il convient aussi que cette teneur soit inférieure à 10 et, de préférence, inférieure à 8 X . Selon une variante intéressante au procédé selon l'inven¬ tion, la solution alcoolique des métaux peut avantageusement contenir un ou plusieurs acides carboxyliques. Les acides carboxyliques aliphatiques tels que les acides formique, acétique et propionique conviennent bien. L'acide acétique a donné de bons résultats, en particulier dans les solutions méthanoliques des métaux.In the process of the invention, the quantities of metals to be used in the dissolved state are such that after impregnation and evaporation of the solution, the total content of metals other than Ti and Ba in the powder is greater than 0.5 X by weight and preferably greater than 1 X. This content should also be less than 10 and preferably less than 8 X. According to an advantageous variant of the process according to the invention, the alcoholic solution of the metals can advantageously contain one or more carboxylic acids. Aliphatic carboxylic acids such as formic, acetic and propionic acids are well suited. Acetic acid has given good results, especially in methanolic solutions of metals.
Selon l'invention, le frittage de la poudre s'effectue à une température suffisante pour que les particules de poudre de titanate de baryum imprégnées par les acétates ou les alcoolates de métaux donnent lieu à la formation d'oxydes de ces métaux à la périphérie des particules. Cette température ne sera cependant pas trop élevée de façon à freiner la diffusion des oxydes de ces métaux vers le coeur des particules. En pratique, la température de frittage se situera entre 1050 °C et 1350 °C. L'invention concerne aussi l'utilisation du procédé de l'invention pour l'obtention d'une poudre destinée à la fabri- cation de condensateurs conformes à la norme X7R.According to the invention, the sintering of the powder is carried out at a temperature sufficient for the particles of barium titanate powder impregnated with the acetates or the alcoholates of metals to give rise to the formation of oxides of these metals at the periphery. particles. This temperature will not however be too high so as to slow the diffusion of the oxides of these metals towards the core of the particles. In practice, the sintering temperature will be between 1050 ° C and 1350 ° C. The invention also relates to the use of the process of the invention for obtaining a powder intended for the manufacture cation of capacitors conforming to standard X7R.
La norme X7R désigne une norme caractérisant un condensateur électrique dont la constante diélectrique ne varie pas de plus de 15 X de part et d'autre de sa valeur à 25 °C dans un intervalle de températures de fonctionnement allant de -55 °C à +125 °C.The X7R standard designates a standard characterizing an electric capacitor whose dielectric constant does not vary by more than 15 X on either side of its value at 25 ° C in an operating temperature range from -55 ° C to + 125 ° C.
Les exemples qui suivent sont donnés dans le but d'illustrer l'invention, sans pour autant en limiter sa portée. L'exemple 1R est donné à titre de comparaison. Les exemples 2 à 7 ont été réalisés conformément à l'invention. Exemple 1R : (non conforme à l'invention)The examples which follow are given for the purpose of illustrating the invention, without however limiting its scope. Example 1R is given for comparison. Examples 2 to 7 were carried out in accordance with the invention. Example 1R: (not in accordance with the invention)
Dans un réacteur contenant un solvant formé d'un mélange équivolumique de méthanol et d'isopropanol, on a introduit une solution d'isopropylate de Ti et d'acide oléique dans le même mélange solvant de façon à réaliser un rapport molaire acide oléique/Ti de 0,7 et une solution 0,0847 M en isopropylate de Ti. On a ensuite ajouté une solution d'alcoolate de Nb dans le méthanol préalablement préparée comme décrit ci-dessous et une solution d'acétate de manganèse dans le méthanol en quantité réglée pour que le rapport molaire Nb/Ti de la solution soit égal à 0,02 et le rapport molaire Mn/Ti à 0,002.In a reactor containing a solvent formed from an equivolumic mixture of methanol and isopropanol, a solution of Ti isopropylate and oleic acid was introduced into the same solvent mixture so as to achieve a molar ratio of oleic acid / Ti 0.7 and a 0.0847 M solution of Ti isopropylate. A solution of Nb alcoholate in methanol previously prepared as described below was then added and a solution of manganese acetate in methanol in an amount adjusted so that the Nb / Ti molar ratio of the solution is equal to 0 , 02 and the Mn / Ti molar ratio at 0.002.
On a ensuite ajouté sous agitation une solution d'hydroxyde de baryum hydraté dans le mélange équivolumique méthanol/ isopropanol en quantité réglée pour que le rapport molaire Ba/Ti soit égal à 1,02. On a ensuite séché le précipité formé puis on l'a calciné jusqu'à 860 °C.A solution of hydrated barium hydroxide in the methanol / isopropanol equivolumic mixture was then added with stirring in an amount adjusted so that the Ba / Ti molar ratio was equal to 1.02. The precipitate formed was then dried and then calcined to 860 ° C.
Les particules obtenues étaient submicroniques (90 Y. de celles-ci avaient un diamètre inférieur à 1 μm) et présentaient un diamètre moyen de 0,5 μm.The particles obtained were submicron (90 Y. of these had a diameter of less than 1 μm) and had an average diameter of 0.5 μm.
La variation des propriétés diélectriques de la poudre obtenue en fonction de la température a été portée en graphique à la figure 1 montrant en ordonnées l'évolution de la constante diélectrique ε en fonction de la température (en degrés C) portée en abscisses, la mesure étant réalisée en courant alternatif à une fréquence de 1,5 kHz. La figure 2 illustre la variation relative, exprimée en Z, de la capacité en fonction de la température (dC/C25°). Les ordonnées de la figure 2 représentent la variation relative de la capacité (dC/C25 °) et sont graduées en % et les abscisses représentent la température et sont graduées en degrés Centigrade. On voit que les variations de la constante diélectrique en fonction de la température sont trop importantes pour que la poudre soit utilisable dans la fabrication de condensateurs électriques conformes à la norme X7R.The variation of the dielectric properties of the powder obtained as a function of the temperature has been plotted in graph in FIG. 1 showing on the ordinates the evolution of the dielectric constant ε as a function of the temperature (in degrees C) plotted on the abscissa, the measurement being carried out with alternating current at a frequency of 1.5 kHz. Figure 2 illustrates the relative variation, expressed in Z, of the capacity as a function of the temperature (dC / C25 °). The ordinates of Figure 2 represent the relative variation of the capacity (dC / C25 °) and are graduated in% and the abscissas represent the temperature and are graduated in degrees Centigrade. It can be seen that the variations in the dielectric constant as a function of the temperature are too great for the powder to be usable in the manufacture of electrical capacitors conforming to the X7R standard.
Préparation de la solution d'alcoolate de Nb : Dans un ballon en verre préalablement mis sous pression d'azote sec, on a introduit 1 1 de méthanol et 34 g de bCls- On a ensuite ajouté 68,5 ml d'oxyde de propylene de façon à réaliser un rapport molaire oxyde de propylène/Nb égal à 7,7 et en contrôlant la température afin qu'elle ne dépasse pas 32 βC, après quoi, on a encore ajouté 1 ml de triéthylamine. On a laissé réagir à température ambiante pendant 2 jours, puis on a chauffé la solution à 40 °C pendant 2 heures. Exemple 2 : (conforme à l'invention)Preparation of the Nb alcoholate solution: 1 l of methanol and 34 g of bCls were introduced into a glass flask previously put under dry nitrogen pressure. 68.5 ml of propylene oxide were then added. so as to produce a propylene oxide / Nb molar ratio equal to 7.7 and by controlling the temperature so that it does not exceed 32 β C, after which 1 ml of triethylamine has been added. It was allowed to react at room temperature for 2 days, then the solution was heated to 40 ° C for 2 hours. Example 2: (according to the invention)
Dans un ballon en verre, on a introduit, successivement : 2,33 g de BaTiOβ obtenu par cohydrolyse en présence d'acide oléique et préalablement calciné à 850 °C pendant 2 heures; 30 ml de méthanol;In a glass flask, there were successively introduced: 2.33 g of BaTiOβ obtained by cohydrolysis in the presence of oleic acid and previously calcined at 850 ° C for 2 hours; 30 ml of methanol;
2,05 ml d'alcoolate de Nb en solution 0,122 M dans le méthanol préparé comme à l'exemple 1R; 25,0 ml de Bi(CH3COO)3 en solution 0,01 M dans un mélange de méthanol et d'acide acétique et 2,0 ml de Mn(CH3C00)2 en solution 0,01M dans le méthanol.2.05 ml of Nb alcoholate in 0.122 M solution in methanol prepared as in Example 1R; 25.0 ml of Bi (CH3COO) 3 in 0.01 M solution in a mixture of methanol and acetic acid and 2.0 ml of Mn (CH3C00) 2 in 0.01M solution in methanol.
On a ensuite procédé à l'évaporation sous pression réduite de la solution, et au frittage de la poudre obtenue à 1175 °C pendant 1 heure. La poudre obtenue présentait un rapport molaire Nb/BaTiθ3 de 0,025, un rapport molaire Bi/BaTiθ3 de 0,025 et un rapport molaire Mn/BaTiθ3 de 0,002.The solution was then evaporated under reduced pressure, and the powder obtained was sintered at 1175 ° C. for 1 hour. The powder obtained had an Nb / BaTiθ3 molar ratio of 0.025, a Bi / BaTiθ3 molar ratio of 0.025 and an Mn / BaTiθ3 molar ratio of 0.002.
Les propriétés diélectriques de la poudre obtenue en fonction de la température ont été portées en graphiques aux figures 3 et 4 montrant l'évolution de la constante diélectrique ε en fonction de la température (en degrés C) et la variation relative de la capacité (en X) en fonction de la température, la mesure étant réalisée en courant alternatif aux fréquences de 1,5 et 10 kHz. Les abscisses et les ordonnées de la figure 3 repré¬ sentent les mêmes grandeurs qu'à la figure 1 et celles de la figure 4, les mêmes qu'à la figure 2. Les courbes en traits pleins représentent les propriétés mesurées à 1,5 kHz et les courbes en traits interrompus, les propriétés mesurées à 10 kHz. La constante diélectrique maximum mesurée à 1,5 kHz vaut 2043 et correspond à une température de 19 °C, celle mesurée à 10 kHz vaut 2020 et correspond à 102 °C. A 25 °C, ces constantes diélectriques valent 2042 (à 1,5 kHz) et 2003 (à 10 kHz).The dielectric properties of the powder obtained as a function of the temperature have been plotted in graphs in FIGS. 3 and 4 showing the evolution of the dielectric constant ε as a function of the temperature (in degrees C) and the variation relative capacity (in X) as a function of temperature, the measurement being carried out using alternating current at frequencies of 1.5 and 10 kHz. The abscissas and the ordinates of FIG. 3 represent the same quantities as in FIG. 1 and those of FIG. 4, the same as in FIG. 2. The curves in solid lines represent the properties measured at 1.5 kHz and the dashed lines, the properties measured at 10 kHz. The maximum dielectric constant measured at 1.5 kHz is 2043 and corresponds to a temperature of 19 ° C, that measured at 10 kHz is 2020 and corresponds to 102 ° C. At 25 ° C, these dielectric constants are worth 2042 (at 1.5 kHz) and 2003 (at 10 kHz).
On voit que les variations de la capacité en fonction de la température sont faibles et inférieures à 10 X dans toute la gamme de températures envisagées. La poudre obtenue peut donc être utilisée dans la fabrication de condensateurs électriques conformes à la norme X7R.It can be seen that the variations in capacity as a function of the temperature are small and less than 10 X over the entire range of temperatures envisaged. The powder obtained can therefore be used in the manufacture of electrical capacitors in accordance with the X7R standard.
La solution d'acétate de Bi dans le mélange méthanol et acide acétique a été préparée comme suit :The solution of Bi acetate in the methanol and acetic acid mixture was prepared as follows:
Dans un erlenmeyer, on a introduit 1,42 g de Bi(CH3C00)3, 17,5 ml d'acide acétique et 50 ml de méthanol. Après avoir chauffé le mélange à reflux, on a ensuite ajouté 300 ml de méthanol sous agitation.1.42 g of Bi (CH3C00) 3, 17.5 ml of acetic acid and 50 ml of methanol were introduced into an Erlenmeyer flask. After heating the mixture to reflux, 300 ml of methanol was then added with stirring.
Exemples 3 à 6 : (conformes à l'invention)Examples 3 to 6: (in accordance with the invention)
On a reproduit l'exemple 2 en modifiant les teneurs en Nb, en Bi et en Mn de façon à réaliser des poudres dont les teneurs suivent :Example 2 was reproduced by modifying the contents of Nb, Bi and Mn so as to produce powders the contents of which follow:
Figure imgf000009_0001
Figure imgf000009_0001
Les résultats obtenus ont été portés en graphiques aux figures 5 à 12 qui donnent l'évolution de la constante diélectrique ε en fonction de la température (en degrés C) (figures 5, 7, 9 et 11) et la variation relative de la capacité en fonction de la température (figures 6, 8, 10 et 12), la mesure étant réalisée en courant alternatif aux fréquences de 1,5 et 10 kHz. Les abscisses et ordonnées des figures 5, 7, 9 et 11 ont les mêmes significations que celles de la figure 1, celles des figures 6, 8, 10 et 12, les mêmes que celles de la figure 2. Les courbes en traits pleins représentent les propriétés mesurées à 1,5 kHz et les courbes en traits interrompus, les propriétés mesurées à 10 kHz, excepté aux figures 11 et 12 où la mesure a été réalisée à 100 kHz plutôt qu'à 10 kHz. Les valeurs maxima et les valeurs à 25 °C des constantes diélectriques mesurées ont été les suivantes :The results obtained have been plotted in graphs Figures 5 to 12 which give the evolution of the dielectric constant ε as a function of the temperature (in degrees C) (Figures 5, 7, 9 and 11) and the relative variation of the capacity as a function of the temperature (Figures 6, 8, 10 and 12), the measurement being carried out with alternating current at frequencies of 1.5 and 10 kHz. The abscissa and ordinate of Figures 5, 7, 9 and 11 have the same meanings as those of Figure 1, those of Figures 6, 8, 10 and 12, the same as those of Figure 2. The curves in solid lines represent the properties measured at 1.5 kHz and the dashed lines, the properties measured at 10 kHz, except in FIGS. 11 and 12 where the measurement was carried out at 100 kHz rather than at 10 kHz. The maximum values and the values at 25 ° C. of the dielectric constants measured were as follows:
Figure imgf000010_0001
Figure imgf000010_0001
(*) : valeurs mesurées à 100 kHz On voit que les variations de la capacité en fonction de la température sont dans tous les cas comprises entre -15 et +15 X dans toute la gamme de températures envisagées. Les poudres obtenues peuvent donc toutes être utilisées dans la fabrication de condensateurs électriques conformes à la norme X7R. (*): values measured at 100 kHz We see that the variations in capacity as a function of temperature are in all cases between -15 and +15 X over the whole range of temperatures envisaged. The powders obtained can therefore all be used in the manufacture of electrical capacitors in accordance with the X7R standard.

Claims

R E V E N D I C A T I O N S R E V E N D I C A T I O N S
1 - Procédé pour la fabrication d'une poudre d'oxydes métalliques mixtes convenant pour la réalisation de condensateurs électriques de haute capacité selon lequel on met en oeuvre une poudre submicronique de titanate de baryum et un ou plusieurs oxydes de métaux des groupes Ilb, IVa, IVb, Va, Vb, Vllb et VlIIb, caractérisé en ce qu'on met en suspension la poudre de titanate de baryum préalablement calcinée dans une solution contenant les métaux à l'état dissous, que l'on imprègne la poudre de titanate de baryum avec la solution, que l'on évapore la solution et que l'on soumet la poudre obtenue à un pressage suivi d'un frittage.1 - Process for the manufacture of a powder of mixed metal oxides suitable for the production of high capacity electric capacitors according to which a submicron powder of barium titanate and one or more metal oxides of groups Ilb, IVa are used , IVb, Va, Vb, Vllb and VlIIb, characterized in that the barium titanate powder, previously calcined, is suspended in a solution containing the metals in the dissolved state, which the titanate powder is impregnated with. barium with the solution, the solution is evaporated and the powder obtained is subjected to pressing followed by sintering.
2 - Procédé selon la revendication 1, caractérisé en ce que la poudre de titanate de baryum est obtenue par coprécipitation résultant du mélange d'une solution alcoolique d'acide oxalique et d'alcoolate de titane avec une solution d'hydroxyde ou d'acétate de baryum.2 - Process according to claim 1, characterized in that the barium titanate powder is obtained by coprecipitation resulting from the mixture of an alcoholic solution of oxalic acid and titanium alcoholate with a hydroxide or acetate solution barium.
3 - Procédé selon la revendication 1, caractérisé en ce que la poudre de titanate de baryum est obtenue par hydrolyse d'un alcoolate de titane en présence d'un hydroxyde de baryum hydraté et d'un acide carboxylique contenant plus de 6 atomes de carbone dans sa molécule.3 - Process according to claim 1, characterized in that the barium titanate powder is obtained by hydrolysis of a titanium alcoholate in the presence of a hydrated barium hydroxide and a carboxylic acid containing more than 6 carbon atoms in its molecule.
4 - Procédé selon la revendication 3, caractérisé en ce que l'acide carboxylique est l'acide oléique.4 - Process according to claim 3, characterized in that the carboxylic acid is oleic acid.
5 _ Procédé selon l'une quelconque des revendications 1 à 4, caractérisé en ce que les métaux sont sélectionnés parmi le niobium, le bismuth, le manganèse et le cobalt.5 _ Process according to any one of claims 1 to 4, characterized in that the metals are selected from niobium, bismuth, manganese and cobalt.
6 - Procédé selon l'une quelconque des revendications 1 à 5, caractérisé en ce que la solution contenant les métaux à l'état dissous est une solution alcoolique d'un ou plusieurs alcoolates et/ou acétates de ces métaux.6 - Process according to any one of claims 1 to 5, characterized in that the solution containing the metals in the dissolved state is an alcoholic solution of one or more alcoholates and / or acetates of these metals.
7 - Procédé selon les revendications 5 et 6, caractérisé en ce que la solution alcoolique contient un mélange d'alcoolates ou d'acétates de niobium, de bismuth et de manganèse.7 - Method according to claims 5 and 6, characterized in that the alcoholic solution contains a mixture of alcoholates or acetates of niobium, bismuth and manganese.
8 - Procédé selon l'une quelconque des revendications 1 à 7, caractérisé en ce que la solution alcoolique est une solution méthanolique.8 - Process according to any one of claims 1 to 7, characterized in that the alcoholic solution is a methanolic solution.
9 - Procédé selon la revendication 8, caractérisé en ce que la solution méthanolique contient un acide carboxylique sélec¬ tionné parmi l'acide formique, l'acide acétique et l'acide propionique.9 - Process according to claim 8, characterized in that the methanolic solution contains a carboxylic acid selected from formic acid, acetic acid and propionic acid.
10 - Utilisation du procédé selon l'une quelconque des revendications 1 à 9 pour la fabrication de poudres d'oxydes métalliques mixtes destinées à la réalisation de condensateurs conformes à la norme X7R. 10 - Use of the method according to any one of claims 1 to 9 for the manufacture of mixed metal oxide powders intended for the production of capacitors in accordance with standard X7R.
PCT/EP1993/000271 1992-02-14 1993-02-04 Method for preparing a mixed metal oxide powder suitable for producing electrical capacitors WO1993016012A1 (en)

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