KR970004271B1 - Doped batio3 based composition - Google Patents

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Description

Doped BaTiO₃Base Composition

The first turn following formula _{1.02Ba 0.811 Pb 0.105 Ca 0.081 Sr 0.003} O · Ti 0.832 Sn 0.074 Zr 0.094 O 2 · 0.012CoO · 0.009MnO · 0.005Nb infinitesimal multiple dopants of dispersibility of the present invention represented by the ₂ O ₅ 50,000x magnified transmission electron micrograph of a composite composite poform.

2 is a 50,000-fold magnification transmission electron micrograph of a single dopant compound barium titanate copolymer represented by the following general formula 0.998Ba _0.792 Pb _0.104 Ca _0.098 Sr _{0.006 O.Ti 0.831} Sn _0.070 Zr _0.099 O ₂ .0.032CoO.

FIELD OF THE INVENTION The present invention relates to barium titanate based compositions, and more particularly to dispersible, finely doped barium titanate copolymers having a narrow particle size distribution.

Barium titanate based compositions are widely used in the electronics industry to produce capacitors, capacitors and PTCR (positive temperature coefficient of resistance) devices. Barium titanate is particularly useful and versatile for electronic applications because its electrical properties can be substantially modified by the incorporation of additives and / or conduits. Common additives used are MAO ₃ having a perovskite structure ₃ BaTiO times (where, M is a divalent cation, A is a tetravalent cation Im) are compounds. Representative additives include titanates, zirconates and tartarates of calcium, strontium, barium and lead. The additives are at least 3 mole percent of the BaTiO ₃ based formulation. Dopants include a wide range of metal oxides. In general, they are less than 5 mole percent of the total BaTiO ₃ based formulation. The dopant (s) used are preferably fully or partially miscible in the taritite grating or are unmiscible in the grating. Examples of the dopants used include oxides of La, lanthanide, Y, Nb, Ta, Cu, Mo, W, Mn, Fe, Co, Ni, Zn, Al, Si, Sb and Bi.

In commercial practice, barium titanate based formulations may be mixed with the required pure titanates, zirconates, tartarates and dopants, or oxides or oxide precursors (eg carbonates) of suitable stoichiometric amounts of barium, calcium, titam, etc. It is prepared by directly preparing the desired powder by high temperature solid state reaction of an intimate mixtrue) of hydroxide or nitrate. Pure titanates, zirconates, tartarates and the like are also typically prepared by high temperature solid state reaction methods.

Although the method for producing the barium titanate and barium titanate-based compositions by solid phase reaction in a linear technique is relatively simple, there are various inconveniences. First, the milling step acts as a source of contaminants that can adversely affect electrical properties. Second, compositional non-uniformity due to incomplete mixing of the microscale can lead to undesirable phase formation, such as off-barot titanate (Ba ₂ Ti ₄ ), which can increase water sensitive properties. Third, significant particle growth and interparticle sintering occur during calcination. As a result, the milled product consists of crushed aggregates of irregular shape with a wide particle size distribution in the range of about 0.2-10 microns. Moreover, the unbaked bodies formed from such agglomerated powders having a wide range of agglomerate particle sizes require high sintering temperatures and have been demonstrated to provide sinters with a wide range of particle size distributions.

Various methods have been developed to overcome the limitations of the conventional solid state reaction method. Precipitation of doped barium titanyl oxalate, partially substituted with strontium or lead instead of doped barium titanyl oxalate or barium, and also with zirconium instead of titanium, is described in Gallaghher et al. Preparation of Semiconducting Titanates by Chemical Methods by J. Amer. Chem. Soc., 46, 359 (1963), Schrey, "Effect of pH on the Chemical Preparation of Barium-Strontium Titanate" J. Amer. Cer. Soc., 48, 401 (1965 ) and binsen Genie "dough chemical manufacture of a ping _{BaTiO 3 (Chemical Preparation of Doped BaTiO} 3)" of (vincenzini), Proceedings of the Twelfth Int. I conf., Science of Ceramics, Vol. 12, 151 (1983) and the like. Oxalate decomposes at high temperatures to form a doped barium titanate based composition. US Patent No. 3,637,531 describes a method of forming a semisolid that is converted to a desired titanate based product by calcination by heating a single solution of dopant, titanium compound and alkaline earth metal salt. US Pat. No. 4,537,865 describes a hydrous oxide precipitation of Ti, Zr, Sn or Pb and a method of mixing the hydrous oxide of a dopant with an aqueous slurry of precipitated carbonates of Ba, Sr, Ca or Mg. The solid is calcined to obtain the required product. Kakegawa et al., "Synthesis of Nb-doped Barium Titanate Semiconductor by a Wet-Dry Combination Technigues" by wet-dry mixing technology. Mat. Sci. Lets., 4, 1266 (1985), describes similar synthetic methods.

Et Mulder (Mulder) [ "Preparation of BaTiO ₃ and other ceramic powder according to the citric acid salt co-precipitation in an alcohol _{(Preparation of BaTiO 3 and Other Ceramic} Powders by Coprecipitation of Citrates in an Alcohol)", Ceramic Bulltin, 49, 990-993 (1970), a doped BaTiO ₃ and BaTiO ₃ based product was prepared by spraying an aqueous solution of citrate or formate of the components in alcohol to dehydrate and co-precipitate. The product obtained by calcining the cocipitated citrate or formate powder consists mainly of compact globules having a particle size in the range of 3-10 microns.

US Pat. No. 4,061,583 describes doped BaTiO ₃ based compositions prepared by adding a nitrate or chloride solution of essential components to an aqueous alkaline solution containing hydrogen peroxide.

Degradation of the tubular product containing the precipitate at about 100 ° C. results in the formation of an amorphous BaTiO ₃ based composition. The amorphous product is calcined to about 600 ° C. to obtain crystalline powder. Unfortunately the primary particle size of the product is not characterized. Simulation of some of the examples given in this patent showed that the primary particle size of the amorphous powder was substantially less than 0.05 microns. Analysis of the product by transmission electron micrograph (TEM) showed that the primary particles of the product calcined at 600 ° C. were aggregated.

In this example by a representative prior art method, calcination is carried out to complete particle synthesis of the desired composition. For the reasons mentioned above, this high temperature operation is detrimental because it produces agglomerated products that provide smaller agglomerate fragments with a wider particle size distribution after grinding.

U.S. Patent Nos. 4,233,282, 4,293,534 and 4,487,755 disclose BaTiO ₃ and BaTiO ₃ base compositions through a molten salt reaction in which Ba is partially substituted by Sr and Ti is partially substituted by Zr. It is described in the method. The product is characterized by chemically uniform, relatively monodisperse microcrystals. Doped BaTiO ₃ based products were not synthesized. Yoon (Yoon), such as described in "in the semiconducting BaTiO ₃ PTCR effect influence (Influence of the PRCR Effect in Semiconductive BaTiO _3)" of, Mat. Res. Bul., 21, 1429 (1986), disclose a product having a composition of Ba _(0.900-x) Sr _0.100 Sb _x Tio ₃ (where x has values of 0.001, 0.002, 0.003 and 0.004 ₎ by using a molten salt method A method of synthesizing is described. Products prepared from the molten salt method have a greater effect on PRCR in their resistance-temperature characteristics, greater resistance at room temperature and current-time than control specimens formed from powders produced by pixelating a mixture of oxides and oxide precursors. A larger current change was shown in the characteristics. These differences are due to the use of KCI in molten salt synthesis and the smaller particle size and particle size distribution of the particles in the sample derived. Molten salt based synthesis can be used to provide extremely doped products with narrow particle size distribution, but the powder is inevitably contaminated with alkali metal because the molten salt consists of alkali metal salts. Of course, alkali metals are harmful pollutants in most electronic applications.

Various aqueous based methods have also been described for preparing BaTiO ₃ and BaTiO ₃ based compositions wherein Ba is partially substituted by Sr and Ti is Sn or possibly partially substituted by Zr. The process described in US Pat. No. 3,577,487 produced titanated, tartarate, zigconate and / or hafnium salts of doped multicomponent alkaline earth metals and / or Pb (II). In this case, the co-precipitated hydrogel is treated with alkaline earth metal hydroxides and subjected to the same treatment steps as those used for the production of BaTiO ₃ , or the required gel and alkaline earth metal hydroxides are added to the preformed slurry of BaTiO ₃ and Then, fluid energy milling and calcination are performed. Unfortunately, the product is not characterized before fluid energy milling. Experience has shown, however, that a doped multicomponent product must have a comparative area of at least 20 m ² / g, indicating that the powder primary particle size is less than about 0.05 microns before milling. Even after fluid energy milling at outlet temperatures above about 426.7 ° C. (800 ° F.), the multicomponent products cited in the Examples had specific surface areas in excess of 18 m ² / g or more. The calcined face specific surface area is further reduced. For the above reasons, this will cause the formation of agglomerated products.

At the same time, the inventors of the United States of the United States Patent Application No. 859,577

Ba _{(1-x-x'-x ")} M _x M '_x'M" _{X "} Ti _(1-y-y'-y") A _y A '_y' A "_y" O ₃

Multicomponent powders are shown. Wherein M is Pb (II), M 'is Ca (II), M "is Sr (II), A is Sn (IV), A is Zr (IV), and A' is Hf (IV), x, x ', x "and y, y', y" represent the atomic fraction of divalent and tetravalent cations, respectively, which are (x + x '+ x ") or (y + y '+ y ") has a value of 0 to 0.3 independently, unless the sum of them exceeds 0.4. The above products having nominal stoichiometric quantities are manufactured by the general hydrothermal method and Coforms are characterized by stoichiometric, dispersible, subtle, and narrow particle size distributions.

Doping of the barium titanate copolymer was not studied in co-pending US patent application 859,577. Therefore, there are any co-formions in the prior art that contain multiple substitutions of calcium and / or lead or divalent and tetravalent cations and are doped with a dispersible, spherical and slight barium titanate with a narrow particle size distribution. I never do that.

Accordingly, it is a primary object of the present invention to provide a dispersible, finely doped barium titanate copolymer with a narrow particle size distribution.

It is another object of the present invention to provide a variety of various BaTiO ₃ based compositions doped with BaTiO ₃ having a primary particle size ranging from 0.05 to 0.4 microns.

Another object of the present invention is to provide a doped barium titanate based composition having isotropic primary particles.

Another object of the present invention is to provide a doped barium titanate based composition that is substantially free of milling media.

It is a further object of the present invention to provide a doped barium titanate based composition wherein all components are intimately mixed on a particle size scale.

The present invention includes a substantially spherical, narrowly sized, intimately blended particle size scale, and a wide variety of disperse doped barium titanate copolymers. One important embodiment of the present invention is a doped barium titanate based composition represented by the following general formula.

_{XBa (1-x ') Ca} x' 0 · YTi (1-y-y'-y ") Sn y Zr y 'Hf y" O 2 · ZD

Wherein X, Y and Z are coefficients, X and Y have a value of 0.9 to 1.1, Z has a value of 0 or more and less than 0.1, and y, y 'and y "are independently 0 to 0.3 Value, but the sum of y + y '+ y "is less than 0.4, x' is greater than or equal to 0 and less than 0.4, and D represents at least one dopant oxide.

Another important embodiment of the present invention is a doped barium titanate chemistry represented by the following general formula.

_{XBa (1-x) Rb x} 0 · YTi (1-y-y'-y ") Sn y Zr y 'Hf y" O 2 · ZD

Wherein X, Y and Z are coefficients, X and Y have a value between 0.9 and 1.1, Z has a value between 0 and less than 0.1, and y, y 'and y "are independently 0 to 0.3 Have a value between and the sum of y + y '+ y "is less than 0.4, x is 0 or more and less than 0.4, and D represents at least one dopant oxide.

Another important embodiment of the present invention is barium titanate copolymer represented by the following general formula.

_{XBa (1-x-x'-} x ') Pb x Ca x' Sr x "0 · YTi (1-y-y'-y") Sn y Zr y 'Hf y "O 2 · ZD

Wherein X, Y and Z are coefficients, X and Y have a value between 0.9 and 1.1, Z has a value of 0 or more and less than 0.1, x, x ', x ", y, y' and y "each independently has a value of 0 or more and less than 0.3, the sum of x + x '+ x" is less than 0.4, the sum of y + y' + y "is less than 0.4, and D is at least one dopant. Oxides.

Each doped barium titanate based copolymer according to the present invention has the same and unique physical properties. The average primary particle size of the doped barium titanate based coform is in the range of 0.05 microns to 0.4 microns. Moreover, the average particle size measured by image analysis is comparable to the average particle size measured by the settling method, which proves that the conformal is dispersible. The doped copolymer particle size distribution curves have a quadrant ratio of 2.0 or less, which demonstrates that the doped barium titanate based copolymer has a fairly narrow particle size distribution. A further important fact is that according to the present invention any barium titanate insulator composition that is dispersible, fine and doped can be prepared by a common single hydrothermal process.

The above and other pertinent and advantages of the present invention will be described with reference to the accompanying drawings.

Suitable embodiments of the invention are doped coforms represented by the following general formula.

_{XBa (1-x-x'-} x ") Pb x Ca x 'Sr x" 0 · YTi (1-y-y'-y ") Sn y Zr y' Hf y" O 2 · ZD

Wherein X, Y and Z are the coefficients of divalent, tetravalent and dopant cations, wherein X and Y have values in the range of 0.9 to 1.1, more preferably 0.95 to 1.05, Z is 0 to 0.1, More preferably, it has a value of 0-0.05, x, x ', x "independently shows the atomic fraction of a divalent cation, It has the range of 0-0.3, More preferably, it is 0-0.2, x + x The sum of '+ x' has a value in the range of 0 to 0.4, more preferably 0 to 0.3, and y, y 'and y "independently represent the particle fraction of tetravalent cations, and 0 to 0.3, more preferably. Below it has a value in the range 0 to 0.25, the sum of y + y '+ y "has a value in the range 0 to 0.4, more preferably 0 to 0.3, and D represents a different dopant oxide of barium titanate Indicates.

Preferably, the fine, dispersible, and fine powder of the present invention consists of a doped barium titanate copolymer that is substituted with 0 to 30 mole percent of both tetravalent and divalent metal ions. Divalent barium ions may be partially substituted by lead, calcium, strontium or mixtures thereof. In addition, tetravalent titanium ions may be partially substituted by tin, zirconium, hafnium or mixtures thereof.

The barium titanate-based compositions include lanthanum, cobalt, manganese, magnesium, scandium, yttrium, antibody, bismuth, zinc, cadmium, aluminum, boron, tungsten, chromium, nickel, molybdenum, iron, niobium, vanadium, tantalum, copper, silicon Small amounts of doped one or more of various dopants, including oxides and mixtures thereof. Although the amount of dopant oxide (s) contained in the coform is 0-10 mol%, more preferably 0-5 mol%, barium titanate based compositions are specifically identified by the morphological properties described above. . Therefore, both single dopants of barium titanate as well as multiple dopant composite copolymers are composed of substantially spherical dispersible particles having a narrow particle size distribution and having a primary particle size in the range of 0.05 to 0.4 microns.

A preferred method of preparing the doped barium titanate based copolymer is to intimately mix the dopant (s) with the tetravalent hydrous oxide (s). Intimate mixing can be accomplished by any of several methods. Dopants may be co-precipitated with tetravalent hydrous oxides. Alternatively, the dopants may be precipitated as high surface area hydrous oxides, washed and subsequently mixed with tetrahydric oxides. Finally, since the dopants can be precipitated in an alkaline medium containing Ba (II), their solutions can be added to the tetrahydric hydrous oxide, preferably as acetate, formate or nitrate or ammonium salt. The slurry of hydrous oxides and dopants is treated hydrothermally with oxides or hydroxides of lead and / or calcium at temperatures up to 200 ° C. The slurry is then cooled to a temperature of 60 to 150 ° C. The barium hydroxide solution partially substituted by barium hydroxide or strontium hydroxide is heated to a temperature of 70 ° C. to 100 ° C. and added to the slurry of insoluble divalent cation, tetravalent hydrous oxide and dopant at a constant rate. The slurry was kept at the addition temperature for 10-30 minutes and then heated at a temperature of 120 ° C.-225 ° C. to allow the reaction of the hydrous oxide with the hydroxide of the soluble divalent cation to occur to the extent required.

The primary particle size and particle size distribution of the coforms prepared by the hydrothermal method are the same whether the doped barium titanate coforms simply contain a single dopant or contain various dopants. This is a multiple dopant composite copolymer, i.e. a predominantly single quadrant ratio of 1.29 indicating that the product has a narrow primary particle size distribution, with a primary particle size of 0.20 microns, 1.02 _{Ba 0.811} Pb _0.105 Ca _0.081 Sr _{0.003 O.Ti 0.832} Sn _0.074 Zr _0.094 O ₂ · can be easily seen from the transmission electron micrograph of _{0.012CoO · 0.009MnO · 0.005Nb 2 O 5} . The multicomponent doped composite barium titanate based copolymer of FIG. 1 and the single dopant barium titanate copolymer, namely 0.998 Ba _0.792 Pb _0.104 Ca _0.098 Sr _0.006 O · Ti _0.831 Sn _0.070 Zr _0.099 O ₂ .0.032CoO of FIG. Comparing the transmission electron micrographs, it can be seen that the shapes of the respective barium titanate based compositions are very similar. This is further illustrated by the results of image analysis showing that the product of FIG. 2 has a primary particle size of 0.18 microns and a quadrant of 1.26.

Various in vitro tests were conducted to evaluate the physical and chemical properties of the doped barium titanate based copolymer according to the present invention. Reagents were all used express or the equivalent. The Ba (OH) ₂ 8H ₂ O product used contained about 1.0 mol% to 0.3 mol% strontium which tends to condense in the product. All Ba (OH) ₂ solutions maintained at 70 ° C. to 90 ° C. were filtered to remove the carbonate present before use. CaCO ₂ was calcined at 800 ° C. to obtain CaO. Compound CaO was contacted with water to obtain Ca (OH) ₂ . Tungsten was introduced into ammonium tungstate solution. An ammonium tungstate solution was prepared by dissolving tungstic acid (WO ₃ H ₂ O) with stirring in a heated 2M ammonia solution. This solution is metastable and was used immediately after preparation.

Hydrous oxides of TiO ₂ , SnO ₂ and Zr ₂ were prepared by neutralizing aqueous solutions of their respective chlorides with aqueous ammonia at room temperature. The product was filtered and washed until a filtrate free of chlorine ions was obtained as measured by AgNO ₃ . Similarly, hydrous Nb (V) oxides were prepared by neutralizing Nb (V) fluoride solutions. Likewise, mixed hydrous oxides of TiO ₂ and SnO ₂ and TiO ₂ and Sb ₂ O ₃ were prepared by neutralizing solutions containing chlorides of Ti (IV), Sn (IV) and Sb (III), respectively. Coprecipitates of hydrous TiO ₂ and SeO ₃ were prepared by neutralizing an aqueous solution containing titanium (IV) chloride and bismuth nitrate (III). The percent solids present in the washed wet cake was measured after calcination at 900 ° C. for 1 hour. Several wet cakes of each product were used for the experiment.

All synthetic experiments were carried out in an autoclave of 2 liters in volume. To prevent contamination, all wet parts of the autoclave were made of titanium metal or coated with Teflon. All synthesis experiments were conducted in the absence of CO ₂ . The filtrate solution of Ba (OH) ₂ , maintained at a temperature of about 80 ° C., was discharged in a autoclave within 10 seconds by a high pressure N ₂ solution of Ba (OH) ₂ contained in a high pressure pump or heated bomb for rapid addition. Introduced in autoclave. The autoclave contents were agitated using a 1 inch diameter turbine type stirrer operating at 1000-1500 RPM during the synthesis process. After synthesis, the resulting slurry was transferred to a compression filter without exposure to atmosphere (to prevent insoluble BaCO ₃ formation), filtered and dried in vacuo at 100 ° C.

Image analysis was used to determine the primary particle size and primary particle size distribution of the product. Primary particle size and primary particle size distribution were measured by measuring the size of 500 to 1000 particles in a number of TEM fields to obtain primary particles having equivalent spherical diameters. Two or more contact particles were visually separated and the size of each primary particle was measured. Equivalent spherical diameters were used to estimate the cumulative mass percent distribution as a function of primary particle size. Average particle size (by weight) was considered as the primary particle size of the sample. The quadrant ratio (QR) defined by the value obtained by dividing the upper quadrant diameter (by weight) by the lower quadrant diameter was taken as a measurement of the distribution width. Monodisperse products have a QR value of 1.0. Products with a QR value in the range of 1.0 to 1.5 are classified as having a narrow particle size distribution, and those having a QR value in the range of 1.5 to about 2.0 are classified as having a moderately narrow particle size distribution, while having a QR value of about 2.0 or more. Were classified as having a broad particle size distribution.

Experience has shown that doped coforms can be classified as having a narrow particle size distribution, a moderately narrow particle size distribution, and a broad particle size distribution by visual evaluation by visual evaluation of the TEM. Based on this experience, visual evaluation was used to classify the particle size distribution of the products of the present invention. Since most of the doped copolymers produced had a narrow particle size distribution, the average primary particle size was determined in the present invention by measuring the size of 20 to 30 particles under a microscope. Both quantitative and semiquantitative particle size measurements showed that the doped barium titanate based copolymers had a primary particle size ranging from 0.05 to 0.4 microns.

Particle size is also calculated from the surface area measured by nitrogen adsorption. In this calculation the density of the product is calculated from the composition of the powder and the literature density of the pure components of the raretite. The amount of dopant in the sample is small and typically dopant does not differ significantly from the density of the important raretite, so the effect of the dopant on the density of the product can be neglected. The error due to this estimate is small.

Exact agreement between particle size as measured by microscope and surface area can only be expected for monodisperse spherical powders. As the distribution is wider, the sphericity decreases and the roughness of the particle surface increases, the difference between the particle sizes measured by the two techniques increases. Thus, in a practical system the particle size measured under the microscope is typically larger than the particle size calculated from the surface area. In the present invention, if the two-digit factor coincides between the two particle size measurements, it is regarded as evidence that the amount of fine size precipitated with the particles is small.

The dispersibility of the product was evaluated by comparing the primary particle size and particle size distribution measured by image analysis with the comparative values measured by sedimentation. The sedimentation method provides a particle Stokes diameter that approximately matches the equivalent spherical diameter measured by image analysis. In the present invention, using a Micromeritics Sedi-graph (Norcros, Georgia, USA) to measure the cumulative mass% distribution, the average Stokes diameter and QR value can be calculated Shown in Stokes diameter.

The powder is dissolved by sonication for 15-30 minutes in isopropanol containing 0.12% by weight of Emphos PS-21A (Witco Organics Divizion, Madison Avenue, 520, New York, USA) as a dispersant prior to sedimentation. I was.

The particle size measured by sedimentation and image analysis depends on different principles. For this reason, the particle sizes measured by the two methods do not always match exactly. In addition, as described above, image analysis separates the visuals of contact particles (some of which may bind together). In the sedimentation method, both the contact particles and the bound particles act as one entity. These entities occur for two reasons: there is a bond that forms a solid aggregate that cannot be easily separated between some of the particles in the primary during sonication and is below the optimum dispersion stability that causes some aggregation. . In the present invention, if the mean weight particle size measured by the image analysis method and the sedimentation method coincides within the 2-digit factor, it is interpreted as one indication that the product is dispersible. In addition, the QR value measured by the sedimentation method is expected to be larger than the QR value by the image analysis method (and in some cases, larger). It is reasonable to assume that the QR value under the optimal dispersion condition will be the value measured by the image analysis method or the value measured by the sedimentation method. A secondary criterion used to measure dispersibility in the present invention was that the QR value of the powder obtained by the sedimentation method was less than 2.0.

Qualitative methods were also used to assess dispersibility. Experience in the present invention indicates that the product can be classified as dispersible if the primary particles in the TEM are mostly present as single particles. Normal assessment of this dispersibility will satisfy the above quantitative criteria for characterizing dispersibility.

Sample uniformity was measured with a scanning transmission electron microscope (STEM) with energy dispersive X-ray analytical power. The composition of several primary particles was measured. If at least 80% of the particles contained all powder components, the product was judged to be uniform as a particle size scale. Indeed, when conducting STEM analysis, this criterion was always met. Moreover, the amounts of the various components were not quantitative, but appeared to be quite comparable (within 80%) from the peak intensity on a particle to particle basis.

The composition of the product was measured after the sample was dissolved by elemental analysis using an inductive pair plasma photometer (IPC). The accuracy for the principal component elements was about ± 2%. The accuracy of the results for the subcomponent elements was below this value. The atomic ratio Ba (II) / Ti (IV) of the sample consisting mainly of BaTiO ₃ was also measured by X-ray fluorescence. This ratio was slightly more accurate than that determined by solution analysis and was used where applicable.

The doped barium titanate copolymer according to the present invention also includes a copolymer in which divalent lead or calcium is partially substituted instead of divalent barium. Doped coforms also include coforms in which divalent barium is partially substituted by a mixture of lead and calcium or a mixture of lead, calcium and strontium. Partial substitution by tin, zirconium and hafnium of tetravalent titanium cations is also included within the scope of the present invention. As shown in our co-pending US patent application number 859,577, despite the substitution of certain divalent or tetravalent cations, the morphological properties of the barium titanate copolymer are the same. As a result, the following non-limiting examples include only more complex barium titanate copolymers, but are also intended to provide representative morphological properties of doped copolymers substituted with lead barium titanate and barium titanate and their tetravalent cations. .

Example 1

A series of coforms containing a single dopant was 0.64 liters of vigorously stirred slurry containing TiO ₂ , 0.167 mol, 0.066 mol Sn, ZrO ₂ , 0.002 mol, 0.022 mol PbO and 0.006 mol dopant salt added with nitrate Was prepared by heating from room temperature to 200 ° C. within about 70 minutes. The slurry was cooled to 120 ° C. and 0.46 liters of about 0.21 mole Ba (OH) ₂ solution was added to the slurry within 3.0 ± 0.2 minutes. The temperature of the resulting slurry was maintained at 120 ° C. for about 30 minutes and then heated to 200 ° C. within about 30 minutes. Slurry samples were filtered, dried and the surface area, chemical and morphological properties were measured.

TABLE 1

The concentrations of dopant and tetrahydric oxides in the filtrate were both below the detection sum of the device (less than 1 × 10 ⁻⁴ mol / liter). Therefore, it can be assumed that these metals are incorporated in the solid phase almost quantitatively. TEM measurements showed that the product particles were substantially spherical and insignificant. The particle size measured from the surface area coincided within the two-digit factor with the particle size measured by the microscope, indicating that the microscopic material had hardly bound the particles. The cobalt doped product was visually assessed by TEMS and the quadrant ratio was 1.26. Visual evaluation of the TEMS of the other products found that they had a similar particle size distribution. The sedimentation method was used to quantitatively assess the dispersibility of the manganese doped product. In this process, the product was found to have a particle size of 0.21 micron and a quadrant ratio of 1.69, which is a good agreement with the particle size obtained from TEMS. From these quantitative data, it was confirmed that this product was dispersible.

Example 2

A composite coforme containing two dopants was prepared by hydrothermal treatment using an amount and source matched to the tetravalent hydrous oxide and alkaline earth metal and Pb (II) cation used in Example 1. Prior to the addition of barium hydroxide, 0.002 moles of each topant was added to the tetrahydric hydrous oxide slurry as nitrate or, in the case of niobium, Nb (OH) wet cake. The solid phase tetravalent and divalent atomic ratios after the hydrothermal treatment process were found to be comparable to those of Example 1, but not described in this example.

TABLE 2

Filtration resulted in about 50-60% of Al (III) in the solution, so that the molar ratio of the dopant oxide rally titaniumite of the chromium-cobalt-aluminum doped coforme, ie the value of the coefficient Z, was determined by cobalt-niobium-manganese dough It was smaller than the value for the pinged conform. All products were substantially spherical, dispersible and had a narrow particle size distribution. Image analysis demonstrated that the cobalt-niobium-manganese doped co-formium had a primary particle size of 0.20 microns and a quadrant ratio of 1.29. Based on the study by the sedimentation method, the product was found to have a particle size of 0.26 microns and a quadrant ratio of 1.67. From these quantitative measurements, a normal assessment could be confirmed that the product is dispersible and has a narrow particle size distribution. Another indication of dispersibility is the agreement within the two-digit factor between the particle size measured by the microscope and the particle size calculated from the surface area. Cobalt-niobium-manganese-doped composite barium titanate copolymer was subjected to STEM analysis. As a result of the analysis, all particles were found to contain almost equivalent amounts of barium, lead, calcium, strontium, titanium, zirconium, tin, manganese, cobalt and niobium. The STEM results demonstrate that multiple doped composite copolymers of barium titanate are uniform at the particle size scale.

Claims (18)

A doped barium titanate-based copolymer, characterized in that it consists of substantially spherical particles represented by the general formula below, wherein the average primary particle size of the doped copolymer is in the range 0.05 to 0.4 microns. _{XBa (1-x) Rb x} 0 · YTi (1-y-y'-y ") Sn y Zr y 'Hf y" O 2 · ZD In the above formula, X and Y have a value of 0.9 to 1.1, Z has a value of 0 or more and less than 0.1, y, y 'and y "independently have a value ranging from 0 to 0.3, y + y' The sum of + y "is less than 0.4, x 'is 0 or more and less than 1.4, and D is at least one dopant oxide. The method of claim 1, wherein at least one dopant oxide D is selected from lanthanum, cobalt, manganese, magnesium, scandium, yttrium, antibody, bismuth, zinc, cadmium, aluminum, boron, tungsten, chromium, nickel, molybdenum, iron Doped copolymer of barium titanate, characterized in that from the group consisting of niobium, vanadium, tantalum, copper, silicon oxides and mixtures thereof. 2. The doped conformation of barium titanate according to claim 1, wherein the primary particle size measured by image analysis and sedimentation is consistent within a two-digit factor. The titanic acid according to claim 1, wherein the doped copolymer has a narrow particle size distribution as measured by image analysis, and the first particle size distribution curve of the doped copolymer has a quadrant ratio of 2.0 or less. Doped coform of barium. 2. The doped copolymer of barium titanate according to claim 1, wherein the X / Y ratio is 1.000 ± 0.015. 2. The doped copolymer of barium titanate according to claim 1, wherein the X / Y ratio is in the range of 0.95 to 1.1. A doped barium titanate-based copolymer, characterized in that it consists of substantially spherical particles represented by the general formula below, wherein the average primary particle size of the doped copolymer is in the range 0.05 to 0.4 microns. _{XBa (1-x) Rb x} 0 · YTi (1-y-y'-y ") Sn y Zr y 'Hf y" O 2 · ZD In the above formula, X and Y have a value of 0.9 to 1.1, Z has a value of 0 or more and less than 0.1, y, y 'and y "independently have a value ranging from 0 to 0.3, y + y' The sum of + y "is less than 0.4, x is 0 or more and less than 1.4, and D is at least one dopant oxide. The method of claim 7, wherein at least one dopant oxide D is selected from the group consisting of lanthanum, cobalt, manganese, magnesium, scandium, yttrium, antibody, bismuth, zinc, cadmium, aluminum, boron, tungsten, chromium, nickel, molybdenum, iron Dopant of barium titanate, characterized in that it is selected from the group consisting of niobium, vanadium, tantalum, copper, silicon oxides and mixtures thereof. 8. The doped copolymer of barium titanate according to claim 7, wherein the primary particle size measured by image analysis and sedimentation is consistent within a two-digit factor. 8. The titanic acid according to claim 7, wherein the doped copolymer has a narrow particle size distribution as measured by image analysis and the first particle size distribution curve of the doped copolymer has a quadrant ratio of 2.0 or less. Doped coform of barium. 8. The doped copolymer of barium titanate according to claim 7, wherein the X / Y ratio is 1.000 ± 0.015. 8. The doped conformation of barium titanate according to claim 7, wherein the X / Y ratio is in the range of 0.95 to 1.1. A barium titanate-based copolymer, characterized in that it consists of substantially spherical particles represented by the following general formula, wherein the average primary particle size of the doped copolymer is in the range of 0.05 to 0.4 microns. _{XBa (1-x-x'-} x ") Pb x Ca x 'Sr x" 0 · YTi (1-y-y'-y ") Sn y Zr y' Hf y" O 2 · ZD In the above formula, X and Y have a value of 0.9 to 1.1, Z has a value of 0 or more and less than 0.1, and x, x ', x ", y, y' and y" are independently 0 or more and less than 0.3. Have a value, and the sum of x + x '+ x "is less than 0.4, the sum of y + y" + y "is less than 0.4, and D is at least one dopant oxide. The method of claim 13, wherein at least one dopant oxide D is selected from lanthanum, cobalt, manganese, magnesium, scandium, yttrium, antibody, bismuth, zinc, cadmium, aluminum, boron, tungsten, chromium, nickel, molybdenum, iron Dopant of barium titanate, characterized in that it is selected from the group consisting of niobium, vanadium, tantalum, copper, silicon oxides and mixtures thereof. 14. The doped copolymer of barium titanate according to claim 13, characterized in that the primary particle sizes measured by image analysis and sedimentation methods coincide within the two-digit factor. 14. The titanic acid according to claim 13, wherein the doped copolymer has a narrow particle size distribution as measured by image analysis, and the first particle size distribution curve of the doped copolymer has a quadrant ratio of 1.5 or less. Doped coform of barium. 14. The doped copolymer of barium titanate according to claim 13, wherein the X / Y ratio is 1.000 ± 0.015. 15. The doped conformation of barium titanate according to claim 13, wherein the X / Y ratio is in the range of 0.95 to 1.1.

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