JP4859640B2 - Barium titanate powder and method for producing the same, and dielectric ceramic - Google Patents

Description

  The present invention relates to a barium titanate powder, a method for producing the same, and a dielectric ceramic, and more particularly, a barium titanate powder having an average particle size of 100 nm or less, a method for producing the same, and a dielectric formed using the barium titanate powder. Related to porcelain.

  In recent years, ceramic electronic components have been rapidly reduced in size and performance in order to cope with downsizing of electronic devices. The same applies to the multilayer ceramic capacitor, and the dielectric layer has been made thinner and higher in number as the dielectric material has higher performance. As an approach to these goals, various elemental technologies such as blending, forming and firing of raw material powders constituting the dielectric layer have been developed.

  By the way, a multilayer ceramic capacitor has a structure in which dielectric layers and internal electrode layers are alternately laminated. The dielectric layer is usually composed of a main raw material powder such as barium titanate as a main component, and the main raw material. It consists of a sintered body of mixed powder to which various auxiliary raw material powders such as oxides of rare earth elements for controlling the dielectric properties of the powder are added.

  For this reason, in order to cope with the thinning of the dielectric layer, the barium titanate powder is atomized (see, for example, Patent Documents 1 and 2).

  For example, in Patent Document 1, barium titanate powder having an average particle size of 0.2 μm or less is obtained by a method of hydrolyzing these aqueous solutions using barium hydroxide as the barium source and titanium alkoxide as the titanium source. A method is disclosed.

Further, according to the cited document 2, in a heated alcohol or glycol ether, a titanium alkoxide as a raw material is reacted with a hydrate of barium hydroxide to thereby form an extremely fine barium titanate having an average particle size of less than 10 nm. A method for obtaining a powder is disclosed.
JP 2000-281338 A JP 2004-131364 A

  However, even if an attempt is made to obtain a barium titanate powder having an average particle size of 100 nm or less on the basis of the production methods disclosed in Patent Documents 1 and 2, the obtained barium titanate powder has a crystal structure mainly composed of cubic crystals. Therefore, there is a problem that a high dielectric constant barium titanate powder cannot be obtained.

  In addition, the method for producing the barium titanate powder disclosed in Patent Documents 1 and 2 requires that the prepared barium titanate powder is temporarily calcined at a temperature of 850 to 1000 ° C. The barium titanate powder thus obtained has a problem that the average particle size becomes large and the variation in particle size becomes large.

  Accordingly, an object of the present invention is to provide a barium titanate powder having a crystal structure mainly composed of tetragonal crystals, a method for producing the same, and a dielectric ceramic.

The barium titanate powder of the present invention has a purity of 99% or more, an average particle size of 35 to 100 nm, and the variation coefficient when the variation coefficient of the particle diameter is expressed as standard deviation / average particle diameter × 100 (%). Is 40% or less, and when the diffraction intensity of the (200) plane in the X-ray diffraction pattern of barium titanate is 100, the diffraction intensity of the (002) plane in the X-ray diffraction pattern of barium titanate is 30. more der is, characterized der Rukoto elevation angle 38 ° or more toward the lower angle side with respect to the base line of the diffraction peak of the (002) plane.

  Moreover, in the said barium titanate powder, it is desirable that an average particle diameter is 35-48 nm.

Next, the method for producing the barium titanate powder of the present invention includes a step of applying ultrasonic waves to a solution containing barium having a purity of 99% or more and titanium having a purity of 99% or more to make the solution into a mist, Introducing the solution into a high-temperature atmosphere to prepare a barium titanate powder precursor, and instantaneously at a temperature of 900 to 1200 ° C. with the barium titanate powder precursor dispersed in a gas. and having a heating process of heating the Ru melted, and a cooling step of Ru solidified by cooling in an instant.

Further, in the method for producing the barium titanate powder, in the heating step, the composite particle is a space having a temperature gradient that changes in a direction in which the temperature rises and a maximum temperature set to 1000 ° C. or higher. with passing as the ambient temperature changes at 1000 ° C. / sec or more, the a cooling step, wherein the composite particles, the temperature from the maximum temperature is set to more than 1000 ° C. space is changed in the direction to decrease a space having a temperature gradient, the temperature of the periphery of the composite particles Ru passed to vary at 1000 ° C. / sec or higher. Further, as a film component, using an oxide powder of a rare earth element, as the coating component, the average particle diameter is preferably used particles: 10 to 20 nm.

  Next, the dielectric ceramic of the present invention is obtained by molding and firing the barium titanate powder.

  As described above, the barium titanate powder of the present invention is a barium titanate powder having high purity, fine particles, small variation in particle size, and high tetragonal crystallinity in the X-ray diffraction pattern. According to such a barium titanate powder, a high dielectric constant can be obtained even with fine particles having an average particle size of 100 nm or less.

  Further, in the method for producing barium titanate powder of the present invention, ultrasonic waves are applied to a solution containing barium and titanium to form a mist, and the mist is introduced into a high temperature atmosphere to prepare a precursor of barium titanate powder. Since it is a manufacturing method, the particle | grain size of the barium titanate powder obtained becomes micro size so that it floats in air | atmosphere, and it can obtain a fine barium titanate powder easily.

Next, in the production method of the present invention, the precursor of the barium titanate powder obtained in a fine particle state is instantaneously heated (melted) and cooled (solidified ) while being dispersed in a gas, and then passed. Since the heating is performed, the heated barium titanate powder has high crystallinity, and even if it is a fine particle, it becomes highly tetragonal.

Moreover, since the production method of the present invention is a step of instantaneously heating (melting) and cooling (solidifying ) in a dispersed state in the gas, the barium titanate powders are not heated in a solid state. Therefore, grain growth is suppressed and atomization is facilitated.

  Since the barium titanate powder obtained by such a manufacturing method has a high tetragonal nature of the particles, it is possible to easily obtain a dielectric ceramic having a high dielectric constant, and a high-capacity and high-insulation multilayer ceramic. It is suitable for a capacitor.

  The barium titanate powder of the present invention is characterized by having a purity of 99% or more, and particularly preferably has a purity of 99.1% or more. The purity here is the content when barium and titanium are expressed as oxides.

  If the purity of the barium titanate powder is 99% or more, the amount of impurities is small and the amount of solid solution in barium titanate is reduced, so that the cubic crystallization of the perovskite crystal structure is suppressed and the tetragonal crystal is maintained. There is an advantage that it is easy.

  On the other hand, when the purity is lower than 99%, the tetragonality of the barium titanate powder is lowered.

  Next, the barium titanate powder of the present invention has an average particle size of 35 to 100 nm, and when the variation coefficient of the particle size is expressed as standard deviation / average particle size, the variation coefficient of the particle size is 40% or less. It is characterized by being.

  When the barium titanate powder has an average particle size of 35 nm or more, the proportion of the core portion increases when the barium titanate powder has a core-shell structure, and the proportion of tetragonal crystals increases. It becomes possible to obtain a relative dielectric constant.

  On the other hand, when the average particle size is 100 nm or less, for example, the dielectric layer of the multilayer ceramic capacitor is suitable for thinning, and since many grain boundaries can be formed in the thickness direction in the dielectric layer, high insulating properties are achieved. It becomes.

  On the other hand, when the average particle diameter of the barium titanate powder is smaller than 35 nm, it is difficult to obtain a high dielectric constant because the ratio of tetragonal crystals contained in the barium titanate powder is small.

  In addition, when the barium titanate powder has an average particle size larger than 100 nm, it is difficult to reduce the thickness of the dielectric layer when this barium titanate powder is used in a multilayer ceramic capacitor. The number of crystal grains in the thickness direction is reduced, and therefore the number of grain boundaries per dielectric layer is reduced, so that the insulating property is lowered.

  In addition, it is desirable that the average particle diameter of the crystal particles in the sintered body produced using the barium titanate powder of the present invention is 20 to 60 nm, particularly 35 to 48 μm.

  Further, the barium titanate powder of the present invention is a powder having a variation coefficient (standard deviation / average particle diameter × 100 (%)) of the particle diameter of the powder of 40% or less and small particle diameter variation. When the variation coefficient of the particle size of the barium titanate powder is 40% or less, the variation coefficient of the particle size of the crystal particles in the sintered dielectric layer can be reduced to 61% or less. When applied, the characteristics can be easily stabilized.

  FIG. 1 is a schematic diagram of an X-ray diffraction pattern of the barium titanate powder of the present invention. FIG. 1 is an X-ray diffraction pattern at 2θ = 44 to 46 °. The peak near 2θ = 44.9 ° is the (002) plane peak in the X-ray diffraction pattern of barium titanate, and the peak near 45.4 ° is the (200) peak.

  The barium titanate powder of the present invention is characterized in that when the (200) plane of the X-ray diffraction pattern of barium titanate is 100, the (002) plane in the X-ray diffraction pattern is 30% or more.

  That is, in the barium titanate powder of the present invention, as is clear from FIG. 1, the peak in the X-ray diffraction pattern is separated into two peaks of (200) plane and (002) plane, and as described above. When the peak of the (200) plane of the X-ray diffraction pattern is 100, the peak intensity of the (002) plane in the X-ray diffraction pattern is 30% or more. Even if it exists, it has a high tetragonality. In this case, the diffraction intensity (002) in the X-ray diffraction pattern is more preferably 50% or more, where the diffraction intensity of the (200) plane in the X-ray diffraction pattern is 100.

  On the other hand, when the diffraction intensity of the (002) plane in the X-ray diffraction pattern is less than 30% when the diffraction intensity of the (200) plane in the X-ray diffraction pattern is 100, the tetragonal nature is low. A high dielectric constant cannot be obtained. The index plane diffraction intensity in the X-ray diffraction pattern is expressed as a ratio of the height in the vertical direction from the base line to each peak top.

Further, the barium titanate powder of the present invention, elevation toward lower angle side with respect to the base line of the peak of the X-ray diffraction pattern (002) plane is an average particle diameter of the barium titanate powder If it is 3 8 ° or more Even if it is 60 nm or less, there is an advantage that the dielectric constant of the sintered dielectric ceramic can be 1500 or more.

  The barium titanate powder of the present invention preferably has an atomic ratio (Ba / Ti) of barium to titanium in the range of 0.997 to 1.005. When (Ba / Ti) is in the range of 0.997 to 1.005, there is an advantage that homogeneous dielectric particles having a perovskite structure showing tetragonal crystals can be formed.

  Next, a method for producing the dielectric material powder of the present invention will be described. FIG. 2 is a schematic view of an apparatus for preparing a precursor of barium titanate powder of the present invention. First, a solution containing barium and titanium is prepared.

  As the barium source, any one of barium acetate, barium nitrate, and barium chloride is preferable in that it has high solubility in water, a mixed solvent of water and an organic solvent, and particularly, heating. Barium acetate is more desirable because there is no generation of toxic gases during decomposition.

  On the other hand, as the titanium source, titanium tetrachloride or an alkoxide of titanium can be suitably used because it is highly soluble in water or a mixed solvent of water and an organic solvent.

In this case, the raw material to be used is desirably 99% or more from the viewpoint of purifying the obtained barium titanate powder.

  The concentrations of barium and titanium in the solution are appropriately adjusted according to the size of the barium titanate powder to be obtained. These concentrations are preferably 0.1 mol / L or less because the solution concentration is lowered to achieve atomization. If the solution concentration is thinner than 0.01 mol / L, the precursor 5 may be thinned and it may be difficult to obtain a solid sphere.

  Next, while applying ultrasonic vibration to the solution containing barium and titanium, a carrier gas is sent to the solution to make the solution containing barium and titanium mist.

  The output of the ultrasonic wave is appropriately adjusted according to the size and quantity of the mist to be obtained.

  Next, the atomized solution is introduced into a high-temperature atmosphere that is an atmosphere formed by a burner or the like to prepare a precursor of barium titanate powder. In this case, the introduction tube between the container containing the mist and the high-temperature atmosphere generator is depressurized to create an air flow from the container to the high-temperature atmosphere generator, and the mist-like solution is heated to a high temperature. Reach the atmosphere generator.

  And the solvent of the mist-like solution which reached | attained in the high temperature atmosphere of a high temperature atmosphere generator instantaneously evaporates, and changes to the precursor containing a metal oxide. The precursor containing the metal oxide thus obtained becomes a precursor of barium titanate powder (hereinafter referred to as precursor).

Then introduced precursor, a heating process of Ru melted by heating instantaneously, in a heating furnace which can make a cooling step of Ru solidified by cooling in an instant.

  FIG. 3 is a schematic sectional view of a heating furnace for producing the barium titanate powder of the present invention. The heating furnace to be used is provided with a raw material charging feeder 13 at the upper part of the furnace main body 11, while a powder recovery part 15 is provided at the lower part of the furnace main body 11. A suction device 21 for producing (laminar flow) is provided. The furnace body 11 is provided with a heating unit 19 around the furnace core tube 17.

In the heating furnace, a gas flow including the precursor 5 that is the powder to be heated is formed by the gas sucked in the direction of the path (arrow) from the raw material charging feeder 13 through the furnace body 11 to the powder recovery unit 15. Is done. Further, the furnace body 11 is provided with a space 23 in a temperature region where the flow of the gas containing the precursor 5 is set to a high temperature at the center of the length direction of the furnace core tube 17. The precursor 5 is instantaneously heated, melted and reacted, and the heated precursor is cooled immediately and solidified by cooling.

  And the heating process in this invention sets temperature to 900-1200 degreeC, It is characterized by the above-mentioned. When the temperature is 900 ° C. or higher, there is an advantage that high-purity barium titanate powder can be obtained by increasing the decomposition of the precursor of barium titanate.

  On the other hand, when the temperature of the heating step is 1200 ° C. or lower, there is an advantage that the barium titanate powder having a small average particle diameter can be obtained by suppressing the grain growth of the synthesized barium titanate powder.

  On the other hand, when the temperature of the heating step is lower than 900 ° C., the purity of the obtained barium titanate powder is lowered, and only barium titanate powder having a low tetragonality can be obtained.

  On the other hand, when the temperature of the heating step is higher than 1200 ° C., the particle size of the synthesized barium titanate powder may be increased.

The temperature around the precursor 5 of the barium titanate powder 5 is 1000 ° C./sec or more in the space 23 in which the temperature of the precursor 5 changes in the direction of increasing temperature and the maximum temperature is set to 1000 ° C. or higher. in Ru passed to vary.

In addition, the cooling step subsequent to the heating step described above is performed on a space 24 having a temperature gradient in which the precursor 5 changes in a direction in which the temperature decreases from the space 23 where the maximum temperature is set to 1000 ° C. or higher. temperature around the precursor 5 Ru passed to vary at 1000 ° C. / sec or higher.

  In this invention, 1100 degreeC or more and 1250 degrees C or less are especially preferable at the point of making the dispersion | variation (CV) of the average particle diameter of barium titanate powder small. When the maximum temperature of the heating furnace is 1000 ° C. or higher, there is an advantage that the crystallinity of the barium titanate powder is increased and the ratio of tetragonality is increased. Moreover, the instantaneous heating and cooling as described above can suppress the amorphization of the surface of the barium titanate powder, thereby increasing the tetragonality.

  The conditions of the heating process and the cooling process described above are between the flow rate of the gas containing the precursor of the barium titanate powder, the temperature of the upper and lower ends of the core tube 11 in the heating furnace, and the position indicating the maximum temperature of the core tube 11. It is calculated from the distance.

  That is, it passes between the upper end portion of the core tube 17 of the heating furnace and the maximum temperature at the central position in the length direction, and between the maximum temperature at the position near the central portion and the lower end portion of the core tube 17. Estimated from the velocity of the heated gas.

  In the manufacturing method of the present invention, since a laminar flow is formed by suction from the lower end side of the core tube 17 of the heating furnace, the upper end side and the lower end side are separated from the core tube 17 as barium titanate powder. The ambient temperature change through which the precursor 5 is passed is almost the same.

  Furthermore, in order to suppress the aggregation of the heated precursor 5 and reduce the coefficient of variation of the particle diameter of the obtained barium titanate powder, the present invention can be set to an environment having the following temperature changes. desirable.

That is, in the present invention, in the heating step in which the barium oxide and titanium oxide constituting the precursor 5 are instantaneously heated and melted, the ambient temperature change through which the precursor 5 passes is 1000 ° C./sec or more. In particular, 1100 ° C./sec or more is preferable.

Also in the cooling step of solidifying the precursor 5 after the heating step instantaneously, as in the heating step, the ambient temperature change passing the precursor 5 is at 1000 ° C. / sec or more, in particular, 1100 C / sec or more is preferable. If the ambient temperature change through which the precursor 5 passes is 1100 ° C./sec or more, there is an advantage that the barium titanate powder is easily crystallized.

  On the other hand, in the heating step and the cooling step, the amorphous state of the barium titanate powder can be suppressed when the condition (temperature change) for allowing the precursor 5 to pass is 2600 ° C./sec or less.

  In the present invention, since air is sucked from the lower end side of the core tube 17, the conditions (temperature change) for allowing the precursor of the barium titanate powder to pass in the heating step and the cooling step are the same.

  On the other hand, when the barium titanate powder is heated and cooled without performing a suction operation like natural fall, the barium titanate powder aggregates during the fall in the core tube 11 of the heating furnace and is coarse. Particles are formed.

  In the heating step and the cooling step, the condition (temperature gradient) for allowing the precursor 5 to pass can be set as described above, and the core tube 17 is improved in that the crystallinity of the barium titanate powder is increased as in the present invention. Is preferably 3 m or longer, particularly preferably 4 m or longer.

  In addition, it cannot be overemphasized that the manufacturing method of this invention can be applied as a method of forming ceramic powder of metal oxides and composite oxides other than barium titanate powder, for example, lead titanium zirconate, alumina, zirconia, cordierite. It can also be applied to ceramic powders such as mullite and spinel, and various glass powders.

  In the production method of the present invention, a precursor 5 of barium titanate powder (for example, oxalate or coprecipitation method), which is a conventionally known production method, is calcined in a ceramic container using a firing furnace. Compared with the method, since the precursor 5 is heated in a state of being dispersed in the gas, there is little aggregation, and therefore a fine powder can be easily obtained.

  That is, in the method of calcining the precursor of the conventional barium titanate powder obtained from the oxalate or coprecipitation method in a ceramic container using a firing furnace, the powder itself is aggregated or heated. Due to the diffusion of the time, grain growth of the barium titanate powder is likely to occur, and a fine grained and highly crystalline barium titanate powder cannot be obtained.

  Further, in the calcining method in which the treatment is performed at a maximum temperature lower than 1000 ° C., in particular, a temperature of about 500 ° C., for example, compared with the production method of the present invention, the decomposition reaction of the barium titanate precursor And the crystallinity of the barium titanate powder cannot be increased.

  Next, a dielectric ceramic obtained by using the barium titanate powder of the present invention and a multilayer ceramic capacitor formed by the dielectric ceramic will be described.

  A dielectric ceramic obtained using the barium titanate powder of the present invention is obtained by molding and firing the barium titanate powder. In the multilayer ceramic capacitor of the present invention, a dielectric layer and an electrode layer are laminated, and this dielectric layer is a sintered body of the barium titanate-based powder of the present invention. This multilayer ceramic capacitor can be manufactured, for example, as follows.

First, a slurry is prepared by mixing the barium titanate powder of the present invention together with various metal oxide powders such as Mg, rare earth elements and Mn, and a glass component as a sintering aid with a resin and, if necessary, a solvent. As the sintering aid, for example, SiO ₂ —CaO—B ₂ O ₃ based glass is suitable. As the resin, polyvinyl butyral, polyvinyl alcohol, or the like can be used. As the solvent, for example, water, alcohol, butyl acetate, ethyl acetate, or the like can be used.

  Subsequently, the slurry is formed into a sheet shape to produce a dielectric green sheet. Although a shaping | molding method is not specifically limited, For example, a doctor blade method etc. are employable. Next, a dielectric green sheet and an electrode pattern are laminated to obtain a laminate. As the electrode pattern, for example, a conductive paste obtained by mixing a resin and a solvent with a base metal powder such as copper, nickel, or cobalt can be used. The number of laminated dielectric green sheets and electrode patterns is not particularly limited, and can be set as appropriate according to the desired capacitance.

  Next, after removing the binder as necessary, this laminated body is fired, and further, external electrodes and the like are appropriately formed on the fired laminated body to obtain a multilayer ceramic capacitor.

The firing temperature can be appropriately set according to the type and amount of the sintering aid and the particle diameter of the dielectric raw material powder to be used, and is, for example, 1100 to 1300 ° C, preferably 1100 to 1250 ° C. The firing atmosphere is preferably a non-oxidizing atmosphere in order to suppress oxidation of the electrode layer.

  First, a mixed solution of barium and titanium shown in Table 1 was prepared. All the raw materials used had a purity of 99.2%. Next, a precursor of barium titanate powder was prepared from this mixed solution using the high-temperature atmosphere generator shown in FIG.

  Next, using the heating furnace of FIG. 2, heat treatment was performed under the conditions shown in Table 1 (temperature, suction force (laminar flow), temperature increase rate) to prepare barium titanate powder. The temperature was the temperature in the furnace at the center in the length direction of the heating furnace. The rate of temperature increase was determined as follows. That is, the laminar flow prepared in the method for producing barium titanate powder of the present invention was prepared by discharging the atmosphere using a suction pump. In this case, the diameter of the core tube was 75 mm, the length was 5 m, the central portion in the length direction was the region of the highest temperature, and the upper end of the core tube was 50 ° C. The ambient temperature change through which the composite particles pass was determined from the time of the airflow reaching the position of 2.5 m from the upper end position of the core tube to the center. When the maximum temperature near the center of the core tube is 1250 ° C., the temperature difference is 1200 ° C., and the drop rate is 2 seconds per 5 m when the suction amount is 10 L / min. The ambient temperature change through which the powder precursor passes is 1200/1 = 1200 ° C./sec. In this case, since the air is sucked from the lower end side of the core tube, the ambient temperature change in which the barium titanate powder precursor is passed in the heating step and the cooling step is the same. When the maximum temperature of the core tube is less than 800 ° C., the dropping speed of the composite particles in the laminar flow is 3 seconds, and when it is 800 ° C. or more, it is 2 seconds. In addition, when it was allowed to fall naturally without suction, the arrival time from the upper end of the 5 m high core tube to the recovery part was 10 seconds. In this case, the composite particles agglomerated and sintered to have a diameter of 10 μm. Aggregates of the above size were obtained.

  Next, the obtained barium titanate powder was washed with ion exchange water. Next, the average particle diameter and the coefficient of variation of the particle diameter (standard deviation / average particle diameter × 100 (%)) were determined for the washed barium titanate powder. Further, the crystal structure of the barium titanate powder was evaluated by X-ray diffraction.

  Moreover, the pellet-shaped molded object of diameter 12mm and thickness 1mm was produced using the barium titanate powder, and it baked on conditions of 1100 degreeC and 2 hours. Next, the average particle diameter of the crystal particles and the coefficient of variation of the particle diameter were measured for each sample of the obtained sintered body. In addition, In—Ga metal was applied to both main surfaces of the sintered body sample, the capacitance was measured, and the relative dielectric constant was determined from the thickness and surface area of the sample. The number of samples was 10 each.

  The average particle size and the coefficient of variation of the particle size of the barium titanate powder were photographed with a scanning electron microscope, and the outline of the barium titanate powder projected in this photograph was image-processed. The diameters of the particles were determined as circles, averaged, and the coefficient of variation in particle size was determined.

  Moreover, after polishing the fracture surface of the obtained sintered body, the average particle size of the crystal particles in the sintered body and the coefficient of variation of the particle size were taken, and this was also taken using a scanning electron microscope, Next, image processing was performed on the contours of the crystal grains shown in these photographs, and the diameters of each grain were determined as a circle, averaged, and the coefficient of variation of the grain size was determined. In this case, since the cross section of the crystal particles in the sintered body is often not the cross section at the maximum diameter, it may be smaller than the average particle diameter of the dielectric particles as the raw material powder.

  The diffraction intensity of each index plane in the X-ray diffraction pattern was expressed as the ratio of the height in the vertical direction from the baseline to each peak top. The angle of the X-ray diffraction pattern with respect to the base line was obtained by measuring the angle θ shown in FIG.

The purity of the obtained barium titanate powder was obtained by quantitative analysis of Ba and Ti by ICP analysis. In this case, a 1000 ppm standard solution of Ba and Ti was used for quantitative analysis.

  As is clear from the results in Tables 1 and 2, the sample produced by the production method of the present invention had high tetragonality and a purity of 99% or more even when the average particle size was 35 to 100 nm.

  In particular, the solution concentrations of barium and titanium are both equimolar, the concentration range is 0.01 to 0.08 mol%, the temperature of the heating step is 1000 to 1150 ° C., and the temperature gradient is 1000 to 1050 ° C. / sample No. 12-14, the average particle size of the obtained barium titanate powder is 35-48 nm, and the (002) / (200) ratio of X-ray diffraction showing tetragonality is 32-38%. A dielectric ceramic produced using barium powder has an average particle size of 70 to 88 nm and a dielectric constant of 1510 to 1590, and exhibits excellent dielectric properties.

  On the other hand, Sample No. with a heating process temperature condition of 700 ° C. and a temperature gradient of 500 ° C./sec. In No. 1, 99% or more of barium titanate powder was not obtained.

It is a schematic diagram of the X-ray diffraction peak of the barium titanate powder of the present invention. It is a schematic diagram of the apparatus for preparing the precursor of the barium titanate powder of this invention. It is a cross-sectional schematic diagram of the heating furnace for producing the barium titanate powder of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Furnace main body 13 Raw material input feeder 15 Powder recovery part 17 Furnace core tube 19 Heating part 23 Space

Claims (4)

When the purity is 99% or more, the average particle size is 35 to 100 nm, and the variation coefficient of the particle size is expressed as standard deviation / average particle size × 100 (%), the variation coefficient is 40% or less, and titanium the diffraction intensity of the (200) plane in X-ray diffraction pattern of barium is taken as 100, the diffraction intensity of the (002) plane in X-ray diffraction pattern of the barium titanate Ri der 30 above, (002) plane barium titanate powder, characterized in der Rukoto elevation angle 38 ° or more toward the lower angle side with respect to the base line of the peak of.   The barium titanate powder according to claim 1, having an average particle size of 35 to 48 nm. Applying ultrasonic waves to a solution containing barium having a purity of 99% or more and titanium having a purity of 99% or more to make the solution atomized, and introducing the atomized solution into a high-temperature atmosphere, titanic acid preparing a precursor of barium powder, a heating step of heating instantaneously Ru melted at a temperature of 900 to 1200 ° C. in a state in which the precursor of powdered barium titanate dispersed in a gas, cooled instantaneously possess a Ru cooling step to solidify Te, as the heating step, the precursor of the barium titanate powder, the space temperature having a temperature gradient that varies in the direction is set to more than 1000 ° C. increase in temperature And the ambient temperature of the barium titanate powder precursor is changed so as to change at 1000 ° C./sec or more. A space having a temperature gradient that varies in the direction in which the temperature is lowered from the set space 1000 ° C. or higher, the temperature around the precursor of the barium titanate powder Ru passed to vary at 1000 ° C. / sec or higher A process for producing barium titanate powder characterized by the above.   A dielectric porcelain obtained by molding and firing the barium titanate powder according to claim 1 or 2.

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