Barium titanate particle dispersion and production method thereof

Abstract

To provide a BTO particle which has high thermal stability and a small crystallite diameter.SOLUTION: A barium titanate particle dispersion having a perovskite structure according to the present invention includes barium titanate particles having the perovskite structure and a solvent. The barium titanate particles have a crystallite diameter of 25 nm or less. A part of titanium present at B sites in the perovskite structure is replaced with a metal element other than titanium.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a dispersion of barium titanate particles and a method for producing the same.

[0002] Barium titanate (BTO) with a perovskite structure has a high dielectric constant, so BTO particles are used in the dielectric layers of multilayer ceramic capacitors (MLCCs). Electrode layers primarily composed of metallic Ni particles are alternately stacked with dielectric layers primarily composed of BTO particles to form MLCCs. During the firing process in MLCC production, the greater the difference between the temperature at which sintering of the metallic Ni particles in the electrode layers begins (hereinafter, the temperature at which sintering begins is referred to as the sintering start temperature) and the sintering start temperature of the BTO particles in the dielectric layers, the more likely cracks will occur in the MLCC. To reduce the difference in sintering start temperatures, a small amount of BTO particles is added to the electrode layers as a co-material.

[0003] As MLCCs become smaller, the Ni particles used in the electrode layers are also becoming smaller. Therefore, the particle size of the BTO particles used as a co-material must also be small. Particles with small particle sizes also have small crystallite sizes. A known method for producing small BTO particles (crystallite size of 25 nm or less) is to add titanium alkoxide to a mixed solution of barium hydroxide (hydroxide of an alkaline earth metal) and alkyl cellosolve, and then hydrolyze the titanium alkoxide (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-240904 Summary of the Invention [Problem to be solved by the invention]

[0005] The use of BTO particles with small crystallite diameters, as disclosed in Patent Document 1, allows for the miniaturization of MLCCs. However, the smaller the crystallites, the lower the thermal stability. Therefore, the BTO particles bond together during the firing process in MLCC manufacturing, reducing their effectiveness as a co-material. In other words, the difference in sintering start temperature increases, causing cracks to form in the MLCC.

[0006] Therefore, an object of the present invention is to provide BTO particles having high thermal stability and a small crystallite size. [Means for solving the problem]

[0007] The present inventors have realized BTO particles with good thermal stability by substituting a portion of the titanium (Ti) present in the B site of the perovskite structure with a metal element other than titanium. That is, a dispersion of barium titanate particles with a perovskite structure according to the present invention contains barium titanate particles with a perovskite structure and a solvent, in which the barium titanate particles have a crystallite diameter of 25 nm or less and in which a portion of the titanium present in the B site of the perovskite structure has been substituted with a metal element other than titanium.

[0008] In addition, the method for producing a dispersion of barium titanate particles of the present invention comprises, in order, a first step of preparing an alkyl cellosolve solution of barium hydroxide; a second step of dehydrating the alkyl cellosolve solution at 40°C or higher; a third step of adding titanium alkoxide to the alkyl cellosolve solution; a fourth step of adding a solvent containing water to the alkyl cellosolve solution containing a compound of a metal element (excluding titanium and barium); and a fifth step of aging the alkyl cellosolve solution at 20°C or higher for 6 hours or more. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention relates to a dispersion containing barium titanate (BTO) particles with a perovskite structure. The BTO particles dispersed in a solvent have a small crystallite diameter (25 nm or less). Because small crystallites have low thermal stability, they tend to bond together during the firing process of MLCC fabrication. This results in cracks in the MLCC. Therefore, in the present invention, a metal element other than titanium occupies part of the B site of the perovskite structure of the BTO particles (hereinafter, this metal element is referred to as a "substituting element") instead of the titanium that is normally present in the B site. This increases the thermal stability of the crystallites. It is believed that the presence of even one atom of a substituting element within a crystallite of the perovskite structure reduces the surface energy of the crystallite (i.e., stabilizes the crystallite), increasing the energy required for bonding between the crystallites. Furthermore, the presence of a substituting element on the surface side of the crystallite tends to lower the surface energy of the crystallite. Even if a substitution element is present inside (at the center) of a crystallite, it is assumed that the substitution element lowers the surface energy of the crystallite because the crystallite diameter of the BTO particle is small and the distance from the surface is short. However, if the crystallite diameter is too small, the thermal stability decreases, so a crystallite diameter of 5 nm or more is preferable. The crystallite diameter can be measured by XRD.

[0010] The higher the proportion of substitutional elements present in BTO particles, the lower the surface energy of the crystallites. Therefore, the ratio of the number of moles of substitutional elements (also called the amount of substance) B to the total number of moles of titanium Ti contained in the BTO particles [number of moles of substitutional elements B / (number of moles of titanium Ti + number of moles of substitutional elements B)] is preferably 0.5% or more. This ratio is more preferably 1% or more, and even more preferably 5% or more. However, the energy required for bonding between crystallites becomes high only up to this ratio of 50%. In other words, this is until the proportion of substitutional elements among the elements present in the B site is half.

[0011] The ionic radius of the metal element is Ti 4+The closer the radius is to (0.605 Å), the easier it is for the metal element to occupy the B site. Therefore, the ionic radius of the metal element is preferably 1.3 Å or less, and more preferably 1.0 Å or less. Elements with an ionic radius of 0.55 Å or more are also preferred. Here, the ionic radius is Shannon's ionic radius (Shannon et al., Acta A 32 (1976) 751.). Since Ti in BTO is six-coordinated, the ionic radius for six-coordinated elements is applied. The ionic radius for a tetravalent element (the same as the valence of titanium in BTO) is applied first. For metal elements that do not have a tetravalent element, the ionic radius for the valence closest to tetravalent is applied. If there are two closest valence elements, the larger one is applied. Two or more metal elements may exist as substitutional elements at the B site.

[0012] XRD can be used as an indicator of whether a metal element is present in the B site. The higher the proportion of substitutional elements present in the BTO particles, the lower the angle of the main peak of the perovskite structure. Therefore, the main peak position should preferably be 31.207 degrees or less.

[0013] Metal elements that occupy the B site include Zr, Dy, Mg, Nb, Y, Cu, Sn, and Zn.

[0014] Typically, MLCCs are fired at 1000-1300°C, where the dielectric layer sinters, and the temperature varies from room temperature to 1300°C during heating. Metallic Ni particles sinter around 500°C, but the co-material prevents this. When BTO particles in the MLCC bond together around 500°C, the effect of the co-material decreases, and metallic Ni particles in the electrode layer sinter around 500°C. In other words, the difference in sintering start temperature increases, causing cracks to occur in the MLCC. Therefore, we evaluated the thermal stability of BTO particles fired at 500°C by measuring the change in crystallite diameter (thermal shrinkage). Specifically, we compared the crystallite diameter D1 after firing the BTO particles at 500°C with the crystallite diameter D1 before firing. o The ratio (D1 / D o It can be said that the smaller the value of α, the lower the thermal shrinkage rate (higher the thermal stability). It is preferable to set the rate of increase in crystallite size to 1.3 or less.

[0015] Furthermore, if impurities exist outside the crystallites of the BTO particles, the impurities will turn into crystals other than the perovskite structure (impurity crystals) upon firing, degrading the performance of the MLCC. Increasing the metal element content in the BTO particles to increase the number of substitution elements makes it easier for metal elements that do not occupy the B site to exist as impurities outside the crystallites of the BTO particles. Therefore, from the perspective of reducing impurities, the ratio of the number of moles of metal elements M to the total amount of the number of moles of metal elements M and the number of moles of titanium Ti contained in the BTO particles [M / (Ti+M)] is preferably 35% or less, more preferably 10% or less. Whether or not BTO particles contain impurities can be determined by measuring the BTO particles after firing with XRD and analyzing peaks other than those of the perovskite structure. Specifically, the peak (I) that is assigned to a structure other than the perovskite structure and has the highest intensity is determined. i ) and the intensity of the main peak of the perovskite structure (I p If the amount of impurity crystals is small, the peak intensity ratio [I i / I p ] becomes smaller. In other words, the smaller the peak intensity ratio, the smaller the amount of impurities contained in the BTO particles before sintering. The peak intensity ratio is preferably 0.1 or less, more preferably 0.07 or less, and even more preferably 0.05 or less. The lower this value, the higher the proportion of substitution elements among the metal elements contained in the BTO particles. The proportion of substitution elements in BTO particles cannot be measured directly, but it can be determined by the peak intensity ratio [I i / I p The molar ratio [M / (Ti+M)] to the peak intensity ratio [M / (Ti+M)] can be used as an index of the proportion of the substitution element. When the peak intensity ratio is 0.1 or less, the molar ratio [M / (Ti+M)] is preferably 0.5% or more. The molar ratio [M / (Ti+M)] is more preferably 1% or more, and even more preferably 5% or more.

[0016] Examples of the shape of BTO particles include spherical, ellipsoidal (rugby ball), cocoon-like, confetti-like, chain-like, dice-like, etc. Spherical BTO particles can easily fit into the gaps between Ni particles.

[0017] The smaller the average particle size, the easier it is to apply to small MLCCs. Therefore, the average particle size of the dispersion measured by dynamic light scattering is preferably 100 nm or less. The average particle size is preferably 50 nm or less, more preferably 30 nm or less, and even more preferably 10 nm or less. Considering dispersibility in the solvent, the average particle size is preferably 1.5 nm or more. Note that the BTO particles after sintering at 500°C are sintered and therefore have an average particle size greater than 500 nm. This distinguishes them from BTO particles before sintering. The BTO particles in the dispersion take at least one of the following forms: primary particles (crystallites) and secondary particles consisting of multiple primary particles. BTO particles in the form of primary particles tend to be uniformly packed around the Ni in the electrode layer.

[0018] Whether BTO particles are in the form of primary particles can be determined by the ratio of average particle size to crystallite size (average particle size / crystallite size). The smaller this ratio, the fewer the number of crystallites that make up the BTO particles. For example, as this ratio decreases to 2 or less, 1 or less, and 0.5 or less, the number of crystallites that make up the BTO particles also decreases. Since it is difficult to prepare BTO particles with this ratio less than 0.1, the lower limit can be said to be 0.1.

[0019] When the ratio of the average particle size to the crystallite size (average particle size / crystallite size) is 2 or less, the smaller the crystallite size of the BTO particles, the easier it is to fill the BTO particles uniformly around the Ni in the electrode layer. Therefore, the crystallite size is preferably 20 nm or less, more preferably 15 nm or less, and even more preferably 12 nm or less.

[0020] BTO particles can be dispersed in both water and organic solvents. Water or organic solvents can be used as the solvent. When a highly polar organic solvent is used, BTO particles can be dispersed in the solvent without using a surface treatment agent. An example of a highly polar organic solvent is alcohol. On the other hand, when a less polar organic solvent is used, treating the surface of the BTO particles with a surface treatment agent makes it easier for the BTO particles to disperse in the organic solvent. Examples of less polar organic solvents include solvents with hydrophobic moieties such as alkyl groups with five or more carbon atoms or cyclic structures (five-membered rings, benzene rings, etc.). Examples of surface treatment agents include organic compounds with carboxylic acids or ketone groups.

[0021] The higher the solids concentration of the dispersion, the lower the transportation costs. Therefore, the solids concentration is preferably 5% by weight or more. On the other hand, the lower the solids concentration, the less likely the BTO particles are to aggregate. Therefore, the solids concentration is preferably 40% by weight or less.

[0022] Next, the method for producing BTO particles will be described. (Step 1) A solution of barium hydroxide in an alkyl cellosolve is prepared. (Step 2) The alkyl cellosolve solution is dehydrated at 40°C or higher. (Step 3) Titanium alkoxide is added to the alkyl cellosolve solution. (Step 4) A solvent containing water is added to the alkyl cellosolve solution. (Step 5) The alkyl cellosolve solution is aged at 20°C or higher for 6 hours or more.

[0023] Before the fourth step is performed, the alkyl cellosolve solution must contain a metal element compound. That is, a solvent containing water is added to the alkyl cellosolve solution containing the metal element compound. This causes barium titanate to crystallize in the alkyl cellosolve solution in the fifth step, resulting in BTO particles with a perovskite structure. The metal element occupies the B site of these BTO particles.

[0024] Ti 4+ Metal elements with an ionic radius close to the ionic radius of Ti (0.605 Å) tend to occupy the B site. Therefore, elements with an ionic radius of 0.55 Å or more are preferred. 4+It is more preferable that the ionic radius of the metal element is larger than the ionic radius (0.605 Å) of the metal element. The ionic radius of the metal element is preferably 1.3 Å or less, and more preferably 1.0 Å or less. Here, the ionic radius is the Shannon ionic radius mentioned above.

[0025] The higher the proportion of metal elements present in the alkyl cellosolve solution, the more metal elements will occupy the B site, lowering the surface energy of the crystallites. Therefore, in the alkyl cellosolve solution, the ratio of the number of moles of metal elements (M) to the sum of the number of moles of titanium (Ti) and the number of moles of metal elements (M) [M / (Ti+M)] is preferably 0.5% or more. On the other hand, the lower this proportion, the less likely the metal elements are to become impurities. Therefore, from the perspective of reducing impurities, this proportion is preferably 50% by weight or less, more preferably 35% or less, and even more preferably 10% or less.

[0026] The metal elements that do not occupy the B site of the added BTO particles remain outside the crystallites as impurities, preventing the crystallites from improving their thermal stability. Impurities can degrade the performance of MLCCs. The closer the atomic ratio (Ba / M+Ti) of the total metal element (M) and titanium (Ti) to barium (Ba) present in the alkyl cellosolve solution during aging is to 1, the less likely impurities are to be generated. Therefore, it is preferable to set the amounts of metal element and titanium alkoxide added so that this atomic ratio is in the range of 0.95 to 1.02. Furthermore, the use of titanium alkoxides with the structure Ti(OR)4 (where R is a hydrocarbon group with 1 to 4 carbon atoms and may be the same or different) reduces the generation of impurities. Tetraisopropoxytitanium is readily available and suitable for mass production.

[0027] Compounds of metal elements can be in the form of metal alkoxides or metal salts. When the compound is a metal alkoxide, it can be uniformly hydrolyzed together with titanium alkoxide, so impurities are less likely to be generated. It is preferable to use a metal alkoxide having the structure M(OR)4 (where R is a hydrocarbon group having 1 to 8 carbon atoms and may be the same or different). With alkoxides of this structure, the hydrolysis rate is easily adjusted, and therefore the particle size and crystallite size can be easily adjusted. From the viewpoint of hydrolysis rate, metal ethoxides and metal propoxides are easy to handle.

[0028] Each step will be described in detail below.

[0029] <First step> In this process, an alkyl cellosolve solution of barium hydroxide is prepared. The alkyl cellosolve interacts with barium hydroxide. This interaction causes barium hydroxide to dissolve in the alkyl cellosolve. The more dissolution progresses (the better the dissolution), the smaller the average particle size of BTO becomes. The fewer carbon atoms in the hydrocarbon group of the alkyl cellosolve, the more likely the interaction occurs. The carbon number is preferably 4 or less, more preferably 2 or less. Methyl cellosolve is preferred as the alkyl cellosolve. Furthermore, barium hydroxide is more easily dissolved by irradiating the alkyl cellosolve solution with ultrasound. Using barium alkoxide instead of barium hydroxide can reduce the average particle size, but the cost increases.

[0030] <Second process> In this step, water is removed from the alkyl cellosolve solution (i.e., the alkyl cellosolve solution is dehydrated). Water is generated when barium hydroxide interacts with the alkyl cellosolve. Removing this water promotes the interaction. When dehydrating, the higher the temperature of the alkyl cellosolve solution, the easier it is for barium hydroxide to interact with the alkyl cellosolve. When dehydrating, the temperature of the alkyl cellosolve solution is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. The higher this temperature, the easier it is to dehydrate, but if it is too high, there is a risk of bumping. To prevent bumping, the temperature is preferably 90°C or lower.

[0031] The longer the dehydration time, the more water can be removed, promoting the interaction. Therefore, a dehydration time of 10 minutes or more is preferable, and 30 minutes or more is more preferable. On the other hand, if the dehydration time is too long, production efficiency is low. The efficiency improves in the order of 10 hours or less, 5 hours or less, and 3 hours or less. Furthermore, the longer the dehydration time, the less likely barium hydroxide is to remain undissolved. The smaller the amount of undissolved residue, the higher the yield. The dehydration time may be set taking the amount of undissolved residue into consideration. For example, when dehydration is performed so that the amount of undissolved residue is less than 40% of the raw material, the particle yield will be 60% or more. The amount of undissolved residue is preferably less than 30%, and more preferably less than 2.5%.

[0032] Dehydration methods include (vacuum) distillation and methods using adsorbents such as silica gel and zeolite. When (vacuum) distillation is performed for a longer time, the amount of barium hydroxide dissolved increases. Therefore, it is preferable to perform the distillation for 30 minutes or more.

[0033] The lower the water content of the alkyl cellosolve solution after dehydration, the less likely impurities are generated when titanium alkoxide is added. Therefore, the water content is preferably less than 1 wt%, more preferably 0.8 wt% or less, and even more preferably 0.55 wt% or less.

[0034] It is preferable to separate undissolved compounds from the alkyl cellosolve solution after dehydration. The remaining barium hydroxide and metal elements react with substances in the air (CO2, etc.), producing barium salts (carbonates, etc.). These barium salts become impurities. If the dissolution of the hydroxide is promoted in the first step, the amount of impurities can be reduced. Separation methods include filtration and decantation. The alkyl cellosolve solution may be centrifuged before decantation.

[0035] <Third step> In this step, titanium alkoxide is added to the alkyl cellosolve solution. It is preferable to set the barium concentration in the alkyl cellosolve solution to 10% by weight or higher beforehand. A concentration of 10% by weight or higher facilitates uniform reaction of barium and metal elements with titanium in the alkyl cellosolve solution, reducing the likelihood of the formation of compounds other than perovskite structures (e.g., barium compounds, metal element compounds, or titanium compounds) after aging. On the other hand, the lower the concentration, the less likely impurities are to be generated. Therefore, the concentration is preferably 40% by weight or lower, more preferably 30% by weight or lower, and even more preferably 20% by weight or lower. The barium concentration can be adjusted at any step prior to this step. By selecting (reduced pressure) distillation as the concentration adjustment method, heating, dehydration, and concentration adjustment (concentration) can be performed simultaneously. This reduces the number of steps. Since a longer (reduced pressure) distillation time results in an excessively high barium concentration in the alkyl cellosolve solution, a time of 5 hours or less is preferred. The (reduced pressure) distillation time can be set taking into consideration the distillation temperature, barium concentration, amount of alkyl cellosolve solution, etc.

[0036] <Fourth process> In this process, a solvent containing water is added to the alkyl cellosolve solution, which hydrolyzes the titanium alkoxide. The alkyl cellosolve solution is then pre-mixed with a metal element compound. This facilitates uniform bonding of the metal element compound with the titanium alkoxide, facilitating the incorporation of the metal element into the B site of the BTO particles after aging. If the metal element compound is added after hydrolysis, it is added to the titanium alkoxide after hydrolysis. As a result, the titanium alkoxide and the metal element compound do not react uniformly, which can lead to the formation of impurities after aging. It is also preferable to dissolve the metal element compound in the alkyl cellosolve (preparing an alkyl cellosolve solution of the metal element [hereinafter referred to as the metal element solution]) before adding it to the alkyl cellosolve solution. The metal element solution can be prepared by dissolving the metal alkoxide in the alkyl cellosolve, or by interacting (dissolving) the metal element hydroxide with the alkyl cellosolve, as with barium hydroxide. By allowing the hydroxide of the metal element to interact with the alkyl cellosolve, the metal element can easily enter the B site.

[0037] The molar ratio of titanium alkoxide to water added to the alkyl cellosolve solution is preferably 6 or more. The higher the molar ratio, the more easily the hydrolysis of titanium alkoxide proceeds. This molar ratio is preferably 30 or less. The lower the molar ratio, the more uniform the hydrolysis and the less likely impurities are to be generated. In addition, the hydrolysis rate can be adjusted by adding a mixed solvent of alcohol and water. This allows for uniform hydrolysis. Uniform hydrolysis also reduces the generation of impurities. To reduce impurities, the weight ratio of alcohol to water (alcohol / water) is preferably 0.5 to 4.0, more preferably 1.5 to 3.5. In particular, when the molar ratio of water to be added and titanium alkoxide in the alkyl cellosolve solution is close to 8, for example, when the molar ratio is 7 to 9, the weight ratio of alcohol to water is preferably in the range of 1.5 to 3.5. Within this range, the particle size can be reduced.

[0038] <Fifth process> An alkyl cellosolve solution containing barium, metal elements, and titanium is heated to 20°C or higher. This matures the alkyl cellosolve solution, resulting in perovskite-structured particles. This method allows for perovskite-structured BTO particles to be obtained without a calcination process. Furthermore, by aging the alkyl cellosolve solution, the BTO particles can be crystallized while still dispersed in the solvent. This eliminates the need to remove the particles from the solvent for crystallization. Therefore, redispersing the BTO particles in the solvent during paste formation is not necessary, reducing the manufacturing process. Furthermore, aging tends to result in a uniform average particle size. Aging times below 20°C make it difficult to obtain the energy required for crystallization, resulting in long aging times and low productivity. Longer aging times above 20°C tend to reduce crystal defects in the BTO particles and improve thermal stability. Therefore, aging times of 6 hours or more are preferred, with 10 hours or more being more preferable. On the other hand, longer aging times result in poor production efficiency. For example, aging times of 500 hours or less are efficient.

[0039] Examples of the present invention will be specifically described below.

[0040] Example 1 <First step> 100 g of barium hydroxide octahydrate (Fujifilm Wako Pure Chemical Industries, Ltd.) and 630 g of 2-methoxyethanol (methyl cellosolve) were placed in a 1-L beaker and mixed. After mixing, the barium hydroxide was partially dissolved by ultrasonic irradiation at 40°C for 30 minutes to obtain an alkyl cellosolve solution.

[0041] <Second process> This alkyl cellosolve solution was placed in a 2-L eggplant-shaped flask and subjected to vacuum distillation using an evaporator. This meant that dehydration and concentration were simultaneously achieved. Distillation was carried out for 1 hour at 70°C and 15 hPa. The distilled alkyl cellosolve solution was centrifuged to precipitate undissolved compounds. The supernatant (alkyl cellosolve solution) was then decanted to separate the sediment (undissolved compounds). The sediment was white. The centrifugation conditions were 3000 rpm and 15 minutes. The barium concentration of the supernatant (alkyl cellosolve solution immediately before the addition of titanium alkoxide) measured by ICP-OES was 15.5 wt% and the water content was 0.86 wt%.

[0042] <Third step> In a glove box under a nitrogen gas atmosphere, 23.1 g of tetraisopropoxytitanium (Orgatix (registered trademark) TA-8, manufactured by Matsumoto Fine Chemical Co., Ltd.; Ti concentration 16.85 wt%) was added to 100 g of the supernatant from the second step and mixed. Subsequently, 1.40 g of zirconium tetra-n-butoxide (Orgatix ZA-65, manufactured by Matsumoto Fine Chemical Co., Ltd.; Zr concentration 20.7 wt%) was added and mixed.

[0043] <Fourth process> While stirring the alkylcellosolve solution at 25°C, a mixed solvent of 48.9 g of methanol and 16.3 g of water was added over 1 minute, and the mixture was then stirred at 25°C for 2 hours.

[0044] <Fifth process> The alkyl cellosolve solution was heated to 80°C and aged for 48 hours to obtain a dispersion of BTO particles. 20 g of this dispersion was dried at 130°C for 1 hour to obtain a powder of BTO particles. 5 g of the BTO particle powder was placed in a crucible and heated to 500°C over 2.5 hours, then fired at 500°C for 3 hours. After cooling to 400°C, the powder was placed in a desiccator and cooled to room temperature to obtain a 500°C-fired product.

[0045] The preparation conditions for the dispersion liquid are shown in Table 1, along with other examples and comparative examples. The physical properties of the obtained particles were measured by the following methods. The measurement results for other examples and comparative examples are shown in Table 2. The "BTO particles" column in Table 2 lists the measured values ​​for the dispersion liquid of BTO particles from the fifth step and the product dried at 130°C (BTO particle powder). The "BTO particles after 500°C baking" column lists the measured values ​​for the product baked at 500°C and the dispersion liquid. The crystallite diameter of the product dried at 130°C was D o The crystallite diameter of the product fired at 500°C is D1, and D1 / D o was calculated.

[0046] (1) Crystal structure (crystallite size, peak intensity ratio, main peak) The target powder was pulverized and used as a measurement sample. The crystal structure was measured using a Rigaku MiniFlex® 600 X-ray diffraction analyzer. The crystal structure can be identified using the analysis software PDXL2. The crystallite diameter was calculated by measuring the half-width β of the main peak of the perovskite structure and calculating it from the half-width β (rad) using the Scherrer formula "D = Kλ / β cosθ." Here, D is the crystallite diameter (Å), K is the Scherrer constant, λ is the X-ray wavelength (1.7889 Å), and θ is the reflection angle. Note that BTO particles have at least one of a tetragonal and a cubic crystal structure. If the crystal structure is tetragonal, the half-width β of the Miller index "101" is measured, and if it is cubic, the half-width β of the Miller index "110" is measured. Using the analysis software PDXL2 (version 2.0.3.0), a peak search (hybrid search match) was performed to obtain the ratio [I i / I p In addition, the main peak position (deg) was measured. In the tetragonal crystal, the peak at Miller index "101" is the main peak, and in the cubic crystal, the peak at Miller index "110" is the main peak.

[0047] (2) Average particle size of BTO particles 1 g of the dispersion was filled into a measurement cell. To make the cell uniform, the liquid in the cell was sucked up with a dropper and then returned to the cell. This process was repeated twice to prepare a sample for measurement. The particle size distribution of the dispersion was measured by dynamic light scattering using a particle size distribution analyzer (Nanotrac (registered trademark) UPA-UT151 manufactured by Nikkiso Co., Ltd.). The median diameter (D50) calculated from the particle size distribution was used as the average particle size. 0.5 g of the product calcined at 500°C was mixed with 10 g of 2-methoxyethanol and subjected to an ultrasonic dispersion treatment to prepare a sample for measurement of the product calcined at 500°C. The measurement was carried out using the same procedure as above. The average particle size / crystallite size was also calculated.

[0048] (3) Molar ratio [M / (Ti+M)] 0.2 g of BTO particle powder, 2 g of sodium hydrogen peroxide, and 1 g of sodium hydroxide were mixed and melted, then dissolved in hydrochloric acid and measured using an ICP-OES (Agilent 5800) to calculate the mole ratio [M / (Ti+M)].

[0049] Example 2 This example is the same as Example 1 except for the following difference: the amount of Orgatix ZA-65 added in the third step was 14.0 g.

[0050] Example 3 This example is similar to Example 1, except for the following differences: the amount of Orgatix ZA-65 added in the third step was 27.9 g.

[0051] Example 4 This example is the same as Example 1 except for the following difference: In the third step, 10.8 g of dysprosium isopropoxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added instead of Orgatix ZA-65.

[0052] Example 5 This example is the same as Example 1 except for the following difference: In the third step, 0.36 g of magnesium ethoxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Mg concentration 21.5 wt %) was added instead of Orgatix ZA-65.

[0053] Example 6 This example is similar to Example 1, except for the following difference: 1.79 g of magnesium ethoxide was added in place of Orgatix ZA-65 in the third step.

[0054] Example 7 This example is similar to Example 1, except for the following difference: in the third step, 3.58 g of magnesium ethoxide was added instead of Orgatix ZA-65.

[0055] Example 8 This example is similar to Example 1, except for the following difference: in the third step, 7.17 g of magnesium ethoxide was added instead of Orgatix ZA-65.

[0056] Example 9 This example is similar to Example 1, except for the following difference: in the third step, 1.79 g of magnesium ethoxide and 6.97 g of Orgatix ZA-65 were added instead of Orgatix ZA-65.

[0057] Example 10 This example is the same as Example 1 except for the following difference: In the third step, 4.22 g of yttrium acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added instead of Orgatix ZA-65.

[0058] Comparative Example 1 This comparative example differs from Example 1 in the following respects: Orgatix ZA-65 was not added in the third step.

[0059] [Table 1]

[0060]

Table 2

Claims

1. A dispersion liquid containing barium titanate particles having a perovskite structure and a solvent, The barium titanate particles have a crystallite diameter of 25 nm or less, A dispersion in which a portion of titanium present in the B site of the perovskite structure is substituted with a metal element other than titanium.

2. 2. The dispersion according to claim 1, wherein when the barium titanate particles are measured using an X-ray diffraction measuring device, a main peak of the perovskite structure is detected at 31.207 deg or less.

3. When the sintered product obtained by sintering the barium titanate particles at 500 ° C. is measured by an X-ray diffraction measurement device, the crystallite diameter D １ and the crystallite diameter D of the barium titanate particles before firing o The ratio [D １ / D o 2. The dispersion according to claim 1, wherein the value of (a) is 1.3 or less.

4. When the sintered product obtained by sintering the barium titanate particles at 500°C is measured by an X-ray diffraction measurement device, the peak I, which is the highest intensity and is attributed to a structure other than the perovskite structure, is i and the intensity of the main peak of the perovskite structure, I p Ratio to [I i / I p 2. The dispersion according to claim 1, wherein the value of (a) is 0.1 or less.

5. The dispersion liquid according to claim 4, characterized in that the ratio [M / (Ti+M)] of the number of moles of the metal element (M) to the total amount of the number of moles of the metal element (M) contained in the barium titanate particles and the number of moles of titanium (Ti) contained in the barium titanate particles is 0.5% or more.

6. 2. The dispersion according to claim 1, wherein the average particle size measured by dynamic light scattering is 100 nm or less.

7. a first step of preparing a solution of barium hydroxide in an alkyl cellosolve; a second step of dehydrating the alkyl cellosolve solution at a temperature of 40°C or higher; a third step of adding a titanium alkoxide to the alkyl cellosolve solution; a fourth step of adding a solvent containing water to the alkyl cellosolve solution containing a compound of a metal element (excluding titanium and barium); and a fifth step of aging the alkyl cellosolve solution at 20°C or higher for 6 hours or more.

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