Barium titanyl oxalate, method for producing the same, and method for producing barium titanate

Abstract

This invention provides barium oxalate oxytannin, which yields barium titanate with small particle size and high crystallinity, and provides an industrially advantageous method for manufacturing the barium oxalate oxytannin. The barium oxalate oxytannin is characterized in that, in thermogravimetric analysis, a weight reduction rate of 99% relative to 1000°C is achieved at a temperature of 600–700°C. The method for manufacturing the barium oxalate oxytannin is characterized by mixing a solution containing oxalic acid (solution A) with a solution containing a titanium compound and a barium compound (solution B) and reacting them to produce barium oxalate oxytannin. In this method, solution A is first added to a reaction vessel, and then solution B is mixed into solution A while stirring it within the reaction vessel. The mixing time of solution B into solution A is less than 10 seconds from start to finish.

Description

Technical Field

[0001] This invention relates to barium titanium oxalate, which is useful as a raw material for functional ceramics such as dielectrics, piezoelectrics, optoelectronic materials, semiconductors, and sensors, and its manufacturing method. Background Technology

[0002] Currently, barium titanate is manufactured using solid-state methods, hydrothermal synthesis methods, alkoxide methods, oxalate methods, and other methods.

[0003] In solid-state synthesis, a dry method is used to manufacture powders by mixing the constituent raw materials and heating the mixture at high temperatures. The resulting powder forms irregularly shaped aggregates, requiring further high-temperature calcination to achieve the desired properties. While hydrothermal synthesis offers the advantage of good powder properties, its complex synthesis process and reliance on autoclaves result in poor productivity, high powder production costs, and industrial disadvantages. Similarly, the alkoxide method suffers from difficult and expensive starting material processing, also hindering industrial development.

[0004] Compared to hydrothermal synthesis and alkoxide methods, barium titanate obtained by the oxalate method can be produced inexpensively with a uniform composition. Furthermore, it exhibits a more uniform composition compared to barium titanate produced by solid-state methods. The existing oxalate method typically involves reacting a titanium source such as titanium tetrachloride, a barium source such as barium chloride, and oxalic acid in a solvent such as water to obtain barium oxalate oxytitanium, followed by calcination of the barium oxalate oxytitanium (see, for example, Patent Documents 1-3).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Publication No. 2005-500239

[0008] Patent Document 2: Japanese Patent Application Publication No. 2010-202610

[0009] Patent Document 3: Japanese Patent Application Publication No. 2013-63867 Summary of the Invention

[0010] The technical problem that the invention aims to solve

[0011] However, the barium titanate oxalate obtained in the aforementioned patent literature is generated by firing at temperatures above 700°C. Therefore, at the moment of barium titanate formation, the crystallinity is low, but some degree of grain growth occurs. When such barium titanate oxalate is fired at high temperatures, even with high crystallinity, the particles are large, which fails to meet the requirements for use as a functional ceramic raw material.

[0012] Therefore, the object of the present invention is to provide barium oxalate oxytannin that can produce barium titanate with small particle size and high crystallinity, and to provide an industrially advantageous method for manufacturing the barium oxalate oxytannin.

[0013] Technical solutions for solving technical problems

[0014] Based on the above-mentioned actual situation, the inventors of this invention have repeatedly and carefully studied the matter and discovered that by shortening the mixing time of the solution containing titanium and barium compounds (liquid B) to the solution containing oxalic acid (liquid A), fine barium oxalate titanium oxide can be obtained. When such fine barium oxalate titanium oxide is calcined, carbon dioxide is easily released during thermal decomposition, which can lower the temperature at which barium titanate is generated. Furthermore, by generating barium titanate at a low temperature, compared with the prior art, barium titanate can be highly crystallized at a low temperature, thus inhibiting the grain growth of barium titanate. Therefore, compared with the prior art, microparticle and highly crystalline barium titanate can be obtained, thereby completing this invention.

[0015] That is, the present invention (1) provides a barium titanium oxalate, characterized in that: in thermogravimetric analysis, the temperature at which the weight reduction rate reaches 99% relative to the weight reduction rate at 1000°C is 600-700°C.

[0016] Furthermore, the present invention (2) provides barium titanium oxalate of (1), characterized in that: by heating it in the atmosphere at 700±10°C for 2 hours, it can be transformed into a product with a specific surface area of ​​15-20 m². 2 Barium titanate with a c / a ratio of 1.0030 to 1.0055.

[0017] In addition, the present invention (3) provides barium oxalate as described in (1) or (2), characterized in that: the average particle size is less than 1.0 μm.

[0018] In addition, the present invention (4) provides a method for manufacturing barium titanium oxalate, characterized in that: a solution containing oxalic acid (solution A) is mixed with a solution containing titanium compound and barium compound (solution B), and the mixture is reacted to produce barium titanium oxalate.

[0019] In the method for manufacturing barium titanium oxalate, firstly, liquid A is added to a reaction vessel. Then, while stirring liquid A in the reaction vessel, liquid B is mixed into liquid A. The mixing time of liquid B into liquid A from start to finish is within 10 seconds.

[0020] In addition, the present invention (5) provides a method for manufacturing barium oxalate oxytannin (4), characterized in that the solvent of the above-mentioned liquid A is an organic solvent.

[0021] In addition, the present invention (6) provides a method for manufacturing barium oxalate oxytitanium of (5), characterized in that: the solvent of the above-mentioned liquid A is one or more selected from methanol, ethanol, propanol, butanol, diethyl ether, 1,3-butanediol, ethylene glycol, propylene glycol, dipropylene glycol, glycerol, N,N-dimethylformamide and acetone.

[0022] In addition, the present invention (7) provides a method for manufacturing barium oxalate oxytannin (4), characterized in that the solvent of the above-mentioned liquid B is water.

[0023] In addition, the present invention (8) provides a method for manufacturing barium titanium oxalate according to any one of (4) to (7), characterized in that: the titanium compound in the above-mentioned liquid B is titanium tetrachloride and the barium compound is barium chloride.

[0024] In addition, the present invention (9) provides a method for manufacturing barium titanium oxalate according to any one of (4) to (8), characterized in that the mixing temperature of the above-mentioned liquid B to the above-mentioned liquid A is 40°C or less.

[0025] In addition, the present invention (10) provides a method for manufacturing barium oxalate oxytannin as described in any one of (4) to (9), characterized in that the average particle size of the generated barium oxalate oxytannin is less than 1.0 μm.

[0026] In addition, the present invention (11) provides a method for manufacturing barium titanate, characterized in that: barium oxalate titanate obtained by any one of the manufacturing methods (4) to (10) is calcined.

[0027] Invention Effects

[0028] This invention provides a barium titanate oxalate that, when calcined at the same temperature, yields barium titanate with smaller particle size and higher crystallinity compared to conventional barium titanate oxalate. Furthermore, this invention also provides an industrially advantageous method for manufacturing this barium titanate oxalate. Attached Figure Description

[0029] Figure 1 The results are the thermogravimetric analysis results of barium oxalate obtained in Example 1 and Comparative Example 1.

[0030] Figure 2 This is a SEM image of barium titanium oxalate obtained in Example 1.

[0031] Figure 3 This is an SEM image of barium titanate obtained in Example 1.

[0032] Figure 4 This is a SEM image of barium titanium oxalate obtained in Comparative Example 1.

[0033] Figure 5The image shown is a SEM image of the fired product obtained in Comparative Example 1. Detailed Implementation

[0034] The present invention relates to barium oxalate oxytitanium, characterized in that, in thermogravimetric analysis (TGA), the temperature at which the weight reduction rate reaches 99% relative to the weight reduction rate at 1000°C is 600–700°C, preferably 610–690°C, and particularly preferably 615–685°C. Here, the weight reduction rate at 1000°C in TGA refers to the weight reduction rate at the moment when the analysis temperature of the TGA is 1000°C. Furthermore, the temperature at which the weight reduction rate reaches 99% relative to the weight reduction rate at 1000°C in TGA refers to the temperature at which the weight reduction rate reaches 99% of the weight reduction rate at the moment when the analysis temperature is 1000°C, relative to the start of the analysis.

[0035] In thermogravimetric analysis (TGA), the temperature at which the weight loss rate reaches 99% relative to 1000°C refers to the temperature at which the thermal decomposition of barium oxalate into barium titanate ends, i.e., the temperature at which barium oxalate is converted into barium titanate. Regarding the weight loss measured by TGA for barium oxalate, when the sample is heated from room temperature at a rate of 10°C / min, some weight loss is confirmed, and then no weight loss is confirmed near 700°C, thus ultimately confirming thermal decomposition into barium titanate. Existing barium oxalate shows no weight loss at 700–720°C, thus confirming the formation of barium titanate within this temperature range. However, the barium oxalate of this invention shows no weight loss at 600–700°C, preferably 610–690°C, and particularly preferably 615–685°C, therefore, compared to the prior art, barium titanate can be obtained from barium oxalate at lower temperatures. For this reason, the inventors of the present invention consider that the barium oxalate oxalate obtained by the manufacturing method of the present invention described later has an average particle size of very small, preferably less than 1.0 μm, particularly preferably 0.01 to 0.5 μm, and therefore easily releases carbon dioxide during thermal decomposition, and is converted into barium titanate at low temperature compared with the prior art.

[0036] In thermogravimetric analysis, the barium oxalate of the present invention achieves a weight reduction rate of 99% relative to 1000°C at a temperature of 600–700°C, preferably 610–690°C, and particularly preferably 615–685°C. This allows barium titanate to be generated within a temperature range of 600–700°C, preferably 610–690°C, and particularly preferably 615–685°C. Therefore, the barium oxalate of the present invention can generate barium titanate at low temperatures, thus enabling high crystallinity of barium titanate at low temperatures compared to existing technologies. Furthermore, by utilizing the barium oxalate of the present invention, barium titanate can be highly crystallized at low temperatures compared to existing technologies, thereby suppressing barium titanate grain growth. Therefore, compared to existing technologies, microparticle and highly crystalline barium titanate can be obtained. Thus, by utilizing the barium oxalate of the present invention, when calcined at the same temperature, fine and highly crystalline barium titanate can be obtained compared to conventional barium oxalate. On the other hand, when the temperature at which the weight reduction rate reaches 99% exceeds 700°C relative to the weight reduction rate of 1000°C, the temperature at which barium titanate is generated from barium oxalate increases, and therefore the subsequent heating temperature for high crystallinity also increases, resulting in a larger particle size of barium titanate.

[0037] There are no particular limitations on the thermogravimetric analysis apparatus used in the thermogravimetric analysis of barium oxalate; for example, the TGA / DSC 1 manufactured by METTLER TOLEDO Co., Ltd. can be cited.

[0038] The present invention preferably transforms barium oxalate oxytitanium into a specific surface area of ​​15-20 m² by heating in the atmosphere at 700±10°C for 2 hours. 2 Barium titanate oxalate of the present invention has a c / a ratio of 1.0030 to 1.0055. The barium titanate obtained by heating the barium titanate oxalate of the present invention in air at 700 ± 10 °C for 2 hours has a particularly preferred specific surface area of ​​16 to 19 m². 2 / g. Furthermore, the c / a of barium titanate obtained by heating barium titanate at 700±10°C for 2 hours in atmosphere according to the present invention is particularly preferably 1.0035 to 1.0050. By utilizing barium titanate generated by heating at 700±10°C for 2 hours in atmosphere, where the specific surface area and c / a are within the above range, even if grain growth occurs during the firing process due to heating for high crystallinity after barium titanate formation, fine and highly crystalline barium titanate can be obtained compared to conventional barium titanate. Regarding the heating test of barium titanate, the test sample is held for 2 hours in a heating apparatus with the temperature adjusted to 700±10°C. After cooling, the specific surface area and c / a of the test sample after the heating test are determined by BET method and X-ray diffraction analysis.

[0039] The average particle size of barium titanate oxalate of the present invention is preferably 1.0 μm or less, more preferably 0.005 to 1.0 μm, and particularly preferably 0.01 to 0.5 μm. With the average particle size of barium titanate oxalate within the above range, barium titanate can be generated at low temperatures. In this invention, the average particle size of barium titanate oxalate is determined by randomly measuring 200 particles using a scanning electron microscope (SEM), and the average value is taken as the average particle size.

[0040] Furthermore, the barium oxalate oxytannin of the present invention is barium oxalate oxytannin that can generate barium titanate when heated in a temperature range of 600-700°C, preferably 610-690°C, and particularly preferably 615-685°C.

[0041] The manufacturing method of the present invention will now be described based on its preferred embodiments.

[0042] The method for manufacturing barium titanium oxalate of the present invention is characterized in that: a solution containing oxalic acid (solution A) is mixed with a solution containing titanium compound and barium compound (solution B) and reacted to produce barium titanium oxalate. In the method for manufacturing barium titanium oxalate, solution A is first added to a reaction vessel. Then, solution B is mixed into solution A while stirring solution A in the reaction vessel. The mixing time of solution B into solution A from start to finish is within 10 seconds.

[0043] The method for manufacturing barium titanium oxalate of the present invention involves a solution A containing oxalic acid. The concentration of oxalate ions in solution A is not particularly limited, but is preferably 0.1–7.0 mol / L, and particularly preferably 0.6–5.0 mol / L.

[0044] The solvent for solution A can be an aqueous solvent, an organic solvent, or a mixture thereof. From the viewpoint of obtaining barium titanium oxalate microparticles, an organic solvent is preferred. As for the organic solvent, there are no particular limitations as long as it is hydrophilic and inert to the raw materials; one or more solvents selected from methanol, ethanol, propanol, butanol, diethyl ether, 1,3-butanediol, ethylene glycol, propylene glycol, dipropylene glycol, glycerol, N,N-dimethylformamide, and acetone can be used. In the case of a mixture of water and an organic solvent, or a mixture of multiple organic solvents, the mixing ratio can be appropriately selected.

[0045] The method for manufacturing barium titanium oxalate of the present invention involves a solution B containing a titanium compound and a barium compound. The concentration of titanium ions in solution B is not particularly limited, but is preferably 0.04–4.0 mol / L, and particularly preferably 0.2–3.0 mol / L. Similarly, the concentration of barium ions in solution B is not particularly limited, but is preferably 0.08–6.5 mol / L, and particularly preferably 0.4–3.0 mol / L.

[0046] The titanium compound used in the method for manufacturing barium titanium oxalate of the present invention is not particularly limited, and examples include titanium tetrachloride and titanium lactate. One type of titanium compound may be used, or two or more may be used in combination. Titanium tetrachloride is preferred as the titanium source.

[0047] The barium compound used in the method for manufacturing barium titanium oxalate of the present invention is not particularly limited, and examples include barium chloride, barium carbonate, barium hydroxide, barium acetate, and barium nitrate. One type of barium compound may be used, or two or more may be used in combination. Preferably, the barium compound is selected from one or more of barium chloride, barium carbonate, and barium hydroxide, with barium chloride being particularly preferred.

[0048] In the method for manufacturing barium titanium oxalate of the present invention, liquid A is added to a reaction vessel, and then, while stirring liquid A in the reaction vessel, liquid B is supplied to liquid A and mixed, thereby carrying out the reaction to generate barium titanium oxalate in the reaction vessel.

[0049] At this point, regarding the mixing of liquid B into the reaction vessel containing liquid A, the mixing time from start to finish is within 10 seconds, preferably within 8 seconds. By ensuring that the mixing time from start to finish of liquid B into liquid A is within the above range, particulate barium titanium oxalate can be obtained.

[0050] The temperature at which liquid B is mixed with liquid A, i.e. the temperature of the reaction liquid (liquid A) and liquid B in the reaction vessel when liquid B is added, is preferably below 40°C, and particularly preferably 5 to 30°C.

[0051] The mixing amount of liquid B into liquid A is preferably 0.01 to 20, and more preferably 0.1 to 10, in a ratio of the total number of moles of titanium and barium in liquid B (based on atomic conversion) to the number of moles of oxalic acid in liquid A.

[0052] The reaction can be terminated by adding all of solution B to solution A, and then removing the reaction solution by filtration after mixing solution B with solution A. Alternatively, all of solution B can be added to solution A, and after mixing solution B with solution A, the reaction solution can be aged at a specified temperature for a certain period of time. The aging temperature is preferably below 40°C, particularly preferably 5–30°C; the aging time is preferably 0.5–40 hours, particularly preferably 1–24 hours.

[0053] When adding and mixing solution B to solution A, it is preferable to add solution B while stirring solution A. Furthermore, if all the solution B is added to solution A and aging is performed after mixing of solution B into solution A, it is preferable to age the reaction solution while stirring. There are no particular limitations on the stirring speed; as long as the reaction solution containing the generated barium titanium oxalate remains in a flowing state until aging is complete, any stirring speed is acceptable.

[0054] When all the contents of solution B are added to solution A and aging is performed after the mixing of solution B into solution A is complete, solid-liquid separation of the reaction solution can be performed using conventional methods after aging. The solid portion is then washed with water. There are no particular limitations on the washing method, but washing by re-pulping or similar methods is preferred for high washing efficiency. After washing, the solid portion is dried and pulverized as needed to obtain barium titanium oxalate.

[0055] According to the above operation, the barium oxalate oxytitanate obtained by the method for manufacturing barium oxalate of the present invention exhibits a weight reduction rate of 99% relative to 1000°C at a temperature of 600–700°C, preferably 610–690°C, and particularly preferably 615–685°C in thermogravimetric analysis. Therefore, the barium oxalate oxytitanate obtained by the method for manufacturing barium oxalate of the present invention is barium oxalate oxytitanate that yields barium titanate when calcined at 600–700°C, preferably 610–690°C, and particularly preferably 615–685°C.

[0056] The average particle size of barium oxalate obtained by the method for manufacturing barium oxalate of the present invention is preferably 1.0 μm or less, more preferably 0.005 to 1.0 μm, and particularly preferably 0.01 to 0.5 μm.

[0057] Regarding the composition of the barium oxalate obtained by the method for manufacturing barium oxalate according to the present invention, the Ba / Ti molar ratio is 0.998 to 1.004, preferably 0.999 to 1.003.

[0058] The barium titanate oxalate obtained by the method of the present invention is suitable for use as a raw material in the manufacture of barium titanate-based ceramics, which are dielectric ceramic materials. The method for manufacturing barium titanate of the present invention is as follows.

[0059] The method for manufacturing barium titanate of the present invention is characterized by calcining the barium titanate oxalate obtained by the method for manufacturing barium titanate oxalate of the present invention.

[0060] Organic matter from oxalic acid in the final product is undesirable because it impairs the dielectric properties of the material and is a major factor contributing to instability during the thermal process of ceramicization. Therefore, in this invention, it is necessary to obtain the target barium titanate by thermally decomposing barium titanate oxalate through firing, and to thoroughly remove the organic matter from oxalic acid. Regarding firing conditions, the firing temperature is preferably 600–1200°C, more preferably 620–1100°C. When the firing temperature is below 600°C, only a portion of barium titanate is generated, or it is difficult to obtain a single-phase barium titanate. On the other hand, when the firing temperature exceeds 1200°C, the particle size deviation becomes larger. The firing time is preferably 0.5–30 hours, more preferably 1–20 hours. In addition, there are no particular limitations on the firing atmosphere; it can be carried out in an inert gas atmosphere, a vacuum atmosphere, an acidic gas atmosphere, or in the atmosphere, or firing can be carried out in the above atmospheres while introducing water vapor.

[0061] The firing process can be repeated several times as needed. Alternatively, to ensure uniform powder properties, the product after one firing can be pulverized and then fired again.

[0062] After calcination, the material is appropriately cooled and then pulverized as needed to obtain barium titanate powder. The pulverization is suitable when the calcined barium titanate is brittle and in blocky form. The barium titanate particles themselves possess the following specific average particle size and BET specific surface area. Specifically, the average particle size of the obtained barium titanate powder, as determined by scanning electron microscopy (SEM), is preferably 0.5 μm or less, more preferably 0.02–0.5 μm. The BET specific surface area is preferably 2–100 m². 2 / g, more preferably 2.5 to 50 mg 2 / g. Furthermore, regarding the composition of barium titanate obtained using the manufacturing method of the present invention, the molar ratio of Ba to Ti (Ba / Ti) is preferably 0.998 to 1.004, particularly preferably 0.999 to 1.003. Additionally, the specific surface area of ​​barium titanate is 15 m² / g. 2 When the specific surface area is in the range of / g or higher, the c-axis / a-axis ratio, which is an indicator of crystallinity, is preferably 1.0030 to 1.0055, and particularly preferably 1.0035 to 1.0050. As the firing temperature increases, grain growth occurs, resulting in a specific surface area of ​​less than 15 m². 2 Within the range of / g, the c-axis / a-axis ratio is preferably greater than 1.0055, more preferably 1.0070 or more, and particularly preferably 1.0075 or more.

[0063] Furthermore, in the barium titanate obtained by the method for manufacturing barium titanate of the present invention, if necessary, in order to adjust the dielectric properties and temperature properties, a compound containing a secondary component element can be added to the barium titanate obtained by the method for manufacturing barium titanate of the present invention, thereby making it contain a secondary component element. Examples of compounds containing a secondary component element that can be used include compounds containing at least one element selected from rare earth elements selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, as well as Ba, Li, Bi, Zn, Mn, Al, Si, Ca, Sr, Co, Ni, Cr, Fe, Mg, Ti, V, Nb, Mo, W, and Sn.

[0064] Compounds containing secondary components can be any type of inorganic or organic compound. Examples include oxides, hydroxides, chlorides, nitrates, oxalates, carboxylates, and alkoxides containing the aforementioned elements. When the compound containing the secondary component is a Si compound, in addition to oxides, silica sol or sodium silicate can also be used. One type of compound containing the secondary component can be used, or two or more can be used in appropriate combinations. The amount added and the combination of compounds added can be determined according to standard methods.

[0065] To incorporate byproduct elements into barium titanate, it can be prepared by uniformly mixing barium titanate with a compound containing byproduct elements before firing. Alternatively, it can be prepared by uniformly mixing barium oxalate oxytitanium with a compound containing byproduct elements before firing.

[0066] When manufacturing a multilayer ceramic capacitor using barium titanate obtained by the method of manufacturing barium titanate according to the present invention, firstly, barium titanate powder is mixed and dispersed in a suitable solvent with known additives, organic binders, plasticizers, dispersants, and other compounding agents including by-component elements, and then slurryed and formed into a sheet. This yields a ceramic sheet for manufacturing a multilayer ceramic capacitor. In manufacturing the multilayer ceramic capacitor from this ceramic sheet, firstly, a conductive paste for forming internal electrodes is printed on one surface of the ceramic sheet. After drying, multiple of the above-mentioned ceramic sheets are stacked and pressed together in the thickness direction to form a multilayer body. Next, the multilayer body is heat-treated, then subjected to a binder removal treatment, and fired to obtain a fired body. Then, Ni paste, Ag paste, nickel alloy paste, copper paste, copper alloy paste, etc., are coated onto the fired body and baked to obtain a multilayer ceramic capacitor.

[0067] Furthermore, when the barium titanate powder obtained by the barium titanate manufacturing method of the present invention is incorporated into resins such as epoxy resin, polyester resin, and polyimide resin to form resin sheets, resin films, adhesives, etc., it can be used as a material for printed circuit boards and multilayer printed circuit boards. In addition, it can also be used as a common material for suppressing the shrinkage difference between internal electrodes and dielectric layers, electrode ceramic circuit boards, glass ceramic circuit boards, circuit peripheral materials, and dielectric materials for inorganic EL.

[0068] Furthermore, the barium titanate obtained by the method of manufacturing barium titanate of the present invention is suitable for use as a surface modifier for printing ink cartridges used in reactions such as removing waste gas and chemical synthesis, and for imparting antistatic and cleaning effects.

[0069] Example

[0070] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.

[0071] (1) Thermogravimetric analysis of barium titanium oxalate

[0072] Thermogravimetric analysis was performed using a TGA / DSC 1 thermogravimetric analyzer manufactured by METTLER TOLEDO Co., Ltd., with a 30 mg sample being measured in an air flow of 50 mL / min, from 30 °C to 1200 °C at a heating rate of 10 °C / min.

[0073] (2) Average particle size of barium oxalate and barium titanate

[0074] Using scanning electron microscope (SEM) images, 200 particles were randomly measured, and their average value was taken as the average particle size.

[0075] (3) Specific surface area of ​​barium titanate

[0076] The result is obtained using the BET method.

[0077] (4) c / a value of barium titanate

[0078] As the radiation source, Cu-Kα rays were used, and the ratio c / a of the c-axis to the a-axis was determined using an X-ray diffraction apparatus (manufactured by Bruker, D8ADVANCE).

[0079] (Example 1)

[0080] 25.0 g of oxalic acid dihydrate was dissolved in 100 g of ethylene glycol to prepare 120 mL of a solution containing oxalic acid (solution A) with a concentration of 2.21 mol / L. In addition, 64.4 g of titanium tetrachloride and 32.0 g of barium chloride were dissolved in 210 g of pure water to prepare 270 mL of a solution containing titanium and barium (solution B) with a concentration of 0.59 mol / L titanium tetrachloride and 0.63 mol / L barium chloride.

[0081] Next, while stirring solution A, solution B was added in 2-second increments. After maintaining the mixture for 3 hours, solid-liquid separation was performed to obtain a precipitate. The precipitate was washed and dried to obtain barium titanium oxalate. The physical properties of the obtained barium titanium oxalate are shown in Table 1. Furthermore, the weight loss rate of the obtained barium titanium oxalate was measured by thermal analysis, and the results are presented below. Figure 1 As a result, the weight reduction rate at 680°C was 44.90%, compared to 45.28% at 1000°C, for a total reduction of 99.16%.

[0082] The obtained barium oxalate was calcined at 700℃ for 2 hours to obtain barium titanate. The physical properties of the obtained barium titanate are shown in Table 1.

[0083] (Examples 2-4)

[0084] The barium oxalate barium titanate obtained in Example 1 was calcined at the temperatures shown in Table 1 to obtain barium titanate. The physical properties of the obtained barium titanate are shown in Table 1.

[0085] (Comparative Example 1)

[0086] 35.0 g of barium chloride dihydrate and 35.0 g of oxalic acid dihydrate were dissolved in 120 g of pure water to prepare 120 mL of a solution (solution a) containing barium and oxalic acid with a barium concentration of 1.10 mol / L and an oxalic acid concentration of 2.20 mol / L. Separately, 54.0 g of titanium tetrachloride was dissolved in pure water to prepare 260 mL of a titanium solution (solution b) containing titanium with a titanium concentration of 0.40 mol / L.

[0087] Next, while stirring solution a, solution b was added over 90 seconds. After maintaining the mixture for 1 hour, solid-liquid separation was performed to obtain a precipitate. The precipitate was washed and dried to obtain barium titanium oxalate. The physical properties of the obtained barium titanium oxalate are shown in Table 1. Furthermore, the weight loss rate of the obtained barium titanium oxalate was measured by thermal analysis, and the results are shown below. Figure 1 As a result, the weight reduction rate at 680°C was 37.71%, compared to 44.81% at 1000°C, for a total reduction of 84.15%.

[0088] The obtained barium titanate oxalate was calcined at 700°C for 2 hours. However, according to the results of thermogravimetric analysis of the weight loss rate, barium titanate was not obtained.

[0089] (Comparative Examples 2-4)

[0090] The barium oxalate barium titanate obtained in Comparative Example 1 was calcined at the temperatures shown in Table 1 to obtain barium titanate. The physical properties of the obtained barium titanate are shown in Table 1.

[0091] [Table 1]

[0092]

[0093] As shown in Table 1, based on a comparison of the average particle size, BET specific surface area, and c / a values ​​when fired at the same temperature, the barium titanate obtained in the examples is microparticle and highly crystalline compared to the barium titanate obtained in the comparative examples. Furthermore, as... Figure 1 As shown, thermogravimetric analysis determined that the barium oxalate oxytannin obtained in Example 1 yielded barium titanate at 700°C, but the barium oxalate oxytannin obtained in Comparative Example 1 did not yield barium titanate even at 700°C.

Claims

1. A method for manufacturing barium titanium oxalate, characterized in that: Solution A, containing oxalic acid, is mixed with solution B, containing titanium and barium compounds, and the mixture is allowed to react to produce barium titanium oxalate. The barium titanium oxalate exhibits a weight reduction rate of 99% relative to 1000°C in thermogravimetric analysis performed by heating from 30°C at a rate of 10°C / min, occurring at temperatures between 600 and 690°C. The average particle size of the barium titanium oxalate is less than 1.0 μm. In the method for manufacturing barium titanium oxalate, firstly, solution A is added to a reaction vessel; then, while stirring solution A in the reaction vessel, solution B is mixed into solution A. The mixing time of liquid B into liquid A from start to finish is within 10 seconds. The solvent for solution A is an organic solvent, and the solvent for solution B is water.

2. The method for manufacturing barium titanium oxalate as described in claim 1, characterized in that: The solvent of solution A is selected from one or more of methanol, ethanol, propanol, butanol, diethyl ether, 1,3-butanediol, ethylene glycol, propylene glycol, dipropylene glycol, glycerol, N,N-dimethylformamide, and acetone.

3. The method for manufacturing barium titanium oxalate as described in claim 1 or 2, characterized in that: The titanium compound in liquid B is titanium tetrachloride, and the barium compound is barium chloride.

4. The method for manufacturing barium titanium oxalate as described in claim 1 or 2, characterized in that: The mixing temperature of liquid B into liquid A is below 40°C.

5. A method for manufacturing barium titanate, characterized in that: Barium titanium oxalate is obtained by the manufacturing method according to any one of claims 1 to 4, and the barium titanium oxalate is then calcined.

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