Method for producing zirconate compound, zirconate compound and sintered body thereof

Abstract

To provide a method for producing a zirconic acid compound having a fine and perovskite structure.SOLUTION: A method for producing a zirconic acid compound having a perovskite structure includes a step (4) of obtaining a zirconic acid compound by mixing a hydroxide with zirconium hydroxide having a BET specific surface area of 300 m2 / g or more, and a step (5) of drying the zirconic acid compound at 400°C or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a zirconate compound, a method for producing the same, and a sintered body thereof. [Background technology]

[0002] Currently, barium titanate is the main raw material used for ceramic capacitors. Other dielectric materials with perovskite structures, such as barium titanate zirconate, strontium titanate, calcium titanate, strontium zirconate, and calcium zirconate, are also known as major raw materials, and are broadly categorized into low-dielectric-constant and high-dielectric-constant types based on their material properties. Low-dielectric-constant types have a small rate of capacitance change due to temperature, and are also known as temperature-compensated types.

[0003] Among these materials, a common method for producing fine calcium zirconate is to mix fine zirconium oxide and fine calcium carbonate and then calcinate them, as shown in Patent Document 1. In the examples of this patent, the BET specific surface area is 25 m 2 / g of calcium zirconate has been obtained.

[0004] Patent Document 1 also describes a method for obtaining calcium zirconate with a size of 10 to 100 nm by spray-drying fine zirconium oxide and fine calcium carbonate, followed by firing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-200297 Summary of the Invention [Problem to be solved by the invention]

[0006] As described in Patent Document 1, it is said that it is impossible to obtain a fine zirconate compound by the aqueous solution method. Furthermore, among conventionally known methods for producing zirconate compounds having a perovskite structure, for example, a method including a heating step at about 600 to 900°C to obtain calcium zirconate is known, as described in Patent Document 1. However, such crystal grain growth by heat treatment promotes particle aggregation, and there is a trade-off between particle miniaturization and improved crystallinity. For this reason, it has been difficult to obtain a zirconate compound having both nano-level fineness and high crystallinity by conventional production methods.

[0007] The present invention has been made to solve the above-mentioned problems, and aims to provide a method for producing a fine zirconate compound having a perovskite structure, a zirconate compound, and a sintered body thereof. The zirconate compound has excellent reactivity (shrinkage) when heated, making it suitable as a material for ceramic capacitors. [Means for solving the problem]

[0008] The present invention includes the following [1] to

[11] . [1] BET specific surface area is 300m 2 1. A method for producing a zirconate compound, comprising: step (4) mixing zirconium hydroxide having a saturation of 1 / 2 g or more with a hydroxide to obtain a zirconate compound; and step (5) drying the zirconate compound at 400°C or less. [2] A method for producing a zirconate compound according to the above [1], comprising: a step (1) of neutralizing a zirconium salt to obtain a zirconium hydroxide slurry; and a step (3) of keeping the zirconium hydroxide slurry at a temperature of 60 to 130°C. [3] The method for producing a zirconic acid compound according to [2] above, wherein the zirconium salt is at least one selected from the group consisting of zirconium oxychloride octahydrate and zirconium nitrate dihydrate. [4] The method for producing a zirconate compound according to [1] or [2] above, wherein the hydroxide comprises at least one selected from calcium hydroxide, barium hydroxide, and strontium hydroxide. [5] The method for producing a zirconic acid compound according to any one of the above [1] to [4], wherein in step (4), the zirconium hydroxide is a slurry containing zirconium hydroxide. [6] The BET specific surface area of ​​the zirconium hydroxide is 360 m 2 The method for producing a zirconic acid compound according to any one of [1] to [5] above, wherein the zirconic acid compound has a viscosity of 1000 saturations .... [7] The method for producing a zirconate compound according to any one of the above [1] to [6], wherein titanium oxide is further mixed in the step (4). [8] The method for producing a zirconate compound according to any one of the above [1] to [7], wherein the proportion of zirconium atoms (Zr) in 100 mol % of atoms contained in the B site of the perovskite structure is 50 to 100 mol %. [9] A BET specific surface area of ​​50 m obtained by the manufacturing method according to any one of [1] to [8] above. 2 / g or more.

[10] The zirconate compound according to [9] above, having an average primary particle size of 5.0 to 30.0 nm.

[11] A sintered body of the zirconate compound according to [9] or

[10] above. [Effects of the Invention]

[0009] The present invention provides a method for producing a fine zirconate compound having a perovskite structure, a zirconate compound, and a sintered body thereof. The zirconate compound has excellent reactivity (shrinkage) when heated, making it suitable as a material for ceramic capacitors. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a chart of an X-ray diffraction spectrum of Example 1. [Figure 2] 1 is a chart of an X-ray diffraction spectrum of Example 2. [Figure 3] 1 is a chart of an X-ray diffraction spectrum of Example 3. [Figure 4] 1 is a chart of an X-ray diffraction spectrum of Example 4. [Figure 5] 1 is a chart of an X-ray diffraction spectrum of Comparative Example 1. [Figure 6] 1 is a chart of an X-ray diffraction spectrum of Comparative Example 2. [Figure 7] 1 is a chart of an X-ray diffraction spectrum of Comparative Example 3. [Figure 8] 1 is a chart of an X-ray diffraction spectrum of Comparative Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Method of producing zirconate compound] The method for producing a zirconate compound having a perovskite structure of the present invention is to produce a zirconate compound having a BET specific surface area of ​​300 m 2 The method includes a step (4) of mixing zirconium hydroxide having a specific surface area of ​​1 / 2 g or more with a hydroxide to obtain a zirconate compound, and a step (5) of drying the zirconate compound at 400° C. or less. By using this production method, a fine zirconate compound with excellent crystallinity can be produced. The present production method preferably further includes at least one of the following steps (1) to (3), more preferably includes at least steps (1) and (3), and more preferably includes all of steps (1) to (3).

[0012] Step (1) is a step of obtaining a zirconium hydroxide slurry by neutralizing a zirconium salt with an alkaline solution. Step (2) is a step of washing the zirconium hydroxide slurry. Step (3) is a step of keeping the zirconium hydroxide slurry at a temperature of 60 to 130°C. In step (4), a BET specific surface area of ​​300 m 2 This is a process for obtaining a zirconate compound by mixing zirconium hydroxide having a solubility of 1 / g or more with hydroxide. Step (5) is a step of drying the zirconate compound at 400°C or less. By using such a production method, it is possible to produce a zirconate compound that is finer and has excellent crystallinity.

[0013] In the present invention, a "zirconate compound having a perovskite structure" refers to a compound having at least a zirconium atom (Zr) at the B site of the perovskite structure and one or more metal atoms other than the zirconium atom (Zr) at the A site of the perovskite structure. Here, the B site refers to the 12-coordinated portion of the perovskite structure, and the A site refers to the 6-coordinated portion of the perovskite structure. The composition formula is represented by ABO3, where A represents the A site, B represents the B site, and O represents an oxygen atom.

[0014] (Metal atom (A)) The metal atom (A) is a metal atom that constitutes the A site, and is preferably one or more types selected from calcium (Ca) atoms, barium (Ba) atoms, and strontium (Sr) atoms. The metal atom (A) constituting the A site of the zirconate compound having a perovskite structure may be one type or two or more types.

[0015] (Metal atom (B)) The metal atom (B) is a metal atom that constitutes the B site, and is preferably one or more types selected from titanium (Ti) atoms, hafnium (Hf) atoms, and cerium (Ce) atoms. At least a zirconium (Zr) atom is present in the B site of the zirconate compound having a perovskite structure, and one or more of the above metal atoms (B) may also be present in addition to the zirconium (Zr) atom. The proportion of zirconium atoms (Zr) in 100 mol% of atoms contained in the B site of the perovskite structure is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%, still more preferably 75 to 100 mol%, and even more preferably 80 to 100 mol%.

[0016] <Process (1)> Step (1) is a step of neutralizing a zirconium salt to obtain a zirconium hydroxide slurry. In step (1), it is preferable to neutralize an aqueous zirconium salt solution containing water as a dispersion medium with an alkaline solution to obtain a zirconium hydroxide slurry. Specific examples of the zirconium salt include zirconium oxychloride octahydrate, zirconium nitrate dihydrate, zirconium sulfate tetrahydrate, and zirconium oxyacetate. These may be used alone or in combination of two or more. Among these, zirconium oxychloride octahydrate and zirconium nitrate dihydrate are preferred, with zirconium oxychloride octahydrate being more preferred. This is because it is generally used as a raw material for zirconia compounds and is therefore advantageous in terms of cost and availability.

[0017] In the present invention, the content of water in the total amount of the dispersion medium in the slurry is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and still more preferably 100% by mass.

[0018] Neutralization is preferably carried out on the alkaline side with a pH greater than 7.0, more preferably in the pH range of 7.5 to 9.0, and even more preferably in the pH range of 7.5 to 8.5. Specifically, an acidic aqueous solution of the zirconium salt is added dropwise to a sufficient amount of alkaline solution and the reaction is carried out while maintaining the pH on the alkaline side, thereby obtaining fine zirconium hydroxide with a large specific surface area. When the neutralization reaction is carried out on the alkaline side, 2 It is easy to obtain zirconium hydroxide of 0.1g or more.

[0019] Examples of the alkaline solution used in the neutralization reaction include aqueous ammonia and various hydroxide solutions. These may be used alone or in combination of two or more. From the standpoint of environmental considerations and contamination, the hydroxide is preferably a hydroxide of the metal atom (A) constituting the A site of the synthesis target or the metal atom (B) constituting the B site. Specifically, calcium hydroxide is more preferred. The neutralization reaction can be carried out in the air at room temperature, but is preferably carried out at a low temperature because a smaller amount of alkaline agent is required for precipitation. The temperature of the reaction atmosphere is preferably 10 to 40°C, more preferably 15 to 30°C, and even more preferably 15 to 25°C.

[0020] The concentration of the zirconium salt in the aqueous solution of the zirconium salt is preferably 0.5 to 5 mol / L, more preferably 1 to 2 mol / L, and even more preferably 1 to 1.5 mol / L. If it is 1 mol or more, the reaction efficiency will be high, and if it is 2 mol or less, the reaction uniformity will be high.

[0021] <Process (2)> Step (2) is a step of washing the zirconium hydroxide slurry obtained in step (1), and is carried out for the purpose of washing away chlorine and nitric acid contained in the raw material zirconium salt. Specifically, washing can be carried out by adding a large amount of water to the zirconium hydroxide slurry, stirring it, and then discarding the supernatant solution by decantation. As long as the conditions are such that the microstructure of the zirconium hydroxide is not destroyed, methods such as ultrafiltration, centrifugation, and filter press can also be used instead of decantation. The washing is preferably carried out in the air at room temperature, preferably 10 to 40°C, more preferably 15 to 30°C, and even more preferably 15 to 25°C.

[0022] <Process (3)> Step (3) is a step of keeping the zirconium hydroxide slurry obtained in step (1) or (2) at a temperature of 60 to 130°C. This increases the fineness of the slurry and makes it possible to obtain a zirconium hydroxide slurry having a BET specific surface area of ​​300m 2 / g or more, thereby increasing the reactivity in step (4). The temperature for keeping the slurry is preferably 60 to 130°C, more preferably 60 to 120°C, even more preferably 70 to 100°C, still more preferably 75 to 90°C, and most preferably 75 to 85°C, from the viewpoint of increasing the fineness of the slurry. For example, when the zirconium hydroxide slurry obtained in the step (2) is kept at 80°C for 12 hours and then dried at 120°C for 24 hours, the BET specific surface area is 400 m 2 On the other hand, when the drying was performed at 120°C without heat retention, the microstructure of 300-350m / g was obtained. 2 / g of zirconium hydroxide.

[0023] The incubation time is preferably 1 hour or more, more preferably 5 to 96 hours, even more preferably 10 to 48 hours, and still more preferably 10 to 24 hours, from the viewpoint of increasing the fineness of the slurry and shortening the production time.

[0024] <Process (4)> In step (4), a BET specific surface area of ​​300 m 2 This is a process for synthesizing a zirconate compound by mixing zirconium hydroxide having a solubility of 1 / g or more with hydroxide to cause a reaction. The zirconium hydroxide is preferably a slurry containing zirconium hydroxide, as this increases reactivity, and more preferably a slurry containing zirconium hydroxide and water. The zirconium hydroxide used is preferably one produced by the above process (3).

[0025] The hydroxide is a hydroxide containing a metal atom other than zirconium (Zr) atom, and is preferably a hydroxide containing metal atom (A). Specific examples include calcium hydroxide, barium hydroxide, and strontium hydroxide, with calcium hydroxide being more preferred from the standpoint of cost. The hydroxide containing metal atom (A) may be one type or multiple types.

[0026] Furthermore, a compound containing a metal atom (B) may be further added, or one or more compounds selected from oxides and peroxides containing a metal atom (A) may be further added. The compound containing a metal atom (B) is a compound containing at least one of titanium (Ti) atoms, hafnium (Hf) atoms, and cerium (Ce) atoms. It may be an oxide, and specific examples include titanium oxide, hafnium oxide, and cerium oxide, with titanium oxide being preferred.

[0027] The metal atom (A) may be added in an amount of 0.8 mol or more but less than 1.2 mol, or 0.9 mol or more but less than 1.1 mol, per mole of the total of zirconium atoms in the zirconium hydroxide and metal atom (B). The proportion of zirconium atoms (Zr) in 100 mol % of atoms constituting the B site is preferably 50 to 100 mol %, more preferably 60 to 100 mol %, even more preferably 70 to 100 mol %, still more preferably 75 to 100 mol %, and even more preferably 80 to 100 mol %.

[0028] The BET specific surface area of ​​zirconium hydroxide is 300m 2 / g or more, preferably 360m 2 / g or more, more preferably 400m 2 / g or more. This is because the finer the raw material, the easier the reaction will proceed. 2 This is because by mixing with zirconium hydroxide at a concentration of 1 / g or more, it is possible to achieve a reaction at a lower temperature than conventional methods. The step (4) can be carried out in an air atmosphere at room temperature, preferably at a temperature of 10 to 40°C, more preferably at a temperature of 15 to 30°C, and even more preferably at a temperature of 15 to 25°C. The mixing can be carried out using a ball mill, a bead mill, or the like, and the mixture may be stirred in a container with a stirring blade. The mixing and stirring time in the step (4) is preferably 1 to 36 hours, more preferably 6 to 24 hours, and even more preferably 10 to 15 hours. The stirring rotation speed in the synthesis step is preferably 10 to 200 rpm, more preferably 30 to 150 rpm, and even more preferably 50 to 100 rpm.

[0029] <Process (5)> The step (5) is a step of drying the zirconate compound obtained in the step (4), whereby the liquid is evaporated to obtain the zirconate compound. The drying method is not particularly limited and may include hot air drying, drying under an inert gas, vacuum drying, and the like. The drying temperature is 400°C or lower, preferably 300°C or lower, more preferably 200°C or lower, and more preferably 120°C or lower, and most preferably drying at room temperature of 40°C or lower. Drying at 400°C or lower allows the specific surface area to remain high. Heat treatment (calcination) at a higher temperature, for example, above 400°C, promotes aggregation of the resulting zirconate compound and reduces its fineness. From the viewpoint of evaporating the liquid, a temperature of 0°C or higher is preferred, and 20°C or higher is more preferred. The drying time is preferably 1 to 48 hours, more preferably 12 to 36 hours, and even more preferably 20 to 30 hours. The obtained zirconate compound is fine and can be used as a material for a ceramic capacitor without pulverization or crushing, but depending on the application, it may be pulverized or crushed and classified by a known method to prepare a classified product with a desired particle size.

[0030] [Zirconate Compound] The zirconate compound according to one embodiment of the present invention is obtained by the above-described production method, and has a BET specific surface area of ​​50 m 2 / g or more. The zirconate compound that satisfies the above production requirements is fine and has excellent crystallinity, and therefore can be suitably used as a raw material for various applications such as ceramic capacitors, piezoelectric elements, abrasives, catalysts, etc. In particular, it is suitable as a raw material for dielectric materials that require thin films.

[0031] (BET specific surface area) In one embodiment of the present invention, the zirconate compound preferably has a BET specific surface area of ​​50 m 2 / g or more, more preferably 60m 2 / g or more, more preferably 65m 2 / g or more, and even more preferably 65m 2 / g or more, and even more preferably 80m 2 / g or more, and even more preferably 100m 2 / g or more, and even more preferably 150m 2 / g or more, and even more preferably 180m 2 / g or more. BET specific surface area is 50m 2 / g or more, it can be said that the fineness and dispersibility required for raw materials of dielectric materials such as ceramic capacitors are obtained. On the other hand, the upper limit of the BET specific surface area is 400m 2 / g or less. 2 From the same viewpoint, it is preferable that the molecular weight is 300m / g or less, which is excellent from the viewpoint of handling. 2 / g or less, more preferably 200m 2 / g or less.

[0032] The BET specific surface area referred to in the present invention is a value measured by the BET flow method (three-point method) using nitrogen gas as the adsorbate in accordance with JIS R 1626:1996. Specifically, it is a value measured using a fully automatic BET specific surface area measuring device described in the Examples below. This BET specific surface area is an index of the fineness of the zirconate compound, and it can be said that the larger the value of this BET specific surface area, the finer the zirconate compound.

[0033] (Powder X-ray diffraction spectrum) In the zirconate compound according to one embodiment of the present invention, the presence of a perovskite structure can be confirmed by checking a peak at 29.5° to 33.0° in a powder X-ray diffraction spectrum using CuKα as a radiation source. Generally, there is a trade-off between fineness and crystallinity, and heat treatment during synthesis promotes crystallization, resulting in sharp peaks, but at the expense of fineness. A good balance of fineness and crystallinity is required for raw materials for dielectric materials such as ceramic capacitors.

[0034] (Average primary particle size) The zirconate compound in one embodiment of the present invention has an average primary particle size of preferably 5.0 to 100.0 nm, more preferably 5.0 to 30.0 nm, even more preferably 10.0 to 30.0 nm, still more preferably 10.0 to 20.0 nm, and even more preferably 10.0 to 15.0 nm. Zirconate compounds falling within the above range can be suitable raw materials for dielectric materials such as ceramic capacitors. A narrow particle size distribution is preferable. The average primary particle diameter referred to in the present invention is a value calculated by taking the average of the major axis and minor axis of any 20 particles in an image of a sample observed with a field emission scanning electron microscope (FE-SEM), excluding the 5 largest and 5 smallest data points from the 20 data points, and averaging the remaining 10 data points.

[0035] [Sintered body] The sintered body according to one embodiment of the present invention is obtained by sintering the zirconate compound having the perovskite structure. The sintered body can be suitably produced by pressing the zirconate compound to form it, and then heating it. The pressure during pressure molding is preferably 1 to 50 MPa, more preferably 5 to 30 MPa, and even more preferably 5 to 15 MPa. The heating temperature is preferably 800 to 1300°C, more preferably 1000 to 1250°C, and even more preferably 1100 to 1200°C.

[0036] [Application] The zirconate compound of the present invention can be suitably used as a raw material for dielectric materials such as strontium zirconate, calcium zirconate, and barium zirconate. For example, calcium zirconate can be synthesized by a known method in which a mixture of the zirconate compound and calcium carbonate is heated to cause a solid-phase reaction, but by using the fine zirconate compound of the present invention, fine calcium zirconate useful as a dielectric material can be obtained. [Example]

[0037] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0038] [Production of zirconate compounds] Example 1 <Process (1)> In the air at room temperature (25°C), 100 g of pure water was placed in a 500 mL fluororesin beaker 1 and stirred, followed by the addition of 10.0 g (0.135 mol) of calcium hydroxide (Ca(OH)2, manufactured by Kanto Chemical Co., Inc.; the same applies hereinafter) to form a suspension. Next, 43.2 g (0.134 mol) of zirconium oxychloride octahydrate (ZrCl2O·8H2O, manufactured by Kanto Chemical Co., Inc.; the same applies hereinafter) was placed in beaker 2, followed by the addition of 100.0 g of pure water, and the mixture was stirred to dissolve. In the air at room temperature (25°C), the zirconium oxychloride aqueous solution in beaker 2 was added dropwise to beaker 1 while maintaining the pH in beaker 1 on the alkaline side, and neutralization was carried out. After mixing, stirring was continued for approximately 3 hours to neutralize the solution. The pH was 8.1. The pH was measured using a portable pH meter ("D-74," manufactured by Horiba, Ltd., 25°C).

[0039] <Process (2)> The contents of beaker 1 were transferred to a 10 L container, and approximately 8 L of pure water was added in the air at room temperature (25°C), and after stirring, the mixture was allowed to settle for 1 hour. The supernatant liquid was discarded and decanted 10 times to wash away the chlorine and calcium. Sufficient washing and removal was confirmed by checking with the pH meter that the conductivity of the supernatant was less than 50 μS / cm.

[0040] <Process (3)> The solution containing the obtained precipitate was sealed in the air, kept in an oven at 80°C for 12 hours, and then returned to room temperature to obtain a finely divided zirconium hydroxide slurry. The zirconium hydroxide slurry was dried in air at 120°C for 2 days to produce a dry powder, and the BET specific surface area of ​​the dry powder was measured and found to be 412 m 2 / g.

[0041] <Process (4)> The obtained zirconium hydroxide slurry was transferred to a 500 mL container of a ball mill, and together with YTZ balls Φ0.5 (500 g) and Φ5 (100 g), 51.3 g (0.163 mol) of barium hydroxide (Ba(OH)2) and 2.6 g (0.033 mol) of titanium oxide (TiO2) were added, and the mixture was mixed and stirred using a ball mill in the air at room temperature (25°C) for 12 hours at 72 rpm. <Process (5)> The powder was then dried in air at 120°C for 24 hours to obtain a dry powder. Figure 1 shows the diffraction spectrum of the dry powder obtained. 0.8 Ti 0.2 An XRD peak corresponding to O3 was obtained.

[0042] Example 2 In step (4), 38.63 g (0.122 mol) of barium hydroxide (Ba(OH)), 2.27 g (0.031 mol) of calcium hydroxide (Ca(OH)), and 1.83 g (0.023 mol) of titanium oxide (TiO) were added and mixed, and in step (5), the mixture was dried at room temperature (25°C), but the same treatment as in Example 1 was carried out. The diffraction spectrum of the dry powder obtained is shown in Figure 2. Because calcium hydroxide was used, calcium was incorporated into the A site, resulting in a good perovskite structure. 0.2 Ba 0.8 Zr 0.85 Ti 0.15 A peak corresponding to O3 was observed.

[0043] Example 3 The same procedure as in Example 1 was repeated except that in step (4), 28.48 g (0.107 mol) of strontium hydroxide octahydrate (Sr(OH)2·8H2O), 14.49 g (0.046 mol) of barium hydroxide (Ba(OH)2), and 1.83 g (0.023 mol) of titanium oxide (TiO2) were added and mixed, and in step (5), the mixture was dried at room temperature (25°C). Figure 3 shows the diffraction spectrum of the resulting dry powder. Sr 0.7 Ba 0.3 Zr 0.85 Ti 0.15 A peak of the perovskite structure that can be identified as O3 was obtained.

[0044] Example 4 The same treatment as in Example 1 was carried out except that in step (4), 9.73 g (0.131 mol) of calcium hydroxide (Ca(OH)2) was added and mixed at 72 rpm for 150 hours, and in step (5), the mixture was dried at room temperature (25°C). The diffraction spectrum of the obtained dry powder is shown in Figure 4. Although it was a small amount, a peak that could be identified as calcium zirconate with a perovskite structure was observed.

[0045] (Comparative Example 1) The same treatment as in Example 1 was carried out, except that in step (4), 15.82 g (0.107 mol) of strontium carbonate (SrCO), 9.06 g (0.046 mol) of barium carbonate (BaCO), and 1.83 g (0.023 mol) of titanium oxide (TiO) were added and mixed, and in step (5), the mixture was dried at room temperature (25°C). Figure 5 shows the diffraction spectrum of the obtained dry powder.

[0046] (Comparative Example 2) The production was carried out in the same manner as in Example 1, except that the step of keeping the temperature at 80°C in an oven was omitted in step (3) and the mixing time was set to 150 hours in step (4). The zirconium hydroxide slurry was dried in the air at 120°C for 2 days to obtain a dry powder. The BET specific surface area of ​​the zirconium hydroxide was 293 m 2 / g. Figure 6 shows the diffraction spectrum of the obtained dry powder.

[0047] (Comparative Example 3) The production was carried out in the same manner as in Example 1, except that drying in step (5) was carried out at 700° C. Figure 7 shows the diffraction spectrum of the obtained dry powder.

[0048] Comparative Example 4 The zirconium hydroxide slurry obtained up to step (3) of Example 1 was dried in the air at 120°C for 2 days to form a dry powder, which was then heat-treated in air at 1000°C for 8 hours to form zirconium oxide. 16 g (0.13 mol) of this zirconium oxide, 13 g (0.13 mol) of calcium carbonate (special grade reagent, manufactured by Kanto Chemical Co., Ltd.), and 100 g of water were mixed and mixed in a ball mill for 150 hours. After drying, the mixture was heat-treated at 900°C for 2 hours. Figure 8 shows the diffraction spectrum of the dry powder obtained. Although good crystals were obtained, it was found that the specific surface area was lower than in the other examples, and the shrinkage rate was also smaller.

[0049] [Analysis and measurement of powder] (BET specific surface area) In accordance with JIS R 1626:1996, the BET specific surface area was measured using a fully automatic BET specific surface area measuring device (Macsorb (registered trademark) HM model-1208, manufactured by Mountec Co., Ltd.) by the BET three-point method using nitrogen gas as the adsorbate.

[0050] (Average primary particle size) The average primary particle size of the sample powder was determined by SEM observation. The sample piece for observation was prepared by placing the powder sample on a 3 mm square silicon wafer piece that had been washed with ethanol, and then fixing the silicon wafer piece to a sample stage with conductive double-sided tape. SEM observation was performed at a magnification of 300,000x, and the major and minor axes of 20 randomly selected particles were measured in the observed image, and the average was taken as the particle size. Of these 20 particle size data, the five largest and five smallest values ​​were removed, and the average of the remaining 10 values ​​was calculated, and this value was taken as the average primary particle size.

[0051] (Powder X-ray diffraction measurement) X-ray diffraction measurements were performed using an X-ray diffractometer (X'pert PRO, manufactured by PANalytical) with a copper target, CuKα radiation (Cu-Kα1), a tube voltage of 45 kV, a tube current of 40 mA, a measurement range of 2θ = 18° to 80°, a sampling width of 0.0167°, and a scanning speed of 3.3° / min. Furthermore, each crystal system was identified by Rietveld analysis (software used: "RIETAN-FP").

[0052] (shrinkage rate) 2.50 g of the resulting zirconate compound powder was weighed out and placed in a 30 mm diameter circular mold, compressed and molded at 10 MPa. The oven was then heated at a rate of 5°C / min up to a thermocouple reading of 1150°C. This temperature was maintained for two hours, after which the heater was disconnected. After 12 hours, the sample was removed and the shrinkage measured. The shrinkage was calculated by measuring two perpendicular diameters, averaging these values ​​as A mm, and then calculating (A / 30)-1. The temperature of a Referthermo (JFCC Practical Reference Material Series TYPE L1) placed in the oven at the same time was 1147°C.

[0053] [Table 1]

[0054] As can be seen from the results shown in Table 1 and the figures, the zirconate compounds of Examples 1 to 4 had a perovskite structure. In addition, the zirconate compounds containing any of Ba, Ca, and Sr as the metal atom (A) could also be obtained. By using fine, highly reactive zirconium hydroxide as a starting material, it was found that any of the above compounds can form a perovskite structure at room temperature. Because the reaction takes place at room temperature, it is possible to obtain fine particles that could not be obtained by conventional methods. Furthermore, all of the compounds described above exhibited the excellent effect of a large shrinkage rate. A large shrinkage rate indicates that a dense film can be formed at a low temperature, making it possible to manufacture ceramic capacitors at a lower temperature than conventional methods. Therefore, the zirconate compounds obtained in the examples can be said to be suitable materials for dielectrics that require thin films.

[0055] Comparative Example 1 was formulated with the aim of achieving the same structure as Example 3, but no peaks were observed that could be attributed to the perovskite structure of the zirconate compound. This is thought to be because carbonates were used as raw materials, rather than hydroxides. In Comparative Example 2, the compound was formulated with the aim of achieving the same structure as in Example 1, but no peaks were observed that would be expected to represent the perovskite structure of the zirconate compound. This suggests that the specific surface area of ​​zirconium hydroxide plays an important role in this reaction. The zirconic acid compound obtained in Comparative Example 3 had the same structure as the zirconic acid compound obtained in Example 1, but had a lower specific surface area and a smaller shrinkage rate of the molded body, due to the high temperature in step (5). Comparative Example 4 was calcium zirconate produced from zirconium oxide and calcium carbonate by a conventionally known method, and had a low specific surface area and a small shrinkage rate of the molded body. [Industrial Applicability]

[0056] As described above, the dielectric material produced using the zirconate compound of the present invention can be suitably used for the ceramic layer of a ceramic capacitor. In addition, the zirconate compound of the present invention can be suitably used for various applications such as abrasives, catalysts, and component materials for small electronic devices, taking advantage of its fine and excellent crystallinity.

Claims

1. BET specific surface area is 300m ２ 1. A method for producing a zirconate compound, comprising: a step (4) of mixing zirconium hydroxide having a saturation of 1 / 2 g or more with a hydroxide to obtain a zirconate compound; and a step (5) of drying the zirconate compound at 400°C or less.

2. 2. The method for producing a zirconate compound according to claim 1, comprising: a step (1) of neutralizing a zirconium salt to obtain a zirconium hydroxide slurry; and a step (3) of maintaining the zirconium hydroxide slurry at a temperature of 60 to 130°C.

3. 3. The method for producing a zirconic acid compound according to claim 2, wherein the zirconium salt is at least one selected from the group consisting of zirconium oxychloride octahydrate and zirconium nitrate dihydrate.

4. 3. The method for producing a zirconate compound according to claim 1, wherein the hydroxide comprises at least one selected from the group consisting of calcium hydroxide, barium hydroxide, and strontium hydroxide.

5. 5. The method for producing a zirconic acid compound according to claim 1, wherein in step (4), the zirconium hydroxide is a slurry containing zirconium hydroxide.

6. The BET specific surface area of ​​the zirconium hydroxide is 360 m ２ The method for producing a zirconic acid compound according to any one of claims 1 to 5, wherein the zirconic acid compound has a solubility of 1 / g or more.

7. The method for producing a zirconic acid compound according to any one of claims 1 to 6, wherein titanium oxide is further mixed in step (4).

8. The method for producing a zirconate compound according to any one of claims 1 to 7, wherein a ratio of zirconium atoms (Zr) to 100 mol% of 100 mol% of atoms contained in the B site of the perovskite structure of the zirconate compound is 50 to 100 mol%.

9. The zirconate compound has a BET specific surface area of ​​50 m ２ The method for producing a zirconate compound according to any one of claims 1 to 8, having a perovskite structure in which the zirconia content is 1 / g or more.

10. The method for producing a zirconate compound according to claim 9, wherein the average primary particle diameter of the zirconate compound is 5.0 to 30.0 nm.

11. A method for producing a sintered body, comprising sintering the zirconate compound according to claim 9 or 10.

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