Manufacturing method of fired body

Abstract

To provide a production method of a fired body including barium titanate and having good quality while suppressing deterioration of a firing jig.SOLUTION: The production method of a fired body is provided, comprising a molding step of molding clay including a titanium compound and a barium compound as ceramic raw material, thereby obtaining a fired body, and a firing step of placing the molded body on a firing jig, firing the molded body, thereby obtaining a fired body including barium titanate. The molded body has a portion having a height of 1 mm or more from the placement surface when placed on the firing jig. The firing step satisfies at least one of the following conditions. (1) the firing jig is made of zirconia with a porosity of 20% or more. (2) bedding powder is placed between the firing jig and the molded body, and the bedding powder is one or more selected from the bedding powder made of barium titanate, the bedding powder made of zirconia, and the bedding powder made of yttria.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a fired body. [Background technology]

[0002] Ceramic products are widely used in various parts such as heater elements, heat exchangers, exhaust gas treatment parts, and catalyst carriers. Ceramic products are manufactured by sintering a molded body obtained by molding clay (molding material) containing ceramic raw materials. When firing the molded body, the firing jig may react with the molded body, causing discoloration and fusion of the fired body (ceramic product), which can reduce the quality of the fired body. In addition, the firing jig itself deteriorates, making it difficult to reuse it.

[0003] To prevent the reaction between the firing jig and the compact, it has been proposed to use a firing jig with a thermally sprayed layer of calcium zirconate and yttria-stabilized zirconia on the surface of an alumina-silica substrate (Patent Document 1). It has also been proposed to use a firing jig with a fired layer of a stabilizer-containing zirconia coating or a high-purity alumina coating on the surface of a substrate selected from mullite, alumina, silicon carbide, etc. (Patent Document 2). It has also been proposed to use a firing jig with a ceramic coating layer, including a thermally sprayed coating layer with a porosity of 20% or less, on the surface of a compact containing numerous voids, primarily composed of heat-resistant inorganic fibers and refractory powder (Patent Document 3). Furthermore, it has been proposed to place a partially stabilized zirconia powder or a sheet of partially stabilized zirconia between the pre-fired compact and the firing jig (Patent Document 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-226586 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-130984 [Patent Document 3] Japanese Patent Application Publication No. 2-260602 [Patent Document 4] Patent No. 5235753 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, sintered bodies containing barium titanate, which exhibit PTC properties, have become increasingly popular in ceramic products such as heater elements. While these sintered bodies can be produced by firing a molded body containing a titanium compound and a barium compound as ceramic raw materials, they are prone to the formation of a liquid phase during firing. In particular, the amount of liquid phase generated increases as the height of the molded body from the mounting surface increases when placed on a firing jig. Therefore, while the amount of liquid phase generated is small when producing relatively thin sintered bodies, such as electronic components like capacitors, the amount of liquid phase generated becomes significantly greater when producing sintered bodies with a large height from the mounting surface, such as honeycomb structures used in heater elements. Furthermore, when the amount of liquid phase generated is large, even if a thermal spray layer or other layer is formed on the firing jig, the reaction between the firing jig and the molded body may not be sufficiently suppressed. This can result in a deterioration in the quality of the sintered body (e.g., cracking, melting, deformation, and foreign matter (such as adhesion of the firing jig material)) and deterioration of the firing jig (e.g., cracking, melting, infiltration of the liquid phase, etc.).

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide a method for producing a high-quality sintered body containing barium titanate while suppressing deterioration of the sintering jig. [Means for solving the problem]

[0007] The present inventors have conducted extensive research into the firing of a molded body containing a titanium compound and a barium compound, and as a result have found that the above-mentioned problems can be solved by firing using a specific firing jig and / or a specific bedding powder, thereby completing the present invention. That is, the present invention is exemplified as follows.

[0008] [1] A molding step of molding a clay containing a titanium compound and a barium compound as ceramic raw materials to obtain a molded body; a firing step of placing the molded body on a firing jig and firing it to obtain a fired body containing barium titanate; Including, the molded body has a portion that is 1 mm or more high from the placement surface when placed on the firing jig, The firing step is performed under the following conditions: (1) Placing a powder between the firing jig and the compact; The firing jig is made of zirconia with a porosity of 20% or more. (However, no coating film is formed on the surface of the firing jig), and the spreading powder is one or more selected from the group consisting of spreading powder composed of barium titanate, spreading powder composed of zirconia and having an average particle size of 0.5 mm or more, and spreading powder composed of yttria and having an average particle size of 0.5 mm or more. (2) Placing a powder between the firing jig and the molded body, the powder being a powder made of barium titanate. With powder be of Either A method for manufacturing a fired body that satisfies one of the requirements.

[0010] [ 2 ] The zirconia and / or the powder constituting the firing jig The method for producing a sintered body according to [1], wherein the zirconia is at least one selected from yttria-stabilized zirconia and calcia-stabilized zirconia.

[0012] [ 3 The method for producing a fired body according to [1], wherein the titanium compound is titanium oxide and the barium compound is barium carbonate.

[0013] [ 4 The method for producing a fired body according to [2], wherein the titanium compound is titanium oxide and the barium compound is barium carbonate.

[0016] [ 5The ceramic raw material is not calcined, [1] to [ 4 ] A method for producing a sintered body according to any one of the preceding items.

[0017] [ 6 The molded body has a honeycomb shape, [1] to [ 4 ] A method for producing a sintered body according to any one of the preceding items.

[0018] [ 7 The molded body has a honeycomb shape, 5 ] A method for producing the sintered body described in

[0019] [ 8 The honeycomb-shaped formed body has an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells extending from a first end face to a second end face, The length of the cell in the extension direction is 1 to 300 mm, The first end surface or the second end surface of the honeycomb-shaped molded body is placed on the firing jig; 6 ] A method for producing the sintered body described in

[0020] [ 9 The honeycomb-shaped formed body has an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells extending from a first end face to a second end face, The length of the cell in the extension direction is 1 to 300 mm, The first end surface or the second end surface of the honeycomb-shaped molded body is placed on the firing jig; 7 ] A method for producing the sintered body described in

[0021] [ 10 The honeycomb-shaped formed body has an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells extending from a first end face to a second end face, Two or more honeycomb-shaped bodies are stacked in the direction in which the cells extend, The total length of the stacked honeycomb-shaped formed bodies in the direction in which the cells extend is 5 to 300 mm, The first end face or the second end face on the non-laminated side of the honeycomb-shaped molded body is placed on the firing jig; 6 ] A method for producing the sintered body described in

[0022] [ 11 The honeycomb-shaped formed body has an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells extending from a first end face to a second end face, Two or more honeycomb-shaped bodies are stacked in the direction in which the cells extend, The total length of the stacked honeycomb-shaped formed bodies in the direction in which the cells extend is 5 to 300 mm, The first end face or the second end face on the non-laminated side of the honeycomb-shaped molded body is placed on the firing jig; 7 ] A method for producing the sintered body described in [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a method for producing a high-quality sintered body containing barium titanate while suppressing deterioration of the sintering jig. DETAILED DESCRIPTION OF THE INVENTION

[0024] A method for producing a sintered body according to an embodiment of the present invention includes a molding step of shaping a clay containing a titanium compound and a barium compound as ceramic raw materials to obtain a shaped body, and a firing step of placing the shaped body on a firing jig and firing it to obtain a sintered body containing barium titanate, the molded body has a portion that is 1 mm or more high from the placement surface when placed on the firing jig, The firing step is performed under the following conditions: (1) The firing jig is made of zirconia with a porosity of 20% or more. (2) A powder is placed between the firing jig and the compact, and the powder is one or more selected from the group consisting of a powder made of barium titanate, a powder made of zirconia, and a powder made of yttria. At least one of the following is satisfied. In particular, when firing a molded body having a portion that is 1 mm or more above the surface on which it is placed on a firing jig, a large amount of liquid phase is produced, resulting in problems such as a decrease in the quality of the fired body (e.g., cracking, melting, deformation, and foreign matter (such as adhesion of materials from the firing jig)) and deterioration of the firing jig (e.g., cracking, melting, penetration of the liquid phase). However, the method for producing a fired body according to an embodiment of the present invention can produce a high-quality fired body containing barium titanate by firing under at least one of the conditions (1) and (2) above, while suppressing deterioration of the firing jig.

[0025] The following is a detailed description of the embodiments of the present invention. The present invention is not limited to the following embodiments, and it should be understood that modifications and improvements made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention are also within the scope of the present invention.

[0026] The method for producing a sintered body according to an embodiment of the present invention includes a molding step and a sintering step.

[0027] <Forming process> The molding step is a step of molding a clay containing a titanium compound and a barium compound as ceramic raw materials to obtain a molded body. The titanium compound and barium compound are not particularly limited as long as they can produce barium titanate after firing. For example, titanium oxide can be used as the titanium compound, and barium carbonate can be used as the barium compound. The titanium compound and the barium compound are used in the form of powder, and the powders can be mixed to form a ceramic raw material. If necessary, the ceramic raw material may contain materials other than titanium compounds and barium compounds, such as, but not limited to, nitrates, oxides, or hydroxides of transition metals or rare earth elements.

[0028] As the ceramic raw material, a titanium compound and a barium compound are mixed and calcined to produce a calcined body, which is then pulverized and used as the clay. By using such a pulverized calcined body as the raw material, the amount of liquid phase generated during the firing process can be reduced, making it easier to obtain a high-quality fired body containing barium titanate while suppressing deterioration of the firing jig. However, calcining the ceramic raw material in this manner takes time and increases costs to produce the fired body. On the other hand, the method for producing a sintered body according to an embodiment of the present invention performs sintering under specific conditions, thereby suppressing deterioration of the sintering jig and producing a high-quality sintered body containing barium titanate, even if a large amount of liquid phase is generated during the sintering process. Therefore, the method for producing a sintered body according to an embodiment of the present invention can use ceramic raw materials that have not been pre-fired. By not pre-firing the ceramic raw materials, the time and cost required to produce the sintered body can be shortened.

[0029] The clay can be obtained by adding a dispersion medium, a binder, and an auxiliary to a ceramic raw material and kneading the mixture. The clay may contain additives such as a sifter, a metal oxide, a property improver, and a conductive powder, as needed.

[0030] Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as alcohol, with water being particularly preferred.

[0031] Examples of binders include organic binders such as methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, etc. One type of binder may be used alone, or two or more types may be used in combination.

[0032] Examples of the auxiliary include polyoxyalkylene alkyl ether, polycarboxylic acid polymer, alkyl phosphate ester, polyoxyalkylene alkyl ether, ethylene glycol, dextrin, fatty acid soap, polyalcohol, etc. The auxiliary may be used alone or in combination of two or more.

[0033] The shape of the molded body obtained by molding the clay is not particularly limited as long as it has a portion that is 1 mm or more high from the surface of the firing jig when placed on the firing jig. This is because a molded body with a height of less than 1 mm (for example, a sheet-like molded body with a thickness of less than 1 mm) generates a small amount of liquid phase in the firing step, and is less likely to cause problems such as a decrease in the quality of the fired body or deterioration of the firing jig.

[0034] The formed body can have, for example, a honeycomb shape. A honeycomb-shaped formed body (hereinafter, abbreviated as "honeycomb formed body") often has a large height from the mounting surface when placed on a firing jig, so by applying the method for manufacturing a fired body according to an embodiment of the present invention, it is possible to solve the problems of a decrease in the quality of the fired body and deterioration of the firing jig.

[0035] The honeycomb formed body has, for example, an outer peripheral wall and partition walls disposed inside the outer peripheral wall to define a plurality of cells extending from a first end face to a second end face, and the length in the cell extension direction is 1 to 300 mm. When this honeycomb formed body is placed on a firing jig, the first end face or the second end face is placed on the firing jig. Alternatively, two or more honeycomb formed bodies may be stacked in the cell extension direction and placed on the firing jig. In this case, the total length of the stacked honeycomb formed bodies in the cell extension direction is 5 to 300 mm. The stacked honeycomb formed bodies are placed on the firing jig with the first end face or second end face on the side that is not stacked. The honeycomb formed body may be a hollow honeycomb formed body further having an inner peripheral wall. That is, the hollow honeycomb formed body has an inner peripheral wall, an outer peripheral wall, and partition walls disposed between the inner peripheral wall and the outer peripheral wall and defining a plurality of cells extending from a first end face to a second end face.

[0036] The outer shape of the cross section of the honeycomb molded body perpendicular to the flow direction (cell extension direction) can be a polygon such as a quadrangle (rectangle, square), pentagon, hexagon, heptagon, or octagon, a circle, an oval shape (egg, ellipse, oval, rounded rectangle, etc.), etc. The end faces (first end face and second end face) have the same shape as the cross section.

[0037] The shape of the cells is not particularly limited, but may be a polygon such as a square, pentagon, hexagon, heptagon, or octagon, a circle, or an oval in a cross section perpendicular to the flow direction of the honeycomb formed body. These shapes may be used alone or in combination of two or more.

[0038] The thickness of the partition walls is not particularly limited, but is preferably 80 to 500 μm, more preferably 100 to 450 μm, and even more preferably 120 to 400 μm. Here, in this specification, the thickness of the partition wall refers to the length of a line segment that crosses the partition wall when the line segment connects the centers of gravity of adjacent cells in a cross section perpendicular to the flow path direction. The thickness of the partition wall refers to the average thickness of all the partition walls.

[0039] The thickness of the outer peripheral wall and the inner peripheral wall (if present) is not particularly limited, but is preferably 50 to 1000 μm, more preferably 60 to 800 μm, and even more preferably 80 to 600 μm. Here, in this specification, the thickness of the outer peripheral wall refers to the length from the boundary between the outer peripheral wall and the outermost cell or partition wall to the side surface of the honeycomb formed body in the normal direction of the side surface in a cross section perpendicular to the flow path direction, and the thickness of the inner peripheral wall refers to the length from the boundary between the inner peripheral wall and the innermost cell or partition wall to the inner surface of the honeycomb formed body in the normal direction of the inner peripheral surface in a cross section perpendicular to the flow path direction.

[0040] The formed body can be obtained by molding the clay by various methods. For example, a honeycomb formed body can be produced by extrusion molding the clay. During extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, etc. can be used to obtain a honeycomb formed body having a predetermined structure.

[0041] <Firing process> The firing step is a step in which the compact is placed on a firing jig and fired to obtain a fired body containing barium titanate. In the firing step, degreasing (calcination) may be carried out before firing, if necessary. The conditions for degreasing are not particularly limited and may be set appropriately depending on the type of raw material used. The firing step is carried out so as to satisfy at least one of the following conditions (1) and (2). (1) The firing jig is made of zirconia with a porosity of 20% or more. (2) A layer of powder is placed between the firing jig and the compact, and the layer of powder is one or more selected from the group consisting of a layer of barium titanate, a layer of zirconia, and a layer of yttria. By firing under at least one of the above conditions (1) and (2), it is possible to produce a high-quality fired body containing barium titanate while suppressing deterioration of the firing jig. Here, in this specification, the term "firing jig" refers to a heat-resistant jig used when firing a molded body, and examples thereof include a setter and a sagger.

[0042] Under condition (1), firing is carried out using a firing jig made of zirconia with a porosity of 20% or more. By making the porosity of the zirconia 20% or more, the liquid phase generated during the firing process can be absorbed, thereby suppressing fusion between the fired body and the firing jig, and melting and cracking of the firing jig. From the viewpoint of stably ensuring this effect, the porosity of the zirconia is preferably 21% or more. If the porosity of the zirconia is less than 20%, the liquid phase generated during the firing process may cause adhesion between the fired body and the firing jig, or the firing jig may melt and crack. The upper limit of the porosity of the zirconia is not particularly limited, but is typically 70% or less from the viewpoint of ensuring the strength of the firing jig. Here, the "porosity" of zirconia refers to the porosity measured by mercury intrusion porosimetry in accordance with JIS R1655:2003.

[0043] The zirconia used in the firing jig is not particularly limited, but is preferably partially stabilized zirconia. In this specification, the term "partially stabilized zirconia" refers to a sintered body in which a stabilizer is dissolved in zirconia. The composition of the partially stabilized zirconia is not particularly limited, but it preferably contains 75.0 to 96.5 mol % of zirconia (ZrO2) and 3.5 to 25.0 mol % of a stabilizer. Examples of the stabilizer include yttria, calcia, magnesia, scandia, ytterbia, etc. These stabilizers may be used alone or in combination of two or more. Among partially stabilized zirconias, at least one selected from yttria-stabilized zirconia using yttria as a stabilizer and calcia-stabilized zirconia using calcia as a stabilizer is preferred. By using such partially stabilized zirconia, the reaction between the molded body and the firing jig can be further suppressed, and the effect of suppressing deterioration of the quality of the fired body and the firing jig can be stably enhanced.

[0044] Condition (2) is that the firing is carried out with a predetermined powder placed between the firing jig and the compact. The firing jig used in condition (2) is not particularly limited, and any jig known in the art can be used. For example, a firing jig made of silicon carbide, alumina, zirconia, etc. can be used. Alternatively, a firing jig may be used in which zirconia, yttria, etc. is thermally sprayed onto the surface of a base material made of silicon carbide, alumina, zirconia, etc.

[0045] As the firing jig used in condition (2), it is preferable to use the firing jig made of zirconia with a porosity of 20% or more used in condition (1). Use of this firing jig can suppress the reaction between the compact and the firing jig, further enhancing the effect of suppressing deterioration of the quality of the fired body and the firing jig.

[0046] The bedding powder used in condition (2) is at least one selected from the bedding powder made of barium titanate, the bedding powder made of zirconia, and the bedding powder made of yttria. The bedding powder made of barium titanate is the same type of component as the barium titanate contained in the fired body, and therefore, by using the bedding powder made of barium titanate, it is possible to suppress deterioration of the quality of the fired body and the firing jig. The bedding powder made of barium titanate can be produced by a known method, and commercially available barium titanate powder may also be used as the bedding powder. The average particle size of the spreading powder made of barium titanate is not particularly limited, but is typically 10 nm to 100 μm. In this specification, the term "average particle size" refers to the particle size at an integrated value of 50% in the particle size distribution determined by a laser diffraction / scattering method.

[0047] The zirconia or yttria-based powder is not particularly limited, but preferably has an average particle size of 0.5 mm or more. By making the average particle size 0.5 mm or more, the liquid phase generated during the firing process can be easily discharged between the particles of the powder, thereby preventing the sintered body from fusing with the firing jig, and preventing the firing jig from melting or cracking. The shape of the zirconia or yttria-based powder is not particularly limited, and various shapes such as powder and beads can be used, but beads are preferred. By using bead-shaped powder, the liquid phase generated in the firing step can be more effectively discharged between the powder particles.

[0048] Here, in this specification, "beads" refers to granular objects such as spherical or cylindrical objects. The beads can be produced in accordance with known methods. For example, beads can be produced by granulating raw material powder. Commercially available beads may also be used. When the bead-shaped powder is used, other components (such as a binder) required for forming the bead-shaped powder may be contained in addition to zirconia or yttria.

[0049] The zirconia constituting the base powder is not particularly limited, but is preferably partially stabilized zirconia. By using partially stabilized zirconia, it is possible to suppress the reaction between the compact and the base powder. Details of partially stabilized zirconia are as described above, and therefore will not be described here.

[0050] Other conditions for the firing step are not particularly limited and may be those known in the art. For example, the firing step may be carried out by maintaining the temperature at 1360 to 1430°C for 0.5 to 10 hours. A degreasing step for removing the binder may be carried out before the firing step, and the atmosphere for the degreasing step is preferably air in order to completely decompose the organic components. The firing furnace used in the firing step and degreasing step is not particularly limited, but an electric furnace, a gas furnace, or the like can be used. [Example]

[0051] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way. Among the examples described below, Examples 1, 5 and 7 are reference examples.

[0052] BaCO3 (barium carbonate) powder, TiO2 (titanium oxide) powder, and La(OH)3 powder were prepared as ceramic raw materials. These powders were mixed to obtain a mixed powder. Next, water and methyl cellulose were added in an appropriate amount in the range of 3 to 30 parts by mass in total to 100 parts by mass of the obtained mixed powder, and kneaded to obtain a clay body by kneading, so that a ceramic molded body with a relative density of 60% or more would be obtained after extrusion molding.

[0053] Next, the obtained clay was placed in an extrusion molding machine and extruded using a specified die so that after firing it would become a honeycomb structure of the shape shown below, obtaining a honeycomb molded body with a length of 200 mm in the cell extension direction. Outline of the cross section perpendicular to the cell extension direction: Rectangle Cell shape: Cross section: Square Partition wall thickness: 300 μm Outer wall thickness: 600 μm

[0054] Next, the obtained honeycomb molded body was subjected to dielectric drying and hot air drying, and then cut to a length of 20 mm in the cell extension direction. Thereafter, the honeycomb molded body was placed on a firing jig (setter) and spread powder shown in Table 1, degreased in an air atmosphere in a firing furnace (450°C x 4 hours), and then fired in an air atmosphere at 1400°C for 5 hours to obtain a fired body (honeycomb structure). Details of the firing jig (setter) and the powder used for laying shown in Table 1 are as follows.

[0055] Setter A: A setter made of calcia-stabilized zirconia containing 3.8 mol% of calcia and 95.0 mol% of zirconia, with a porosity of 21%. Setter B: A setter made of yttria-stabilized zirconia containing 14.0 mol % yttria and 85.7 mol % zirconia, with a porosity of 0.1% or less. Setter C: Setter made of silicon carbide Setter D: A setter having a base material of 92.2 mol% alumina and 7.5 mol% silica, on the surface of which is formed a fired layer of a coating agent containing 91.2 mol% zirconia, 6.9 mol% yttria, and 0.7 mol% calcia. Setter E: A setter having a base material of 92.2 mol % alumina and 7.5 mol % silica, on the surface of which a thermal spray layer containing 90.1 mol % zirconia and 8.4 mol % yttria is formed. Setter F: A setter having a base material of 82.4 mol % alumina and 17.5 mol % silica, on the surface of which a thermal spray layer containing 99.5 mol % zirconia is formed.

[0056] Powder A: Barium titanate powder with an average particle size of 5 μm Spreading powder B: Barium titanate beads with an average particle size of 0.1 mm Spreading powder C: Yttria-stabilized zirconia beads having an average particle size of 0.5 mm and containing 4.9 mol % yttria and 94.75 mol % zirconia Spreading powder D: Yttria-stabilized zirconia beads having an average particle size of 0.1 mm and containing 4.9 mol % yttria and 94.75 mol % zirconia Spreading powder E: Yttria beads with an average particle size of 0.5 mm Spreading powder F: Yttria beads with an average particle size of 0.1 mm

[0057] Next, the state of the fired body produced through the above steps and the state of the setter used to produce the fired body were visually evaluated. The fired body was visually evaluated for cracking, melting, deformation, and adhesion of foreign matter (setter or bedding powder material). In the crack evaluation of the fired body, a sintered body in which no cracks were found was represented by an O, a sintered body in which cracks were found in an area less than 1 mm from the installation surface was represented by a △, and a sintered body in which cracks were found in an area 1 mm or more from the installation surface was represented by an X. In the evaluation of melting of the fired body, those in which melting was not observed in the fired body were represented by ◯, and those in which melting was observed in the fired body were represented by ×. In the evaluation of deformation of the fired body, a ◯ indicates that no deformation was observed in the fired body, a △ indicates that deformation was observed in an area less than 1 mm from the installation surface of the fired body, and an × indicates that deformation was observed in an area 1 mm or more from the installation surface of the fired body. In the evaluation of the adhesion of foreign matter to the fired body, the fired body in which no adhesion of foreign matter was found was represented by ◯, and the fired body in which adhesion of foreign matter was found was represented by ×.

[0058] The setter was visually evaluated for cracking, melting, and penetration of the liquid phase during firing. In the evaluation of setter cracking, a setter that did not crack was marked with ◯, a setter that cracked but did not split was marked with △, and a setter that cracked and split was marked with ×. In the evaluation of setter dissolution, the case where no dissolution of the setter was observed was represented by ◯, and the case where dissolution of the setter was observed was represented by ×. In the evaluation of liquid phase penetration into the setter, a setter that showed no liquid phase penetration was indicated by ○, a setter that showed liquid phase penetration but did not penetrate from the front surface to the back surface of the setter was indicated by △, and a setter that showed liquid phase penetration and penetrated from the front surface to the back surface of the setter was indicated by ×.

[0059] The overall evaluation of the above evaluations was made according to the following criteria. A: All setter evaluations are 〇 and all fired body evaluations are 〇 B: All setter evaluations are △ or 〇 and all fired body evaluations are 〇 C: All setter evaluations are △ or 〇 and all fired body evaluations are 〇 or △ F: One of the setter's evaluations was × or could not be evaluated The results of the above evaluations are shown in Table 1.

[0060] [Table 1]

[0061] As shown in Table 1, in Example 1, in which firing was performed using setter A made of zirconia with a porosity of 20% or more, in Examples 2 and 3, in which in addition to setter A, bedding powders A and B made of barium titanate were placed between the setter and the honeycomb formed body and firing was performed, in Examples 4 and 5, in which in addition to setter A, bedding powders C and D made of zirconia were placed between the setter and the honeycomb formed body and firing was performed, and in Examples 6 and 7, in which in addition to setter A, bedding powders E and F made of yttria were placed between the setter and the honeycomb formed body and firing was performed, the quality of the fired bodies was good and there was little damage to the setter. Note that although foreign matter was found to be attached to the fired bodies obtained in Examples 5 and 7, the foreign matter was easily removed, so it can be determined that the quality of the fired bodies was good. Furthermore, even when using a setter B made of zirconia with a porosity of less than 20%, as in Example 8, by placing a bedding powder A made of barium titanate between the setter and the honeycomb molded body and performing firing, it was possible to improve the quality of the fired body while reducing damage to the setter.

[0062] In contrast, in Comparative Example 1, firing was carried out using only setter B (without using bedding powder) made of zirconia with a porosity of less than 20%, which caused the setter to crack and split, resulting in significant damage to the setter. In Comparative Example 2, the setter C made of silicon carbide was used, and therefore the setter melted, causing significant damage to the setter. Comparative Examples 3 and 4 used setters D and E, which had a fired or sprayed coating layer formed on the surface of the substrate, and therefore the setter was heavily infiltrated with the liquid phase, causing significant damage to the setter. Comparative Example 5 also used setter F, which had a sprayed layer of coating agent formed on the surface of the substrate, and the sprayed layer peeled off, causing significant damage to the setter.

[0063] As can be seen from the above results, the present invention can provide a method for producing a high-quality sintered body containing barium titanate while suppressing deterioration of the sintering jig.

Claims

1. a molding step of molding a clay containing a titanium compound and a barium compound as ceramic raw materials to obtain a molded body; a firing step of placing the molded body on a firing jig and firing it to obtain a fired body containing barium titanate; Including, the molded body has a portion that is 1 mm or more high from a placement surface when placed on the firing jig, The firing step is carried out under the following conditions: (1) A spreading powder is placed between the firing jig and the compact, the firing jig is made of zirconia having a porosity of 20% or more (however, no coating film is formed on the surface of the firing jig), and the spreading powder is one or more selected from a spreading powder made of barium titanate, a spreading powder made of zirconia having an average particle size of 0.5 mm or more, and a spreading powder made of yttria having an average particle size of 0.5 mm or more. (2) A powder is placed between the firing jig and the molded body, and the powder is made of barium titanate. A method for producing a fired body, which satisfies any one of the above.

2. A method for producing a sintered body as described in claim 1, wherein the zirconia constituting the sintering jig and / or the zirconia constituting the bedding powder is at least one type selected from yttria-stabilized zirconia and calcia-stabilized zirconia.

3. The method for producing a fired body according to claim 1, wherein the titanium compound is titanium oxide and the barium compound is barium carbonate.

4. The method for producing a fired body according to claim 2, wherein the titanium compound is titanium oxide and the barium compound is barium carbonate.

5. The method for producing a fired body according to any one of claims 1 to 4, wherein the ceramic raw material is not calcined.

6. The method for producing a fired body according to any one of claims 1 to 4, wherein the formed body has a honeycomb shape.

7. The method for producing a fired body according to claim 5 , wherein the formed body has a honeycomb shape.

8. the honeycomb-shaped formed body has an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells extending from a first end surface to a second end surface, The length of the cell in the extension direction is 1 to 300 mm, The method for producing a fired body according to claim 6 , wherein the first end face or the second end face of the honeycomb-shaped formed body is placed on the firing jig.

9. the honeycomb-shaped formed body has an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells extending from a first end surface to a second end surface, The length of the cell in the extension direction is 1 to 300 mm, The method for producing a fired body according to claim 7 , wherein the first end face or the second end face of the honeycomb-shaped formed body is placed on the firing jig.

10. the honeycomb-shaped formed body has an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells extending from a first end surface to a second end surface, Two or more honeycomb-shaped bodies are stacked in the direction in which the cells extend, The total length of the stacked honeycomb-shaped formed bodies in the direction in which the cells extend is 5 to 300 mm, The method for producing a fired body according to claim 6 , wherein the first end face or the second end face on the non-laminated side of the honeycomb-shaped formed body is placed on the firing jig.

11. the honeycomb-shaped formed body has an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells extending from a first end surface to a second end surface, Two or more honeycomb-shaped bodies are stacked in the direction in which the cells extend, The total length of the stacked honeycomb-shaped formed bodies in the direction in which the cells extend is 5 to 300 mm, The method for producing a fired body according to claim 7 , wherein the first end face or the second end face on the non-laminated side of the honeycomb-shaped formed body is placed on the firing jig.

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