JP2016141133A - Molding die for casting, method for producing sintered compact, sintered compact and oxide target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding die for casting capable of suppressing the breakage of a molded body without sacrificing a raw material yield, a method for producing a sintered compact using the same, a sintered compact reduced in defects using the production method, and an oxide target.SOLUTION: Provided is a molding die for casting having a bottom part and side wall parts forming a slurry filling space, in which the bottom part has water absorptivity, and the slurry filling space side of the side walls is provided with a flexible layer peeled from the side wall parts after slurry filling. Also provided is a method for producing a sintered compact comprising: a molding step where the slurry filling space of the molding die for casting is filled with slurry including inorganic powder and a binder; a drying step where the molded body obtained through the molding step is discharged from the slurry filling space; and a firing step where the molded body passed through the drying step is fired.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a casting mold, a method for manufacturing a sintered body using the casting mold, a sintered body manufactured by the manufacturing method, and an oxide target formed using the sintered body About.

  A defect-free high-density ceramic molded body using an inorganic powder such as a ceramic powder is generally produced using a CIP (hydrostatic pressure press) apparatus. CIP requires a large facility, and when a rubber mold is used, near-net molding is difficult and processing loss after molding increases. On the other hand, cast molding using slurry (slurry) (hereinafter also simply referred to as “cast molding”) is known as a simple molding method.

  In casting molding, the slurry is filled in a mold having water absorbency such as a plaster mold, and a deposit layer of inorganic powder in the slurry is formed on the inner wall of the mold while dehydrating by the water absorption of the mold, and the deposit is dried in a timely manner. In this method, the layer is taken out of the mold and a molded body is obtained. General casting molding is often used when a relatively thin and compact molded body is produced because the mold is inexpensive and no special pressurizing equipment is required. However, it has been difficult to produce a relatively thick and large molded body having a high density such as that used for an oxide target by casting.

  For this reason, various proposals relating to improvements in casting are made. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 11-19910) discloses a non-liquid-absorbing type in which a molding recess is provided on the upper surface for the purpose of producing a ceramic sintered body having a high density and a uniform composition. A solid mud casting mold comprising a lower mold and a liquid-absorbing upper mold covering the upper surface of the lower mold is disclosed. Patent Document 2 (Japanese Patent Application Laid-Open No. 2011-140235) discloses a liquid-absorbing lower mold provided with a molding recess on the upper surface for the purpose of improving the production yield of molded articles and improving molding time. A mold for casting mud is disclosed, which comprises a liquid-absorbing upper mold that covers the upper surface of the lower mold, and the side formed by the side and bottom surfaces of the molding recess has a radius of curvature of a predetermined curvature. . The purpose of providing the round is to prevent cracking when the molded body is removed from the mold.

JP-A-11-19910 JP 2011-140235 A

  However, in the case of the molding die described in Patent Document 1, a thickening layer is formed on the liquid-absorbing upper mold. Therefore, when the thickening layer becomes thick and moisture decreases, May cause the mold to be removed and the molded body to be damaged. Moreover, in the case of the shaping | molding die of patent document 2, since the round shape more than necessary is formed in the edge | side of a molded object, it cannot shape | mold in a near net shape. Therefore, even if the number yield in the molding process can be improved, the processing loss for obtaining the final shape increases, and there is a problem that the raw material yield decreases.

  Accordingly, in view of the above problems, the present invention provides a mold for casting molding capable of suppressing breakage of a molded body without sacrificing raw material yield and a method for producing a sintered body using the same. With the goal. Moreover, this invention aims at providing a sintered compact with few defects, and an oxide target using this manufacturing method.

  The casting mold of the present invention has (i) a bottom portion and a side wall portion forming a slurry filling space, (ii) the bottom portion has water absorption, and (iii) the slurry filling space in the side wall portion. A flexible layer that peels off from the side wall portion after slurry filling is provided on the side.

  In the casting mold, it is preferable that the flexible layer is water-absorbing and the side wall is non-water-absorbing. Furthermore, it is preferable that the flexible layer is configured using a fibrous sheet material.

  In the casting mold, it is preferable that a water repellent layer having water repellency is provided on the side of the side wall portion facing the flexible layer. Furthermore, the water repellent layer is preferably formed using a water repellent sheet material.

  In the casting mold, it is preferable that the flexible layer is disposed apart from the bottom.

  Further, in the casting mold, the slurry filling space is configured in a polygonal column shape by a plurality of adjacent planes in the side wall portion, and the adjacent plane portion that crosses the corners of the polygonal column shape has a continuous shape. A flexible layer is preferably disposed.

The method for producing a sintered body of the present invention was obtained through a casting process in which slurry containing inorganic powder and a binder is filled in a slurry filling space of any one of the casting molds, and the casting process. It includes a drying step of taking out the molded body from the slurry filling space and drying, and a firing step of firing the molded body that has undergone the drying step.
Moreover, in the manufacturing method of the said sintered compact, it is preferable to have a preliminary baking process between the said drying process and the said baking process.

The sintered body of the present invention is a sintered body produced by any one of the above-described methods for producing a sintered body.
Furthermore, the oxide target of the present invention is formed using the sintered body.

  According to the present invention, it is possible to provide a casting mold that can suppress damage to the molded body without sacrificing the raw material yield and a method for manufacturing a sintered body using the same. Furthermore, by employing such a manufacturing method, a sintered body and an oxide target with few defects can be provided.

It is a figure which shows embodiment of the shaping | molding die for casting molding which concerns on this invention. It is a figure which shows an example of the soft layer used for the shaping | molding die for casting molding which concerns on this invention. It is a figure which shows other embodiment of the shaping | molding die for casting molding which concerns on this invention. It is a process flow figure for explaining an embodiment of a manufacturing method of a sintered compact concerning the present invention.

The casting mold according to the present invention has a bottom part and a side wall part that form a slurry filling space. Such a bottom has water absorption. Furthermore, it is one of the important features of the present invention that the side wall portion is provided with a flexible layer that is peeled off from the side wall portion after slurry filling on the slurry filling space side (inner wall side). It has a remarkable effect on the prevention of damage.
Embodiments of a casting mold, a method for manufacturing a sintered body, a sintered body, and an oxide target according to the present invention will be specifically described below. However, the present invention is not limited to this.

  FIG. 1A is a perspective view of an embodiment of a casting mold according to the present invention, and FIG. 1B is a cross-sectional view taken along line AA of FIG. The casting mold 100 has a bottom portion 2 and a side wall portion 3 that form a slurry filling space 1. The embodiment shown in FIG. 1 is an example of a molding die for a so-called single-sided inking method (also referred to as a single-sided inking method) in which the bottom 2 has water absorption. The slurry filling space 1 is a recess opened upward, and the slurry is poured into the slurry filling space 1 from above (z direction) and filled.

  The water-absorbing bottom portion 2 absorbs the moisture of the filled slurry, and the raw material powder contained in the slurry settles on the bottom portion 2. Dehydration and deposition of raw material powder proceed to form a molded body in which the raw material powder is solidified. In addition to the property of absorbing and transmitting water, the water-absorbing bottom portion 2 is preferably made of a material having hardness and strength capable of maintaining a constant shape while supporting a heavy molded body. For example, gypsum, porous metal, and the like can be used. Of these, gypsum is preferable because it is inexpensive.

  On the other hand, the side wall part 3 demarcates the external shape and outline of a molded object. Therefore, the side wall part 3 has the intensity | strength which can maintain a predetermined shape also at the time of slurry filling. A flexible sheet 4 is provided on the side of the side wall 3 where the slurry is filled. Such a flexible sheet 4 is an example of a flexible layer in the present invention.

  As moisture is removed from the molded body and dried, the molded body tends to shrink. Therefore, for example, in the conventional method in which the side wall portion is composed only of a hard resin having poor deformability, the molded body is chipped due to friction and sliding with the inner wall of the side wall portion during drying shrinkage, and damage such as cracks Is likely to occur. On the other hand, the flexible sheet 4 not only has flexibility, but is not fixed to the side wall portion 3 at the time of casting, and therefore easily follows the shrinkage of the molded body in the course of slurry filling, solidification, and drying. Has properties. Since the flexible sheet 4 is flexible and has a weak force to constrain the surface of the molded body, chipping and cracking of the molded body can be suppressed even when the molded body shrinks due to drying.

  In addition, since the flexible sheet 4 is peeled off from the side wall portion 3 after filling with the slurry, it is possible to prevent chipping and the like from occurring when the molded body is taken out from the mold after drying. For the purpose of preventing chipping, it is not necessary to provide a rounded corner at the corner of the mold, so that a near net shape can be formed and the material yield is improved.

  After the slurry is filled, the flexible sheet 4 is peeled off from the side wall 3 when the molded body is taken out or before that. The form in which the flexible sheet 4 is peeled from the side wall part 3 is, for example, a form in which the flexible sheet 4 is peeled off while being attached to the molded body side, or a form in which the flexible sheet 4 is peeled from both the side wall part 3 and the molded body. is there. When the flexible sheet is light enough to stick to the molded body when the molded body is taken out, the former form is used. On the other hand, when the flexible sheet 4 is peeled from the molded body during the drying shrinkage, the latter form is obtained. In this case, the flexible sheet 4 may be in contact with the side wall part 3, but if there is no fixing force, it is considered that this form is also peeled off. Even if the side wall 3 has such a high strength that it does not follow the dry shrinkage of the molded body, peeling occurs between the flexible sheet 4 and the side wall 3, so that the side wall 3 does not cause the dry shrinkage of the molded body. Direct inhibition can be prevented.

  Since the flexible sheet 4 is deformed following the drying shrinkage of the molded body, the function of maintaining the shape of the slurry filling space during the casting is not exhibited by the flexible sheet 4 alone. The side wall has the function of maintaining the shape. Therefore, for example, when the sheet is placed upright, even if the flexible sheet cannot stand by itself while maintaining the planar shape, the slurry filling space is secured by combining with the side wall.

  The configuration of the flexible layer is not particularly limited as long as it exhibits the functions according to the present invention, such as the functions related to peeling. Either a water-absorbing (water-permeable) material or a non-water-absorbing (non-water-permeable) material can be used. More specifically, for example, a non-water-absorbing material may be a resin film such as a wrap, and a water-absorbing material may be a woven fabric / non-woven fabric, a fiber sheet such as paper, a sponge, or the like. .

  When a water-absorbing material is used as the flexible layer, there are the following advantages. Since the flexible layer having water absorption also has air permeability, the peelability after forming the molded body is high. Further, since the slurry contains a binder, the adhesion force between the flexible layer and the molded body when the molded body is taken out may increase. On the other hand, a soft layer can be easily peeled from a molded object by absorbing a small amount of moisture from the outside of the soft layer.

  As the flexible layer having water absorption, a fiber sheet, particularly paper, is easy to use from the viewpoint of processability and the like, which is preferable. Even when a fiber sheet such as paper is used, a thickness capable of ensuring flexibility such as being easily deformed by its own weight is selected. For example, if paper or a resin sheet is used, a thickness of 0.5 mm or less is suitable. The thickness of the paper is more preferably 0.1 mm or less. Paper is one of materials that can be regarded as an inelastic material, and is preferable because tensile stress in the direction opposite to drying shrinkage, which causes chipping and cracking, does not substantially work.

  When a water-absorbing material is used as the flexible layer, the side wall portion is preferably non-water-absorbing. This is because if the side wall portion has the same dehydration function as the bottom portion, the adhesion between the flexible layer and the molded body may be too strong, or the slurry may reach the side wall portion side and solidify. It is. Even if the flexible layer functions as a water-absorbing layer, the effects of dehydration and raw material powder deposition on the flexible layer alone are very limited. Further, since the outer side of the flexible layer is covered with a non-water-absorbing side wall, the water absorption on the side of the slurry filling space is limited, unlike the bottom that actively absorbs and dehydrates. Therefore, if the side wall portion is non-water-absorbing, the flexible layer and the molded body are gently fixed, so that the molded body can be prevented from being damaged even when the flexible layer is peeled off from the molded body during or after drying. The As the non-water-absorbing material that does not absorb / permeate water, resin materials such as acrylic resin and vinyl chloride resin, metal materials such as stainless steel and brass, glass, and the like can be used. Among these, a resin material is preferable from the viewpoint of cost and ease of handling.

  On the other hand, when a non-water-absorbing material is used as the soft layer, whether the side wall portion is water-absorbing or non-water-absorbing does not affect chipping or cracks in the molded body. Therefore, the water-absorbing side wall can be used in the same manner as the non-water-absorbing side wall. That is, plaster etc. can be used in addition to the above-mentioned resin materials such as acrylic resin and vinyl chloride resin, metal materials such as stainless steel and brass, glass and the like. It is also possible to use the same material as the bottom.

  As described above, as the moisture is removed from the molded body and dried, the molded body tends to shrink. Therefore, in the conventional method in which water is actively dehydrated also from the side wall portion side, the molded body is easily chipped due to friction and sliding with the inner wall of the side wall portion during drying shrinkage, and damage such as cracks is likely to occur. On the other hand, by giving non-water absorption to the side wall or the flexible sheet as described above, it is possible to more effectively suppress chipping of the molded body.

  In the embodiment shown in FIG. 1, the slurry filling space 1 has a rectangular parallelepiped shape in order to obtain a plate-shaped molded body, but the shape of the slurry filling space 1 is not limited to this. For example, a slurry filling space in which the shape of the bottom portion 2 is a polygonal columnar shape other than a rectangular shape or a cylindrical shape can be configured. In the embodiment shown in FIG. 1, the inner wall of the side wall 3 is perpendicular to the bottom 2, but the inner wall of the side wall is inclined when there is little processing loss, such as when the side surface of the final product is inclined. You may do it.

  In the embodiment shown in FIG. 1, a molding die is configured by placing a rectangular frame-shaped side wall 3 on a base 5 made of gypsum board or the like that is larger than the projected shape. A portion of the base 5 exposed to the inside of the frame-shaped side wall 3 constitutes the bottom 2. Although it is possible to form the mold by inserting the base into the inside of the frame-shaped side wall, a configuration in which the frame-shaped side wall is placed on the base 5 as shown in FIG. 1 is preferable. . The rectangular frame-shaped side wall 3 may be integrally formed by bonding with an adhesive or the like, or may be formed by combining a plurality of members. In the embodiment shown in FIG. 1, the frame-shaped side wall 3 includes a pair of rectangular parallelepiped members 3 a that are arranged in parallel and a pair of rectangular parallelepiped members 3 b that are arranged in parallel so as to be sandwiched from both ends of the member 3 a. It consists of and. The four members constituting each side of the rectangle are not bonded, but the periphery is temporarily fixed by band fastening (not shown). The fixing method is not limited to band tightening, and fixing methods such as screwing, fitting, and clamping can also be adopted. If the plurality of members are temporarily fixed to form the side wall portion, the molded body can be taken out by removing the members to the side, so that the possibility of damaging the molded body is reduced.

  In the embodiment shown in FIG. 1, the flexible sheet 4 arranged along the inner wall of the side wall portion 3 has a rectangular frame shape as a whole. The flexible sheet 4 may be configured as a single unit or may be configured by a plurality of sheet members. In order not to inhibit the drying shrinkage, the flexible sheet is preferably composed of a plurality of sheet members, and more preferably composed of a number of sheet members equal to or more than the number of side walls. preferable.

  In the case where the slurry filling space has a polygonal column shape such as a quadrangular columnar shape constituted by a plurality of adjacent planes on the side wall portion, a continuous flexible sheet or the like is provided on the adjacent plane portion across the corner of the polygonal column shape. It is preferable that the flexible layer is disposed. In other words, it is preferable that a flexible layer such as a flexible sheet, which is continuous over two planes constituting the corner portion, is disposed on the side wall portion constituting the corner portion of the polygonal column shape of the slurry filling space. If a flexible layer is arranged for each plane of the side wall part, and the joint of such a flexible layer is arranged at the corner part, the slurry is likely to leak from the corner part, and a minute chipping is likely to occur at the corner part of the molded body. is there. On the other hand, by arranging a flexible layer such as a continuous flexible sheet in the portion of the adjacent plane crossing the corner so that the joint of the flexible layer is not arranged at the corner, such a minute chip is prevented. be able to.

  An example of a flexible layer such as such a flexible sheet is shown in FIG. The sheet member 4a shown in FIG. 2 has an L shape when viewed from above (z direction). The sheet member itself may hold an L shape by bending the sheet member, or an L shape may be formed as a result of the sheet member being brought into close contact with the side wall portion.

  By using four L-shaped sheet members, a rectangular frame-shaped flexible layer can be formed. It can also arrange | position so that the edge parts of a sheet | seat member may contact | connect, and a part of sheet | seat member can also be arrange | positioned. It is also possible to configure a frame-like flexible layer by combining an L-shaped sheet member and a planar sheet member.

  The bonding relationship between the flexible sheet 4 and the side wall portion 3 at the stage before filling with the slurry is not limited to this. The flexible sheet 4 should just peel from the side wall part 3 as a result after slurry filling. For example, the flexible sheet 4 may be in a state of being simply disposed along the side wall portion 3, that is, in a free state with respect to the side wall portion 3, or in a state of being attached to the side wall portion 3. . An example of the latter is a state in which a flexible sheet (flexible layer) is adsorbed on the side wall through moisture, for example. Both are included in the form in which the flexible sheet (flexible layer) peels from the side wall after the slurry is filled. Further, even if the flexible sheet (flexible layer) is fixed to the side wall before the slurry is filled, a form in which the fixation is released simultaneously with the slurry filling is also applicable. Such a form is, for example, a form in which the flexible sheet (flexible layer) is bonded with a substance that absorbs moisture of the slurry and loses its adhesive strength.

  If the upper end of the flexible layer is above the upper surface of the filled slurry, the height dimension of the flexible layer is not particularly limited. If the upper end of the flexible sheet 4 is configured to be lower than the upper end of the side wall portion 3 as in the embodiment shown in FIG. 1, the flexible sheet (contacts the flexible layer unintentionally during operation). This is because if the flexible sheet protrudes from the side wall part, the flexible sheet may move by touching a person or an object during the work.The flexible sheet (the flexible layer and the upper end of the side wall part are aligned. However, the embodiment shown in FIG. 1 is easier to manufacture.

  As arrangement | positioning of the flexible sheet | seat 4 in the depth direction (z direction) in slurry filling space, arrangement | positioning which contacts the bottom part 2 as shown in FIG.1 (b) is simple. On the other hand, as shown in FIG.1 (c), the structure which spaces apart the edge of the flexible sheet | seat 4 from the bottom part 2, and the slurry filled only in this part can contact a side wall part directly is also possible. Such a configuration has the following advantages. In some cases, the binder component contained in the slurry accumulates along the flexible sheet 4. In particular, when such a binder component is transferred to the bottom 2 side through the flexible sheet 4, the solidified molded body and the bottom 2 are firmly fixed. As a result, when the molded body is taken out, the bottom 2 side of the molded body is removed. Chipping may occur.

  On the other hand, as shown in FIG. 1 (c), by arranging the end of the flexible sheet 4 away from the bottom 2, the binder component is transferred to the flexible sheet and accumulated near the bottom 2. Can be prevented. Although the molded body and the side wall portion come into contact with each other at the separation portion between the flexible sheet 4 and the bottom portion 2, the fixing between the molded body and the side wall portion includes the binding force due to the concentrated binder component. Since it is much weaker than the adhesion between the molded body and the bottom, it contributes to the reduction of chipping.

  FIG. 3 shows another embodiment of a casting mold. FIG. 3 shows a cross-sectional view of a casting mold as in FIG. In the casting mold 200, the water-repellent sheet 6 is disposed on the surface (inner wall) of the side wall 3 facing the flexible sheet 4. By disposing the water repellent sheet and imparting water repellency to the side wall portion 3, friction between the flexible sheet 4 and the side wall portion 3 is reduced, and the flexible sheet 4 can be easily peeled from the side wall portion 3. The water-repellent sheet 6 is preferably a fluororesin sheet such as PTFE (polytetrafluoroethylene).

  The method of imparting water repellency to the surface (inner wall) of the side wall 3 that faces the flexible sheet 4 is not limited to the use of the above water-repellent sheet. The side wall 3 itself may be made of a water repellent material (for example, the above PTFE), or a water repellent coating may be provided on the inner wall of the side wall 3. However, it is convenient and preferable to use the water-repellent sheet shown in FIG.

  Next, an embodiment of a method for producing a sintered body according to the present invention using the above-described casting mold will be described. The sintered body is, for example, oxide sintered such as indium tin complex oxide (ITO), zinc tin complex oxide (ZTO), indium zinc tin complex oxide (IZTO), indium gallium zinc complex oxide (IGZO). Bodies, nitride sintered bodies such as silicon nitride, and metal powder sintered bodies such as Mo, Ni and Ti.

  Fig.4 (a) is the flow of the process for demonstrating the manufacturing method of a sintered compact. The manufacturing method shown in FIG. 4 is a molding process obtained by filling a slurry-filling space of any of the above-described molding molds with an inorganic powder and a slurry containing a binder, and the molding process obtained through the casting process. A drying step of taking out the body from the slurry filling space and drying, and a firing step of firing the molded body that has undergone the drying step are included.

  First, the casting process will be described. Since the casting mold is as described above, description thereof is omitted. The slurry contains, in water as a solvent, inorganic powder that is a raw material of the sintered body, and a binder that binds the inorganic powder to each other in the molded body. As the inorganic powder, for example, ceramic powders such as oxides and nitrides, metal powders, and the like, which are raw materials for the oxide sintered body, can be used. Hereinafter, an oxide sintered body is assumed as a sintered body, and an oxide powder that is a raw material powder is assumed as an inorganic powder. The oxide powder can be used in the form of a mixed powder of raw material oxides. However, from the viewpoint of improving homogeneity and reducing the amount of shrinkage during sintering, it is preferable to use oxide powder obtained by calcining and pulverizing the raw material oxide for casting. Conditions for obtaining the pulverized oxide powder, such as calcination conditions, may be determined according to the type of the oxide sintered body.

The particle size, slurry concentration (solid content concentration), and the like of the inorganic powder to be used are not particularly limited. For example, the specific surface area of the inorganic powder is 1 to 50 m ² / g as a BET value, and the slurry concentration is 30 to 30%. What is necessary is just to adjust in the range of 90 mass%. The adjusted slurry is poured into the slurry filling space and dehydrated over a predetermined time. The dehydration time is, for example, about 5 to 50 hours, although it depends on the particle size of the inorganic powder, the slurry concentration, and the molded body thickness.

  In the casting process, the slurry filled in the slurry filling space is dehydrated and solidified to a strength that can be handled to obtain a molded body. The molded body obtained through the casting process is taken out from the slurry filling space and dried. The flexible layer may be peeled off from the molded body during the drying process in the slurry filling space, or may be stuck to the molded body when the molded body is taken out from the slurry filled space. In the latter case, the flexible layer may be peeled off before being subjected to the drying step, or the molded body may be subjected to the drying step while the flexible layer is adhered. Even when the flexible layer is peeled off, since the binding force between the flexible layer and the molded body is weak, the flexible layer can be easily peeled without damaging the molded body. Further, when the flexible layer is fixed to the molded body, the absorption layer can be more easily separated by absorbing a small amount of moisture from the outside.

  In the drying step, it is preferable to heat the molded body in order to remove residual moisture. However, since rapid heating to a high temperature may cause cracks in the molded article, the heating temperature is preferably 35 ° C to 80 ° C. In addition, it is also possible to use the molded body drying in a state where the slurry is contained in the slurry filling space. Although the molded body is naturally dried even when it is in the slurry filling space, drying can be promoted by heating in this state.

  In order to increase the relative density of the final sintered body, it is preferable to increase the relative density of the molded body as much as possible when the drying step is completed. This is particularly important in the case of materials where the sintering temperature cannot be raised or difficult to sinter. For example, in the case of a zinc-tin composite oxide sintered body (ZTO sintered body), it is preferable to increase the relative density of the molded body to 60% or more when the drying step is completed.

  The molded body that has undergone the above-described drying step is subjected to a firing step. The firing temperature and atmosphere are determined by the type and composition of the material used. For example, in the case of the above-described zinc-tin composite oxide sintered body (ZTO sintered body), the firing temperature is preferably in the range of 1450 to 1600 ° C. The binder contained in the molded body can be removed by a binder removal pattern incorporated in the temperature raising process of the firing process. In such a case, firing and binder removal can be performed in the same furnace.

  On the other hand, as shown in FIG.4 (b), the prebaking process is integrated between a drying process and a baking process, and the intensity | strength which can be handled can be provided to a prebaking body through the said prebaking process. In such a case, binder removal and firing can be performed in separate furnaces, so that the degree of freedom of operation in the sintering process is improved. The pre-baking temperature is preferably 800 ° C. or higher, for example. Note that the preliminary firing step is performed at a temperature lower than that of the firing step for the purpose. Further, when a pre-baking step is provided before the baking step, it is possible to select an atmosphere in the furnace, for example, pre-baking is performed in the air and subsequent baking is performed in nitrogen.

  The sintered body of the present invention is a sintered body produced by any one of the above-described methods for producing a sintered body. The kind of the sintered body is not limited to this. As described above, the sintered body is, for example, indium tin composite oxide (ITO), zinc tin composite oxide (ZTO), indium zinc tin composite oxide (IZTO), indium gallium zinc composite oxide (IGZO), or the like. An oxide sintered body, a nitride sintered body such as silicon nitride, and a metal powder sintered body such as Mo, Ni, and Ti.

Since the method for producing a sintered body according to the present invention is suitable for producing a large-area sintered body, an oxide target using the sintered body is particularly suitable as an application of the sintered body. The oxide target is used, for example, for forming a semiconductor film or an electrode film. The sintered body obtained through the firing step is appropriately processed to obtain an oxide target. For example, in the case of a rectangular parallelepiped, an oxide target having a size of 300 mm or more, 200 mm or more, and a thickness of 10 mm or more can be realized with one sintered body. Furthermore, it is possible to obtain a sintered body having an area of the main surface (the surface having the largest area) of 1 m ² or more. According to such a configuration, an oxide target superior in quality and cost can be realized while responding to the demand for an increase in size without using an expensive press apparatus having a high pressure.

(Invention Example 1)
A sintered body of a zinc-tin composite oxide for an oxide semiconductor target was produced by the following procedure. The raw material powder of zinc tin composite oxide (ZTO) was calcined and pulverized to obtain an inorganic powder for slurry. The specific surface area of the obtained inorganic powder was 2.2 m ² / g. This inorganic powder is mixed with water and a binder (type: Chukyo Yushi Seruna WN-405, added amount: 1 part by mass with respect to 100 parts by mass of the inorganic powder) to obtain a slurry having a solid content concentration of 82% by mass. Produced. The obtained slurry was poured into a slurry filling space of a molding die having the configuration shown in FIG. 3 and allowed to stand for 40 hours for casting.

  The configuration of the mold is as follows. A rectangular frame-shaped side wall made of a vinyl chloride resin was placed on a gypsum base. A high-quality copy sheet having a thickness of 0.09 mm was disposed as a flexible sheet (flexible layer) through a water-repellent sheet (water-repellent layer) made of polytetrafluoroethylene on the side of the slurry filling space on the side wall. The high-quality copy paper was composed of a plurality of sheet members bent in an L shape, and the bent portions were arranged in accordance with the corners of the side walls. The water-repellent sheet was fixed to the inside of the side wall portion with an adhesive, while the flexible sheet was wetted with water and separated from the bottom by 1 mm, and was placed in a state of adhering to the water-repellent sheet. The slurry filling space was 314 mm wide, 235 mm long and 50 mm high, and the thickness of the molded body was about 20 mm.

  The molded body obtained through the casting process was taken out from the slurry filling space and dried under the conditions of 40 ° C. and 40 hours. The relative density of the molded body at the time when the drying process was completed was 70%. The formed body that had undergone the drying step was pre-fired at 1000 ° C. and then fired in a nitrogen atmosphere at 1550 ° C. for 4 hours to obtain a sintered body having a width of 282 mm, a length of 210 mm, and a thickness of 18 mm.

(Invention Example 2)
A sintered body of zinc-tin composite oxide was produced in the same manner as in Example 1 except that the flexible sheet was placed in contact with the bottom.

(Invention Example 3)
A sintered body of zinc-tin composite oxide was produced in the same manner as Example 1 except that the water-repellent sheet was not disposed between the side wall portion and the flexible sheet.

(Invention Example 4)
Zinc was formed in the same manner as in Example 1 except that the flexible sheet (high-quality copy paper) was composed of four planar sheet members matched to the inner wall size of the side wall and arranged on the inner wall of the side wall. A sintered body of a tin composite oxide was produced. That is, as the flexible sheet, there was adopted a configuration in which there are discontinuities in the flexible sheet at the four corners of the slurry filling space, and the flexible sheet is discontinuous.

(Comparative example)
For comparison, a sintered body was obtained in the same manner as in Invention Example 1 except that no flexible sheet was disposed.

  Table 1 shows the results of confirming breakage such as chipping and cracking in the state of the molded body taken out from the slurry filling space and the state of the sintered body after firing for the inventive example and the comparative example.

  As shown in Table 1, in the comparative example, large chippings of 10 mm or more were generated at the four corners of the molded body. In the present invention examples 1 to 4 using a mold in which paper is arranged as a flexible sheet on the side of the slurry filling space of the side wall portion, chipping at the four corners of the molded body generated in the comparative example is not observed, and is good. A molded body having an appearance was obtained. In addition, chipping and crack defects could not be confirmed even after firing, and a good sintered body was obtained.

  In Example 2 of the present invention, micro-chips on the bottom side that were not problematic for practical use were confirmed. However, in Example 1 of the present invention in which the flexible sheet was arranged apart from the bottom, such micro-chips were also suppressed. Was confirmed. Further, in the present invention example 1 in which the surface of the side wall portion facing the flexible sheet is water repellent, the flexible sheet is smoothly peeled from the side wall portion as compared to the present invention example 3 that does not have such water repellency. It was. Furthermore, in the present invention example 4 in which the flexible sheet is configured by four planar sheet members, a minute chipping of a practically no problem was confirmed in the slurry filling space corner portion, but a plurality of bent in an L shape In Invention Example 1 in which the flexible sheet is formed of the sheet member, it was confirmed that such minute chipping was suppressed.

1: Slurry filling space, 2: Bottom, 3: Side wall, 3a: Member, 3b: Member, 4: Flexible sheet, 4a: Sheet member, 5: Base, 6: Water repellent sheet, 100: For casting Mold, 200: Mold for casting

Claims (11)

Having a bottom and sidewalls forming a slurry-filled space;
The bottom has water absorption;
A mold for casting molding, comprising a flexible layer that is peeled off from the side wall portion after slurry filling on the side of the side wall of the slurry filling space.   The mold for casting molding according to claim 1, wherein the flexible layer is water-absorbing and the side wall is non-water-absorbing.   The mold for casting molding according to claim 2, wherein the flexible layer is configured using a fibrous sheet material.   The mold for casting molding according to claim 2 or 3, comprising a water-repellent water-repellent layer on a side of the side wall portion facing the flexible layer.   The mold for casting molding according to claim 4, wherein the water-repellent layer is formed using a water-repellent sheet material.   The mold for casting molding according to any one of claims 1 to 5, wherein the flexible layer is disposed apart from the bottom portion. The slurry filling space is configured in a polygonal column shape by a plurality of adjacent planes on the side wall portion,
The mold for casting molding according to any one of claims 1 to 6, wherein the continuous flexible layer is disposed in a portion of the adjacent plane that crosses the corner of the polygonal column shape. A casting molding step of filling a slurry-filling space of the molding die for casting molding according to any one of claims 1 to 7 with a slurry containing an inorganic powder and a binder,
A drying step of taking out the molded body obtained through the casting molding step from the slurry filling space and drying;
And a firing step of firing the molded body that has undergone the drying step.   The manufacturing method of the sintered compact of Claim 8 which has a preliminary baking process between the said drying process and the said baking process.   The sintered compact manufactured by the manufacturing method of the sintered compact of Claim 8 or 9.   The oxide target formed using the sintered compact of Claim 10.