JP2010090005A - Setter for firing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a setter for firing which controls the lowering of the performance of objects such as piezoelectric ceramics and the deterioration of the setting table. <P>SOLUTION: The setter for firing is provided with a ceramic fired body having a setting plate 10 on which objects 100 formed of ceramic shaped bodies to be fired. The base material of the ceramic fired body is cerium oxide. The cerium oxide has small reactivity with the objects placed on the setting plate 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a setter for firing that is used when an object such as a ceramic-based electronic material component is placed and fired.

The prior art will be described by taking the firing of piezoelectric ceramics as an example. Piezoelectric ceramics using PZT (PbZrTiO ₃ ) or the like as a raw material are formed as follows. That is, the raw material powder is molded to form an object made of an unfired ceramic molded body, and the unfired object is placed on the placement surface of the firing setter. And the piezoelectric ceramic is manufactured by charging the setter for baking which mounted the target object in a baking furnace, and heating and hold | maintaining for a predetermined time at baking temperature (for example, 800-1400 degreeC). The firing setter described above is formed of a fired ceramic body having a mounting surface on which an object made of an unfired ceramic molded body is placed.

  In the industry, when firing the above-mentioned target piezoelectric ceramics, the firing temperature at which the piezoelectric ceramics are fired is quite high, so diffusion and reaction between the target piezoelectric ceramics and the setter mounting surface. May occur. In this case, there is a possibility that the performance of the piezoelectric ceramic that is the object is lowered. Furthermore, the setting surface of the setter may be deteriorated.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a firing setter that can suppress a decrease in performance of an object such as piezoelectric ceramics and can also suppress deterioration of a mounting surface.

  A setter for firing according to the present invention is a setter for firing provided with a ceramic fired body having a mounting surface on which an object formed of an unfired or semi-fired ceramic molded body to be fired is placed. The base material is cerium oxide. Cerium oxide has little chemical reactivity with the object mounted on the mounting surface. In particular, in an oxidizing atmosphere, there is little chemical reactivity with the object mounted on the mounting surface.

  Since cerium oxide is used as a base material, the reactivity with the mounting surface of the setter with an object such as piezoelectric ceramics is reduced. Furthermore, deterioration on the mounting surface of the setter can also be suppressed.

Cerium oxide has a melting point of 1950 ° C. or higher, is chemically stable, and is extremely stable even in an oxidizing atmosphere. Furthermore, the hardness is high. The cerium oxide is CeO ₂ , but Ce ₂ O ₃ may be contained. Here, when the cerium oxide is 100 mol%, CeO ₂ can be 90% or more, 95% or more, or 98% or more. When the entire setter is 100% by mass, the cerium oxide (CeO ₂ ) can be 80 to 100% by molar ratio. In a molar _{ratio, Al 2 O 3, Cr 2} O 3, Fe 3 O 4, CaO, MgO, Mn 3 O 4, La 2 O 3, Nd 2 O 3, SiO 2, B 2 O 3, ZrO 2, TiO ₂ , at least one of Y ₂ O ₃ may be contained in an amount of 0.1 to 30%. In this case, the above-described compound is expected to serve as a sintering aid, and the setter sinterability is ensured.

When the entire setter is 100% by mass, the cerium oxide (CeO ₂ ) can be 85 to 98% and 90 to 95% in molar ratio. In this case, Al ₂ O ₃ , Cr ₂ O ₃ , Fe ₃ O ₄ , CaO, MgO, Mn ₃ O ₄ , La ₂ O ₃ , Nd ₂ O are used in molar ratios depending on the properties required for the setter. ₃ , SiO ₂ , B ₂ O ₃ , ZrO ₂ , TiO ₂ , Y ₂ O ₃ with an upper limit of 25%, 20%, 15%, 10%, 5%, 3%, 2% Can be included.

  When the average crystal grain size on the placement surface is fine, the frequency of occurrence of crystal grain boundaries increases, and the exposed area and / or the probability of appearing of the crystal grain boundaries on the placement surface increases. Since the crystal grain boundary often has a composition other than cerium oxide, the reaction with the target object is promoted, and the components of the crystal grain boundary may diffuse into the target object, thereby reducing the original performance of the target object. is there. Here, the average crystal grain size on the mounting surface can be in the range of 10 to 300 micrometers. It can be in the range of 20-200 micrometers and in the range of 30-100 micrometers. Or it can be in the range of 50-300 micrometers, the range of 50-200 micrometers, and the range of 50-100 micrometers.

  Here, examples of the upper limit value of the average crystal grain size on the mounting surface include 300 micrometers, 200 micrometers, 100 micrometers, and 50 micrometers. Examples of the lower limit value of the average crystal grain size that can be combined with any of the above upper limit values include 10 micrometers, 20 micrometers, 30 micrometers, 40 micrometers, and 50 micrometers. The average crystal grain size can be adjusted by the composition of the starting material, the crystal grain size of the starting material, the firing temperature, and the like.

  The object to be placed on the placement surface may be oxide-based, nitride-based, carbide-based, or boride-based. The atmosphere at the time of firing the object can be appropriately washed, and examples include an oxidizing atmosphere, a non-oxidizing atmosphere, and a vacuum atmosphere, but an oxidizing atmosphere is preferable.

Embodiment 1 of the present invention will be described below with reference to FIG. The firing setter is a ceramic fired body having a flat plate shape having a placement surface 10 on which an object 100 formed of a ceramic molded body to be fired is placed and a back surface 12 facing away from the placement surface 10. The base material has a thickness in the range of 1 to 3 millimeters. The mounting surface 10 and the back surface 12 have a flat planar shape and are parallel to each other. The setter 1 has a projecting engagement portion 2 that can be stacked. Using the projecting engagement portion 2, the setter 1 can be stacked in multiple stages by placing the object 100 on the placement surface 10. The setter 1 uses cerium oxide (CeO ₂ ) as a base material, and the firing temperature when the setter compacted body is fired to form a setter sintered body is 1400 to 1600 ° C., particularly 1450 to 1550 ° C. When the entire setter 1 is 100% by mass, the cerium oxide (CeO ₂ ) is 99.90% or more by molar ratio. The mounting surface 10 and the back surface 12 are polished surfaces, but may be natural surfaces that are not polished.

  When the average crystal grain size on the mounting surface 10 is fine, the exposed area and / or the exposure probability that the crystal grain boundary appears on the mounting surface 10 increases. Since the crystal grain boundary often has a composition other than cerium oxide, the reaction with the target object 100 is promoted, the components of the crystal grain boundary diffuse into the target object, and the original performance of the target object 100 is reduced. There is a fear. Therefore, the average crystal grain size on the mounting surface 10 is set within a range of 10 to 300 micrometers. In particular, it is set within the range of 10 to 200 micrometers and within the range of 30 to 100 micrometers. Here, although the upper limit value of the average crystal grain size on the mounting surface 10 is different depending on the use of the setter 1, etc., 300 micrometers and 200 micrometers are exemplified, and 100 micrometers and 50 micrometers are exemplified. . Examples of the lower limit of the average crystal grain size that can be combined with the above upper limit include 10 micrometers, 20 micrometers, 30 micrometers, 40 micrometers, and 50 micrometers. The average crystal grain size can be adjusted by the crystal grain size of the starting material, the firing temperature, and the like.

  As shown in FIG. 2, the average crystal grain size is defined as one diagonal line in an electron micrograph (SEM), the length of the diagonal line is L micrometers, and the number of particles passing through the diagonal line is defined as follows. When N, L / N was determined as an average crystal grain size micrometer.

  When used, a firing furnace in an air atmosphere (oxidizing atmosphere) in a state where an object 100 formed of an unfired ceramic molded body (PZT or the like) that is fired is placed on the mounting surface 10 of the setter 1 The object 100 is fired.

(Test example)
A description will be given of test examples. First, 99.9 parts by mass of a cerium oxide (CeO ₂ ) powder, 1 part by mass of a dispersant (polycarboxylic acid type), 1 part by mass of an organic binder (PVA), and a solvent (distillation) Water) 20 parts by mass were prepared. These were kneaded by a ball mill for a predetermined time (6 hours) to form a slurry as a kneaded product. In this case, 1/3 of the mill capacity was used for the grinding balls.

Next, a spray dryer was used as a drier, granulation was performed at a slurry supply rate of 1 liter / hour, an atomizer speed of 10,000 rpm, an inlet temperature of heated air of 150 ° C., and an outlet temperature of heated air of 90 ° C. The granulated size averaged 50 micrometers. Next, the granulated particles are put into a mold cavity and pressed at room temperature (1 tonf / cm ² ) to form a plate-like compact (size: 130 mm × 130 mm × 2 mm). Formed. In this case, the projected shape of the mold cavity is 120 mm × 120 mm.

  Next, in an air atmosphere, the compacted body was degreased at a temperature of 20 ° C./hour from room temperature to 500 ° C. to remove the binder. Next, in an air atmosphere, the compacted body was heated to 500-1500 ° C. at 50 ° C./hour. Thereafter, the compacted body was heated and held at 1500 ° C. for 2 hours in an oxidizing atmosphere and fired to form a fired body. Thereafter, the fired body was cooled to near room temperature at 100 ° C./hour. The average crystal grain size on the mounting surface 10 of the setter 1 was in the range of 10 to 50 micrometers.

Furthermore, as a comparative example, a setter 1 having a base material of zirconia (PSZ), which has been considered to have higher chemical stability than before, was formed. About the setter 1 which concerns on Example 1, and the setter 1 which concerns on a comparative example, the reactivity of the setter 1 and the target object 100 in a high temperature area | region was measured. In the comparative example, the average crystal grain size on the mounting surface 10 of zirconia (PSZ) was 1 micrometer. Then, PZT is used as the target object 100, and the target object 100 (piezoelectric ceramics) is heated at 1000 to 1200 ° C. for 5 hours in a state where the target object 100 is mounted on the mounting surface 10 of the setter 1 in an air atmosphere firing furnace. And fired. In Example 1, even when the number of firings of the object 100 (piezoelectric ceramics) exceeded 10, the color of the mounting surface 10 of the setter 1 was not changed. On the other hand, in the comparative example, when the number of firings exceeded 10, the color change of the mounting surface 10 of the setter 1 was recognized. Thereby, it turns out that the setter 1 which concerns on a present Example has low reactivity. In this case, since the setter 1 according to the present embodiment uses cerium oxide (CeO ₂ ) as a base material, the setter 1 as the object 100 even when the object 100 is heated and fired in a high temperature region. The reactivity with the mounting surface 10 is reduced.

Embodiment 2 of the present invention will be described below. Since the present embodiment basically has the same configuration and operational effects as the first embodiment, FIG. 1 is applied mutatis mutandis. The setter 1 for firing uses, as a base material, a ceramic fired body having a mounting surface 10 and a back surface 12 on which an object 100 formed of a ceramic molded body to be fired is placed. The base material is cerium oxide (CeO ₂ ). In a molar _{ratio, Al 2 O 3, Cr 2} O 3, Fe 3 O 4, CaO, MgO, Mn 3 O 4, La 2 O 3, Nd 2 O 3, SiO 2, B 2 O 3, ZrO 2, TiO ₂ and at least one of Y ₂ O ₃ is contained in an amount of 0.1 to 30%. A role can be expected as a sintering aid. The firing temperature when the setter compacted body is fired at a high temperature to form a setter sintered body is in the range of 1450 to 1550 ° C. When the entire setter 1 is 100% by mass, the cerium oxide (CeO ₂ ) is 99.90% or more by molar ratio. The average crystal grain size on the mounting surface 10 can be the same as in Example 1.

A third embodiment of the present invention will be described below with reference to FIG. The third embodiment has basically the same configuration and function as the first and second embodiments. The setter 1 has a flat sheet shape or a film shape, has flexibility, and a placement surface 10 on which an object 100 formed of a ceramic molded body to be fired is placed. A ceramic fired body having a back surface 12 is used as a base material. The base material is cerium oxide (CeO ₂ ). As a sintering aid, a molar _{ratio, Al 2 O 3, Cr 2} O 3, Fe 3 O 4, CaO, MgO, Mn 3 O 4, La 2 O 3, Nd 2 O 3, SiO 2, B 2 O ₃ , ZrO ₂ , TiO ₂ , Y ₂ O ₃ at least one of 0.1 to 30% is included.

  The average crystal grain size on the mounting surface 10 can be the same as in Example 1, and can be in the range of 2 to 30 micrometers, in particular in the range of 6 to 20 micrometers. The thickness t1 of the setter 1 is set to be thinner than the thickness t2 of the object 100. However, in some cases, the thickness t1 of the setter 1 is set to be thicker than the thickness t2 of the object 100. Of course, the thickness t1 of the setter 1 is larger than the average crystal grain size.

  In the vicinity of 700 to 1700 ° C., the thermal conductivity of the setter 1 is as low as 0.03 cal / cm · sec · ° C. or less, particularly 0.02 cal / cm · sec · ° C. or less. Thus, when the heat conductivity of the setter 1 is low, if the thickness of the setter 1 is thick, it takes time to soak the setter 1, and temperature unevenness occurs on the mounting surface 10 of the setter 1 during the temperature rising process. There is a risk. In this case, when the object 100 placed on the setting surface 10 of the setter 1 is baked, temperature unevenness of the object 100 is induced, and there is a limit to further improving the quality of the object 100.

  Therefore, according to the present embodiment, the thickness of the setter 1 is set thin within a range of 10 to 300 micrometers, within a range of 20 to 200 micrometers, and particularly within a range of 30 to 150 micrometers. Such a setter 1 can be formed by reducing the gap between the tip of the blade and the slurry conveying surface by the doctor blade method. Since the thickness of the setter 1 is thin as described above, the material cost can be reduced, and when the target object 100 is placed on the mounting surface 10 of the setter 1 and the target object 100 is fired, temperature unevenness is easily suppressed in the setter 1. As a result, temperature unevenness of the object 100 can be easily suppressed, and the quality of the object 100 can be further improved. Further, since the thickness of the setter 1 is extremely thin, the setter 1 has high flexibility. Therefore, it is effective to bring the surface of the object 100 and the placement surface 10 of the setter 1 into close contact with each other while adapting to the shape of the object 100. The thermal conductivity of the setter 1 can be adjusted by the composition, pore size or porosity of the setter 1, and the thermal conductivity of the setter 1 is as low as 0.005 cal / cm · sec · ° C. or less in the vicinity of 700 to 1700 ° C. You can also

  Embodiment 4 of the present invention will be described below. Since this embodiment basically has the same configuration and effect as the first, second, and third embodiments, FIGS. 1 to 3 apply mutatis mutandis. The object 100 to be fired on the flat mounting surface 10 of the setter 1 is an oxide. In this case, when the target object 100 is placed on the placement surface 10 of the setter 1 and fired, if the surface of the target object 100 and the placement surface 10 of the setter 1 are in close contact, the target object 100 is in a firing atmosphere. Contact with air is restricted, and there may be a portion of the object 100 that is deficient in oxygen. In this regard, according to the present embodiment, the setter 1 has high oxygen ion conductivity in a high temperature region corresponding to the firing temperature of the object 100, so that diffusion of oxygen ions is expected in the setter 1, and oxygen shortage is present in the object 100. Are reduced. For this reason, it can contribute to raising the baking quality of the target object 100 which is an oxide type.

  Embodiment 5 of the present invention will be described below with reference to FIG. The present embodiment basically has the same configuration and effect as the first to fourth embodiments. The compacted body to be the setter 1 is pressure-molded by the press die 40. The press die 40 includes a female die 42 having a molding cavity 41 and a male die 43 inserted into the molding cavity 41. Due to commercially available starting materials and the like, cerium oxides tend not to be dense. Therefore, the bottom surface 41a of the molding cavity 41 of the female mold 42 and the pressing surface 43a facing the bottom surface 41a of the male mold 43 are roughened to form an uneven rough surface. When the compacted body is pressure-molded, the air discharge performance is increased due to the unevenness, which is advantageous for increasing the compressibility and density ratio of the compacted body. As a result, the setter 1 can be densified. The strength can be further increased. By adjusting the size of such irregularities, it is possible to adjust the pore size and / or porosity of the setter 1 and adjust the thermal conductivity of the setter 1. Therefore, in the setter 1 obtained by firing the compacted body, the mounting surface 10 and the back surface 12 are formed with uneven portions 18 having a large number of unevenness. The surface roughness of the concavo-convex portion 18 of the setter 1 can be 10 to 300 micrometers, 20 to 200 micrometers, or 20 to 100 micrometers with Ra, although it depends on the thickness of the setter 1. The thickness of the setter 1 can be about 1 to 10 millimeters and about 2 to 5 millimeters.

  Embodiment 6 of the present invention will be described below with reference to FIG. The present embodiment basically has the same configuration and operational effects as the first embodiment. The firing setter 1 includes a flat placing surface 10 on which an object 100 (for example, a PZT shaped body) formed of an unfired or semi-fired ceramic shaped body is placed, and a flat surface facing the placing surface 10. A rear surface 12. The setter 1 has a flat plate shape formed of a sintered ceramic body having a placement surface 10 on which the object 100 is placed, and a convex projecting engagement portion 2 (setter) provided on the placement surface 10. 1 and a concave portion 3 (depth: M1) which is provided on the back surface 12 of the setter 1 and is engaged with the tip end portion of the projecting engagement portion 22 of the other setter 1 And have. A plurality of the projecting engagement portions 2 and the recessed portions 3 are integrally formed on the setter 1 and are formed so as to be back-to-back with each other. A plurality (at least three) of projecting engagement portions 2 are formed at the edge of the setter 1 in the length direction. A plurality of (at least three) concave portions 3 are also formed on the edge of the setter 1 in the length direction.

As shown in FIG. 5, the plurality of setters 1 can be stacked in the vertical direction by the engagement of the protruding protrusion engaging portion 2 of one setter 1 and the concave portion 3 of the other setter 1. Has been. And the several setter 1 is laminated | stacked on the up-down direction in the state which mounted the target object 100, such as a PZT molded object, on the mounting surface 10 of the setter 1. FIG. And the target object 100 on the setter 1 is baked by heating to a high temperature area | region with the baking furnace which has an atmospheric condition. As described above, by using a plurality of firing setters 1 stacked on top and bottom, the space 200 on the placement surface 10 of the lower firing setter 1 is covered with the upper firing setter 1. Since the object 100 is a closed space or close to a closed space, even if the object 100 is a ceramic molded body (for example, an unfired PZT molded body) containing an element that easily evaporates such as Pb, the amount of transpiration of the element is suppressed. The benefits are expected. That is, since the space 200 above the mounting surface 10 is narrow, the interior of the space 200 above the mounting surface 10 easily reaches a saturated vapor pressure due to slight evaporation from the object 100 when the object 100 is baked. Since the above transpiration is suppressed, the target object 100 (PZT) after firing has a small composition change and is advantageous for exhibiting good piezoelectric characteristics. In this embodiment, the projecting direction of the projecting engagement portion 2 (that is, The tip of the firing setter 1 in the stacking direction) is set so that the cross-sectional area (that is, the cross-sectional area along the direction orthogonal to the stacking direction) decreases toward the tip. Specifically, the projecting engagement portion 2 has an outer wall surface 20 that is inclined so as to become narrower toward the distal end (upper end), and is provided with a convex roundness provided at the distal end of the outer wall surface 20. Part 21. The outer wall surface 20 has a shape along a conical shape or a pseudo-conical shape. The concave portion 3 is provided with a flat concave bottom surface 3x having a concave space that is circular in bottom view and can be engaged with the distal end portion of the protruding engagement portion 2 in the setter 1. It is formed to be back to back. In manufacturing the protruding engagement portion 22, a compacted body that becomes a setter main body having a portion that becomes the protruding engagement portion 2 may be integrally formed and then fired. Or the compacted body used as a setter main body and the compacted body used as the protrusion engagement part 2 may be separately formed beforehand, and both may be pressure-bonded integrally and then fired.

  Further, since the tip rounded portion 21 is formed at the tip of the projecting engagement portion 22, the contact area between the tip rounded portion 21 of the projecting engagement portion 2 and the other setter 1 can be kept small. Therefore, even if the temperature of the baking process which bakes the target object 100 is quite high, and the protrusion engaging part 2 and the other setter 1 are bound by heat influence, it protrudes after completion | finish of baking. The engaging part 2 can be easily separated from the other setters 1.

  As shown in FIG. 5, since the inner diameter D1 of the concave portion is considerably larger than the outer diameter D2 of the tip rounded portion 21 formed at the tip of the projecting engagement portion 2, the tip rounded portion 21 is mounted on the setter 1. The position can be positively adjusted along the surface direction of the placement surface 10 (a two-dimensional direction including the X1 and X2 directions). In addition, according to the present Example, since the protrusion engaging part 2 and the recessed part 3 are formed back to back so as to face each other, if necessary, the setter 1 is inverted upside down and stacked. You can also.

Hereinafter, Example 7 will be described. Since the present embodiment basically has the same configuration and effects as the above-described embodiments, the description will be given with reference to FIGS. Although cerium oxide is chemically stable in an oxidizing atmosphere, its thermal shock resistance is not always sufficient. Further, cerium oxide (CeO ₂ ) has a low specific resistance at 500 to 1900 ° C. and tends to be an electric conductor. For this reason, while setting one electrode in the one end part of the setter 1, and setting the other electrode in the other end part of the setter 1, it is possible to heat the setter 1 by energizing the electrodes in an oxidizing atmosphere. it can. For this reason, when the setter 1 on which the object 100 is placed is inserted into a firing furnace and the object 100 is fired, the setter 1 itself can be preheated to a temperature close to a predetermined temperature by electric heating, so that the thermal shock in the setter 1 can be reduced. . The object 100 can be mounted on the mounting surface 10 of the setter 1 preheated to a certain temperature and fired in a firing furnace having an oxidizing atmosphere. According to the literature (Sintered ceramics detailed 4, fine ceramics, page 548, Gihodo Shuppan, first printing on January 25, 1951), the specific resistance of the ceria pressure body is 5 × 10 at 500 ° C. in the air. ⁷ Ω · cm, and 240 Ω · cm at 1200 ° C.

Example 8 will be described below. Since the present embodiment basically has the same configuration and effects as the above-described embodiments, the description will be given with reference to FIGS. The setter 1 of the present embodiment is a porous body having a large number of pores. The porosity can be set as appropriate, but the volume ratio is 1 to 10%. When a setter 1 is formed by firing a compacted body based on CeO ₂ near 1950 ° C., CeO ₂ may be partially dissociated to become Ce ₂ O ₃ and free oxygen. In this case, the escaped oxygen may cause pores. In this case, when the target object 100 is placed on the setter 1 and the target object 100 is fired, it can be expected to improve the exhaustability of the gas discharged from the target object 100 or the like.

  (Others) The present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications within a range not departing from the gist. In the vicinity of 700 to 1700 ° C., the thermal conductivity of the setter 1 can be 0.01 cal / cm · sec · ° C. or less.

It is sectional drawing which shows the state which laminated | stacked the setter which concerns on Example 1. FIG. It is explanatory drawing which shows the measurement form of the average crystal grain diameter of a setter. It is sectional drawing which shows the principal part of the state which laminated | stacked the setter which concerns on Example 2. FIG. It is sectional drawing which shows the principal part of the state which shape | molds the compacting body of the setter which concerns on Example 5. FIG. It is sectional drawing which shows the principal part of the state which laminated | stacked the setter which concerns on Example 6. FIG.

Explanation of symbols

  In the figure, 1 is a setter, 10 is a placement surface, 12 is a back surface, and 100 is an object.

Claims (4)

  A setter for firing comprising a ceramic fired body having a mounting surface on which an object formed of an unfired or semi-fired ceramic molded body to be fired is mounted, the cerium oxide being a base material A setter for firing. According to claim 1, in a molar _{ratio, Al 2 O 3, Cr 2} O 3, Fe 3 O 4, CaO, MgO, Mn 3 O 4, La 2 O 3, Nd 2 O 3, at least one of SiO ₂ A setter for firing comprising 0.1 to 30% of seeds.   The setter for firing according to claim 1 or 2, wherein the average crystal grain size on the mounting surface is in the range of 10 to 300 micrometers.   4. The firing setter according to claim 1, wherein the thermal conductivity is about 0.03 cal / cm · sec · ° C. or less in the vicinity of 700 to 1700 ° C. 5.

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