JP4432341B2 - Ceramic plate firing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for firing a ceramic plate such as a laminated piezoelectric substrate used for a piezoelectric actuator, a piezoelectric sensor, or the like.
[0002]
[Prior art]
A conventional method for firing a ceramic plate is disclosed, for example, in Patent Document 1 below. In the firing method described in Patent Document 1, the ceramic plate is placed on the lower setter of the setter facing the ceramic plate so that a gap of a predetermined interval is formed between the ceramic plate and the upper setter. The upper setter is supported on the lower setter by struts having the same shrinkage properties. When firing in this state, the struts contract together with the ceramic plate, so that the gap between the ceramic plate and the upper setter can be kept at a predetermined interval.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-324574 [0004]
[Problems to be solved by the invention]
However, in the firing method described above, since the peripheral portion of the ceramic plate between the setters facing each other is open, the concentration of the atmosphere between the ceramic plate and the upper setter is not kept uniform during firing, There is a possibility that the ceramic plate shrinks unevenly depending on the location, and the fired ceramic plate is warped or swelled. This problem becomes more prominent as the thickness of the ceramic plate is reduced.
[0005]
Therefore, the present invention has been made in view of such circumstances, and provides a method for firing a ceramic plate that can prevent warping and undulation from occurring in the fired ceramic plate.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a method for firing a ceramic plate according to the present invention is a method for firing a ceramic plate in which a ceramic plate is disposed between a first holding member and a second holding member for firing. The first holding member and the second holding member are provided so that a gap equal to or less than the thickness of the ceramic plate is provided between the ceramic plate placed on the first holding member and the second holding member. A plurality of spacers that hold a gap between the first holding member and the second holding member are disposed around the ceramic plate between the adjacent spacers, and adjacent spacers are provided at a predetermined distance from the ceramic plate. The ceramic plate is degreased and fired by disposing an enclosing member made of a ceramic material having the same composition as the ceramic plate and having the same height as the thickness of the ceramic plate.
[0007]
In this method of firing a ceramic plate, the peripheral portion of the ceramic plate between the first holding member and the second holding member is surrounded by an enclosing member formed of a ceramic material having substantially the same composition as the ceramic plate. Therefore, the concentration of the atmosphere in which the ceramic plate is disposed is kept uniform during firing. Accordingly, the shrinkage of the ceramic plate due to firing can be made uniform, and warpage and undulation can be prevented from occurring in the fired ceramic plate.
[0008]
The ceramic plate means not only a single plate of a ceramic sheet but also a plate-like laminate formed by laminating a plurality of ceramic sheets, and includes those in which electrodes and the like are formed using the ceramic sheet as a substrate.
[0009]
And the firing method of the ceramic board which concerns on this invention is especially effective when the ceramic material which forms a ceramic board contains the compound containing lead. Lead in lead-containing compounds such as lead titanate and lead zirconate titanate is easy to evaporate by firing, but the ceramic plate is placed because the surrounding member is made of a ceramic material with almost the same composition as the ceramic plate In the atmosphere, lead in the lead-containing compound is released from the surrounding member. Thereby, it is suppressed that the lead in the compound containing lead evaporates from the ceramic plate, and the lead concentration in the atmosphere in which the ceramic plate is arranged is kept uniform during firing. Therefore, the shrinkage of the ceramic plate due to firing is made constant, and it is possible to prevent warping and undulation from occurring in the fired ceramic plate.
[0010]
Further, the ceramic plate is placed on the first holding member, is provided between the ceramic plate and the second holding member, Ru thickness following clearance of the ceramic plate is provided. In this way, when firing is performed by providing a gap equal to or less than the thickness of the ceramic plate between the ceramic plate and the second holding member, the uniformity of the concentration of the atmosphere in which the ceramic plate is disposed is promoted. It is possible to further suppress the warpage and undulation of the ceramic plate.
[0011]
Furthermore, the enclosing member is that having a thickness the same height as the ceramic plate. When firing in such a state, similarly to the above, the concentration of the atmosphere in which the ceramic plate is arranged is promoted, and the warpage and undulation of the ceramic plate can be further suppressed. In addition, when the second holding member is brought close to the ceramic plate, the surrounding member does not become an obstacle, and therefore, when the gap between the ceramic plate and the second holding member is set to be equal to or less than the thickness of the ceramic plate. It is particularly effective.
[0012]
Furthermore, the enclosing member is Ru are arranged at a predetermined distance from the ceramic plate. The concentration of the atmosphere in which the ceramic plate is arranged so that the occurrence of warpage and undulation in the ceramic plate is suppressed according to the thickness and composition of the ceramic plate by taking a predetermined distance between the ceramic plate and the surrounding member Can be adjusted.
[0013]
Around part of the ceramic plate, a spacer for holding the gap between the first holding member and the second holding member is more disposed, between adjacent spacers Ru is arranged enclosing member. As described above, by arranging the surrounding member between the adjacent spacers, the holding member can be reduced in size and space-saving.
[0014]
Further, it is preferable that the ceramic plate is taken out from the ceramic material, and the surrounding member is formed by the remaining portion of the ceramic material from which the ceramic plate is taken out. For example, if the surrounding member is formed by the remaining part of the ceramic material when the ceramic plate is removed by punching from a ceramic material such as a single sheet of green sheets or a laminate of green sheets, the composition of the ceramic plate is almost the same. The surrounding member containing the ceramic material can be efficiently formed. In addition, the cost required for firing the ceramic plate can be reduced by utilizing the remaining portion of the ceramic material that is generally a waste material.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
[First Embodiment]
As shown in FIGS. 1 and 2, on a dense zirconia setter (first holding member) 1 formed in a 10 mm × 10 mm square shape (porosity 3% or less, more preferably 1% or less). The ceramic plate 2 is placed on the surface. The zirconia setter 1 is preferably stabilized with 3 mol% to 8 mol% of yttria (Y203) because of its low reactivity with the ceramic plate 2 during firing and good durability. Further, the ceramic plate 2, the piezoelectric ceramic (more details, including lead zirconate _{titanate, PbTiO 3 -PbZrO 3 -Pb (Mg1} / 3 Nb2 / 3) O 3 -Pb (Zn1 / 3 Nb2 / 3) O ₃ is a single plate formed by the following method.
[0017]
That is, materials in the form of oxides or carbonates are wet-mixed by a ball mill, and after the mixing, preliminary firing is performed at 950 ° C. The pre-fired material is wet pulverized with a ball mill to prepare a piezoelectric ceramic powder. Subsequently, a binder, a solvent, or the like is added to the piezoelectric ceramic powder to form a slurry, and a green sheet (ceramic material) having a thickness of 0.15 mm is formed by an extrusion method. The green sheet is cut and cut to obtain a ceramic sheet 2 having a square thin plate shape of “80 mm × 80 mm, thickness 0.15 mm”.
[0018]
The ceramic plate 2 produced in this way is arranged in the center of the zirconia setter 1, and the spacers 3 having a height of 0.30 mm are placed at the four corners of the blank portion on the zirconia setter 1 formed thereby. Further, a bar-shaped surrounding member 4 is placed between the adjacent spacers 3 on the zirconia setter 1. At this time, each of the four surrounding members 4 is separated from each of the four side surfaces 2 a of the ceramic plate 2 by a certain distance. Thus, the zirconia setter 1 can be reduced in size by arranging the surrounding member 4 between the adjacent spacers 3 and 3. The spacer 3 is preferably made of the same material as the zirconia setter 1, but may be made of a material such as alumina or magnesia. The shape of the spacer 3 is not limited to a prismatic shape, and may be a cylindrical shape, for example. Moreover, each surrounding member 4 is formed from the remaining part of the green sheet from which the ceramic plate 2 was cut out in the production of the ceramic plate 2 described above.
[0019]
Then, a zirconia setter (second holding member) 5 having the same shape as the zirconia setter 1 is placed on the spacer 3 so as to face the zirconia setter 1. As a result, a gap S with an interval of 0.15 mm is formed between the upper surface 2 b of the ceramic plate 2 and the lower surface 5 a of the zirconia setter 5.
[0020]
The firing unit 10 configured as described above is housed and heated in a closed bowl 7 as shown in FIG. Thereby, the sintering reaction of the ceramic plate 2 occurs, and a fired body of the ceramic plate 2 is obtained. The firing temperature is 1100 ° C. and the stabilization time is 2 hours. Before firing the ceramic plate 2, the ceramic plate 1 and the surrounding members 4 are heated at 350 ° C. with the ceramic plate 1 and the surrounding members 4 placed at the predetermined positions on the zirconia setter 1. 4 was degreased.
[0021]
In the method for firing a ceramic plate according to the first embodiment, the surrounding portion (surrounding space) of the ceramic plate 2 between the zirconia setters 1 and 5 is surrounded by the surrounding member 4 made of a ceramic material having substantially the same composition as the ceramic plate 2. Since it is surrounded, lead in the lead zirconate titanate is released from each surrounding member 4 into the gap S between the ceramic plate 2 and the zirconia setter 5. Thereby, evaporation of lead in the lead zirconate titanate from the ceramic plate 2 is suppressed, and the lead concentration in the gap S is kept uniform during firing. Accordingly, the shrinkage of the ceramic plate 2 due to firing can be made uniform, and the ceramic plate 2 after firing can be prevented from warping or waviness.
[0022]
And it became clear from the experimental result shown next that the curvature of the ceramic board 2 after baking can be made very small if the space | interval of the clearance gap S is made into the thickness of the ceramic board 2 or less. The main reason for this is that if firing is performed with the gap S being equal to or less than the thickness of the ceramic plate 2, the uniform concentration of lead in the gap S is promoted.
[0023]
First, when the gap S is 0.15 mm (= thickness of the ceramic plate 2) as described above, the amount of warpage is 15.7 μm, and the gap S is 0.10 mm (<ceramic plate 2). Thickness), the amount of warpage was 15.5 μm. On the other hand, when the gap S was set to 0.30 mm (> thickness of the ceramic plate 2), the amount of warpage was 95.5 μm. As described above, when the gap S is set to be equal to or smaller than the thickness of the ceramic plate 2, the amount of warpage can be suppressed to about 1/6. Here, the amount of warpage is the maximum height difference of the ceramic plates 2 measured using a laser-type non-contact three-dimensional shape measuring apparatus, and is an average value for 100 ceramic plates 2.
[0024]
When the gap S is set to 0.10 mm or less, there is a slight tendency that the square ceramic plate 2 is distorted into a trapezoid or a parallelogram or the ceramic plate 2 is cracked or chipped. It was. Therefore, it is more preferable to make the gap S larger than 0.10 mm. In addition, when a porous (porosity of about 15%) zirconia setter was used in place of the dense zirconia setters 1 and 5, there was a slight tendency for the amount of warpage to increase.
[0025]
In the ceramic plate firing method according to the first embodiment, since the height of the surrounding member 4 is substantially the same as the thickness of the ceramic plate 2, the height of the spacer 3 is adjusted so that the zirconia setter 5 is ceramic. When approaching the plate 2, the surrounding member 4 does not become an obstacle.
[0026]
Moreover, since each surrounding member 4 is spaced apart from the side surface 2a of the ceramic plate 2 by a certain distance, the lead concentration in the gap S on the ceramic plate 2 can be made uniform. In addition, by adjusting the distance between the side surface 2 a of the ceramic plate 2 and the surrounding member 4, the gap S is controlled so that the warpage or undulation in the ceramic plate 2 is suppressed according to the thickness or composition of the ceramic plate 2. The lead concentration in can be adjusted.
[0027]
Furthermore, since the surrounding member 4 is the remaining part of the green sheet from which the ceramic plate 2 is cut, the surrounding member 4 made of a ceramic material having substantially the same composition as the ceramic plate 2 can be efficiently formed. In addition, since the remaining portion of the green sheet that is generally a waste material is used, the cost required for firing the ceramic plate 2 can be reduced, and the amount of waste material generated can be reduced.
[0028]
[Second Embodiment]
In the method of firing a ceramic plate according to the second embodiment, a ceramic sheet laminate in which electrodes are patterned is used as the ceramic plate 2. This ceramic plate 2 is 10 sheets taken out by pressing from a green sheet laminate (ceramic material) after the press treatment, and is formed in a rectangular thin plate shape of “33 mm × 12 mm, thickness 0.375 mm”. Yes. In addition, the ceramic plate 2 is subjected to a polarization treatment or the like after firing as described below to become a multilayer piezoelectric element.
[0029]
As shown in FIGS. 4 and 5, 10 ceramic plates 2 cut out from the green sheet laminate are placed on the zirconia setter 1 in a matrix of 2 rows and 5 columns in the center of the zirconia setter 1. Deploy. Then, four bar-shaped surrounding members 4 are placed on the zirconia setter 1 so as to surround the periphery of the assembly of ceramic plates 2. Further, the spacers 3 having a height of 0.75 mm are placed at the four corners of the blank portion on the zirconia setter 1. In addition, each surrounding member 4 is formed from the remaining part of the laminated body of the green sheet from which the ceramic board 2 was cut out.
[0030]
Then, a zirconia setter 5 having the same shape as that of the zirconia setter 1 is placed on the spacer 3 so as to face the zirconia setter 1. Thereby, a gap S having an interval of 0.375 mm is formed between the upper surface 2b of each ceramic plate 2 and the lower surface 5a of the zirconia setter 5.
[0031]
The baking unit 10 configured as described above is degreased at 350 ° C., and then accommodated in the sealed mortar 7 and heated as in the first embodiment described above. Thereby, the sintering reaction of the ceramic plate 2 occurs, and a fired body of the ceramic plate 2 is obtained. The firing temperature is 1100 ° C. and the stabilization time is 2 hours.
[0032]
Also in the method of firing the ceramic plate according to the second embodiment, the ceramic plate 2 has a substantially same composition as the ceramic plate 2 in the periphery of each ceramic plate 2 between the zirconia setters 1 and 5 as in the first embodiment. Since it is surrounded by the surrounding member 4 made of a material, shrinkage of each ceramic plate 2 due to firing can be made uniform, and it is possible to prevent warping and undulation from occurring in each ceramic plate 2 after firing.
[0033]
And the experimental result by the same experiment as 1st Embodiment is as follows. First, when the gap S is 0.375 mm (= thickness of the ceramic plate 2) as described above, the amount of warpage is 13.5 μm, and the gap S is 0.10 mm (<ceramic plate 2). ), The amount of warpage was 13.3 μm. On the other hand, when the gap S was 0.825 mm (> thickness of the ceramic plate 2), the amount of warpage was 92.6 μm. As described above, when the gap S is set to be equal to or smaller than the thickness of the ceramic plate 2, the amount of warpage can be suppressed to about 1/7.
[0034]
The present invention is not limited to the first and second embodiments. For example, as long as the surrounding member is formed of a ceramic material having substantially the same composition as the ceramic plate, the surrounding member may not be the remaining portion of the ceramic material from which the ceramic plate is taken out. Of course, even if the surrounding member and the ceramic plate are formed of a ceramic material having the same composition, an effect equal to or greater than that of the case where the surrounding member and the ceramic plate are formed of a ceramic material having substantially the same composition can be obtained. Moreover, although the said 1st and 2nd embodiment was the case where the surrounding part of a ceramic board is surrounded by several surrounding members, you may surround the surrounding part of a ceramic board by a ring-shaped surrounding member. Further, even if the height of the surrounding member and the thickness of the ceramic plate are not substantially the same (for example, even if the height of the surrounding member is smaller than the thickness of the ceramic plate), the ceramic plate after firing is warped or undulated. It is possible to prevent. Furthermore, as shown in FIG. 6, the firing units according to the first embodiment and the firing units according to the second embodiment are stacked in a plurality of stages (for example, 10 stages) and accommodated in a sealed bowl, and firing of the plurality of ceramic plates is performed. You may do it at the same time.
[0035]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent warping and undulation from occurring in the fired ceramic plate.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional front view of a firing unit according to a first embodiment.
FIG. 2 is a plan view in which a part of the firing unit shown in FIG. 1 is cut away.
FIG. 3 is a partial cross-sectional front view showing a state where the firing unit shown in FIG. 1 is housed in a closed mortar.
FIG. 4 is a partial cross-sectional front view of a firing unit according to a second embodiment.
FIG. 5 is a plan view in which a part of the firing unit shown in FIG. 4 is cut away.
FIG. 6 is a partial cross-sectional front view showing a state in which a plurality of firing units are stacked and accommodated in a closed bowl.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Zirconia setter (1st holding member), 2 ... Ceramic board, 3 ... Spacer, 4 ... Enclosing member, 5 ... Zirconia setter (2nd enclosing member).

Claims (3)

A method of firing a ceramic plate in which a ceramic plate is disposed between a first holding member and a second holding member and fired.
The first holding member and the first holding member and the second holding member are provided with a gap equal to or less than the thickness of the ceramic plate between the ceramic plate placed on the first holding member and the second holding member. A plurality of spacers for holding a gap between the first holding member and the second holding member are disposed around the ceramic plate between the second holding member and a predetermined distance from the ceramic plate. The ceramic plate is degreased by disposing an enclosing member formed of a ceramic material having the same composition as the ceramic plate and having the same height as the thickness of the ceramic plate between the adjacent spacers. And firing the ceramic plate, characterized by firing.   The method for firing a ceramic plate according to claim 1, wherein the ceramic material forming the ceramic plate contains a lead-containing compound. The ceramic plate is removed from the ceramic material;
The method of firing a ceramic plate according to claim 1 or 2 , wherein the surrounding member is formed by a remaining portion of the ceramic material from which the ceramic plate has been taken out.

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