JP2007227483A - Laminated ceramic element manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely suppress the occurrence of cracks and the elution of an internal electrode layer in a laminated ceramic element. <P>SOLUTION: A laminated ceramic element manufacturing method is composed so as to bake a laminated body, in which a ceramic precursor layer including a material of a ceramic layer and an internal electrode precursor layer including a material of the internal electrode layer are alternately laminated, in a state of storing it in a sagger partially provided with an opening after degreasing the laminated body. The laminated body is stored in the sagger in a placed state on a setter. Unevenness is formed in the setter on a placing face onto which the laminated body is placed. A ratio A/B is ≥15% between volume A of spaces under the laminated body formed by the unevenness and volume B of the laminated body. It is preferable that a flat part does not substantially exist at each tip of protrusions contacting with the laminated body 13 in the unevenness of the setter 12. The unevenness of the setter 12 is, for example, a plurality of mutually parallel grooves 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, after degreasing a laminate obtained by alternately laminating a ceramic precursor layer containing a raw material for a ceramic layer and an internal electrode precursor layer containing a raw material for an internal electrode layer, an open portion is provided in part. The present invention relates to a method for manufacturing a multilayer ceramic element that is fired in a state of being accommodated in a pot.

  For example, a laminated ceramic element typified by a piezoelectric element or the like forms a green sheet by adding a binder or a solvent to a ceramic material, prints a conductive paste on the surface of the green sheet, and laminates the green sheet to form a laminated body. Then, it is manufactured by degreasing and baking in a heating furnace or the like. The firing is usually performed in a state where the degreased laminate is housed in a ceramic container called a mortar.

  By the way, when a metal having a low melting point (for example, lead) is included as a ceramic material, the composition shifts due to the evaporation of lead during firing. Therefore, from this viewpoint, the mortar must be sealed. However, if the mortar is hermetically sealed during firing, the binder remaining in the laminate without being removed in the degreasing step evaporates and then remains in the mortar, resulting in delays in ceramic sintering and cracking, etc. May cause malfunctions.

  In addition, when using a base metal such as copper or nickel for the internal electrode, in order to avoid oxidation of the base metal, a reducing atmosphere having a predetermined oxygen partial pressure is introduced into the furnace and firing is performed. If kept in a sealed state, the introduced reducing atmosphere gas does not spread into the sagger. As a result of further reducing the atmosphere in the mortar by volatilizing the carbon component remaining in the laminate after degreasing, when the ceramic material contains lead oxide and the internal electrode contains copper, In some cases, lead oxide is metallized, or the generated metal lead is melted by eutectic reaction with copper.

Thus, attempts have been made to eliminate such problems. For example, in Patent Document 1, in a method for manufacturing an electronic component using a ceramic composition mainly composed of a lead compound as a raw material, the firing process is performed using a partially opened mortar, and the reducing gas is supplied to the mortar. A method for producing a lead-based ceramic electronic component is described in which the decomposition gas of the binder generated during firing and the surplus of lead vapor are discharged from the mortar. According to the prior art, the vapor pressure of PbO does not become excessively high, and the reducing atmosphere generated during burnout of the residual binder can be effectively discharged out of the bowl.
JP-A-6-283378

However, as a result of investigations by the present inventors, it has been found that even if a mortar as described in the above-mentioned prior art is used, the above-mentioned problems cannot be completely solved. Moreover, in the method described in the prior art, a decrease in characteristics such as the piezoelectric constant d ₃₃ was observed, and the characteristic decrease was remarkable particularly when a large-sized laminate was fired.

  Therefore, the present invention has been proposed in view of such a conventional situation, and it is possible to reliably prevent the occurrence of cracks and elution of internal electrodes and to obtain a multilayer ceramic element having good characteristics. An object is to provide a manufacturing method.

  In order to achieve the above-mentioned object, a method for manufacturing a multilayer ceramic element according to the present invention includes alternately laminating a ceramic precursor layer containing a ceramic layer material and an internal electrode precursor layer containing an internal electrode layer material. After degreasing the laminated body, a method for producing a laminated ceramic element that is fired in a state where the laminated body is housed in a mortar provided with an open part, wherein the laminated body is placed on a setter. Concavities and convexities are formed on the mounting surface on which the laminate is placed on the setter. The volume A of the space below the laminate formed by the irregularities and the laminate The ratio A / B with the volume B is 15% or more.

  In the present invention, by using a mortar having an open part in part at the time of firing, exchange between the atmosphere in the furnace and the atmosphere in the mortar is realized, and the firing can be performed smoothly. Further, the residual binder or the like evaporated from the laminated body is quickly discharged from the open portion to the outside of the mortar, and can be fired without causing cracks or internal electrode elution.

  By the way, when the laminated body is directly placed on the bottom surface of the mortar, when the back surface of the laminated body (the side facing the bottom surface of the mortar) is in contact with the bottom surface of the mortar, the firing atmosphere in the furnace is Since it is not supplied to the back surface of the multilayer body, it causes a decrease in characteristics such as a decrease in piezoelectric constant of the multilayer ceramic element. In addition, the said malfunction similarly generate | occur | produces, when a flat setter is spread on the bottom of a mortar. Moreover, since evaporation of residual carbon that has not been removed in the degreasing process is hindered on the back side of the laminate, problems such as generation of cracks and elution of internal electrodes may occur.

  Therefore, in the present invention, by using a setter that ensures a sufficient space under the laminate during firing, the atmosphere in the sagger is easily brought into contact with the back surface of the laminate through the space. Therefore, since firing in a state where the atmosphere in the sagger, that is, the atmosphere in the furnace is in almost equal contact with the entire laminate, is realized, good piezoelectric characteristics are realized in the multilayer ceramic element. Further, the occurrence of cracks and elution of internal electrodes as described above can be suppressed.

  According to the present invention, firing is performed by combining a setter in which the ratio A / B between the volume A of the space under the laminate and the volume B of the laminate is in the above range, and a mortar provided with an open portion. Therefore, a high-performance multilayer ceramic element can be manufactured while reliably suppressing the occurrence of cracks and elution of internal electrodes.

  Hereinafter, a method for manufacturing a multilayer ceramic element to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 shows an example of a multilayer ceramic element (here, a multilayer piezoelectric element) that is a target of the manufacturing method of the present invention. As shown in FIG. 1, the multilayer piezoelectric element 1 includes a multilayer body 4 in which an internal electrode layer 3 is inserted between a plurality of ceramic layers (piezoelectric layer 2). The multilayer body 4 serves as an active portion. Contributes to displacement. Although the thickness per layer of the piezoelectric layer 2 can be arbitrarily set, it is usually set to, for example, about 1 μm to 100 μm. On both sides of the laminate 4, there is an inactive piezoelectric layer region 5 in which the internal electrode layer 3 is not formed as an inactive region. The thickness of the piezoelectric layer in the inactive piezoelectric layer region 5 is determined by the internal electrode layer 3. In some cases, the thickness of the piezoelectric layer 2 is set to be thicker.

  As shown in FIG. 2, the internal electrode layers 3 are alternately extended in opposite directions, and terminal electrodes (not shown) are electrically connected to the internal electrode layers 3 at the ends in the extending directions. Is provided). The terminal electrode may be formed, for example, by sputtering a metal such as Au, or may be formed by baking an electrode paste. The thickness of the terminal electrode is appropriately set depending on the application, the size of the laminated piezoelectric element 1, and the like, but is usually about 10 μm to 50 μm.

  In the laminated piezoelectric element, the internal electrode layer 3 functions as an electrode for applying a voltage to each piezoelectric layer 2 and is made of a conductive material. In this case, a noble metal such as Ag, Au, Pt, or Pd can be used as the conductive material, but in the present invention, a base metal such as Cu or Ni is preferably used. When Cu is used as the conductive material, the internal electrode layer 3 is formed by applying and baking a Cu paste. By using the base metal such as Cu as an electrode material, the manufacturing cost of the multilayer piezoelectric element 1 is reduced.

On the other hand, a piezoelectric ceramic composition is used for the piezoelectric layer 2, and the piezoelectric ceramic composition used is mainly composed of a composite oxide containing Pb, Ti, and Zr as constituent elements, for example. Here, the composite oxide includes, for example, lead zirconate titanate (PZT), lead titanate (PbTiO ₃ ), lead zirconate (PbZrO ₃ ), and lead zinc niobate [Pb (Zn _1/3). Nb _2/3 ) O ₃ ], a composite oxide obtained by substituting a part of Pb with Sr, Ba, Ca or the like in the ternary composite oxide. be able to.

  As a specific composition of the ternary composite oxide, a composition represented by the following formula (A) or (B) can be given. In these formulas (A) and (B), the composition of oxygen is obtained stoichiometrically, and deviation from the stoichiometric composition is allowed in the actual composition. .

Pb _a [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (A)
(However, 0.96 ≦ a ≦ 1.03, 0.05 ≦ x ≦ 0.15, 0.25 ≦ y ≦ 0.5, 0.35 ≦ z ≦ 0.6, and x + y + z = 1.)

(Pb _a-b Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (B)
(However, 0.96 ≦ a ≦ 1.03, 0 <b ≦ 0.1, 0.05 ≦ x ≦ 0.15, 0.25 ≦ y ≦ 0.5, 0.35 ≦ z ≦ 0.6 X + y + z = 1, and Me in the formula represents at least one selected from Sr, Ca, and Ba.)

  The laminated piezoelectric element 1 includes a lamination process in which a ceramic precursor layer (piezoelectric layer 2) and internal electrode layer 3 after firing are alternately laminated with a ceramic precursor layer and an internal electrode precursor layer to form a laminate. It is produced by a degreasing step for degreasing and a firing step for firing the degreased laminate. Hereinafter, a method for manufacturing the multilayer piezoelectric element 1 will be described.

In order to produce the laminated piezoelectric element 1, first, a lamination process is performed. In this lamination process, the raw material of the piezoelectric layer 2 is prepared, weighed according to the target composition, mixed, and calcined. And then pulverized to obtain a ceramic precursor powder. The raw material of the piezoelectric layer 2 includes oxides, carbonates, oxalates, hydroxides, etc. of the elements constituting the piezoelectric layer 2. For example, the piezoelectric layer 2 is made of the above lead zirconate titanate. In some cases, lead oxide (PbO), titanium oxide (TiO ₂ ), and zirconium oxide (ZrO ₂ ) are used as raw materials. Next, a binder or the like is added to the obtained ceramic precursor powder to form a ceramic raw material mixture, and this ceramic raw material mixture is formed into a sheet shape to form a ceramic precursor layer.

  Similarly, a base metal that is a raw material of the internal electrode layer 3, such as metallic copper, is prepared, and a binder or the like is added to form an internal electrode raw material mixture. As a raw material of the internal electrode layer 3, the metallic copper may be used alone or in combination with other materials. In this case, examples of the other material include a copper oxide or an organic copper compound which becomes metal copper after firing, and a metal other than metal copper, a metal oxide, an organic metal compound, or the like. Moreover, you may add additives, such as a dispersing agent, a plasticizer, a dielectric material, an insulator material, to an internal electrode raw material mixture as needed.

  The internal electrode precursor layer is formed by, for example, screen printing the internal electrode raw material mixture on the ceramic precursor layer. As described above, a plurality of ceramic precursor layers on which the internal electrode precursor layers are formed are stacked to obtain a stacked body in which the ceramic precursor layers and the internal electrode precursor layers are alternately stacked.

  After the above-mentioned lamination process, a degreasing process is performed with respect to the obtained laminated body in a degreasing process. The degreasing step is a step of decomposing and removing the ceramic precursor layer and the binder contained in the internal electrode precursor layer constituting the laminate by heating.

  The degreasing step is preferably performed in a reducing atmosphere in order to suppress oxidation of the metal contained as the raw material of the internal electrode layer 3. Specifically, the oxygen partial pressure at which the oxide that the ceramic precursor layer contains as a raw material of the ceramic layer (piezoelectric layer 2) and the metal that the internal electrode precursor layer contains as a raw material of the internal electrode layer 3 can coexist is set. It is preferable to perform degreasing in an atmosphere gas.

  Specifically, the reducing atmosphere means that an oxide included in the ceramic precursor layer as a raw material for the ceramic layer (piezoelectric layer 2) and a metal included in the internal electrode precursor layer as a raw material for the internal electrode layer 3 coexist. An atmospheric gas having a possible oxygen partial pressure. For example, when the piezoelectric layer 2 contains lead oxide (PbO) as an oxide and the internal electrode layer 3 contains copper (Cu) as a metal, degreasing is performed in an atmospheric gas having an oxygen partial pressure in which Cu and PbO can coexist. It is preferable to perform a process. As shown in FIG. 3, the atmospheric gas having an oxygen partial pressure in which a metal and an oxide can coexist has an oxygen partial pressure at which a metal (for example, Cu) is not oxidized and an oxide (for example, PbO) is not reduced. It refers to the atmospheric gas that it has.

Further, an inert gas such as nitrogen (N ₂ ) or argon (Ar), water vapor, and, if necessary, an atmosphere gas containing hydrogen is introduced into the furnace, and the oxygen partial pressure atmosphere represented by the formula (1) is used. Performing the degreasing step is also a preferred form. The oxygen partial pressure is more preferably within the range shown in Formula (2).
p (O ₂ ) ≦ (25331 × Kp) ^2/3 (1)
Kp ² × 10 ⁶ ≦ p (O2) ≦ (25331 × Kp) ^2/3 (2)
[Wherein, Kp represents the dissociation equilibrium constant of water. The unit of oxygen partial pressure p (O ₂ ) is Pa. ]

  In the degreasing step, the temperature during the degreasing treatment is preferably 600 ° C. or lower. This is because if the degreasing temperature exceeds 600 ° C., the lead-based ceramic material starts to sinter, so that the densification may occur and the ventilation holes may be blocked, and decomposition and volatilization of the binder may be hindered.

  After the degreasing step, the multilayer body is fired in the firing step to obtain the multilayer ceramic element 1. At the time of firing, for example, a setter 12 as shown in FIG. 5 is arranged in a mortar 11 as shown in FIG. 4 and a laminate 13 is placed on the setter 12.

  In the firing step, it is necessary to bring the firing atmosphere introduced into the furnace into contact with the entire surface of the laminate 13 as much as possible, but by providing a sufficient space under the laminate 13, In addition, the firing atmosphere can be easily brought into contact. Therefore, as the setter 12, when the laminated body 13 after degreasing is placed, the setter 12 is provided with unevenness that can provide sufficient space under the laminated body 13, and specifically, the setter 12 is used. As shown in FIG. 6, a material having a ratio A / B of 15% or more of the volume A of the space under the laminated body 13 formed by the unevenness of the setter 12 and the volume B of the laminated body 13 is used. Here, the space below the stacked body 13 formed by unevenness is the surface of the stacked body 13 facing the setter 12 and the setter 12 when the state in which the stacked body 13 is placed on the setter 12 is viewed in plan view. This is the space sandwiched by the mounting surface. When the ratio A / B is less than 15%, contact with the firing atmosphere is hindered on the back surface side of the laminated body 13, resulting in deterioration of piezoelectric characteristics. Further, removal of residual carbon on the back side of the laminate 13 may be hindered, resulting in problems such as a delay in sintering, cracking, and melting of the internal electrode layer 3. In addition, it is more preferable from the viewpoint of obtaining the effects of the present invention, such as prevention of occurrence of cracks, as the ratio A / B is increased. However, if the ratio A / B exceeds 100%, it becomes difficult to support the laminated body. Therefore, the ratio A / B may be appropriately set in consideration of this point.

  The unevenness of the stacked body mounting surface of the setter 12 is formed by, for example, a plurality of grooves 14 parallel to each other, as shown in FIGS. By arranging the plurality of grooves 14 as unevenness in equilibrium with each other, the atmosphere in the mortar 11 can be efficiently supplied under the laminate 13 through the space in the grooves 14. Moreover, the residual carbon component gasified from the back surface of the laminated body 13 can be quickly moved in the lateral direction through the inside of the groove 14 passing under the laminated body 13. Therefore, residual carbon can be removed more efficiently.

  The shape of the plurality of parallel grooves 14 forming the unevenness is not limited to the triangular shape as shown in FIGS. 5 and 6, and the space where the ratio A / B is 15% or more under the laminate 13. Can be arbitrarily set, for example, a cross-sectional arc shape, a cross-sectional rectangular shape, or the like. Moreover, the depth of the groove | channel 14 which forms an unevenness | corrugation, a pitch, etc. can also be set arbitrarily.

  Further, the shape of the unevenness formed on the mounting surface of the setter 12 is parallel to each other as described above as long as it gives a space under the laminate 13 such that the ratio A / B is 15% or more. The shape is not limited to the plurality of grooves 14, and may be any shape such as a protrusion.

  Examples of the material of the setter 12 include zirconia and magnesia. The unevenness of the setter 12 can be formed by machining the surface of a flat plate such as zirconia or magnesia, for example.

  The firing step is preferably performed in a reducing atmosphere in order to suppress oxidation of the metal contained as the raw material of the internal electrode layer 3. When firing in a reducing atmosphere, cracking and internal electrode elution are serious problems because it is difficult to decompose and remove residual carbon that could not be removed in the degreasing process, but the ratio A / B is within the scope of the present invention during firing. By using the setter which becomes, it is possible to obtain the advantage of performing firing in a reducing atmosphere while solving the above-mentioned problems. The reducing atmosphere refers to the oxide that the ceramic precursor layer contains as a raw material of the ceramic layer (piezoelectric layer 2), and the internal electrode precursor layer contains the raw material of the internal electrode layer 3 as described in the degreasing step. An atmospheric gas having an oxygen partial pressure in which a metal can coexist.

Further, in the firing step, when the temperature in the furnace exceeds 100 ° C., a predetermined atmosphere gas with an oxygen partial pressure adjusted within the range represented by the following formula (3) is introduced, whereby a firing atmosphere is obtained. May be controlled to the reducing atmosphere. The predetermined atmospheric gas contains, for example, an inert gas (such as nitrogen or Ar), hydrogen, and water vapor. By introducing the atmospheric gas when the temperature in the furnace exceeds 100 ° C. in the firing step, oxidation and elution of the internal electrode layer 3 can be suppressed without performing complicated control.
10 ¹⁰ × Kp ² ≦ P (O ₂ ) ≦ 10 ¹⁴ × Kp ² (3)
[Wherein, Kp represents the dissociation equilibrium constant of water. The unit of oxygen partial pressure P (O ₂ ) is Pa. ]

  The baking temperature may be set higher than the degreasing temperature, for example, 900 ° C. to 1000 ° C.

  On the other hand, as shown in FIG. 4 and FIG. The mortar 11 is used for the purpose of preventing composition deviation of the ceramic material. However, when the mortar 11 is fired in a sealed state, the carbon component evaporated from the laminate 13 is not discharged out of the mortar 11, so that cracks are generated. Problems such as sintering delay and melting of the internal electrode layer occur. In addition, when firing a laminate containing lead as a raw material, PbO produced by evaporation forms a PbO atmosphere in the mortar, but PbO usually has a molecular weight and stays at the bottom of the mortar. The PbO concentration may become excessively high at the bottom of the bowl, and PbO may precipitate on the surface or grain boundary of the multilayer ceramic element.

  Therefore, an open portion 23 that communicates the inside and the outside is provided in a part of the bowl 11. By providing the open portion 23, problems such as generation of cracks due to the carbon component evaporated from the laminate, a delay in sintering, and elution of the internal electrode layer can be solved. Further, when the ceramic material contains lead, excess PbO vapor can be discharged out of the mortar 11 through the open portion 23.

  The open portion 23 can be formed by displacing the upper lid 22 with respect to the container 21 or the like, but is formed by arranging a spacer 24 between the upper surface of the opening end of the container 21 and the upper lid 22. It is preferable. In this case, the open portion 23 is provided on the side surface of the mortar 11. The spacer 24 may be separate from or integral with the container 21 or the upper lid 22. In the present embodiment, an example in which substantially cubic spacers 24 are arranged at the four corners of the open end of the container 21 has been shown, but the shape, the arrangement location, the number of arrangements, and the like of the spacers can be arbitrarily set.

  The open rate of the mortar 11 is preferably 0.5% to 30%. The open ratio of the mortar is the area ratio of the open part to all the surfaces of the upper surface, the lower surface and the four side surfaces when the mortar is a hexahedron such as a rectangular parallelepiped. It is. If the open rate of the mortar 11 is less than 0.5%, cracks may occur or the internal electrodes may be eluted. On the other hand, when the open ratio exceeds 30%, cracks and elution of internal electrodes may occur, lead or the like may excessively evaporate, and the composition of the multilayer ceramic element may deviate from a desired value.

  It is preferable that the occupation ratio of the laminated body 13 which is a to-be-fired object in the mortar 11 is 20% to 80%. The occupation ratio of the laminated body 13 in the mortar 11 refers to the ratio of the total volume of the laminated body 13 accommodated to the volume of the mortar 11. By setting the occupation ratio within the above range, deviation of the composition of the multilayer ceramic element can be reliably suppressed, and the firing atmosphere can be smoothly supplied to the entire interior of the mortar 11. If the occupation ratio is less than 20%, the evaporation of lead per volume of the multilayer body 13 increases, and the characteristics of the multilayer ceramic element may be deteriorated. On the other hand, if the occupation ratio exceeds 80%, the reducing atmosphere gas flowing from the outside of the mortar 11 becomes difficult to come into contact with the individual laminates 13, and there is a possibility that the characteristics are also deteriorated. In addition, the more preferable range of an occupation rate is 20%-60%, and a higher effect can be acquired by setting it as the said range.

  The bowl may be formed entirely of the same material, or may be formed of a different material for each part. Examples of the material include alumina, zirconia, and magnesia.

According to the manufacturing method as described above, the setter having the ratio A / B of 15% or more is used in the firing step in combination with the mortar provided with the open portion, whereby the atmosphere in the furnace and the atmosphere in the mortar It is possible to perform firing while appropriately exchanging and to make the atmosphere in the furnace in good contact with the back side of the laminate. Therefore, in the laminated ceramic device obtained, it is possible to prevent degradation properties such as piezoelectric constant d _33. Moreover, since the carbon component removed from the laminated body from the open part provided in the mortar can be discharged out of the mortar, the occurrence of cracks, elution of internal electrodes, and the like can be reliably suppressed.

The present invention is particularly effective when a large laminate is to be fired, and is particularly effective when the volume B of the laminate is 20 mm ³ or more.

  By the way, in the above description, a case where a setter having a ratio A / B of 15% or more is used only in the firing step is described as an example. However, the setter is preferably used also in the degreasing step. By using a setter that ensures a sufficient space under the laminate during degreasing, the decomposition and removal of organic components on the setter side of the laminate proceeds smoothly, and the amount of residual carbon in the laminate is greatly reduced. Can do. For this reason, it is possible to suppress problems such as delay in ceramic sintering, generation of cracks, elution of internal electrodes, and the like.

  Moreover, when the setter is used in the degreasing step, the setter in a state where the laminate is placed after the degreasing step is accommodated in a mortar and the firing step may be started. That is, it is not necessary to replace the laminate on the setter of the present invention after the degreasing step, and the production efficiency can be improved.

  However, when the degreasing is performed, if the setter and the laminate are in surface contact, the carbon component tends to remain on the contact surface of the laminate with the setter. It is preferable that there is substantially no flat portion at the tip. By using a setter having no substantially flat portion at the tip of the convex portion in contact with the laminated body for degreasing, it is possible to reliably prevent occurrence of defects such as generation of cracks and elution of internal electrodes.

  FIG. 7 is a view showing a contact state between the setter 12 and the laminated body 13, but it is assumed that there is substantially no flat portion at the tip of the convex portion 14 in contact with the laminated body 13 of the setter 12. When the unevenness on the mounting surface is formed as a plurality of grooves 14 that are parallel to each other, the width of the flat portion in the convex portion 15 between the grooves 14 is 0.5 mm or less.

  In the above description, the multilayer piezoelectric element is given as a main example as the multilayer ceramic element, but it goes without saying that the present invention can be applied to all other methods for manufacturing multilayer ceramic elements.

Examples to which the present invention is applied will be described below.
<Examination of ratio A / B>
(Sample 1)
PbO, ZrO ₂ , TiO ₂ , SrCO ₃ , ZnO, Nb ₂ O ₅ , Ta ₂ O ₅ were used as raw materials, and a predetermined amount of each of these raw material powders was weighed to obtain material powders. This material powder was wet-mixed by a ball mill for 16 hours, dried, and calcined at 700 ° C. to 900 ° C. for 2 hours in an air atmosphere. Thereafter, it was further wet-ground by a ball mill for 16 hours and dried to obtain a ceramic precursor powder. This ceramic precursor powder was mixed with an acrylic binder, a solvent and the like to form a slurry, and a green sheet (ceramic precursor layer) was formed by a doctor blade method.

On the other hand, an ethyl cellulose binder, a solvent and the like were mixed with metal copper powder to form a paste, and printed on the green sheet so as to have a thickness of less than 1 to 2 μm. After printing, 300 green sheets were laminated and thermocompression bonded under conditions of 80 ° C. and 1 ton / cm ² , and cut into 7 × 7 × 30 mm to obtain a green laminate.

100 green laminates were placed on a zirconia setter, inserted into an Inconel tubular furnace, and held at 550 ° C. for 32 hours for degreasing. In the degreasing process, a mixed gas in which water vapor was added to N ₂ and H ₂ was introduced into the furnace as an atmospheric gas so that the oxygen partial pressure at which the metal copper and lead oxide can coexist at the degreasing temperature. As the setter, a plurality of grooves parallel to each other are formed on the mounting surface of the green laminate, and the ratio A between the volume A of the space below the laminate formed by the grooves and the volume B of the laminate / B is 15%, and a flat portion having a width exceeding 0.5 mm does not exist at the tip of the convex portion between the grooves.

After the degreasing treatment, firing was performed. In firing, first, a plurality of grooves parallel to each other are formed on the mounting surface of the green laminate, and the ratio between the volume A of the space below the laminate formed by the grooves and the volume B of the laminate The degreased laminate is placed on a setter in which A / B is 24% and there is no flat part having a width exceeding 0.5 mm at the tip of the convex part between the grooves, and this setter is placed in the bowl. installed. Moreover, the opening rate of the mortar was set to 5% by installing a spacer having a predetermined thickness between the upper lid of the mortar and the frame. The mortar was inserted into an Inconel tubular furnace and fired by holding at 950 ° C. for 2 hours to obtain a multilayer ceramic element. At the time of firing, a mixed gas in which water vapor was added to N ₂ and H ₂ was introduced into the furnace as an atmospheric gas so that an oxygen partial pressure at which the metallic copper and lead oxide could coexist at the firing temperature.

(Sample 2)
The laminated body after the degreasing treatment was placed in the mortar together with the setter used in the degreasing treatment, and the firing was performed. Otherwise, a multilayer ceramic element was obtained in the same manner as Sample 1.

(Sample 3)
The laminated body after the degreasing treatment is replaced with a setter having the ratio A / B of 7% by changing the depth and width of the groove, and the firing is performed in a state where the setter is installed in the mortar. went. Otherwise, a multilayer ceramic element was obtained in the same manner as Sample 1.

(Sample 4)
The laminated body after the degreasing treatment was transferred to a flat plate-like setter in which no groove was formed, and the firing was performed in a state where the setter was installed in the mortar. Otherwise, a multilayer ceramic element was obtained in the same manner as Sample 1.

(Sample 5)
The laminated body after the degreasing treatment was placed in the mortar together with the setter used in the degreasing treatment, and the firing was performed. At this time, the mortar was sealed without using the spacer. Otherwise, a multilayer ceramic element was obtained in the same manner as Sample 1.

The appearance of the multilayer ceramic elements of the above samples 1 to 5 was visually observed to check for cracks and internal electrode elution. Moreover, about the sample which did not have a problem in appearance, after polishing both sides by sandblast, Cu and Ag were vacuum-deposited to form an electrode, and 2.5 kV / mm for 5 minutes in 150 ° C. silicone oil. Polarization treatment was performed. The sample 2.0 kV / mm, performs voltage measurement of the displacement amount by引加of 0.1 Hz, displacement, number of layers, measurement of the piezoelectric constant _{d 33} from the voltage.

As is evident from Table 1, it showed samples 1 and 2 high piezoelectric properties d ₃₃ of greater than 700pC / N In using setter as the ratio A / B during calcination treatment of 15% or more. In addition, no problem in appearance was observed in the obtained multilayer ceramic element. In contrast, in the sample 3 using a setter such that the sample 4 and the ratio A / B was used tabular setter less than 15%, the piezoelectric characteristics d ₃₃ is below the 700pC / N is a measure of the characteristic. Further, from the comparison between sample 2 and sample 5, when firing with the mortar in a sealed state, the internal electrode is eluted by the reaction of Cu of the internal electrode and the metallized Pb, and the appearance of the sintered body is increased. A malfunction occurred. Therefore, from this experiment, a good characteristic is exhibited by using a combination of a mortar with an open part in part and a setter in which the ratio A / B is 15% or more. It was confirmed that a multilayer ceramic element can be manufactured.

<Examination of mortar opening rate>
(Samples 6-9)
The laminated body after the degreasing treatment was placed in the mortar together with the setter used in the degreasing treatment, and the firing was performed. At this time, by changing the thickness of the spacer, the open rate of the mortar was set to the value shown in Table 2. Otherwise, a multilayer ceramic element was obtained in the same manner as Sample 1.

  About the above samples 6-9, the external appearance test | inspection after baking and the piezoelectric characteristic were investigated. The results are shown in Table 2. Table 2 also shows the results of Sample 5 and Sample 2.

  As is apparent from Table 2, when the open rate of the mortar exceeded 30%, cracks occurred (Sample 9). Therefore, from this experiment, it was confirmed that the preferable range of the mortar opening rate is 0.5% to 30%.

It is a schematic perspective view which shows an example of a laminated ceramic element. It is a schematic sectional drawing which shows an example of the lamination | stacking state of a piezoelectric material layer and an internal electrode layer. It is a figure which shows the oxygen dissociation curve of copper and lead. (A) is a disassembled perspective view which shows the mortar used in a baking process, (b) is a perspective view of the state which mounted the upper cover. (A) is a schematic plan view which shows the relationship between the container of a mortar, a setter, and a laminated body in a baking process, (b) is a schematic sectional drawing. It is a principal part schematic sectional drawing which shows the relationship between the setter and laminated body in a baking process. It is a principal part expanded sectional view of a setter.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Laminated piezoelectric element, 2 Ceramic layer (piezoelectric layer), 3 Internal electrode layer, 4 Laminated body, 5 Inactive piezoelectric layer area | region, 11 Bowl, 12 Setter, 13 Laminated body, 14 Groove, 15 Convex part, 21 Container , 22 Top cover, 23 Open part, 24 Spacer

Claims (11)

After degreasing the laminate in which the ceramic precursor layer containing the raw material of the ceramic layer and the internal electrode precursor layer containing the raw material of the internal electrode layer are alternately laminated, it is housed in a pot with a part of the open portion provided A method for producing a multilayer ceramic element that is fired in a state where
The laminate is housed in the mortar in a state of being placed on a setter,
The setter has an unevenness on the mounting surface on which the laminate is placed, and the ratio A / of the volume A of the space under the laminate formed by the unevenness to the volume B of the laminate. B is 15% or more, The manufacturing method of the laminated ceramic element characterized by the above-mentioned.   The method for manufacturing a multilayer ceramic element according to claim 1, wherein a plurality of grooves parallel to each other are formed as the unevenness on the mounting surface of the setter.   The said mortar includes a container having an upper surface opened and an upper lid, and the open portion is formed by a spacer disposed between the open end of the container and the upper lid. The manufacturing method of the multilayer ceramic element as described in description.   The method for producing a multilayer ceramic element according to any one of claims 1 to 3, wherein an opening rate of the mortar is 0.5% to 30%.   5. The method for manufacturing a multilayer ceramic element according to claim 1, wherein an occupation ratio of the multilayer body in the mortar is 20% to 80%.   The method for manufacturing a multilayer ceramic element according to claim 1, wherein the firing is performed in a reducing atmosphere. The ceramic precursor layer includes an oxide as the raw material, and the internal electrode precursor layer includes a metal as the raw material,
The method for producing a multilayer ceramic element according to claim 6, wherein an atmosphere gas having an oxygen partial pressure in which the oxide and the metal can coexist is used as the reducing atmosphere. The method for manufacturing a multilayer ceramic element according to claim 1, wherein the volume of the multilayer body is 20 mm ³ or more.   The method for manufacturing a multilayer ceramic element according to claim 1, wherein the ceramic precursor layer contains lead oxide as the raw material, and the internal electrode precursor layer contains copper as the raw material. .   10. The method for manufacturing a multilayer ceramic element according to claim 9, wherein the ceramic layer contains lead zirconate titanate as a ceramic, and the internal electrode layer is a copper electrode layer. The method for producing a multilayer ceramic element according to any one of claims 1 to 10, wherein the degreasing is performed using the setter.

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