JP2007189164A - Stacked piezoelectric element, process for fabrication thereof, and conductor paste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stacked piezoelectric element equipped with a terminal electrode having a high adhesion strength even under a low-temperature grazing. <P>SOLUTION: The stacked piezoelectric element comprises: a laminate consisting of a plurality of piezoelectric layers and an internal electrode layer formed between a plurality of piezoelectric layers; and a terminal electrode which is jointed to the laminate and electrically connects the internal electrode layer to an external power source. A compound containing alkaline earth metal is formed at the interface between the laminate and the terminal electrode. If the piezoelectric layer contains a composite oxide comprising Pb, Ti, and Zr, the compound containing alkaline earth metal further contains Pb. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multilayer piezoelectric element, and more particularly to improvement of a terminal electrode of the multilayer piezoelectric element.

  2. Description of the Related Art Conventionally, piezoelectric elements have been used as driving sources for various devices by utilizing the characteristic that electrical energy can be converted into mechanical energy by the inverse piezoelectric effect. A general piezoelectric element has a structure in which an electrode layer is formed by printing and baking a conductor paste on both surfaces of a piezoelectric layer such as lead zirconate titanate (PZT). However, since the amount of displacement obtained with a single piezoelectric layer is small, when a large amount of displacement is desired, the amount of displacement is increased by laminating the piezoelectric layer and the internal electrode layer. This is a multilayer piezoelectric element.

  FIG. 3 is a cross-sectional view illustrating a configuration example of the multilayer piezoelectric element 1. The multilayer piezoelectric element 1 includes a multilayer body 10 in which a plurality of piezoelectric layers 11 and a plurality of internal electrode layers 12 are alternately stacked. The thickness per layer of the piezoelectric layer 11 is, for example, 1 to 200 μm, preferably 20 to 150 μm. Note that the number of stacked piezoelectric layers 11 is determined according to the target displacement.

In general, the piezoelectric ceramic composition constituting the piezoelectric layer 11 is mainly composed of a composite oxide containing Pb, Ti and Zr as constituent elements.
The internal electrode layer 12 contains a conductive material. As a conductive material constituting the internal electrode layer 12, a noble metal such as Ag or an Ag—Pd alloy has been used. However, since the noble metal material is one of the factors that increase the cost of the multilayer piezoelectric element 1, it is attempted to use Cu, which is a base metal material, as a conductive material (for example, Patent Document 1 and Patent Document 2). ).

The plurality of internal electrode layers 12 are alternately extended in opposite directions, and a pair of terminal electrodes 21 and 22 electrically connected to the internal electrode layer 12 are provided in the extension direction. The terminal electrodes 21 and 22 are electrically connected to an external power source (not shown) via a lead wire (not shown), for example.
The terminal electrodes 21 and 22 are formed by applying and then baking a conductive paste containing a conductive material such as Ag, Cu or Pd, a glass composition and an organic vehicle. Although the thickness of the terminal electrodes 21 and 22 is suitably determined according to a use etc., it is 10-50 micrometers normally.

JP 2004-137106 A JP-A-2005-285806

  When a noble metal such as Ag or Ag—Pd alloy was used as the conductive material of the internal electrode layer 12, the temperature for baking the terminal electrodes 21 and 22 could be made relatively high, for example, about 700 ° C. This is because noble metals such as Ag and Ag—Pd alloy hardly diffuse into the piezoelectric layer 11 even at such a temperature. Therefore, as the glass used for the conductor paste for the terminal electrodes 21 and 22, Pb-based or Zn-based glass having a melting point of about 700 ° C. can be used, and adhesion to the laminate 10 is also ensured.

However, when Cu is used as the conductive material of the internal electrode layer 12, it is necessary to lower the baking temperature as compared with the prior art. This is because Cu easily diffuses into the piezoelectric layer 11. Therefore, when the conductive material of the internal electrode layer 12 is Cu, conventional Pb-based and Zn-based glasses cannot be used.
On the other hand, the multilayer piezoelectric element 1 is attracting attention as an electronic component of a high-speed response next-generation automobile engine fuel injection control device. The multilayer piezoelectric element 1 used for this purpose is required to have a large number of stacked layers of several hundred layers and a size of about 10 mm × 10 mm × height of about 40 mm. Furthermore, the multilayer piezoelectric element 1 for this application is continuously driven under a high electric field and high pressure, and has strong adhesion so that the terminal electrodes 21 and 22 do not peel from the multilayer body 10 (piezoelectric material). Is required.
The present invention has been made on the basis of such a technical problem, and an object of the present invention is to provide a multilayer piezoelectric element including a terminal electrode having high adhesion strength even by low-temperature baking. Moreover, an object of this invention is to provide the electrically conductive paste for obtaining such a terminal electrode.

  The adhesion strength of the terminal electrode to the piezoelectric material is governed by the glass contained together with the conductive material. This glass is included for bonding a conductive material to a piezoelectric material. Therefore, the present inventors examined the components of the glass. As a result, when glass contains a specific element, a compound containing the element is formed on the surface of the piezoelectric material after baking, and the terminal electrode is bonded to the piezoelectric material through this compound layer. I found out. And when the terminal electrode was joined to the piezoelectric material through this compound, the adhesion strength was excellent.

  The multilayer piezoelectric element of the present invention is based on the above study, and is bonded to the multilayer body including a plurality of piezoelectric layers and internal electrode layers formed between the plurality of piezoelectric layers, A terminal electrode that electrically connects the internal electrode layer and an external power source is provided, and a compound containing an alkaline earth metal is formed at the interface between the laminate and the terminal electrode. The compound containing an alkaline earth metal is preferably formed in a layered manner at the interface between the laminate and the terminal electrode. In addition, as long as the compound is formed in a layered form, the concentration does not necessarily need to be uniform, and the present invention includes a case where the concentration is uneven.

In the multilayer piezoelectric element of the present invention, when the piezoelectric layer contains a composite oxide containing Pb, Ti and Zr as constituent elements, the compound containing an alkaline earth metal preferably further contains Pb.
In the multilayer piezoelectric element of the present invention, the compound containing an alkaline earth metal is one or two selected from Ba ₂ PbO ₄ , BaPbO ₃ , Ca ₂ PbO ₄ , CaPbO ₃ , Sr ₂ PbO ₄ and SrPbO _3. It is preferable that it is a seed or more.
The multilayer piezoelectric element of the present invention is particularly effective when the conductive material of the internal electrode layer is Cu.

The multilayer piezoelectric element according to the present invention described above includes a multilayer body including a plurality of piezoelectric layers and internal electrode layers formed between the plurality of piezoelectric layers, and the internal electrode layer and an external power source joined to the multilayer body. A method for producing a laminated piezoelectric element comprising a terminal electrode for electrically connecting a piezoelectric layer precursor and an internal electrode layer precursor in a laminated state to obtain a laminate by firing And forming a terminal electrode in a predetermined region of the laminate, and the formation of the terminal electrode includes a conductive material, glass, and an organic vehicle, and the glass contains Bi ₂ O ₃ : 57 to 87% by mass, B ₂ O ₃ : 0.5 to 12% by mass, SiO ₂ : 18% by mass or less (excluding 0), ZnO: 6 to 17% by mass, Al ₂ O ₃ : 17% by mass or less (provided that 0 1) or 2 or more types selected from BaO, CaO and SrO : 13 wt% or less (including not a 0) the terminal electrode precursor having a composition of coating a predetermined region of the stack, and then are prepared by baking.
In the present invention, when the internal electrode layer contains Cu as a conductive material, it is recommended to fire in a reducing atmosphere.

The above paste containing glass is effective in addition to terminal electrode formation. Accordingly, the present invention includes a conductive material, glass, and an organic vehicle, and the glass contains Bi ₂ O ₃ : 57 to 87% by mass, B ₂ O ₃ : 0.5 to 12% by mass, and SiO ₂ : 18% by mass or less. (However, 0 is not included), ZnO: 6 to 17% by mass, Al ₂ O ₃ : 17% by mass or less (however, 0 is not included), one or more selected from BaO, CaO, SrO The present invention also provides a conductor paste having a composition of 13% by mass or less (excluding 0).
In this conductor paste, it is preferable to use one or more kinds selected from Ag, Au, Cu, Ni, Pt and Pd as the conductive material.

  ADVANTAGE OF THE INVENTION According to this invention, the lamination type piezoelectric element provided with the terminal electrode which has high adhesive strength also by low temperature baking is provided. Moreover, according to this invention, the conductor paste which has high adhesive strength also by low temperature baking is provided.

  The basic configuration of the multilayer piezoelectric element 1 has already been described with reference to FIG. 3 and will not be described. Here, the manufacturing process of the multilayer piezoelectric element 1 will be described with reference to FIG. Explained. FIG. 4 is a flowchart showing the manufacturing process of the multilayer piezoelectric element 1.

First, as the main starting material for obtaining the piezoelectric layer 11, for example, PbO, TiO ₂ , ZrO ₂ , ZnO and Nb ₂ O ₅ or a compound that can be changed to these oxides by firing; SrO, BaO and CaO Powders such as at least one selected oxide or a compound that can be converted into these oxides by firing are prepared and weighed (step S101). As a starting material, not an oxide but a material that becomes an oxide by firing, such as carbonate or oxalate, may be used. As these raw material powders, those having an average particle diameter of about 0.5 to 10 μm are usually used.

If necessary, starting materials for subcomponents are prepared and weighed (step S101). As the starting material of the subcomponent, for example, at least one oxide selected from Ta ₂ O ₅ , Sb ₂ O ₃ , Nb ₂ O ₅ and WO ₃ or a compound that can be changed to these oxides by firing can be used. However, instead of an oxide, a material that becomes an oxide by firing, such as carbonate or oxalate, may be used. These subcomponents have the effect of improving the sinterability and lowering the firing temperature.

Subsequently, the starting materials of the main component and the subcomponent are wet pulverized and mixed using, for example, a ball mill to obtain a raw material mixture (step S102).
In addition, although the starting material of a subcomponent may be added before temporary baking (step S103) mentioned later, you may make it add after temporary baking. However, it is preferable to add it before calcination because a more uniform piezoelectric layer 11 can be produced. When added after calcination, it is preferable to use an oxide as a starting material for the auxiliary component.

Next, the raw material mixture is dried and, for example, pre-baked at a temperature of 750 to 950 ° C. for 1 to 6 hours (step S103). This pre-baking may be performed in the air, or may be performed in an atmosphere having a higher oxygen partial pressure or in a pure oxygen atmosphere than in the air. After calcination, for example, the calcination product is wet pulverized and mixed in a ball mill to obtain a calcination powder containing a main component and, if necessary, subcomponents (step S104).
Next, a binder is added to the temporarily fired powder to produce a piezoelectric layer paste (step S105). Specifically, it is as follows. First, a slurry is obtained by wet pulverization using, for example, a ball mill. At this time, water or an alcohol such as ethanol or a mixed solvent of water and ethanol can be used as a solvent for the slurry. The wet pulverization is preferably performed until the average particle size of the calcined powder becomes about 0.5 to 2.0 μm.

  The resulting slurry is then dispersed in an organic vehicle. The organic vehicle is obtained by dissolving a binder in an organic solvent, and the binder used in the organic vehicle is not particularly limited, and may be appropriately selected from usual various binders such as ethyl cellulose, polyvinyl butyral, and acrylic. Also, the organic solvent used at this time is not particularly limited, and it is appropriately selected from organic solvents such as terpineol, butyl carbitol, acetone, toluene, MEK (methyl ethyl ketone), terpineol and the like depending on the method used, such as printing method and sheet forming method. Just choose.

The content of the organic vehicle in the paste is not particularly limited, and may be a normal content, for example, about 5 to 10% by mass for the binder and about 10 to 50% by mass for the solvent. Moreover, the paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like, as necessary.
The same organic vehicle may be used for the internal electrode layer paste and the terminal electrode paste.

  When the piezoelectric layer paste is used as a water-based paint, a water-based vehicle in which a water-soluble binder, a dispersant, or the like is dissolved in water and a pre-fired powder may be kneaded. The water-soluble binder used for the water-based vehicle is not particularly limited, and for example, polyvinyl alcohol, cellulose, water-soluble acrylic resin, or the like may be used.

Also, an internal electrode layer paste is prepared (step S106).
The internal electrode layer paste is prepared by kneading Cu particles as a conductive material and the above-described organic vehicle.

Also, a terminal electrode paste is prepared (step S107).
The terminal electrode paste includes a conductive material, glass, and an organic vehicle. In this, glass plays a role of joining the terminal electrodes 21 and 22 to the laminate 10. The organic vehicle is added for preparing a paste.
As the conductive material, particles composed of one kind or two or more kinds selected from conventionally used Ag, Au, Cu, Ni, Pt and Pd can be used. This conductive material may be an alloy of the above elements. What is necessary is just to select the particle size of this particle | grain suitably from the range of 0.1-3.0 micrometers. The amount of the conductive material in the terminal electrode paste is preferably in the range of 50 to 85% by mass. If it is less than 50% by mass, the amount of metal is too small, fading may occur, and there may be a region that does not contact the internal electrode layer 12. Moreover, when it exceeds 85 mass%, it will become impossible to paste. A more preferable amount of the conductive material in the terminal electrode paste is 70 to 80% by mass.

The present invention is characterized by the composition of the glass contained in the terminal electrode paste. This glass has the following composition. If each compound is out of the following range, the necessary adhesion strength cannot be obtained as shown in the examples described later.
Bi ₂ O _3: 57~87 wt%
B ₂ O _3: 0.5~12 wt%
SiO ₂ : 18% by mass or less (excluding 0)
ZnO: 6 to 17% by mass
Al ₂ O ₃ : 17% by mass or less (excluding 0)
1 type or 2 types or more selected from BaO, CaO, SrO: 13 mass% or less (however, 0 is not included)

A preferred glass composition is as follows.
Bi ₂ O _3: 60~85 wt%
B ₂ O _3: 1~10 wt%
SiO ₂ : 15% by mass or less (excluding 0)
ZnO: 8 to 15% by mass
Al ₂ O ₃ : 15% by mass or less (however, 0 is not included)
One or more selected from BaO, CaO, SrO: 10% by mass or less (excluding 0)

A more preferable glass composition is as follows.
Bi ₂ O _3: 65~75 wt%
B ₂ O _3: 4~8 wt%
SiO ₂ : 0.3 to 10% by mass
ZnO: 10 to 15% by mass
Al ₂ O ₃ : 0.2 to 10% by mass
One or more selected from BaO, CaO and SrO: 0.1 to 8% by mass

  The amount of glass in the terminal electrode paste is preferably in the range of 3 to 20% by mass. If it is less than 3% by mass, sufficient adhesion to the laminate 10 cannot be ensured. Moreover, when it exceeds 20 mass%, glass will inhibit sintering of a conductive material, and sufficient electroconductivity cannot be provided to the terminal electrodes 21 and 22. The more preferable amount of glass in the terminal electrode paste is 5 to 15% by mass.

  In the above, the piezoelectric layer paste, the internal electrode layer paste, and the terminal electrode paste are produced in order, but it goes without saying that they may be produced in parallel or in the reverse order.

Next, a green chip (laminated body) to be fired is manufactured using the above paste (step S108).
When producing a green chip using a printing method, a piezoelectric layer paste is printed a plurality of times on a substrate such as polyethylene terephthalate at a predetermined thickness, and as shown in FIG. The body layer 11a is formed. Next, the internal electrode layer paste is printed in a predetermined pattern on the green outer piezoelectric layer 11a to form a green internal electrode layer (internal electrode layer precursor) 12a. Next, on the internal electrode layer 12a in the green state, the piezoelectric layer paste is printed a plurality of times with a predetermined thickness in the same manner as described above to form the piezoelectric layer (piezoelectric layer precursor) 11b in the green state. To do. Next, the internal electrode layer paste is printed in a predetermined pattern on the green piezoelectric layer 11b to form the green internal electrode layer 12b. The internal electrode layers 12a, 12b,... In the green state are formed so as to be opposed to each other and exposed at different end surfaces. The above operation is repeated a predetermined number of times. Finally, the piezoelectric layer paste is printed a predetermined number of times with a predetermined thickness on the green internal electrode layer 12 to form the green outer piezoelectric layer 11c. Form. Then, it pressurizes and pressure-bonds, heating, cut | disconnects to a predetermined shape, and is set as a green chip (laminated body).
In the above, an example in which a green chip is manufactured by a printing method has been described. However, a green chip can also be manufactured by using a sheet forming method.

Next, the binder removal process is performed on the green chip (step S109).
In the binder removal process, the atmosphere needs to be determined by the conductive material in the internal electrode layer precursor. When a noble metal is used as the conductive material, the binder removal may be performed in the air, or may be performed in an atmosphere having a higher oxygen partial pressure than in the air or a pure oxygen atmosphere. However, when using Cu as a conductive material, it is necessary to consider oxidation, and heating in a reducing atmosphere should be employed. On the other hand, it is necessary to consider that an oxide contained in the piezoelectric layer precursor, such as PbO, is reduced in the binder removal process. For example, when Cu is used as the conductive material, the equilibrium oxygen partial pressure of Cu and Cu ₂ O (hereinafter simply referred to as equilibrium oxygen partial pressure of Cu) and the equilibrium oxygen partial pressure of Pb and PbO (hereinafter simply referred to as equilibrium oxygen partial pressure of Pb). Based on the above, it is preferable to set what reducing atmosphere is applied to the binder removal treatment.

  If the temperature of the binder removal process is less than 300 ° C., the binder removal cannot be performed smoothly, and if it exceeds 650 ° C., the effect of the binder removal corresponding to the temperature cannot be obtained and energy is wasted. The binder removal time needs to be determined depending on the temperature and atmosphere, but can be selected in the range of 0.5 to 50 hours. Further, the binder removal treatment can be performed independently of the firing and can be performed continuously with the firing. In the case where the firing is continuously performed, the binder removal process may be performed in the firing temperature increasing process.

After the binder removal process, firing (step S110) is performed.
As with the binder removal, the atmosphere needs to be determined by the conductive material in the internal electrode layer precursor.
The firing temperature needs to be appropriately determined according to the piezoelectric ceramic composition constituting the piezoelectric layer 11. When using a piezoelectric ceramic composition that can be fired at a low temperature, it can be carried out in a range of 800 to 1200 ° C. The firing temperature is determined on the premise that a dense sintered body can be obtained and the conductive material constituting the internal electrode layer 12 is not melted.

The fired piezoelectric layer 11 preferably contains a composite oxide containing Pb, Ti and Zr as constituent elements. Examples of the composite oxide include, for example, lead titanate (PbTiO ₃ ), lead zirconate (PbZrO ₃ ), and zinc / lead niobate [Pb (Zn _1/3 Nb _2/3 ) O ₃ ]. Examples thereof include ternary composite oxides and composite oxides in which part of Pb in the ternary composite oxide is substituted with Sr, Ba, Ca, or the like.

  Specific examples of the composition include composite oxides represented by the following formula (1) or (2). In these formulas (1) and (2), the oxygen composition 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 (1)
(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 (2)
(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 composite oxide has a so-called perovskite structure, and Pb and the substitution element Me in the formula (2) are located at a so-called A site of the perovskite structure. Zn, Nb, Ti, and Zr are located at the so-called B site of the perovskite structure.

  In the composite oxide represented by the formula (1) or formula (2), the ratio a of the A site element is preferably 0.96 ≦ a ≦ 1.03. If the A-site element ratio a is less than 0.96, firing at low temperatures may be difficult. On the contrary, when the ratio a of the A site element exceeds 1.03, the density of the obtained piezoelectric ceramic composition is lowered, and as a result, sufficient piezoelectric characteristics may not be obtained, and the mechanical strength is also lowered. There is a fear. A more preferable A-site element ratio a is 0.98 ≦ a ≦ 1.01, and a more preferable A-site element ratio a is 0.99 ≦ a ≦ 1.005.

  In the composite oxide represented by the above formula (2), a part of Pb is substituted with the substitution element Me (Sr, Ca, Ba), but this can increase the piezoelectric strain constant. However, if the substitution amount b of the substitution element Me is too large, the sinterability is lowered, and as a result, the piezoelectric strain constant is reduced and the mechanical strength is also lowered. Also, the Curie temperature tends to decrease as the substitution amount b increases. Therefore, the substitution amount b of the substitution element Me is preferably 0.1 or less. A more preferable substitution amount b of the substitution element Me is 0.06 or less, and a more preferred substitution amount b of the substitution element Me is 0.04 or less.

  On the other hand, among the B site elements, the ratio x between Zn and Nb is preferably 0.05 ≦ x ≦ 0.15. The ratio x affects the firing temperature. If this value is less than 0.05, the effect of lowering the firing temperature may be insufficient. On the other hand, if it exceeds 0.15, the sinterability is affected. As a result, the piezoelectric strain constant may be reduced and the mechanical strength may be reduced. A more preferable ratio x of Zn and Nb is 0.06 ≦ x ≦ 0.125, and a more preferable ratio x of Zn and Nb is 0.08 ≦ x ≦ 0.1.

  Of the B-site elements, the Ti ratio y and the Zr ratio z are preferably set in terms of piezoelectric characteristics. Specifically, the Ti ratio y is preferably 0.25 ≦ y ≦ 0.5, and the Zr ratio z is preferably 0.35 ≦ z ≦ 0.6. By setting it within the above range, a large piezoelectric strain constant can be obtained in the vicinity of the morphotropic phase boundary (MPB). A more preferable Ti ratio y is 0.275 ≦ y ≦ 0.48, and a more preferable Ti ratio y is 0.3 ≦ y ≦ 0.45. A more preferable Zr ratio z is 0.375 ≦ z ≦ 0.55, and a more preferable Zr ratio z is 0.35 ≦ z ≦ 0.5.

The laminated body 10 manufactured through the above steps is subjected to end face polishing by, for example, barrel polishing or sand blasting, and the terminal electrodes 21 and 22 are formed by printing and baking the above-described terminal electrode paste (step S111).
The procedure of this process is shown in FIG.
After the terminal electrode paste is printed (step S201), the terminal electrode paste is dried, and then the binder is removed (step S202). The binder removal conditions can follow the conditions in the process of obtaining the laminate 10. However, since the laminated body 10 has already been baked, the oxidation of Cu is slight even if the binder is removed in an oxidizing property such as the atmosphere.
When the binder removal is performed in an oxidizing atmosphere, a reduction process is performed (step S203). In the process of removing the binder, it is assumed that a part of Cu constituting the internal electrode layer 12 is oxidized. Therefore, the reduction process is performed to return the metal Cu. The reduction treatment may be performed by heating and holding at 300 to 500 ° C. in a reducing gas atmosphere such as a mixed gas atmosphere of hydrogen and an inert gas.
After the reduction treatment, baking is performed. The baking may be held in an inert gas atmosphere at 500 to 600 ° C. for about 0.1 to 3 hours.
Thus, the multilayer piezoelectric element 1 shown in FIG. 3 can be obtained.

A piezoelectric ceramic composition was prepared by adding 1% by mass of Ta ₂ O ₅ as an auxiliary component to the following main components.
Main component: (Pb _0.992 Me _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

The piezoelectric ceramic composition was produced as follows. First, PbO powder, SrCO ₃ powder, BaCO ₃ powder, CaCO ₃ powder, ZnO powder, Nb ₂ O ₅ powder, TiO ₂ powder, and ZrO ₂ powder are prepared as the main component raw materials, and the composition of the main component is obtained. Weighed as follows. In the formula, Me is any one of Sr, Ba, and Ca. Next, these raw materials were wet mixed using a ball mill and calcined at 900 ° C. for 4 hours in the air.
The obtained calcined product was finely pulverized and then wet pulverized using a ball mill. After drying this, an acrylic resin was added as an organic vehicle for granulation, and pressure was applied at a pressure of 50 MPa using a uniaxial press molding machine to obtain a molded body having a diameter of 13 mm and a thickness of 1.5 mm. The binder was removed by holding the molded body at 350 ° C. for 10 minutes in the air, and then baking was performed at 900 ° C. for 8 hours in the air to obtain a substrate.

Moreover, the conductor paste was produced in the following procedures.
Conductive material powders (average particle size 0.6 μm) shown in Tables 1 to 8, glass powders and organic vehicles having the compositions shown in Tables 1 to 8 were prepared. Conductive material powder: 75% by mass, glass powder: 10% by mass, organic vehicle: remainder were mixed to obtain a conductor paste. Note that an alkaline resin was used as the organic vehicle.

As shown in FIG. 6, on the obtained substrate S ((Pb _0.992 Me _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃ ) After the conductor paste was printed and dried by screen printing, the binder was removed by holding in the atmosphere at 350 ° C. for 10 minutes. Next, after performing a reduction treatment that was held at 350 ° C. in a 4% H ₂ —N ₂ gas atmosphere for 30 minutes, baking was carried out at 560 ° C. in an N ₂ gas atmosphere for 10 minutes to form a conductor film C. In addition, the reduction process here was performed in order to confirm the reduction resistance of glass. When the glass is reduced to become a metal, the adhesiveness is not ensured.

Next, an L-shaped Cu wire W plated with Sn was soldered on the conductor film C as shown in FIG. While pulling the Cu wire W in the direction indicated by the arrow in FIG. 6 at a speed of 10 mm / min, the strength when the conductor film C peeled from the substrate S was measured as the adhesion strength. The results are shown in Tables 1-8. In addition, the material of the board | substrate S used for the measurement of Tables 1-8 is as follows.
Tables 1 to 6: (Pb _0.992 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃
Table 7: (Pb _0.992 Ba _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃
Table 8: (Pb _0.992 Ca _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃
Further, after the conductor film C is peeled off, the product on the substrate S is identified by X-ray diffraction, and the production of Ba ₂ PbO ₄ , BaPbO ₃ , Ca ₂ PbO ₄ , CaPbO ₃ , Sr ₂ PbO ₄ , SrPbO ₃ is identified. The presence or absence was confirmed. The results are shown in Tables 1-6.

As shown in Table 1, when the glass composition was outside the range of the present invention (No. 1 to 11), no adhesion strength was obtained. On the other hand, when the glass composition is within the range of the present invention (Nos. 12 to 29), an adhesion strength of 15 N or more, further 20 N or more is obtained, and sufficient adhesion as a terminal electrode of the multilayer piezoelectric element. Was found to be obtained.
As a result of X-ray diffraction although high adhesion strength is obtained, Ba ₂ PbO ₄ or BaPbO ₃ is formed on the substrate S when the glass contains BaO. When the glass contains CaO, Ca ₂ PbO ₄ or CaPbO ₃ is generated on the substrate S. Further, when the glass contains SrO, Sr ₂ PbO ₄ or SrPbO ₃ is formed on the substrate S. On the other hand, in the case where the adhesion strength was not obtained, the production of Ba ₂ PbO ₄ or BaPbO ₃ was not confirmed despite containing BaO. It is understood that the substrate S and the glass did not react because the glass was crystallized.

From the above results, the compound containing the alkaline earth metal element (Ba, Ca, Sr) is generated, thereby ensuring the adhesion of the conductive layer to the substrate S made of the piezoelectric material. Further, the product contains Pb in addition to the alkaline earth metal elements (Ba, Ca, Sr), and this Pb is an element contained in the substrate S, and the alkaline earth metal in the glass. It is understood that the compound (Ba, Ca, Sr) and Pb contained in the substrate S reacted to form the compound.
Further, as shown in Tables 2 to 8, the same results as above were obtained even when the conductive material was other than Ag.

An organic vehicle was added to the piezoelectric ceramic composition powder obtained by pulverizing the calcined product obtained in Example 1, and kneaded to prepare a piezoelectric layer paste. At the same time, Cu powder as a conductive material was kneaded with an organic vehicle to produce an internal electrode layer paste. Subsequently, a green chip, which is a precursor of the multilayer body, was produced by a printing method using the piezoelectric layer paste and the internal electrode layer paste. The number of stacked layers is 20, the thickness of each piezoelectric layer is 70 μm, and the thickness of each internal electrode layer is 3 μm. Furthermore, binder removal processing was performed, and firing was performed under reducing firing conditions to obtain a laminate. As reducing firing conditions, firing was performed for 8 hours at a firing temperature of 900 ° C. under a reducing atmosphere (oxygen partial pressure of 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁶ atm).

A terminal electrode was formed on the obtained laminate. The terminal electrode paste is No. 1 in Table 1 of Example 1. 13 glasses were used. The terminal electrode was formed in the same manner as in Example 1.
The piezoelectric characteristics of the obtained multilayer piezoelectric element were evaluated. In the evaluation, the capacitance C, resonance frequency fr, and antiresonance frequency fa of the element were obtained from an impedance analyzer, and the piezoelectric strain constant d33 was obtained. As a result, it was 700 pc / N, and good piezoelectric characteristics were obtained.
In addition, X-ray diffraction was performed on the interface between the terminal electrode and the laminate, and the cross section of the interface was observed by SEM (Scanning Electron Microscope) and EPMA (Electron Probe Micro-Analyzer). The X-ray diffraction chart is shown in FIG. 1, and the SEM and EPMA observation results are shown in FIG. As shown in FIG. 1, it was found that Ba ₂ PbO ₄ was generated by X-ray diffraction. Moreover, it can be seen from the element mapping image by EPMA in FIG. 2 that Ba and Pb are segregated in layers between the terminal electrode and the laminate. In addition, Ba seems to be scattered because a specific portion with a particularly large amount of compound is emphasized. However, this is merely that the concentration of Ba is not uniform, and the segregation in layers is not changed. The above X-ray diffraction and element mapping of EPMA specify that Ba ₂ PbO ₄ exists in a layered manner between the terminal electrode and the laminate.

3 is an X-ray diffraction chart of an interface between a terminal electrode and a laminate in the present example. It is a figure which shows the elemental mapping image by the SEM image and EPMA of the interface cross section of the terminal electrode and laminated body in a present Example. It is a figure which shows one structural example of the lamination type piezoelectric element in this Embodiment. It is a flowchart which shows the manufacture procedure of the lamination type piezoelectric element in this Embodiment. It is a flowchart which shows the formation procedure of the terminal electrode in this Embodiment. It is a figure which shows the measuring method of the adhesive strength of the electrically conductive film in a present Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laminated piezoelectric element, 10 ... Laminated body, 11 ... Piezoelectric layer, 12 ... Internal electrode layer, 21, 22 ... Terminal electrode

Claims (9)

A laminate including a plurality of piezoelectric layers and an internal electrode layer formed between the plurality of piezoelectric layers;
A terminal electrode joined to the laminate and electrically connecting the internal electrode layer and an external power source;
A multilayer piezoelectric element, wherein a compound containing an alkaline earth metal is formed at an interface between the multilayer body and the terminal electrode. The piezoelectric layer includes a composite oxide having Pb, Ti and Zr as constituent elements,
2. The multilayer piezoelectric element according to claim 1, wherein the compound containing an alkaline earth metal further contains Pb. The alkaline earth metal-containing compound is one or more selected from Ba ₂ PbO ₄ , BaPbO ₃ , Ca ₂ PbO ₄ , CaPbO ₃ , Sr ₂ PbO ₄ and SrPbO _3. The multilayer piezoelectric element according to claim 1 or 2.   The multilayer piezoelectric element according to claim 1, wherein the conductive material of the internal electrode layer is Cu.   The multilayer piezoelectric element according to claim 1, wherein the compound containing the alkaline earth metal is formed in a layered manner at an interface between the multilayer body and the terminal electrode. A laminate including a plurality of piezoelectric layers and an internal electrode layer formed between the plurality of piezoelectric layers;
A method of manufacturing a multilayer piezoelectric element comprising a terminal electrode joined to the multilayer body and electrically connecting the internal electrode layer and an external power source,
Firing the piezoelectric layer precursor and the internal electrode layer precursor in a laminated state to obtain the laminate;
Forming a terminal electrode in a predetermined region of the laminate, and
The formation of the terminal electrode includes a conductive material, glass and an organic vehicle,
The glass is
Bi ₂ O _3: 57~87 wt%,
B ₂ O _3: 0.5~12 wt%,
SiO ₂ : 18% by mass or less (excluding 0),
ZnO: 6 to 17% by mass,
Al ₂ O ₃ : 17% by mass or less (however, not including 0),
A terminal electrode precursor having a composition of one or more selected from BaO, CaO, and SrO: 13 mass% or less (excluding 0) is applied to a predetermined region of the laminate, and then baked. A method for manufacturing a laminated piezoelectric element, characterized in that   The method for manufacturing a multilayer piezoelectric element according to claim 6, wherein the internal electrode layer includes Cu as the conductive material and is fired in a reducing atmosphere. Including conductive materials, glass and organic vehicles,
The glass is
Bi ₂ O _3: 57~87 wt%,
B ₂ O _3: 0.5~12 wt%,
SiO ₂ : 18% by mass or less (excluding 0),
ZnO: 6 to 17% by mass,
Al ₂ O ₃ : 17% by mass or less (however, not including 0),
A conductor paste having a composition of one or more selected from BaO, CaO, and SrO: 13% by mass or less (excluding 0).   The conductive paste according to claim 8, wherein the conductive material is one or more selected from Ag, Au, Cu, Ni, Pt and Pd.

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