JP4640092B2 - Multilayer piezoelectric element and method for manufacturing the same - Google Patents

Description

  The present invention relates to a piezoelectric ceramic composition suitable for piezoelectric layers of various piezoelectric elements such as actuators, piezoelectric buzzers, sounding bodies, sensors, etc., and in particular, a piezoelectric layer of a stacked piezoelectric element using Cu as an internal electrode. And a multilayer piezoelectric element using the composition.

A piezoelectric ceramic composition used for a piezoelectric element is required to have a large piezoelectric characteristic, particularly a piezoelectric strain constant. As a piezoelectric ceramic composition satisfying this characteristic, it is composed of, for example, lead titanate (PbTiO ₃ ), lead zirconate (PbZrO ₃ ), and lead zinc niobate [Pb (Zn _1/3 Nb _2/3 ) O ₃ ]. A ternary piezoelectric ceramic composition, a piezoelectric ceramic composition in which a part of Pb in the ternary piezoelectric ceramic composition is replaced with Sr, Ba, Ca or the like has been developed.
However, these conventional piezoelectric ceramic compositions need to be fired at a relatively high temperature, and since firing is performed in an oxidizing atmosphere, for example, a multilayer piezoelectric element that simultaneously fires internal electrodes has a high melting point. Therefore, it is necessary to use a noble metal (for example, Pt, Pd, etc.) that is not oxidized even when fired in an oxidizing atmosphere. As a result, the cost is increased and the cost of the manufactured multilayer piezoelectric element is hindered.

  In such a situation, the applicant of the present application includes a first subcomponent including at least one selected from Fe, Co, Ni, and Cu in the ternary piezoelectric ceramic composition, and Sb, Nb, and Ta. It is proposed that low temperature firing is possible by adding a second subcomponent containing at least one selected from the above, and that an inexpensive material such as an Ag—Pd alloy can be used for the internal electrode (Patent Document 1). reference).

  The invention described in Patent Document 1 includes the ternary piezoelectric ceramic composition and the piezoelectric ceramic composition in which part of Pb is replaced with Sr, Ba, Ca, etc. in the ternary piezoelectric ceramic composition. By adding a first subcomponent containing at least one selected from Co, Ni, and Cu and a second subcomponent containing at least one selected from Sb, Nb, and Ta, it has a high piezoelectric strain constant and has a low temperature. Realizes a piezoelectric ceramic composition that is densified without impairing various piezoelectric properties even when fired at a high pressure and has improved mechanical strength, and provides a piezoelectric element having a piezoelectric layer composed of the piezoelectric ceramic composition. That's it.

JP 2004-137106 A

  In order to provide a cheaper piezoelectric element, for example, it is conceivable to use Cu, which is cheaper than an Ag—Pd alloy, as the conductive material of the internal electrode. However, when Cu is used as the conductive material for the internal electrode, it has been found that the piezoelectric strain characteristic, which is important as the characteristic of the piezoelectric element, is deteriorated. Accordingly, an object of the present invention is to provide a piezoelectric ceramic composition in which the piezoelectric strain characteristics do not deteriorate even when Cu is used as a conductive material for an internal electrode. Another object of the present invention is to provide a laminated piezoelectric element using such a piezoelectric ceramic composition and a method for producing the same.

The present inventors investigated the cause of the decrease in the piezoelectric strain characteristics when Cu was used as the conductive material for the internal electrode, and confirmed that Cu was diffused from the internal electrode to the piezoelectric layer. Therefore, the present inventors understand that the diffusion of Cu into the piezoelectric layer is the cause of the deterioration of the piezoelectric strain characteristics. Accordingly, the present inventors have revealed that examined subcomponent to be added to the piezoelectric ceramic composition, M g, by trace additives of component containing at least one selected from C o and Ga as an auxiliary component, Cu is Even when diffused in the piezoelectric layer, high piezoelectric characteristics can be maintained. Surprisingly, it has been found that by specifying the added amounts of these subcomponents, it is possible to obtain a very special effect in that higher piezoelectric strain characteristics are exhibited when Cu diffuses than when Cu does not diffuse.
The present invention is based on the above knowledge, and is mainly composed of a composite oxide having Pb, Ti and Zr as constituent elements, and at least selected from M g , Co and Ga as the first subcomponent with respect to the main component. A plurality of piezoelectric layers containing 0.5% by mass or less (excluding 0) in terms of oxide, and an internal electrode layer formed between the plurality of piezoelectric layers and containing Cu as a conductive material; And a laminated piezoelectric element.
In the present invention, the main component is (Pb _ab Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃ (where 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, Me is selected from Sr, Ca, and Ba It is assumed to be composed of a complex oxide represented by at least one kind.
This multilayer piezoelectric element can obtain high piezoelectric strain characteristics even when Cu contained in the internal electrode diffuses into the piezoelectric layer.

In the piezoelectric ceramic composition of the present invention, as the second subcomponent, Ta, Sb, at least one less 1.0 wt% in terms of oxide selected from Nb and W (note that 0 is not included.) Containing It is preferable.

In addition, the multilayer piezoelectric element according to the present invention includes a step of obtaining a laminate in which a piezoelectric layer precursor containing a composite oxide and an internal electrode precursor containing Cu are laminated, and this laminate is reduced. It can manufacture by passing through the baking process baked in atmosphere. Firing in a reducing atmosphere is preferably performed at a firing temperature of 800 ° C. to 1200 ° C. and an oxygen partial pressure of 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁶ atm.

  As described above, according to the present invention, a piezoelectric ceramic composition having a high piezoelectric strain characteristic, for example, an electromechanical coupling coefficient kr, is provided even when an inexpensive metal material such as Cu is used as a conductive material for an internal electrode. Is possible. Therefore, according to the present invention, it is possible to provide a piezoelectric element that is excellent in piezoelectric characteristics, particularly a multilayer piezoelectric element, while being inexpensive. In particular, according to the present invention, when Cu diffuses into the piezoelectric layer, there is a unique effect that the piezoelectric strain characteristics are improved.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is a cross-sectional view showing a configuration example of a multilayer piezoelectric element 1 obtained by the present invention. Note that FIG. 1 is merely an example, and it goes without saying that the present invention is not limited to the multilayer piezoelectric element 1 of FIG. 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, and more preferably 50 to 100 μm. Note that the number of stacked piezoelectric layers 11 is determined according to the target displacement.

The piezoelectric ceramic composition constituting the piezoelectric layer 11 is mainly composed of a composite oxide containing Pb, Ti and Zr as constituent elements. Examples of the composite oxide include lead titanate (PbTiO ₃ ), lead zirconate (PbZrO ₃ ), and zinc niobate [Pb (Zn _1/3 Nb _2/3 ) O ₃ ]. It is a ternary complex oxide or a complex oxide obtained by substituting a part of Pb with Sr, Ba, Ca, or the like in the ternary complex oxide.

  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 _ab 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 other hand, if the ratio a of the A-site element exceeds 1.03, the density of the obtained piezoelectric ceramic decreases, and as a result, sufficient piezoelectric characteristics may not be obtained, and the mechanical strength may also decrease. is there. A more preferable A-site element ratio a is 0.97 ≦ a ≦ 1.02, and a more preferable A-site element ratio a is 0.98 ≦ a ≦ 1.01.

  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 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 preferred substitution amount b of the substitution element Me is 0.005 ≦ b ≦ 0.08, and a more preferred substitution amount b of the substitution element Me is 0.007 ≦ b ≦ 0.05.

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 0.07 ≦ x ≦ 0.13, and a more preferable ratio x of Zn and Nb is 0.08 ≦ x ≦ 0.12.

  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 0.3 ≦ y ≦ 0.48, and a more preferable Ti ratio y is 0.4 ≦ y ≦ 0.46. A more preferable Zr ratio z is 0.37 ≦ z ≦ 0.55, and a more preferable Zr ratio z is 0.4 ≦ z ≦ 0.5.

The piezoelectric ceramic composition of the present invention, as a sub-component (the first subcomponent), M g, at least one kind of oxide selected from C o and Ga (M gO, C oO, Ga 2 O 3) in terms of 0 0.5 mass% or less (however, 0 is not included). By including this first subcomponent, high piezoelectric strain characteristics can be obtained even when Cu as the electrode material diffuses into the piezoelectric layer. The amount of the first subcomponent added is preferably 0.03 to 0.4 mass% and more preferably 0.08 to 0.35 mass% in terms of oxide. Among the first subcomponents, Mg and Ga are preferable for obtaining high piezoelectric strain characteristics, and Mg is particularly preferable.

The piezoelectric ceramic composition of the present invention may contain other subcomponents in addition to the subcomponents in addition to the main components. In this case, the subcomponent (second subcomponent) is at least one selected from Ta, Sb, Nb and W. By adding the subcomponent, the piezoelectric characteristics and the mechanical strength can be improved. However, the content of these subcomponents is preferably 1.0% by mass or less in terms of oxide. For example, Ta is 1.0% by mass or less in terms of Ta ₂ O ₅ , Sb is 1.0% by mass or less in terms of Sb ₂ O ₃ , and Nb is 1.0% by mass in terms of Nb ₂ O _5. Hereinafter, in the case of W, it is 1.0 mass% or less in terms of WO ₃ . If the content of the subcomponent exceeds 1.0% by mass in terms of oxide, the sinterability may be reduced and the piezoelectric characteristics may be deteriorated. A more preferable content is 0.05 to 0.8% by mass, and a more preferable content is 0.1 to 0.5% by mass.

The internal electrode layer 12 contains a conductive material. The present invention uses Cu as the conductive material. When Cu is used as the conductive material, it is beneficial for low-temperature firing at 1050 ° C. or lower, for example.
The plurality of internal electrode layers 12 are alternately extended in opposite directions, for example, 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 may be formed by sputtering Cu, for example, or may be formed by baking terminal electrode paste. Although the thickness of the terminal electrodes 21 and 22 is suitably determined according to a use etc., it is 10-50 micrometers normally.

  Next, a preferred method for manufacturing the multilayer piezoelectric element 1 will be described with reference to FIG. FIG. 2 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). The starting materials of the first subcomponent, M gO, C oO, may be at least one oxide selected from Ga ₂ O _3. However, instead of an oxide, a material that becomes an oxide by firing, such as carbonate or oxalate, may be used. As the starting material for the second subcomponent, at least one oxide selected from Ta ₂ O ₅ , Sb ₂ O ₃ , Nb ₂ O ₅ and WO ₃ can be used. As described above, instead of an oxide, a material that becomes an oxide by firing, such as carbonate or oxalate, may be used. These second 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 form 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 may be appropriately selected from organic solvents such as terpineol, butyl carbitol, acetone, toluene, MEK (methyl ethyl ketone), and terpineol depending on the method used, such as a printing method and a sheet forming method. Just choose.

  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 the various conductive materials described above or various oxides, organometallic compounds, resinates, and the like, which become the conductive materials described above after firing, and the above-described organic vehicle.

  In the firing step described later, Cu contained in the internal electrode layer paste diffuses into the piezoelectric layer 2 formed by firing the piezoelectric layer paste. In this diffusion, the particle size of Cu contained in the internal electrode layer paste affects the diffusion amount. When the particle size of Cu contained in the internal electrode layer paste is large, the amount of diffusion increases, and when the particle size of Cu is small, the amount of diffusion decreases. In order not to lower the piezoelectric strain characteristics, it is desirable that the amount of diffusion of Cu is small. Therefore, it is desirable that the particle size of Cu contained in the internal electrode layer paste is as small as possible.

The terminal electrode paste is prepared in the same manner as the internal electrode layer paste (step S107).
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.

  The content of the organic vehicle in each 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. Each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like as necessary.

Next, a green chip (laminated body) to be fired is manufactured using the above paste (step S108).
When producing a green chip by using a printing method, a piezoelectric layer paste is printed a plurality of times on a substrate such as polyethylene terephthalate with a predetermined thickness, 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, it 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. 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 Cu equilibrium oxygen partial pressure) and the equilibrium oxygen partial pressure of Pb and PbO (hereinafter simply referred to as Pb equilibrium oxygen partial pressure). It is preferable to set what reducing atmosphere is applied to the binder removal process based on the above.

  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.
The multilayer piezoelectric element 1 is preferably fired under reducing firing conditions. When the multilayer piezoelectric element 1 is manufactured, if it is fired in an oxidizing atmosphere, for example, a noble metal needs to be used as the electrode material of the internal electrode layer 12. On the other hand, since the multilayer piezoelectric element 1 is fired under reducing firing conditions, inexpensive Cu can be used for the internal electrode layer 12 in the present invention. Here, the reducing firing conditions are, for example, a firing temperature of 800 ° C. to 1200 ° C. and an oxygen partial pressure of 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁶ atm.
When the firing temperature is less than 800 ° C., the firing does not proceed sufficiently, and when it exceeds 1200 ° C., there is a concern about melting of Cu. A preferable baking temperature is 850 to 1100 ° C, and a more preferable baking temperature is 900 to 1050 ° C.
If the oxygen partial pressure is less than 1 × 10 ⁻¹⁰ atm, an oxide contained in the piezoelectric layer precursor, such as PbO, is reduced and deposited as metal Pb, which may lower the piezoelectric properties of the finally obtained fired body. If the pressure exceeds 1 × 10 ⁻⁶ atm, there is a concern about oxidation of Cu as an electrode material. A preferable oxygen partial pressure is 10 ⁻⁹ to 10 ⁻⁷ atm, and a more preferable oxygen partial pressure is 10 ⁻⁸ to 10 ⁻⁷ atm.

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 or baking the above-described terminal electrode paste (step S111). In addition to printing or baking, the terminal electrodes 21 and 22 can also be formed by sputtering.
As described above, the multilayer piezoelectric element 1 shown in FIG. 1 can be obtained.

  The multilayer piezoelectric element 1 is manufactured using Cu for the internal electrode layer 12, and the piezoelectric layer 11 near the internal electrode layer 12 is analyzed by TEM-EDS (field-emission type transmission electron microscope with energy dispersive X-ray spectroscopy). Went. FIG. 3 shows the result of point analysis by TEM image and EDS. It was confirmed that Cu was present at the triple points and grain boundaries of the piezoelectric layer 11 and diffused from the internal electrode layer 12 during the firing process.

Hereinafter, the present invention will be described based on specific examples.
<First embodiment>
An experiment in which the effect of adding the first subcomponent (MgO) was confirmed will be described as a first example.
In this experiment, Mg was added to the following main components so as to have an amount shown in Table 1 in terms of MgO, and the effect was examined.
Main component: (Pb _0.995-0.03 Sr _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, ZnO powder, Nb ₂ O ₅ powder, TiO ₂ powder, and ZrO ₂ powder were prepared as raw materials for the main component, and weighed so as to have the composition of the main component. Further, MgO was prepared as an additive species of Mg, and added to the main component matrix composition so as to have the contents shown in Table 1. Next, these raw materials were wet-mixed for 16 hours using a ball mill, and calcined at 700 to 900 ° C. for 2 hours in the air.
The obtained calcined product was finely pulverized and then wet pulverized for 16 hours using a ball mill. After drying this, an acrylic resin was added as a binder for granulation, and it was formed into a disk shape having a diameter of 17 mm and a thickness of 1 mm using a uniaxial press molding machine at a pressure of about 445 MPa. After molding, a Cu paste containing Cu powder having a particle size of 1.0 μm was printed on both sides. The obtained pellets were heat-treated to volatilize the binder and fired at 950 ° C. for 8 hours in a low oxygen reducing atmosphere (oxygen partial pressure 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁶ atm). The obtained sintered body was formed into a disk shape having a thickness of 0.6 mm by slicing and lapping, and the printed Cu paste was removed and processed into a shape capable of characteristic evaluation. A silver paste was printed on both surfaces of the obtained sample and baked at 350 ° C., and an electric field of 3 kV was applied in 120 ° C. silicone oil for 15 minutes to carry out polarization treatment. Further, a sample was prepared in which the polarization treatment was performed in the same manner as described above except that Cu paste printing and heat treatment for binder volatilization were not performed.

  The electromechanical coupling coefficient kr (%) was measured for the six types of samples prepared. The electromechanical coupling coefficient kr was measured using an impedance analyzer (HP4194A, manufactured by Hewlett-Packard Company). The results are shown in Table 1. FIG. 4 shows the relationship between the added amount of Mg (MgO) and the electromechanical coupling coefficient kr (%).

  As shown in Table 1 and FIG. 4, when Cu paste is not printed, the electromechanical coupling coefficient kr is reduced by adding MgO, whereas when Cu paste is printed, MgO is added. As a result, the electromechanical coupling coefficient kr is improved. Therefore, when a laminated piezoelectric element using Cu as a conductive material for the internal electrode is manufactured, even if diffusion of Cu described above into the piezoelectric layer occurs, the electromechanical coupling coefficient kr can be increased by adding MgO. It is easily understood that it can be improved. Therefore, according to the present invention, it is possible to reduce the cost by using Cu as the electrode material, and to improve the electromechanical coupling coefficient kr.

  FIG. 5 shows SEM images of a sample (left side) subjected to Cu paste printing and a sample (right side) added with 0.1% by mass of MgO and subjected to Cu paste printing. From the comparison between the two, it is understood that the addition of MgO promotes grain growth and increases the electromechanical coupling coefficient kr even in the presence of Cu.

<Second embodiment>
Samples were prepared in the same manner as in the first example except that a and Mg were added to the following main components so as to have the amounts shown in Table 2 in terms of MgO. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 2.
Main component: (Pb _a-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As shown in Table 2, in the sample subjected to Cu paste printing, when a is in the range of 0.96 to 1.03, an electromechanical coupling coefficient kr of 60% or more can be obtained.

<Third embodiment>
A sample was prepared in the same manner as in the first example except that b and Mg were added to the following main components so as to have the amounts shown in Table 3 in terms of MgO. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 3.
Main component: (Pb _0.995-b Sr _b ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As shown in Table 3, it is understood that the electromechanical coupling coefficient kr is improved by substituting Pb of the main component with Sr, and the substitution amount (molar ratio) of Sr is preferably 0.1 or less. .

<Fourth embodiment>
Samples were prepared in the same manner as in the first example, except that Me was added to the following main components so that Me was an element shown in Table 4 and the amount shown in Table 4 was added. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 4.
Main component: (Pb _0.995-0.03 Me _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As shown in Table 4, when Ca or Ba is used as a substitution element for Pb, the effect of improving the electromechanical coupling coefficient kr, which is the effect of containing MgO, can be enjoyed similarly to Sr.

<Fifth embodiment>
Samples were prepared in the same manner as in the first example except that x, y and z were set to the values shown in Table 5 and Mg was added so as to have the amounts shown in Table 5 in terms of MgO. Was made. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 5.
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃

  As is clear from Table 5, the effect of adding MgO can be obtained even when x, y, and z of the B site element are changed, and the electromechanical coupling coefficient kr is higher when the Cu paste is printed. I understand that. However, if x, y, and z are out of the ranges of 0.05 ≦ x ≦ 0.15, 0.25 ≦ y ≦ 0.5, and 0.35 ≦ z ≦ 0.6, respectively, the electromechanical coupling coefficient kr ( %) Becomes smaller.

<Sixth embodiment>
Respect to the main component of the following, in terms of MgO to Mg as an auxiliary component, also except for adding Ta so that the amount shown in Table 6 Ta ₂ O ₃ in terms of the sample in the same manner as in the first embodiment Produced. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 6.
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

As shown in Table 6, by adding Ta ₂ O ₃ as a subcomponent (second subcomponent), the electromechanical coupling coefficient kr can be improved, and the effect of adding MgO can be obtained, and a Cu paste is printed. In this case, it can be seen that the electromechanical coupling coefficient kr becomes high. However, if the amount of Ta ₂ O ₃ added is too large, the electromechanical coupling coefficient kr will decrease.

<Seventh embodiment>
Samples were prepared in the same manner as in the first example except that subcomponents (first subcomponent and second subcomponent) were added to the following main components so as to have the amounts shown in Table 7. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 7.
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

As shown in Table 7, the electromechanical coupling coefficient kr can be improved by adding Sb ₂ O ₃ , Nb ₂ O ₅ , and WO ₃ as subcomponents (second subcomponents), and the effect of adding MgO It can be seen that the electromechanical coupling coefficient kr increases when the Cu paste is printed. However, if the added amount of these subcomponents is too large, the electromechanical coupling coefficient kr is lowered.

<Eighth embodiment>
A sample was prepared in the same manner as in the first example except that Co was added in an amount equivalent to the CoO shown in Table 8 instead of MgO with respect to the following main components. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 8. FIG. 6 shows the relationship between the amount of Co (CoO) added and the electromechanical coupling coefficient kr (%).
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As shown in Table 8 and FIG. 6, when the Cu paste is not printed, the electromechanical coupling coefficient kr is reduced by the addition of CoO, whereas when the Cu paste is printed, the addition of CoO is performed. As a result, the electromechanical coupling coefficient kr is improved. Therefore, when a laminated piezoelectric element using Cu as the conductive material for the internal electrode is manufactured, even if the above-described diffusion of Cu into the piezoelectric layer occurs, the electromechanical coupling coefficient kr is increased by adding CoO. The improvement can be easily understood. Therefore, according to the present invention, it is possible to reduce the cost by using Cu as the electrode material, and to improve the electromechanical coupling coefficient kr.

<Ninth embodiment>
Samples were prepared in the same manner as in the first example except that a and Co were added to the following main components so as to have the amounts shown in Table 9 in terms of CoO. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 9.
Main component: (Pb _a-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As shown in Table 9, even in a sample subjected to Cu paste printing, an electromechanical coupling coefficient kr of 60% or more can be obtained when a is in the range of 0.96 to 1.03.

<Tenth embodiment>
Samples were prepared in the same manner as in the first example except that b and Co were added to the following main components so as to have the amounts shown in Table 10 in terms of CoO. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 10.
Main component: (Pb _0.995-b Sr _b ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As shown in Table 10, it is found that the electromechanical coupling coefficient kr is improved by substituting Pb as the main component with Sr, and that the substitution amount (molar ratio) of Sr is preferably 0.1 or less. .

<Eleventh embodiment>
Samples were prepared in the same manner as in the first example except that Me was added to the following main components so that Me was an element shown in Table 11 and Mg was added in an amount shown in Table 11 in terms of MgO. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 11.
Main component: (Pb _0.995-0.03 Me _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As shown in Table 11, even when Ca or Ba is used as the substitution element for Pb, the effect of improving the electromechanical coupling coefficient kr, which is the effect of containing CoO, can be enjoyed similarly to Sr.

<Twelfth embodiment>
Samples were prepared in the same manner as in the first example, except that x, y and z were set to the values shown in Table 12 and Co was added so as to have the amounts shown in Table 12 in terms of CoO. Was made. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 12.
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃

  As is clear from Table 12, the effect of adding CoO is obtained even when x, y, and z of the B site element are changed, and the electromechanical coupling coefficient kr is greater when Cu paste is printed. It turns out that it becomes high. However, when x, y, and z are out of the respective ranges, the electromechanical coupling coefficient kr (%) becomes small.

<Thirteenth embodiment>
Samples were prepared in the same manner as in the first example, except that subcomponents (first subcomponent and second subcomponent) were added to the following main components so as to have the amounts shown in Table 13. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 13.
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

As shown in Table 13, by adding Ta ₂ O ₃ as a subcomponent (second subcomponent), the electromechanical coupling coefficient kr can be improved, and the effect of adding CoO can be obtained, and a Cu paste is printed. In this case, it can be seen that the electromechanical coupling coefficient kr increases. However, if the amount of Ta ₂ O ₃ added is too large, the electromechanical coupling coefficient kr will decrease.

<14th embodiment>
A sample was prepared in the same manner as in the first example, except that subcomponents (first subcomponent and second subcomponent) were added to the following main components in amounts shown in Table 14. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 14.
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

As shown in Table 14, the electromechanical coupling coefficient kr can be improved by adding Sb ₂ O ₃ , Nb ₂ O ₅ , and WO ₃ as subcomponents (second subcomponents), and the effect of adding CoO It can be seen that the electromechanical coupling coefficient kr increases when the Cu paste is printed. However, if the added amount of these subcomponents is too large, the electromechanical coupling coefficient kr is lowered.

<Fifteenth embodiment>
A sample was prepared in the same manner as in the first example except that Ga was added in an amount equivalent to Ga ₂ O ₃ shown in Table 15 instead of MgO with respect to the following main components. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 15. FIG. 7 shows the relationship between the added amount of Ga (Ga ₂ O ₃ ) and the electromechanical coupling coefficient kr (%).
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

As shown in Table 15 and FIG. 7, when the Cu paste is not printed, the electromechanical coupling coefficient kr is reduced by the addition of Ga ₂ O ₃ , whereas when the Cu paste is printed. The addition of Ga ₂ O ₃ improves the electromechanical coupling coefficient kr. Therefore, when a laminated piezoelectric element using Cu as a conductive material for an internal electrode is manufactured, even if diffusion of Cu described above into the piezoelectric layer occurs, electromechanical coupling can be achieved by adding Ga ₂ O _3. It can be easily understood that the coefficient kr is improved. Therefore, according to the present invention, it is possible to reduce the cost by using Cu as the electrode material, and to improve the electromechanical coupling coefficient kr.

<Sixteenth embodiment>
Samples were prepared in the same manner as in the first example except that a and Ga were added to the following main components so as to have the amounts shown in Table 16 in terms of Ga ₂ O ₃ . For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 16.
Main component: (Pb _a-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As shown in Table 16, even in a sample subjected to Cu paste printing, an electromechanical coupling coefficient kr of around 60% or more can be obtained when a is in the range of 0.96 to 1.03.

<Seventeenth embodiment>
Samples were prepared in the same manner as in the first example, except that b and Ga were added to the following main components so as to have the amounts shown in Table 17 in terms of Ga ₂ O ₃ . For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 17.
Main component: (Pb _0.995-b Sr _b ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As shown in Table 17, it is understood that it is preferable that the electromechanical coupling coefficient kr is improved by substituting Pb of the main component with Sr, and that the substitution amount (molar ratio) of Sr is 0.1 or less. .

<Eighteenth embodiment>
A sample was prepared in the same manner as in the first example, except that Me was changed to an element shown in Table 18 and Ga was added in an amount shown in Table 18 in terms of Ga ₂ O ₃ with respect to the following main components. Produced. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 18.
Main component: (Pb _0.995-0.03 Me _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

  As shown in Table 18, even when Ca or Ba is used as a substitution element for Pb, the effect of improving the electromechanical coupling coefficient kr, which is the effect of containing CoO, can be enjoyed similarly to Sr.

<Nineteenth embodiment>
Samples were prepared in the same manner as in the first example except that x, y, and z were set to the values shown in Table 19 and Co was added so as to have the amounts shown in Table 19 in terms of CoO. Was made. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 19.
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃

  As is apparent from Table 19, even when x, y, and z of the B site element are changed, the effect of adding CoO is obtained, and when the Cu paste is printed, the electromechanical coupling coefficient kr is increased. Recognize. However, when x, y, and z are out of the respective ranges, the electromechanical coupling coefficient kr (%) becomes small.

<20th embodiment>
Samples were prepared in the same manner as in the first example except that subcomponents (first subcomponent and second subcomponent) were added to the following main components so as to have the amounts shown in Table 20. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 20.
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

As shown in Table 20, by adding Ta ₂ O ₃ as a subcomponent (second subcomponent), the electromechanical coupling coefficient kr can be improved, and the effect of adding CoO can be obtained, and a Cu paste is printed. In this case, it can be seen that the electromechanical coupling coefficient kr increases. However, if the amount of Ta ₂ O ₃ added is too large, the electromechanical coupling coefficient kr will decrease.

<Twenty-first embodiment>
Samples were prepared in the same manner as in the first example except that subcomponents (first subcomponent and second subcomponent) were added to the following main components so as to have the amounts shown in Table 21. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 21.
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

As shown in Table 21, the electromechanical coupling coefficient kr can be improved by adding Sb ₂ O ₃ , Nb ₂ O ₅ , and WO ₃ as subcomponents (second subcomponents), and Ga ₂ O ₃ is added. It can be seen that the electromechanical coupling coefficient kr increases when the Cu paste is printed. However, if the added amount of these subcomponents is too large, the electromechanical coupling coefficient kr is lowered.

<Twenty-second embodiment (reference example) >
Samples were prepared in the same manner as in the first example except that the subcomponents shown in Table 22 were added in the amounts shown in Table 22 instead of MgO with respect to the following main components. For the obtained sample, the electromechanical coupling coefficient kr was measured in the same manner as in the first example. The results are shown in Table 22 as a reference example .
Main component: (Pb _0.995-0.03 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃

<Twenty-third embodiment>
Among the samples listed in Table 1, it corresponds to a sample (comparative example) in which the content of Mg converted to MgO is 0% by mass and a sample (example) in which the content of Mg converted to MgO is 0.1% by mass. A laminated piezoelectric element as shown in FIG. 1 was produced using the powder before firing. The thickness of the piezoelectric layer 11 sandwiched between the internal electrode layers 12 was 25 μm, and the number of stacked layers was 100. The dimension of the laminated body 10 is 4 mm long × 4 mm wide. For the internal electrode layer 12, the same internal electrode Cu paste as that used in Example 1 was used, and firing was performed in a reducing atmosphere within the range recommended by the present invention. The displacement amount when a voltage of 43 V was applied to the obtained piezoelectric element was measured. The results are shown in Table 23.

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 figure which shows the point analysis result by the TEM image and EDS of the piezoelectric material layer of an internal electrode layer vicinity of the lamination type piezoelectric element obtained using Cu for an internal electrode layer. It is a graph which shows the relationship between the addition amount of Mg (MgO), and the electromechanical coupling coefficient kr (%). The SEM image of the sample which added 0.1 mass% of MgO and performed Cu paste printing is shown. It is a graph which shows the relationship between the addition amount of Co (CoO) and the electromechanical coupling coefficient kr (%). It is a graph showing the relationship between the Ga concentration of (Ga ₂ O ₃₎ and electromechanical coupling factor kr (%).

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 (5)

A composite oxide containing Pb, Ti, and Zr as constituent elements is a main component, and at least one selected from M g , Co, and Ga is 0.5 mass in terms of oxide as the first subcomponent for the main component. % Or less (however, 0 is not included) a plurality of piezoelectric layers,
An internal electrode layer formed between the plurality of piezoelectric layers and containing Cu as a conductive material;
And the main component is
(Pb _ab Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃
(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,
Me is composed of a composite oxide represented by at least one selected from Sr, Ca, and Ba).   The at least 1 sort (s) chosen from Ta, Sb, Nb, and W as a 2nd subcomponent is 1.0 mass% or less (however, 0 is not included) in conversion of an oxide, The claim 1 characterized by the above-mentioned. The laminated piezoelectric element described.   The multilayer piezoelectric element according to claim 1, wherein Cu contained in the internal electrode layer is diffused in the piezoelectric layer. A composite oxide containing Pb, Ti, and Zr as constituent elements is a main component, and at least one selected from M g , Co, and Ga is 0.5 mass in terms of oxide as the first subcomponent for the main component. % Of the piezoelectric layer including a plurality of piezoelectric layers (not including 0) and an internal electrode layer formed between the plurality of piezoelectric layers and containing Cu as a conductive material. Because
The main component is
(Pb _ab Me _b ) [(Zn _1/3 Nb _2/3 ) _x Ti _y Zr _z ] O ₃
(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,
Me is composed of a complex oxide represented by (at least one selected from Sr, Ca, Ba),
Obtaining a laminate in which a piezoelectric layer precursor containing the composite oxide and an internal electrode precursor containing Cu as a conductive material are laminated;
And a firing step of firing the laminate in a reducing atmosphere. Firing in the reducing atmosphere is
Firing temperature 800 ° C to 1200 ° C,
The method for producing a laminated piezoelectric element according to claim 4, wherein the method is performed at an oxygen partial pressure of 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁶ atm.

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