JP2007250606A - Method of evaluating piezoelectric magnetic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of evaluating piezoelectric characteristic of a laminated piezoelectric element by evaluating the piezoelectric characteristic as a piezoelectric magnetic device. <P>SOLUTION: In this method, the piezoelectric characteristic used for a piezoelectric material layer is measured under the condition that a piezoelectric magnetic device is independently provided in the laminated piezoelectric element, where a piezoelectric material layer including a piezoelectric ceramics and an internal electrode layer including a conductive material are laminated, and a conductive material is diffused into the piezoelectric material layer. The conductive material diffused into the piezoelectric material layer is included into the piezoelectric ceramics existing independently to measure the piezoelectric characteristic of the piezoelectric ceramics. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piezoelectric ceramic evaluation method that can be used for piezoelectric vibrators such as actuators, piezoelectric buzzers, sounding bodies, and sensors, and that is particularly suitable for laminated piezoelectric vibrators.

A piezoelectric ceramic used for a piezoelectric element is required to have a large piezoelectric characteristic, particularly a piezoelectric strain constant. As a piezoelectric ceramic satisfying this characteristic, for example, lead titanate (PbTiO ₃ ), lead zirconate (PbZrO ₃ ), and zinc niobate [Pb (Zn _1/3 Nb _2/3 ) O ₃ ] are configured. A ternary piezoelectric ceramic (so-called PZT), a piezoelectric ceramic in which a part of Pb is replaced with Sr, Ba, Ca or the like in the ternary piezoelectric ceramic have been developed.

  FIG. 1 is a cross-sectional view showing a configuration example of the multilayer piezoelectric element 1. In addition, FIG. 1 shows an example to the last. 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 number of stacked piezoelectric layers 11 is determined according to a target displacement amount.

The internal electrode layer 12 contains a conductive material. As this conductive material, Ag and Ag—Pd alloy are mainly used, and studies on using Cu for the purpose of cost reduction are in progress.
For example, 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 may be formed by sputtering Cu, for example, or may be formed by baking terminal electrode paste.

The laminated piezoelectric element 1 is integrally fired in a state where a piezoelectric layer precursor constituting the piezoelectric layer 11 and an internal electrode precursor constituting an internal electrode are laminated. In this firing process, there is a problem that the conductive material constituting the internal electrode layer 12 diffuses into the piezoelectric layer 11 and causes deterioration of piezoelectric characteristics and reliability.
To solve this problem, a technique for suppressing the diffusion of the conductive material into the piezoelectric layer 11 has been studied (for example, Patent Document 1 and Patent Document 2).

JP 2003-124766 A JP 2003-2011175 A

Although Patent Document 1 and Patent Document 2 can suppress the diffusion of the conductive material into the piezoelectric layer 11, the diffusion of the conductive material into the piezoelectric layer 11 cannot be completely eliminated. Therefore, when the piezoelectric ceramic for the multilayer piezoelectric element 1 is developed, for example, the piezoelectric characteristics of the piezoelectric ceramic itself constituting the piezoelectric layer 11 and the piezoelectric characteristics obtained as the multilayer piezoelectric element 1 are problematic. There is a considerable gap between them. In other words, the evaluation of only the piezoelectric characteristics of the piezoelectric ceramic could not predict the characteristics of the obtained multilayer piezoelectric element 1. This is a factor that impairs the speed of material development for piezoelectric ceramics.
The present invention has been made based on such a technical problem, and an object of the present invention is to provide a method capable of evaluating the piezoelectric characteristics of a laminated piezoelectric element by evaluating the piezoelectric characteristics as a piezoelectric ceramic.

As described above, the diffusion of the conductive material into the piezoelectric layer 11 cannot be completely eliminated. Therefore, the present inventors propose a piezoelectric ceramic evaluation method based on a novel idea of reproducing a state containing a conductive material in a piezoelectric ceramic that exists alone, like a piezoelectric layer of a multilayer piezoelectric element. Is. That is, the piezoelectric ceramic evaluation method of the present invention includes a piezoelectric material in a laminated piezoelectric element in which a piezoelectric layer including a piezoelectric ceramic and an internal electrode layer including a conductive material are stacked and the conductive material is diffused in the piezoelectric layer. This is a method for measuring the piezoelectric characteristics of a piezoelectric ceramic used for a layer in a state where the piezoelectric ceramic is present alone, and a piezoelectric material containing a conductive material diffused in the piezoelectric layer is contained in the piezoelectric ceramic. It is characterized by measuring the piezoelectric characteristics of the porcelain.
In the piezoelectric ceramic evaluation method of the present invention, an amount of a conductive material capable of obtaining the piezoelectric characteristics of the multilayer piezoelectric element is contained in the piezoelectric ceramic that exists alone. By doing so, the state in which the conductive material is diffused in the piezoelectric layer of the multilayer piezoelectric element can be accurately reproduced with a piezoelectric ceramic that exists independently. If the piezoelectric characteristics of the piezoelectric ceramic are measured, the measurement result can be regarded as equivalent to the piezoelectric characteristics that would be obtained for the laminated piezoelectric element.

There are at least two methods for incorporating a conductive material into the piezoelectric ceramic. One is that, like the piezoelectric layer of the multilayer piezoelectric element, a conductive material can be contained in the piezoelectric ceramic by diffusion. The other is that a conductive material can be contained in the piezoelectric ceramic by adding it as a raw material during the manufacturing process of the piezoelectric ceramic.
The conductive material contained in the piezoelectric ceramic is a metal contained in the internal electrode layer of the multilayer piezoelectric element, and can be Ag or Cu that diffuses into the piezoelectric layer during firing.

  As described above, according to the present invention, in a piezoelectric ceramic that exists alone, the state containing a conductive material can be reproduced in the same manner as the piezoelectric layer of the multilayer piezoelectric element. By measuring the piezoelectric characteristics, the piezoelectric characteristics as a multilayer piezoelectric element can be evaluated.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
First, in order to facilitate understanding of the present invention, a series of steps for manufacturing a multilayer piezoelectric element targeted by the present invention will be briefly described with reference to FIGS.
The piezoelectric layer 11 can be made of PZT, which is a Pb (Zr, Ti) O ₃ -based perovskite complex oxide. In the following description, it is assumed that the piezoelectric layer 11 is composed of PZT. As this starting material, for example, PbO, ZrO ₂ , TiO _2, or a powder of a compound that can be converted into these oxides by firing is prepared and weighed (step S101). As these raw material powders, those having an average particle diameter of about 0.5 to 10 μm are usually used. A part of Pb which is the A site component of the above formula or Zr and Ti which are the B site components can be substituted with other elements.

Subsequently, the starting material is wet pulverized and mixed using, for example, a ball mill to obtain a raw material mixture (step S102).
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 pulverized powder (step S104).

Next, a binder is added to the pulverized powder to produce a piezoelectric layer paste (step S105). For example, a slurry is obtained by wet grinding using a ball mill or the like. 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 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.

On the other hand, 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.
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.

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.

After the binder removal process, firing (step S110) is performed. During this firing process, the conductive material (Ag, Ag—Pd, Cu, etc.) in the internal electrode precursor diffuses into the piezoelectric layer 11. Depending on the conditions, the conductive material in the internal electrode precursor may diffuse into the piezoelectric layer 11 even in the binder removal process.
As with the binder removal, 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 a base metal as a conductive material, it is necessary to consider oxidation, and heating in a reducing atmosphere should be employed.
The firing temperature must be appropriately determined according to the piezoelectric ceramic constituting the piezoelectric layer 11. When a piezoelectric ceramic capable of low-temperature firing is used, it can be performed in the 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 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 schematic manufacturing process of the multilayer piezoelectric element 1 is as described above, and the conductive material constituting the internal electrode layer 12 diffuses into the piezoelectric layer 11 in the course of firing (step S110). According to the study by the present inventors, the piezoelectric characteristics may be improved in addition to the case where the piezoelectric characteristics are deteriorated due to diffusion of the conductive material into the piezoelectric layer 11. Here, the deterioration of the piezoelectric characteristic means that the characteristic of the piezoelectric ceramic in which the conductive material is diffused is lower than that of the piezoelectric ceramic in which the conductive material does not diffuse (piezoelectric layer 11). Also, the improvement in piezoelectric characteristics means that the characteristics of the piezoelectric ceramic in which the conductive material is diffused are higher than those in the piezoelectric ceramic in which the conductive material is not diffused. In any case, the characteristics of the piezoelectric ceramic fluctuate due to the diffusion of the conductive material. Therefore, even if the piezoelectric characteristics of the piezoelectric ceramic alone are simply measured, the piezoelectric characteristics as the multilayer piezoelectric element 1 Cannot be properly evaluated.

  Therefore, the present invention makes it possible to appropriately evaluate the piezoelectric characteristics of the multilayer piezoelectric element 1 based on the piezoelectric characteristics of the piezoelectric ceramic alone by performing predetermined measurements on the piezoelectric characteristics. This predetermined measurement is based on reproducing the diffusion state of the conductive material in the piezoelectric layer 11 and measuring the piezoelectric characteristics of the piezoelectric ceramic.

  In order to reproduce the diffusion state of the conductive material in the piezoelectric layer 11 for the piezoelectric ceramic, the piezoelectric characteristics of the multilayer piezoelectric element 1 are measured. The piezoelectric characteristics may be measured by a known method such as the piezoelectric constants d31 and d33.

Next, the existence state of the conductive material similar to that of the piezoelectric layer 11 is created for the piezoelectric ceramic that exists independently. There are at least two methods for including a conductive material in a piezoelectric ceramic. One is a method in which a conductive material is made to exist in the piezoelectric ceramic by diffusion like the piezoelectric layer 11. The other is a method of manufacturing a piezoelectric ceramic by adding a substance similar to the conductive material diffusing into the piezoelectric layer 11. As will be apparent from the examples described later, the present invention can be implemented by any method. When the conductive material is Ag or an Ag—Pd alloy, it is understood that Ag diffuses in the piezoelectric layer 11 and the diffused Ag is present in the piezoelectric layer 11 as Ag ₂ O. Further, when the conductive material is Cu, it is understood that Cu diffuses in the piezoelectric layer 11 and the diffused Cu exists in the piezoelectric layer 11 as Cu ₂ O.

  In the method in which the conductive material is present in the piezoelectric ceramic by diffusion, the concentration of the conductive material in the piezoelectric ceramic can be changed by changing the thickness of the piezoelectric ceramic. Actually, a plurality of types of piezoelectric ceramics having different thicknesses are produced, and a conductive material is diffused into the piezoelectric ceramics using the same composition as the internal electrode layer precursor. If it does so, the density | concentration of the electrically-conductive material in a piezoelectric ceramic will change with thickness. Piezoelectric characteristics are measured for a piezoelectric ceramic in which a conductive material is diffused. A piezoelectric ceramic having a piezoelectric characteristic that matches or approximates the piezoelectric characteristic of the multilayer piezoelectric element 1 measured in advance is extracted. It can be said that this piezoelectric ceramic reproduces the diffusion state of the conductive material of the piezoelectric layer 11 in the multilayer piezoelectric element 1. As will be described later, it was confirmed that when the concentration of the conductive material in the piezoelectric layer 11 of the multilayer piezoelectric element 1 and the concentration of the conductive material in the piezoelectric ceramic substantially matched, the piezoelectric constants of the two substantially matched. Therefore, the piezoelectric constant of the multilayer piezoelectric element 1 can be recognized by diffusing a conductive material and measuring the piezoelectric constant of the piezoelectric ceramic having the thickness.

  In the case where the same conductive material content as that of the piezoelectric layer 11 is reproduced by adding a conductive material, piezoelectric ceramics having various addition amounts of the conductive material are manufactured. Also in this case, the piezoelectric material layer in the multilayer piezoelectric element 1 is adopted by adopting the addition amount of the conductive material in the piezoelectric ceramic in which the piezoelectric characteristics that match or approximate the piezoelectric characteristics of the multilayer piezoelectric element 1 measured in advance are obtained. The diffusion state of the eleven conductive materials can be reproduced. As will be apparent from the examples described later, a piezoelectric ceramic manufactured by adding a conductive material having a concentration equivalent to that of the conductive material in the piezoelectric layer 11 can obtain a piezoelectric constant equivalent to that of the multilayer piezoelectric element 1. it can. Therefore, thereafter, the piezoelectric constant as the multilayer piezoelectric element 1 can be recognized by manufacturing a piezoelectric ceramic to which a conductive material is added so as to have the concentration and measuring the piezoelectric constant.

Example 1 describes an example in which an Ag—Pd alloy is used as the conductive material of the internal electrode layer.
First, the manufacturing method of a laminated body is demonstrated. PbO, TiO ₂ , ZrO ₂ , ZnO, Nb ₂ O ₅ and SrCO ₃ were weighed as starting materials so as to have the following composition, wet mixed for 16 hrs using a ball mill, and then 700 to 900 ° C. in an atmosphere of 2 hrs Calcination was performed to obtain a calcined product.
(Pb _0.965 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃
This calcined product was pulverized by a ball mill for 16 hrs and dried to obtain a calcined powder. This calcined powder was kneaded by adding a binder, a solvent, and the like to prepare a piezoelectric layer paste. On the other hand, a conductive material for forming an internal electrode or various oxides, organometallic compounds, resinates, or the like that become conductive materials after firing were kneaded with a binder and a solvent to prepare an internal electrode paste. In this example, an Ag—Pd alloy (Ag / Pd = 85/15 (weight ratio)) was used as the conductive material.

Subsequently, by using these piezoelectric layer paste and internal electrode layer paste, a green chip in which 20 layers of piezoelectric layer precursors and internal electrode layer precursors are alternately laminated is manufactured by a printing method. A binder removal treatment was performed and baked to obtain a laminate.
The obtained laminated body was subjected to end surface polishing, and terminal electrodes were formed by printing or baking a separately prepared terminal electrode paste to obtain a laminated piezoelectric element. This laminated piezoelectric element was subjected to a polarization treatment of 3 kV / mm-15 min in 120 ° C. silicone oil.

The amount of displacement was measured using a laser Doppler displacement meter in a state where a sine wave having a driving voltage of 1.3 kV / mm and a frequency of 0.1 Hz was applied to the multilayer piezoelectric element described above. The piezoelectric constant d31 obtained from the displacement and the applied voltage was 362 (pC / N).
In addition, a composition analysis was performed on the piezoelectric layer 11 of the produced multilayer piezoelectric element 1. Note that the thickness of the piezoelectric layer 11 (= interval between the internal electrode layers 12) of the produced multilayer piezoelectric element 1 is 24 μm, and the composition analysis shows that the internal electrode layer 12 has 3 μm and 6 μm as shown in FIG. And a position of 12 μm were specified by EPMA (Electron Probe Micro Analyzer).
As a result of composition analysis, Ag, which is a constituent element of the conductive material constituting the internal electrode layer 12, was detected in addition to the elements constituting the piezoelectric layer 11. Therefore, it was found that the constituent elements of the conductive material forming the internal electrode layer 12 diffuse into the piezoelectric layer 11 in the process of removing the binder and firing the laminate 10. Table 1 and FIG. 4 show the amount of Ag (in terms of Ag ₂ O) in the piezoelectric layer 11. Ag is diffused almost uniformly in the piezoelectric layer 11, and the amount of diffusion is in terms of Ag ₂ O. About 0.3 wt%.

  As described above, in order to evaluate the original characteristics of the piezoelectric ceramic constituting the piezoelectric layer 11 of the multilayer piezoelectric element 1 with the piezoelectric ceramic alone, it is necessary to consider the influence of the conductive material constituting the internal electrode layer 12. I know that there is. Therefore, a method of applying the internal electrode layer paste used for the production of the multilayer piezoelectric element 1 to the molded body before the binder removal, and diffusing the conductive material into the piezoelectric ceramic that exists alone by removing the binder and firing. Since it implemented, the result is demonstrated below.

<Example 1-1>
PbO, TiO ₂ , ZrO ₂ , ZnO, Nb ₂ O ₅ and SrCO ₃ were weighed as starting materials so as to have the following composition, wet mixed for 16 hrs using a ball mill, and then 700 to 900 ° C. in an atmosphere of 2 hrs Calcination was performed to obtain a calcined product.
(Pb _0.965 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃
Thereafter, the calcined product was pulverized for 16 hrs using a ball mill. It is dried and P.P. V. An appropriate amount of A (polyvinyl alcohol) was added and granulated. As the granulated powder, three types of compacts of 20 mm long × 20 mm wide, 1 mm thick, 1.7 mm, and 3 mm were produced using a uniaxial press molding machine at a pressure of about 392 MPa. The reason why the thickness of the molded body is three types, 1 mm, 1.7 mm, and 3 mm, is to control the amount of Ag diffused into the piezoelectric ceramic by changing the thickness of the molded body.
The obtained molded body was coated with the above-mentioned internal electrode layer paste on both the front and back surfaces, heat-treated to volatilize the binder, and then fired at 960 ° C. for 2 hrs in the atmosphere to obtain a porcelain sample. Table 2 shows the relationship between the thickness of the molded body and the thickness of the obtained porcelain sample.

Then, after lapping the surface to make the thickness 0.5 mm, electrodes were formed by baking on both the front and back surfaces. Thereafter, a polarization treatment of 3 kV / mm-15 min was performed in 120 ° C. silicone oil. A porcelain sample cut into a length of 12 mm × width of 3 mm × 0.5 mm after being left for 24 hrs was measured for an electromechanical coupling coefficient k31 and a dielectric constant εr (1 kHz) using an impedance analyzer (HP4194A, manufactured by Hewlett-Packard Company). .
Further, for each porcelain sample, a sinusoidal wave having a driving voltage of 1.3 kV / mm and a frequency of 0.1 Hz was applied, and a displacement amount was measured using a laser Doppler displacement meter. The piezoelectric constant d31 was determined from the displacement and the applied voltage. In addition, the amount of Ag diffused into the piezoelectric ceramic by EPMA was quantified. Table 3 and FIG. 5 show the analysis results of the distance from the surface of the porcelain sample and the amount of Ag (in terms of Ag ₂ O). Table 4 shows the average Ag (Ag ₂ O equivalent) amount and material characteristics of each porcelain sample in comparison.

From the above results, in the sample 4 in which the Ag (Ag ₂ O) diffusion amount is substantially the same as that in the piezoelectric layer 11 of the multilayer piezoelectric element 1, the piezoelectric constant d31 obtained from the displacement amount of the multilayer piezoelectric element 1 is obtained. D31 = 353 (pC / N) almost equal to 362 (pC / N) is obtained. Therefore, by adopting the same conditions as in the sample 4, the piezoelectric characteristics in the piezoelectric layer 11 of the multilayer piezoelectric element 1 can be almost reproduced by a piezoelectric ceramic that exists independently. In the piezoelectric ceramic used in this example, the piezoelectric constant d31 is improved by diffusion of Ag.

<Example 1-2>
In Example 1-1, Ag was diffused, but in Example 1-2, Ag ₂ O was added to produce a piezoelectric ceramic to reproduce the Ag diffusion state of the piezoelectric layer 11 of the multilayer piezoelectric element 1. Therefore, it will be described below.
After performing pre-baking in the same manner as in Example 1-1, Ag ₂ O was added (addition amount = 0 wt%, 0.09 wt%, 0.28 wt%, 0.47 wt%) and 16 hrs using a ball mill. Crushed. Then, the porcelain sample was produced like Example 1-1. This porcelain sample was lapped to a thickness of 0.5 mm, and then electrodes were formed on both the front and back surfaces by baking. Thereafter, a polarization treatment of 3 kV / mm-15 min was performed in 120 ° C. silicone oil. After the polarization treatment, the sample was allowed to stand for 24 hours, and then cut into a sample having a length of 12 mm × width of 3 mm × thickness of 0.5 mm. With respect to this sample, an electromechanical coupling coefficient kr (%) and a dielectric constant εr (1 kHz) were measured using an impedance analyzer (manufactured by Hewlett Packard: HP4194A). Further, for each sample, a sine wave having a driving voltage of 1.3 kV / mm and a frequency of 0.1 Hz was applied, and a displacement amount was measured using a laser Doppler displacement meter. The piezoelectric constant d31 was determined from the displacement and the applied voltage. Table 5 shows the addition amount of Ag ₂ O and material characteristics.

From the above results, in sample 6 in which the Ag ₂ O diffusion amount and the Ag ₂ O amount in the piezoelectric layer 11 of the multilayer piezoelectric element 1 are substantially the same, the piezoelectric constant d31 obtained from the displacement amount of the multilayer piezoelectric element 1 is obtained. D31 = 349 (pC / N) which is almost equivalent to 362 (pC / N) is obtained. Therefore, by adopting the same conditions as in the sample 6, the piezoelectric characteristics in the piezoelectric layer 11 of the multilayer piezoelectric element 1 can be substantially reproduced with a single piezoelectric ceramic.

In Example 1, the case where the conductive material constituting the internal electrode layer 12 is an Ag—Pd alloy is shown. However, in Example 2, the conductive material constituting the internal electrode layer 12 is Cu, and is fired in a reducing atmosphere. The case of the laminated piezoelectric element 1 will be described.
A laminated piezoelectric element 1 was produced in the same manner as in Example 1 except that the conductive material constituting the internal electrode layer 12 was Cu, the firing was a reducing atmosphere, and the number of laminated layers was 300. A drive voltage of 1.7 kV / mm, A displacement wave was measured using a laser Doppler displacement meter by applying a sin wave with a frequency of 0.1 Hz. The piezoelectric constant d33 obtained from the displacement and the applied voltage was 635 (pC / N).
In addition, a composition analysis was performed on the piezoelectric layer 11 of the produced multilayer piezoelectric element 1. Note that the thickness of the piezoelectric layer 11 (= interval between the internal electrode layers 12) of the produced multilayer piezoelectric element 1 is 80 μm, and the composition analysis shows that the internal electrode layer 12 has 10 μm and 20 μm as shown in FIG. And 40 μm positions were identified by EPMA line analysis.
As a result of the composition analysis, Cu, which is a constituent element of the conductive material forming the internal electrode layer 12, was detected in addition to the elements forming the piezoelectric layer 11. Therefore, it was found that the constituent elements of the conductive material forming the internal electrode layer 12 diffuse into the piezoelectric layer 11 in the process of removing the binder and firing the laminate 10. Table 6 and FIG. 7 show the amount of Cu (in terms of Cu ₂ O) in the piezoelectric layer 11. Cu is diffused almost uniformly in the piezoelectric layer 11, and the amount of diffusion is in terms of Cu ₂ O. About 0.03 wt%.

  As described above, in order to evaluate the original characteristics of the piezoelectric ceramic constituting the piezoelectric layer 11 of the multilayer piezoelectric element 1 by itself, even when Cu is used as the conductive material of the internal electrode layer 12, It turns out that the effects need to be considered. Therefore, a method of applying the internal electrode layer paste used for the production of the multilayer piezoelectric element 1 to the molded body before the binder removal, and diffusing the conductive material into the piezoelectric ceramic that exists alone by removing the binder and firing. Carried out. The results will be described below.

<Example 2-1>
PbO, TiO ₂ , ZrO ₂ , ZnO, Nb ₂ O ₅ and SrCO ₃ were weighed as starting materials so as to have the following composition, wet mixed for 16 hrs using a ball mill, and then 700 to 900 ° C. in an atmosphere of 2 hrs Calcination was performed to obtain a calcined product.
(Pb _0.965 Sr _0.03 ) [(Zn _1/3 Nb _2/3 ) _0.1 Ti _0.43 Zr _0.47 ] O ₃
Thereafter, the calcined product was pulverized for 16 hrs using a ball mill. It was dried and granulated by adding an appropriate amount of acrylic resin as a binder. As the granulated powder, a disk-shaped molded body having a diameter of 17 mm, a thickness of 2.4 mm and a thickness of 1.2 mm was produced using a uniaxial press molding machine at a pressure of about 392 MPa.
The obtained molded body was coated with internal electrode layer paste on both the front and back surfaces, heat-treated to volatilize the binder, and then fired at 950 ° C. for 4 hrs in a reducing atmosphere to obtain a thickness of 2.0 mm and 1 mm. A porcelain sample of 0.0 mm was obtained.
After the obtained porcelain samples were each lapped, electrodes were formed by baking on both the front and back surfaces. Thereafter, a polarization treatment of 3 kV / mm-15 min was performed in 120 ° C. silicone oil. After being left for 24 hours, an electromechanical coupling coefficient kr (%) and a dielectric constant εr (1 kHz) were measured using an impedance analyzer (HP4194A, manufactured by Hewlett-Packard Company).
Further, a sinusoidal wave having a driving voltage of 1.7 kV / mm and a frequency of 0.1 Hz was applied to each porcelain sample, and a displacement amount was measured using a laser Doppler displacement meter. The piezoelectric constant d33 was obtained from the amount of displacement and the applied voltage. Further, the amount of Cu diffused into the piezoelectric ceramic was quantified by EPMA. Table 7 and FIG. 8 show the analysis results of the distance from the surface of the porcelain sample and the Cu (Cu ₂ O equivalent) amount. Table 8 shows the average Cu (Cu ₂ O equivalent) amount and material characteristics in comparison.

  From the above results, it can be seen that when Cu diffuses, the piezoelectric constant d33 decreases. Further, in the sample 10 in which the Cu diffusion amount is substantially the same as that in the piezoelectric layer 11 of the multilayer piezoelectric element 1, it is equivalent to 635 (pC / N) which is the piezoelectric constant d33 obtained from the displacement amount of the multilayer piezoelectric element 1. The piezoelectric constant d33 = 622 (pC / N) is obtained, and the piezoelectric characteristics in the piezoelectric layer 11 of the multilayer piezoelectric element 1 can be substantially reproduced by a piezoelectric ceramic that exists independently.

<Example 2-2>
In Example 2-1, Cu was diffused, but in Example 2-2, Cu ₂ O was added to produce a piezoelectric ceramic to reproduce the Cu diffusion state of the piezoelectric layer 11 of the multilayer piezoelectric element 1. Therefore, it will be described below.
After performing pre-baking in the same manner as in Example 2-1, Cu ₂ O was added (addition amount = 0 wt%, 0.01 wt%, 0.03 wt%, 0.05 wt%) and 16 hrs using a ball mill. Crushed. Thereafter, a porcelain sample was produced in the same manner as in Example 2-1. This porcelain sample was lapped to obtain a disk-shaped sample having a thickness of 0.6 mm. Electrodes were formed on the front and back surfaces of this sample by baking. Thereafter, a polarization treatment of 3 kV / mm-15 min was performed in 120 ° C. silicone oil. After being left for 24 hrs after the polarization treatment, an electromechanical coupling coefficient kr (%) and a dielectric constant εr (1 kHz) were measured using an impedance analyzer (HP4194A manufactured by Hewlett-Packard Company). Further, for each sample, a sine wave having a driving voltage of 1.7 kV / mm and a frequency of 0.1 Hz was applied, and a displacement amount was measured using a laser Doppler displacement meter. The piezoelectric constant d33 was obtained from the amount of displacement and the applied voltage. Table 9 shows the amount of Cu ₂ O added and material characteristics.

From the above results, in the multilayer Cu 2 _O diffused amount of the piezoelectric layers 11 of the piezoelectric element 1 and the Cu 2 _O weight samples 12 and slightly more is substantially the same sample 13, the amount of displacement of the multilayer piezoelectric element 1 D33 = 627 (pC / N) and d33 = 630 (pC / N) substantially equal to the obtained piezoelectric constant d33 of 635 (pC / N) are obtained, and the piezoelectric layer 11 of the multilayer piezoelectric element 1 is obtained. The piezoelectric characteristics inside can be almost reproduced with a single piezoelectric ceramic.

It is a figure which shows the example of 1 structure of a lamination type piezoelectric element. It is a flowchart which shows the manufacture procedure of a lamination type piezoelectric element. It is a figure which shows the measurement position of Ag diffusion amount in Example 1. FIG. 4 is a graph showing a relationship between a distance from an internal electrode layer and an Ag diffusion amount in Example 1. It is a graph which shows the relationship between the distance from the porcelain sample surface and Ag diffusion amount in Example 1-1. It is a figure which shows the measurement position of Cu diffusion amount in Example 2. FIG. 6 is a graph showing a relationship between a distance from an internal electrode layer and a Cu diffusion amount in Example 2. It is a graph which shows the relationship between the distance from the porcelain sample surface and Cu diffusion amount in Example 2-1.

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 (4)

In a stacked piezoelectric element in which a piezoelectric layer including a piezoelectric ceramic and an internal electrode layer including a conductive material are stacked, and the conductive material is diffused in the piezoelectric layer, the piezoelectric ceramic used in the piezoelectric layer A method for measuring piezoelectric characteristics in a state where the piezoelectric ceramic exists alone,
A method for evaluating a piezoelectric ceramic, characterized in that the piezoelectric material of the piezoelectric ceramic is measured by containing the conductive material diffused in the piezoelectric layer in the piezoelectric ceramic that is present alone.   2. The piezoelectric device according to claim 1, wherein the piezoelectric property is measured by including the conductive material in an amount that can obtain the piezoelectric property of the multilayer piezoelectric element in the piezoelectric ceramic that exists alone. Evaluation method of porcelain.   The method for evaluating a piezoelectric ceramic according to claim 1 or 2, wherein the conductive material contained in the piezoelectric ceramic is based on at least one of diffusion and addition.   The method for evaluating a piezoelectric ceramic according to claim 1, wherein the conductive material contained in the piezoelectric ceramic is Ag or Cu.

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