JP5345834B2 - Lead-free piezoelectric ceramic, multilayer piezoelectric device, and lead-free piezoelectric ceramic manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead-free piezoelectric ceramic favorable for applying to a highly efficient piezoelectric actuator, a laminated piezoelectric device applying the same and a method for producing the lead-free piezoelectric ceramic. <P>SOLUTION: The lead-free piezoelectric ceramic whose main ingredient is a compound having a composition denoted as x(Bi<SB>0.5</SB>Na<SB>0.5</SB>TiO<SB>3</SB>)-y(BaTiO<SB>3</SB>)-z(SrTiO<SB>3</SB>) (wherein, x+y+z=1) is obtained by adding a copper oxide of 0.1 wt.% or more and 2 wt.% or less and manganese dioxide (MnO<SB>2</SB>) and by baking at 1,100&deg;C or lower and then the lead-free piezoelectric ceramic has a low temperature sintering property and a large mechanical quality factor. As a result, a highly efficient laminated piezoelectric actuator is produced with a lead-free material. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a lead-free piezoelectric ceramic having a low temperature sintering property, a laminated piezoelectric device, and a method for producing a lead-free piezoelectric ceramic.

  In recent years, piezoelectric ceramic compositions containing no lead compound have attracted attention as piezoelectric ceramic element materials, and research and development have been promoted (for example, Patent Document 1). Since such a piezoelectric ceramic composition does not contain a lead compound, the load on the natural environment can be reduced.

The piezoelectric ceramic composition described in Patent Document 1 has a composition formula of x (Bi _0.5 Na _0.5 TiO ₃ ) -y (BaTiO ₃ ) -z (SrTiO ₃ ) (x + y + z = 1). Then, in the triangular coordinates having these components as vertices, the composition exists within a range surrounded by a predetermined point. This provides a lead-free piezoelectric ceramic composition that has a high Curie temperature and is practical.

On the other hand, in order to enhance the function of the device, there is an increasing demand for a laminated piezoelectric device in which piezoelectric ceramics and electrodes are laminated. An internal electrode using a material such as Ag—Pd is provided inside the multilayer piezoelectric device, and the material such as Ag—Pd used for the internal electrode melts when it reaches a temperature exceeding 1000 ° C. start.
JP 2003-201172 A

  In the piezoelectric ceramic disclosed in Patent Document 1, the sintered body becomes dense when fired at a high temperature of 1200 ° C. However, when a multilayer piezoelectric device is manufactured using a non-lead material, The densification temperature exceeds the melting temperature of the internal electrode. The inventors of the present invention have developed a multilayer piezoelectric device using a BNT-BT-ST piezoelectric ceramic as a piezoelectric layer. In that process, paying attention to the need to fire the multilayer piezoelectric device at a temperature at which the internal electrodes do not melt, and by adding copper oxide (CuO), the BNT-BT-ST piezoelectric ceramics can be densified at low temperature I found.

  However, in order to increase the efficiency of the piezoelectric device, it is not sufficient that it is suitable for low-temperature firing and easy lamination, and it is necessary to have a large mechanical quality factor. Although the mechanical quality factor of the BNT-BT-ST piezoelectric ceramic is slightly increased by the addition of copper oxide, it cannot be said to be sufficiently large. The present invention has been made in view of such circumstances, and is preferably a lead-free piezoelectric ceramic suitable for application to a highly efficient piezoelectric device, a laminated piezoelectric device using the same, and a method for producing a lead-free piezoelectric ceramic The purpose is to provide.

(1) In order to achieve the above object, the lead-free piezoelectric ceramic according to the present invention includes x (Bi _0.5 Na _0.5 TiO ₃ ) -y (BaTiO ₃ ) -z (SrTiO ₃ ) (however, x + y + z = 1), which is a lead-free piezoelectric ceramic mainly composed of a compound represented by the composition: 1% by weight (wt%) or more of copper oxide with respect to the lead-free piezoelectric ceramic material. It is characterized in that it is obtained by adding manganese dioxide (MnO ₂ ) and firing at 1100 ° C. or lower, in addition to adding by weight% or less.

  Thus, since the lead-free piezoelectric ceramic of the present invention is fired containing copper oxide, it has low-temperature sinterability and is suitable for a piezoelectric layer of a multilayer piezoelectric device. Further, by including manganese dioxide, it has a mechanical quality factor that is at least twice as large as that not including manganese dioxide. As a result, a highly efficient stacked piezoelectric device can be manufactured using a lead-free material.

  (2) Further, the lead-free piezoelectric ceramic according to the present invention is characterized by having a mechanical quality factor of 200 or more. As a result, the use for piezoelectric devices is expanded as an elastically energy-efficient material.

  (3) The lead-free piezoelectric ceramic according to the present invention is characterized in that the added manganese dioxide is 0.1 wt% or more and 2.0 wt% or less. As a result, the mechanical quality factor of the lead-free piezoelectric ceramic becomes larger than 200, and the application to the piezoelectric device is expanded as an elastically energy-efficient material.

  (4) Further, the multilayer piezoelectric device according to the present invention is formed by alternately laminating piezoelectric layers made of the above lead-free piezoelectric ceramics and internal electrode layers made of Ag-Pd, and integrally firing. It is characterized by being. Thus, the multilayer piezoelectric device of the present invention is integrally fired with the internal electrode layer and is driven with high efficiency.

(5) Moreover, the manufacturing method of the lead-free piezoelectric ceramics according to the present invention is x (Bi _0.5 Na _0.5 TiO ₃ ) -y (BaTiO ₃ ) -z (SrTiO ₃ ) (where x + y + z = 1). The addition step of adding manganese dioxide to the calcined powder of lead-free piezoelectric ceramics whose main component is a compound represented by the following formula: And a firing step of firing the molded body of the material obtained by the addition step at 1100 ° C. or lower. As described above, the lead-free piezoelectric ceramics can be sintered at a low temperature by adding copper oxide. Moreover, a larger mechanical quality factor can be realized by adding manganese dioxide, and lead-free piezoelectric ceramics can be applied to highly efficient piezoelectric devices.

  According to the present invention, it is possible to provide a lead-free piezoelectric ceramic preferable for application to a highly efficient piezoelectric device, a laminated piezoelectric device to which the lead-free piezoelectric ceramic is applied, and a method for producing the lead-free piezoelectric ceramic.

(Composition of base material)
The lead-free piezoelectric ceramic of the present invention uses a BNT-BT-ST piezoelectric ceramic as a base material. The BNT-BT-ST-based piezoelectric _{ceramics, x (Bi 0.5 Na 0.5 TiO} 3) -y (BaTiO 3) -z (SrTiO 3) ( provided that, x + y + z = 1 ) of the compound represented by the composition Is a lead-free piezoelectric ceramic.

(Base material experiment)
When expressed as x (Bi _0.5 Na _0.5 TiO ₃ ) -y (BaTiO ₃ ) -z (SrTiO ₃ ) (where x + y + z = 1), 0.79 ≦ x ≦ 0.87, 0.10 ≦ y ≦ 0.19, appropriately selected in a range satisfying 0 ≦ z ≦ 0.07, and when the composition trace experiment was performed, the result that the electromechanical coupling coefficient kr = 0.17 was obtained in most compositions, A relatively large value was obtained as the electromechanical coupling coefficient kr of the lead-free piezoelectric material. In the trace experiment, a silver paste was printed on both main surfaces of the sintered pellet, and the electrodes were polarized by firing, and each characteristic was measured. The sintered body was polarized in the thickness direction under the conditions of 60 to 150 ° C., 5 to 20 minutes, and 2 to 4 kV / mm (hereinafter, the same applies to the characteristic measurement).

  FIG. 1 is a table showing the results of measurement of density, electromechanical coupling coefficient, relative dielectric constant, and dielectric loss for BNT-BT-ST piezoelectric ceramics of each composition. Further, in subsequent experiments, it was found that the characteristics in the composition of x = 0.83, y = 0.08, z = 0.09 and the composition in the vicinity thereof are preferable. There is no direct relationship between the composition of the BNT-BT-ST piezoelectric ceramic and the size of the low temperature sinterability or mechanical quality factor. The density indicates a bulk density and is measured by Archimedes method (hereinafter, the same applies to the density measurement).

(Addition of copper oxide)
In order to lower the sintering temperature of the ceramic member without deteriorating the piezoelectric characteristics of the base material of the BNT-BT-ST piezoelectric ceramic, a substance having a high reactivity and a low melting point is added, and a liquid phase is added to the grain boundary phase. It is effective to promote low temperature sintering.

A sintering aid made of copper oxide is suitable for densifying BNT-BT-ST piezoelectric ceramics. By adding copper oxide to the piezoelectric ceramic in the manufacturing process of the BNT-BT-ST piezoelectric ceramic, the BNT-BT-ST piezoelectric ceramic is densified at a firing temperature of 1100 ° C. or lower. Copper oxide is preferably used as a sintering aid for BNT-BT-ST piezoelectric ceramics because it has a similar composition as a sintering aid for PZT (PbTiO ₃ -PbZrO ₃ ) piezoelectric ceramics and BaTiO ₃ piezoelectric ceramics. It can be inferred from the fact that the binding agent functions sufficiently. Whether it is a BBZ sintering aid for PZT-based piezoelectric ceramics or copper oxide for BNT-BT-ST-based piezoelectric ceramics, the mechanism for creating a liquid phase in the grain boundary phase and promoting low-temperature sintering is the same. is there.

(Experiment of adding copper oxide)
Using the BNT-BT-ST piezoelectric ceramics having the compositions of sample numbers 1 and 13 shown in FIG. 1 as the base material, firing was performed at each copper oxide addition amount and at each firing temperature. The matrix composition was adjusted when the powder was weighed. Copper oxide powder was mixed with the calcined powder of the base material. Copper oxide was added at the time of pulverization after calcination, and added in an externally divided weight ratio with respect to the calcination powder. That is, the auxiliary agent addition ratio is a ratio (H / E) of the weight (H) of the sintering auxiliary agent to the weight (E) of the base material. In this way, 0.3% by weight or 0.6% by weight of copper oxide was added.

Molded bodies with addition amounts of copper oxide of 0 wt%, 0.3 wt%, and 0.6 wt% were fired at 1000 ° C, 1050 ° C, and 1100 ° C, respectively. Moreover, the molded object which did not add an auxiliary agent was baked at 1200 degreeC. And when the density of the sintered compact was measured, BNT-BT-ST obtained by using the composition of sample number 1 as a base material, with a firing temperature of 1000 ° C. or higher and a copper oxide addition amount of 0.3 wt% or higher. The density of the piezoelectric ceramics exceeded 5.5 × 10 ³ kg / m ³ . Further, the density of the BNT-BT-ST piezoelectric ceramic obtained under the conditions of a firing temperature of 1100 ° C. or higher and an addition amount of copper oxide of 0.3% by weight or higher exceeds 5.7 × 10 ³ kg / m ^3. The density was the same as the density of the sample fired at 1200 ° C. without adding copper oxide. The density of the sample fired at 1200 ° C. without adding copper oxide was 5.72 × 10 ³ kg / m ³ .

  FIG. 2 is a graph showing the relationship between the amount of copper oxide added and the density of a BNT-BT-ST piezoelectric ceramic having the composition of sample number 1 as a base material. As shown in FIG. 2, the BNT-BT-ST piezoelectric ceramic having the composition of sample number 1 is densely sintered even when the firing temperature is set to 1000 ° C. by setting the addition amount of copper oxide to 0.3% by weight or more. It turns out that a body is obtained.

On the other hand, the density of the BNT-BT-ST piezoelectric ceramics having the composition of sample number 13 as a base material and a firing temperature of 1000 ° C. or higher and an added amount of copper oxide of 0.3 wt% or higher is 5.7 × 10 ³ kg / m. ^It was over ³ and was comparable to the density of the sample fired at 1200 ° C. without adding copper oxide. The density of the sample fired at 1200 ° C. without adding copper oxide was 5.72 × 10 ³ kg / m ³ .

  FIG. 3 is a graph showing the relationship between the amount of copper oxide added and the density of the BNT-BT-ST piezoelectric ceramics having the composition of Sample No. 13 as a base material. As shown in FIG. 3, the BNT-BT-ST piezoelectric ceramic having the composition of Sample No. 13 is densely fired even when the firing temperature is 1000 ° C. by setting the amount of copper oxide to be 0.3% by weight or more. It was found that a knot was obtained.

  In addition, referring to the results obtained by the above experiment, in reality, densification occurs at an addition amount of 0.3% by weight or more of copper oxide. It is thought that crystallization will occur.

  The pellet-like sintered body sample fired at each copper oxide addition amount and each firing temperature in this way was polarized, and the electromechanical coupling coefficient was measured. Measurements were performed on samples having an addition amount of copper oxide of 0 wt%, 0.3 wt%, 0.6 wt%, and firing temperatures of 1000 ° C, 1050 ° C, and 1100 ° C. For reference, the electromechanical coupling coefficient was also measured for a sample fired at 1200 ° C. without adding copper oxide.

  FIG. 4 is a table showing the relationship between each firing temperature, each added amount, and the electromechanical coupling coefficient. For example, the electromechanical coupling coefficient measured for a sample fired at 1100 ° C. with an addition amount of copper oxide of 0.3% by weight is 0.15. “−” In the figure indicates that polarization was impossible, and the blank indicates that measurement was not performed.

  When the sample of the base material composition of sample number 1 was measured, polarization was impossible when the addition amount of copper oxide was 0% by weight, but 0.3% by weight and 0.6% by weight were added. Any of those added could be polarized, and a high electromechanical coupling coefficient of 0.12 or more was obtained. On the other hand, when the sample of the base material composition of sample number 13 was measured, it could not be measured except for the sample which was not added with copper oxide at 0.3 wt% and baked at 1000 ° C. From the result of the sample of the base material composition of sample number 1, a large electromechanical coupling is achieved by setting the amount of copper oxide added to the BNT-BT-ST piezoelectric ceramic base material to be 0.3 wt% or more and 0.6 wt% or less. It has been demonstrated that the coefficient can be obtained. In addition, from the result of the sample of the base material composition of sample number 13, it was found that sufficient piezoelectric characteristics may not be obtained even when copper oxide is added to the base material composition not containing strontium.

  In consideration of this result, other characteristics were also measured in a confirming manner. The sample of sample No. 1 with no copper oxide added or 0.6% by weight added, and the samples fired at 1200 ° C. and 1100 ° C. were measured for relative dielectric constant εr and dielectric loss tan δ. . FIG. 5 is a table summarizing the characteristics of BNT-BT-ST piezoelectric ceramic samples prepared at each copper oxide addition amount and at each firing temperature. Data are shown for firing temperatures of 1200 ° C. and 1100 ° C., and copper oxide additions of 0 wt% and 0.6 wt%, respectively. As shown in FIG. 5, the BNT-BT-ST piezoelectric ceramics obtain the same piezoelectric properties as those fired at 1200 ° C. even when fired at 1000 ° C. when 0.6 wt% of copper oxide is added. It has been demonstrated that

(Addition of manganese dioxide)
As described above, if copper oxide is added to the BNT-BT-ST piezoelectric ceramic in an amount of 0.1 wt% or more and 2 wt% or less, sintering is performed at a temperature of 1100 ° C. or less. The lead-free piezoelectric ceramic according to the present invention is fired by further adding 0.1% by weight or more and 2% by weight or less of manganese dioxide to the calcined powder of BNT-BT-ST piezoelectric ceramic. By adding copper oxide, low temperature firing is possible, and by adding manganese dioxide, the mechanical quality factor can be dramatically increased. As a result, a highly efficient piezoelectric device can be manufactured using a lead-free material with a low environmental load.

A production method for producing the lead-free piezoelectric ceramic of the present invention by low-temperature firing is as follows. First, Bi ₂ O ₃ , Na ₂ CO ₃ , BaTiO ₃ , SrCO ₃ , and TiO ₂ powders are weighed and mixed with a solvent in a mill. Then, the mixed powder is dried and granulated by a mesh pass. Subsequently, the powder is calcined at 800 ° C. and pulverized. Then, a predetermined amount of copper oxide and manganese dioxide powder is added together with the binder, dried and granulated. If the powder thus obtained is formed into a desired shape and fired at 1100 ° C. or lower, a sintered body of BNT-BT-ST piezoelectric ceramics is obtained by low-temperature firing.

(Experiment with manganese dioxide addition)
Referring to the results of the above copper oxide addition experiment, using a BNT-BT-ST piezoelectric ceramic as a base material, a certain amount of copper oxide and each amount of manganese dioxide were added and fired to prepare each sample. .

First, when powder is weighed and expressed as x (Bi _0.5 Na _0.5 TiO ₃ ) + y (BaTiO ₃ ) + z (SrTiO ₃ ) (where x + y + z = 1), x = 0.83, y = The base material composition was weighed so that 0.08 and z = 0.09. Copper oxide powder and manganese dioxide powder were mixed with the calcined powder of such a base material. Copper oxide powder and manganese dioxide powder were added during pulverization after calcination. It added by the external weight ratio with respect to calcining powder. That is, the auxiliary agent addition ratio is a ratio (H / E) of the weight (H) of the sintering auxiliary agent to the weight (E) of the base material. The amount of copper oxide added to the calcined powder of the base material was constant at 0.5% by weight in all samples. The amount of manganese dioxide added to the calcined powder of the base material was changed to 0 wt%, 0.3 wt%, 0.5 wt%, 1.0 wt%, and 2.0 wt% for each sample. A pellet-like CIP compact was produced from the powder obtained by mixing the copper oxide powder and the manganese dioxide powder in this manner.

  And each molded object was baked at 1000 degreeC, the diameter 15mm and the pellet of thickness 1mm were produced, and the density was measured. In addition, the sintered body was polarized, its capacitance, resonance / antiresonance frequency, resonance resistance were measured, and the mechanical quality factor was measured.

FIG. 6A is a table showing the relationship between the amount of manganese dioxide added, the density of the lead-free piezoelectric ceramic, and the mechanical quality factor Qm. FIG. 6B is a graph showing the relationship between the amount of manganese dioxide added and the mechanical quality factor Qm of the lead-free piezoelectric ceramic. As shown in FIGS. 6A and 6B, the mechanical quality factor Qm is remarkably increased by adding manganese dioxide. As a result, a highly efficient piezoelectric device can be realized with a lead-free material. On the other hand, the densities are all about 5.7 × 10 ³ kg / m ³ , indicating that the obtained lead-free piezoelectric ceramics are sintered.

  The mechanical quality factor Qm when any amount of manganese dioxide is added is twice or more the mechanical quality factor Qm when no manganese dioxide is added. Further, as shown in FIGS. 6A and 6B, the mechanical quality factor Qm exceeds 200 when the amount of manganese dioxide added is in the range of 0.1 wt% to 2.0 wt%. The mechanical quality factor Qm exceeds 400 in the range of 0.2 wt% to 1.5 wt%. In order to use piezoelectric ceramics industrially, the mechanical quality factor Qm is preferably 400 or more, and the addition amount of manganese dioxide is preferably 0.2 wt% or more and 1.5 wt% or less. Further, referring to the approximate curve derived from the actually measured data (FIG. 6B), the mechanical quality factor Qm exceeds 500 in the range of 0.3 wt% to 0.7 wt%, and 0.3 Qm is further improved in the range of not less than 0.5% by weight.

  Next, by the same production method as described above, a lead-free piezoelectric ceramic was produced by changing the addition amount of manganese dioxide and changing the addition amount of copper oxide. The amount of manganese dioxide added to the calcined powder of the base material was kept constant at 0.3% by weight. In addition, the amount of copper oxide added to the calcined powder of the base material was changed to 0.2% by weight, 0.3% by weight, 0.4% by weight, and 0.5% by weight for each sample. Got the body. Then, the density and the mechanical quality factor Qm were measured by the same measuring method as described above.

  FIG. 7A is a table showing the relationship between the amount of copper oxide added, the density of the lead-free piezoelectric ceramic, and the mechanical quality factor Qm. FIG. 6B is a graph showing the relationship between the amount of manganese dioxide added and the mechanical quality factor Qm of the lead-free piezoelectric ceramic. 7 (a) and 7 (b), the mechanical quality factor Qm slightly increases with respect to the added amount of copper oxide, but the mechanical quality factor Qm is not significantly affected by the added amount of copper oxide. I understand that. Thus, it was demonstrated that the amount of copper oxide added does not significantly affect the mechanical quality factor Qm. Therefore, in the range of 0.1 wt% or more and 2 wt% or less, it is considered that the mechanical quality factor Qm does not change greatly with the amount of copper oxide added.

  Next, in the same production method as described above, a lead-free piezoelectric ceramic sample was produced for each of the case where both copper oxide and manganese dioxide were not added, the case where either was added, and the case where both were added. Then, the density and the mechanical quality factor Qm were measured for each sample.

  FIG. 8 is a table showing the relationship between the amount of copper oxide and manganese dioxide added, the density of the lead-free piezoelectric ceramic, and the mechanical quality factor Qm. When only copper oxide was added and when both were added, firing was performed at 1000 ° C. However, the sample in which both were not added and the sample in which only manganese dioxide was added were fired at 1200 ° C. because they were not sufficiently densified even when fired at 1000 ° C.

  As shown in FIG. 8, the sample to which only copper oxide is added has a sufficient density and is sintered, but the mechanical quality factor Qm slightly increases due to the influence of densification, but is about 100, which is high. It was found that the mechanical quality factor Qm is too low for use in an ultrasonic element such as an ultrasonic motor. In addition, in the sample to which only manganese dioxide was added, there was a tendency that manganese dioxide was not densified even at 1200 ° C. and manganese dioxide inhibited densification. In addition, it was confirmed that the sample to which both were added was sufficiently densified even at low temperature firing, and the mechanical quality factor Qm increased dramatically. Manganese dioxide is an obstacle to densification, but the addition of copper oxide makes it possible to achieve sufficient densification even at low temperatures. As described above, it was confirmed that it is important to add both copper oxide and manganese dioxide in order to make the BNT-BT-ST piezoelectric ceramic function as a highly efficient piezoelectric device.

(Laminated piezoelectric device)
In addition, the lead-free piezoelectric ceramic of the present invention provides a great effect when used in a laminated piezoelectric device in which electrodes and piezoelectric layers are alternately laminated. BNT-BT-ST piezoelectric ceramics have the advantage of simple solid-phase sintering and are suitable for lamination. An example of the multilayer piezoelectric device is a multilayer piezoelectric transformer. Multilayer piezoelectric transformers are small and can provide a large step-up ratio, so that there is an increasing demand for backlights for liquid crystal displays. By producing a multilayered piezoelectric transformer using BNT-BT-ST piezoelectric ceramics as a piezoelectric layer using copper oxide and manganese dioxide, a multilayered piezoelectric transformer containing no lead can be obtained.

  As an example of a manufacturing method of a multilayer piezoelectric device using a lead-free piezoelectric ceramic using copper oxide and manganese dioxide, a manufacturing method of a multilayer piezoelectric transformer using a BNT-BT-ST piezoelectric ceramic as a piezoelectric layer is as follows. Explained.

First, appropriate amounts of Bi ₂ O ₃ , Na ₂ CO ₃ , BaTiO ₃ , SrCO ₃ and TiO ₂ are blended and mixed uniformly by a ball mill or the like. The slurry after mixing is dried and calcined at 800 ° C. The calcining temperature is preferably 800 ° C. or lower. For example, the dielectric loss of a sintered compact becomes small by setting it as 800 degrees C or less.

Next, the calcined body is pulverized with a ball mill or the like to dry the slurry. Then, a predetermined amount of 0.1% to 2% by weight of copper oxide and a predetermined amount of 0.1% to 2% by weight of manganese dioxide are added, and a binder is mixed to form a green sheet. BNT-BT-ST piezoelectric ceramics having a density of 5.5 × 10 ³ kg / m ³ or more can be obtained by adding 0.1% by weight or more of copper oxide and firing at 1000 ° C. or less. On the other hand, the conductivity by copper oxide can be suppressed by setting it as 2 weight% or less. Further, by adding manganese dioxide, it is possible to provide lead-free piezoelectric ceramics that can be driven with high efficiency.

  The green sheet can be produced by a known method such as a doctor blade method, an extrusion method, a calendar roll method, or the like. The thickness of the green sheet is adjusted so as to have a desired thickness after firing, for example. The green sheet thus manufactured is punched or cut in consideration of firing shrinkage and processing margin, and a printing sheet having a predetermined shape suitable for the rectangular shape of the piezoelectric transformer to be manufactured is obtained. An internal electrode paste containing Ag and Pd is printed by a screen printing method or the like on a half region in the longitudinal direction of the printing sheet. Here, in the printing of the internal electrode paste of Ag—Pd, for example, the printing thickness is adjusted to be about 2 μm to 5 μm after firing. Further, it is desirable to determine a pattern for printing the internal electrode paste so that the internal electrodes to be formed can be easily connected every other layer thereafter.

  Next, the printing sheets on which the internal electrode paste is printed are aligned and laminated by a predetermined number, and the printing sheets thus laminated are thermocompression bonded by a hot press or the like to be integrated. In this way, the press body in which the sheet is press-fitted in accordance with a predetermined position is punched to produce a molded body.

  Subsequently, the molded body is fired at 1100 ° C. or less according to a predetermined temperature pattern. If necessary, the shape and the shape of the fired body are adjusted by grinding or polishing. Next, using an Ag-Pd paste or the like, the internal electrodes of the input part are connected every other layer to form a pair of electrodes, and the output electrode is formed on the end face of the output part, and then at a predetermined temperature. The Ag-Pd paste or the like is baked by processing. Usually, the baking treatment of the Ag—Pd paste or the like is performed at a temperature lower than the firing temperature. And a lead wire is attached to the electrode formed as needed. The obtained sintered body is subjected to polarization treatment. A predetermined voltage is applied between the pair of electrodes provided in the input unit and the electrode provided on the end face of the output unit to perform polarization processing of the output unit, and then the pair of electrodes provided in the input unit A piezoelectric transformer is manufactured by applying a predetermined voltage between the electrodes and performing polarization processing of the input portion.

  The polarization process is performed for a predetermined time at a predetermined temperature lower than the Curie point of the piezoelectric ceramic. In this way, a lead-free BNT-BT-ST laminated piezoelectric transformer can be manufactured. Thus, a press body in which piezoelectric layers made of BNT-BT-ST piezoelectric ceramics and internal electrode layers made of Ag-Pd or the like are alternately laminated is integrally fired to produce a lead-free laminated piezoelectric transformer. Can be manufactured.

It is a table | surface which shows the characteristic of the BNT-BT-ST type piezoelectric ceramic of each composition. It is a graph which shows the relationship between the addition amount of copper oxide, and a density about a BNT-BT-ST type piezoelectric ceramic. It is a graph which shows the relationship between the addition amount of copper oxide, and a density about a BNT-BT-ST type piezoelectric ceramic. It is a table | surface which shows the relationship between each baking temperature and each addition amount, and an electromechanical coupling coefficient about a BNT-BT-ST type piezoelectric ceramic. It is the table | surface which put together the characteristic of the BNT-BT-ST type piezoelectric ceramic sample. Regarding the lead-free piezoelectric ceramic of the present invention, (a) a table showing the relationship between the addition amount of manganese dioxide and the density and mechanical quality factor Qm of the lead-free piezoelectric ceramic, (b) the addition amount of manganese dioxide and the lead-free It is a graph which shows the relationship with the mechanical quality factor Qm of a piezoelectric ceramic. (A) Table showing the relationship between the amount of copper oxide added and the density and mechanical quality factor Qm of lead-free piezoelectric ceramics, (b) shows the amount of manganese dioxide added and the mechanical quality of lead-free piezoelectric ceramics It is a graph which shows the relationship with the coefficient Qm. It is a table | surface which shows the relationship between the addition amount of a copper oxide and manganese dioxide, the density of a lead-free piezoelectric ceramic, and the mechanical quality factor Qm.

Claims (3)

For a material mainly composed of a compound represented by the composition of x (Bi _0.5 Na _0.5 TiO ₃ ) -y (BaTiO ₃ ) -z (SrTiO ₃ ) (x + y + z = 1), 0. Piezoelectric layer made of lead-free piezoelectric ceramic obtained by adding 1% by weight or more and 2% by weight or less and adding 0.1% by weight or more and 2.0% by weight or less of manganese dioxide and firing at 1100 ° C. or less And an internal electrode layer made of Ag—Pd are alternately laminated and formed by integral firing . The multilayer piezoelectric device according to claim 1, wherein the lead- free piezoelectric ceramic has a mechanical quality factor of 200 or more. To a calcined powder of lead-free piezoelectric ceramics mainly composed of a compound represented by a composition of x (Bi _0.5 Na _0.5 TiO ₃ ) -y (BaTiO ₃ ) -z (SrTiO ₃ ) (where x + y + z = 1) On the other hand, an addition step of adding 0.1 to 2% by weight of copper oxide and adding 0.1 to 2.0% by weight of manganese dioxide;
A printing step of printing an Ag-Pd paste with an internal electrode pattern on a green sheet of the material obtained by the addition step ;
Method for producing a laminated piezoelectric device, which comprises a firing step of firing the shaped body obtained a green sheet which is coated with the Ag-Pd paste laminating a plurality at 1100 ° C. or less.

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