JP5392603B2 - Method for manufacturing piezoelectric ceramic electronic component - Google Patents

Description

  The present invention relates to a method for manufacturing a piezoelectric ceramic electronic component, and more particularly to a method for manufacturing a piezoelectric ceramic electronic component that requires a high mechanical quality factor such as a piezoelectric oscillator, a piezoelectric transformer, an ultrasonic motor, and a piezoelectric filter.

Conventionally, a ceramic material mainly composed of Pb (Zr, Ti) O ₃ (hereinafter referred to as “PZT”) made of a solid solution of a ferroelectric PbTiO ₃ and an antiferroelectric PbZrO ₃ is a piezoelectric material. Widely used in ceramic electronic components.

For example, Patent Document 1, the general formula (α · Pb-β · Me ) {(Mn 1/3 Nb 2/3) x Zr y Ti z} O 3 ( where, Me is Sr, Ba, and the Ca At least one selected from the group, the Pb component mol content α, the Me component mol amount β, the Mn _1/3 Nb _2/3 component mol amount x, and the Zr component mol amount y. , Ti content mol amount z of 0.985 ≦ α ≦ 1.055, 0.000 ≦ β ≦ 0.100, 0.045 ≦ x ≦ 0.200, 0.290 ≦ y ≦ 0.425, respectively. 0.475 ≦ z ≦ 0.580, (x + y + z = 1), and 0.15% to 0.500% Mn oxide, 0.000% to 0,010 in terms of weight%. There has been proposed a method for producing a piezoelectric ceramic composition containing 1% Cr oxide and 0.000% to 0.090% Si oxide.

  In Patent Document 1, in the PZT-based piezoelectric ceramic composition, mechanical quality factor Qm is improved by substituting part of Zr and Ti with Mn and Nb. As a result, a piezoelectric ceramic composition suitable for piezoelectric ceramic electronic components that require a high mechanical quality factor Qm, such as a piezoelectric transformer, an ultrasonic motor, and a piezoelectric filter, is obtained.

Further, Patent Document 2, the general formula _{Pb a (Mn 1/3 Nb 2/3)} x Ti y Zr z O 3 ( hereinafter. Referred to as "PMN-PZT") as a main component represented by the sub A piezoelectric ceramic composition in which 0.3 to 0.8% by weight of Mn ₃ O ₄ is added as a component to 100% by weight of the main component has been proposed.

  In Patent Document 2, a predetermined amount of Mn is added to a PMN-PZT material, thereby improving heat resistance.

JP 2003-128462 A JP 2000-103694 A

  In recent years, this type of piezoelectric ceramic electronic component has been improved in performance and size, and a multilayer type in which an internal electrode is formed inside a piezoelectric ceramic body has been widely used. In the case of such a laminated type, it is widely performed by alternately laminating ceramic layers and conductive layers and co-firing the conductive layers and ceramic layers.

  Thus, when co-firing and manufacturing a piezoelectric ceramic electronic component, it is desirable to use Cu or Ag-Pd alloy with low Pd content as an internal electrode material from the surface of material cost.

  However, the piezoelectric ceramic electronic parts using the PMN-PZT material as the main component as in Patent Documents 1 and 2 have a high mechanical quality factor Qm, but have poor sinterability and are fired at a high temperature of 1100 ° C. or higher. Had to do. For this reason, low-melting-point inexpensive Cu cannot be used as the internal electrode material, and even when an Ag—Pd alloy is used, it is expensive because it contains 30% by weight or more of high-melting-point Pd. An Ag—Pd alloy had to be used, leading to an increase in cost.

  The present invention has been made in view of such circumstances, and a piezoelectric ceramic electronic component having a desired piezoelectric characteristic can be obtained even when sintered at a low temperature, and the cost can be reduced. It aims at providing the manufacturing method of components.

  In order to improve the mechanical quality factor Qm, it is known that it is effective to dissolve Mn in the PZT material.

Therefore, the present inventor has made Mn and Nb solid solution in PZT and conducted earnest research under various firing conditions. As a result, PMN-PZT after sintering was prepared so that the ratio α / β of the molar ratio α of Mn and the molar ratio β of Nb exceeded 0.50, and the obtained raw material powder was molded Then, the compact is fired in a reducing atmosphere having an oxygen partial pressure PO ₂ of 0.25 Pa or less, thereby improving the sinterability and sintering at a low temperature of less than 1050 ° C. while maintaining good piezoelectric properties. I got the knowledge that I can.

The present invention has been made on the basis of such knowledge, and a method for manufacturing a piezoelectric ceramic electronic component according to the present invention includes a ceramic raw material containing at least a Pb compound, a Mn compound, an Nb compound, a Zr compound, and a Ti compound. , Mn blending molar ratio α and Nb blending molar ratio β is blended so that the ratio α / β exceeds 0.50, and the sintered main component is represented by the general formula Pb {(Mn, Nb), Zr, A raw material production step of producing a ceramic raw material powder represented by Ti} ₃ ; a molding step of producing a ceramic molded body by molding the ceramic raw material powder; and a reducing atmosphere having an oxygen partial pressure of 0.25 Pa or less And a firing step of firing the ceramic molded body.

  In addition, the method for manufacturing a piezoelectric ceramic electronic component according to the present invention includes a conductive material mainly composed of one conductive material of any one of an Ag-Pd alloy having a Cu and Pd content of 10 wt% or less. Conductive paste production process for producing paste, conductive film formation process for forming conductive film by applying conductive paste to ceramic molded body, and laminating process for laminating ceramic molded body on which conductive film is formed The firing step is characterized by firing the laminated ceramic molded body.

According to the method for manufacturing a piezoelectric ceramic electronic component, a ceramic raw material containing at least a Pb compound, a Mn compound, an Nb compound, a Zr compound, and a Ti compound is mixed with a ratio of a molar ratio α of Mn to a molar ratio β of Nb. a raw material preparation step of preparing a ceramic raw material powder in which α / β exceeds 0.50 and the sintered main component is represented by the general formula Pb {(Mn, Nb), Zr, Ti} ₃ ; The ceramic raw material powder is molded to produce a ceramic molded body, and the ceramic partial body is fired in a reducing atmosphere having an oxygen partial pressure of 0.25 Pa or less. It becomes possible to sinter at a low temperature of less than 1050 ° C. while maintaining excellent piezoelectric characteristics.

  In addition, a conductive paste manufacturing step of preparing a conductive paste whose main component is one of an Ag—Pd alloy having a Cu and Pd content of 10 wt% or less, and the ceramic A conductive film forming step of forming the conductive film by applying the conductive paste to the formed body; and a stacking step of stacking the ceramic formed body on which the conductive film is formed, wherein the firing step is the stacked layer Since the ceramic molded body is fired, it is possible to co-fire the Ag-Pd alloy having a Cu or Pd content of 10% by weight or less and the ceramic molded body at a low temperature. Therefore, co-firing can be performed using an inexpensive Cu or a relatively inexpensive Ag—Pd alloy having an expensive Pd content of 10% by weight or less as the internal electrode material, thereby reducing the cost of the product. Can be planned.

It is sectional drawing which shows one Embodiment of the piezoelectric oscillator as a piezoelectric ceramic electronic component produced using the manufacturing method of this invention. It is a figure which shows the relationship between the calcination temperature and sintering density of the sample numbers 1-5 produced in the Example.

  Next, an embodiment of the present invention will be described in detail.

  FIG. 1 is a cross-sectional view showing an embodiment of a piezoelectric oscillator as a piezoelectric ceramic electronic component manufactured by using the manufacturing method of the present invention.

  In this piezoelectric oscillator, an internal electrode 2 is embedded in a piezoelectric ceramic body 1, and external electrodes 3 and 4 are formed on the surface of the piezoelectric ceramic body 1.

  The piezoelectric ceramic body 1 has two piezoelectric ceramics 1a and 1b. The internal electrode 2 is formed so as to cover the majority surface of the piezoelectric ceramic body 1b and to expose one end of the piezoelectric ceramic body 1b, and the piezoelectric ceramic 1a is laminated on the internal electrode 2 and the piezoelectric ceramic body 1b. It has become. One external electrode 3 is formed on one side surface of the piezoelectric ceramic body 1 so as to be electrically connected to the internal electrode 2. The other external electrode 4 is formed on both main surfaces so that a part thereof is opposed to the internal electrode 2, and the two main surfaces are electrically connected via the other side surface portion. It is formed so that.

  The ceramic body 1 is polarized in the direction of the arrow P. When a voltage is applied between the external electrodes 3 and 4, an electric field is generated between the internal electrode 2 and the external electrode 4. It functions as a piezoelectric oscillator using the second harmonic.

  The piezoelectric ceramic body 1 is made of a PMN-PZT material having a perovskite structure. The internal electrode 2 is formed of a low melting point metal material that can be sintered at 1050 ° C. or less, for example, an Ag—Pd alloy having a Cu or Pd content of 10 wt% or less.

  Next, a method for manufacturing the piezoelectric oscillator will be described.

(1) Raw material powder preparation step As a ceramic raw material, a Pb compound containing Pb, a Mn compound containing Mn, an Nb compound containing Nb, a Zr compound containing Zr, and a Ti compound containing Ti are prepared. .

  Then, in the PMN-PZT after sintering, the ceramic raw material is adjusted so that the ratio α / β of the molar ratio α of Mn and the molar ratio β of Nb exceeds 0.50. Weigh. That is, the stoichiometric ratio of the ratio α / β is 0.50, but if the ratio α / β is 0.50 or less than 0.50 and the solid solution amount of Mn with respect to Nb is reduced, the sinterability Decreases and sintering at a low temperature of less than 1050 ° C. becomes difficult. Further, when the ratio α / β exceeds 0.50, an improvement in heat resistance can be expected. For this reason, in the PMN-PZT which is the main component, each ceramic raw material is weighed so that the ratio α / β of the molar ratio α of Mn and the molar ratio β of Nb exceeds 0.50.

  Then, these weighed materials are put into a ball mill containing a pulverizing medium such as partially stabilized zirconia, sufficiently wet-mixed with pure water or ethanol as a solvent, dehydrated, and then subjected to temperature in an air atmosphere. Calcination is performed at 800 ° C. to 1000 ° C. to obtain ceramic raw material powder.

(2) Forming process After this ceramic raw material powder is crushed, an organic binder such as polyvinyl alcohol resin is added, and it is again put into a ball mill contained in a grinding medium and sufficiently wet crushed to produce a slurry. .

  Next, the slurry is subjected to a molding process such as a doctor blade method to produce a ceramic green sheet.

  Next, for example, a conductive paste containing as a main component a low melting point material such as Ag—Pd prepared with a Cu or Pd content of 10 wt% or less is prepared. And after apply | coating the said electrically conductive paste to a part of said ceramic green sheet | seat, and forming a conductive layer, the ceramic green sheet | seat in which the conductive layer is not formed is laminated | stacked on the upper surface of this ceramic green sheet | seat, and it pressure-bonds and ceramics. A molded body is produced.

(3) Firing step The ceramic molded body is fired at a low temperature of less than 1050 ° C. in a reducing atmosphere having an oxygen partial pressure PO ₂ of 0.25 Pa or less. As a result, the internal electrode 2 is embedded, and Mn and Nb are dissolved in the B site ((Zr, Ti) site) of PZT, so that a ceramic sintered body mainly composed of PMN-PZT is produced.

Here, the firing atmosphere was performed in a reducing atmosphere having an oxygen partial pressure PO ₂ of 0.25 Pa or less for the following reason.

PMN-PZT (Pb ((Mn, Nb), Zr, Ti) O ₃ ) forms a perovskite structure by dissolving Mn ²⁺ in the B site. However, since Mn ³⁺ and Mn ⁴⁺ are more stable in the air, manganese oxide is difficult to be dissolved in the B site when fired in the air. For this reason, in order to obtain a sintered ceramic body having desired piezoelectric characteristics and good sinterability, firing at a high temperature is required.

On the other hand, when firing in a reducing atmosphere, Mn ³⁺ and Mn ⁴⁺ are reduced to Mn ²⁺ , so that Mn can be easily dissolved in the B site of PMN-PZT, thereby reducing the temperature. Firing is possible.

However, when the oxygen partial pressure PO ₂ exceeds 0.25 Pa, the base metal material having a low melting point such as Cu is inferior in oxidation resistance, so that the internal electrode material may be oxidized when co-fired. .

For this reason, it is necessary to co-fire in a reducing atmosphere having an oxygen partial pressure PO ₂ of 0.25 Pa or less.

(4) External electrode formation process
Sputtering is performed on both main surfaces of the ceramic sintered body using Ag or Cu as a target to form an electrode for polarization treatment. Next, a predetermined DC voltage is applied between both main surfaces in an insulating oil at 150 ° C. to perform polarization treatment, and then the polarization treatment electrode is removed by etching, whereby the piezoelectric ceramic element having the internal electrode 2 embedded therein is removed. Obtain body 1.

  After that, the internal electrode 2 is appropriately cut so as to be arranged at a predetermined position, and then sputtered again using Ag as a target to form the external electrodes 3 and 4 on both main surfaces of the piezoelectric ceramic body 1, thereby A piezoelectric oscillator is manufactured.

  In this way, the method of manufacturing the piezoelectric resonator according to the present invention is prepared so that the ratio α / β of the molar ratio α of Mn and the molar ratio β of Nb exceeds 0.50. A raw material production process for producing a ceramic raw material powder whose component is represented by PMN-PZT, a molding process for producing a ceramic molded body by molding the ceramic raw material powder, and a reducing atmosphere having an oxygen partial pressure of 0.25 Pa or less Since it includes a firing step of firing the ceramic molded body below, it can be sintered at a low temperature of less than 1050 ° C. while maintaining desired good piezoelectric properties. Therefore, Cu and Pd can be co-fired with an Ag—Pd alloy having a low content (10% by weight or less), and the manufacturing cost can be reduced.

  The present invention is not limited to the above embodiment. For example, a trace amount of Fe, Cl, Si, Al or the like may be contained as an inevitable impurity as long as the characteristics of the present invention are not impaired.

  Further, as a low melting point metal material that is inexpensive and can be co-fired at a temperature lower than 1050 ° C., an Ag—Pd alloy having a Cu and Pd content of 10 wt% or less is representative, but desired piezoelectric characteristics and temperature characteristics It is also possible to use other low-melting-point metal materials other than these as long as the above can be ensured.

  Further, specific forms of the ceramic raw material such as Pb compound, Ti compound, Mn compound, Nb compound, and Zr compound may be any of carbonate, hydroxide, and oxide.

  Moreover, in the said embodiment, although the piezoelectric ceramics 1a and 1b are produced by what is called a sheet method, you may produce the piezoelectric ceramics 1a and 1b by press molding.

  In the above embodiment, the piezoelectric oscillator is exemplified as the piezoelectric element, but the same applies to the piezoelectric transformer, the piezoelectric filter, and the like.

  Next, examples of the present invention will be specifically described.

First, Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , MnCO ₃ , and Nb ₂ O ₅ were prepared as ceramic raw materials.

  Next, these ceramic raw materials are weighed and wet-mixed so that the sintered main component has the composition shown in Table 1, and then dehydrated with a Nutsche suction filter, and then at a temperature of 800 to 1000 ° C. The shellac raw material powder was obtained by calcining for about 2 hours.

  Next, this ceramic raw material powder, a solvent (ethanol) and an organic binder (polyvinyl alcohol resin) are mixed to produce a slurry, and then molded using a doctor blade method to obtain a ceramic green sheet having a thickness of 50 μm. Produced.

  Next, a ceramic green sheet was punched out to a predetermined size, laminated, and pressed to obtain a ceramic molded body. And this ceramic molded object was heated to 500 degreeC, and the binder removal process was performed.

Then, for each sample, the oxygen partial pressure PO ₂ and ^{1.0 × 10 4 ~1.0 × 10 -2} Pa, the firing temperature was fired 4 hours set in a range of 900 to 1300 ° C., Sample No. 1 A ceramic sintered body of ˜5 was obtained.

  Subsequently, about the sample of sample numbers 1-5, the sintered density in each calcination temperature was calculated | required using the Archimedes method.

Table 1 shows the respective compositions and the oxygen partial pressure PO ₂ of the sample No. 1-5.

FIG. 2 is a graph showing the relationship between the firing temperature and the sintered density for each of sample numbers 1 to 5, where the ● symbol indicates sample number 1, the □ symbol indicates sample number 2, the X symbol indicates sample number 3, and the Δ symbol indicates. Sample numbers 4 and ▪ indicate sample number 5. The horizontal axis is the firing temperature (° C.), and the vertical axis is the sintered density (g / cm ³ ).

As apparent from Table 1 and FIG. 2, Sample No. 2 was fired in an oxygen atmosphere with an oxygen partial pressure PO ₂ of 1.0 × 10 ⁵ Pa, and 1250 ° C. in order to saturate the sintered density. It was found that it was necessary to fire at the above high temperature.

In Sample No. 3, the ratio α / β of the Mn compounding molar ratio α and the Nb compounding molar ratio β exceeds 0.580 and 0.5, but the oxygen partial pressure PO ₂ is 1 as in Sample No. 2. It was baked in an air atmosphere of 0.0 × 10 ⁵ Pa, and it was found that it was necessary to fire at a high temperature of 1050 ° C. or higher in order to saturate the sintered density.

In Sample No. 4, as in Sample No. 3, the ratio α / β of the Mn blending molar ratio α and the Nb blending molar ratio β exceeds 0.588 and 0.5, but the oxygen partial pressure PO in the firing atmosphere _{It was found that 2} was 1.0 × 10 ⁴ Pa, close to the air atmosphere, and sintered at a high temperature of 1050 ° C. or higher in order to saturate the sintered density.

Sample No. 5 was fired in a reducing atmosphere having an oxygen partial pressure PO ₂ of 1.0 × 10 ⁻² Pa, but the ratio α / β between the molar ratio α of Mn and the molar ratio β of Nb was 0. It was found that it was necessary to fire at a high temperature of 1200 ° C. or higher in order to saturate the sintered density.

On the other hand, in sample No. 1, the ratio α / β of the molar ratio α of Mn and the molar ratio β of Nb is 0.580, and the oxygen partial pressure PO _{2 in the} firing atmosphere is 1.0 × 10 ^−2. Since firing was performed in a reducing atmosphere of Pa, it was found that sintering density was saturated by firing at a low temperature of 950 ° C.

  Next, each sample of sample numbers 1 to 5 was polished so that the ceramic sintered body had a predetermined thickness, and then an external electrode was formed using an Ag paste. In this embodiment, the thick film electrode is formed using Ag paste, but the thin film electrode may be formed by sputtering, vapor deposition or the like.

  Next, each sample was subjected to a polarization treatment by applying a DC electric field of 3.0 kV / mm and cut into rectangular shapes to obtain piezoelectric ceramic electronic components of sample numbers 1 to 5.

  The obtained piezoelectric ceramic electronic components of sample numbers 1 to 5 were 13.0 mm in length, 3.0 mm in width, and 0.6 mm in thickness.

Next, for each of the samples Nos. 1 to 5, a voltage of 0.01 V was used using an impedance analyzer (manufactured by Agilent Technologies: HP-4194A) in accordance with the Japan Electronic Materials Industries Association Standard: EMAS-6100. Relative dielectric constant εr (= ε ₃₃ ^T / ε _o ), electromechanical coupling coefficient k ₃₁ , and mechanical quality factor Qm were obtained.

And, among the sample of the sample No. 1-5, electromechanical coupling factor k ₃₁ compared the piezoelectric properties at the firing temperature at which the maximum.

  Table 2 shows the firing conditions and measured values of these samples.

Comparing Sample No. 1 and Sample Nos. 2 to 4, it was found that Sample No. 1 can obtain good piezoelectric characteristics even when fired at a temperature lower by about 150 to 300 ° C. than Sample Nos. 2 to 4. This is because Sample Nos. 2 to 4 have a high oxygen partial pressure PO _{2 in the} firing atmosphere of 1.0 × 10 ^{4 to} 1.0 × 10 ⁵ Pa and are fired in an air atmosphere or a state close to the air atmosphere. On the other hand, it seems that Sample No. 1 is fired in a sufficiently reducing atmosphere with an oxygen partial pressure PO ₂ of 1.0 × 10 ⁻² .

Comparing Sample No. 1 and Sample No. 5, it was found that Sample No. 1 can obtain good piezoelectric characteristics even when fired at a temperature lower by about 250 ° C. than Sample No. 5. Both sample numbers 1 and 5 are fired in a reducing atmosphere having an oxygen partial pressure PO ₂ of 1.0 × 10 ⁻² , but sample number 1 has a molar ratio α of Mn and a molar ratio β of Nb. It seems that the ratio α / β exceeds 0.580 and 0.50, whereas the ratio α / β of Sample No. 5 is lower than 0.499 and 0.50.

From the above, in the PMN-PZT material, the composition is blended so that the ratio α / β of the blending molar ratio α of Mn and the blending molar ratio β of Nb exceeds 0.50, and the oxygen partial pressure PO ₂ is 1. It has been found that by firing in a reducing atmosphere of 0 × 10 ⁻² or less, sintering can be performed at a low temperature of less than 1050 ° C., and a piezoelectric ceramic electronic component having good piezoelectric characteristics can be obtained.

  And since it can be fired at a low temperature of 1050 ° C. or less, it can be co-fired even when using an Ag—Pd alloy having a Cu or Pd content of 10% by weight or less, thereby reducing the cost. I found that I can plan.

  Even if the PMN-PZT material is fired at a low temperature, a piezoelectric ceramic electronic component having a desired piezoelectric characteristic having a high mechanical quality factor Qm can be obtained, and the cost can be reduced.

Claims (2)

A ceramic raw material containing at least a Pb compound, a Mn compound, an Nb compound, a Zr compound, and a Ti compound is prepared such that the ratio α / β of the Mn compounding molar ratio α and the Nb compounding molar ratio β exceeds 0.50. And a raw material preparation step of preparing a ceramic raw material powder whose main component after sintering is represented by the general formula Pb {(Mn, Nb), Zr, Ti} O ₃ ;
A molding process for producing a ceramic molded body by molding the ceramic raw material powder,
And a firing step of firing the ceramic molded body in a reducing atmosphere having an oxygen partial pressure of 0.25 Pa or less. A conductive paste preparation step of preparing a conductive paste whose main component is one of an Ag-Pd alloy having a Cu and Pd content of 10 wt% or less, and the ceramic molded body A conductive film forming step of forming the conductive film by applying the conductive paste to the substrate, and a stacking step of stacking the ceramic molded body on which the conductive film is formed,
2. The method for manufacturing a piezoelectric ceramic electronic component according to claim 1, wherein the firing step comprises firing the laminated ceramic molded bodies.

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