JP2000340855A - Piezoelectric ceramic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent delamination of a palladium electrode even if burnt at lower temperatures by a method wherein glass of a predetermined wt.% width with respect to a metal component included in an internal electrode is mixed in the internal electrode. SOLUTION: In order to raise a voltage step up ratio, a piezoelectric transformer has a lamination structure in which a primary part 10a has a piezoelectric layer 101 and an internal electrode layer 102. The piezoelectric layer 101 structuring a piezoelectric material and the internal electrode layer 102 electrically connecting with input electrodes 12, 13 are alternately laminated, and further in this internal electrode layer 102, an internal electrode layer 102A connected to the one input electrode 12 and an internal electrode layer 102B connected to the other input electrode 13 are alternately laminated. On the other hand, as for internal electrode paste, palladium particles of 100 wt.% having a specific surface area 0.5 to 2.3 m2/g, organic vehicles of 100 wt.%, and glass particles of 5 wt.% having mean particle size 1.4 μm at softening point 835 deg.C are mixedly kneaded with three rolls to form the internal electrode paste.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric ceramic device having an internal electrode containing palladium as a main component, and more particularly to a piezoelectric ceramic device manufactured by firing at a low temperature of 1150 ° C. or less.

[0002]

2. Description of the Related Art This type of piezoelectric ceramic device includes a piezoelectric transformer, a ceramic resonator, a ceramic filter,
It is widely applied to piezoelectric displacement elements, piezoelectric buzzers, ultrasonic vibrators, and the like.

A rectangular piezoelectric ceramic plate is used for a general piezoelectric transformer, and a primary side (input side) polarized in a thickness direction and a secondary side (output side) polarized in a length direction.
Consists of When an AC electric field of one-wavelength or half-wave resonance is applied, electric energy is converted into vibration energy on the low impedance primary side, and the vibration energy propagates to the high impedance secondary side, where the electric energy is converted. By being converted into energy, a high voltage is extracted from the secondary side.

In such a piezoelectric transformer, since the ratio Z2 / Z1 between the impedance Z1 on the primary side and the impedance Z2 on the secondary side is correlated with the boosting ratio V2 / V1, the impedance on the primary side is further reduced to increase the boosting ratio. In order to obtain a high-voltage piezoelectric transformer, the primary side has a laminated structure of a piezoelectric layer and an internal electrode layer.

[0005]

Incidentally, in the above-described piezoelectric transformer having a laminated structure of the piezoelectric layer and the internal electrode layer, when firing is performed in the air, the material constituting the internal electrode is not conventionally used. More noble metals were used. For example, palladium has been used at a firing temperature of about 1200 ° C., and a silver-palladium alloy has been used at a firing temperature of 900 to 1200 ° C.

However, when a silver-palladium alloy is used as the internal electrode material, there is a problem that the silver component diffuses into the piezoelectric layer, thereby deteriorating the piezoelectric characteristics of the piezoelectric transformer. On the other hand, the sintering temperature of palladium is 13
Since it is as high as 00 ° C., the firing temperature of the piezoelectric material is 900 to 12
When a palladium electrode is used at a low temperature of about 00 ° C., there is a problem that delamination (delamination) occurs between the piezoelectric layer and the internal electrode layer, and reliability is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and has as its object to provide a piezoelectric ceramic device capable of preventing delamination of a palladium electrode even at low temperature firing.

[0008]

According to the present invention, there is provided a piezoelectric ceramic device having an internal electrode containing palladium as a main component and firing at a temperature of 1150 ° C. or less. In the above, there is provided a piezoelectric ceramic device, wherein more than 1% by weight and less than 10% by weight of glass are added to the internal electrode with respect to a metal component contained in the internal electrode.

When palladium is used for the internal electrode of a piezoelectric ceramic device which is fired at a low temperature of 1150 ° C. or less, the sintering temperature of the palladium is as high as 1300 ° C., so that the shrinkage behavior with the piezoelectric material is different and delamination occurs. In the present invention, since more than 1% by weight and less than 10% by weight of glass are added, the sinterability of palladium is improved to approach the shrinkage ratio of the piezoelectric body, thereby delamination between the piezoelectric layer and the internal electrode layer. Is prevented.

Further, by adding glass, the adhesion between the piezoelectric layer and the internal electrode layer is improved, thereby also preventing delamination of both layers.

When the glass added to the internal electrode is 1% by weight or less, delamination occurs in the internal electrode layer and the piezoelectric layer, and when it is 10% by weight or more, the piezoelectric efficiency decreases.

(2) In the above invention, although not particularly limited, the softening point of the glass is 800 ° C. or more and 90 ° C.
It is more preferable that the temperature is 0 ° C. or lower. If the softening point of the glass is less than 800 ° C, delamination occurs in the internal electrode layer and the piezoelectric layer even when an appropriate amount is added, and delamination similarly occurs in the internal electrode layer and the piezoelectric layer even when the softening point exceeds 900 ° C. appear.

In the above invention, the average particle size of the glass is not less than 0.5 μm, but not particularly limited.
It is more preferable that it is not more than μm. If the average particle diameter of the glass is less than 0.5 μm, the pulverization productivity is poor, and if it exceeds 3 μm, screen printing on the piezoelectric sheet is adversely affected.

(3) The amount of glass to be added to the internal electrode in the present invention means the ratio to the weight of the metal component contained in the paste to be the internal electrode. It is% by weight based on the metal components including additives or impurities.

Further, the softening point of the glass in the present invention is:
When a fiber having a diameter of 0.55 to 0.75 mmφ and a length of 235 mm is heated at 4 to 6 ° C./min, it means the temperature at which the elongation becomes 1 mm / min.

The particle size of the glass in the present invention means an average particle size measured by a laser scattering method.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of the piezoelectric ceramic device of the present invention, and FIG. 2 is a sectional view taken along the line II-II of FIG.

In this embodiment, the piezoelectric ceramic device of the present invention is applied to a piezoelectric transformer 1 and has a rectangular plate-shaped device body 10. This device body 10
Is, for example, length L = 15-40 mm, width W = 3-7 m
m and thickness T = 0.7 to 1.5 mm.

An output electrode 11 made of a conductor layer is provided on one end face of the device body 10, and input electrodes 12, 1 also made of the conductor layer are provided on both other side faces.
3 are provided. A conductor such as silver is used for the input electrodes 12 and 13 and the output electrode 11, for example.
Its thickness is about 1 to 20 μm.

The portion where the input electrodes 12 and 13 are provided is the primary side 10a, the portion where the output electrode 11 is provided is the secondary side 10b, the primary side 10a is polarized in the thickness direction, and the secondary side 10b is Polarized in the longitudinal direction.

In particular, in the piezoelectric transformer 1 of this embodiment, in order to increase the voltage boost ratio, the primary side portion 10a is
01 and the internal electrode layer 102. That is, as shown in FIG.
[(Zn _1/3 Nb _2/3 ) x (Ti) y (Zr) z]
Piezoelectric layers 101 made of a piezoelectric material such as O ₃ (where x + y + z = 1) and internal electrode layers 102 electrically connected to the input electrodes 12 and 13 are alternately laminated. The layer 102 is formed by alternately stacking internal electrode layers 102A connected to one input electrode 12 and internal electrode layers 102B connected to the other input electrode 13. By adopting such a laminated structure, the primary side 10a
Since the impedance of is smaller than the single plate structure,
The voltage boost ratio V2 / V1 increases.

Then, when an AC electric field V1 of one-wavelength or half-wavelength resonance is applied to the input electrodes 12, 13, from the primary side 10a to the secondary side 10b, electric energy → vibration energy → electric energy in this order. The high voltage V2 is converted and propagated, and the high voltage V2 is extracted from the output electrode 11.

[0023]

EXAMPLE 1 Lead oxide PbO, titanium oxide TiO ₂ ,
Using zirconium oxide ZrO ₂ , zinc oxide ZnO, niobium oxide Nb ₂ O _5, and manganese carbonate MnCO ₃ , these powders were blended according to the following composition formula, and each blend was wet-mixed with a ball mill.

[0024]

Pb [(Zn _1/3 Nb _2/3 ) x (Ti) y (Zr) z] O ₃ + αMnCO ₃ (where x + y + z = 1, 0.5 wt% ≦ α ≦ 1.5
weight%)

After thoroughly mixing the starting materials, the mixture is calcined at 850 ° C. for 2 hours in air (both at a temperature rising rate and a cooling rate of 200 ° C./hour), and water is added to the calcined product obtained. And wet-pulverized using a ball mill.

This piezoelectric material can be fired at a relatively low temperature. 3.5% by weight of an acrylic resin as an organic binder, 35% by weight of a mixed organic solvent, 100% by weight of this piezoelectric material, and a plasticizer 2% by weight of benzyl butyl phthalate was added and mixed well to obtain a piezoelectric paste.

On the other hand, for the internal electrode paste, palladium particles 100 having a specific surface area of 0.5 to 2.3 m ² / g were used.
% By weight, 100% by weight of the organic vehicle, and a softening point of 83%.
5% by weight of glass powder having an average particle size of 1.4 μm at 5 ° C.,
Was kneaded with three rolls to obtain an internal electrode paste.

With respect to the external electrode paste, 100% by weight of silver particles having a specific surface area of 0.8 to ³ m ² / g and 67% by weight of an organic vehicle were kneaded to obtain an external electrode paste.

Next, using the above-mentioned piezoelectric paste, P
A green sheet having a thickness of 30 to 35 μm was formed on the ET film, and the above-mentioned internal electrode paste was printed thereon, and then the green sheet was peeled off from the PET film. Next, a plurality of the green sheets thus obtained were laminated and pressed and pressed to produce a green chip. The number of stacked green sheets having internal electrodes was nine.

Next, the green chip is cut into a predetermined size and subjected to binder removal processing, firing and polarization processing.
A laminated piezoelectric transformer was obtained.

The binder removal treatment is performed at a heating time of 15 ° C. /
The test was performed under the conditions of a time, a holding temperature of 350 ° C., a holding time of 3 hours and an air atmosphere. The firing was performed at a heating rate of 200 ° C./hour, a holding temperature of 1060 ° C., a holding time of 2 hours, and a cooling rate of 2 hours.
The test was performed at 00 ° C./hour in an air atmosphere.

Next, after the sides of the laminated piezoelectric ceramic fired body are polished by sandblasting, the external electrode paste is transferred to the end faces and the side faces, and fired at 700 ° C. for 10 minutes in an air atmosphere to form the external electrodes. Formed. Then, the input side and the output side were separately polarized at a voltage of 2 kV / mm to obtain a sample of the laminated piezoelectric transformer (hereinafter, also referred to as a piezoelectric transformer sample). The size of each sample was 4.5 mm in width × 32 mm in length × 1 mm in thickness, the thickness of the piezoelectric layer was 100 μm, and the thickness of the internal electrode was 3 μm.

For each sample of the piezoelectric transformer thus obtained, the transformer efficiency was measured, and the cross section was observed for the presence or absence of delamination using an optical microscope and an SEM. ”, Delamination was observed as“ x ”). Table 1 shows the results.

The transformer efficiency was measured using a measuring device shown in FIG. That is, the power Pi of the primary side 10a
n is the voltage Vi applied to the two input electrodes 12 and 13
n was measured with an oscilloscope, and the current Iin was measured with a current probe. These measured values were substituted into the following equation to determine the primary-side power Pin.

The electric power Pout of the secondary side 10b is obtained by measuring the current value Iout flowing through the output electrode 11 with an ammeter, and substituting it into the following equation together with a known load resistance RL. I asked. And these Pin
And the transformer efficiency η was determined from Pout.

[0036]

## EQU2 ## Pin = (Vin / 2√2) × (Iin / 2√)
2) × cos θ where θ is the phase difference between Vin and Iin Pout = Iout ² × RL η = Pout / Pin

Example 2 A piezoelectric transformer sample was prepared under the same conditions as in Example 1 except that the softening point of the glass added to the internal electrode paste was 900 ° C., and the transformer efficiency and the presence or absence of delamination were determined. Was observed. Table 1 shows the results.

Comparative Example 1 A piezoelectric transformer sample was prepared under the same conditions as in Example 1 except that no glass was added to the internal electrode paste, and the transformer efficiency and the presence or absence of delamination were observed. Table 1 shows the results.

Comparative Example 2 A piezoelectric transformer sample was prepared under the same conditions as in Example 1 except that the softening point of the glass added to the internal electrode paste was set at 795 ° C., and the transformer efficiency and delamination were measured. The presence or absence was observed. Table 1 shows the results.

Comparative Example 3 A piezoelectric transformer sample was prepared under the same conditions as in Example 1 except that the softening point of the glass added to the internal electrode paste was 930 ° C., and the transformer efficiency and the delamination were measured. The presence or absence was observed. Table 1 shows the results.

Comparative Example 4 In Example 1, 70% Ag-30% was used as the internal electrode.
A piezoelectric transformer sample was prepared under the same conditions as in Example 1 except that a Pd alloy was used and no glass was added.
Trans efficiency and the presence or absence of delamination were observed. Table 1 shows the results.

[0042]

[Table 1]

From the above results, it can be seen that the sample having no glass added to the internal electrode paste (Comparative Example 1) and the glass having a softening point of 800 even when an appropriate amount (5% by weight) of glass was added. C. (Comparative Example 2) or 900
When the temperature was higher than 0 ° C. (Comparative Example 3), delamination was observed in both the internal electrode layer and the piezoelectric layer. On the other hand, no delamination was observed and the transformer efficiency was a suitable value in the case where glass having a softening point of 800 ° C. or more and 900 ° C. or less was added (Examples 1 and 2). In addition, the transformer efficiency of the device using the internal electrode made of a silver-palladium alloy (Comparative Example 4) was deteriorated.

Example 3 Next, an appropriate amount of glass to be added to the internal electrode was confirmed. That is, the same softening point as in the first embodiment is 83.
A piezoelectric transformer sample was prepared under the same conditions as in Example 1 except that the amount of glass added at 5 ° C. was 3% by weight, and the transformer efficiency and the presence or absence of delamination were observed. Table 2 shows the results.

Example 4 The same amount of glass having a softening point of 835 ° C.
A piezoelectric transformer sample was prepared under the same conditions as in Example 1 except that the weight% was used, and the transformer efficiency and the presence or absence of delamination were observed. Table 2 shows the results.

Comparative Example 5 The same amount of glass having a softening point of 835 ° C.
A piezoelectric transformer sample was prepared under the same conditions as in Example 1 except that the weight% was used, and the transformer efficiency and the presence or absence of delamination were observed. Table 2 shows the results.

Comparative Example 6 The same amount of glass having a softening point of 835 ° C.
A piezoelectric transformer sample was prepared under the same conditions as in Example 1 except that the weight was set to 0% by weight, and the transformer efficiency and the presence or absence of delamination were observed. Table 2 shows the results.

[0048]

[Table 2]

From the above results, when the glass added to the internal electrode paste is 1% by weight or less (Comparative Example 5),
Delamination was observed between the internal electrode layer and the piezoelectric layer. When the amount of glass added was 10% by weight or more (Comparative Example 6), the transformer efficiency deteriorated. On the other hand, when the amount of glass added was more than 1% by weight and less than 10% by weight (Examples 1, 3, and 4), no delamination was observed, and the transformer efficiency was also a suitable value.

[0050]

As described above, according to the present invention, since more than 1% by weight and less than 10% by weight of glass are added, the sinterability of palladium is improved, and the shrinkage ratio of the piezoelectric body approaches. Thus, delamination between the piezoelectric layer and the internal electrode layer is prevented.

Further, the addition of glass improves the adhesion between the piezoelectric layer and the internal electrode layer, thereby also preventing the delamination of both layers.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a piezoelectric ceramic device according to the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a block diagram showing an apparatus for measuring transformer efficiency according to an example of the present invention and a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piezoelectric transformer 10 Device main body 10a ... Primary side 101 ... Piezoelectric layer 102, 102A, 102B ... Internal electrode layer 10b ... Secondary side 11 ... Output electrode 12, 13 ... Input electrode

Claims (3)

[Claims] 1. A piezoelectric ceramic device having an internal electrode containing palladium as a main component and fired at a temperature of 1150 ° C. or less, wherein 1% by weight based on a metal component contained in the internal electrode.
A piezoelectric ceramic device, wherein more than 10% by weight of glass is added to the internal electrode. 2. The glass has a softening point of at least 800 ° C.
The piezoelectric ceramic device according to claim 1, wherein the temperature is not higher than 00C. 3. The piezoelectric ceramic device according to claim 1, wherein the average particle size of the glass is 0.5 μm or more and 3 μm or less.