JP2957537B2 - Piezoelectric and piezoelectric devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic mainly comprising lead zirconate titanate zinc niobate, and is particularly useful for a piezoelectric ceramic which requires mechanical strength.

[0002]

2. Description of the Related Art Heretofore, as a piezoelectric material, porcelain mainly composed of lead titanate and lead zirconate titanate, and further various additives have been added to the second component or the third component. A piezoelectric ceramic having improved piezoelectric characteristics, electric characteristics, and the like has been obtained.

[0003] By adding manganese oxide and cobalt oxide to lead zirconate titanate zinc niobate, it is possible to obtain a piezoelectric ceramic having excellent piezoelectric characteristics which can be used for an ultrasonic vibrator, a filter, and a piezoelectric transformer (Japanese Patent Publication No. 54-78). -1840
No. 0), and lead in which a part of lead is replaced by strontium, barium or the like (JP-A-62-154682).
No.), currently used for various purposes.

[0004] Although piezoelectric transformers, which have received particular attention in recent years, have been studied for a long time, they can be made smaller (particularly thinner) and lighter than conventional electromagnetic transformers, and can have higher efficiency and lower efficiency. It has the characteristic of noise. A typical piezoelectric transformer uses a rectangular piezoelectric ceramic plate, and generally has a structure including a primary (input) side polarized in a thickness direction and a secondary (output) side polarized in a length direction. is there.
By applying an AC electric field of one-wavelength or half-wave resonance to the piezoelectric transformer having this structure, electric energy is converted into vibration energy on the low impedance primary side.
This vibration energy is propagated to the high impedance secondary side, where it is converted to electrical energy and a high voltage is generated.

The piezoelectric ceramic has a great correlation between defects such as voids and mechanical strength. When driven with a large amplitude, such as a piezoelectric transformer, it is destroyed not only by an impact, but also when the input voltage is increased and excited with a large amplitude, the node is broken at a point called a node point where stress concentrates. In order to solve this, the particle diameter of the raw material powder is reduced to make the specific surface 10
There is a method in which the crystal grain diameter of the device is reduced to 1 μm or less by calcining at 650 ° C. or less while increasing the temperature to at least m ² / g (JP-A-6-112542). It is also possible to improve the mechanical strength by a method using a hot press.

[0006]

The pulverization of powder, which is a means for improving the mechanical strength, makes it difficult to handle the powder in producing a piezoelectric ceramic, and a new pulverization process is required. May join. In addition, when a hot press is used, the process becomes longer than in the process of manufacturing a normal piezoelectric ceramic, and the equipment becomes expensive. As a result, the finished product also becomes expensive.

Therefore, an object of the present invention is to provide a piezoelectric ceramic having a higher mechanical strength than conventional piezoelectric ceramics, simply and at low cost, without deteriorating the piezoelectric characteristics.

[0008]

This object is achieved by one of the following constitutions (1) and (2). (1) (Pb _1-a A _a ) (Zn _1/3 Nb _2/3 ) _x Ti _y Zr
_z O ₃ (provided that, A is calcium (Ca), strontium (Sr), at least one or more metal element selected from barium (Ba).) when expressed by the general formula,
0 ≦ a ≦ 0.1, x + y + z = 1, 0.05 ≦ x ≦ 0.
4, a main component satisfying 0.1 ≦ y ≦ 0.5, 0.2 ≦ z ≦ 0.6, and manganese oxide converted to MnO ₂ from 0.05 to
3 wt% and at least one of antimony oxide and niobium oxide are converted to Sb ₂ O ₃ and Nb ₂ O ₅ to give a total of 0.1 wt%.
And a sub-component containing 0.5 to 5% by weight. (2) A piezoelectric device using the piezoelectric ceramic of (1).

[0009]

The present invention is intended to improve the mechanical strength of a conventional lead zirconate titanate zinc niobate composition. The composition is mainly composed of a conventional lead zirconate titanate zinc niobate. The object has been achieved by adding at least one of antimony oxide and niobium oxide to a piezoelectric ceramic.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific configuration of the present invention will be described in detail. The piezoelectric ceramic with improved mechanical strength according to the present invention comprises (Pb _1-a A _a ) (Zn _1/3 Nb _2/3 ) _x Ti _y Z
r _z O ₃ (where A is at least one metal element selected from calcium (Ca), strontium (Sr), and barium (Ba), 0 ≦ a ≦ 0.1, x + y + z =
1, 0.05 ≦ x ≦ 0.4, 0.1 ≦ y ≦ 0.5, 0.
2 ≦ z ≦ 0.6) and a manganese oxide in an amount of 0.05 to 3% by weight, preferably 0.1 to 1.5% by weight in terms of MnO ₂ , of antimony oxide and niobium oxide. at least one, the sum 0.05-5% preferably in terms of Sb ₂ O ₃ and Nb ₂ O ₅ is made of a subcomponent including an 0.1~3wt%.

In the above composition, if the total amount of antimony oxide and niobium oxide is less than 0.05% by weight, the mechanical strength is not improved. If the total amount is more than 5% by weight, the piezoelectric properties are reduced and the mechanical strength is reduced. descend. Usually, the antimony oxide is added in the form of Sb ₂ O _{3 and} the niobium oxide is added in the form of Nb ₂ O ₅ . When both are added, the ratio is arbitrary.

The composition of the piezoelectric ceramic is determined by converting the amount of metal at the time of mixing the raw materials into a stoichiometric composition. The composition of the piezoelectric ceramic may slightly deviate from the above formula except for the ratio of Pb to A and the ratio of Zn + Nb to Ti and Zr.

Although these raw materials are usually used in the form of oxides, alkaline earth elements and Mn may be compounds such as carbonates and oxalates which become oxides by firing.

The Pb composite oxide having the above main composition forms a main phase of perovskite and has an average grain diameter of 0.5%.
.About.10 .mu.m.

The piezoelectric ceramic according to the present invention is suitable as a piezoelectric device used for, for example, a piezoelectric transformer or an ultrasonic motor.

For example, in the case of a Rosen type piezoelectric transformer used for a piezoelectric transformer, the structure is as shown in FIG. 1, for example. That is, the piezoelectric device 10 has a rectangular plate-shaped device main body 12 made of the piezoelectric ceramic. This device body 12 has a normal length L = 1.
5-40 mm, width W = 3-7 mm, thickness T = 0.7-1.5
mm. The piezoelectric device of the present invention is effective when the thickness is 2 mm or less, particularly 0.05 to 1 mm.

On one end face of the device body 12,
An output electrode 14 formed of a conductive layer is provided, and input and output electrodes 16, 1, 1 formed of a conductive layer are formed on upper and lower surfaces of a half of the device body 12 on a side remote from the output electrode 14.
8 are provided. These electrodes 14, 16, 18
Is made of a conductor such as silver (Ag) and has a thickness of 1 to 20 μm.
Degree. The portion of the device body 12 provided with the input electrodes 16 and 18, ie, the primary portion 12a, is pre-polarized in the thickness direction, while the remaining portion, ie, the secondary portion 12b, is polarized in the length direction. ing. The length L ₁ of the primary part 12a is about 7～20Mm.

With the above configuration, the voltage device 10 used in the piezoelectric transformer applies electric or vibrational energy by applying an AC electric field of one-wavelength or half-wavelength resonance from the input electrodes 16 and 18 to the primary part. , And are converted into electric energy in the order, and are converted into high voltage from the output electrode 14 and taken out. When the single-plate piezoelectric device 10 shown in FIG. 1 is used, the voltage can be 5 to 15 times.

In order to increase the conversion ratio of the voltage, as shown in FIG.
With the porcelain layers 12a-1 to 12a-n and the electrode layers 16, 18
Can be achieved according to the number of layers. It should be noted that also in the case of the piezoelectric device having this laminated structure, the outer size itself is the same as or equivalent to that of the single-plate voltage device shown in FIG.

The piezoelectric device having the above structure can be manufactured by an ordinary method. In the case of the laminated structure shown in FIG. 2, it is preferable that the porcelain and the electrodes (especially those disposed in the porcelain) are simultaneously fired. The firing temperature at this time is preferably from 1000 to 1150 ° C.

[0021]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention. Lead oxide (Pb
O), titanium oxide (TiO ₂ ), zirconium oxide (Z
rO ₂ ), zinc oxide (ZnO), niobium oxide (Nb
₂ O ₅ ), antimony oxide (Sb ₂ O ₃ ), manganese carbonate (MnCO ₃ ), calcium carbonate (CaCO ₃ ), strontium carbonate (SrCO ₃ ), barium carbonate (BaC)
Using O ₃ ), these powders were blended according to the following composition formula, and each blend was wet-mixed with a ball mill. The amounts of the element A, antimony oxide and niobium oxide are shown in Table 1.

(Pb _0.995 A _0.05 ) (Zn _1/3 Nb _2/3 )
_0.20 Ti _0.40 Zr _0.40 O ₃ + MnCO ₃ (1.0 wt% Mn
O _{2 conversion) + Sb 2 O 3 (awt} %) + Nb 2 O 5 (bwt%)

Next, after calcining the mixture at 800 to 900 ° C. for 2 hours, the calcined product was wet-pulverized with a ball mill. Next, a small amount of a binder is added to the calcined powder, and about 5 to
It was formed into a shape of 50 × 50 mm under a pressure of n / cm ² .

Next, these compacts are put in the range of 1000 to 1100
Firing in the air at a temperature of 2 ° C. for 2 hours gave a piezoelectric ceramic sample. The sample thus obtained was subjected to a density measurement, and it was confirmed that the density was 95% or more of the theoretical density.

Next, in order to conduct a strength test (three-point bending strength), it was processed to have a size of 2 mm × 4 mm and a thickness of 0.9 mm.
This test piece was subjected to a bending strength test according to JIS (R1601). The results are shown in Table 1.

In order to confirm the destruction in the piezoelectric transformer shape and the transformer characteristics (efficiency, step-up ratio, etc.), the length L = 3
After processing to 2 mm × width W = 4.5 mm and thickness T = 1 mm, a silver electrode was formed so as to have a Rosen type shown in FIG. 1, and the thickness direction (primary side portion) and the length direction (2 Next, polarization was performed in silicon oil at 120 ° C. for 30 minutes in an electric field of 2 kV / mm. Incidentally, the length L ₁ of the primary part was 16 mm. The sample thus prepared is held and input / output by a contact probe 20 (see FIG. 3) at a non-vibration point (a point where the stress is maximum) called a node point and an output electrode, and after measuring the transformer characteristics, the output side is turned off. 200 V was applied as a load while adjusting the resonance frequency (100 kHz) to the input side, and the presence or absence of destruction after 1 minute (destruction test) was examined. These results are also shown in Table 1.
In addition, in the column of the destruction test in Table 1, 0 was not destroyed,
Indicates broken.

[0027]

[Table 1]

Of the samples shown in Table 1, antimony oxide,
Samples having a total addition amount of niobium oxide of less than 0.01 wt% did not show any improvement in mechanical strength, and were broken in the above-mentioned breaking test. On the other hand, the samples having a total added amount exceeding 5 wt% did not show a significant improvement in mechanical strength, and were broken in the above-mentioned destructive test and the input / output conversion efficiency was lowered. Note that all of the destruction occurred at the node points of the secondary part 12b of the device body 12.

Further, as shown in Table 1, when a part of lead is replaced by calcium, strontium, or barium, the mechanical strength is improved by adding antimony oxide or niobium oxide. At this time, the effective addition amounts of antimony oxide and niobium oxide are the same as those of lead alone. If x, y, and z are not within the predetermined ranges, firing is difficult and the piezoelectric characteristics are very low.

[0030]

As described in detail above, the piezoelectric ceramic according to the present invention is different from the piezoelectric ceramic mainly composed of lead zirconate titanate zinc niobate in that at least one metal oxide of antimony oxide and niobium oxide is used. By adding a specific amount of, a piezoelectric ceramic having improved mechanical strength while maintaining transformer characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a piezoelectric device of the present invention.

FIG. 2 is a perspective view showing another example of the piezoelectric device of the present invention.

FIG. 3 is a view conceptually showing a structure of a piezoelectric device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Piezoelectric device 12 Device main body 12a Primary part 12b Secondary part 14 Output electrode 16 Input electrode 18 Input electrode 20 Contact probe

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-40965 (JP, A) JP-A-7-157315 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/49 H01L 41/187 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] (1) (Pb _1-a A _a ) (Zn _1/3 Nb _2/3 ) _× T
When represented by a general formula of i _y Zr _z O ₃ (where A is at least one metal element selected from calcium (Ca), strontium (Sr), and barium (Ba)), 0 ≦ a ≦ 0.1, x + y + z = 1, 0.05 ≦ x ≦ 0.
4. 0.05 to 3 wt% of a main component satisfying 0.1 ≦ y ≦ 0.5, 0.2 ≦ z ≦ 0.6 and manganese oxide converted to MnO ₂
And at least one of antimony oxide and niobium oxide,
In terms of sb ₂ O ₃ and Nb ₂ O ₅ Total 0.05~5wt
A piezoelectric ceramic comprising: 2. A piezoelectric device using the piezoelectric ceramic according to claim 1.