JPH0745882A - Piezoelectric element - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric element whose baking temperature can be lowered, whose crystal particle size can be made dense and in which the attenuation factor of elastic waves is reduced, by a method wherein a Ti-Zr-Pb- oxide-based piezoelectric plate which contains zinc and niobium is used as a main component and a specific oxide is added as a subcomponent. CONSTITUTION:A compound expressed by the formula is used as a main component for the piezoelectric plate of a plezoelectric element::, values for (x), (y) and (z) are set at 0.1<=(x)<=0.5, 0.12<=(y)<=0.75 and 0.125<=(z)<=0.865 and (x)+(y)+(z)=1. Pb(M1/2W1/2)O3 is used as a subcomponent, where 0.5 to 10.0wt. % of M which is represented by at least one kind out of Co, Ni, Cu and Zn is added and this mixture is baked temporarily. Then, the mixture is crushed and dried, a bonding agent is added, and this mixture is granulated, pressurized and formed into a disk. Then, the disk is baked again, a silver electrode is formed. Then, the piezoelectric element is obtained. Thereby, its baking temperature can be lowered, its crystal particle size is made dense, its attenuation factor of elastic waves Is reduced, and its piezoelectric characteristic such as an electromechanical coupling coefficient or the like can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric element used for an oscillator or a surface wave element, for example.

[0002]

2. Description of the Related Art Conventionally, as a piezoelectric plate of a piezoelectric element, barium titanate porcelain, lead zirconate titanate titanate porcelain, magnesium niobate titanate zirconate titanate porcelain, and zinc niobate titanate lead zirconate titanate porcelain were used. . And various improvements were made according to the purpose of use.

[0003]

In the above conventional structure, the firing temperature of the piezoelectric plate is as high as 1200 to 1300 ° C. Even if the fine particle raw material is used to lower the firing temperature,
The temperature could not be lowered to 1100 ° C or lower. Therefore, evaporation of lead oxide during firing was remarkable, and densification was hindered.

As a result, there is a problem that the attenuation rate of the elastic wave of the piezoelectric element increases.

The present invention solves the above problems and provides a piezoelectric element which can be fired at a low temperature and has improved electromechanical coupling coefficient and mechanical quality coefficient.

[0006]

In order to achieve this object, the piezoelectric element of the present invention comprises a piezoelectric body as a main component represented by (Chemical Formula 2) and Pb (Co _1/2 W _1/2 as a sub-component. ) O ₃ , Pb
(Ni _1/2 W _1/2 ) O ₃ , Pb (Cu _1/2 W _1/2 ) O ₃ , Pb
At least one of (Zn _1/2 W _1/2 ) O ₃ is 0.5
It is formed by adding -10.0% by weight.

[0007]

[Chemical 2]

[0008]

According to the above structure, Pb (Co _1/2 W _1/2 )
O ₃ , Pb (Ni _1/2 W _1/2 ) O ₃ , Pb (Cu _1/2 W _1/2 )
By adding 0.5 to 10.0% by weight of at least one of O ₃ and Pb (Zn _1/2 W _1/2 ) O ₃ , the sintering temperature can be lowered and at the same time crystal grain growth can be achieved. Since it is suppressed, it can be densified. As a result, the attenuation factor of elastic waves is reduced, and a piezoelectric element having an improved electromechanical coupling coefficient and mechanical quality coefficient can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, PbO, TiO ₂ , ZrO ₂ , Zn
O, Nb ₂ O ₅ , CoO, NiO, CuO and WO ₃ were accurately weighed so as to have the compositions shown in (Table 1), (Table 2) and (Table 3), and mixed well by a ball mill.

[0011]

[Table 1]

[0012]

[Table 2]

[0013]

[Table 3]

The following mixture was calcined at a temperature of 850 ° C., further crushed by a ball mill, dried, and an aqueous polyvinyl alcohol solution was added as a binder to granulate. Then, it was pressure-molded into a disk shape having a diameter of 20 mm and a thickness of 1 mm at a pressure of 1 ton / cm ² , and then fired at a temperature of 1000 to 1250 ° C. for 1 hour in a closed furnace to obtain the piezoelectric plate 1 of FIG. This piezoelectric plate 1 is lapped to a thickness of 0.5 mm, and silver electrodes 2a, 2 are provided on both sides.
b is baked in silicon oil at 100 ° C for 3KV /
A direct current electric field of mm was applied for 30 minutes for polarization treatment. In this way, 5 samples were prepared for each sample number.

The density, crystal grain size, dielectric constant ε _T / ε _O ,
The electromechanical coupling coefficient Kp and the mechanical quality coefficient Qm were measured, the average value was calculated for each sample No, and the firing temperatures are shown in (Table 4), (Table 5) and (Table 6).

[0016]

[Table 4]

[0017]

[Table 5]

[0018]

[Table 6]

In Tables 1 to 6, the sample No. 28-3
When the subcomponents are less than 0.5% by weight, such as 2,38,39, the sintering temperature must be 1170 ° C or higher. In addition, sample No. 33 to 37, the auxiliary component is more than 10.0% by weight, the sample No. X, like 40, 41
A composition of <0.01, x> 0.60 does not sinter. Sample No. 42-45, y <0.120, y
With a composition of> 0.75, z> 0.125, and z> 0.865, Kp is 10% or less, and the piezoelectric property is significantly lowered.

[0020]

As described above, in the piezoelectric element of the present invention, the piezoelectric plate is made of the compound represented by (Chemical Formula 1) and Pb (Co _1/2 W _1/2 ) O.
₃ , Pb (Ni _1/2 W _1/2 ) O ₃ , Pb (Cu _1/2 W _1/2 ) O
_3, the Pb (Zn _1/2 W _1/2) to at least one of O ₃ is added 0.5 to 10.0 wt%, it is possible to become simultaneously densifying possible low-temperature firing. As a result, the attenuation factor of the elastic wave is reduced, and a piezoelectric element having improved piezoelectric characteristics such as an electromechanical coupling coefficient and a mechanical quality coefficient can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a piezoelectric element according to an embodiment of the present invention.

[Explanation of symbols]

 1 Piezoelectric plate 2a, 2b electrode

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H03H 9/25 C 7259-5J

Claims (1)

[Claims] 1. A piezoelectric plate and a pair of electrodes provided on the surface of the piezoelectric plate, wherein the piezoelectric plate contains Pb (Co _1/2 W _{1 / 2} ) O ₃ , Pb
(Ni _1/2 W _1/2 ) O ₃ , Pb (Cu _1/2 W _1/2 ) O ₃ , Pb
At least one of (Zn _1/2 W _1/2 ) O ₃ is 0.5
A piezoelectric element to which 10.0 wt% is added. [Chemical 1]