JPH0692729A - Piezoelectric porcelain composition - Google Patents

Abstract

PURPOSE:To obtain a material for a laminated piezoelectric element capable of sintering at a low temp. by limiting the principal components in a piezoelectric porcelain compsn. represented by a specified general formula to a prescribed range in a three-component compsn. diagram. CONSTITUTION:This piezoelectric porcelain compsn. has a compsn. represented by the general formula (where 0.001<=s<=0.2 and x+y+z=1) and the principal components (x, y, z) in this compsn. are limited to the range defined by a line connecting points A (x=0.74, y=0.25, z=0.01), B (x=0.4, y=0.59, z=0.01), C (x=0.4, y=0.25, z=0.35) and D (x=0.06, y=0.59, z=0.35) in the three-component compsn. diagram. In this compsn., Ca, Ba or Sr may be substd. for part of Pb by 0.001-0.1. This piezoelectric porcelain compsn. is excellent in piezoelectric characteristics and is sintered at such a low temp. as 1,100 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic composition containing lead zirconate titanate as a main component, and in particular, it can be sintered at a low optimum sintering temperature of about 1100 ° C. and has excellent piezoelectric characteristics. And a piezoelectric ceramic composition.

[0002]

2. Description of the Related Art Conventional piezoelectric ceramic compositions having a composition containing lead zirconate titanate as a main component have a large piezoelectric constant, and are therefore widely used as materials for actuators including piezoelectric vibrators. There is. However, with this type of material, it is difficult to obtain a dense sintered body due to evaporation of lead oxide during firing, and the morphotopic phase boundary (MP
In the vicinity of B), since the piezoelectricity depends on the composition of titanium and zirconium, it is difficult to guarantee the reproducibility and uniformity of the characteristics. To remedy these drawbacks,
For example, means for substituting Pb with an appropriate amount of Ca, Sr, Mg, Ba, or the like, or La, Nd, Nb, Ta, Sb, B
There is a means of adding oxides such as i, Th, and W. The former has the advantage that the permittivity can be increased without lowering the piezoelectric characteristics, and the latter has the advantage that polarization is facilitated, the piezoelectric constant is increased, and the change over time is reduced. On the other hand, in parallel with the improvement of lead zirconate titanate, a large number of compound perovskite type compounds having a plurality of ions having different valences at the A or B positions were discovered as ABO ₃ type ferroelectrics. Since then, research and development on the composition of the three components with this composite perovskite type compound have been vigorously pursued. Examples of the ternary piezoelectric ceramic composition include PbTiO ₃
There is a composition of -PbZrO ₃ -Pb (Ni _1/3 Nb _2/3 ) O ₃ . Wherein the piezoelectric ceramic composition of such a three-component system, for example, Pb (Zr, Ti) of said component as compared to the O _3, less evaporation of lead oxide, the calcination is easy, Morpho topic The phase boundary (MPB) extends from a point to a line, resulting in a material with properties that make it more versatile. The PbTiO ₃
The -PbZrO ₃ -Pb (Ni _1/3 Nb _2/3 ) O ₃ -based piezoelectric ceramic composition has an extremely large piezoelectric strain constant (d constant) and thus is suitable for a piezoelectric ceramic for an actuator element.

[0003]

However, the above-mentioned Pb
The sintering temperature of the TiO ₃ -PbZrO ₃ -Pb (Ni _1/3 Nb _2/3 ) O ₃ -based piezoelectric ceramic composition is as high as 1200 to 1300 ° C. Therefore, when a laminated piezoelectric element is produced with this piezoelectric ceramic composition, platinum or palladium that can withstand this sintering temperature must be used as an internal electrode, which is a problem of high manufacturing cost. . If the sintering temperature can be lowered, an inexpensive silver-palladium alloy or the like can be used. When using a silver-palladium alloy as the internal electrode, if the cost of palladium is high and the content of palladium is high, palladium undergoes a redox reaction during sintering,
Since it causes cracks and peeling in the laminated piezoelectric element,
The proportion of palladium is required to be 30% or less. To reduce the ratio of palladium to 30% or less, Ag-Pd
From the phase diagram, the sintering temperature is 1150 ° C or less, preferably 1
It is necessary to set the temperature to 120 ° C or lower. Therefore, PbTi
O ₃ -PbZrO ₃ -Pb (Ni _1/3 Nb _2/3 ) O ₃ -based piezoelectric ceramic composition is used to make a laminated piezoelectric element using silver / palladium for internal electrodes. Or a complicated operation such as HIP processing is required.

The present invention solves the problems existing in the above-mentioned prior art, and is a piezoelectric material suitable for a user material, especially a laminated piezoelectric element material, which can easily be sintered at a low temperature and has a large piezoelectric property. The purpose is to provide a porcelain composition.

[0005]

In order to solve the above problems, in the present invention, the general formula (1-s) {xPb (Ni _1/3 Nb _2/3 )
O ₃ -yPbTiO ₃ -zPbZrO ₃ } -sPb (Co _1/2 W _1/2 ) O ₃ (however, x + y + z =
In the piezoelectric ceramic composition consisting of 1), the compounding ratio x, y, z is
In this three-component composition diagram, the following composition point A: (x = 0.74, y =
0.25, z = 0.01) B: (x = 0.40, y = 0.59, z = 0.01) C: (x = 0.40, y =
0.25, z = 0.35) D: (x = 0.06, y = 0.59, z = 0.35) on the line connecting them and in the composition range surrounded by this line, and s is 0.0
In the range of 01 ≦ s ≦ 0.2, a part of Pb in the main component is replaced with at least one of Ca, Ba and Sr of 0.001 to 0.1, which is a technical means.

[0006]

[Function] The reason why the main component composition range is limited to the above range is as follows.
This is because the composition electromechanical coupling coefficient Kp or the relative dielectric constant ε T ₃₃ is remarkably lowered in the composition outside the above range. The amount of strain generated when a laminated piezoelectric element is used is proportional to the piezoelectric strain constant, which is one of the material characteristics of the piezoelectric ceramic composition. This piezoelectric strain constant (d31) is calculated by equation 1.

[0007]

[Number 1] d31 = _{[(1-σ) S 11 E} · εT 33 · ε 0/2 ] _{^{1/2 · K P (σ}} : Poisson's ratio, S ₁₁ E: elastic compliance,
epsilon _0: Of the dielectric constant of vacuum) Number 1 sigma, S ¹¹ E is a piezoelectric material PZT-based, most ^{σ = 0.25~0.35, S 11 E =} 11~16 × 10
^Since it is in the range of ^-12 m ² / N, d 31 is almost proportional to the product of Kp and the square root of ε T ₃₃ . Therefore, the piezoelectric strain constant (d constant) is remarkably reduced outside the above-mentioned limited range. Pb (Co _1/2 W _1/2 ) O
_{When 3} is contained in 0.001 ≦ s ≦ 0.2, Kp and εT ₃₃
It is possible to significantly reduce the sintering temperature without lowering the temperature. When s <0.001, the sintering temperature is 112
It cannot be 0 ° C or lower. When S> 0.2, the decrease in Kp is remarkable. Substitution of part of Pb in the main component with at least one of Ca, Ba, and Sr increases ε T ₃₃ . The substitution amount is 0.
If it is less than 001, the effect of substitution is insufficient, and if it exceeds 0.100, the Kp is remarkably lowered, and the sintering temperature is 1120.
Exceeds ℃.

[0008]

EXAMPLES The effects of the present invention will be specifically described below with reference to examples.

Lead oxide (PbO), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), nickel oxide (NiO), niobium oxide (Nb ₂ O ₅ ), tungsten oxide (WO ₃ ), cobalt oxide (CoO) A raw material of strontium carbonate (SrCO ₃ ) was weighed so as to have the composition shown in Table 1 and mixed in a ball mill for 2 hours. The obtained mixture was tentatively molded, calcined in air at 850 ° C. for 2 hours, and further pulverized by a ball mill for 2 hours. After granulating this, a molded product having a diameter of 20 mm and a length of 15 mm was prepared by press molding. Sintering was performed for 2 hours in oxygen in a state where the molded body was sealed in a container made of alumina or magnesia. Cutting the obtained sintered body,
By polishing, a shape having a diameter of 16 mm and a thickness of 0.8 mm was formed, electrodes made of Cr-Au were formed on both end faces, and a polarization treatment was performed by applying a DC voltage of 3 kV / mm in silicon oil.

Table 1 shows the characteristics obtained with each composition. composition
Nos. 1, 3, 5, and 7 are A, B, C, and D in FIG. 1, respectively.
Corresponding to the composition of. The main component, PbTiO ₃ -PbZrO ₃ -Pb (Ni
Within the composition range in which _1/3 Nb _2/3 ) O ₃ is surrounded by A, B, C and D, Kp and ε T ₃₃ are large and a large strain amount can be obtained in the case of a laminated piezoelectric element. An appropriate amount of Pb (C
The composition with addition of o _1/2 W _1/2 ) O ₃ is 2, 4, 6, and 8, respectively, but the optimum sintering temperature decreases by about 100 ° C,
It can be seen that sintering can be performed at a temperature of ℃ or less. Composition No. 10 to 1
5 indicates that when the amount of Pb (Co _1/2 W _1/2 ) O ₃ added is within the limited composition range,
Both p and εT ₃₃ are sufficiently large, but Pb (Co _1/2 W _1/2 ) O ₃
When the amount added exceeds 0.20, the Kp is significantly lowered.

From the results of Composition Nos. 17 to 20, εT ₃₃ is further increased by substituting a part of Pb with Sr.

As is clear from the above results, the piezoelectric ceramic composition of the present invention has an optimum sintering temperature of 1120 ° C. or lower and a large Kp and εT ₃₃ . Note that instead of Sr, Ca,
When Ba was used, the same results as in Tables 1 and 2 were obtained.

[Table 1]

[Table 2]

[0013]

EFFECTS OF THE INVENTION Since the piezoelectric ceramic composition of the present invention has a sintering temperature of 1120 ° C. or lower, when used as a laminated piezoelectric element, inexpensive silver / palladium electrodes can be used, and the piezoelectric Because of its excellent characteristics, it is extremely useful as a piezoelectric ceramic composition for laminated piezoelectric elements.

[Brief description of drawings]

FIG. 1 is a main component (Pb (Ni _1/3 Nb _2/3 ) O ₃ -PbT in the present invention.
The composition range of iO ₃ -PbZrO ₃ ) is shown.

Claims (2)

[Claims] 1. The general formula (1-s) {xPb (Ni _1/3 Nb _2/3 ) O ₃ -yPbTi
In a piezoelectric ceramic composition consisting of O ₃ -zPbZrO ₃ } -sPb (Co _1/2 W _1/2 ) O ₃ (however, x + y + z = 1), the compounding ratios x, y, z are the three components. In the composition chart, the following composition points A: (x = 0.74, y = 0.25, z =
0.01) B: (x = 0.40, y = 0.59, z = 0.01) C: (x = 0.40, y = 0.25, z =
0.35) D: (x = 0.06, y = 0.59, z = 0.35) is on the line connecting the lines and in the composition range surrounded by this line, and s is 0.001 ≦ s ≦
A piezoelectric ceramic composition characterized by being in the range of 0.2. 2. A part of Pb is 0.001-0.1 Ca, Ba,
The piezoelectric ceramic composition according to claim 1, wherein at least one of Sr is substituted.