JPH07149562A - Piezoelectric ceramic composition - Google Patents

Abstract

PURPOSE:To provide a piezoelectric ceramic composition having a low dielectric constant, expressing a high electromechanical coupling factor and capable of improving heat resistance. CONSTITUTION:This composition is a complex perovskite type compound containing at least Pb, Zr, Ti, Nb, Yb and In as metal components. When a molar composition formula of these metal elements is expressed by the formula Pb1[(NbbYbcInd)eTifZr1-e-f[O3 each of a, b, c, d, e, and f satisfies 0.95<=a<=1.O5, b=1.00, 0.25<=c<=0.90, 0.10<=d<=0.75, 0.05<=e<=0.15, 0.32<=f<=0.45. A portion of Pb is preferably replaced with at least one of Ca, Sr, Ba, Pr or Nd in <=2.0mole%.

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, for example, a ceramic filter, a ceramic resonator, an ultrasonic transducer, a piezoelectric buzzer, a piezoelectric ignition unit, an ultrasonic motor, a piezoelectric fan, a piezoelectric actuator and an acceleration sensor. The present invention relates to a piezoelectric ceramic composition suitable for piezoelectric sensors such as knocking sensors and AE sensors.

[0002]

2. Description of the Related Art Conventionally, products using a piezoelectric ceramic include, for example, ceramic filters, ceramic resonators, ultrasonic applied vibrators, piezoelectric buzzers, piezoelectric ignition units, ultrasonic motors, piezoelectric fans, piezoelectric sensors, piezoelectric actuators, and the like. is there.

For elements such as ceramic filters and ceramic resonators, a porcelain composition containing PbZrO ₃ --PbTiO ₃ as a main component is used.
Metal oxides such as b ₂ O ₅ and MnO ₂ , Pb (Nb _2/3 M
g _1/3) improvement of O ₃ and _{Pb (Nb 2/3 Mn 1/3} ) piezoelectric characteristics by substituting or adding a complex perovskite oxide O _3, is achieved. As such a piezoelectric ceramic composition, a material having a large electromechanical coupling coefficient Kp and excellent piezoelectricity, such as Pb (Nb _2/3 Co _1/3 ) O
₃ -PbZrO ₃ -PbTiO ₃ system ceramic compositions are known.

On the other hand, in recent years, piezoelectric components such as ceramic filters and ceramic resonators have been required to be able to meet various conditions so that they can be mounted on the surface of a substrate or the like. When reflow soldering a component to a substrate, the component mounted on the substrate is exposed to a high temperature of about 300 ° C., so that the piezoelectric element is also required to have heat resistance.

Further, for example, a ladder type filter as shown in FIG. 1 is composed of a series resonator 1 and a parallel resonator 2. The series resonator 1 has a characteristic that the mechanical quality coefficient Qm is small and the electromechanical coupling coefficient is small. Since Kp is large and the compensation attenuation amount is large, a material having a small relative permittivity εr and excellent heat resistance is required.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the prior art, for example, the above-mentioned Pb (Nb _2/3 Co _1/3 ) O ₃ -Pb
The ZrO ₃ —PbTiO ₃ system porcelain composition has a large relative dielectric constant of about 1500 and an electromechanical coupling coefficient Kp of 50%.
Although it is large, the heat resistance is low, so that the piezoelectric characteristics before and after reflow soldering and the temperature change of the resonance frequency are large, which is a practical problem. Further, for example, a series resonator of a ladder filter is required to have a small relative permittivity εr, but there is a problem that when the relative permittivity εr of the element is reduced, the electromechanical coupling coefficient Kp sharply decreases. .

The piezoelectric ceramic composition of the present invention is intended to provide a piezoelectric ceramic composition having a small relative permittivity, a high electromechanical coupling coefficient and excellent heat resistance, and particularly a ceramic filter. It is an object of the present invention to provide a piezoelectric ceramic composition suitable for a series resonator having a small relative permittivity and an ultrasonic vibrator used for.

[0008]

The inventors of the present invention have proposed that Pb,
A composite perovskite type compound containing Zr, Ti, Nb, Yb, and In, which has a small dielectric constant, a high electromechanical coupling coefficient, and heat resistance and thermal shock resistance by controlling these to a specific composition. The inventors have found that an excellent piezoelectric ceramic composition can be obtained, and completed the present invention.

That is, the piezoelectric ceramic composition of the present invention contains at least Pb, Zr, Ti, Nb, Yb and I as metal components.
It is a composite perovskite type compound containing n, and the composition formula based on the molar ratio of these metal elements is Pb _a [(Nb _b Y
b _c In _d ) _e Ti _f Zr _{1- ef} ] O ₃
a, b, c, d, e, f are 0.95 ≦ a ≦ 1.05, b
= 1.00, 0.25 ≦ c ≦ 0.90, 0.10 ≦ d ≦
0.75, 0.05 ≦ e ≦ 0.15, 0.32 ≦ f ≦
0.40 is satisfied, and part of Pb is Ca, S
2.0 mol% of at least one of r, Ba, Pr and Nd
It is particularly desirable that the following be substituted.

Here, the reason why a, b, c, d, e and f are set in the above range will be described. The ab of Pb is set to 0.95 ≤ a ≤ 1.05 because the electromechanical coupling coefficient Kp decreases when a is less than 0.95, and a is 1.05.
This is because the electromechanical coupling coefficient Kp, the mechanical quality coefficient Qm, and the heat resistance fr _a decrease when the value is larger than the above. Pb
It is particularly desirable that the amount be 0.99 ≦ a ≦ 1.01.

Further, the Yb amount c is 0.25 ≦ c ≦ 0.
The reason for setting 90 is that the electromechanical coupling coefficient Kp decreases when c is less than 0.25 or greater than 0.90. It is particularly desirable that the Yb amount is 0.50 ≦ c ≦ 0.75.

The reason for setting the In content d to 0.10≤d≤0.75 is that the electromechanical coupling coefficient Kp decreases when d is less than 0.10 or greater than 0.75. is there.

The substitution amount e of (Nb _b Yb _c In _d ) to Zr is set to 0.05 ≦ e ≦ 0.15, because e is 0.05.
If it is less than 0.1, the electromechanical coupling coefficient Kp is not lowered or the heat resistance effect is not recognized, and if it is more than 0.15, the electromechanical coupling coefficient Kp is drastically lowered. (Nb _b Y
The substitution amount e of Zr for b _c In _d ) is 0.10 ≦ e ≦ 0.
A value of 15 is particularly desirable.

The substitution amount f of Ti by Zr is 0.32 ≦ f ≦
0.40 is used when f is less than 0.32 or 0.4
This is because if it is larger than 0, the heat resistance is deteriorated and the electromechanical coupling coefficient Kp is lowered. It is particularly desirable that the substitution amount f of Ti with Zr is 0.35 ≦ f ≦ 0.40.

Further, part of Pb is Ca, Sr, Ba, N
The reason for substituting 2.0 mol% or less of at least one of d and Pr is that by substituting, the temperature characteristics of the resonance frequency can be improved and the electromechanical coupling coefficient Kp can be improved. . This substitution amount is 2.0
The reason why the content is limited to mol% or less is that the electromechanical coupling coefficient Kp tends to decrease when the content is more than 2.0 mol%. P
The amount of substitution of Ca, Sr, Ba, Nd, and Pr for b is 0.
It is particularly desirable that the amount is 5 mol% or more and 2.0 mol% or less.

The piezoelectric ceramic of the present invention may be made of, for example, PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ and Yb ₂ as raw materials.
O ₃ , In ₂ O ₃ , CaCO ₃ , SrCO ₃ and Ba
A predetermined amount of each raw material powder of CO ₃ , Nb ₂ O ₃ and Pr ₆ O ₁₁ was weighed and wet-mixed with a ball mill or the like for 10 to 24 hours, and then the mixture was dehydrated and dried, then 500-100
It is calcined at 0 ° C. for 1 to 3 hours, and the calcined product is ground again with a ball mill or the like.

After that, an organic binder is mixed with the pulverized product, and after granulation, the product is molded at a predetermined pressure to prepare a molded product, which is 0.5 to 0.5 at 1200 to 1350 ° C. in the atmosphere.
It is obtained by firing for 4 hours.

[0018]

In the piezoelectric ceramic composition of the present invention, PbZrO ₃
Part of Zr and Ti of the PbTiO ₃ -based porcelain composition is N
By substituting with b, Yb, and In, the relative dielectric constant is 30.
When the electromechanical coupling coefficient Kp is 0 to 1000, the electromechanical coupling coefficient Kp exhibits high characteristics of 30% or more, has excellent heat resistance even at a temperature cycle of about 250 ° C., and the resonance frequency hardly changes. Shows excellent stability. For this reason,
When the element is mounted on the substrate by the reflow soldering, there is no change in the characteristics, and the non-defective rate at the time of manufacturing can be increased.

[0019]

The present invention will be described in the following examples. As raw material powder, PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ ,
Yb ₂ O ₃ , In ₂ O ₃ , CaCO ₃ , SrCO ₃ , B
Each raw material powder of aCO ₃ , Nb ₂ O ₃ and Pr ₆ O ₁₁ was weighed in a predetermined amount as shown in Table 1 and Table 2, wet-mixed in a ball mill for 12 hours, and then the mixture was dehydrated and dried, It is calcined at 950 ° C. for 3 hours, and the calcined product is pulverized with a ball mill again.

Then, an organic binder (P
VA) was mixed and granulated. 1.5 t / of the obtained powder
A disk having a diameter of 23 mm and a thickness of 2 mm was press-molded with a pressure of cm ² . Furthermore, these molded bodies are
The container was sealed in a container made of O or the like and baked in the atmosphere at 1300 ° C. for 2 hours.

The obtained sintered body is polished to have a thickness of 0.5 mm.
Disk was formed. Electrodes were formed by baking Ag paste on both main surfaces of the disk, and a DC voltage of 3 kv / mm was applied for 30 minutes in silicon oil at 80 ° C. for polarization, and then an electromechanical coupling coefficient Kp, The heat resistance, relative permittivity εr, and mechanical quality factor Qm were evaluated.

The electromechanical coupling coefficient Kp, the relative permittivity εr, and the mechanical quality coefficient Qm were calculated by an impedance analyzer. The heat resistance is Δfr _a = (from the values of the resonance frequency fr ₁ before the test and the resonance frequency fr ₂ after the test when the test is conducted by passing the test piece through a reflow furnace having a peak of 250 ° C. three times in succession. The change rate Δfr _a calculated using the formula fr ₂ −fr ₁ ) / fr ₁ × 100 was evaluated. The results are shown in Tables 1 and 2.

[0023]

[Table 1]

[0024]

[Table 2]

From these tables, the porcelain composition of the present invention is
Relative permittivity εr is 300 to 1000, electromechanical coupling coefficient K
It can be seen that _P is as large as 30% or more, and the temperature change Δfr _a of the resonance frequency in the heat resistance test is as small as 0.20% or less.

[0026]

As described in detail above, according to the present invention, P
By substituting a part of Zr and Ti of the bZrO ₃ —PbTiO ₃ based porcelain composition with Nb, Yb, In,
It is possible to obtain a piezoelectric ceramic composition having a small relative permittivity, a high electromechanical coupling coefficient, improved heat resistance, and being effectively used as an element such as a piezoelectric component for surface mounting.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a ladder filter.

[Explanation of symbols]

 1 series resonator 2 parallel resonator

Claims (2)

[Claims] 1. A metal component containing at least Pb, Zr, and T.
i, Nb, Yb, a composite perovskite compound including In, the composition formula by molar ratio of the metal elements Pb _{a [(Nb b Yb c In d)} e Ti f Zr 1-ef ]
When expressed as O ₃ , a, b, c, d, e, f are 0.95 ≦ a ≦ 1.05 b = 1.00 0.25 ≦ c ≦ 0.90 0.10 ≦ d ≦ 0. 75 A piezoelectric ceramic composition characterized by satisfying 0.05 ≦ e ≦ 0.15 0.32 ≦ f ≦ 0.40. 2. Part of Pb is Ca, Sr, Ba, Pr, N
2. The piezoelectric ceramic composition according to claim 1, wherein at least one of d is substituted by 2.0 mol% or less.