JPH07187775A - Piezoelectric porcelain composition - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric porcelain composition exhibiting a high electromechanical coupling factor, a high mechanical quality factor and a low dielectric constant, and capable of improving heat resistance. CONSTITUTION:This piezoelectric porcelain composition comprises a composite perovskite type compound containing at least Pb, Zr, Ti, Nb, Mn, and Fe as metal components and satisfying inequalities: 0.95<=a<=1.05, 0.05<=b<=0.67, 0.10<=c<=0.35, 0.05<=d<=0.35, 0.05<=e<=0.12, 0.20<=f<=0.35, b+c+d:1.00, when a composition formula showing the molar ratio of the metal elements is represented by Pb1[(NbbMncFed)eTifZr1-3-f]O3.

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 sensor, a piezoelectric actuator. Etc., especially surface acoustic waves (Surface Ac
The present invention relates to a piezoelectric porcelain composition which is most suitable for an acoustic wave filter.

[0002]

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

Here, as elements such as ceramic filters and ceramic resonators, PbZrO ₃ -PbTi is used.
A porcelain composition containing O ₃ as a main component has been used, whereby a metal oxide such as Nb ₂ O ₅ or MnO ₂ , Pb (N
b _2/3 Mg _1/3 ) O ₃ and Pb (Nb _2/3 Co _1/3 ) O ₃
The piezoelectric characteristics have been improved by adding or substituting a composite perovskite oxide such as.

A piezoelectric ceramic composition having a large mechanical quality factor Qm, a large electromechanical coupling factor Kp, a small dielectric constant, and a wide optimum firing temperature is Pb (Nb).
_A piezoelectric magnetic composition comprising a ternary solid solution of _2/3 Mn _1/3 ) O ₃ -PbZrO ₃ -PbTiO ₃ is disclosed (see Japanese Patent Publication No. 46-16632). Further, as a material electromechanical coupling factor Kp is excellent in large piezoelectric property, for _{example, Pb (Mn 2/3 W 1/} 3) O 3 -PbZrO 3 -P
A bTiO ₃ -based porcelain composition is known.

On the other hand, in recent years, SA of several tens of megahertz band
As a W filter material, a material utilizing surface acoustic waves of piezoelectric ceramics is used. As such a piezoelectric ceramic, Pb (Nb _2/3) containing Pr ₆ O ₁₁ is used.
Mn _1/3 ) O ₃ —PbZrO ₃ —PbTiO ₃ is known (Japanese Patent Publication No. 56-50434). As a piezoelectric ceramic of a SAW filter material, a material having a low dielectric constant, a high electromechanical coupling coefficient, and a small temperature change rate of characteristics is desired because it is used in a relatively high frequency range. Therefore, the composition in the vicinity of the composition phase boundary (MPB) of the conventional PbZrO ₃ —PbTiO ₃ composition system is not used, but the material in the composition region in which rhombohedral crystals are the main crystal phase is used.

In addition, piezoelectric components for SAW filters are also required to be able to meet various conditions so that they can be mounted on the surface of a substrate or the like. In such piezoelectric components, the components are reflow soldered to the substrate. At this time, since the component mounted on the substrate is exposed to a high temperature of about 300 ° C., the piezoelectric element in which the component is incorporated is also required to have heat resistance.

[0007]

However, the conventional Pb (Nb _2/3 Mn _1/3 ) O ₃ -Pb described above, for example, is used.
The ZrO ₃ —PbTiO ₃ based porcelain composition has low heat resistance and has large changes in piezoelectric characteristics and resonance frequency before and after reflow soldering, which has been a practical problem.

The piezoelectric ceramic composition of the present invention is a material having a large electromechanical coupling coefficient Kp and a mechanical quality coefficient Qm, a small relative dielectric constant suitable for high frequency applications, and excellent heat resistance. The purpose is to provide.

[0009]

The inventors of the present invention have proposed that Pb,
A complex perovskite type compound containing Zr, Ti, Nb, Mn, and Fe, which has a constant composition, has a high electromechanical coupling coefficient and a high mechanical quality coefficient, a small relative dielectric constant, and a high heat resistance. The inventors have found that a piezoelectric ceramic composition having excellent properties 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, Mn and F as metal components.
It is a composite perovskite type compound containing e, and the composition formula based on the molar ratio of these metal elements is Pb _a [(Nb _b M
n _c Fe _d ) _e Ti _f Zr _{1- ef} ] O ₃
a, b, c, d, e, f are 0.95 ≦ a ≦ 1.05,
0.50 ≦ b ≦ 0.67, 0.10 ≦ c ≦ 0.35,
0.05 ≦ d ≦ 0.35, 0.04 ≦ e ≦ 0.12,
It satisfies 0.20 ≦ f ≦ 0.35 and b + c + d = 1.00.

Here, the reason why a, b, c, d, e and f are set in the above range will be described. The Pb amount a was set to 0.95 ≦ a ≦ 1.05 because the electromechanical coupling coefficient Kp decreases when a is less than 0.95 or greater than 1.05.

Further, the Nb amount b is 0.50 ≦ b ≦ 0.6
The reason for setting 7 is that the electromechanical coupling coefficient Kp decreases when b is less than 0.50, and the heat resistance decreases when b is greater than 0.67.

Further, the Mn content c is 0.10≤c≤0.
The reason for setting 35 is that when c is less than 0.10, the heat resistance is lowered, and when c is more than 0.35, the electromechanical coupling coefficient Kp is lowered and the heat resistance is lowered.

The d content of Fe is set to 0.05≤d≤0.35 because the Curie temperature is lowered when d is less than 0.05 and the heat resistance is lowered, and when d is greater than 0.35, the mechanical strength is reduced. This is because the quality factor Qm decreases. (Nb _b Mn _c Fe
_The amount e of substitution of _d ) with Zr is set to 0.04 ≦ e ≦ 0.12, when e is less than 0.04, the effect of heat resistance is not recognized and the electromechanical coupling coefficient Kp is low. This is because if it is larger than 12, the electromechanical coupling coefficient Kp drops sharply.

The substitution amount f of Ti with Zr is 0.20 ≦ f ≦
The reason for setting 0.35 is that when f is less than 0.20, the electromechanical coupling constant Kp is lowered and heat resistance is lowered, and when f is greater than 0.35, the relative dielectric constant becomes too high. . In the present invention, part of Pb may be replaced with Ba, Ca, Sr, Pr and Nd in order to improve the temperature coefficient of the resonance frequency.

In the piezoelectric ceramic of the present invention, for example, PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ and M are used as raw materials.
A predetermined amount of each raw material powder of n ₂ O ₃ and Fe ₂ O ₃ 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, and then 500-1000.
It is calcined at 1 ° C for 1 to 3 hours, and the calcined product is pulverized again by a ball mill or the like. Then, an organic binder is mixed with this pulverized product, and after granulation, it is molded at a predetermined pressure to prepare a molded body, and these are molded in the atmosphere at 1200 to 1350 ° C. for 0.5 to
It is obtained by firing for 4 hours.

[0017]

In the piezoelectric ceramic composition of the present invention, PbZrO ₃
By substituting Nb, Mn, and Fe for part of Zr and Ti of the PbTiO ₃ -based porcelain composition, a high electromechanical coupling coefficient, a high mechanical quality coefficient Qm, and a low dielectric constant are shown, and heat resistance is improved. It becomes possible to do.

[0018]

The present invention will be described in the following examples. As raw material powder, PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ ,
A predetermined amount of each raw material powder of MnO ₃ and Fe ₂ O ₃ was weighed as shown in Table 1, and wet mixed in a ball mill for 12 hours,
Then, after dehydrating and drying the mixture, the mixture was dried at 950 ° C. for 3 hours.
It is calcined for a period of time, and the calcined product is pulverized again with a ball mill.

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 sides of this disk, and after applying a DC voltage of 3 kV / mm for 30 minutes in silicon oil at 80 ° C for polarization treatment, the electromechanical coupling coefficient and heat resistance were improved. evaluated. Further, the relative permittivity εr was calculated and calculated from the capacitance obtained by the impedance meter. The electromechanical coupling coefficient Kp was calculated from the values of the resonance frequency and the antiresonance frequency measured with an impedance meter. The heat resistance was calculated from the values of the electromechanical coupling coefficient Kp ₁ before the test and the value of Kp ₂ after the test when the test was conducted through a reflow furnace having a peak of 260 ° C. three times in succession. _2- Kp ₁ ) / Kp ₁ ×
The rate of change ΔKp calculated using the formula of 100 was evaluated.
The mechanical quality factor Qm was calculated from the resonance frequency, anti-resonance frequency, resonance resistance, and capacitance measured with an impedance meter. The results are shown in Table 1.

[0021]

[Table 1]

From Table 1, the porcelain composition of the present invention has a large electromechanical coupling coefficient Kp of 15% or more, a high mechanical quality factor Qm of 1300 or more, and a relative dielectric constant of 350.
Low as below, and the change of ΔKp by heat resistance test is ± 1
It can be seen that the heat resistance is excellent because it is as small as 0.1% or less.

[0023]

According to the present invention, PbZrO ₃ -PbT
Part of Zr and Ti of the io ₃ -based porcelain composition is Nb, M
By substituting with n and Fe, a high electromechanical coupling coefficient, a mechanical quality coefficient, and a low dielectric constant are exhibited, heat resistance is improved, and a piezoelectric ceramic composition most suitable as a SAW filter element for surface mounting can be obtained. it can.

Claims (1)

[Claims] 1. A metal component containing at least Pb, Zr, and T.
i, Nb, Mn, a composite perovskite compound including Fe, the composition formula by molar ratio of the metal elements Pb _{a [(Nb b Mn c Fe d)} e Ti f Zr 1-ef ]
When expressed as O ₃ , a, b, c, d, e, f are 0.95 ≦ a ≦ 1.05 0.50 ≦ b ≦ 0.67 0.10 ≦ c ≦ 0.35 0.05 ≦ A piezoelectric ceramic composition characterized by satisfying d ≦ 0.35 0.04 ≦ e ≦ 0.12 0.20 ≦ f ≦ 0.35 b + c + d = 1.00.