JPH06196769A - Piezoelectric material - Google Patents

Abstract

PURPOSE:To simultaneously heighten stability to an electric machine bond coefficient, a mechanical quality coefficient and a temperature change of a piezoelectric porcelain by using a piezoelectric material to be shown by a specific chemical formula. CONSTITUTION:A piezoelectric porcelain material is to be shown by the formula. In the formula, X, Y, Z is within the following formula and the total is 1. X is 0.35<=X<=0.45, Y is 0.45<=Y<=0.55, Z is 0.08<=Z<=0.15. Further, in the piezoelectric porcelain material, a part of a Pb atom is replaced by at least one kind of atoms selected from a group consisting of Ba, Ca and Sr. In this way, when a part of a Pb atom is replaced, a dielectric constant can be heightened without damaging an electric machine bond coefficient and a mechanical quality coefficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to porcelain materials, especially piezoelectric ceramic materials.

[0002]

2. Description of the Related Art With the increase in the capacity of communication information such as video signals and audio signals and the diversification of communication terminals such as car phones and mobile communication, a highly sensitive and low loss filter with high reliability is required. ing. As a result, the development of piezoelectric ceramic materials suitable for such filters is desired.

Suitable piezoelectric ceramic materials for the above filters are lead (Pb), zirconium (Zr) and titanium (T).
A so-called PZT-based piezoelectric ceramic material composed of the complex oxide i) is known. As a PZT-based piezoelectric ceramic material of this type, Japanese Patent Publication No. 54-34920 discloses a mechanical quality factor (Q) obtained by adding tin (Sn) and niobium (Nb) oxides.
The higher m) is shown. In addition, Japanese Patent Publication No.
No. 36756 includes antimony (Sb) and tin (Sn).
A PZT-based piezoelectric ceramic material having a dielectric constant (εr) and an electromechanical coupling coefficient (Kp) increased by the addition of the oxide (1) is shown.

[0004]

The conventional piezoelectric ceramic material cannot form a piezoelectric ceramic having both a good electromechanical coupling coefficient and a good mechanical quality coefficient, and is stable with respect to temperature changes. poor. Therefore, when a filter for a communication device mounted on a vehicle, which is subject to drastic environmental changes, is formed of a conventional piezoelectric ceramic material, the transmission / reception frequency fluctuates due to temperature changes in the vehicle and stable transmission / reception is often difficult.

An object of the present invention is to simultaneously increase the electromechanical coupling coefficient, the mechanical quality coefficient and the stability against temperature change of the piezoelectric ceramic.

[0006]

The piezoelectric ceramic material of the present invention is represented by the following general formula.

[0007]

[Chemical 2]

In the general formula, X, Y and Z are in the following ranges and have a total of 1.

[0009]

[Equation 2]

In this piezoelectric ceramic material, for example, 3 to 15 atomic% of Pb is replaced with at least one atom selected from the group consisting of Ba, Ca and Sr. *** The piezoelectric ceramic material of the present invention is a solid solution of perovskite type crystals represented by the following general formula.

[0011]

[Chemical 3]

This piezoelectric ceramic material contains Pb, Zr and T
The interstitial solid solution containing atoms of Nb, Mn, and W in the space lattice of i, and the intrinsic positions of Pb, Zr, and Ti in which the atoms of Nb, Mn, and W form the spatial lattice are irregular. Both substitutional solid solutions substituting for In the above general formula, X, Y and Z are in the following ranges and the total is 1.

[0013]

[Equation 3]

When X is less than 0.35 or Y is 0.5
When it exceeds 5, the electromechanical coupling coefficient becomes small. X
When Y exceeds 0.45 or Y is less than 0.45, the variation (drift) of the resonance frequency increases when the temperature changes. When Z is less than 0.08, the sinterability decreases, and the mechanical quality factor of the piezoelectric ceramic decreases. Z is 0.
If it exceeds 15, the Curie point (Tc) becomes low.

In the piezoelectric ceramic material of the present invention, a part of Pb atoms in the above general formula may be substituted with at least one atom selected from the group consisting of Ba, Ca and Sr. By substituting a part of Pb atoms in this way, the dielectric constant can be increased without impairing the electromechanical coupling coefficient and the mechanical quality coefficient. The substituted atoms of Ba, Ca and Sr form a spatial lattice, that is, an A site in the perovskite type crystal structure. The Pb atom substitution amount is preferably set to 3 to 15% of the total Pb atoms. When the substitution amount is less than 3 atomic%, improvement in dielectric constant cannot be expected. On the contrary, if it exceeds 15 atomic%, the heat resistance of the piezoelectric ceramic material deteriorates. A more preferable range of the substitution amount of Pb atoms is 3 to 15 atom%.

Next, a method of manufacturing a piezoelectric ceramic material of the present invention will be described.
explain about. The piezoelectric ceramic material of the present invention has a special method.
Can be manufactured according to a well-known method.
Specifically, PbO, TiO₂, ZrO₂, Nb
₂O_Five, MnO ₂And WO₃Metallic acid of constituent metal elements such as
Compound is used as the raw material powder, and each of these raw material powders is described above.
Weigh and mix so as to be in the range of X, Y and Z.

As the raw material powder, it is possible to use carbonates and oxalates of the constituent metal elements instead of the metal oxides. It is also possible to use a composite oxide powder such as PbTiO ₃ or PbZrO ₃ which is calcined by combining metal oxides. Next, the mixed material powder is molded into a desired shape by a method such as press molding or a doctor blade method, and is fired. Firing is 1200-1340 ° C
2 to 6 hours in the oxidizing atmosphere. Thereby, the piezoelectric ceramic material of the present invention is obtained.

The obtained piezoelectric ceramic material has a relative density of 95.
It is desirable that it is a high-density body of at least%. Relative density is 9
If it is less than 5%, it becomes difficult to suppress the waveform defect when the filter is formed of the material. Such a piezoelectric ceramic material having a high relative density is obtained by subjecting a sintered body obtained by a normal firing method to a hot isostatic firing method of 1000 to 1200.
This can be achieved by further firing at 500 ° C., 500 to 2000 atm and an acidic atmosphere. In this case, a sintered body having a relative density of 97% or more is obtained.

When a part of the Pb atom is replaced with an atom such as Ba, instead of part of the raw material powder for introducing Pb into the above-mentioned general formula, metal oxidation of the replacing atom such as BaO, CaO, SrO is carried out. Substances, carbonates or oxalates are added so as to satisfy the above range. The piezoelectric ceramic material of the present invention is used, for example, as a piezoelectric substrate forming a ladder type filter.

[0020]

Example: Purity of 99.5% or more, average particle size of 1.0 to
3.0 μm commercial PbO, TiO ₂, ZrO₂, Nb
₂O_Five, MnO₂, WO₃, BaCO₃, CaCO₃Over
And SrCO₃Each raw material powder was weighed at the ratio shown in Table 1.
It was After wet mixing this raw material powder using a ball mill
And dried at 1000 ° C.

The calcined product thus obtained is crushed using a ball mill for 24 hours.
It was wet-milled for an hour, and an organic binder was added thereto and mixed. Then, this was pressure-molded into a disk shape having a diameter of 17 mm and a height of 1.5 mm. This molded body is 1260-134
It was fired for 6 hours in an oxidizing atmosphere at 0 ° C. The obtained sintered body was polished into a diameter of 15 mm and a height of 1 mm, and silver paste was baked on both main surfaces thereof to form electrodes. The device thus obtained was immersed in insulating oil at 80 ° C., and a direct current voltage of 3 kV / mm was applied between the electrodes for polarization treatment.

The electromechanical coupling coefficient (Kp), mechanical quality coefficient (Qm), relative permittivity (εr) and frequency drift (fa drift) of the device 24 hours after the polarization treatment were measured using an Impey analyzer. . The results are shown in Table 1.

[0023]

[Table 1]

According to Table 1, all devices having a composition of piezoelectric ceramic material within the range of the present invention have Kp of 40 or more, Qm of 1500 or more, εr of 1000 or more, and fa drift of ±.
Each property within 0.3 is achieved. In particular, it can be seen that εr increases when a part of Pb atoms is replaced with Ba, Ca or Sr.

[0025]

Since the piezoelectric ceramic material of the first invention contains Pb, Zr, Ti, Nb, Mn and W so as to satisfy the above general formula, the electromechanical coupling coefficient, mechanical quality coefficient and temperature change. At the same time the stability against. In the piezoelectric ceramic material according to the second aspect of the present invention, a part of Pb atoms is replaced with at least one atom selected from the group consisting of Ba, Ca and Sr, so that the relative dielectric constant can be further increased. .

Claims (2)

[Claims] 1. A piezoelectric ceramic material represented by the following general formula. [Chemical 1] In the formula, X, Y and Z are in the following ranges and the total is 1. [Equation 1] 2. 3 to 15 atomic% of Pb is Ba, Ca and S
The piezoelectric ceramic material according to claim 1, which is substituted with at least one atom selected from the group consisting of r.