JPH08333158A - Piezoelectric ceramic composition and production of piezoelectric resonator using the same - Google Patents

Abstract

PURPOSE: To obtain a piezoelectric resonator having small variation in piezoelectricity and resonant frequency in a humidified atmosphere and excellent in thermal shock resistance. CONSTITUTION: A silver electrode 2 is formed on a piezoelectric ceramic 1 obtained by polarizing a sintered material of a piezoelectric ceramic composition comprising a main component expressed by Pb(Sn1/3 Nb2/3 )XTiYZrZO3 (X=0.01-0.50, Y=0.12-0.75, Z=0.125-0.865; X+Y+Z=1) added with 0.5-10.0wt.% of a compound of Pb(Me1/2 Te1/2 )O3 (Me is at least one kind of metal selected from the group consisting of Mn, Co, Ni and Cu), annealing at 0.4-0.8 times of Curie temperature for >=1hr and holding at a normal temperature for >=48hr and polishing.

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 and a method for manufacturing a piezoelectric resonator using the same, which has a small change in piezoelectric property and resonance frequency in a humid atmosphere and is excellent in thermal shock resistance. A piezoelectric resonator is provided.

[0002]

2. Description of the Related Art A ternary piezoelectric ceramic composition with a composite perovskite type compound in which a plurality of ions having different valences have been substituted at A site or B site in an ABO ₃ type ferroelectric has been intensively studied. . One of the three-component piezoelectric ceramic compositions is lead zirconate titanate titanate porcelain porcelain, which has a smaller amount of lead oxide vaporized than lead titanate zirconate titanate porcelain and is easy to fire and at the same time has a morphotype. Since the topic phase boundary (MPB) is expanded from a point to a line, there is an advantage that the material selection range is widened.

[0003]

However, the above-described lead zirconate titanate tin niobate porcelain has a problem that its piezoelectricity gradually decreases and its resonance frequency changes when it is exposed to a humidified atmosphere for a long time. there were.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve the conventional problems described above and to provide a piezoelectric ceramic composition having a small change in piezoelectricity and resonance frequency in a humid atmosphere.

[0005]

In order to achieve this object, the present invention provides Pb (Sn _1/3 Nb _2/3 ) _X Ti _Y Zr _Z O ₃ (where X = 0.01 to 0.50, Y = 0.12 to 0.75
Z = 0.125~0.865; X + Y + Z = relative principal component represented by 1), as a sub-component Pb (Me _1/2 T
e _1/2 ) O ₃ (however, Me is at least one metal selected from the group consisting of Mn, Co, Ni, and Cu) is added in an amount of 0.5 to 10.
A piezoelectric ceramic composition containing 0% by weight.

[0006]

According to this constitution, P is added as an auxiliary component to the basic composition.
b (Me _1/2 Te _1/2 ) O ₃ (However, Me is Mn, Co,
0.5 to 10.0% by weight of at least one metal selected from the group consisting of Ni and Cu) is added to lower the firing temperature of the composition and at the same time suppress grain growth and lower porosity. You can This makes it difficult for water to penetrate into the interior even when it is exposed to a humidified atmosphere for a long time, and at the same time, reduces the attenuation rate of elastic waves and improves piezoelectric characteristics.

[0007]

EXAMPLE An example of the present invention will be specifically described below.

As raw materials, PbO, TiO ₂ , ZrO ₂ , S
nO ₂ , Nb ₂ O ₅ , MnO ₂ , CoO, NiO, CuO,
Accurately weigh TeO ₃ so that it has the composition shown in (Table 1),
Mix well in a ball mill.

[0009]

[Table 1]

Next, the mixture was calcined at a temperature of 850 ° C. and further pulverized by a ball mill. After drying this, a polyvinyl alcohol aqueous solution as a binder was added, and the mixture was granulated and then pressure-molded at a pressure of 1 ton / cm ² to obtain a disk-shaped molded product having a diameter of 20 mm and a thickness of 1 mm. The molded body obtained here is placed in a closed furnace at a temperature of 1000 to 1250 ° C. for 1
Burned for hours. After measuring the density of the sintered body, the thickness of the porcelain was adjusted to 0.5 mm by lapping, and silver electrodes were baked on both sides.
A polarization treatment was carried out by applying a DC electric field of 3 kV / mm for 30 minutes in 100 ° C. silicon oil. Further, both sides of this disk were polished by lapping to form a piezoelectric ceramic 1 having a thickness of 0.3 mm, the polarization electrodes were removed, and then the opposite longitudinal silver electrodes 2 for thickness longitudinal mode resonance generation shown in FIG. 1 were deposited. Formed. The resonance characteristics are evaluated by the resonance frequency of the thickness-longitudinal fundamental wave of the energy-confining disk resonator and the ratio of the mountain valley [20 × log].
₁₀ (anti-resonance impedance / resonance impedance)]. Furthermore, as reliability data, changes in resonance characteristics with time and thermal shock (-40 ° C, 30 minutes ⇔ 80 ° C, 30 ° C) under high temperature and high humidity (temperature 60 ° C, relative humidity 95%) atmosphere
(Min: 100 cycles) was measured.

Among these measurement results, porcelain firing temperature (maximum density), density, electromechanical coupling coefficient K _t , mechanical quality coefficient Q _m , thickness longitudinal mode resonator fundamental wave initial peak-valley ratio (without annealing after polarization) ) And a thickness longitudinal mode resonator fundamental wave peak-valley ratio change value after elapse of 500 hours in a high temperature and high humidity (temperature 60 ° C., relative humidity 95%) atmosphere are also shown in (Table 1).

Samples within the scope of the present invention are listed in Table 2.
Curie temperature, annealing conditions, aging time after annealing and thermal shock (-
40 ° C., 30 minutes ⇔ 80 ° C., 30 minutes: 100 cycles).

[0013]

[Table 2]

In the main composition of the piezoelectric ceramic composition of the present invention, X = 0.01 to 0.50, Y = 0.12 to 0.7
The reason for limiting to 5, Z = 0.125 to 0.865 is as follows. Since the composition represented by X <0.01 or X> 0.50 is difficult to sinter as shown in (Table 1), Y <0.12, Y>0.75; Z <0. 12
5, the composition represented by Z> 0.865 is also excluded from the scope of the present invention because the piezoelectricity is remarkably reduced as shown in (Table 1), that is, the electromechanical coupling coefficient K _t is as small as 30% or less. . In addition, Pb (Me _1/2 Te _1/2 ) O ₃ (however,
Me is the addition amount or content of at least one metal selected from the group of Mn, Co, Ni and Cu) of 0.5 to 1
0.0% by weight means that the firing temperature is 1 when 0.5% or less.
The temperature is required to be 200 ° C. or higher, the number of pores is increased due to the evaporation of PbO, the composition is not uniform, and the piezoelectricity is significantly reduced in a humidified atmosphere. On the other hand, if it is added in an amount of 10.0% by weight or more, the sinterability is remarkably reduced and sufficient piezoelectricity cannot be obtained.

After polarization, after annealing for 1 hour or more at a temperature of 0.4 to 0.8 times the Curie temperature, and after polishing at room temperature for 48 hours or more, polishing is performed to obtain a resonant element because of the polarization component. The purpose is to remove the depolarizing component by heat treatment or thermal shock during mounting in advance to stabilize it.By doing this, even if the oscillator is mounted on an electronic device or thermal shock is applied, the piezoelectric resonator Depolarization and changes in resonance characteristics are minimized.

As shown in (Table 2), even if the post-polarization annealing is carried out at a temperature not higher than 0.4 times the Curie temperature, an unstable component remains in the polarized component, and when a thermal shock is applied. The amount of polarization changes, and the rate of change in the resonance frequency due to thermal shock increases accordingly. Also, when annealing after polarization is performed at a temperature 0.8 times the Curie temperature or higher, polarization is lost and oscillation does not occur. This is because the unstable component in the polarization component remains within the annealing time of 1 hour and the rate of change of the resonance frequency increases. The room temperature aging time of the piezoelectric ceramic after polarization was set to 48 hours or more.
Within 8 hours, the piezoelectric characteristics largely change with time, and the rate of change of the resonance frequency of the resonator increases, so it was excluded from the scope of the present invention.

[0017]

As described above, according to the present invention, it is possible to lower the firing temperature and, at the same time, suppress the crystal grain growth and lower the porosity.

As a result, even when it is exposed to a humidified atmosphere for a long time, it becomes difficult for water to enter the inside, and at the same time, the attenuation rate of elastic waves is lowered and the piezoelectricity is improved. A piezoelectric resonator formed using this piezoelectric ceramic composition has excellent characteristics.

[Brief description of drawings]

FIG. 1 is a perspective view of a thickness longitudinal mode energy trap type piezoelectric resonator according to an embodiment of the present invention.

[Explanation of symbols]

 1 Piezoelectric ceramic 2 Silver electrode

Claims (2)

[Claims] 1. The general formula Pb (Sn _1/3 Nb _2/3 ) _x Ti _y Z
r _z O ₃ (however, x = 0.01 to 0.50, y = 0.12 to
0.75, z = 0.125 to 0.865, x + y + z =
In addition to the main component represented by 1), Pb (Me _1/2) as a subcomponent.
Te _1/2 ) O ₃ (wherein Me is at least one metal selected from the group consisting of Mn, Co, Ni, and Cu) in an amount of 0.5 to 1
A piezoelectric ceramic composition containing 0.0% by weight. 2. The general formula Pb (Sn _1/3 Nb _2/3 ) _x Ti _y Z
r _z O ₃ (however, x = 0.01 to 0.50, y = 0.12 to
0.75, z = 0.125 to 0.865, x + y + z =
In addition to the main component represented by 1), Pb (Me _1/2) as a subcomponent.
Te _1/2 ) O ₃ (wherein Me is at least one metal selected from the group consisting of Mn, Co, Ni, and Cu) in an amount of 0.5 to 1
0.0 wt% is added to form a compact, and then the compact is fired to obtain a sintered body, which is polarized and then 0.4 times or more and 0.8 times the Curie temperature. A method for manufacturing a piezoelectric resonator, comprising annealing at the following temperature for 1 hour or more, and then forming an electrode on the surface of the sintered body.