JP2003023187A - Highly heat resistant piezoelectric element and piezoelectric device comprising it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly heat resistant piezoelectric element which can exhibit high heat resistance while sustaining a high piezoelectric constant (d), and a piezoelectric device comprising it. SOLUTION: In a titanate zirconate lead based piezoelectric material, crystal system of the piezoelectric material under room temperature is set closer to the rhombohedral phase side than the boundary of morphotropic phase so that transition is made from rhombohedral phase to tetragonal phase by heat treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high heat resistant piezoelectric element suitable for a piezoelectric device such as a piezoelectric sounding body, a piezoelectric sensor, a piezoelectric actuator, etc., and in particular, it can cope with a heating temperature at the time of solder reflow during mounting. The present invention relates to a high heat resistant piezoelectric element.

[0002]

2. Description of the Related Art Conventionally, there are various types of piezoelectric elements and devices using a piezoelectric ceramic composition, such as a piezoelectric sounding body, a piezoelectric sensor, and a piezoelectric actuator. A piezoelectric element used in such a piezoelectric device is required to have a high piezoelectric d constant in order to improve sound pressure, sensitivity, and displacement. The piezoelectric d constant is generally expressed by the following equation (1).

[0003] ^{d = k · ε 1/2 · s} 1/2 ... (1) (k: an electromechanical coupling factor, epsilon: permittivity, s: the elastic compliance) zirconate titanate piezoelectric material constituting the piezoelectric element Lead acid (hereinafter referred to as PZT) is often used. In particular, in the vicinity of the morphotropic phase boundary (hereinafter referred to as MPB) which is a phase boundary between the rhombohedral phase and the tetragonal phase, k,
Since ε and s show the maximum and the piezoelectric d constant also shows the maximum, the material composition is often set near the MPB of PZT.
The setting of the MPB composition in the PZT-based material is mainly performed by adjusting the molar ratio of Ti and Zr.

In recent years, along with surface mounting of piezoelectric applied products, piezoelectric elements are required to have high heat resistance capable of supporting heating such as solder reflow during mounting. That is,
There has been a problem that the polarized piezoelectric element is depolarized (depolarized) by the heat treatment, the piezoelectric d constant is deteriorated, and desired performance cannot be obtained.

Various methods have heretofore been used in order to suppress deterioration of characteristics due to heat treatment such as reflow. First, a method is known in which the Curie temperature of the piezoelectric element is sufficiently higher than the heat treatment temperature.

Next, in Japanese Unexamined Patent Publication No. 10-95666, in order to suppress the depolarization effect due to pyroelectric charge generated by heat treatment, the electrical resistivity of the piezoelectric material forming the piezoelectric element is lowered by composition modification or the like. A method of causing is disclosed.

Further, in Japanese Patent Laid-Open No. 11-330578, as another means for suppressing the depolarizing action due to pyroelectric charge generated by the heat treatment, a method of short-circuiting both electrodes of the piezoelectric element by using a resistor is disclosed. It is disclosed.

[0008]

However, the above-mentioned prior art has the following problems. First, in the method in which the Curie temperature of the piezoelectric element is sufficiently higher than the heat treatment temperature, the relative permittivity εr of the piezoelectric material before the heat treatment tends to decrease regardless of before and after the heat treatment. There is a problem that it is difficult to obtain a large piezoelectric d constant later.

Further, in JP-A-10-95666, although heat resistance is improved to some extent by this method,
This method alone has a problem that the piezoelectric d constant after the heat treatment is still insufficient.

Next, in Japanese Patent Laid-Open No. 11-330578, there is a problem that a device having a high driving electric field has a problem that a leak current is generated and the effective electric field is lowered, and the number of manufacturing steps of the piezoelectric element is increased, which is preferable. There wasn't.

An object of the present invention is to provide a highly heat-resistant piezoelectric element in which deterioration of the piezoelectric d constant due to heat treatment such as solder reflow at the time of mounting is small and the piezoelectric d constant after heat treatment is sufficiently high, and a piezoelectric device using the same. Is to provide. Further, the present invention that can achieve the present object is to minimize the need for composition modification of the piezoelectric material forming the piezoelectric element, and to eliminate the extra steps such as the short-circuiting of the piezoelectric element that has been conventionally required. It is unnecessary.

[0012]

In order to solve the above-mentioned problems, a high heat-resistant piezoelectric element of the present invention is a high heat-resistant piezoelectric element that uses a lead zirconate titanate-based piezoelectric material and is compatible with heat treatment. Therefore, the crystal system of the piezoelectric material at room temperature is
It is characterized in that it is set on the rhombohedral phase side of MPB so that the rhombohedral phase is transformed to the tetragonal phase by the heat treatment.

In order to solve the above-mentioned problems, another high heat-resistant piezoelectric element of the present invention is a high heat-resistant piezoelectric element that can be subjected to heat treatment, and the resonance of piezoelectric resonance of the piezoelectric element before the heat treatment. The temperature at which the frequency is minimum is 60 ℃ or more and 200 ℃
It is characterized by existing in the following range.

In order to solve the above-mentioned problems, still another high heat-resistant piezoelectric element of the present invention is a high heat-resistant piezoelectric element that can be subjected to heat treatment, and the piezoelectric resonance of the piezoelectric element after the heat treatment. The temperature at which the resonance frequency is minimum is 0 ° C or higher 1
It is characterized in that it exists in the range of 40 ° C. or lower.

In order to solve the above-mentioned problems, still another high heat-resistant piezoelectric element of the present invention is a high heat-resistant piezoelectric element that can be subjected to a heat treatment, and the piezoelectric resonance of the piezoelectric element before the heat treatment is performed. The temperature at which the resonance frequency is minimum is 60 ° C or higher 2
It exists in the range of 00 ° C. or less, and the temperature at which the resonance frequency of the piezoelectric resonance exhibits a minimum decreases by performing the heat treatment, and the resonance frequency of the piezoelectric resonance of the piezoelectric element after the heat treatment is reduced. It is characterized in that the temperature exhibiting the minimum exists in the range of 0 ° C. or higher and 140 ° C. or lower.

According to the above structure, the crystal system at room temperature of the piezoelectric material is set to the rhombohedral phase side from MPB so that the phase transition from the rhombohedral phase to the tetragonal phase occurs by the heat treatment, and the heat treatment is performed. By controlling the temperature at which the resonance frequency of the piezoelectric resonance of the piezoelectric element before and / or after the piezoelectric element has a minimum value as described above, it is excellent when mounting the piezoelectric element with high heat resistance, for example, during solder reflow. The piezoelectricity can be maintained.

Further, in the above structure, the crystal system of the piezoelectric material at room temperature is set to be closer to the rhombohedral crystal phase side than MPB so that the phase transition from the rhombohedral crystal phase to the tetragonal crystal phase is caused by the heat treatment. Even when the heat treatment is performed under severe temperature conditions such as solder reflow when mounting the piezoelectric element, the heat resistance is further excellent as compared with the conventional piezoelectric element, and the high piezoelectric d constant after the heat treatment. Can be obtained.

In the above high heat resistant piezoelectric element, it is preferable that the Curie temperature is 260 ° C. or higher and the electric insulation resistivity at room temperature is less than 1.0 × 10 ¹² Ω · cm.
According to the above configuration, a very high heat resistance can be obtained by the combined effect of adjusting the temperature at which the resonance frequency becomes minimum.

In the above high heat resistant piezoelectric element, the piezoelectric ceramic made of the lead zirconate titanate perovskite compound for forming the high heat resistant piezoelectric element is made of Cr, Mn, F.
At least one of e, Ni, Mg, Sn, Cu, Ag
It is desirable to contain at least one kind and at least one kind out of Nb, Sb, and W.

According to the above constitution, by containing the above composition, a piezoelectric element having excellent heat resistance can be more surely obtained.

In the high heat resistant piezoelectric element, the heat treatment is heating of solder reflow when mounting the piezoelectric element, and the maximum temperature in the heat treatment is preferably 200 ° C. or higher. According to the above configuration, for example, lead-free solder having a peak temperature of 260 ° C. can be used when mounting the piezoelectric element, and an environmental problem caused by lead can be easily dealt with.

In order to solve the above-mentioned problems, the piezoelectric device of the present invention is characterized by using the high heat-resistant piezoelectric element according to any one of the above. According to the above configuration, since excellent piezoelectric characteristics can be maintained even after the heat treatment, it is possible to improve the piezoelectric characteristics and the degree of freedom in mounting.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The high heat-resistant piezoelectric element of the present invention is a high heat-resistant piezoelectric element that uses a lead zirconate titanate-based piezoelectric material and can be subjected to heat treatment. It is obtained by designing (setting) the system so that it undergoes a phase transition from the rhombohedral phase to the tetragonal phase by the above heat treatment, with a slight shift from the MPB to the rhombohedral phase side. The phase transition temperature from the rhombohedral phase to the tetragonal phase (the temperature at which MPB occurs) can be grasped by measuring the temperature at which the resonance frequency of the piezoelectric resonance of the piezoelectric element exhibits a minimum.

The relationship between the temperature at which the resonance frequency of the piezoelectric resonance of the piezoelectric element exhibits a minimum, the phase transition temperature of the piezoelectric element, the high heat resistance, and the high piezoelectric d constant will be described below by taking PZT as an example.

In the piezoelectric element, when the temperature of the piezoelectric element is raised from the room temperature to the Curie temperature, the resonance frequency of the piezoelectric vibration changes variously depending on the material composition, but the Curie temperature in the middle from the room temperature to the Curie temperature. It may show a minimum value at some temperature other than. As shown in FIG. 1, this phenomenon is determined mainly by the ratio of MPB to Ti and Zr.
Rich), that is, slightly tilted to the rhombohedral phase side (disclosed in the "Piezoelectric Ceramic Material" supervised by: Electronic Material Industry Association).

Specifically, when the crystal phase of the piezoelectric element at room temperature is slightly on the rhombohedral crystal phase side of MPB (composition A in FIG. 1), it passes through the MPB as the temperature rises, and the phase shifts to the tetragonal phase side. Transfer. Generally, the piezoelectric element in this MPB is elastically softer than that in the rhombohedral phase or the tetragonal phase, so that the elastic compliance s shows a maximum. Since the resonance frequency of the piezoelectric element is inversely proportional to the square root of s, the resonance frequency of the piezoelectric element shows a minimum at the MPB passage temperature due to temperature change (see FIG. 2).

As an example, the relationship between the resonance frequency fr of the long side vibration of the piezoelectric element and the elastic compliance s ₁₁ ^E is shown in equation (2).

Fr = 1 / {2L · (D · s ₁₁ ^E ) ^1/2 } (2) (D: Density, L: Length of long side of piezoelectric element) That is, the piezoelectric material forming the piezoelectric element The crystal system of is M
When it is slightly on the side of the rhombohedral phase from PB, the resonance frequency of the piezoelectric vibration shows a minimum at a temperature of room temperature or higher and Curie temperature or lower.

Next, the piezoelectric element shown in the preceding paragraph is subjected to a heat treatment once to undergo a phase transition from the rhombohedral phase to the MPB to the tetragonal phase, then to room temperature, and then to the temperature of the resonance frequency again. When the change was evaluated, it was found that the temperature at which the resonance frequency showed the minimum value was lower than that before the heat treatment and was closer to room temperature (see FIG. 2).

Although the cause of this is not clear, once the piezoelectric element undergoes a phase transition from the rhombohedral phase to the MPB to the tetragonal phase by heat treatment, even if the temperature is returned to room temperature, the original crystal system before the heat treatment still remains. It is considered that the crystal system cannot be completely returned to the crystal system on the side of the rhombohedral phase rather than MPB. That is, it is considered that the crystal system slightly on the side of the rhombohedral crystal phase from MPB immediately after the polarization treatment is changed to a crystal system closer to immediately below MPB by the heat treatment.

Directly below the MPB is a crystal system showing the best piezoelectric characteristics. Therefore, as described in the preceding paragraph, when the heat treatment causes a slight change in the crystal system from the side of the rhombohedral phase of MPB to the vicinity of just below MPB, εr,
s is improved and deterioration of k is suppressed. (Although εr and s may decrease due to the heat treatment, the decrease due to the heat treatment is smaller than that of the element outside the scope of the present invention). This reduces the deterioration of the piezoelectric d constant of the equation (1) due to the heat treatment. Especially, if the optimum design is performed, it is possible to improve the piezoelectric d constant by heat treatment.

In the above high heat-resistant piezoelectric element, the temperature at which the resonance frequency has a minimum value before the heat treatment is 60 ° C. or higher and 200
C. or less is preferable. If the temperature is lower than 60 ° C, the heat resistance is deteriorated because the change of the crystal system due to the heat treatment is not sufficient.
If the temperature exceeds 0 ° C., the crystal system before the heat treatment is too far from MPB, so that | d ₃₁ | (representing the absolute value of d ₃₁ ) before and after the heat treatment becomes small. For the same reason, the temperature at which the resonance frequency after the heat treatment has a minimum value is 0 ° C to 140 ° C.
It is desirable to set the temperature to ° C.

As described above, the crystal-based piezoelectric material directly below the MPB has been used for the piezoelectric element requiring a high piezoelectric d constant in the related art, but it is also necessary to deal with heat treatment such as solder reflow at the time of mounting. In this case, a piezoelectric material showing a crystal system at room temperature (about 20 ° C.), which is slightly displaced from the MPB on the side of the rhombohedral phase, shows less deterioration of the piezoelectric d constant due to heat treatment, and is therefore more likely to be a highly heat-resistant piezoelectric element. Is.

The composition ratio of shifting such a crystal system from the MPB to the rhombohedral phase side is such that at the highest temperature during the heat treatment, the crystal system goes from the rhombohedral phase side to the tetragonal phase side through the MPB. When the temperature shifts to room temperature after heat treatment,
Those that return slightly to the B side, more preferably MPB
One that returns to the vicinity of before and after, and more preferably returns to immediately below the MPB.

In order to further reduce the deterioration of the piezoelectric d constant due to the heat treatment or to further increase the piezoelectric d constant after the heat treatment, the Curie temperature of the piezoelectric element is 260 ° C. or higher,
Desirably, it is sufficiently high at 280 ° C. or higher, and the electrical insulation resistivity is less than 1.0 × 10 ¹² Ω · cm.

The effect of increasing the piezoelectric d constant after the heat treatment is still insufficient if these two methods are used alone or in combination. However, by combining these two methods and the above-mentioned three methods of adjusting the temperature at which the resonance frequency has a minimum value to an optimum value, it is possible to further increase the piezoelectric d constant after the heat treatment. .

Further, since the piezoelectric element of the present invention improves the heat resistance by adjusting the crystal system of the piezoelectric material forming the element, MPB exists and it has a slope with respect to temperature (temperature dependence). With the composition system having), high heat resistance can be achieved without limiting the composition system.

That is, since the necessity of changing the composition system and modifying the composition of additives and the like is reduced, there is little concern about the characteristic deterioration of the piezoelectric element, and the development and practical application period of the piezoelectric element can be shortened. For example, in PZT-based piezoelectric material,
To adjust the crystal system near the MPB, Ti and Zr of the material composition
Since the adjustment of the content ratio of is sufficient, high heat resistance can be achieved without adding new additives or changing the composition system.

[0039]

The present invention will be described in more detail with reference to the following examples.
explain. As raw material powder, Pb ₃O_Four, TiO₂, Z
rO₂, Cr₂O₃, Sb₂O₃, La₂O₃Prepared
It was Next, these raw material powders are shown in the following formula (3).
Weigh it to the composition and add water to it.
Wet mixing using Table 1 shows the relationship between composition and sample number.
Shown in.

(Pb _0.995 La _0.005 ) {(Cr _A Sb _1-A ) _X (Ti _Y Zr _1-Y )} O ₃ (3)

[0041]

[Table 1]

In Table 1, the samples marked with * are outside the scope of the present invention.

The mixture obtained is dried and dried at 800 ° C. to 10 ° C.
It was calcined at a temperature of 00 ° C. Water and an organic binder were added to this calcined powder and wet-mixed, and the resulting mixture was dried, granulated, and press-molded to a desired size. This compact was fired at a temperature of 1000 ° C to 1200 ° C to obtain a ceramic sintered body.

The surface of this ceramic sintered body had a thickness of about 0.
After polishing to 5 mm, measuring the density of the sintered body, and forming electrodes on both main surfaces (both end surfaces in the thickness direction) by Cu / Ag vapor deposition, 1.5 kV / mm ~ in insulating oil at 80 ° C. 3.
The polarization treatment was performed with an electric field (thickness direction) of 5 kV / mm.
This polarized ceramic sintered body was cut into a rectangle of 3 mm × 13 mm to obtain a desired piezoelectric element.

Next, the electrical resistivity ρ of this piezoelectric element, the relative permittivity ε ₃₃ ^T / ε ₀ (hereinafter referred to as εr), the resonance frequency fr of the long-side vibration of the piezoelectric element fr, and the elastic compliance calculated from this fr s ₁₁ ^E , the electromechanical coupling coefficient k ₃₁ and the piezoelectric d ₃₁ constant calculated by the resonance-antiresonance method, the temperature change of fr within the Curie temperature or lower range, and the Curie temperature Tc were measured. The results are shown in Table 2.

[0046]

[Table 2]

In Table 2, the samples marked with * are outside the scope of the present invention, and T _min1 is the resonance frequency f before reflow.
r represents the temperature at which the minimum is shown.

Next, the piezoelectric element was passed through the reflow furnace twice (peak temperature: 200 ° C. to 260 ° C.), and after leaving for 24 hours, εr, fr, s ₁₁ ^E , k ₃₁ , | d ₃₁ |, fr The temperature change within the range below the Curie temperature was measured.
The results are shown in Table 3.

[0049]

[Table 3]

In Table 3, the samples marked with * are within the scope of the present invention.
Show outside, T_min2Is the resonance frequency f after reflow.
r is the temperature at which the minimum is shown, and | d₃₁｜ Reduction rate is reflow
By | d₃₁Shows the decrease rate of |, and (#) value is negative
In case of reflow, | d ₃₁Indicates that | has increased
ing.

The samples Nos. 2 to 6 and the samples Nos. 10 to 13 exist within the scope of the present invention, and the resonance frequency of the piezoelectric resonance of the piezoelectric element before the reflow (heat treatment) is performed. The minimum temperature is 60 ℃ or more 20
The temperature which exists in the range of 0 ° C. or less and at which the resonance frequency of the piezoelectric resonance of the piezoelectric element after reflow shows a minimum value is
Since it exists in the range of 0 ° C. or higher and 140 ° C. or lower, the deterioration of | d ₃₁ | due to the heat treatment is small.

As an example, | d of the samples Nos. 1 to 9
FIG. 3 shows a comparison between ₃₁ | before and after heat treatment.
The samples Nos. 1 to 9 are obtained by changing the Ti amount (Y) of the material composition so as to increase as the sample number increases.

From FIG. 3, in the sample No. 7 (Y = 0.49), | d ₃₁ | before reflow significantly decreased due to reflow. The rate of decrease was 13.2%. In comparison with this, the samples of sample numbers 2 to 6 are | d ₃₁ |
Is 10% or less, which is significantly smaller than that of Sample No. 7. However, the reduction rate of | d ₃₁ | of 10% or less due to reflow is merely an example in the examples, and does not limit the scope of the claims of the present invention.

Further, like the samples Nos. 2 to 4,
In some cases, it is possible to make the value of | d ₃₁ | after reflow higher than that of | d ₃₁ | before reflow. In addition, sample numbers 2 to 6 and sample numbers 10, 11, and 1
As described in No. 3, when the Curie temperature of the piezoelectric element is 260 ° C. or higher, it can be applied to the case where the heat treatment is reflow for eutectic solder having a peak temperature of about 240 ° C., which is desirable as a high heat resistant piezoelectric element.

Further, as in sample numbers 2 to 6 and sample numbers 10 and 13, the Curie temperature of the piezoelectric element is 280.
If the temperature is above ℃, the heat treatment is about 260 ℃.
Since it can be applied to the case of reflow soldering for lead-free solder, it is desirable as a high heat resistant piezoelectric element from the environmental aspect.

Sample Nos. 2 to 6 and Sample No. 10,
11 and 12, the electrical insulation resistivity (ρ) is 1.0 ×
When it is less than 10 ¹² Ω · cm, the effect of suppressing the depolarization effect due to the pyroelectric charge generated by the heat treatment is large,
Furthermore, heat resistance can be improved.

Further, as in Sample Nos. 2 to 6 and Sample Nos. 10 and 11, when the Curie temperature is 260 ° C. or higher and the electrical insulation resistivity is less than 1.0 × 10 ¹² Ω · cm, As a result of the combined effect with the method of adjusting the temperature at which the resonance frequency fr becomes minimum, extremely high heat resistance can be obtained. Sample numbers 3, 4, 5, 6, which are especially optimally designed,
Sample No. 10 has a very high value of | d ₃₁ | of 200 pC / N or more after reflow for lead-free solder having a peak temperature of 260 ° C., which is very promising as a high heat resistance element.

As comparative examples, sample numbers 1, 7, 8, 9 were used.
As described above, the temperature at which the resonance frequency of the piezoelectric resonance of the piezoelectric element before the heat treatment exhibits the minimum value is. When it does not exist in the range of 60 ° C. or higher and 200 ° C. or lower, εr, k by heat treatment,
Since the decrease of s cannot be suppressed sufficiently, the heat resistance is poor, which is not desirable.

The piezoelectric material of the present invention has the above-mentioned (3).
The present invention is not limited to the composition of the formula, but is applicable to piezoelectric materials having MPB in general.

Since such a high heat resistant piezoelectric element of the present invention can maintain excellent piezoelectric characteristics even after heat treatment,
It can be suitably used for piezoelectric devices such as a piezoelectric sounding body, a piezoelectric sensor, and a piezoelectric actuator.

[0061]

As described above, the highly heat-resistant piezoelectric element of the present invention has a rhombohedral structure rather than MPB so that the crystal system of the piezoelectric material at room temperature undergoes a phase transition from a rhombohedral phase to a tetragonal phase by heat treatment. This is the configuration set on the phase side.

As described above, in another high heat-resistant piezoelectric element of the present invention, the temperature at which the resonance frequency of the piezoelectric resonance of the piezoelectric element before the heat treatment exhibits a minimum is in the range of 60 ° C. to 200 ° C. It is an existing configuration.

As described above, according to still another high heat-resistant piezoelectric element of the present invention, the temperature at which the resonance frequency of the piezoelectric resonance of the piezoelectric element after the heat treatment exhibits a minimum is 0 ° C. or higher and 140 ° C. or higher.
The configuration exists in the following range.

Therefore, in the above structure, deterioration of the piezoelectric d constant due to heat treatment such as solder reflow at the time of mounting is small,
Further, there is an effect that excellent piezoelectric characteristics such as a large piezoelectric d constant after heat treatment can be exhibited.

Further, by using the high heat resistant piezoelectric element of the present invention, a high heat resistant and high performance piezoelectric device can be obtained. Further, in obtaining the high heat resistant piezoelectric element of the present invention, there is little need to change the composition system and composition change of additives etc. in the piezoelectric material forming the element, so there is little concern about characteristic deterioration, and early It is easy to develop and put to practical use. Further, in the above-described configuration, since an extra step such as a short circuit between electrodes, which is conventionally required, is unnecessary, there is an effect that the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a graph showing a phase change in PZT of a high heat resistant piezoelectric element according to the present invention.

FIG. 2 is a graph showing changes in resonance frequency with temperature before and after heat treatment of the PZT.

FIG. 3 | d ₃₁ in sample numbers 1 to 9 of the PZT
FIG. 6A is an explanatory diagram showing a change due to reflow of |
Is a graph, and (b) is a table showing a comparison between the horizontal axis Y and the sample number.

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Claims (8)

[Claims] 1. A high heat-resistant piezoelectric element using a lead zirconate titanate-based piezoelectric material, which can be subjected to heat treatment, wherein the crystal system of the piezoelectric material at room temperature is rhombohedral phase by the heat treatment. A high heat-resistant piezoelectric element, characterized in that it is set on the side of a rhombohedral crystal phase from a morphotropic phase boundary so as to make a phase transition from a tetragonal phase to a tetragonal phase. 2. A high heat-resistant piezoelectric element that can be subjected to heat treatment, wherein the temperature at which the resonance frequency of the piezoelectric resonance in the piezoelectric element before heat treatment exhibits a minimum is in the range of 60 ° C. to 200 ° C. A high heat resistant piezoelectric element characterized by being present. 3. A high heat-resistant piezoelectric element which can be subjected to heat treatment, wherein the temperature at which the resonance frequency of piezoelectric resonance in the piezoelectric element after heat treatment exhibits a minimum is in the range of 0 ° C. to 140 ° C. A high heat-resistant piezoelectric element characterized by being present in. 4. A high heat-resistant piezoelectric element that can be subjected to heat treatment, wherein the temperature at which the resonance frequency of piezoelectric resonance in the piezoelectric element before heat treatment exhibits a minimum is in the range of 60 ° C. to 200 ° C. Existence, and the temperature at which the resonance frequency of the piezoelectric resonance exhibits a minimum by performing heat treatment decreases, and the temperature at which the resonance frequency of the piezoelectric resonance in the piezoelectric element after performing the heat treatment exhibits a minimum, A high heat-resistant piezoelectric element, which is present in the range of 0 ° C. or higher and 140 ° C. or lower. 5. The Curie temperature is 260 ° C. or higher, and the electrical insulation resistivity at room temperature is 1.0 × 10 ¹² Ω.
-It is less than cm, The high heat resistant piezoelectric element in any one of Claim 1 thru | or 4 characterized by the above-mentioned. 6. A piezoelectric ceramic made of a lead zirconate titanate-based perovskite compound for forming the high heat resistant piezoelectric element comprises Cr, Mn, Fe, Ni, Mg, Sn, Cu, A.
at least one of g, and Nb, S
6. The high heat resistant piezoelectric element according to claim 1, containing at least one of b and W. 7. The heat treatment is a solder reflow heating at the time of mounting a piezoelectric element, and the maximum temperature in the heat treatment is 200 ° C. or higher. High heat resistant piezoelectric element. 8. A piezoelectric device comprising the high heat-resistant piezoelectric element according to claim 1.