JPS5831750B2 - oxide piezoelectric material - Google Patents

Description

[Detailed description of the invention] The present invention relates to oxide piezoelectric materials.

More specifically, (1-x) PbT 103-xP
b (Me'J/3 NtJ'3)03 pb S in which x = 0.01 to 0.15 in the two-component basic composition and in which some of the pb atoms are polysubstituted with 1.0 to 18 atoms with Sr
r((Me4pb,k)Ti)03 (where Me is Z
The present invention relates to an oxide-based piezoelectric material containing at least one of n, Mg).

Furthermore, as a subcomponent, Mno. Nio and Fe2O
The present invention relates to the above-mentioned oxide piezoelectric material containing at least one type of ρ in an amount of 0.05 to 2.0% by weight.

As is well known, piezoelectric materials are used in a wide range of fields as ultrasonic vibration elements, transducer elements such as mechanical filters, ceramic filters, ceramic resonator elements, vibrometers, accelerometers, and other elements.

For such uses, improved PbTiO3-PbZrO3 binary oxide piezoelectric materials have been developed.

For example, B 1203 in the PbTiO3PbZrO3 binary system
Attempts have been made to improve the piezoelectric properties by adding additives such as , Cr2 o3y Mn02y ZnU.

PbTl03-2 PbZr03-Pb(Mg715)03 ternary piezoelectric materials have also been developed, but these piezoelectric materials have a ferroelectric Curie temperature of about 300°C and cannot be used at temperatures higher than that. Ta.

Further, the dielectric constant of the piezoelectric material is about 1000, which makes it unsuitable for application in a high frequency range.

On the other hand, P b has a small dielectric constant of 150 to 250.
T i 03-based materials have also been reported, but because of cracks that occur after sintering, it is not possible to obtain large sintered bodies with a diameter of 20 mrn or more, and the polarization conditions are extremely severe, with an applied voltage of 60 KVA 1 n at 200 °C. However, there were drawbacks such as low actual product accuracy.

The purpose of the present invention is to solve the above-mentioned problems, to be able to be used stably even at high temperatures of 300°C or higher due to its high Curie temperature, to be suitable for applications in the high frequency range of several MHz or higher, and to be suitable for applications in the high frequency range of several MHz or higher, and to be suitable for use with conventional PbTiO3-based piezoelectric materials. The PbTr03-based oxidized piezoelectric material is a piezoelectric material that is much easier to polarize than the PbTr03-based oxidized piezoelectric material.

That is, the oxide piezoelectric material according to the present invention is PbT 1
03-P b (M comfort N bi) o3ko (M e is M
g, at least one kind of Zn), some of the Pb is replaced with Sr.
It is substituted with MnO and N as subcomponents.
Reliability is further improved by adding a small amount of at least one kind of oxide of iO and Fe2O3.

For further details, see (1x)PbTiO3xPb(Me/Nb5a)os two-component basic composition (Me is Zn, M
g), X=0.01 to 0.1
5, and some of the pb atoms are substituted with 1.0 to 20 atomic % of Sr.

That is, if expressed as a general formula, Pb1-as r a ((
Me old NbA)xTil-x)03 (In the formula, Me is Z
n, at least one type of Mg), x=
001 to 0.15, a=o, and 01 to 0.20.

The oxide piezoelectric material further contains at least one of MnO, NiO, and Fe2O3 as a subcomponent in an amount of 0.05 to 2.0 weight.

Such an oxide piezoelectric material of the present invention can generally be easily manufactured by a powder metallurgy method.

For example, PbO1T t02.8 rcO3, MnC0
3NiO, Fe2O3, Nb2o, and MeO(Me
(at least one of Zn and Mg) is accurately weighed out in a predetermined ratio, and mixed well using a ball mill or the like.

The raw material to be removed may be a compound that is converted into an oxide by heating, such as a hydroxide, carbonate, or oxalate.

Next, the mixture is preliminarily calcined at a temperature of, for example, about 600 to 900° C., and further pulverized using a ball mill or the like to obtain a prepared powder.

After that, water or a binder such as polyvinyl alcohol is added to the prepared powder to form a powder of 0.5 to 2 tons/
After pressure molding with a pressure of about ffl, 1100~120
Fire at a temperature of about 0°C.

During this firing, there is a possibility that a part of PbO, which is one of the components, may evaporate and diffuse, so the firing is carried out in a closed furnace.
Further, it is generally sufficient to maintain the temperature at the maximum temperature for about 0.5 to 3 hours.

Furthermore, the present invention will be explained in detail.

First, (x-1)PbTi03-xPb(Me3'Nb
03 (However, in the basic composition of at least one of Me, Mg, and Zn, the reason for limiting x to 0.01 to 0.15 is that when x<0.01, sinterability is poor and dense porcelain cannot be obtained. First, if x > 0.15, the Curie temperature will drop to below 350°C, making it impossible to use stably at high temperatures above 300°C, and the dielectric constant will also exceed 300, making it difficult to use in high frequency ranges. be.

Next, the reason why the amount of Pb substitution by Sr is limited to 1.0 to 20 atoms is that if it is less than 10 atoms, P b T 1
This is because the effect of substitution, which facilitates the polarization of 03 series piezoelectric materials and facilitates the sintering of porcelain, hardly appears, and if there are more than 20 atoms, the Curie temperature is 350°C
This is because it becomes difficult to use at high temperatures.

Furthermore, MnO, NiO and Fe2O as subcomponents
The added content of at least one of 3 is 0.05 to 2.0
The reason for limiting the weight to a large weight is that if the weight is less than 0.05 weight φ, these subcomponents will not show the effect of improving the temperature characteristics, aging characteristics, and mechanical quality coefficient of the P b T t Os ceramic. This is because if the amount is more than 0.0 weight, the sinterability of the ceramic will deteriorate.

Thus, the following effects can be obtained by the present invention.

First, P bT i03 had a Curie temperature of around 500°C and was considered to be a promising piezoelectric material, but it was not practical due to the difficulty of sintering.
b(MeIZNbsu03 (However, Me is M g , Z
Since at least one type of n) is used as one of the components, and a part of PB is replaced with Sr, these act as mineralizers and facilitate sintering.

This facilitation of sintering ultimately lowers the sintering temperature, suppressing the evaporation and dispersion of PbO, which forms part of the composition, and ultimately making it easier to obtain a dense piezoelectric material.

Furthermore, in PbTiO3-based ceramics, it is important to perform firing to suppress grain length.In the present invention, by substituting some of the Pb atoms with Sr, grain growth is suppressed to 1 to 3 μm or less. This has the effect of making it easier to bake.

Second, by substituting a part of Pb with Sr, it is possible to easily polarize PbTiO3 ceramic, which has been difficult to polarize.

That is, conventional PbTiO3 ceramics have polarization conditions of 60 to 80 KVl at a high temperature of 180 to 200°C.
The i% piezoelectric material of the present invention that required a voltage of crn was 80
~100℃.

Sufficient polarization can be achieved under relaxed conditions of 40 to 60 KVlcm.

Thirdly, by substituting a part of Pb with Sr, changes in mechanical strength over time after polarization can be improved.

That is, in the conventional P b T t 03 material, 1 after polarization.
After 1,000 hours, mechanical strength decreases and cracks occur, making it difficult to manufacture large-sized vibrators, but the material of the present invention has the effect of significantly improving this problem.

In addition to the above-mentioned effects, MnO is used as a subcomponent.

By adding and containing at least one of NiO and Fe2Oρ, the temperature characteristics, aging characteristics, and mechanical quality factor can be significantly improved compared to conventional P b T t 03 ceramics.
Large-sized sintered bodies such as X1 t, 100100tX20, etc. can be easily produced.

Next, examples of the present invention will be described.

20. G
>49) The piezoelectric properties were each measured by the standard circuit method shown in Nos. 1378 to 1395.

These measurement results are shown in Table 1 along with the composition ratios of these sintered bodies.

In Table 1, F and T are the firing temperature CO, D is the specific gravity (measured at 23°C), and ε is the dielectric constant (IHz, 23°C).
Kt is the electromechanical coupling coefficient (%), Qm is the mechanical quality coefficient, and Tc is the Curie temperature.

Among these samples, the values of the electromechanical coupling coefficient Kl depending on the polarization temperature were measured for the samples of Example 7 and Reference Example 2, and the results shown in FIG. 1 were obtained.

In FIG. 1, curve a shows the case of Example 7, and curve 2 shows the case of Reference Example 2.

It can be seen that the examples of the present invention are easier to polarize than the conventional PbTi03-based ceramics.

Next, for the samples of Example 1.7 and Reference Example 3 among these samples, changes in dielectric constant due to temperature l were measured, and the results shown in FIG. 2 were obtained.

In FIG. 2, curve a shows the case of Example 1, curve S shows the case of Example 7, and curve C shows the case of Reference Example 3.

It can be seen that Examples 1 (curve a) and 7 (curve b) of the present invention have high Curie temperatures and can be used at temperatures of 300° C. or higher.

Furthermore, when the change in electromechanical coupling coefficient Kt with respect to temperature was measured for the same sample, the results shown in FIG. 3 were obtained.

In FIG. 3, curve a shows the case of Example 1, curve S shows the case of Example 7, and curve C shows the case of Reference Example 3.

According to this figure, in Examples 1 and 7 of the present invention, Kt is almost constant over a wide temperature range from room temperature to 400°C because the Curie temperature is high.

The results shown in FIGS. 2 and 3 show that the piezoelectric material according to the present invention can be used at the highest operating temperature for a piezoelectric material.

Furthermore, the sample of Example 13 has the same basic composition and ☆ composition, but contains MnO and NiO as subcomponents.

Ceramic resonators were made using the samples of Examples 18, 19, and 2o containing at least one type of Fe2O3, and the time-dependent characteristics of the frequency constant N t (Hz - m) were determined, as shown in Figure 4. Got the results.

In FIG. 4, curve a is the curve for Example 13, c and d are for Example 18, 19 and 20, respectively.
The case is shown below.

Mob, Nip. It can be seen that the addition of Fe2O3 improves the aging characteristics.

Furthermore, when we measured the temperature characteristics and aging characteristics of the resonant frequency of the ceramic resonator of the same sample as above, we found that the second
The results shown in the table were obtained.

By adding MoO, NiO, and Fe2O3, the temperature characteristics and aging characteristics were improved. tan, which indicates the strength of
The results of examining changes in δ over time are shown.

In FIG. 5, curve a corresponds to Example 13, and reference example 2 corresponds to curve a.
Each case is shown below.

) In the composition of Reference Example 2 in which Sr substitution was not performed, tan δ increased rapidly and cracks occurred in the vibrator after 100 hours or more after polarization, whereas in the case of Example 13, tan δ
No change was observed, indicating that the change in mechanical strength over time was improved by Sr substitution.

1. The Qm is dramatically improved by the addition of the sub-i component. τ (Has) As is clear from the above examples, the piezoelectric material according to the present invention has many features such as being able to be used stably even at high temperatures of 300°C or higher and being usable in a high frequency range.

Furthermore, since the rate of change in temperature characteristics, aging characteristics, etc. is small, it can exhibit excellent functions as various conversion elements.

Thus, the oxide piezoelectric material according to the present invention can be said to be suitable for, for example, the following uses.

(1) It is possible to measure vibration, acceleration, and pressure of high-temperature objects, and to measure vibrations and acceleration of objects that reach temperatures close to 500°C or objects that undergo rapid temperature changes.

Similarly, pressure inside hot objects can be measured. (2) Ultrasonic application for high-temperature objects It can be used as an ultrasonic generation source during ultrasonic processing of high-temperature objects, or as an element for ultrasonic inspection of high-temperature objects.

(3) Generation of strong ultrasonic waves When ordinary piezoelectric materials are operated with large amplitude, the temperature rises due to heat generation and the piezoelectric material according to the present invention becomes unusable.
Since it can withstand use at temperatures above 0°C, it is advantageous for generating powerful ultrasonic waves through large-radiation operation.

(4) Application in high frequency applications Conventional piezoelectric materials have a dielectric constant of 100 degrees, which is too large, making them unsuitable for use in high frequency ranges.

Generally, impedance Z is Z=d, /(2πf・ε・s
) (where d and s are the thickness and cross-sectional area of the sample, f is the operating frequency, and ε is the dielectric constant.

) is given by Therefore, d needs to be made thinner in inverse proportion to f.

In the end, it becomes Z■1/(f2 · ε · S), but as f becomes higher, Z becomes effective as a square and rapidly decreases.

It is necessary to make S or ε small for Z matching, but since S has a limit in processing, it is advantageous to make ε small.

The piezoelectric material of the present invention has a dielectric constant ε of about 150 to 250, which is ν to 7 compared to the conventional piezoelectric material.

Therefore, if conventional materials can be used up to 10 MHz,
Using the material of the present invention, frequencies up to about 50 MHz are possible.

(5) Probe for linear scan type ultrasound diagnostic equipment The sound wave conversion element in the probe for ultrasound diagnostic equipment has a large shape and is required to be made thinner as the frequency becomes higher.

It was difficult to reduce the thickness of the large-sized fL of the element with conventional piezoelectric materials, but the material of the present invention has good sinterability, so it can be made into a large-sized thin plate with excellent mechanical strength (for example, 50 to 10 mm in length).
0mm.

A width of 15 to 20 mm and a thickness of 200 μm is easily achieved.

As described above, it can be seen that the use of the piezoelectric material of the present invention as shown in the ternary diagram in FIG. 6 is useful for applications that were previously impossible.

When used as a high-frequency filter or resonator, the temperature characteristics and aging characteristics of the frequency are problematic; however, since the rate of change in these characteristics is also small, it can be used satisfactorily for practical use.

[Brief explanation of the drawing]

The drawings show an example of the characteristics of the oxide piezoelectric material according to the present invention. FIG. 1 is a relationship curve between polarization temperature and electromechanical coupling coefficient Kt (%), FIG. 2 is a relationship curve between temperature and dielectric constant, Figure 3 is a diagram of the relationship between temperature and electromechanical coupling coefficient Kt.
The figure shows a relationship curve between time and frequency constant Nt (Hz, m), and FIG. 5 shows time and tan δ. FIG. 6 shows a ternary diagram showing the scope of claims.

Claims (1)

[Claims] In the basic two-component composition of 1(1-X)PbTiO3-XPb(Me)/3NbNe03 (at least one of Mei/'iZn1Mg), x=0.01 to 0.15, An oxide piezoelectric material characterized in that a part of Pb atoms are replaced with 1.0 to 20 atoms of Sr. 2 (1-x) PbT 1o3-xPb (Me
f Nbh) 03 two-component basic composition (Me is Zn,
at least one type of Mg), x=0.01 to 0.
15, and some of the pb atoms are 1.0 to 20 with Sr.
Atoms are polysubstituted, and at least one of MnO, NiO, and Fe20s is added as a subcomponent to 0.05 to 2.0
An oxide piezoelectric material characterized by containing a large amount of additives.