JPS5917983B2 - oxide piezoelectric material - Google Patents

Description

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

More specifically, (1-x)PbTiO3xPb(Me
1/3Nb2/3)03x- in the two-component basic composition
0.01 to 0.15, and some of the Pb atoms are Br
PbSr [(Me1/3
Nb・O2/3)Ti]Os (where Me is Ni, Co
(1) oxide-based piezoelectric material. Furthermore, the present invention relates to the oxide piezoelectric material containing 0.05 to 2.0% by weight of at least one of MnO, Ni0, and Fe2O3 as a subcomponent. j5 As is well known, piezoelectric materials are used in a wide range of fields as elements such as ultrasonic vibration elements, transducer elements such as mechanical filters, ceramic filters, ceramic resonator elements, vibrometers, and accelerometers.

For this kind of use ■0PbTiO3-PbZr0
Improved tri-binary oxide piezoelectric materials have been developed. For example, the above PbTiO_3-PbZr0
Bi2O3, Cr2O3, MnO2, 2no in the 3 binary system
Attempts have been made to improve piezoelectric properties by adding additives such as. Ma■5 PbTiO_3-PbZr03
-Pb(Mg1/3Nb2/3)03 ternary piezoelectric materials have also been developed. However, these piezoelectric materials have a ferroelectric Curie temperature of about 300° C., and cannot be used at temperatures higher than that. Further, the dielectric constant of the piezoelectric material is 1
000?0, making it unsuitable for applications in the high frequency range. On the other hand, PbT has a small dielectric constant of 150 to 250.
iO_3-based materials have also been reported, but due to cracks that occur after sintering, it is not possible to obtain large sintered bodies with a diameter of 20m or more, and the polarization conditions are 200°C, 35°C, and an applied voltage of 6°C.
Since the OKV/cm is very strict, there were drawbacks such as low product retention.

The purpose of the present invention is to solve the above-mentioned problems, to be able to be used stably even at a high temperature of 30°C or higher, to be suitable for applications in the high frequency range of several MHz or higher, and to be suitable for use in the high frequency range of several MHz or higher, and to be suitable for use with conventional PbTiO3-based piezoelectrics. The object of the present invention is to provide a PbTiO3-based oxide piezoelectric material that is much easier to polarize than other materials. That is, the oxide piezoelectric material according to the present invention contains Pb
TlO3-Pb(Mel/3Nb2/3)03 binary system (
Reliability was further improved by substituting a part of Pb with Sr in MelliCO, Ni) and adding a small amount of at least one oxide of MnO, NiO, and Fe2O3 as subcomponents. It is something.

More specifically, (1-x)PbTiO3-XPb(M
el/3Nb2/3) 03 Two-component basic composition (Tashashi Me
is either Ni or CO) and XO.

Ol ~ 0.15, and some of the Pb atoms are replaced by Sr.
．． It is substituted by 5 to 20 atomic percent. That is, if expressed as a general formula, Pbl-ASra [(Mel/2Nb1/2
)XTil-x]03 (in the formula, Me is either Ni or CO), x = 0.01 to 0.15
, a=0.01 to 0.20. Furthermore, MnO, NiO as subcomponents
and at least one of Fe2O3 from 0.05 to 2.0
This is an oxide piezoelectric material containing an additive amount by weight. Such an oxide piezoelectric material of the present invention can generally be easily manufactured by a powder metallurgy method.

For example, PbO, TiO2, SrCO3, MnCO3,
Raw material oxides such as NlO, Nb2O5, Fe2O3, and MeO (Me is one of Ni and CO) are weighed out accurately in predetermined proportions, and mixed well using a ball mill or the like. Note that the raw material used at this time may be a compound that is converted into an oxide by heating, such as a hydroxide, carbonate, or oxalate. The mixture is then mixed with e.g.
The powder is preliminarily calcined at a temperature of about 0.000 to 900.degree. C., and then 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 this prepared powder to form a powder of 0.5 to 2t0n/C.
After pressure molding with a pressure of about d, 1100-1200℃
Bake at a temperature of about During this firing, there is a risk that some of the PbO, which is one of the components, may evaporate and diffuse, so the firing is carried out in a closed furnace, and the maximum temperature is generally 0.5
~3 hours is sufficient. Furthermore, the present invention will be explained in detail. First, (1-x)PbTiO3-XPb(Me
l/2Nb1/2)03 (where Me is either CO or Ni), x = 0.01 to 0,1
The reason for limiting the value to 5 is that when x < 0.01, the sinterability is poor and dense porcelain cannot be obtained, and when x > 0.15, the Kiri temperature decreases to below 350 °C and is stable at high temperatures of 300 °C or higher. In addition, the dielectric constant is 300 or more, making it difficult to use in a high frequency range.

Next, the amount of Pb replacement by Sr was limited to 1.0 to 20 at%, which means that it is 1.0 at%, and at least PbTiO3
This is because the effect of substitution, which facilitates polarization of piezoelectric materials and facilitates sintering of porcelain, hardly appears.
This is because if the amount is more than 20 atomic %, the Kiri temperature will be 350.degree. C. or less, making it 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 why these subcomponents are limited to 2.0% by weight is that if the amount is less than 0.05% by weight, these subcomponents will not show the effect of improving the temperature characteristics, aging characteristics, and mechanical quality coefficient of PbTiO3 ceramic. This is because if the amount is too large, the sinterability of the ceramic will deteriorate.

Thus, the following effects can be obtained by the present invention. First, PbTiO3 has a temperature of 5
Pb(Mel/2Nb1/2)03 (However, Me
/1iC0, Ni) is used as one of the components, and some of the Pb is replaced with Sr, so these act as mineralizers and facilitate sintering. It has become normalized.

This facilitation of sintering ultimately lowers the sintering temperature, suppresses the evaporation and dissipation of PbO, which forms part of the composition, and finally makes it easier to obtain a dense piezoelectric material. Furthermore, when it comes to PbTiO3-based ceramics, it is important to sinter them in a way that suppresses grain growth, but in the present invention, by substituting some of the Pb atoms with Br, grain growth is reduced to 1 to 3 μm or less. It has the effect that it can be suppressed and firing can be made easier. Second
In addition, by substituting a part of Pb with Sr, it is possible to easily polarize PbTiO3 ceramic, which has been difficult to polarize.

In other words, the polarization conditions for conventional PbTiO3 ceramics are 60 to 80 KV/at a high temperature of 180 to 200°C.
Although the piezoelectric material of the present invention required a voltage of 80 to
Sufficient polarization can be achieved under relaxed conditions of 100° C. and 40 to 60 KV/Cm. Thirdly, some of the Pb is
By substituting with r, changes in mechanical strength over time after polarization can be improved.

In other words, with conventional PbTiO3 materials, mechanical strength decreased approximately 1,000 hours after polarization, causing cracks and making it difficult to create large-sized resonators, whereas the material of the present invention significantly improves this. There is an effect that it can be done. Fourth
By adding at least MnO, NiO, and Fe2O3 to the ceramic material, the temperature characteristics, aging characteristics, and mechanical quality factor can be significantly improved compared to conventional PbTiO3 ceramics.
Large-sized sintered bodies such as x 1 t, 1001 x 20 W x 1 t, etc. can be easily manufactured.

Next, examples of the present invention will be described.

The sintered sample was polished to 20ψ×1.0[Mt, silver electrodes were attached to both sides and polarized under the conditions of 10°C, 6OKV/CTn, and then PrOc. IREVOl. l37(゛4
9) 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. T is the firing temperature (°C), D is the specific gravity (measured at 23°C), and ε is the dielectric constant (
), Kt is the electromechanical coupling coefficient (%), Qm is the mechanical quality coefficient, and Tc is the temperature. Among these samples, the electromechanical coupling coefficient Kt depending on the polarization temperature for the samples of Example 7 and Reference Example 2
When the value of was measured, the results shown in FIG. 1 were obtained. In FIG. 1, curve a represents the case of Example 7, and curve b represents the case of Reference Example 2.
The case is shown below. Embodiments of the present invention are based on conventional PbTiO3
It can be seen that polarization is easier compared to ceramics. Next, changes in dielectric constant due to temperature were measured for the samples of Examples 1 and 7 and Reference Example 3 among these samples, and the results shown in FIG. 2 were obtained.

In FIG. 2, curve a shows the case of Example 1, curve b 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 a high temperature 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 b shows the case of Example 7, and curve c shows the case of Reference Example 3. According to this figure, in both Examples 1 and 7 of the present invention, Kt is almost constant over a wide temperature range from room temperature to 4000C because the 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 samples of Example 13 and Example 18, which had the same basic composition but added and contained at least one of MnO, NlO, and Fe2O3 as subcomponents,
Ceramic vine resonators were made using 19 samples and 20 samples, and the time-dependent characteristics of the frequency constant Nt (Hz, m) were determined, and the results shown in FIG. 4 were obtained.

In FIG. 4, curve a represents the case of Example 13, and curve B represents the case of Example 13.
, c, and d are Examples 18, 19} and 20, respectively.
The case is shown below. It can be seen that the aging properties become better by adding MnO, NiO, and Fe2O3. Furthermore, we measured the temperature characteristics and aging characteristics of the resonant frequency for the ceramic resonator of the same sample as above.
The results shown in Table 2 were obtained. MnO,. NiO, Fe2O
It can be seen that by adding 3, the temperature characteristics and aging characteristics are improved. Furthermore, it is shown that Qm is dramatically improved by adding subcomponents. Figure 5 shows the composition of Example 13 Reference Example 1 with a diameter of 50 cr.
Create a disc oscillator of n and show the mechanical strength after polarization T
The results of investigating the temporal change of anδ are shown. In FIG. 5, curve a shows the case of Example 13, and curve b shows the case of Reference Example 1. In the composition of Reference Example 1 in which Sr substitution was not performed, Tan δ increased rapidly and cracks occurred in the vibrator after 100 hours 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. 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) Vibration, acceleration measurement, and pressure measurement of high-temperature objects;
It is possible to measure the vibration and acceleration of objects that reach temperatures close to 500 degrees Celsius or objects that experience 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 amplitude operation.

(4) Application in high frequency range Conventional piezoelectric materials have a dielectric constant of about 1000, which is too large, making them unsuitable for use in high frequency ranges.

Generally, impedance z is Z=d/(2πF, ε, s)
(Here, D and s are the thickness and cross-sectional area of the sample, f is the operating frequency, and ε is the dielectric constant.) Therefore, d is f
It is necessary to make it thinner in inverse proportion to . In the end ZOcl/(F
2, ε, s), but as f becomes higher, Z becomes effective as a square and rapidly decreases. To match Z, it is necessary to reduce s or ε, but there is also a processing limit to s, so
It is advantageous to reduce ε. The piezoelectric material of the present invention has a dielectric constant ε of about 150 to 250, which is 1/1 compared to conventional materials.
It is 5 to 1/10. Therefore, if conventional materials can be used up to 10 MHz, the material of the present invention can be used up to about 50 MHz. (5) Probe for linear scan type ultrasound diagnostic equipment The sound wave conversion elements in probes for ultrasound diagnostic equipment are required to be larger in size and thinner as the frequency becomes higher. It was difficult to make the element larger in size and thinner with conventional piezoelectric materials, but the material of the present invention has good sinterability, so it can be made into a large and thin plate with excellent mechanical strength (for example, it can be made into a large and thin plate with a length of 50 mm). ~100, width 15~20 [m1 thickness 200t
tm) is easily realized. 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 of the frequency, the aging characteristics, and the aging characteristics of the mechanical strength are problematic, but since the rate of change in these is small, it can be used satisfactorily for practical use.

[Brief explanation of drawings]

The drawings show an example of the characteristics of the oxide piezoelectric material according to the present invention, and Figure 1 shows the polarization temperature and electromechanical coupling coefficient Kt(0/)).
Figure 2 is a diagram of the relationship between temperature and permittivity, Figure 3 is a diagram of the relationship between temperature and electromechanical coupling coefficient Kt (%), and Figure 4 is the relationship between time and frequency constant Nt (Hz, m ), Figure 5 is a relationship curve diagram between time and Tan δ (%),
FIG. 6 each shows a ternary diagram showing the claims.

Claims (1)

[Claims] 1 (1-x)PbTiO_3-xPb(Me1/3N
b2/3) O_3 two-component basic composition (Me is Ni,
any type of Co), x = 0.01 to 0.0
5, and a part of the Pb atoms are replaced by 1.0 to 20 atomic % of Sr. 2 (1-x)PbTiO_3-xPb(Me1/3N
b2/3) O_3 two-component basic composition (Me is Ni,
Co), x = 0.01 to 0.1
5, and some of the Pb atoms are replaced by 1.0 to 20 at% of Sr, and Mno, NiO and Fe_2 are added as subcomponents.
An oxide piezoelectric material characterized by containing at least one type of O_3 in an amount of 0.05 to 2.0% by weight.