JPS5831748B2 - oxide piezoelectric material - Google Patents

Description

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

More specifically, (1-x) PbTiO3-xP
b (Me'/3 Sb"/3)03 In the two-component basic composition, x = 0.01 to 0.15'"'C8, and pb
Pb5 with 1.0 to 20 at.% of atoms replaced with Sr
r[(Me1/3Sb2/3)Ti]03 (where Me
is Zn.

This invention relates to a Sn-type oxide piezoelectric material.

Furthermore, as subcomponents, MnO, NiO and Fe2
The present invention relates to the oxide piezoelectric material containing at least one type of 0.03 in an amount of 0.05 to 2.0% by species.

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, in the above PbTi03-()bZr03 binary system, B
Attempts have been made to improve piezoelectric customization by adding additives such as 12031Cr203, MnO2, and ZnO.

Also 2 PbT 103- PbZ r03- Pb (Mg-
Piezoelectric materials based on the qNb-H)03 ternary system 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 about 1000, which makes it unsuitable for application in a high frequency range.

On the other hand, pbT has a small dielectric constant of 150 to 250.
Although i03-based materials have also been reported, large sintered bodies with a diameter of 20 mm or more cannot be obtained due to cracks that occur after sintering, and the polarization conditions are 200°C and an applied voltage of 60°C.
/cfrL, each of which had drawbacks such as a low yield of the product.

It is an object of the present invention to solve the above 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 in the conventional P b T io The object of the present invention is to provide a PbTiOs-based oxide piezoelectric material whose polarization operation is much easier than that of the 3-based piezoelectric material.

That is, the oxide piezoelectric material according to the present invention is PbTi0
In the 3-Pb(Mel, (Sb2/3)03 binary system (Me is either Zn or Sn), a part of 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.

More specifically, (1-x)PbT 1o3-xPb
(Me1/3Sb”/) 03 two-part basic composition (Me is Zn.

any type of Sn), x=0.01 to 0.1
5, and some of the Pb atoms are substituted with 1.0 to 20 atom % of Sr.

That is, if expressed as a general formula, Pb1-a Sra((Me
'/Sb2/3)xTil-x)03 (where Me is Z
n, Sn), x =
The present invention is an oxide piezoelectric material characterized in that 0.01 to 0115 degrees a=o and 01 to 0.20.

This is an oxide piezoelectric material containing 0.05 to 2.0% by weight of at least one of MnO, NiO, and Fe2O3 as a subcomponent.

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

For example, PbO2TiO2, SrCO3,1! l/Ir
ICO3゜N io 2 Fe2032 S b20
3 and MeO (Me is Zn.

Raw material oxides such as any one of Sn) are appropriately 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/c.
After pressure molding at a pressure of about riL, 1100 to 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 constituents, may evaporate and diffuse, so the firing is carried out in a closed furnace, and it is generally sufficient to maintain the maximum temperature for about 0.5 to 3 hours.

Furthermore, the present invention will be explained in detail.

First, (1-x) P bT 103-xPb (M
e1/3 Sb”/3 ) 03 (Me is Zn, S
In the basic composition of n), x=0.01
The reason for limiting it to ~0.15 is that when x < 0.01, sinterability is poor and dense porcelain cannot be obtained, and when x > o, 15, the Curie temperature decreases to below 350 °C and high temperatures of over 300 °C occur. This is because, in addition to being unable to be used stably, the dielectric constant is 300 or more, making it difficult to use in a high frequency range.

Next, when the amount of substitution of pb by Sn is limited to 1.0 to 20 at%, if it is less than 1.0 at%, P b T
This is because the substitution effect of facilitating polarization of iOs-based piezoelectric materials and sintering of porcelain is hardly manifested, and more than 20 atom % has a Curie temperature of 350
This is because it becomes difficult to use at high temperatures.

Furthermore, MnO, NiO and Fe2O3 as subcomponents
The reason for limiting the content of at least one type of addition to 0.05 to 2.0% by weight is that less than 0.05% by weight,
This is because these subcomponents do not show the effect of improving the temperature characteristics, aging characteristics, and mechanical quality coefficient of PbTiO3-based ceramics, and if the amount exceeds 20% by weight, the sinterability of the ceramic deteriorates.

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

First, P b T io 3 has a Curie temperature of 500
℃, and was considered to be a promising piezoelectric material, but it was not practical due to difficulties in sinterability.
(However, Me is one of Zn2Sn) is used as one of the components, and a part of Pb is replaced with Sr, so these act as mineralizers and facilitate sintering. I'm used to it.

This facilitation of sintering ultimately lowers the sintering temperature, suppresses the evaporation and dissipation of PbO, which is a part of the composition, and ultimately makes it easier to obtain a dense piezoelectric material.

Furthermore, in PbTiOs ceramics, it is important to perform firing to suppress grain growth, but in the present invention, by replacing some of the Pb atoms with Sr,
The effect is that the growth of dalein can be suppressed to 1 to 3 μm or less, and firing can be facilitated.

Second, 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 conventional P b TiOs ceramic is
The polarization conditions are 60-80℃ at a high temperature of 180-200℃.
KV/cyn, (1 tL pressure was required, but the piezoelectric material of the present invention can be sufficiently polarized under relaxed conditions of 80 to ioo°C and 40 to 60 KV/cTL.

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 PbTiO3 material, 1000
While it has been difficult to produce large-sized vibrators due to a decrease in mechanical strength over time and cracks, 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 MiO and Fe2O3, temperature customization, aging customization, and mechanical quality coefficient can be significantly improved compared to conventional P b TiOa ceramics. Large-sized sintered bodies such as 101 x 20 W x 1 can be easily produced.

Next, examples of the present invention will be described.

The sintered sample was polished to 20 mm x 1.0 iit, and silver electrodes were baked on both sides at 100°C, 60 KV/CrrL.
After polarization under the conditions of Proc, IRE Vol.
137 (49) 1378-1395, etc., the piezoelectric properties were measured in accordance with the standard circuit method disclosed in 137(49) 1378-1395.

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

In Table 1, F and T represent the firing temperature ('C),
D is the specific gravity (measured at 23°C), and ε is the dielectric constant (IHz, 2
), Kt is the electromechanical coupling coefficient (measured at 3°C), and Qm
represents the mechanical quality factor, and Tc represents the Curie temperature.

Among these samples, the values of the electromechanical coupling coefficient Kt 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 Leprosy Example 7, and curve a shows the case of Reference Example 2.

Examples of the present invention are 1. It can be seen that polarization is easier compared to conventional PbTiO3 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, the curve 1a shows the case of Actual Example 1, the curve 1b shows the case of Example 7, and the curve C shows the case of Reference Example 3.

It can be seen that practical 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 Practical Example 1, curve S shows the case of Example 7, and curve C shows the case of Reference Example 3.

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

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 basic composition is the same as that of the sample of Practical Example 13, but MnO and NiO are added as subcomponents.

Ceranimic resonators were created using samples of Actual Examples 18, 19, and 20, which contained at least one type of Fe 203, and the time-dependent characteristics of the frequency constant Nt (Hzom) were determined. The results are shown in Figure 4. I got **.

In FIG. 4, curve a represents the case of Actual Example 13, and curve b represents the case of Actual Example 13.
j C and d are Actual Examples 18゜19 and 2, respectively.
The case of 0 is shown.

MnO, NiO. It can be seen that by adding Fe2O3, the customization over time becomes better.

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

It can be seen that the temperature percent property is improved by adding MnO, N i O, and Fe2O3.

Furthermore, it is shown that Qm is dramatically improved by adding subcomponents.

Figure 5 shows the composition of Actual Example 13 Reference Example 1 with a diameter of 50 cm.
The results of creating a disk vibrator of rrL and examining the change over time in ton δ, which indicates the mechanical strength after polarization, are shown.

In Figure 5, curve a curves actual example 13 and reference example 1.
Each case is shown below.

In the composition of Reference Example 1 in which Sr substitution was not performed, the ton δ increased rapidly and cracks occurred in the vibrator after 100 hours or more after polarization, whereas in the case of Example 13, no change in ton δ was observed and the result was due to Sr substitution. This shows that the change in mechanical strength over time has been improved.

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 due to temperature customization or aging is small, it can perform excellent functions as a variety of 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 applications Conventional piezoelectric materials have a dielectric constant of about 1000, which is too thick, 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, r is the frequency used, 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 comparable to that of conventional piezoelectric materials.

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 Ultrasonic Diagnostic Devices Ultrasonic transducer elements in probes for ultrasonic diagnostic devices are required to be large in size and thin as the frequency becomes higher.

It was difficult to make the element larger and thinner with conventional piezoelectric materials, but the material of the present invention has good sintering properties, so it is difficult to make the element larger and thinner (for example, with longer length). 50~
100 mw.

A width of 15 to 207n7IL1 and a thickness of 200 μm) 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, customization of frequency, temperature, and aging may be a problem, 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 a custom-made example of the oxide positive electric material according to the present invention. Figure 1 is a curve diagram of the relationship between polarization temperature and electromechanical coupling coefficient Kt (%), and Figure 2 is a curve diagram of the relationship between temperature and dielectric constant. Figure 3 is a relationship curve diagram between temperature and electromechanical coupling coefficient Kt (%), Figure 4
The figure shows a relationship curve between time and the frequency constant N t (Hz j rn ), FIG. 5 shows a relationship curve between time and ton δ (%), and FIG. 6 shows a ternary diagram showing the claims.

Claims (1)

[Claims] 1 (1-x)PbTiO3-xPb (M disease Sb”/
)03 Two-component basic composition (Me is either Zn or Sn), x = 0.01 to 0.15,
An oxide piezoelectric material characterized in that part of the Pb atoms is replaced by 1.0 to 20 at % of Sr. 2 (1-x)PbTi03-xPb(Me'/Sb
”/3) 03 Two-component basic composition (Me is Zn, Sn
), x=o, 01 to 0.15, and a part of the pb atoms is Sr at 1.0 to 20 atom%
An oxide piezoelectric material characterized in that it contains at least one of MnOtN10 and Fe2O3 as subcomponents in an amount of 0.05 to 2.0% by weight.