JPS5940314B2 - oxide piezoelectric material - Google Patents

Description

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

More specifically, (1-x)PbTi03-xPb(M
el/2, W 赳) 03 In the two-component basic composition, x=0.
01 to 0.20, and some of the Pb atoms are 0 with Br.
．． PbSr [(Mel/2W included) Ti)O substituted with 5 to 20 atom %. (wherein, Me is at least one kind of MnZn)-based 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. 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, vibration meters, accelerometers, and the like.

For such uses, an improved PbTi03-PbZr03 binary oxide piezoelectric material has been developed. For example, attempts have been made to improve the piezoelectric properties by adding additives such as Bi2O3, Cr2O3, and Mno332no to the PbTi03-PbZr03 binary system. In addition, PbTi03-PbZr03-Pb (Mg%
Nb2/3)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 about 1000, which makes it unsuitable for application in a high frequency range. On the other hand, the dielectric constant is 150~
PbTiO3-based materials with a small value of 250°C 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 20°C or more, and the polarization conditions are also limited to 200°C.
Since the applied voltage was very strict at 6 OKV/cm, there were drawbacks such as a low yield of the product.

The purpose of the present invention is to solve the above problems, have a high Curie temperature, can be used stably even at high temperatures of 300°C or higher, is suitable for applications in the high frequency range of several MH2 or higher, and is compatible with conventional PbTi03-based piezoelectric materials. The object of the present invention is to provide a PbTiO3-based oxide piezoelectric material whose polarization operation is much easier than that of the present invention. That is, the oxide piezoelectric material according to the present invention contains Pb
TiO3-Pb(Me-W-)Os binary system (however, Me
is at least one of Mn and Zn) in which a part of Pb is replaced with Br, and if necessary, MnO,
Reliability is further improved by adding a small amount of at least one oxide of NiO and Fe2O3.

More specifically, (1-x)PbTiO3-XPb(M
eWl/2. )03 Two-component basic composition (Me, Zn
(at least one type of), x=0, 01 to 0.20
And some of the Pb atoms are replaced with Sr by 0.5 to 2.0 atomic %.

That is, if expressed as a general formula, Pbl-Asra [(Mel
/2W? )XTil? x) 03 (in the formula, Me is Mn, Zn
x=0.01~
0.20, and a=0.005 to 0.20. The oxide piezoelectric material further contains 0.05 to 2.0% by weight of at least one of MnO, NiO, and Fe2O3 as a subcomponent, if necessary. Such an oxide piezoelectric material of the present invention can generally be easily manufactured by a powder metallurgy method.

For example, PbO, TiO2, SrO, WO3NiO, F
Accurately weigh raw material oxides such as e2O3 and MeO (Me is at least one of Mn and Zn) to a predetermined ratio,
These are thoroughly mixed using a ball mill or the like. In addition,
The raw materials used in this case may be compounds that are converted into oxides by heating, such as hydroxides, carbonates, and oxalates. 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 this prepared powder and blended.
After pressure molding at a pressure of about 0.5 to 2t0n/Cd,
It is fired at a temperature of about 1100 to 1200°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 performed 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, (1-x)PbT
In the basic composition of iO3-XPb(Me?w?)03 (Me is at least one of Mn and Zn), x=0
．． The reason for limiting the range to 0.01 to 0.20 is that when X<0.01, sinterability is poor and dense porcelain cannot be obtained, and when This is because it cannot be stably used at high temperatures and has a dielectric constant of 250 or more, making it difficult to use in a high frequency range.

Next, the reason why the amount of Pb substitution by Sr was limited to 0.5 to 20 at.% is that if it is less than 0.5 at.%, PbTiO
This is because the effect of facilitating the polarization of the 3-type piezoelectric material and the sintering of porcelain is hardly achieved, and 20
This is because if the amount is more than atomic %, the temperature will be lower than 350° C., making it difficult to use at high temperatures.

Furthermore, MnO, NiO and Ve2O 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 mainly because the sinterability of the ceramic deteriorates.

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

First, PbTiO3 was considered to be a promising piezoelectric material due to its Kiyuri temperature of around 500°C, but it was not practical due to difficulties in sintering.
Since e3/2Wν2)03 (Me is at least one of Mn and Zn) is used as one of the components, and a part of Pb is replaced with Sr, it acts as a mineralizer. This makes sintering easier.

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, in PbTiO3 ceramics, it is important to perform firing to suppress grain growth.
In the present invention, by substituting some of the Pb atoms with Sr, grain growth can be suppressed to 1 to 3 μm or less, and sintering can be facilitated.

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

In other words, conventional PbTiO3 ceramics have polarization conditions of 60 to 80 KV/C at a high temperature of 180 to 200°C.
m, whereas the piezoelectric material of the present invention requires a voltage of 80 to 1
Sufficient polarization can be achieved under relaxed conditions of 00° C. and 40 to 60 KV/Cm. Thirdly, MnO, NiO
By adding and containing at least one of Fe2O3 and Fe2O3, the temperature characteristics, aging characteristics, and mechanical quality coefficient can be significantly improved compared to conventional PbTiO3 ceramics.
Large-sized sintered bodies such as 0tx20Wx1t can be easily manufactured.

Next, examples of the present invention will be described.

The sintered sample was polished to 20φ x 1.0WrLt, and silver electrodes were baked on both sides and polarized at 100°C and 60KY/Cm, then PrOc, IREVOl, l37C54
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 and T are the firing temperature (C), D is the specific gravity (measured at 23°C), and ε is the dielectric constant (
1Hz, 23℃), Kt is the electromechanical coupling coefficient (measured at 1Hz, 23℃)
a), Qm represents the mechanical quality factor, and Tc represents the temperature of the yoke. Among these samples, Example 7 and Reference Example 2
When the value of the electromechanical coupling coefficient Kt depending on the polarization temperature was measured for the sample, the results shown in FIG. 1 were obtained. In FIG. 1, curve a shows the case of Example 7, and curve b 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 PbTiO3 ceramics. Next, changes in dielectric constant due to temperature were measured for the samples of Examples 1 and 13 and Reference Example 4 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 13, and curve c shows the case of Example 4.
It can be seen that Examples 1 (curve a) and 13 (curve b) of the present invention have a high temperature and can be used at temperatures of 300° C. or higher. Furthermore, when we measured the change in electromechanical coupling coefficient Kt with respect to temperature for the same sample, we obtained the results shown in Figure 3. In FIG. 3, curve a represents Example 1.
Curve b shows the case of Example 13, and curve c shows the case of Reference Example 4.

According to this figure, in both Examples 1 and 13 of the present invention, Kt is almost constant over a wide temperature range from room temperature to 400° C. 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 9 and Example 19, which had the same basic composition but added and contained at least one of MnO, NiO, and Fe2O3 as subcomponents,
Ceramic resonators were made using samples Nos. 20 and 21, and the time-dependent characteristics of the frequency constant Nt (Hz.m) were determined. In FIG. 4, curve a is for Example 9, curves B and c are
and d indicate the cases of Examples 19, 20 and 21, respectively.

It can be seen that the addition of MnO and NiO improves the aging characteristics. Furthermore, the temperature characteristics and aging characteristics of the resonant frequency of the ceramic resonator of the same sample as above were measured, and the results shown in Table 2 were obtained. M
It can be seen that the addition of nO and NiO improves the temperature characteristics and aging characteristics. In addition, although the samples of Examples 19 and 20 have compositions containing Fe2O3, they exhibit good characteristics similar to MnO, exhibiting characteristics of the added content, and showing the effects of the added content. Figure 5 shows Example 8
Composition of VC. Mechanical quality factor Qm when MnO is added
shows the change in In FIG. 5, a indicates the composition of Example 8,
B, c, d, e, f, g, h, i are respectively Example 2
5, 26, 27, 28, 29, 30, 31, 32, and i indicates Reference Example 7. This shows that Qm is dramatically improved by adding the subcomponents. 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 perform 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'C 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 powerful 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 00°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 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, Z(X)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 also has a processing limit, it is advantageous to make ε small. The piezoelectric material of the present invention has a dielectric constant ε of about 180 to 300, which is lower than 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 ultrasound diagnostic equipment The sound wave conversion element in the probe for ultrasound diagnostic equipment is required to be larger in size and thinner 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 sinterability, so it can be made large and thin with excellent mechanical strength (for example, 50-1
00Trm, width 15-20Tm, thickness 200μm) can be 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.

Note that when used as a high frequency filter or resonator, the temperature characteristics and aging characteristics of the frequency become a problem, but since the rate of change in these characteristics is also small, it can be satisfactorily used for practical use.

[Brief explanation of drawings]

The drawings show characteristic examples of the oxide piezoelectric material according to the present invention, and FIG. 1 is a relationship curve between polarization temperature and electromechanical coupling coefficient Kt(1), FIG. 2 is a relationship curve between temperature and dielectric constant, and FIG. Figure 3 is a relationship curve between temperature and electromechanical coupling coefficient Kt(1), Figure 4 is a relationship curve between time and frequency constant Nt (Hz.m), and Figure 5 is a relationship curve between additive amount and mechanical quality factor Qm. relationship curve diagram,
Figure 6 shows a ternary genealogy showing the composition.

Claims (1)

[Claims] 1 (1-x)PbTiO_3-xPb(Me1/2W
1/2) O_3 two-component basic composition (Me=Mn, Z
n), x = 0.01 to 0.2
0, and a part of Pb atoms are replaced with 0.5 to 20 at. % of Sr. 2 MnO, NiO and Fe_2O_3 as subcomponents
The oxide piezoelectric material according to claim 1, wherein the oxide piezoelectric material contains at least one of the following in an amount of 0.05 to 2.0% by weight.