JPS6022836B2 - oxide piezoelectric material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to oxide piezoelectric materials, particularly (1-a) PbT
i03-. This invention relates to an improvement in an oxide piezoelectric material having a basic two-component composition of Pb(Col'2WI/2)03.

As is well known, Shoden 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, an improved PbTi03-PbZr03 binary oxide piezoelectric material has been developed. For example, Bi20 is added to the three-component system on the PbTi03-P side
3. Attempts have been made to improve the piezoelectric properties by adding additives such as Cr203, Mh02, and Zn○. Also P
bTi03-occupation 3-Pb (M increases).Three ternary music materials have also been developed.

However, these piezoelectric materials have a strong electrostatic Curie temperature of about 300 qo, and cannot be used at temperatures higher than that. Further, the dielectric constant of the piezoelectric material is 100, making it unsuitable for application in a high frequency range. On the other hand, the dielectric constant is 150
PbTi03-based materials with a small value of ~250 have been reported, but due to cracks that occur after solidification, it is not possible to obtain large composite bodies with a diameter of 2 or more, and the polarization conditions are also 200.
Since the applied voltage was extremely severe at 60 KV/arc at .degree. C., there were drawbacks such as a low yield of the product. Further, in the conventional PbTiQ-based oxide piezoelectric material, the mechanical strength rapidly decreases over time and the material becomes easily disintegrated, resulting in a lack of reliability.
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 30030 or higher, is suitable for applications in the high frequency range of several MHz or higher, and is more effective than conventional PbTi03-based piezoelectric materials. The present invention provides an oxide piezoelectric material that is much easier to polarize and has excellent aging characteristics.

The present invention is (PbraMea) [(COl/2WI/2)
xTi, -X]03, and (Pq-aMea)0/[(Col/2WI/2)xT
i, ~]02 (hereinafter referred to as A/B) as 0. Spots<A/B<
It is an oxide piezoelectric material with a concentration of 0.05 to 2.0, and at least one of Mh○, Ni○, and Fe2Q as a subcomponent. Reliability is improved by including the content in a weight percent of .

Such an oxide piezoelectric material of the present invention can generally be easily manufactured by a powder metallurgy method. For example, Pb0, Ti02, Coo, W03 and Me0 (M
e is the base material, Sr or Ca) and other raw material oxides are accurately weighed out in a predetermined ratio, and mixed using a ball mill or the like. Note that the raw material used at this time may be a compound that converts into an oxide upon heating, such as a hydroxide, carbonate, or oxalate. Then, the mixture is heated to, for example, 600 to
It is pre-calcined at a temperature of about 900 oo, and is further ground into a prepared powder using a ball mill or the like.

After that, water or a binder such as polyvinyl alcohol is added to the prepared powder, and the powder is pressure-molded at a pressure of 0.5 to 1000 yen, followed by firing at a temperature of 1000 to 1250 yen. . During this firing, there is a risk that the negative part of Pb○, which is one of the components, may evaporate and oxidize, so the firing is carried out in a closed furnace, and the maximum temperature is generally 0.5~
About 3 hours is sufficient. Furthermore, the reasons for the limitations of the present invention will be explained in detail.

First, (Pq-aMea) [(Col'2WI/2)x
In the basic composition of Ti, -x]03, x=0.01~
The reason why it is limited to 0.20 is that when x<0.01, the firing resistance is poor and delicate porcelain cannot be obtained, and when x>0.20, the Curie temperature decreases to below 400℃, resulting in a high temperature of 30°C or higher. This is because, in addition to being unable to be used stably, the dielectric constant is 250 or more, making it difficult to use in a high frequency range. Next M
The reason why the amount of substitution of Pb by at least one of Sr and Ca, indicated as e, is limited to 0.5 to 20 atomic % is that less than 0.5 atomic % facilitates the polarization of the PbTi03-based piezoelectric material; Moreover, the effect of substitution to facilitate sintering of porcelain is hardly manifested, and if the amount is more than 20 at %, the Curie temperature becomes 350 pm or lower, making it difficult to use at high temperatures.

Furthermore, Nm○, Ni○ and Fe2Q as subcomponents
The added content of at least one of the following is 0.05 to 2. % by weight is less than 0.05% by weight
It is said to improve the temperature characteristics and aging characteristics of bTi03-based ceramics.

2. It does not show the effects of these subcomponents. This is because if the amount is more than 2% by weight, the dawn streaking properties of the ceramic will deteriorate. Also (P
b-aMea)0/[(Col/2WI/2)xTi,
★]02 is limited to 0.98 minus A/B < 1.000 because if the A/B ratio is less than 0.980, the crystallization property is poor and sufficient density cannot be obtained, and it will collapse within a few days after the crystallization. It's for a reason.

Furthermore, if the A/B ratio is 1.000 or more, an excessive current flows during polarization, making it impossible to obtain sufficient coupling coefficients Kt and Kp (%). Furthermore, after polarization, a rapid increase in n8 (%) occurs within a few weeks, and eventually collapse occurs. A/
B ratio is 0. By setting the absorption coefficient to 0 to 1.000, it is possible to obtain ceramics that have excellent silkiness, easy polarization, and excellent aging properties. For this reason, compared to conventional PbTi03 ceramics, tan
6 can be significantly improved. Thus, the following effects can be obtained by the present invention.

First, PbTi03 had a Curie temperature of around 50,030 and was considered to be a promising piezoelectric material, but it was not practical due to the difficulty in bonding.
(Col/2WI/2)03 is used as one of the components, and some of the Pb is replaced with Ba, Br, Ca, etc., so these act as mineralizers and cause crystallization. This makes it easier.

This facilitation of competitive bonding ultimately lowers the adjacency temperature, suppresses the evaporation and scattering of Pbo, which forms part of the composition, and ultimately makes it easier to obtain a dense piezoelectric material. . Second, by substituting a portion of Pb with at least one of Bc, Sr, and Ca, it is possible to easily polarize PbTi03 ceramic, which has been difficult to polarize.

In other words, while the conventional PbTiQ ceramic requires a voltage of 60 to 8 V/ga at a high temperature of 180 to 200 qo as polarization conditions, the piezoelectric material of the present invention requires a voltage of 80 to 10
Sufficient polarization can be achieved under relaxed conditions of 0qo, 40 to 6 V/g. Thirdly, by adding at least one of Mn○, Nj0 and Fe203, the temperature characteristics and aging characteristics can be improved compared to conventional PbTi03 ceramics.

Fourthly, by adjusting the A/B ratio, the aging characteristics over a long period of time after polarization are significantly improved.

Next, examples of the present invention will be described. The scaled sample was sized at 200×1. After polishing the ribs and baking silver electrodes on both sides and polarizing them under the conditions of 100 qo and 6 plate V/skin, Pr
ratio. IRE Vol. 137 ('49) 1378-139
The Shoelectric characteristics were measured using the standard circuit method shown in No. 5 and the like.

The results of these measurements are shown in Table 1 along with the composition ratios of these whisker bodies. In addition, in Table 1, the A/B ratio is (Pb
, -aMea)○ and [(Col/2WI/2)xTi,
] 02, the ratio with F. T is the firing temperature (℃), D is the specific gravity (measured at 23℃), and is the dielectric constant (IKHz/S, 2y
o), Kt is the electromechanical coupling coefficient (%), Qm
represents the mechanical quality factor, and Tc represents the Curie temperature. Further, the tan6 change rate (%) is determined from the following equation using the value of n6 immediately after polarization in IK phase and the value of n6 after 1 pi (rib). tan 6 rate of change (
%) [T fox 6 autumn o after lo thing)] - [T blood 6 squad immediately after polarization.

) Immediately after polarization t blood 6 fall o) Example 80 in these samples
Figure 1 shows the density when the compositional starch ratio is changed.

The ratio is 0. While it shows a sufficient density of compaction at mottling or above, the density of compaction is not sufficient below 0.9 milk, and after a few days it spontaneously disintegrates and turns into powder. Based on these results, A/
B ratio is 0. It was confirmed that ceramics with sufficient strength could not be obtained below the total strength. Further, FIG. 2 shows the results of measuring the values of electromechanical coupling coefficients Kt and Kp after polarization for reference samples in which the A/B ratio was changed using the composition system of Example 5 in a sufficiently phosphorized sample.

When the A/B ratio is in the range of 0.98<A/B<1.00, sufficient Kt and Kp are shown, but when the A/B ratio is 1.01 or more, K rapidly decreases and Kp decreases. There is. FIG. 3 shows the tan6 (IK) and mechanical quality factor Qm of samples having the composition system of Example 5 with different A/B ratios. tan6 has an A/B ratio of 0. The lowest value is shown for the composition of Job<A/B<1.00. Qm', A/B ratio is 0.98<A/B 1.00
Although it is 1500 or more, it rapidly decreases as the A/B ratio increases. Figure 4 shows Examples 5 and 6 Reference Example 7
, 8 shows the rising characteristics of the thread n6. In the figure, curve a shows Example 5, curve b shows Example 6, and curves c and d show Reference Examples 7 and 8, respectively. In the sample with A/B ratio of 0.98<A/B<1.00, tan6 hardly changes, whereas A
In the samples of Reference Examples 7 and 8 where the /B ratio was 1.01 or more, tan6 increased rapidly, indicating that the mechanical strength decreased with time. As is clear from the above examples, the piezoelectric material according to the present invention can be used in high temperature and high frequency ranges, and is an extremely reliable material.

[Brief explanation of the drawing]

The drawings show an example of the characteristics of the oxide piezoelectric material according to the present invention.
The figure is a relationship curve diagram showing the A/B ratio and electromechanical coupling coefficient, Figure 3 is a relationship curve diagram showing the A/B ratio, thread n6, and mechanical quality factor Qm, and Figure 4 is the temporal characteristic of spring n6. It is a relationship curve diagram showing. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 (Pb_1_-_aMe_a) [(CO1/2W1
/2)xTi_1−_x]O_3▲There are mathematical formulas, chemical formulas, tables, etc.▼ and has the composition of (Pb_1_−_aMe_a)O/[(Co1/2W1
/2)xTi_1_-_x]O_2 (hereinafter referred to as A/B, an oxide piezoelectric material characterized in that 0.98<A/B<1.00. as Mn
At least one of O, NiO and Fe_2O_3 is 0
．． An oxide piezoelectric material characterized by containing 05 to 2.0% by weight.