JPS6023513B2 - oxide piezoelectric material - Google Patents

Description

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

For more details, see (PbHCaa) [(Me,'3NQ/
3) xTi, -x] Basic composition of 03 system (however, Me is Nj
, Co) and 0.01SxSO. 10,
0.05 myaSO. 35 composition range of oxide piezoelectric materials. Furthermore, as subcomponents Mn0, Ni○ and F
At least one type of e203 in an amount of 0.05 to 2. % by weight of an oxide piezoelectric material.

Recently, various ultrasonic transducers and surface wave elements using oxide piezoelectric materials have been developed.

For such uses, PbTi03-PbZr03 binary system and PbTi03-PbZr03-Pb(Mg,/3
Materials in which additives such as Cr2Q, Mn02, and Ni○ are added to the NQ/3)03 ternary system have also been developed, but these piezoelectric materials have a large dielectric constant of 350 to 2000, making them difficult to use in high frequency ranges. is not suitable. In addition, when this material is used at high frequencies, the coupling coefficient Kt in the thickness direction and the coupling coefficient Kp in the spreading direction are approximately the same value, so spurious noise is likely to occur due to overtone of the coupling coefficient Kp in the spreading direction. existed. For this reason, it has been considered desirable for the Kt/Kp ratio to be as large as possible in high frequency applications. In addition, PTi03-based materials have been reported that have anisotropy in the coupling coefficient in which the values of the coupling coefficient Kt in the thickness direction and the coupling coefficient Kp in the spreading direction are significantly different. It was not possible to obtain a large-sized sintered body, and the polarization conditions were extremely severe, such as an applied voltage of 60 KV/200 qo, making it easy to cause discharge breakdown and making it difficult to obtain a large-sized vibrator.

Furthermore, in the conventional PbTi03 material, the coupling coefficient Kt in the thickness direction is 40 to 48%, and the coupling coefficient Kp in the spreading direction.
is 8% or more, so the ratio of coupling coefficients Kt/Kp is 4~
6 is the limit, and spurious noise due to overtone of the coupling coefficient Kp in the spreading direction cannot be ignored.

Furthermore, when trying to apply the related PbTi03-based material as a surface wave element, it is impossible to obtain a material with a dielectric constant of 200 or less, which is 4 mm, and a composition with a surface wave temperature coefficient of 2 pm or less. Ta.

Furthermore, the temperature coefficients of these materials all tend to be negative, and it has not been possible to improve the temperature coefficients by using ferrite coils or the like. The purpose of the present invention is to solve the above problems, and the coupling coefficient Kt in the thickness direction is as large as 50% or more, and the coupling coefficient Kp in the spreading direction is 3 to 5%, that is, Kt/Kp is 10 to 19. It is a material with a low dielectric constant of 300 or less, and is easy to burn, so it has a dielectric constant of 500 or less.
A large oscillator larger than the size of the PbTi03 oscillator can be obtained.
The object of the present invention is to provide an oxide piezoelectric material that can be polarized much more easily than other materials.

Furthermore, in the material of the present invention, it is also possible to obtain a material with an excellent surface wave temperature coefficient.

The present invention is based on (Pq~Caa) [(Me,/3NQ/3)x
In the general formula of Ti,1]03 (where Me is either Ni or Co), 0.05Sa, 0.35,0.
It has a composition of 0.01S x 0.10, and if necessary, at least one of Mn○, Nj○, and Fe203 is added as a subcomponent from 0.05 to 2.0. This is an oxide piezoelectric material containing an additive amount of .

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

For example, Pb0, Ti02, CaC03, MnC03,
Raw material oxides such as Ni○, Fe203Nb2Q, and COO are accurately weighed out in predetermined proportions and mixed well using a ball mill or the like. 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. Next, the mixture is preliminarily calcined at a temperature of, for example, about 600 to 900 qo, and is further pulverized using a ball mill or the like to obtain a prepared powder.

Thereafter, water or a binder such as polyvinyl alcohol is added to the prepared powder, and the powder is press-molded at a pressure of about 0.5 to about 100 ml, followed by firing at a temperature of about 1,100 to 1,200 q0. During this firing, there is a risk that a part of Pb0, which is one of the components, may evaporate and dissipate, so the firing is carried out in a closed furnace, and at the maximum temperature, the retention is generally 0.5~
About 3 hours is sufficient. Further, the present invention will be explained in detail.

First, (Pq-aCaa) [(Me, /3Nb2/3)x
TiM]03 basic composition (Me is either Ni or Co) with 0.05 myaSO. The reason for limiting it to 35 is that the value of Kp is 5 whether a<0.05 or a>0.35.
% or more, and the ratio of Kt to Kp becomes less than 10, which increases the occurrence of spurious signals.

Further, if a>0.35, the dielectric constant value becomes 300 or more, which is particularly disadvantageous for application as a surface wave element material or high frequency application. The reason for limiting X to 0.01 to 0.10 is that when X < 0.01, Pb (Mel/state b2'3
)03 (however, Me is one of Ni and Co) does not exhibit the effect, and when X>0.10, Kp becomes large and the ratio of Kt to Kp becomes less than 10.

Further, the additive content of any one of MN0, Ni○, and Fe3 is 0.05 to 2. The weight percent was limited to 0.05.
If the weight percentage is too low, the remarkable effects of these subcomponents on improving the sinterability and polarization properties of PbWi03 porcelain cannot be obtained.2. This is because if the amount is more than 1% by weight, the competitiveness of the porcelain may deteriorate.

Thus, according to the present invention, the following effects can be obtained.

First, in conventional PZT materials and three-component materials, the coupling coefficient Kt in the thickness direction and the coupling coefficient Kp in the spreading direction are almost the same. However, in the material of the present invention, although the coupling coefficient in the thickness direction shows a large value of 50 or more, the coupling coefficient KP in the spreading direction is as small as 3 to 5%. Because of this value, spurious waves at high frequencies are small, which is advantageous for use. Second, by substituting a part of Pb with Ca, and by partially solidifying Pb(Me,/3Nb2/3)03, which has a low firing temperature, we lowered the firing temperature, which led to the beginning of PbTiQ-based materials. This makes it possible to obtain fine porcelain with a small number of bores, which can be used as a material for surface wave substrates.

Furthermore, with conventional PbTi03-based materials, the coupling coefficient K is sufficient unless an electric field of 6 V/arc is applied at a high temperature of 20 P0.
Since it is not possible to extract t, discharge breakdown is likely to occur during polarization, making it difficult to obtain a large oscillator. In the material of the present invention, since a part of Pb is replaced with Ca, polarization is facilitated, and a sufficient coupling coefficient Kt can be obtained under polarization conditions of 10 P0, 30 to 5 V/G. Almost no discharge damage occurs, and large oscillators can be produced stably.

-Thirdly, by adding at least one of M, Nio, and Fe203, it is possible to further improve the quenching properties, polarization characteristics, and resonant frequency characteristics over time.

Fourthly, in the material system of the present invention, it is also possible to obtain a material with a small temperature coefficient of the resonance frequency of the fundamental wave. Conventional PbT
In the case of iQ-based materials, the temperature coefficient of resonance frequency in a region where the PbTi03 component is 6 ol % or more is all considered to be negative. Moreover, the value remains -2 even if the additive solid solution component is added.
Although it was thought to be impossible to use materials under Misaki PM, by substituting 10 to 15 hol% of Ca for part of the Pb, the temperature coefficient could be reversed, and it was also possible to obtain a material with a temperature coefficient within 20 ppm. Serve. This phenomenon is caused by Mg, Sr, Ba
This phenomenon is unique to Ca, and is not observed with substitutions such as .

Next, examples of the present invention will be described.

The bonded sample was polished to a size of 200 x 0.5, and electrodes were baked on both sides and polarized under the conditions of 100 qo and 50 KV/g, followed by PrM. IRE. Vol. 137 (1949) 1
The piezoelectric properties were each measured by the standard circuit method shown in 378-1395.

The results of these measurements are shown in Table 1 along with the composition ratios of the brick bodies. In addition, in Table 1, F. T is the firing temperature (
00), D is the specific gravity (measured at 23qo), and D is the specific gravity (measured at 23qo).
Kt is the coupling coefficient in the thickness direction (measured at IKHz 23℃).
%), Kp is the coupling coefficient (%) in the spreading direction, Kt/K
p indicates the ratio of coupling coefficients.

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

In FIG. 1, curve a shows the case of Example 15, and curve b shows the case of Reference Example 1. Embodiments of the present invention are based on PbTi
It can be seen that a sufficient coupling coefficient Kt can be obtained even at low temperatures compared to 03 series shellac, and polarization is easier. Next, among these samples, Examples 9, 1011, 12,
When the changes in precision coefficients Kt and Kp and the coupling coefficient ratio Kt/Kp of the samples of Reference Examples 1, 2, 3, and 4 were measured for each 1-pack IL1i1, the results shown in FIG. 2 were obtained.

In Figure 2, samples a, b, c, d, e, f, g, h'
Examples 9, 10, 11, 12, 1-pack 141F 16, samples i, i, k, 1, and reference examples 1, 2, 3, and 4 are shown, respectively. As is clear from FIG. 2, 0.05 myaSO. 35
In the range, the coupling coefficient Kt shows a value of 50% or more, but the coupling coefficient Kp is as small as 3 to 5%, and the coupling coefficient ratio Kt/Kp reaches 10 to 19.

Figure 3 shows CaTi03mo in the case of x=0.05.
The relationship between l% and dielectric constant is shown.

The power transfer rate shows a small value of 300 or less when a<0.35. Figure 4 shows CaTj03m in the case of x=0.05.
ol% and the resonance frequency temperature coefficient of the fundamental wave are shown.

In a composition range of 10 to 15 mol of CaTi03, a material with a temperature coefficient of 20 ppm or less can be obtained. In this way, a material with a dielectric constant of 200 or less and an excellent temperature coefficient can be obtained.

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

1. Application in high frequency applications Conventional piezoelectric materials have a disadvantage in that they are not suitable for use in high frequency ranges because they have a coefficient of conductivity of 100 degrees, which is too large.

Generally, impedance Z is Z=d/(2 bamboo f・go・s)
(Here, d·s is the thickness and cross-sectional area of the sample, f is the frequency used, and d is the dielectric constant.) Therefore, d needs to be made thinner in inverse proportion to f. In the end, Z's 1/(f21
s), but as f becomes higher, Z becomes effective as a square and rapidly decreases. It is necessary to make the s cage small for Z alignment, but since s has a limit in processing, it is advantageous to make the cage small. The piezoelectric material of the present invention has a dielectric constant of 180 to 30 degrees, which is 1/3 to 1 compared to conventional materials.
/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. In addition, the coupling coefficient ratio Kt/Kp is 10 to 19
Since this is large, the influence of spurious effects due to overtone of Kp is small, which is practically advantageous when producing a vibrator.

2 Probe for Linear Scan Type Ultrasonic Diagnostic Devices The sound wave conversion elements in probes for ultrasonic diagnostic devices are 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 PbTi03-based piezoelectric materials, but with the material of the present invention, it is difficult to make the element larger and thinner.
Large and thin plates with excellent mechanical strength due to good properties (for example, length 50-10 mm, width 15-2 mm, thickness 200 mm)
m) can be easily realized. 3 Application as a substrate for surface waves Recently, surface wave filters using oxide piezoelectric materials have been developed, but the characteristics particularly required for piezoelectric materials for surface waves are a small temperature coefficient of surface waves (2 pm). The following is preferable)
That's a thing.

Furthermore, when using a material with a large dielectric constant, the impedance of the surface acoustic wave filter decreases by 4, causing a problem of mismatching with an external circuit. Therefore, the value of dielectric constant should be as small as possible,
It is said to be more desirable. For these requirements, Pb
TiQ-PbZrQ material (PZT material) and PbTi0
Attempts were made to use 3-Pb(Sn,'2Sb,/2)03-based materials (ternary materials) for the 3C-P side, but these materials have low dielectric constants in the region where the temperature coefficient is 2 oppm or less. was 350 to 1000, and had the disadvantage that the yield rate was too high for use as a surface wave filter material. Furthermore, these materials had drawbacks in terms of stability due to large changes in resonance frequency over time.

By using the material of the present invention, it is also possible to obtain an oxide piezoelectric material suitable for surface wave applications, which has a dielectric constant of 200 or less, a temperature coefficient of 4.0 mm resonance frequency within ±20 ppm, and excellent aging characteristics.

As described above, it can be seen that the use of the piezoelectric material of the present invention is useful for applications that were previously impossible.

[Brief explanation of drawings]

The drawings show characteristic examples of the oxide piezoelectric material according to the present invention. Fig. 1 is a graph showing the relationship between polarization temperature and electromechanical coupling coefficient Kt, and Fig. 2 is a graph showing the relationship between the mol% of CaTi03 and the coupling coefficient Kt (
%), Kp (%), and their ratio. Figure 3 is a diagram showing the relationship between mol% of CaTi03 and yield rate. Figure 4 is a diagram showing the relationship between mol% of CaTi03 and the temperature coefficient of resonance frequency. , and FIG. 5 each show a ternary diagram showing the scope of the claims. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 (Pb_1_-_aCa_a) [Me_1/_3N
b_2/_3)_xTi_1_-_x] O_3 basic composition (Me is either Ni or Co) x = 0
．． 01 to 0.10, and a=0.05 to 0.35. 2 MnO, NiO and Fe_2O_3 as subcomponents
The oxide piezoelectric material according to claim 1, characterized in that the oxide piezoelectric material contains 0.05 to 2.0% by weight of at least one of the following.