JPH02137771A - Piezoelectric material - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric material having improved piezoelectric constant, mechanical mass coefficient and mechanical strength by adding MnO2, SnO2, ZnO, etc., to a ceramic composition composed of PbTiO3, PbZrO3 and Pb(Mg1/3Nb2/3)O3 at specific ratios. CONSTITUTION:A ceramic composition is produced by compounding a 3-component system of formula I (a is mol% satisfying formula II; b is mol% satisfying formula III; c is mol% satisfy]ng formula IV; a+b+c=100; <=10 %atom of Pb atom is substituted with Sr, Ca and/or Ba). 100mol% of the obtained composition is mixed with 0.1-5mol% each of MnO2, SnO2 and ZnO, 0.05-2mol% of Bi2O3 and 0.1-5mol% of ZrO2 and/or Sb2O3 and the mixture is calcined, crushed, granulated, baked and sintered. A DC voltage is applied to the sintered material to obtain the objective piezoelectric material.

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention is applicable to materials such as piezoelectric actuators, ultrasonic motors, and ultrasonic vibrators that have a high mechanical quality factor and mechanical strength and utilize resonance displacement. This invention relates to a piezoelectric material suitable for use as a piezoelectric material.

(Prior art) Piezoelectric materials include lead zirconate titanate, Pb (Zr
Ti)Oz '171 compositions are well known. This compound is difficult to manufacture because it evaporates during firing because it contains lead, but it has great piezoelectricity, can be used at a high temperature, and can be replaced or added with a third component. There are advantages such as the ability to obtain 4512K rich in denaturation. In particular, PbTi0. -PbZrOi-Pb(J
Ig+/3Nb□z+)Oi three-component piezoelectric ceramics are easy to fire with little lead evaporation, and can have various piezoelectric properties by adding various additives to the main components. Since then, it has been used as a material for piezoelectric buzzers, frequency filters, piezoelectric ignition elements, ultrasonic vibrators, etc.

In recent years, with the development of mechatronics, responsiveness has improved,
The need for displacement elements that can be precisely controlled has increased, and attempts have been made to use displacement driving elements that utilize piezoelectric strain. For example, ultrasonic motors are an example of this. The ultrasonic motor is used to drive the robot's arm.
It is attracting attention as an alternative to conventional electromagnetic motors for driving lenses in autofocus cameras. This ultrasonic motor uses the vibration of the piezoelectric ceramic as the driving force for rotation, but in order to obtain better motor characteristics, the amplitude of the vibration of the piezoelectric ceramic must be large. In addition, in order to obtain such large vibrations, a large mechanical quality factor and piezoelectric constant are also required. Furthermore, in an ultrasonic motor, the piezoelectric ceramic vibrates while being bonded to an elastic body (usually a metal material), so the vibration of the porcelain is restrained by the elastic body and stress is applied to the porcelain. Therefore, piezoelectric ceramics for ultrasonic motors must also have mechanical strength that can withstand this stress.

The above explanation has mainly been given using piezoelectric ceramics for ultrasonic motors as an example, but there are many uses for piezoelectric ceramics that require similar characteristics. However, among the conventional materials, for example, Pb known from Japanese Patent Publication No. 42-11622)
(Mg+/Jbzzs)Ox PbTi0) Pb
The material obtained by adding Mn01 to Zr01 has a large mechanical quality factor, but the piezoelectric constant and mechanical strength are extremely small. In addition, the material obtained by adding Zr0z to the above three-component basic composition is disclosed in Japanese Patent Application Laid-open No. 154882/1982. Although this is known, the piezoelectric constant and mechanical quality factor are not sufficiently large.

(Problems to be Solved by the Invention) As mentioned above, the piezoelectric materials known so far have insufficient mechanical quality factor, piezoelectric constant, or mechanical strength, and are not suitable for use in ultrasonic motors, for example. Problems remain, such as not being able to produce large vibrations when used, making it impossible to expect improvements in motor characteristics, or being susceptible to breakage due to insufficient strength.

The object of the present invention is to provide a piezoelectric material that can be used in ultrasonic motors, etc., to obtain large vibrations, and that does not cause cracks or the like.
That is, the object is to provide a piezoelectric material whose mechanical quality factor, piezoelectric constant, and mechanical strength are all above a certain level.

(Means for solving problems) The gist of the present invention is the piezoelectric material described below.

'a PbTiO3b PbZrO3c Pb(Mg
+/5Nbzzs)Ox, the above a, b, and C satisfy the following ■~■2, and less than 10 atomic % of Pb atoms are substituted with one or more of S'', Ca, and Ba. Mn0t, Sn
0.1 to 5 mol% of O□ and ZnO, respectively, and B
0.05 to 2 mol% of 1□03, ZrO2 and sb
Piezoelectric material 1 containing 0.1 to 5 mol% of one or two of the following: 30≦a≦50 2.5≦b≦60 ・・・・・・■ 0≦c≦55 ・・・・・・■ However, a, b, c are mol%, a+b+c=100
It is.

(Function) The piezoelectric material of the present invention is produced by appropriately selecting the proportions of the oxides constituting the basic composition of the ternary system, that is, the values of a, b, and C, and by adding a portion of the Pb atoms. Sr.

Substituted with one or more of Ca, Ba, Mn0t, Snug
, ZnO, B1103, and one or two of z"0. and 5btOs in appropriate amounts.

The reason why the ratio of the oxides in the basic composition, that is, the values of a, b, and C, is determined as above is because the piezoelectric constant becomes small outside this range.

Sr
, Ca, and Ha in order to increase the piezoelectric constant. However, this amount of W is Pb
If the amount exceeds 10 atomic %, the piezoelectric constant becomes small.

Note that substituting 10 atomic % or less of Pb means that it may not be substituted at all.

With respect to 100 mol% of the above ceramic composition, MnO□, S
0.1 to 5 mol% of nO2 and ZnO, B110
．． 0.05 to 2 mol%2, and further ZrO2 and 5b2
0.1 to 5 mol% of one or two of 03 is added.

The reason why 0.1 to 5 mol% of MnO□ is added is to improve the mechanical quality factor of the piezoelectric material. This effect is
It appears from 0.1 mol%, and if it exceeds 5 mol%, both the mechanical quality factor and the piezoelectric constant deteriorate.

The addition of Snug, ZnO, and B1103 is necessary to increase the piezoelectric constant, but if only one or two of these are added, the effect may be small or the piezoelectric constant may be lower than when no additive is added. Therefore, add the three ingredients at the same time. The lower limit of the amount of addition of these components is the amount where the above effects are clearly manifested, and the upper limit is the value beyond which the piezoelectric constant decreases.

ZrO□ and sb,o refine the crystal grains of the piezoelectric material and increase its mechanical strength. If it is less than 0.1 mol%, the effect will be small, and if it exceeds 5 mol%, the piezoelectric constant will be reduced. Zr01 and 5btOs may be added alone or both.

The piezoelectric material of the present invention has the above composition, and the manufacturing method thereof is the same as that for conventional ceramic compositions of this type. That is, it can be manufactured by mixing oxides, carbonates, hydroxides, etc. of each element so as to have the above-mentioned composition, molding, and then sintering.

(Example) The basic composition is a PbTiOs b PbZrOs CPb(M
g + zJbzz) Os (Idanshi, a + b ten c
+=too), P boo ZrO! l Tioz + MgO+
NbxOs + CaC0= , Sr Co 31B
aCO+, 5n01. ZnO, BizO*, Mn0g,
5t) The raw materials of xoz were weighed so as to have the composition shown in Table 1, and thoroughly mixed using a ball mill. The obtained mixed powder was calcined at 900 to 1000° C. for about 2 hours, and the calcined product was sufficiently ground and mixed in a ball mill again, and then an organic binder was mixed and granulated. Approximately 1'> of this granulated powder
The molded material was molded into a diameter of 20 mm and a thickness of 2 mm under a pressure of /C-, and fired at a temperature of 1200-1300 DEG C. for about 2 hours.

Further, silver electrodes were baked on both sides of the obtained disc-shaped sintered body, and a DC voltage of 2 kV/mIm was applied to the sintered body at 100'C to perform a decentralization process.

The piezoelectric properties of the porcelain thus obtained are shown in Table 1. In the table, d41 is a piezoelectric constant, Qm is a mechanical quality factor, and σ is a bending strength.

Trial t4Nal~12 was PbTiOs, PbZr0=,
and Pb(Mg+zsNbtzz)Oz, changes in characteristics due to differences in the ratios, ie, a, b, and c, are observed. In the case where these values are outside the range defined by the present invention (comparative example), d31 is extremely small.

Samples N (113 to 17 are examples in which the amount of Pb substitution by Ca, Sr, Ba is changed.'R substitution amount is 10 at%
When it exceeds d31 and Q+w become small like Nα13. Although Nα15 does not have Pb atoms substituted, it is an example in which a product having a large piezoelectric constant, mechanical quality factor, and strength can be obtained even without substitution.
Substitution with Ca or 5rSBa is effective, whether it is a negative element or a combination of three or more elements, as long as the total amount is 10 at % or less of Pb atoms.

Sample N (Li2 to 35 are Snug, ZnO, Bi2O
This is an example in which the amount of No. 3 added was changed. It can be seen that when these three components are added within the range defined by the present invention, the effect of increasing dffl is remarkable. One or two of these ingredients
When only the ingredients are added (No, 18.23.28.3
3 to 35) have no effect of increasing d31, and when the amount added is out of the range defined by the present invention (trial $4Nα1
9, 22.24, 27.29.32) also d, l, Om
decreases.

Samples N (136 to 40 are examples in which the amount of MnO□ added was changed.

Sample Nα36 with an added amount of Mn01 of less than 0.1 mol%,
No. 37 had no improvement effect on low, and conversely, in sample Nα40, in which more than 5 mol% was added, Qm decreased and d
, 1 are also smaller.

Samples 41 to 49 contained ZrO□ and Sb, 0. This is an example of changing the amount of addition. Products with appropriate amounts of one or two of these ingredients added are additive-free products (Testine 4Nα41).
) has higher mechanical strength (σ). However, if the amount added is less than 0.1 mol%, the effect of improving σ is small (sample Nα42.46). On the other hand, the amount added is 5 mol%
If it exceeds , d31 and Qm deteriorate as in NCL45.49.

(Hereinafter, blank space) (Effects of the invention) As shown in the examples, the piezoelectric material of the present invention has a high piezoelectric constant, high mechanical mass coefficient, and high mechanical strength, so it can obtain large vibrations and It can be widely used as a material for sonic motors, ultrasonic vibrators, etc.

Claims (1)

[Claims] aPbTiO_3-bPbZrO_3-cPb(Mg_
1_/_3Nb_2_/_3)O_3, the above a, b, and c satisfy the following formulas (1) to (3), and P
MnO_2, SnO_2, and ZnO were each added to 100 mol% of a ceramic composition in which 10 at% or less of b atoms were substituted with one or more of Sr, Ca, and Ba.
．． 1 to 5 mol%, 0.05 to 2 mol% of Bi_2O_3, and one or two of ZrO_2 and Sb_2O_3.
A piezoelectric material containing 0.1 to 5 mol% of seeds. 30≦a≦50 (1) 2.5≦b≦60 (2) 10≦c≦55 (3) However, a, b, c is mol%, a+b+c=100
It is.