JPH02137761A - Piezoelectric material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention has a high mechanical quality factor and mechanical strength, and can be used as a material for piezoelectric actuators, ultrasonic motors, ultrasonic vibrators, etc. that utilize resonance displacement. Concerning suitable piezoelectric materials.

(Conventional technique 1) Piezoelectric materials include lead zirconate titanate, I'b (Zr
Ti)Ot porcelain 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. This method has the advantage of producing porcelain that is highly denatured. In particular, PbTi0l-PbZrOz Pb (group g1/) in which - parts of Zr and Ti are replaced with Mg and Nb.

Nbzzs) 03's three-component piezoelectric ceramic is used in piezoelectric buzzers because it is easy to fire with little lead evaporation, and it is possible to give various piezoelectric properties by adding various additives to the main component. It has been used as a material for 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, an ultrasonic motor is one example. Ultrasonic motors are attracting attention as an alternative to conventional electromagnetic motors for driving robot arms, autofocus camera lenses, and the like. This ultrasonic motor uses the vibration of a piezoelectric ceramic as the driving force for rotation, but in order to obtain better motor characteristics, it is necessary to use a pressure TL.
It is necessary that the amplitude of the vibration of the porcelain is large. In addition, in order to obtain such large vibrations, a large mechanical quality factor and piezoelectric constant are also required. Furthermore, in ultrasonic motors, the piezoelectric ceramic is an elastic body (usually a metal material).
Since the porcelain vibrates while being bonded to the porcelain, the vibrations of the porcelain are restrained by the elastic material 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 (Japanese Patent Publication No. 42-11622)
Mg+zzNbzzx)Os PbTi0z Pb
Zr0z with Mn- added has a large mechanical quality factor, but extremely low piezoelectric constant and mechanical strength.

Further, a product in which ZrO2 is added to the above three-component basic composition is known from JP-A-57-154882, but this also does not have a sufficiently large piezoelectric constant and mechanical quality factor.

(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 lies in the following piezoelectric material.

'a Pb(Mg+7Jbtzs)Ox b Pb
(Co+zJbxzz)Osc PbTiO3-d P
bRepresented by ZrO3, a, bSc above.

and d satisfies the following (1) to (3) 2, and 10 atomic % or less of Pb atoms are substituted with one or more of S, Ca, Ba, and 100 mol% of the ceramic composition. Against Mn
Piezoelectric material 1 containing 0.1 to 5 mol% of each of O2 and Zr01 10 ≦a+b≦55・・・・・・■30
≦c≦ 50 ・ ・ ・ ・ ・■2.5≦d≦
60 ・ ・ ・ ・ ・(3) However, aSb
, c, and d are mol%, and a+b+c+d=100.

Further, a or b may be O, that is, the basis of the piezoelectric material of the present invention is Pb(Mg+7Jbtzs)Oz-PbTi0z-Pb
ZrOs or Pb(Co+z+Nbzz*)Ox
Ternary system of PbTi0z PbZrOs, or Pb(Mg+7Jbtzs)Os Pb(CQ+z
sNbz73) O+ PbTies d PbZr
It is any of the quaternary systems of Os.

(Function) The piezoelectric material of the present invention has a ratio of oxides constituting the basic composition of the above ternary system or quaternary system, that is, the above a, b, c.
, after selecting the value of d appropriately, some of the Pb atoms are 5rS
Substitution with one or more types of CaSBa, and further MnO□ and Z
It is characterized by the addition of r0z.

The reason why the ratio of oxides in the basic composition is determined as above is because the piezoelectric constant becomes small outside this range.

The reason why 10 atomic % or less of Pb in the basic ternary or quaternary oxide is replaced with one or more of Sr, Ca, and Ba is to increase the piezoelectric constant.

However, if this amount of substitution exceeds 10 atomic % of Pb, the piezoelectric constant becomes small.

Note that substituting 10 atomic % or less of Pb means that there are cases where no substitution is made at all.

In addition, Pb (gate g+zJbz/ko) 0. Pb(
CoBJbtz3) On PbTi0z PbZr
O3 ternary system, or Pb (Mgz+Nbzza)O
s Pb(Co+zJbzzs)Os PbTi0
i dPbZr03, Pb(Mg+zJbzzi
)Ox PbTi0t A larger piezoelectric constant than the PbZrO3 system can be obtained.

Based on 100 mol% of the above ceramic composition, MnO
, and Zr0t are added in an amount of 0.1 to 5 mol %, respectively.

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 when it exceeds 5 mol%, both the mechanical quality factor and the piezoelectric constant decrease.

ZrO2 refines the crystal grains of the piezoelectric material and increases its mechanical strength. 0. If it is less than I mol %, the effect is small, and if it exceeds 5 mol %, the precipitation of Zr(h) becomes significant and the piezoelectric constant decreases.

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 was changed to aPb(Mg+zJl)zzz)Oz bPb(Co
+z:+Nbgzs)Osc f'bTto, -d
Represented as PbZr0i (however, a+b+c+d-100), PbO, Zr0z, Ti0z, MgO, CoO, Nbz
Raw materials OsCaCOj, SrCO3, BaC0j, and Mn0z were weighed so as to have the compositions shown in Table 1, and thoroughly mixed using a ball mill. 900 ml of the obtained mixed powder
The calcined product was calcined at ~1000°C for about 2 hours, and the calcined product was thoroughly ground and mixed again in a ball mill, and then an organic binder was mixed therein and granulated. This granulated powder is molded at a pressure of about 1 totu/C111 to a diameter of 20 mm and a thickness of 1,200 to 120 mm.
It was baked at a temperature of 1300°C for about 2 hours.

Further, silver electrodes were baked on both surfaces of the obtained disc-shaped sintered body, and polarization treatment was performed by applying a DC voltage of 2 kv/mm in silicone oil at 100''C.

The piezoelectric properties of the porcelain thus obtained are shown in Table 1. In addition, 631 in the table is a piezoelectric constant, Qm is a mechanical quality factor, and σ is a bending strength.

Samples Nα1 to 12 are Pb(Mg+zsNbz/3)O
x, Pb(Go+zaNbzzz)O*, PbTiOs
, PbZrOs ratio, i.e. a, b.

This shows changes in characteristics due to differences in c and d.

These values are outside the range defined by the present invention (comparative example)
has an extremely small dff+.

Samples HNa13 to 18 are P due to Ca, Sr, and Ba.
This is an example in which the amount of substitution of b is changed. When the amount of substitution exceeds 10 atom%, di+ and Qm as in Nα17 and 18
becomes smaller. Ca.

Whether Sr or Ba is a negative element or a combination of three or more elements, the effect is recognized as long as the total amount is 10 atomic % or less.

Samples Nα19 to Nα24 are examples in which the amount of ZrO2 added was changed.

When the amount added is less than 0.1 mol%, the effect of improving σ is small (Nα 19.20), while when the amount added exceeds 5 mol%, not only σ but also d3. and QIm also worsen.

Samples Nα25 to 30 are examples in which the amount of Mn0z added was changed.

Sample Nα25 with an added amount of MnO2 of less than 0.1 mol%,
Sample No. 26 had no effect of improving Qm, and conversely, in sample No. 30, in which more than 5 mol % was added, Qm decreased and d3 also became small.

Samples Nα31 and 32 are examples in which b and a are O, respectively. Looking at its characteristics, Pb(Mg+/3Nbt/3)0
3 In the PbTi03PbZro+ system, Pb(C
O+7Jbzzx)Os PbTi0i-PbZr0
．． It can be seen that addition of appropriate amounts of MnOz and ZrOt is effective in improving (h+, Om and σ) in the system as well.

(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] aPb(Mg_1_/_3Nb_2_/_3)O_3-
bPb(Co_1_/_3Nb_2_/_3)O_3-
It is represented by cPbTiO_3-dPbZrO_3, where a, b, c, and d above satisfy the following formulas (1) to (3), and 10 at % or less of Pb atoms are one or more of Sr, Ca, and Ba. A piezoelectric material in which 0.1 to 5 mol% of MnO_2 and ZrO_2 are each added to 100 mol% of a porcelain composition substituted with . 10≦a+b≦55 (1) 30≦c≦50 (2) 2.5≦d≦60 (3) However, a, b, c, d is mol%, a or b may be 0, and a+b+c+d=100.