JP2001253772A - Piezoelectric porcelain composition and method for manufacture the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric porcelain composition of a PbZrO3-PbTiO3 component system which has a high electrical machine coupling coefficient and low dielectric constant and may be fired at a low temperature. SOLUTION: The piezoelectric porcelain composition is constituted by using PbZrO3-PbTiO3-Pb(Zn1/3Sb2/3)O3 as an essential component and incorporating elements Li, Bi and Cu in a range 0 wt.%<Li2CO3<1.0 wt.%, 0 wt.%<Bi2 O3<1.0 wt.% and 0 wt.%<CuO<2.0 wt.%, respectively in terms of Li2CO3, Bi2O3 and CuO therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides a high electromechanical coupling coefficient, which has the electrical characteristics of low dielectric constant, a piezoelectric ceramic composition PbZrO ₃ -PbTiO ₃ composition system capable of low-temperature firing and a method of manufacturing the same For example, it is suitable as an element constituting an ultrasonic transducer, an ultrasonic motor, a piezoelectric actuator, or the like.

[0002]

2. Description of the Related Art Conventionally, there have been used ultrasonic transducers, ultrasonic motors, piezoelectric actuators, and the like in which a displacement generated by a piezoelectric effect is used as a mechanical drive source. One.

[0003] For example, a laminated piezoelectric actuator is constructed by sintering and integrating a plurality of laminated bodies in which green sheets made of a piezoelectric material on which a conductor paste as an electrode is printed are stacked and integrated. Compared to conventional electromagnetic actuators that have been wound, they have low power consumption and heat generation, have excellent response speed, and have excellent features such as large displacement, small size and small weight, and have been attracting attention in recent years. Used in ink jet printer heads and the like. Then, as the piezoelectric material constituting these piezoelectric _actuators, the piezoelectric ceramic composition of PbZrO 3 -PbTiO ₃ composition system has been used.

[0004] By the way, as the applications of the above-mentioned piezoelectric actuators and the like have expanded, mechanical displacement can be obtained at a higher speed, and at the same time, a device which consumes less power and generates less heat is required. Among the piezoelectric characteristics of the porcelain composition, those having a high electromechanical coupling coefficient, a low dielectric constant, and excellent in durability without deterioration even when repeatedly displaced are desired. That is, by using a piezoelectric ceramic composition having a high electromechanical coupling coefficient and a low dielectric constant, electric energy can be efficiently converted to mechanical energy, and the power consumption of the piezoelectric element is small and the heat generation is small. A suitable piezoelectric actuator can be obtained.

As a piezoelectric ceramic composition meeting such a purpose, Pb (ZrO ₃ -PbTiO ₃ composition system, Pb (Z
The present applicant has already proposed a solution in which (n _1/3 Sb _2/3 ) O ₃ is dissolved as a third component (JP-A-7-4512).
No. 4).

[0006]

However, PbZrO
Pb (Zn _1/3 Sb _2/3 ) O _{3 is} added to the _3- PbTiO ₃ composition system.
The conventional piezoelectric ceramic composition having a solid solution of
Since the temperature is as high as 00 to 1300 ° C., when the piezoelectric ceramic composition and the electrode are sintered and integrated together like a laminated piezoelectric actuator, there are few electrode materials that can withstand the above firing temperature range. There is a problem that very expensive metals such as Pd and Pd must be used.

[0007] In addition, if the firing temperature is high, equipment for this is required, and as a result, inexpensive products cannot be provided.

[0008]

An object of the present invention is an object of the _invention, PbZrO 3 -PbT
Piezoelectric ceramic composition capable of further lowering the dielectric constant and firing at a low temperature without significantly lowering the high electromechanical coupling coefficient of iO ₃ -Pb (Zn _1/3 Sb _2/3 ) O ₃ Object and a method for producing the same.

[0009]

Means for Solving the Problems In order to achieve the above object, the inventors of the present invention have proposed PbZrO ₃ -PbTi.
After intensive research on piezoelectric ceramic compositions mainly composed of O ₃ —Pb (Zn _1/3 Sb _2/3 ) O ₃ , it was found that other components such as Li, Bi, and Cu were contained. As a result, the inventors have found that the above problems can be eliminated, and have reached the present invention.

That is, the present invention relates to PbZrO ₃ -PbTi
O ₃ -Pb (Zn _1/3 Sb _2/3 ) O ₃ is mainly used, and Li,
Bi and Cu are represented by Li ₂ CO ₃ and Bi, respectively.
In terms of ₂ O _3, CuO, 0 _{wt% <Li 2 CO 3 <1} .
0 wt%, 0 wt% <Bi ₂ O ₃ <1.0% by weight, is obtained by the piezoelectric ceramic composition contains in the range of 0 wt% <CuO <2.0% by weight.

The present invention also relates to a method for manufacturing the piezoelectric ceramic composition, wherein PbZrO ₃ -PbTiO ₃ -Pb
A calcined powder mainly composed of (Zn _1/3 Sb _2/3 ) O ₃ is prepared, and Li ₂ CO ₃ , Bi ₂ O ₃ , and CuO powders are added to the calcined powder, and Li, Bi and Cu content is Li ₂ C
0% by weight <Li ₂ C in terms of O ₃ , Bi ₂ O ₃ , CuO
O ₃ <1.0% by weight, 0% by weight <Bi ₂ O ₃ <1.0% by weight, 0% by weight <CuO <2.0% by weight, and then molded into a predetermined shape. Later, 900-10
It is designed to be fired at a temperature of 00 ° C.

[0012]

The piezoelectric ceramic composition of the present invention DETAILED DESCRIPTION OF THE INVENTION, principal _{PbZrO 3 -PbTiO 3 -Pb (Zn,} Sb) O 3
PbZrO ₃ —PbTiO
₃ (hereinafter referred to as PZT), Pb (Zn _1/3 Sb)
_2/3 ) By forming a solid solution of O ₃ as the third component, the electromechanical coupling coefficient among the piezoelectric characteristics can be increased, and the deterioration of the piezoelectric characteristics can be suppressed even when a constant load is repeatedly applied. As a result, the durability can be improved.

Here, the main component is PbZrO_Three-PbTiO_Three
-Pb (Zn, Sb) O_ThreeConsists of a part of Pb
One substituted with Sr or Ba, or Pb as the fourth component
(Ni _1/2 Te_1/2) O_ThreeIncluding solid solution of
Say

Specifically, the composition formula is represented by Pb_1-xySr_xBa
_y(Zn_1/3 Sb_2/3)_aZr_bTi_{1 -ab}O_ThreeExpressed
When x, y, a and b are 0 ≦ x ≦ 0.14, 0 ≦ y ≦ 0.
14, 0 <x + y, 0.01 ≦ a ≦ 0.12, 0.43
≦ b ≦ 0.58 or the composition formula is Pb_1-xy
Sr_xBa_y(Zn_1/3 Sb_2/3)_a(Ni_1/2 T
e_1/2) _cZr_bTi_1-abcO_ThreeX, y,
a, b, c are 0 ≦ x ≦ 0.14, 0 ≦ y ≦ 0.14, 0
<X + y, 0.01 ≦ a ≦ 0.12, 0.43 ≦ b ≦
0.58, 0.002 ≦ c ≦ 0.02
Can be used.

The reason why the substitution amount a of Ti with (Zn _1/3 Sb _2/3 ) is set to 0.12 or less is that if the substitution amount a is increased, the electromechanical coupling coefficient can be increased. However, if the substitution amount a exceeds 0.12, the dielectric loss becomes too large, which is not preferable. In addition,
When the substitution amount a is less than 0.01, the effect of increasing the electromechanical coupling coefficient cannot be obtained, and the characteristic deterioration due to stress and heat applied repeatedly due to piezoelectric deformation is not preferable. Therefore, the substitution amount a is 0.01 ≦ a ≦ 0.12
It is good to be in the range.

Further, in the piezoelectric ceramic composition containing PZT as a main component, when the solid solution ratio of PbZrO ₃ and PbTiO ₃ is changed, MPB (composition phase boundary) showing the maximum value of the electromechanical coupling coefficient exists, It is preferable to use the MPB and the composition value in the vicinity of the MPB as elements such as an acoustic transducer, an ultrasonic motor, and a piezoelectric actuator. And this MPB
Changes depending on the amount of the substitution amount x or the substitution amount a, so that the value of the substitution amount b is a composition that captures MPB within the composition range of the substitution amount x or the substitution amount a, that is, 0.43 ≦ b ≦ 0.58. By doing so, the MPB can be captured.

Further, the present invention provides a method for producing PZT-Pb (Zn
_1/3 Sb _2/3 ) O ₃ , Li, B
It is characterized by containing three components of i and Cu.

That is, Li, B contained as other components
The three components i and Cu have ionic radii that are easily replaced by Zr and Ti, and have a low melting point. In each case, a liquid phase is formed at a low temperature from the initial stage to the middle stage of sintering to promote sintering, At the end of the conclusion, PZT-Pb (Zn
_1/3 Sb _2/3 ) O ₃ element is substituted into the crystal lattice and sintered, so that the firing temperature of the piezoelectric ceramic composition is 1
It can be lowered to below 000 ° C.

However, if the liquid phase component having no ferroelectricity remains at the grain boundary as it is, the electromechanical coupling coefficient of the piezoelectric ceramic composition after sintering will be significantly deteriorated. However, according to the study of the present inventors, PZT-Pb
(Zn _1/3 Sb _2/3 ) O ₃ contains Li, Bi, and Cu in addition to lowering the sintering temperature, as well as PZT-Pb (Zn _1/3 Sb _2/3 ). It has been found that the dielectric constant can be reduced while maintaining the high electromechanical coupling coefficient of O ₃ .

These effects cannot be obtained only by containing Li, Bi or Cu elements alone or only by two components. Even when three components are contained, each component is made of Li ₂ CO _3. , Bi ₂ O ₃ , and CuO, L
i ₂ CO ₃ is 1.0% by weight or more, Bi ₂ O ₃ is 1.0% by weight
It has been found that when the content of CuO is 2.0% by weight or more, the electromechanical coupling coefficient of the piezoelectric ceramic composition is significantly reduced.

Therefore, Li to be contained as another component,
The elements of Bi and Cu are Li ₂ CO ₃ , Bi ₂ O ₃ , Cu
In terms of O, 0% by weight <Li ₂ CO ₃ <1.0% by weight,
0% by weight <Bi ₂ O ₃ <1.0% by weight, 0% by weight <CuO
It is important to contain it in the range of <2.0% by weight, and by containing three components in these ranges, it is possible to lower the relative dielectric constant to 2900 or less while maintaining a high electromechanical coupling coefficient. It can be fired at a temperature of 1000 ° C. or less. As a result, in the manufacture of piezoelectric actuators and the like, Ag is less expensive than Pt or Pd.
An electrode material mainly composed of, for example, an electrode material containing 90% or more of Ag can be used, and when used as a piezoelectric actuator, displacement can be performed at high speed with low consumption and small heat generation.

By the way, as a method for producing such a piezoelectric ceramic composition of the present invention, for example, Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , ZnO, Sb ₂ O ₃ as starting materials and, if necessary, BaCO _3, SrCO _3, NiO, each powder was weighed mixed TeO _2, then dehydrated mixture, followed by drying, and 1 to 3 hours and calcined at 850 to 900 ° C., pulverized to PZT-Pb (Zn _{1 / 3} Sb _2/3 ) Produce calcined powder mainly composed of O ₃ . Then, Li _{2 is} added to the calcined powder.
A predetermined amount of powder of CO ₃ , Bi ₂ O ₃ and CuO is added and mixed. Then, a slurry is produced from these mixtures and a molded body is obtained by a tape molding method, an extrusion molding method, or a casting method, or the mixture is granulated and dried to produce granules and filled in a mold. Then, a molded body is formed into a predetermined shape by a uniaxial pressure molding method or an equal pressure molding method. Thereafter, the obtained molded body is 900 to 1000 in an air atmosphere or an oxygen atmosphere.
C., preferably at 920 to 980 ° C. for about several hours.

[0023]

EXAMPLE Pb ₃ O ₄ , ZrO ₂ , Ti
Each powder of O ₂ , ZnO, Sb ₂ O ₃ , BaCO ₃ , and SrCO ₃ was prepared by mixing 0.90 mol of Pb, 0.49 mol of Zr,
0.44 mol, Zn 0.02 mol, Sb 0.05
Mol, Ba was 0.02 mol, and Sr was weighed so as to have a ratio of 0.08 mol, and wet-mixed in a ball mill for 24 hours. Next, the mixture was dehydrated and dried, and then calcined at 900 ° C. for 3 hours to obtain a calcined powder.

When the calcined powder was subjected to composition analysis by ICP emission spectroscopy, the composition formula was Pb _1-xy Sr _x Ba.
_{y (Zn 1/3 Sb 2/3) a} Zr b Ti 1-ab O 3 (x: 0.
08, y: 0.02, a: 0.07, b: 0.49).

Next, Li ₂ CO ₃ , Bi ₂ O ₃
And CuO powder were added at the ratios shown in Table 1, and wet-pulverized by a ball mill for 24 hours. Further, an organic binder was added and kneaded, followed by drying and granulation to obtain granules. Then, the obtained granules were uniaxially pressed into a disc having a diameter of 20 mm and a thickness of 2 mm at a pressure of 1.5 t / cm ² ,
The firing was performed in an air atmosphere while maintaining the firing temperature at 940 ° C.

Thereafter, the obtained piezoelectric ceramic composition was processed into a strip having a thickness of 1 mm, a width of 3 mm and a length of 12 mm, and silver electrodes were baked on both sides.
Polarization treatment was performed by applying a DC voltage of kV / mm for 30 minutes to obtain a sample.

For each sample, the contents of Li, Bi, and Cu were determined by ICP emission spectroscopy to be Li ₂ CO ₃ , Bi.
_{In addition to} measurement in terms of ₂ O ₃ and CuO, piezoelectric characteristics (electromechanical coupling coefficient k ₃₁ , relative dielectric constant 率₃₃ ^T / ε ₀ ) were measured based on the Electronic Industries Association Standard EMAS-6004.

The criterion is as follows:
o. When the conventional piezoelectric ceramic composition shown in FIG. 1 was used as a reference sample, the piezoelectric properties of which the relative dielectric constant was 2900 or less and the electromechanical coupling coefficient was 100% or more of the reference sample were □. If the coefficient is 95% or more and less than 100%, it is evaluated as ○.
%, And those having an electromechanical coupling coefficient of less than 90% were evaluated as x, and those having a relative dielectric constant of 2900 or less and an electromechanical coupling coefficient of 90% or more were evaluated as good.

The results are as shown in Table 1.

[0030]

[Table 1]

As a result, the sample No. No. 3 containing Bi alone, sample No. 3 In the case of the sample containing two types of Li and Bi as in No. 5, sintering at 940 ° C. was not possible, and sintering at 1000 ° C. was not possible.

The sample No. Samples containing only Li or Cu as in Sample Nos. Those containing two components among Li, Bi and Cu as in 6, 7 are 94
Although sintering was possible at 0 ° C., the electromechanical coupling coefficient was as low as 82% or less of the reference sample.

Further, even if the sample containing three components of Li, Bi and Cd was used, the sample No. Like 10,14,18,
Li content of 1.0% by weight or more in terms of Li ₂ CO ₃ , Bi content of 1.0% by weight or more in terms of Bi ₂ O ₃ , Cu being 2.0% by weight in terms of CuO In all of the above, the electromechanical coupling coefficient was as small as less than 90% of the reference sample.

On the other hand, the sample No. 8,9,11-1
Nos. 3, 15 to 17 each contain three components of Li, Bi, and Cu, and their contents are respectively 0 <Li ₂ CO ₃ <1.
0 _{wt%, 0 <Bi 2 O 3} <1.0 wt%, 0 <CuO <
Since it is in the range of 2.0% by weight, it can be sufficiently sintered even at a low temperature of 940 ° C., and has a relative dielectric constant of 2900.
And the electromechanical coupling coefficient is 90% of that of the reference sample.
I was able to do above.

From these results, it was found that three components Li, Bi, and Cd were contained, and the contents of each component were 0 <Li ₂
CO ₃ <1.0% by weight, 0 <Bi ₂ O ₃ <1.0% by weight,
If 0 <CuO <2.0% by weight, PZT-Pb (Z
The dielectric constant can be reduced while maintaining the high electromechanical coupling coefficient of n _1/3 Sb _2/3 ) O ₃ , and 100
It can be seen that firing can be performed at a temperature of 0 ° C. or less.

When these piezoelectric ceramic compositions are used for a piezoelectric actuator or the like, an energy-saving element can be obtained, and Ag-Pd or Ag-Pt can be used as an electrode material.
(However, Ag is 50% by weight or more) or Ag (1
00% by weight) and expensive Pd or Pd
Since the amount of t can be significantly reduced, it is possible to manufacture the device at low cost.

[0037]

As described above, according to the present invention, PbZrO ₃ -PbTiO ₃ -Pb (Zn _1/3 S
b _2/3 ) Li ₂ CO ₃ and B for calcined powder mainly composed of O ₃
i ₂ O ₃ and by forming a material obtained by adding powder of CuO in a predetermined shape, and thereafter, the molded article 900 to 1000 ° C.
Baking at a temperature of PbZrO ₃ -PbTiO ₃ -Pb
(Zn _1/3 Sb _2/3 ) O ₃ is the main component, and the elements Li, Bi, and Cu are Li ₂ CO ₃ , Bi ₂ O ₃ , and CuO, respectively.
0% by weight <Li ₂ CO ₃ <1.0% by weight, 0
Wt% <Bi ₂ O ₃ <1.0 wt%, 0 wt% <CuO <
Since the piezoelectric ceramic composition was obtained by containing each in the range of 2.0% by weight, PbZrO ₃ -PbTiO ₃ -Pb
The dielectric constant can be reduced while maintaining the excellent electromechanical coupling coefficient of (Zn _1/3 Sb _2/3 ) O _3.
Firing at a low temperature of 000 ° C. or less becomes possible. Therefore, the use of the piezoelectric ceramic composition of the present invention makes it possible to produce ultrasonic applied vibrators, ultrasonic motors, piezoelectric actuators, and the like that can be displaced at high speed with low power consumption and small heat generation. Since (Ag) can be used as the electrode material, it can be manufactured at low cost.

Claims (2)

[Claims] [Claim 1] PbZrO ₃ -PbTiO ₃ -Pb (Zn
_1/3 Sb _2/3 ) O ₃ as the main component, Li, Bi, and Cu
Are converted to Li ₂ CO ₃ , Bi ₂ O ₃ and CuO, respectively, and 0% by weight <Li ₂ CO ₃ <1.0% by weight and 0% by weight
<Bi ₂ O ₃ <1.0% by weight, 0% by weight <CuO <2.0
A piezoelectric ceramic composition which is contained in the range of weight%. 2. PbZrO ₃ -PbTiO _3- prepared in advance
_{Pb (Zn 1/3 Sb 2/3} ) O 3 Li 2 CO 3 with respect to the calcined powder composed mainly of, Bi ₂ O _3, and a powder of CuO, after sintering Li, Bi, and Cu Element content of Li ₂ C
0% by weight <Li ₂ C in terms of O ₃ , Bi ₂ O ₃ , CuO
O ₃ <1.0% by weight, 0% by weight <Bi ₂ O ₃ <1.0% by weight, 0% by weight <CuO <2.0% by weight, and then molded into a predetermined shape. Later, 900-10
A method for producing a piezoelectric ceramic composition, comprising firing at a temperature of 00 ° C.