JP2000128633A - Piezoelectric porcelain composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric porcelain composition having excellent characteristics as a piezoelectric material and capable of using an Ag-Pd alloy which is a relatively inexpensive electrode and good in sintering properties even when baked at a low temperature such as <=1,000 deg.C capable of suppressing the evaporation of lead oxide. SOLUTION: This piezoelectric porcelain composition comprises nickel, niobium, tantalum, titanium, zirconium and oxygen and is represented by the formula xPb(Ni1/3(Nb1aTaa)2/3)O3-yPbTiO3-zPbZrO3 [(x)+(y)+(z)] is 1}. In the formula, (x), (y) and (z) are each within the ranges of 0.20<(x)<0.60; 0.30<(y)<0.50 and 0.10<(z)<0.50]. Furthermore, the amount of substitution (a) of Ta in Nb sites is within the range of 0<(a)<0.10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates generally relates to such a suitable piezoelectric ceramic composition piezoelectric actuator using a piezoelectric strain, in particular the dielectric constant (ε ₃₃ / ε ₀₎ and piezoelectric properties (d constant) And the firing temperature is 1000
The present invention relates to a piezoelectric porcelain composition as low as not more than ° C.

[0002]

2. Description of the Related Art As a piezoelectric porcelain composition, lead zirconate titanate (PZT) is widely used for various piezoelectric elements such as vibrators since it has a large piezoelectricity and can be used up to high temperatures. . Further, by adding the third component to PZT, porcelain having various characteristics has been obtained.

For example, Pb (Ni _1/3 Nb _2/3 ) O ₃ −
PbTiO ₃ —PbZrO ₃ based piezoelectric ceramic composition is
rans. J. Brit. Ceram. Soc. , 73
(1974) 251 reports that it is a piezoelectric ceramic composition having high piezoelectric properties by Luff et al., Which is suitable for a piezoelectric ceramic for an actuator element.

[0004]

However, the firing temperature of this type of piezoelectric ceramic composition is 1200 to 1300.
℃ and high temperature. For this reason, it is difficult to obtain a dense sintered body due to evaporation of lead oxide at the time of firing, and there is a disadvantage that a composition shift due to evaporation of lead oxide is caused and it is difficult to obtain reproducibility and uniformity of characteristics.

Further, when manufacturing a monolithic sintered type laminated piezoelectric element such as a piezoelectric actuator, the firing temperature is high, so that platinum or palladium which can withstand the firing temperature must be used as the internal electrode, and the cost of the element must be increased. Is a factor that increases

In order to solve the problem of the electrode, it is necessary to set the firing temperature to 1150 ° C. or less at which an Ag-Pd alloy which is a relatively inexpensive electrode can be used, and to control the evaporation of lead oxide. For this purpose, it is necessary to set the firing temperature to 1000 ° C. or less, at which the evaporation of lead oxide rapidly increases.

Accordingly, an object of the present invention is to provide a piezoelectric porcelain composition having excellent properties as a piezoelectric material and having good sinterability even when fired at a low temperature of 1000 ° C. or less. .

[0008]

According to the present invention, there is provided a compound of the general formula xPb
(Ni _1/3 (Nb _1-a Ta _a ) _2/3 ) O ₃ -yPbTiO _3-
A piezoelectric ceramic composition composed of nickel, niobium, tantalum, titanium, zirconium, and oxygen, represented by zPbZrO ₃ (where x + y + z = 1), wherein x, y, and z are respectively 0.20 <x <0.60. , 0.30 <y <
0.50, 0.10 <z <0.50, Nb
The present invention relates to a piezoelectric ceramic composition, wherein the Ta substitution amount a at the site is in the range of 0 <a <0.10. At this time, if the amount b is in the range of 0 <b <5 (parts by weight) when PbO is contained as a subcomponent and the amount b is 100 parts by weight of the main component, the firing temperature can be further lowered. preferable.

[0009] The composition of the porcelain composition is limited to the above range.
The reason is that, for compositions outside the above range, the electromechanical coupling coefficient Kp
Or the relative permittivity ε₃₃/ Ε₀Is significantly reduced
You. The reason for limiting the Ta substitution amount to the above is as follows.
When contained, the relative dielectric constant ε ₃₃/ Ε₀Improves but electricity
This is because the mechanical coupling coefficient Kp decreases. Also, sub-components
The reason for limiting the amount ratio of PbO is that
If it is contained more, the electromechanical coupling coefficient Kp decreases.
That's because.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An example of a preferred method for producing a piezoelectric ceramic composition of the present invention will be described below.

[0011] Lead oxide (PbO), nickel oxide (Ni
O), niobium oxide (Nb ₂ O ₅ ), tantalum oxide (Ta ₂
O ₅ ), titanium oxide (TiO ₂ ), and zirconium oxide (ZrO ₂ ) are weighed, mixed, and pulverized in predetermined amounts. This is calcined at a predetermined temperature in an oxygen-containing gas atmosphere (for example, an air atmosphere) for about 1 to 5 hours. next,
The obtained calcined powder and PbO as an accessory component are wet-mixed with a solvent such as water or alcohol. Subsequently, after removing the solvent, pulverization is performed. Further, the mixture is mixed with an organic binder such as polyvinyl alcohol to homogenize, dried, pulverized, and pressed (with a pressure of about 100 to 1000 kg / cm 2).
The obtained molded product was placed in an oxygen-containing gas atmosphere such as air for 8 hours.
By firing at 00 to 1000 ° C., the piezoelectric ceramic composition represented by the above composition formula is obtained.

After the obtained sintered body is cut and polished, an electrode is formed, and 3 kV /
mm DC voltage for 20 minutes to perform polarization processing,
Measure various piezoelectric characteristics.

Note that lead, nickel, niobium, tantalum,
Raw materials for titanium and zirconium include PbO, Ni
In addition to O, Nb ₂ O ₅ , TiO _2, ZrO _2, etc., nitrates, hydroxides and the like which become oxides during firing can be used.

[0014]

The present invention will be described more specifically with reference to the following examples.

High purity lead oxide (PbO), nickel oxide (NiO), niobium oxide (Nb ₂ O ₅ ), tantalum oxide (Ta ₂ O ₅ ), titanium oxide (TiO ₂ ) and zirconium oxide (ZrO ₂ ) Of which, NiO, Nb ₂ O ₅ , Ta ₂
After weighing and mixing a predetermined amount of O ₅ , 10
Calcination was performed at 00 ° C. for 5 hours. A predetermined amount of the calcined powder and the remaining raw material powder were weighed and mixed and pulverized. This powder was calcined at 800 ° C. for 2 hours in an air atmosphere. Next, a predetermined amount of the obtained calcined powder and lead oxide (PbO) was mixed in a ball mill using zirconia cobblestone with ethanol as a solvent. After desolvating the solution, pulverizing it, adding an appropriate amount of polyvinyl alcohol solution, and drying, forming pellets having a diameter of 10 mm and a thickness of about 2 mm, and baking under an oxygen atmosphere at each temperature shown in Table 1 for 2 hours. did.

The sintered body of the porcelain composition thus obtained is processed into a size having a diameter of 8 mm and a thickness of about 0.5 mm.
An electrode is formed and 3 kV / mm in silicon oil
Was applied for 20 minutes to perform a polarization treatment. Thereafter, the relative permittivity ε ₃₃ / ε ₀ and the electromechanical coupling coefficient Kp were measured. Table 1 shows the characteristics obtained with each composition, together with comparative examples obtained in the same manner.

[0017]

[Table 1]

It can be seen that within the composition range of the present invention, by substituting Ta for Nb, the firing temperature is lowered and the relative dielectric constant is raised. However, when the substitution amount a of Ta increases, Kp tends to decrease. When the substitution amount a is 0.1, sufficient characteristics cannot be obtained.

Further, by adding lead oxide, the firing temperature can be further lowered. But with it
A decrease in p is observed, and when the added amount b of lead oxide is 5.0 parts by weight, a preferable Kp cannot be obtained.

Further, when x, y and x in the above formulas are also outside the above ranges, it can be seen that Kp or the relative permittivity ε ₃₃ / ε ₀ becomes extremely small.

[0021]

As is clear from the above results, the present invention
In the piezoelectric ceramic composition, the relative dielectric constant ε ₃₃/ Ε₀And electric machine
The mechanical coupling constant is large and low temperature firing is possible.
Simultaneous use of relatively inexpensive Ag-Pd etc.
Provided is a piezoelectric ceramic composition that can be laminated by firing.
be able to.

Claims (2)

[Claims] 1. The formula xPb (Ni _1/3 (Nb _1-a Ta _a ))
_{2/3) O 3 -yPbTiO 3 -zPbZrO 3} ( where x + y
+ Z = 1) is a piezoelectric ceramic composition composed of lead, nickel, niobium, tantalum, titanium, zirconium and oxygen, wherein x, y and z are each 0.20 <x
<0.60, 0.30 <y <0.50, 0.10 <z <
0.50, and the Ta substitution amount a of the Nb site is:
A piezoelectric porcelain composition, wherein 0 <a <0.10. 2. PbO is contained as an auxiliary component, and its amount b (parts by weight) is represented by the general formula xPb (Ni _1/3 (Nb _1-a T
a _a ) _2/3 ) When the main component represented by O ₃ -yPbTiO ₃ -zPbZrO ₃ (where x + y + z = 1) is 100 parts by weight, it is within the range of 0 <b <5 (parts by weight). The piezoelectric ceramic composition according to claim 1, wherein: