JPH07315924A - Piezoelectric porcelain composition - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric porcelain compsn. ensuring a low sintering temp. of a compact and having a desired high electromechanical coupling factor and a desired high mechanical quality factor as a piezoelectric porcelain compsn. used for a ceramic filter, a ceramic oscillator, a piezoelectric buzzer, etc. CONSTITUTION:A basic compsn. represented by the general formula, PbTiAZrB (Zn1/3Nb2/3)C(Sn1/3-Nb2/3)DO3 (where 0.25<=A<=0.625, 0.20<=B<=0.625, 0<C<=0.50, 0<D<=0.25 and A+B+C+D=1) is prepd. and cobalt oxide and/or nickel oxide are incorporated into the basic compsn. as secondary components by 0.03-3wt.% (expressed in terms of Co3O4) based on the total amt. and 0.05-7wt.% (expressed in terms of NiO) based on the total amt., respectively. The sintering temp. of a compact is reduced and a high mechanical quality factor and/or a high electromechanical coupling factor is ensured. At least one kind of element selected from among Sr, Ca and Ba may be substd. for <= 15 atomic % of Pb atoms.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic composition used particularly for ceramic filters, ceramic oscillators, piezoelectric buzzers and the like.

[0002]

2. Description of the Related Art In recent years, as the amount of communication information such as video signals and audio signals has increased, the propagation frequency has become wider. Further, along with the miniaturization of equipment, miniaturization of individual parts constituting the equipment is required. Piezoelectric ceramics are incorporated in these devices as elements such as ceramic filters and ceramic oscillators. In order to meet the demand for miniaturization, a piezoelectric ceramic composition having a high electromechanical coupling coefficient, relative permittivity, mechanical quality coefficient and the like is required.

Conventionally, Pb (Ti, Zr) O ₃ binary system, PbTi _x Zr _y (Mg _1/3 Nb _2/3 ) _z O ₃ ternary system, and further PbTi _A Zr _B (Zn _1/3 Nb). _2/3 ) _C
A piezoelectric ceramic composition composed of a (Sn _1/3 Nb _2/3 ) _D O ₃ quaternary composition has been proposed according to the intended use (for example, JP-A-47-14697).

[0004]

However, the above-mentioned conventional piezoelectric ceramic composition could not obtain a sufficiently high mechanical quality factor. On the other hand, regarding the electromechanical coupling coefficient,
When the Ti / Zr ratio is brought close to the morphotropic phase boundary in order to obtain a high value, the temperature dependence of the dielectric properties and piezoelectric properties becomes large, and when it is used for ceramic filters, ceramic oscillators, etc. It has a problem that it causes deterioration in function.

Moreover, the conventional piezoelectric ceramic composition has a problem that PbO is vaporized during firing and the characteristics vary because the sintering temperature of the molded product is high. The present invention is to solve the above conventional problems, the sintering temperature of the molded product is low,
It is an object of the present invention to provide a piezoelectric ceramic composition having a desired high electromechanical coupling coefficient and mechanical quality coefficient.

[0006]

[Means for Solving the Problems]
Therefore, the first invention of the present application is based on the general formula PbTi._AZr_B(Zn
_1/3Nb_2/3)_C(Sn_1/3Nb_2/3)_DO₃(However
0.25 ≦ A ≦ 0.625, 0.20 ≦ B ≦ 0.6
25,0 <C ≦ 0.50, 0 <D ≦ 0.25, A + B +
C + D = 1) as a subcomponent to the basic composition
Cobalt oxide to the total amount, Co₃O_FourConverted to 0.0
It also has a structure in which 3 to 3% by weight is added and contained.
Of.

The second invention is the general formula PbTi _A Zr _B
(Zn _1/3 Nb _2/3 ) _C (Sn _1/3 Nb _2/3 ) _D O
₃ (However, 0.25 ≦ A ≦ 0.625, 0.20 ≦ B
≦ 0.625,0 <C ≦ 0.50, 0 <D ≦ 0.25,
A + B + C + D = 1) is added to the basic composition represented by A + B + C + D = 1) in an amount of 0.05 to 7% by weight in terms of NiO with respect to the total amount of nickel oxide.

The third invention is the general formula PbTi _A Zr _B
(Zn _1/3 Nb _2/3 ) _C (Sn _1/3 Nb _2/3 ) _D O
₃ (However, 0.25 ≦ A ≦ 0.625, 0.20 ≦ B
≦ 0.625,0 <C ≦ 0.50, 0 <D ≦ 0.25,
A + B + C + D = 1) with respect to the basic composition expressed as Co ₃ O ₄ in 0.03 to _{3 with} respect to the total amount as an auxiliary component.
It has a constitution in which two kinds of cobalt oxide of 0.05% by weight and nickel oxide of 0.05 to 7% by weight in terms of NiO are added and contained at the same time.

In the structures of the above-mentioned first to third inventions, if necessary, 15 atm.
It can be substituted with at least one element selected from r, Ca and Ba.

[0010]

According to the structure of the first invention, by adding cobalt oxide as an accessory component to the basic composition of the general formula, the sintering temperature can be lowered and the mechanical quality factor can be improved. The mechanical quality factor can be adjusted by adjusting the addition amount of the component.

Next, according to the structure of the second invention, by adding nickel oxide as an accessory component to the basic composition of the general formula, the electromechanical coupling coefficient is improved and the additive amount of the accessory component is adjusted. By doing so, the electromechanical coupling coefficient can be adjusted.

Next, according to the structure of the third invention, the sintering temperature is lowered by simultaneously adding two kinds of cobalt oxide and nickel oxide as auxiliary components to the basic composition of the general formula. It is possible to adjust both the mechanical quality factor and the electromechanical coupling factor by improving the mechanical quality factor and the electromechanical coupling factor and adjusting the amounts of addition of the two subcomponents, respectively.

It is a preferable structure of the first to third inventions,
If necessary, each of the Pb atoms may contain 15 atm.% Or less of S.
Also in the composition in which at least one element selected from r, Ca and Ba is substituted, the sintering temperature can be similarly lowered to improve the mechanical quality factor and / or the electromechanical coupling factor.

[0014]

EXAMPLES An example of the present invention will be described below.
As a starting material, chemically pure PbO and SrC are used.
O ₃ , TiO ₂ , ZrO ₂ , ZnO, Nb ₂ O ₅ , Sn
O ₂ , Co ₃ O ₄ , and NiO were used. After correcting the purity of the raw materials, the raw materials were weighed so as to have various compositions shown in (Table 1), (Table 2), and (Table 3). These powders were placed in a polyethylene ball mill, stabilized zirconia balls and pure were added and mixed for 16 hours. After mixing, dry the slurry, put in an alumina crucible,
It was calcined at 850 ° C. for 2 hours. The calcined powder was pulverized with the above-mentioned ball mill for 16 hours. After crushing, the slurry was dried to obtain a raw material powder. To this raw material powder, 7% by weight of a 5% by weight aqueous solution of polyvinyl alcohol was added as a binder and mixed, and then the mixture was passed through a 32 mesh sieve and granulated.
It was press-molded into a disc shape having a diameter of 13 mm and a thickness of about 0.5 mm at 5 MPa. After heating the molded body at 600 ° C for 2 hours to incinerate the binder, put it in a magnesia porcelain container,
It was capped and held at 1100 to 1350 ° C. for 2 hours for firing. Apply Au deposition electrodes on both sides of the fired body, and
A DC electric field of 3-4 kV / mm is applied in insulating oil at 60 ° C for 30 minutes.
A polarization treatment was performed by applying for a minute. The electromechanical coupling coefficient and the mechanical quality coefficient of the polarized sample were determined by a usual measuring method.

The characteristics of the piezoelectric magnetic composition according to the example and the characteristics of the conventional piezoelectric magnetic composition are shown in (Table 1), (Table 2), and (Table 3).

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

As is clear from (Table 1), the piezoelectric ceramic composition included in the first invention has a lower sintering temperature and a higher mechanical quality coefficient than the comparative examples. Also (Table 2)
As is clear from the above, the piezoelectric ceramic composition included in the scope of the second invention exhibits a higher electromechanical coupling coefficient than the comparative example. Further, as is clear from (Table 3), the piezoelectric ceramic composition included in the third invention has a lower sintering temperature and higher mechanical quality coefficient and electromechanical coupling coefficient than those of the comparative examples.

[0020]

As described above, the piezoelectric ceramic composition of the present invention contains the cobalt oxide as an auxiliary component in addition to the basic composition of the above general formula, so that the sintering temperature is lowered and the mechanical quality is improved. The coefficient can be increased, and the mechanical quality coefficient can be adjusted to a desired value by adjusting the addition amount of the accessory component.

The electromechanical coupling coefficient can be increased by adding nickel oxide as an auxiliary component to the basic composition of the above general formula, and the electromechanical coupling can be achieved by adjusting the addition amount of the auxiliary component. It is possible to adjust the coefficient to a desired value.

Furthermore, by simultaneously adding two kinds of cobalt oxide and nickel oxide as subcomponents to the basic composition of the above general formula, the sintering temperature is lowered and both the mechanical quality factor and the electromechanical coupling factor are increased. By adjusting the amounts of the two subcomponents added, it becomes possible to adjust both the mechanical quality factor and the electromechanical coupling factor to desired values.

The fact that the electromechanical coupling coefficient and the mechanical quality coefficient can be adjusted to desired values facilitates the circuit design of the element and contributes to the miniaturization of parts using the piezoelectric element. Furthermore, by lowering the sintering temperature of the molded product, the evaporation of PbO can be suppressed, the uniformity of the material can be remarkably increased, the variation in the characteristics can be suppressed, and the firing on a mass production scale can be facilitated. can do.

Claims (4)

[Claims] 1. The general formula PbTi _A Zr _B (Zn _1/3 Nb
_2/3 ) _C (Sn _1/3 Nb _2/3 ) _D O ₃ (however, 0.2
5 ≦ A ≦ 0.625, 0.20 ≦ B ≦ 0.625, 0 <
C ≦ 0.50, 0 <D ≦ 0.25, A + B + C + D =
A piezoelectric ceramic composition containing, as a subcomponent, 0.03 to 3% by weight of Co ₃ O ₄ added as a subcomponent to the basic composition represented by 1). 2. The general formula PbTi _A Zr _B (Zn _1/3 Nb
_2/3 ) _C (Sn _1/3 Nb _2/3 ) _D O ₃ (however, 0.2
5 ≦ A ≦ 0.625, 0.20 ≦ B ≦ 0.625, 0 <
C ≦ 0.50, 0 <D ≦ 0.25, A + B + C + D =
0.05 to 7% by weight in terms of NiO, based on the total amount of nickel oxide as a subcomponent with respect to the basic composition represented by 1).
A piezoelectric ceramic composition containing an additive. 3. The general formula PbTi _A Zr _B (Zn _1/3 Nb
_2/3 ) _C (Sn _1/3 Nb _2/3 ) _D O ₃ (however, 0.2
5 ≦ A ≦ 0.625, 0.20 ≦ B ≦ 0.625, 0 <
C ≦ 0.50, 0 <D ≦ 0.25, A + B + C + D =
With respect to the basic composition represented by 1), 0.03 to 3% by weight of cobalt oxide in terms of Co ₃ O ₄ and 0.05 to 7% by weight of nickel oxide in terms of NiO are added as auxiliary components. 2. A piezoelectric ceramic composition containing the two types of the above at the same time. 4. Sr, C is contained in an amount of 15 atm.% Or less of Pb atom.
The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition is substituted with at least one element selected from a and Ba.