JP3215013B2 - Piezoelectric ceramic composition - Google Patents

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, for example, a ceramic filter, a ceramic resonator, an ultrasonic oscillator, a piezoelectric buzzer, a piezoelectric ignition unit, an ultrasonic motor, a piezoelectric fan, a piezoelectric actuator, and an acceleration sensor. , A knocking sensor, a piezoelectric ceramic composition suitable for a piezoelectric sensor such as an AE sensor, etc.
In particular, the present invention relates to a piezoelectric ceramic composition which is optimal as a ceramic filter for cellular use.

[0002]

2. Description of the Related Art Conventionally, products utilizing piezoelectric ceramic compositions include, for example, ceramic filters, ceramic resonators, ultrasonic transducers, piezoelectric buzzers, piezoelectric ignition units, ultrasonic motors, piezoelectric fans, piezoelectric sensors, and piezoelectric actuators. Etc.

Here, elements such as a ceramic filter and a ceramic resonator include PbZrO ₃ -PbTi
A porcelain composition containing O ₃ as a main component is used, and a metal oxide such as Nb ₂ O ₅ or MnO ₂ , Pb (Nb
Piezoelectric properties have been improved by adding or replacing composite perovskite oxides such as _2/3 Mg _1/3 ) O ₃ and Pb (Nb _2/3 Mn _1/3 ) O ₃ .

As such a piezoelectric ceramic composition, as a material having a large electromechanical coupling coefficient and excellent piezoelectricity, for example, Pb (Nb _2/3 Co _1/3 ) O ₃ -PbZrO ₃ -P
A bTiO ₃ -based porcelain composition is disclosed.

On the other hand, in recent years, piezoelectric components such as ceramic filters and ceramic resonators have been required to be able to cope with various conditions so that they can be mounted on the surface of a substrate or the like. When a component is reflow-soldered to a substrate, the component mounted on the substrate is exposed to a high temperature of about 300 ° C., so that a piezoelectric element incorporated as a component is also required to have heat resistance.

[0006]

However, the conventional Pb (Nb _2/3 Co _1/3 ) O ₃ --P
bZrO ₃ -PbTiO ₃ system ceramic composition, a change in the piezoelectric characteristics and the resonance frequency before and after the reflow soldering low heat resistance is large, has been a practical problem. In addition, since the temperature coefficient (TC fr) of the resonance frequency is as large as 50 ppm / ° C. or more, when the filter is used for a filter of a vehicle-mounted communication device or the like in which the environment changes drastically, stable transmission and reception due to a change in element characteristics. There was a problem that it became impossible.
Further, the above-mentioned composition has a problem that the mechanical quality factor Qm is as high as 300 or more, and is not suitable for a material for a cellular filter, for example, which requires a flat group delay characteristic.

An object of the present invention is to provide a piezoelectric ceramic composition having excellent heat resistance, excellent temperature characteristics of resonance frequency, and having a high electromechanical coupling coefficient and a low mechanical quality coefficient.

[0008]

[Means for Solving the Problems] The present inventors have proposed Ca,
At least one of Sr and Ba, Nd, Gd, L
at least one of a, Pr, Sm, Pb, Zr,
A composite perovskite compound containing Ti, Nb, Yb, Cr and Co, having a certain composition,
Piezoelectric material that has excellent heat resistance, temperature characteristics of resonance frequency, high electromechanical coupling coefficient Kp, and requires flat group delay characteristics. For example, a piezoelectric material having a low mechanical quality factor Qm which is optimal as a ceramic filter for cellular use. The inventors have found that a porcelain composition can be obtained, and have reached the present invention.

That is, the piezoelectric ceramic composition of the present invention comprises at least one of Ca, Sr, and Ba as a metal component;
at least one of d, Gd, La, Pr, and Sm;
Pb, Zr, Ti, Nb, Yb, a composite perovskite compound containing Cr and Co, the composition formula by molar ratio of the metal elements _{(Pb 1-xy A x B} y) a [{(Nb 1 _{/ 2 Yb 1/2) b (Nb} 1/2 Cr 1/2) c (Nb 2/3 Co 1/3) 1-bc} 1-d Nb d] e (Ti f Zr 1-f) 1- _When expressed as eO ₃ , the values of x, y, a, b, c, d, e, and f are 0 <x, 0 <y, 0 <x + y ≦ 0.12, 0.9
70 ≦ a ≦ 1.030, 0.100 ≦ b ≦ 0.700,
0.100 ≦ c ≦ 0.700, 0 ≦ d ≦ 0.170,
0.030 ≦ e ≦ 0.200, 0.480 ≦ f ≦ 0.6
00 is satisfied. Where A is Ca, S
r, at least one of Ba and B is Nd,
It is at least one of Gd, La, Pr, and Sm.

Here, x, y, a, b, c, d, e, f
The reason for setting the value in the above range will be described. P
Part of b is replaced with at least one of Ca, Sr, and Ba because the temperature coefficient of the resonance frequency can be controlled, and among these, Sr is optimal. Further, a part of Pb is converted to Nd, Gd, La, Pr, Sm.
The reason for replacing with at least one of the above is that control of the temperature characteristic of the resonance frequency and reduction of the mechanical quality factor Qm can be performed at the same time, and among these, La is optimal.

The reason why the total amount of Pb replaced by other elements is x + y ≦ 0.12 is that when x + y is larger than 0.12. In the present invention, x is from 0.025 to from the viewpoint of heat resistance.
0.06, y is 0.005 to 0.02, x + y is 0.0
3-0.08 is desirable.

[0012] The _{(Pb 1-xy A x B} y) of a 0.97
The reason for 0 ≦ a ≦ 1.030 is that the electromechanical coupling coefficient Kp decreases when a is less than 0.970 or greater than 1.030. _{(Pb 1-xy A x B} y)
It is particularly preferred that the amount is 0.980 ≦ a ≦ 1.010.

[0013] Further, the amount of (Nb _1/2 Yb _1/2 ) b is set to 0.
The reason for 100 ≦ b ≦ 0.700 is that if b is less than 0.10, the electromechanical coupling coefficient Kp decreases, and if b is greater than 0.700, the heat resistance decreases. (N
It is particularly desirable that the amount of (b _1/2 Yb _1/2 ) is 0.150 ≦ b ≦ 0.300.

The amount of (Nb _1/2 Cr _1/2 ) c is 0.1
The reason for setting 00 ≦ c ≦ 0.700 is that when c is less than 0.100, the heat resistance decreases, and when c is greater than 0.700, the mechanical quality factor Qm increases. (Nb
_1/2 Cr _1/2) the amount, it is particularly desirable from the viewpoint of reducing the mechanical quality factor Qm is 0.150 ≦ c ≦ 0.550. The present inventors have proposed that at least P
b, and filed Zr, Ti, Nb, Yb, composite perovskite compounds containing Co, previously to this as system with the addition of Cr ₂ O ₃ powder (Japanese Patent Application No. 5-329252
However, in this system, the mechanical quality factor Qm is increased by adding Cr ₂ O ₃ powder. on the other hand,
In the present application, the weight is measured so as to be replaced in the form of (Nb _1/2 Cr _1/2 ), and in the earlier application, the weight is not replaced in such a form, so that the mechanical quality factor Qm becomes higher,
This is optimal for filters such as AM radio that require high selectivity.

Further, d of the Nb amount is set to 0 ≦ d ≦ 0.170.
The reason for this is that the mechanical quality factor Qm decreases as the Nb content increases, but the electromechanical coupling factor Kp sharply decreases when d is greater than 0.17. It is particularly desirable that the amount of Nb is 0.050 ≦ d ≦ 0.150.

[｛(Nb _1/2 Yb _1/2 ) _b (Nb _1/2 C
r _1/2 ) _c (Nb _2/3 Co _1/3 ) _{1- bc} ｝ _1-d Nb _d ]
Of _{(Ti f Zr 1-f)} 0.03 ≦ e ≦ 0 the substitution amount e to.
The reason for setting it to 2 is that if e is less than 0.03, no improvement in heat resistance is observed, and if it is more than 0.2, the electromechanical coupling coefficient Kp drops sharply. [｛(Nb _1/2 Yb _1/2 )
_b (Nb _1/2 Cr _1/2 ) _c (Nb _2/3 C
o _1/3 ) _1-bc { _1-d Nb _d ] The amount is 0.05 ≦ e ≦ 0.
A value of 1 is particularly desirable.

The replacement amount f of Ti with Zr is 0.48 ≦ f ≦
The reason for setting to 0.6 is that when f is less than 0.48, no improvement in heat resistance is observed, and when f is greater than 0.6, the electromechanical coupling coefficient decreases. It is particularly desirable that the substitution amount of Ti for Zr is 0.49 ≦ f ≦ 0.53.

The piezoelectric ceramic according to the present invention is, for example, composed of PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ , Y as raw materials.
b ₂ O ₃ , Cr ₂ O ₃ , CoO, SrCO ₃ , La ₂ O
₃ was converted to Pb-Zr-Ti (PZT) -based Z
r and part of Ti are converted to Nb _1/2 Yb _1/2 , Nb _1/2 C
A predetermined amount is weighed so that r _1/2 , Nb _2/3 Co _1/3 , and Nb are substituted, and a part of Pb is replaced with Sr and La, and wet weighed by a ball mill or the like for 10 to 24 hours. After mixing and then dehydrating and drying this mixture, 500-110
The calcined product is calcined at 0 ° C. for 1 to 3 hours, the calcined product is again pulverized by a ball mill or the like, an organic binder is mixed with the pulverized product, granulated, and then molded at a predetermined pressure to produce a molded body. It is obtained by firing in the air at 1200 to 1350 ° C for 0.5 to 4.0 hours.

[0019]

According to the piezoelectric ceramic composition of the present invention, Pb-Zr-T
Some of the i (PZT) -based Zr and Ti are converted to (Nb _1/2
Yb _1/2 ), (Nb _1/2 Cr _1/2 ), (Nb _2/3 Co _{1 /
3} ) By substituting with Nb, excellent heat resistance, high electromechanical coupling coefficient, and low mechanical quality factor Qm
Can be obtained. In the present invention, in particular, by substituting Nb _1/2 Cr _1/2 and Nb, the mechanical quality factor Qm can be reduced, a flat group delay characteristic can be achieved, and the ceramic filter can be optimized as a ceramic filter for cellular use. it can.

A part of Pb is at least one of Ca, Sr, and Ba, and Nd, Gd, La, Pr, Sm.
By replacing with at least one of the above, the temperature coefficient of the resonance frequency can be reduced and the mechanical quality factor Qm can be reduced.

[0021]

The present invention will be described below with reference to the following examples. PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ ,
Yb ₂ O ₃ , Cr ₂ O ₃ , CoO, CaCO ₃ , SrC
O ₃ , BaCO ₃ , Nd ₂ O ₃ , Gd ₂ O ₃ , La ₂ O
₃ , Pr ₂ O ₃ , and Sm ₂ O ₃ are shown in Tables 1 and 2,
As shown in FIG. 3, a part of PZT-based Zr and Ti is converted to Nb _1/2 Y.
b _1/2, Nb _1/2 Cr _1/2, and at least one way, also a part of Pb Ca, Sr, among Ba Nb _2/3 Co _1/3, substituted by Nb, Nd, Gd, La, Pr, S
m is weighed so as to be replaced with at least one of m, wet-mixed in a ball mill for 12 hours, then the mixture is dehydrated and dried, and then calcined at 900 ° C. for 3 hours. And crushed.

Thereafter, an organic binder (P
VA) was mixed and granulated. 1.5 t /
It was press-formed at a pressure of cm ² into a disk having a size of 23 mm in diameter and 2 mm in thickness. Furthermore, these compacts are
It was sealed in a container made of O or the like, and baked at 1300 ° C. in the atmosphere for 2 hours.

The obtained sintered body is polished to a thickness of 0.5 mm.
Was formed. Electrodes are formed by baking Ag paste on both principal surfaces of the disc, and applying a DC voltage of 3 kV / mm in silicon oil at 80 ° C. for 30 minutes for polarization treatment. Properties and temperature characteristics were evaluated.

The electromechanical coupling coefficient Kp was calculated from the values of the resonance frequency and the antiresonance frequency measured by an impedance meter. The heat resistance was determined from the value of the resonance frequency Fr ₀ before the test and the value of the resonance frequency Fr ₂₄ after the test ₂₄ Hr when the test was performed by continuously passing through a reflow furnace having a peak at 250 ° C. three times, ΔFr = ( Fr ₂₄ −Fr ₀ ) / Fr ₀
The evaluation was performed with the change rate ΔFr calculated using the formula of × 100. Further, the temperature coefficient T. C. fr (ppm
/ ° C) is calculated from the value of the resonance frequency measured in the range of -20 ° C to + 80 ° C. C. _{fr = (Fr 80 -Fr -20)} /
100 × 10 ⁶ / Fr ₂₀ (where Fr ₈₀ , Fr _-20 ,
Fr ₂₀ respectively + 80 ℃, -20 ℃, was calculated using the formula shown) the resonance frequency at + 20 ° C.. Tables 3 and 4 show the results.
Shown in

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

From Tables 3 and 4, it can be seen that the porcelain composition of the present invention has a large electromechanical coupling coefficient Kp of 50% or more, a mechanical quality factor Qm of 150 or less, and a change in resonance frequency due to a heat resistance test of ± 10%. It is as small as 0.10% or less. In addition, the temperature coefficient (TC fr) of the resonance frequency shows that a part of Pb is C
By substituting at least one of a, Sr, and Ba, the temperature characteristic of the resonance frequency can be controlled,
It can be seen that by replacing a part of Pb with at least one of Nd, Gd, La, Pr, and Sm, it is possible to simultaneously control the temperature characteristic of the resonance frequency and the reduction of the mechanical quality factor Qm.

[0030]

As described in detail above, according to the present invention, P
A part of Zr and Ti of the b-Zr-Ti (PZT) system is converted to (Nb _1/2 Yb _1/2 ), (Nb _1/2 Cr _1/2 ),
(Nb _2/3 Co _1/3 ) and Nb, and a part of Pb is replaced with at least one of Ca, Sr and Ba and N
By replacing with at least one of d, Gd, La, Pr, and Sm, it has excellent heat resistance, temperature characteristics of resonance frequency, high electromechanical coupling coefficient, and low mechanical quality coefficient Qm. Elements such as piezoelectric components for surface mounting, which can obtain materials and show stable characteristics against temperature changes,
For example, an optimal piezoelectric ceramic composition can be obtained as an element such as a filter or a resonator, and particularly as a ceramic filter for cellular use.

Continuation of front page (56) References JP-A-8-26825 (JP, A) JP-A-7-82021 (JP, A) JP-A-7-69723 (JP, A) JP-A-8-165169 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/42-35/49 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A metal component comprising at least one of Ca, Sr and Ba, at least one of Nd, Gd, La, Pr and Sm, Pb, Zr, Ti, Nb, Yb and C
A composite perovskite compounds containing r and Co, the composition formula by molar ratio of the metal elements _{(Pb 1-xy A x B} y) a [{(Nb 1/2 Yb 1/2) b (Nb _1/2 Cr _1/2) when expressed as _{c (Nb 2/3 Co 1/3) 1} -bc} 1-d Nb d] e (Ti f Zr 1-f) 1-e O 3, wherein x , Y, a, b, c, d, e, and f are 0 <x 0 <y 0 <x + y ≦ 0.12 0.970 ≦ a ≦ 1.030 0.100 ≦ b ≦ 0.700 0. 100 ≦ c ≦ 0.700 0 ≦ d ≦ 0.170 0.030 ≦ e ≦ 0.200 0.480 ≦ f ≦ 0.600 A: At least one of Ca, Sr, and Ba B: Nd, Gd, A piezoelectric ceramic composition satisfying at least one of La, Pr, and Sm.