JPH0920559A - Piezoelectric ceramic composition - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a piezoelectric ceramic composition having excellent heat resistance and temperature characteristics of resonance frequency, having a high electromechanical coupling coefficient and a low electromechanical coefficient. [Configuration] 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) when expressed as _{1-e O 3, x,} y, a, b, c, d, e, The value of f is 0 <x, 0 <y, 0 <x + y ≦ 0.12, 0.97
0 ≦ 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.

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 transducer, a piezoelectric buzzer, a piezoelectric ignition unit, an ultrasonic motor, a piezoelectric fan, a piezoelectric actuator and an acceleration sensor. , A piezoelectric ceramic composition suitable for piezoelectric sensors such as knocking sensors and AE sensors,
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]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the prior art, for example, the above-mentioned Pb (Nb _2/3 Co _1/3 ) O ₃ --P
The bZrO ₃ —PbTiO ₃ based porcelain composition has a low heat resistance and a large change in piezoelectric characteristics and resonance frequency before and after reflow soldering, which 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 it is used for a filter of a vehicle-mounted communication device or the like whose environment changes drastically, stable transmission / reception due to changes in the element characteristics is possible. There was a problem that I could not do it.
Further, the above-mentioned composition has a problem that it has a high mechanical quality factor Qm of 300 or more and is not suitable as a material for a filter for a cell, for example, which requires flat group delay characteristics.

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

[0008]

[Means for Solving the Problems]
At least one of Sr and Ba, Nd, Gd, L
at least one of a, Pr and Sm, Pb, Zr,
A compound perovskite type compound containing Ti, Nb, Yb, Cr and Co, which has a constant composition,
A piezoelectric with a low mechanical quality coefficient Qm, which is excellent in heat resistance and temperature characteristics of resonance frequency, has a high electromechanical coupling coefficient Kp, and is required to have flat group delay characteristics, and is optimal as a ceramic filter for cellular, for example. It was found that a porcelain composition could be obtained, and the present invention was completed.

That is, the piezoelectric ceramic composition of the present invention comprises at least one of Ca, Sr and Ba as a metal component, N.
at least one of d, Gd, La, Pr, 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 _e O 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. However, A is Ca, S
At least one of r and Ba, 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 most suitable. In addition, a part of Pb is Nd, Gd, La, Pr, Sm.
The reason why at least one of them is replaced is that the temperature characteristic of the resonance frequency can be controlled and the mechanical quality factor Qm can be reduced at the same time, and among these, La is optimal.

The total amount of substitution of other elements of Pb is set to x + y ≦ 0.12 because the heat resistance is likely to decrease 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.

(Pb _1-xy A _x B _y ) a is 0.97
The reason why 0 ≦ a ≦ 1.030 is set 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 desirable that the amount be 0.980 ≦ a ≦ 1.010.

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

Also, the amount of (Nb _1/2 Cr _1/2 ) c is 0.1
00 ≦ c ≦ 0.700 is because 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
It is particularly desirable that the amount of _1/2 Cr _1/2 ) be 0.150 ≦ c ≦ 0.550 from the viewpoint of reducing the mechanical quality factor Qm. The present inventors have found that at least P as the metal component.
A complex perovskite type compound containing b, Zr, Ti, Nb, Yb and Co, and a system in which Cr ₂ O ₃ powder is added thereto has been previously filed (Japanese Patent Application No. 5-329252).
No.) enhances the mechanical quality factor Qm in this system by adding Cr ₂ O ₃ powder. on the other hand,
In the present application, it is weighed so as to be replaced in the form of (Nb _1/2 Cr _1/2 ), and since it is not replaced in such a form in the previous application, the mechanical quality factor Qm becomes high,
It is ideal for filters such as AM radios that require high selectivity.

Further, d of Nb amount is 0 ≦ d ≦ 0.170.
The reason is that the mechanical quality factor Qm is reduced by increasing the Nb content, but the electromechanical coupling factor Kp is rapidly reduced when d is larger 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 ]
The substitution amount e of (Ti _f Zr _1-f ) with 0.03 ≦ e ≦ 0.
The reason for setting 2 is that when e is less than 0.03, the heat resistance is not improved, and when it is more than 0.2, the electromechanical coupling coefficient Kp is rapidly reduced. [{(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 ] is 0.05 ≦ e ≦ 0.
A value of 1 is particularly desirable.

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

In the piezoelectric ceramic of the present invention, for example, PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ and Y are used 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
Weigh a predetermined amount so as to replace r _1/2 , Nb _2/3 Co _1/3 , and Nb, and replace part of Pb with Sr and La, and wet it with a ball mill for 10 to 24 hours. After mixing and then dehydrating and drying this mixture, 500 to 110
The mixture is calcined at 0 ° C. for 1 to 3 hours, the calcined product is pulverized again by a ball mill or the like, the pulverized product is mixed with an organic binder, and the mixture is granulated and then molded at a predetermined pressure to prepare a molded body. It is obtained by firing in 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} ) and Nb have excellent heat resistance, high electromechanical coupling coefficient, and low mechanical quality factor Qm.
It is possible to obtain a material having In the present invention, particularly by substituting with Nb _1/2 Cr _1/2 and Nb, the mechanical quality factor Qm can be lowered, a flat group delay characteristic can be achieved, and it can be optimized as a ceramic filter for cellular. it can.

Further, a part of Pb is mixed with at least one of Ca, Sr and Ba and Nd, Gd, La, Pr and Sm.
By substituting at least one of them, the temperature coefficient of the resonance frequency can be reduced and the mechanical quality coefficient Qm can be reduced.

[0021]

The present invention will be described in the following examples. As raw material powders, 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
_The raw material powders of ₃ , Pr ₂ O ₃ and Sm ₂ O ₃ are shown in Tables 1 and 2.
As shown in Fig. 3, part of Zr and Ti of PZT system is 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 was weighed in a predetermined amount so as to be replaced by at least one of them, wet-mixed in a ball mill for 12 hours, then dehydrated and dried, and then calcined at 900 ° C. for 3 hours, and the calcined material was again ball-milled. Crushed with.

Then, 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 have a thickness of 0.5 mm.
Disk was formed. Electrodes are formed by baking Ag paste on both main surfaces of this disk, and a DC voltage of 3 kV / mm is applied for 30 minutes in silicon oil at 80 ° C for polarization, and then electromechanical coupling coefficient and heat resistance are applied. And the temperature characteristics were evaluated.

The electromechanical coupling coefficient Kp was calculated from the values of the resonance frequency and antiresonance frequency measured with an impedance meter. Heat resistance, when tested to pass three times in succession in a reflow furnace with a peak 250 ° C., from the value of the resonant frequency Fr ₂₄ after the resonance frequency Fr ₀ test 24Hr before the test, .DELTA.fr = ( Fr ₂₄ -Fr ₀₎ / Fr ₀
The change rate ΔFr calculated using the formula of × 100 was used for evaluation. Further, the temperature coefficient T. C. fr (ppm
/ ° C) is the T.T. 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 shows the resonance frequency at + 80 ° C., −20 ° C., and + 20 ° C. respectively). The results are shown in Tables 3 and 4.
Shown in

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

From Tables 3 and 4, the porcelain composition of the present invention has a large electromechanical coupling coefficient Kp of 50% or more, a mechanical quality coefficient Qm of 150 or less, and a change in resonance frequency by heat resistance of ±. 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 substituting a part of Pb with at least one of Nd, Gd, La, Pr, and Sm, the temperature characteristic of the resonance frequency and the reduction of the mechanical quality factor Qm can be controlled at the same time.

[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 ), Nb, and part of Pb is at least one of Ca, Sr, and Ba, and
Substituting with at least one of d, Gd, La, Pr and Sm shows excellent heat resistance and temperature characteristics of resonance frequency, high electromechanical coupling coefficient and low mechanical quality coefficient Qm. An element such as a surface mount piezoelectric component that can obtain a material and exhibits stable characteristics against temperature changes,
For example, an optimum piezoelectric ceramic composition can be obtained as an element such as a filter or a resonator, particularly as a ceramic filter for cellular.

Front page continued (72) Inventor Kenichi Yoshimura 1-4 Yamashita-cho, Kokubun-shi, Kagoshima Kyocera Stock Company Research Institute

Claims (1)

[Claims] 1. At least one of Ca, Sr and Ba as a metal component, 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, 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, Ba B: Nd, Gd, A piezoelectric ceramic composition characterized by satisfying at least one of La, Pr and Sm.