JPH08231270A - Piezoelectric composition - Google Patents

Abstract

(57) [Summary] [Object] To provide a piezoelectric ceramic composition having a large electromechanical coupling coefficient Kp, a small mechanical quality coefficient Qm, a small relative permittivity εr, and excellent heat resistance. [Structure] The composition formula based on the atomic ratio of metal elements (Pb _{1-xy
L x M y) a (Nb} b Cr c Y d Al e) f Ti g Zr
_1-fg O ₃ (where L is at least one of Sr and Ba, M is La, Ce, Gd, Nd, Sm, Pr, Eu
At least one of the above), x, y, a,
b, c, d, e, f, g are 0.01 ≦ x ≦ 0.08,
0.002 ≦ y ≦ 0.05, 0.95 ≦ a ≦ 1.05,
0.46 ≦ b ≦ 0.60, 0.11 ≦ c ≦ 0.42,
0.02 ≦ d ≦ 0.31, 0.02 ≦ e ≦ 0.18,
0.02 ≦ f ≦ 0.15, 0.46 ≦ g ≦ 0.52, b
This satisfies + c + d + e = 1.00.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a piezoelectric ceramic composition used in, 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 sensor, and a piezoelectric actuator. Related to things, especially analog cellular phones,
The present invention relates to a piezoelectric ceramic composition suitable for a second intermediate frequency filter of a mobile communication device such as a digital cellular phone.

[0002]

2. Description of the Related Art Conventionally, products using a piezoelectric ceramic composition include, for example, ceramic filters, ceramic resonators, ultrasonic applied vibrators, piezoelectric buzzers, piezoelectric ignition units, ultrasonic motors, piezoelectric fans, piezoelectric sensors, piezoelectric actuators. Etc.

Here, as elements such as ceramic filters and ceramic resonators, PbZrO ₃ -PbTi is used.
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 or Pb (Nb
Piezoelectric properties have been improved by adding or substituting complex perovskite type oxides such as _2/3 Mg _1/3 ) O ₃ and Pb (Nb _2/3 Co _1/3 ) O ₃ .

Conventionally, Pb (Nb _2/3 Co) has been used as a piezoelectric ceramic composition having a large electromechanical coupling coefficient Kp and excellent piezoelectricity.
_2/3) O ₃ -PbZrO ₃ -PbTiO ₃ system composition is known.

On the other hand, in recent years, even piezoelectric components such as ceramic filters and ceramic resonators have been required to meet various conditions so that they can be mounted on the surface of a substrate or the like. ,
When the component is reflow-soldered on the substrate, the component mounted on the substrate is exposed to a high temperature of about 230 ° C. to 300 ° C., so that the piezoelectric element incorporated in the component is also required to have heat resistance.

Further, for example, in a filter of several hundreds of kilohertz band which utilizes the spreading vibration of piezoelectric ceramics, the electromechanical coupling coefficient Kp is large and the mechanical quality coefficient Q is large.
In order to reduce m and increase the guaranteed attenuation amount, a material having a small relative permittivity εr and excellent heat resistance is required.
Particularly in digital cellular phones, it is required to stabilize the group delay characteristics of the filter within the guaranteed band in order to prevent noise from adjacent channels.

[0007]

However, the above-mentioned conventional Pb (Nb _2/3 Co _1/3 ) O ₃ -PbZrO described above is used.
_{The 3-} PbTiO ₃ -based porcelain composition has low heat resistance and has large changes in piezoelectric characteristics and resonance frequency before and after reflow soldering, which has been a practical problem. In addition, since the piezoelectric characteristics and the resonance frequency change greatly after the thermal shock test, there is a problem that stable transmission / reception cannot be performed due to changes in the element characteristics when used in filters for vehicle-mounted communication devices, etc., where environmental changes are drastic. there were.

Further, since the relative permittivity εr is as high as about 1800, it is necessary to form a partial electrode to form an element, and the mechanical delay coefficient Qm is large, so that the group delay characteristic is poor. was there.

The piezoelectric ceramic composition of the present invention has a large electromechanical coupling coefficient Kp and a small mechanical quality coefficient Qm,
An object of the present invention is to provide a piezoelectric ceramic composition having a small relative permittivity εr and excellent heat resistance.

[0010]

The inventors of the present invention have proposed that Pb,
Zr, Ti, Nb, Cr, Y, Al, and La, C
A complex perovskite type compound containing at least one of e, Gd, Nd, Sm, Pr and Eu, and at least one of Sr and Ba and having a constant composition has a large electromechanical coupling coefficient Kp, The inventors have found that it is possible to obtain a piezoelectric ceramic composition having a small mechanical quality factor Qm, a small relative permittivity εr, and excellent heat resistance and thermal shock resistance, and arrived at the present invention. That is, the piezoelectric ceramic composition of the present invention contains Pb, Zr, Ti, Nb as metal components,
Cr, Y, Al and La, Ce, Gd, Nd, Sm,
Pr, at least one of Eu, and Sr, at least one a perovskite compound including a composition formula by the atomic ratio of these metal elements _{(Pb 1-xy L x M} y) of the Ba _a (Nb _b Cr _c Y _d Al _e )
_f Ti _g Zr _1-fg O ₃ (where L is at least one of Sr and Ba and M is at least one of La, Ce, Gd, Nd, Sm, Pr and Eu), x, y, a, b, c, d,
e, f, g are 0.01 ≦ x ≦ 0.08, 0.002 ≦ y
≦ 0.05, 0.95 ≦ a ≦ 1.05, 0.46 ≦ b ≦
0.60, 0.11 ≦ c ≦ 0.42, 0.02 ≦ d ≦
0.31, 0.02 ≦ e ≦ 0.18, 0.02 ≦ f ≦
0.15, 0.46 ≦ g ≦ 0.52, b + c + d + e =
It satisfies 1.00.

Here, the reason why a, b, c, d, e, f, g are set in the above range will be described. The reason for setting a of the A site to 0.95 ≦ a ≦ 1.05 is that a is 0.95.
This is because if it is less than 1.05 or more than 1.05, the electromechanical coupling coefficient Kp is lowered and the heat resistance is lowered. It is particularly desirable that a of the A site is 0.99 ≦ a ≦ 1.01.

Further, b of the Nb amount is 0.46≤b≤0.6
The reason for setting 0 is that when b is less than 0.46, the mechanical quality factor Q
This is because when m is large and b is larger than 0.60, the relative dielectric constant εr is large and the heat resistance is lowered.
It is desirable that the Nb amount b be 0.52 ≦ b ≦ 0.58.

Further, the Cr content c is 0.11≤c≤0.
The reason for setting 42 is that when c is less than 0.11, heat resistance decreases, and when it is greater than 0.42, the mechanical quality factor Qm increases and the group delay time characteristic decreases. It is desirable that the Cr content c be 0.22 ≦ c ≦ 0.26.

The d of Y amount is set to 0.02 ≦ d ≦ 0.31 because the mechanical quality factor Qm is greatly increased when d is less than 0.02, and the relative dielectric constant εr is greater than 0.31. Is high and heat resistance is deteriorated. D of Y amount is 0.02
It is desirable that ≦ d ≦ 0.17.

The amount e of Al is set to 0.02≤e≤0.18 because the relative permittivity εr increases when e is less than 0.02 and the mechanical quality factor Qm increases when e is more than 0.18. Because it becomes too big. The Al amount e is 0.02 ≦ e ≦
It is desirable to set it to 0.12.

The substitution amount f of (Nb _b Cr _c Y _d Al _e ) at the B site is set to 0.02 ≦ f ≦ 0.15 because the electromechanical coupling coefficient Kp decreases when f is less than 0.02. On the other hand, if it is larger than 0.15, the relative permittivity εr becomes large and the heat resistance sharply decreases. (Nb _b Cr _c
The substitution amount f of B _d site of Y _d Al _e ) is 0.05 ≦ f ≦
It is desirable to set it to 0.07.

The substitution amount g of Ti by Zr is 0.46 ≦ g ≦
The reason for setting 0.52 is that when g is less than 0.46, the relative permittivity εr is large and the heat resistance is lowered, and when it is larger than 0.52, the electromechanical coupling coefficient Kp is too low. is there. The substitution amount g of Ti by Zr is 0.48 ≦ g ≦ 0.
It is preferably 51.

Substitution amount x of L (Sr and / or Ba) x
Is set to 0.01 ≦ x ≦ 0.08 because the electromechanical coupling coefficient Kp is small when x is less than 0.01 and the relative dielectric constant εr is large when x is greater than 0.08. is there. Substitution amount x of Sr and / or Ba is 0.01 ≦ x
It is desirable that ≦ 0.015. In the present invention, especially S
Substitution with r is desirable.

M (La, Ce, Gd, Nd, Sm, P
The substitution amount y of at least one of r and Eu) is 0.00
2 ≦ y ≦ 0.05 is set so that when y is less than 0.002, the electromechanical coupling coefficient Kp becomes small, and when y is larger than 0.05, the relative dielectric constant εr is high and the heat resistance is deteriorated. This is because The substitution amount y of M is 0.003 ≦ y ≦ 0.0
A value of 05 is desirable.

The piezoelectric ceramic composition of the present invention has a composition formula (Pb _{1- xy} L _x M _y ) _a based on the atomic ratio of metal elements.
(Nb _b Cr _c Y _d Al _e ) _f Ti _g Zr _1-fg O ₃
(Here, L is at least one of Sr and Ba, and M is at least one of La, Gd, Nd, Sm, and Pr)
, X, y, a, b, c, d, e, f, g are 0.01 ≦ x ≦ 0.015, 0.003 ≦ y ≦ 0.00
5, 0.99 ≦ a ≦ 1.01, 0.52 ≦ b ≦ 0.5
8, 0.22 ≦ c ≦ 0.26, 0.02 ≦ d ≦ 0.1
7, 0.02 ≦ e ≦ 0.12, 0.05 ≦ f ≦ 0.0
7, 0.48 ≦ g ≦ 0.51 is preferably satisfied.

The piezoelectric ceramic of the present invention can be manufactured, for example, by using PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ and C as raw materials.
r ₂ O ₃ , Y ₂ O ₃ , Al ₂ O ₃ and La, Ce, G
At least one oxide of d, Nd, Sm, Pr, and Eu, and each raw material powder of SrCO ₃ and / or BaCO ₃ are weighed in a predetermined amount and wet-mixed with a ball mill for 10 to 24 hours, and then this mixture is mixed. Is dehydrated and dried, and then calcined at 800 to 1000 ° C. for 1 to 3 hours, and the calcined product is pulverized again by a ball mill or the like.

Then, an organic binder is mixed with the crushed product, and after granulation, the product is molded at a predetermined pressure to prepare a molded product, which is 0.5 to 0.5 at 1200 to 1350 ° C. in the atmosphere.
It is obtained by firing for 4 hours.

[0023]

In the piezoelectric ceramic composition of the present invention, PbZrO ₃
Part of Zr and Ti of the PbTiO ₃ -based porcelain composition is replaced with Nb, Cr, Y, and Al, and part of Pb is Sr and / or Ba, La, Ce, Gd, Nd, Sm, P.
By substituting at least one of r and Eu,
High electromechanical coupling factor Kp, low mechanical quality factor Qm,
It is possible to exhibit a low relative permittivity εr and improve heat resistance.

[0024]

The present invention will be described in the following examples. As raw material powder, PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ ,
Cr ₂ O ₃ , Y ₂ O ₃ , Al ₂ O ₃ , SrCO ₃ and / or BaCO ₃ , La, Ce, Gd, Nd, Sm,
A predetermined amount of each raw material powder of at least one oxide of Pr and Eu was weighed so as to have a composition shown in Tables 1 to 3, wet-mixed with a ball mill for 12 hours or more, and then,
After this mixture was dehydrated and dried, it was calcined at 950 ° C. for 3 hours, and the calcined product was pulverized again with a ball mill.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

Then, an organic binder (P
VA) was mixed and granulated. The obtained powder was press-molded at a pressure of 1.5 to 2 t / cm ² into a disk shape having a diameter of 23 mm and a thickness of 2 mm. Further, these molded bodies were sealed in a container made of MgO or the like and placed in the atmosphere.
Baking was performed at 00 to 1350 ° C. for 2 hours.

The obtained sintered body is polished to have a thickness of 0.5 mm.
Disk was formed. Electrodes were formed by baking Ag paste on both principal surfaces of this disc at 600 ° C., and a DC voltage of 3 kv / mm was applied for 30 minutes in silicon oil at 80 ° C. for polarization treatment, followed by electromechanical coupling. The coefficient Kp, the mechanical quality coefficient Qm, and the heat resistance were evaluated. Also, the relative permittivity ε
r was calculated and calculated from the capacity obtained by the impedance meter. Electromechanical coupling coefficient Kp, mechanical quality coefficient Qm
Was calculated from the values of the resonance frequency and anti-resonance frequency measured by an impedance meter. Heat resistance is 250 ° C
From the values of the resonance frequency fr ₁ before the test and the resonance frequency fr ₂ after the test when the test is performed in which the solder reflow furnace having the peak of 3 times is continuously passed, fra = | (fr ₂ −fr ₁ ) | / Fr ₁ × 100 The rate of change fra calculated using the equation was evaluated. The results are shown in Tables 4 to 6.

[0030]

[Table 4]

[0031]

[Table 5]

[0032]

[Table 6]

The samples No. 55 in Tables 1 to 3 are M
Gd is used as the sample, Sm is used as the M in the sample No. 56, Pr is used as the M in the sample No. 57, and the sample No. 58 is used.
Uses Nd as M, Sample No. 34 uses La as 0.003 and Ce as 0.002 as M, and has Sample No. 3
5 used Eu as M. In other samples, La was used as M.

In Sample No. 70, Ba was used as L. In Sample No. 33, Ba was 0.007 and Sr was 0.008 as L, and Sr was used as L for the others.

From these Tables 4 to 6, the piezoelectric ceramic composition of the present invention has a large electromechanical coupling coefficient Kp of 40% or more, a low mechanical quality factor Qm of 200 or less, and a relative dielectric constant of 1500 or less. It can be seen that it is low, and the change in fra due to the heat resistance test is as small as ± 0.1% or less.

[0036]

As described in detail above, according to the present invention, P
Part of Zr and Ti of the bZrO ₃ —PbTiO ₃ system porcelain composition is replaced with Nb, Cr, Y, and Al, and part of Pb is Sr and / or Ba or La, Ce, Gd, N.
By substituting at least one of d, Sm, Pr, and Eu, a high electromechanical coupling coefficient Kp, a low mechanical quality coefficient Qm, a low relative dielectric constant εr, and heat resistance can be improved. It is possible to obtain a piezoelectric ceramic composition that is effectively used as an element such as a mounting piezoelectric component.

Claims (1)

[Claims] 1. A metal component of Pb, Zr, Ti, Nb,
Cr, Y, Al and La, Ce, Gd, Nd, Sm,
Pr, at least one of Eu, and Sr, at least one a perovskite compound including a composition formula by the atomic ratio of these metal elements _{(Pb 1-xy L x M} y) of the Ba _a (Nb _b Cr _c Y _d Al _e )
_f Ti _g Zr _1-fg O ₃ (where L is at least one of Sr and Ba and M is at least one of La, Ce, Gd, Nd, Sm, Pr and Eu), x, y, a, b, c, d,
e, f and g are 0.01 ≤ x ≤ 0.08 0.002 ≤ y ≤ 0.05 0.95 ≤ a ≤ 1.05 0.46 ≤ b ≤ 0.60 0.11 ≤ c ≤ 0. 42 0.02 ≤ d ≤ 0.31 0.02 ≤ e ≤ 0.18 0.02 ≤ f ≤ 0.15 0.46 ≤ g ≤ 0.52 b + c + d + e = 1.00 Piezoelectric composition.