JPH0546641B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a ferroelectric piezoelectric ceramic composition used, for example, as a material for an element that converts electrical energy into mechanical energy and mechanical energy into electrical energy. (Prior art) A morphotopic phase transition (MPB) exists in a solid solution of PbZ _r O ₃ −PbT _i O ₃ (PZT), and this MPB
After it was revealed that piezoelectricity peaks near the surface, the scope of use of ceramics as piezoelectric materials has expanded significantly. After this, as a substitute for the above PZT, a three-component system of Pb(Mg _1/3 Nb _2/3 )O ₃ −PbT _i O ₃ −PbZ _r O ₃
(PCM: product name) was developed, and this PCM is MPB
It became even more versatile as it was expanded from points to lines. Various attempts have been made to improve the characteristics of the three-component ceramic composition. For example, Tokkosho
In the ferroelectric piezoelectric ceramic composition disclosed in No. 44-17103, some of the Pb atoms in Pb(Mg _1/3 Nb _2/3 ) O ₃ −PbZ _r O ₃ −PbT _i O ₃ are replaced with S _r . and
With such a composition, it is possible to obtain an electromechanical transducer element with a large electromechanical coupling coefficient and dielectric constant, and a small resonance resistance. (Problems to be Solved by the Invention) According to the above-mentioned ferroelectric piezoelectric ceramic composition, a wide range of constants can be selected depending on the purpose of use,
The applications of piezoelectric ceramics will continue to expand,
Depending on the application, the above composition may not provide sufficient piezoelectric properties. For example, when piezoelectric ceramics are used as actuators, the
RD (relative density), ε (permittivity), Kp (radial coupling coefficient) and d ₃₁ (piezoelectric strain constant) are required, and it is expected that piezoelectric ceramics will be laminated in the future, and in this case, It will be necessary to fire at a lower temperature than currently available. (Means for Solving the Problems) In order to solve the above problems, the present invention provides Pb (Mg _1/3
Nb _2/3 ) O ₃ −PbT _i O ₃ −PbZ _r O ₃ −Z _o O−B _i2 O ₃ based porcelain composition, or Pb(Mg _1/3 Nb _2/3 )O ₃ −PbT _i
A predetermined amount of S _n2 O ₃ (samarium oxide) was added to the O ₃ -PbZ _r O ₃ -Z _o O-B _i2 O ₃ -S _o O-based ceramic composition. (Function) By adding S _n2 O ₃ together with B _i2 O ₃ or together with B _i2 O ₃ and S _o O, a ceramic composition having excellent various properties can be obtained. (Example) The present invention is divided into a first invention and a second invention, and in the example, experiments were conducted with the compositions other than S _n2 O ₃ fixed. That is, for the first invention, 37.5Pb (Mg _1/3 Nb _2/3 ) O ₃ +32.5PbT _i O ₃ +25.0PbZ _r O ₃ +5.0S _r T _i O ₃ +2.0Z _o O +1.0B _i2 O ₃ +XS _n2 O ₃ ... However, X = 0, 0.01, 0.02, 0.05, 0.10, 0.15, 0.20, 0.30, 0.50. Regarding the second invention, 37.5Pb (Mg _1/3 Nb _2/3 ) O ₃ +32.5PbT _i O ₃ +25.0PbZ _r O ₃ +5S _r T _i O ₃ +2.0Z _o O +1.0B _i2 O ₃ +2 .S _o O＋XS _n2 O ₃ … However, X=0, 0.01, 0.02, 0.05, 0.10,
0.15, 0.20, 0.30, 0.50. Further, although only for the first invention, experiments were also conducted regarding the addition ratio of B _i2 O ₃ as shown in the following equation. 37.5Pb (Mg _1/3 Nb _2/3 ) O ₃ +32.5PbT _i O ₃ +25.0PbZ _r O ₃ +5.0S _r T _i O ₃ +2.0Z _o O +0.1S _n2 O ₃ +XB _i2 O ₃ … However, X=0, 0.2, 0.5, 1.0, 2.0, 3.0, 5.0
To create a ceramic (element) from a composition having the above composition, the following steps are performed. First, prepare an oxide or carbonate with a chemical purity of 98% or higher, weigh it as a raw material so that it has the compounding composition of each formula above, and perform wet mixing for 12 hours in a rubber-lined ball mill to create a homogeneous mixture. shall be.
After drying this mixture, it was pre-calcined at 1020°C for 2 hours, and then wet-pulverized in a ball mill for 12 hours. After this, the pulverized material is dried, a small amount of organic binder is added, and the granulated material is pressurized.
Formed into a disc with a diameter of 22mm and a thickness of 2mm at 1000Kg/ ^cm2 .
This disk is held at a predetermined temperature for 2 hours in a closed container of an alumina crucible and fired. Here, the predetermined temperature refers to 1240°C, 1250°C, 1260°C in the first invention.
℃ and 1270℃, and in the case of the second invention,
There were four levels: 1220°C, 1230°C, 1240°C and 1250°C. Next, after polishing the fired disk, silver electrodes are coated on both sides of the disk and baked, and then immersed in silicone oil and exposed to a DC electric field of 1.6 to 1.8 kv/mm at room temperature for 20 minutes.
The desired porcelain is obtained by applying the voltage for a minute and polarizing it. The following [Table] shows the S _n2 O ₃ of the porcelain according to the present invention obtained as described above and the porcelain of other compositions.
It shows the relationship between mol% and various properties, [Table 1]
[Table 4] to [Table 4] show the results of the experimental examples included in the first invention, [Table 5] to [Table 8] show the results included in the second invention, and [Table 9] to [Table 11] show the results of the _experimental examples included in the first invention. [ _Table 12] to [Table 16] show the results of comparative examples, [Table 17] to [Table 20] show the results of comparative examples, and [Table 21] to [Table 20] show the results of comparative examples. Table 24] shows the results of the comparative examples.
Pb(Mg _1/3 Nb _2/3 )O ₃ −PbT _i O ₃ −PbZ _r O ₃ −S _r T _i O ₃
S _n2 O ₃ was added to the ceramic composition of the system, and Pb(Mg _1/3 Nb _2/3 ) O ₃ −PbT _i O ₃ − was added for the comparative example.
For PbZ _r O ₃ −S _r T _i O ₃ −Z _o O-based porcelain compositions
Added S _n2 O ₃ and further added Pb for comparative example.
(Mg _1/3 Nb _2/3 )O ₃ −PbT _i O ₃ −S _r T _i O ₃ −Z _o O−S _o
S _n2 O ₃ was added to the O-based porcelain composition. Furthermore, the measured values were those close to the average value among samples (4 or more) prepared under the same conditions, and the meanings of the symbols in the table are as follows. Density (Kg/m ³ ): The larger this value is, the better the bending strength is. ε: dielectric constant. The larger this value is, the better the properties of the piezoelectric element are. Kp (%): Radial coupling coefficient. As with the dielectric constant, a larger value is better. d ₃₁ (×10 ^-12 V・m/N): Strain in the direction perpendicular to the direction of application when voltage is applied to the element. The larger this value, the better the characteristics when used as an actuator. Qm: Electromechanical quality factor. It is preferable that this value is larger. tanδ: dielectric loss. It is preferable that this value is smaller. Y11 (×10 ¹⁰ N/m ² ): Young's modulus. When used as a piezoelectric element, it is preferably within a predetermined range.

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

[Table] The effects of the present invention are summarized as follows. Pb(Mg _1/3 Nb _2/3 )O ₃ −PbTiO ₃ −PbZrO ₃ −
Some of the Pb atoms in the ZnO−Bi ₂ O ₃ based ceramic composition
Porcelain compositions in which the amount of Sm ₂ O ₃ added is 0.02 mol% or less with respect to those substituted with Sr atoms;
As is clear from [Tables 1] to [Table 4], a ceramic composition containing 0.4 mol% or more, that is, a ceramic composition that is outside the scope of the first invention of the present application, has a dielectric constant (ε), a coupling coefficient ( Kp) and piezoelectric strain constant (d ₃₁ ), the amount of Sm ₂ O ₃ added is 0.02 to 0.4 mol.
%, these values tend to be lower than those of the ceramic composition according to the first invention of the present application. Pb(Mg _1/3 Nb _2/3 )O ₃ −PbTiO ₃ −PbZrO ₃ −
In contrast to ZnO−Bi ₂ O ₃ −SnO ceramic compositions in which some of the Pb atoms are replaced with Sr atoms, Sm ₂
Porcelain compositions in which the amount of O ₃ added is 0.02 mol% or less and porcelain compositions in which the amount of O 3 added is 0.4 mol% or more, that is, ceramic compositions that are outside the scope of the first invention of the present application, are:
As is clear from [Tables 5] to [Table 9], the addition amount of Sm ₂ O ₃ was varied from 0.02 to 0.02 for dielectric constant (ε), coupling coefficient (Kp), and piezoelectric strain constant (d ₃₁ ).
These values tend to be lower than the ceramic composition according to the second invention of the present application, which has a content of 0.4 mol %. For a Pb (Mg _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ -PbZrO _3- based ceramic composition in which some of the Pb atoms were replaced with Sr atoms, the amount of Sm ₂ O ₃ added was 0.0. ~
As is clear from [Table 12] to [Table 16], the ceramic composition containing 0.5 mol% of ZnO and Bi ₂ O ₃
The porcelain composition of the first invention of the present application, or
Compared to the ceramic composition of the second invention of the present application containing ZnO, Bi ₂ O ₃ and SnO, the values of dielectric constant (ε), coupling coefficient (Kp) and piezoelectric strain constant (d ₃₁ ) tend to be lower. . Pb(Mg _1/3 Nb _2/3 )O ₃ −PbTiO ₃ −PbZrO ₃ −
The amount of Sm ₂ O ₃ added to a ZnO-based ceramic composition in which some of the Pb atoms are replaced with Sr atoms is
The porcelain composition containing 0.0 to 0.5 mol% is [Table 17]
As is clear from [Table 20], the ceramic composition of the first invention of the present application containing Bi ₂ O ₃ or Bi ₂ O ₃
The dielectric constant (ε), coupling coefficient (Kp), and piezoelectric strain constant (d ₃₁ ) tend to be lower than the ceramic composition of the second invention of the present application containing SnO and SnO. Pb(Mg _1/3 Nb _2/3 )O ₃ −PbTiO ₃ −PbZrO ₃ −
Some of the Pb atoms in the ZnO−SnO ceramic composition
Porcelain compositions with Sm ₂ O ₃ added in an amount of 0.0 to 0.5 mol% relative to those substituted with Sr atoms,
As is clear from [Table 21] to [Table 24], Bi ₂
The dielectric constant (ε) value tends to be lower than the ceramic composition of the first invention or the second invention of the present application containing O ₃ . The preferable addition ratio of Bi ₂ O ₃ to increase the dielectric constant is as shown in [Table 9]
1.0 to 3.0mol as clear from [Table 11]
%. As described above, the ceramic composition according to the present invention can lower the firing temperature and exhibits excellent effects in terms of dielectric constant, coupling coefficient, and piezoelectric strain constant.

Claims (1)

[Claims] 1 Pb(Mg _1/3 Nb _2/3 )O ₃ −PbT _i O ₃ −PbZ _r O ₃ −Z _o
0.02 _to 0.4 mol of S _n2 O 3 is added to the O-B _i2 O ₃ based ceramic composition in which some of the Pb atoms are replaced with Sr atoms.
% of a ferroelectric piezoelectric ceramic composition. 2 Pb(Mg _1/3 Nb _2/3 ) O ₃ −PbT _i O ₃ −PbZ _r O ₃ −Z _o
O-B _i2 O ₃ -S _o For O-based ceramic compositions in which some of the Pb atoms are replaced with Sr atoms, S _n2 O ₃ is added from 0.02 to
A ferroelectric piezoelectric ceramic composition characterized by adding 0.4 mol%.