JPH0826825A - Piezoelectric porcelain composition for actuator - Google Patents

Abstract

PURPOSE:To produce a piezoelectric porcelain composition having a high strength. CONSTITUTION:This piezoelectric porcelain composition for actuator has a composition represented by the following formula: Pb1-a-b-c-dLaaPbBacSrd(SrxTi1-x-y--zNyMz)O3 [P is at least one or more of Pr, Nd and Sm; N is at least one or more of In, Fe, Co and Ga; M is at least one or more of Sb and Nb; 0.0025<= a 0.010; 0.005<= d <=0.020; 0.010<= c <=0.025; 0.050<= d <=0.150; 0.540<= x <=0.560; 0.002<= y <=0.005; 0.005<= z <=0.030].

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, and more particularly to a piezoelectric ceramic composition which can be advantageously used in a piezoelectric element such as an actuator.

[0002]

BACKGROUND ART Studies on piezoelectric ceramic compositions have been carried out for a long time, and products using such piezoelectric ceramic compositions are widely used in various fields. Examples of products using such piezoelectric ceramic compositions include ceramic filters, glass delay lines, ultrasonic transducers, piezoelectric buzzers, piezoelectric ignition units, ultrasonic motors, piezoelectric fans, piezoelectric sensors, and piezoelectric actuators. Can be mentioned. here,
The piezoelectric actuator utilizes a displacement and force generated through a piezoelectric phenomenon as a mechanical drive source, and is one of the ones that have recently attracted attention in the field of mechatronics. Since this piezoelectric actuator is a solid-state element that utilizes the piezoelectric effect, it consumes less power, has a faster response speed, and has a larger amount of displacement than conventional electromagnetic actuators that have a coil wound around a magnetic body. It has excellent features such as low heat generation, small size and weight.

Various types of piezoelectric ceramic compositions are known as those which can be used for the above-mentioned piezoelectric element. For example, many piezoelectric ceramic compositions have been known, starting from the technique of adding a simple oxide to PZT ceramics described in Japanese Patent No. 275421 issued in 1960. U.S. Pat. No. 2,911,370 describes adding elements such as niobium (Nb), tantalum (Ta), and rare earth metals to PZT-based ceramics, or partially adding Pb to strontium (S
It is taught that by substituting with an element of alkaline earth metal such as r) or calcium (Ca), the piezoelectric constant and dielectric constant of the resulting composition are increased. Japanese Unexamined Patent Publication No. 62-298192 teaches a piezoelectric ceramic composition used for an actuator element, which has a basic composition of Pb (Zr _x Ti _y ) O ₃ , and this composition is used as a material for an actuator. It has been reported that it has a usable piezoelectric strain constant and has an extremely low dielectric loss.

Further, Japanese Patent Laid-Open No. 4-260662 discloses Pb.
_0.89-x Sr _0.11 Ba _x (Zr _a Ti _b Sb _c ) O ₃ (where 0.01 ≦ x
≤0.04, 0.545 ≤a ≤0.555, 0.445 ≤b ≤0.455, 0.
005 ≤ c ≤ 0.015, a + b + c = 1), high piezoelectric properties, in particular high Curie temperature, suitable for piezoelectric actuators.

This composition has a three-point bending strength of 75 MPa, and when it is subjected to a repeated drive test at 100 ° C. with a voltage of 0 to 800 V, cracking occurs. this is,
This is because the strength is insufficient and domain switching easily occurs due to the repeated drive test.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of conventional piezoelectric materials, and provides a piezoelectric ceramic composition for an actuator, which has high piezoelectric characteristics, especially a high Curie temperature, and high strength. To do.

[0007]

The piezoelectric ceramic composition of the present invention has a composition represented by the following formula: Pb _1-abcd La _a P _b Ba _c Sr _d (Zr _x Ti
_1-xyz N _y M _z ) O ₃ (wherein P is at least one of Pr, Nd and Sm, N is at least one of In, Fe, Co and Ga, and M is at least one of Sb and Nb, and 0.002 ≤ a ≤ 0.010, 0.1.
005 ≤ b ≤ 0.020, 0.010 ≤ c ≤ 0.025, 0.050 ≤ d ≤
0.150, 0.540 ≤ x ≤ 0.560, 0.002 ≤ y ≤ 0.005, 0.
005 ≦ z ≦ 0.030).

Further, the piezoelectric ceramic composition of the present invention has the following formula
Composition represented by: Pb_{(1 + e) -abcd}La_aP_bBa_cSr_d(Zr_xT
i_1-xyzN_yM_z) O ₃ (In the above formula, P is at least Pr, Nd, or Sm.
Is also one or more, and N is In, Fe, Co, or Ga.
At least one kind, and M is Sb, Nb
And at least one kind, and 0.002 ≤ a ≤ 0.010, 0.
005 ≤ b ≤ 0.020, 0.010 ≤ c ≤ 0.025, 0.050 ≤ d ≤
0.150, 0.01 ≤ e ≤ 0.05, 0.540 ≤ x ≤ 0.560, 0.002
≤ y ≤ 0.005, 0.005 ≤ z ≤ 0.030)
And are characterized by.

[0009]

The piezoelectric ceramic composition of the present invention is a conventional piezoelectric ceramic assembly.
Product, formula, Pb_1-abBa _aSr_b(Zr_1-xyTi_xzIn
_zSb_y) O₃In the composition represented by, a part of the Pb component
At least one of La, Pr, Nd, and Sm
And are replaced at the same time. Obtained by this replacement
The crystal structure of the composition is refined and the strength is significantly improved.
Further, the Curie temperature is improved.

Further, in the composition of the present invention, PbO
By increasing the amount in the range of 0.01 to 0.05, excessive PbO promotes sintering, so that the firing temperature can be lowered, the crystal structure can be further refined, and the strength can be further improved.

[0011]

Supplementary Explanation of Means for Solving the Problems The piezoelectric ceramic composition of the present invention can be used especially for piezoelectric actuators of automobiles and other piezoelectric elements. For example, a piezoelectric actuator is formed by using a known method, for example, by laminating two thin plates of a piezoelectric material to form a bimorph type structure, or by laminating several tens to several hundreds of thin plates of the piezoelectric material, and one of them. It can be manufactured by alternately stacking and fixing one sheet so that the polarization in the thickness direction is reversed, to form a laminated structure.

In the composition of the present invention, La has the effect of refining the crystal, and its amount is 0.002 ≤ a ≤ 0.0010,
That is, it is 0.2 to 1 mol%. If the amount of La is less than this lower limit, there is no effect of refining, and if it exceeds the upper limit, the effect of refining is saturated and the electrical properties of the composition deteriorate.

The amount of Ba is 0.010≤c≤0.025, that is, 1 to 2.5 mol%. If the amount of Ba is less than this lower limit, the electrical characteristics will deteriorate, and if it exceeds the upper limit, the Curie temperature will decrease. The amount of Sr is 0.050 ≤ d ≤ 0.150, that is, 5
~ 15 mol%. If the amount of Sr is outside this range, the electrical characteristics will deteriorate. The amount of Zr is 0.540 ≤ x ≤ 0.56
0, that is, 54 to 56 mol%. With a Zr content in this range, a tetragonal composition having high displacement characteristics can be obtained.

In the composition of the present invention, Pr, Nd, S
The amount of P, which is at least one of m, is 0.005 ≤ b
≦ 0.020, that is, 0.5 to 2 mol%, In, F
The amount of N, which is at least one of e, Co, and Ga, is 0.002 ≤ y ≤ 0.005, that is, 0.2 to 0.5 mol%, and the amount of M, which is at least one of Sb and Nb, is 0.005 ≤. z ≦ 0.030, that is, 0.5 to 3 mol%
Is. Within this range, the crystal structure of the composition becomes finer, the strength is significantly improved, and the Curie temperature is improved.

[0015]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 Pb _1-abcd La _a Pr _b Ba _c Sr _d (Zr _x Ti
In the composition formula represented by _1-xyz In _y Sb _z ) O ₃ , a = 0.005, c = 0.016, d = 0.11, x = 0.55, y
= 0.003, z = 0.01, and the raw materials PbO, BaCO ₃ , SrCO ₃ , and Zr are used so that b has the values shown in Table 1 below.
O ₂ , TiO ₂ , In ₂ O ₃ , Sb ₂ O ₅ , La ₂ O ₃
And Pr ₆ O ₁₁ are weighed in predetermined amounts, and z = 0.002, 0.
In ₂ O ₃ was weighed to give 003 and 0.005 mol and they were wet mixed in a ball mill for 40 hours.
Then, the obtained mixed powder was dried, calcined at 800 ° C. for 2 hours, pulverized again in a ball mill for 48 hours, and dried.

To the mixed powder thus obtained, 1.5% by weight of PVA (polyvinyl alcohol) as a binder was added, and the diameter was 20 mm and the thickness was 1 mm at a molding pressure of 1000 kg / cm ^2.
Formed into a circular plate. By sintering this at 1200 ° C. for 2 hours, piezoelectric element pellets having different amounts of Pr substitution were manufactured.

Silver electrodes were baked on both sides of the pellet by a conventional method, and a polarization treatment was performed by applying a voltage of DC 4 kV / cm in 100 ° C. silicon oil.

The relative permittivity (ε _r ), electromechanical coupling coefficient (Kp), Curie temperature (Tc) and three-point bending strength (σ _3b , φ15 mm, t = 0.5 mm) of each of the obtained piezoelectric pellets
Bending strength with a span of 10 mm) was measured for the pellets. Table 1 shows the results.

[0020]

[Table 1]

As is clear from this table, the strength (σ _3b ) when the Pr substitution amount is 1.0 mol%, that is, when b = 0.01.
And the Curie temperature (Tc) were both maximum. The Pr substitution amount that improves the strength and the Curie temperature at the same time is 0.005
≦ b ≦ 0.02. For comparison, the amount of La added was set to 0, that is, a = 0, and the piezoelectric pellet was manufactured by substituting only with Pr, and the strength and the Curie temperature were measured. The results are shown in Table 2.

[0022]

[Table 2]

In this sample, although the strength was slightly improved, the Curie temperature was lowered. Further, as a result of substituting only La with the Pr addition amount set to 0, that is, b = 0,
The effect of improving the strength and improving the Curie temperature of the obtained sample was hardly obtained. Furthermore, even if Nd or Sm was substituted for Pr, the strength and Curie temperature were improved in the same range as Pr.

The composition of the present invention shown in Table 1 (Pr substitution amount,
Piezoelectric pellets manufactured from b = 0.5 to 2.0) were repeatedly driven under the following conditions. Repeated drive test conditions Temperature: 100 ° C. Voltage: −200 to 600 V Preset load: 20 MPa Sample shape: pellet, φ16 mm, thickness 0.5 mm This pellet did not crack even after driving 1 × 10 ⁸ times. On the other hand, Pr substitution amount, b = 0, 0.3, 2.3 and
With the composition of 2.5 and the conventional material, 40% of the samples cracked under the same test conditions.

Example 2 Pb _1-abcd La _a Pr _b Ba _c Sr _d (Zr _x Ti
In the composition formula represented by _1-xyz In _y Sb _z ) O ₃ , a = 0.005, b = 0.01, c = 0.016, d = 0.11, x
= 0.55, y = 0.003, and a piezoelectric pellet was manufactured in the same manner as in Example 1 so that z had the values shown in Table 3 below, and the characteristics were measured. The results are shown in Table 3.

[0026]

[Table 3]

The electrical characteristics Kp and the strength σ _3b were maximum when the Sb substitution amount was 1 mol%, that is, when z = 0.01. The amount of Sb substitution that improves electrical characteristics and strength at the same time is
0.005 ≦ z ≦ 0.03. Further, even if Nb was substituted for Sb, the electrical characteristics and strength were improved within the same range as Sb.

Example 3 Pb _1-abcd La _a Pr _b Ba _c Sr _d (Zr _x Ti
In the composition formula represented by _1-xyz In _y Sb _z ) O ₃ , a = 0.005, b = 0.01, c = 0.016, d = 0.11, x
= 0.55, z = 0.01, and y was set to the values in Table 4 below, a piezoelectric pellet was manufactured in the same manner as in Example 1, and the characteristics were measured. Table 4 shows the results.

[0029]

[Table 4]

The electrical characteristics Kp and the strength σ _3b were maximum when the In substitution amount was 0.3 mol%, that is, when z = 0.003. The amount of In substitution that improves the electrical properties and strength at the same time is 0.002 ≤ z ≤ 0.005. Also, even if Fe was substituted for In, the electrical characteristics and strength were improved within the same range as In.

Example 4 Pb _{(1 + e) -abcd} La _a P _b Ba _c Sr _d (Zr _x T
In the composition formula represented by i _1-xyz N _y M _z ) O ₃ ,
a = 0.005, b = 0.01, c = 0.016, d = 0.11, x = 0.
Piezoelectric pellets were manufactured in the same manner as in Example 1 such that 55, y = 0.003, z = 0.01, and e had the values shown in Table 5 below, and the characteristics were measured. The results are shown in Table 5.

[0032]

[Table 5]

As is clear from this table, by increasing the amount of PbO by 1 mol% to 5 mol%, that is,
By setting 01 ≦ e ≦ 0.05, the strength of the piezoelectric pellet is improved. Further, even if the firing temperature is set to 1100 to 1200 ° C, the same characteristics as those obtained at the conventional firing temperature of 1200 ° C can be obtained.

[0034]

EFFECTS OF THE INVENTION The piezoelectric ceramic composition of the present invention has a fine crystal structure, is significantly improved in strength, and is also improved in Curie temperature, as compared with the conventional piezoelectric ceramic composition. . Further, by increasing the amount of Pb, the firing temperature can be lowered and the strength can be improved.

Claims (2)

[Claims] 1. A composition represented by the following formula: Pb _1-abcd La _a P _b Ba _c Sr _d (Zr _x Ti
_1-xyz N _y M _z ) O ₃ (wherein P is at least one of Pr, Nd and Sm, N is at least one of In, Fe, Co and Ga, and M is at least one of Sb and Nb, and 0.002 ≤ a ≤ 0.010, 0.1.
005 ≤ b ≤ 0.020, 0.010 ≤ c ≤ 0.025, 0.050 ≤ d ≤
0.150, 0.540 ≤ x ≤ 0.560, 0.002 ≤ y ≤ 0.005, 0.
005 ≦ z ≦ 0.030), and a piezoelectric ceramic composition for an actuator. 2. A composition represented by the following formula: Pb_{(1 + e) -abcd}La_aP_bBa_cSr_d(Zr_xT
i_1-xyzN_yM_z) O ₃ (In the above formula, P is at least Pr, Nd, or Sm.
Is also one or more, and N is In, Fe, Co, or Ga.
At least one kind, and M is Sb, Nb
And at least one kind, and 0.002 ≤ a ≤ 0.010, 0.
005 ≤ b ≤ 0.020, 0.010 ≤ c ≤ 0.025, 0.050 ≤ d ≤
0.150, 0.01 ≤ e ≤ 0.05, 0.540 ≤ x ≤ 0.560, 0.002
≤ y ≤ 0.005, 0.005 ≤ z ≤ 0.030)
A piezoelectric ceramic composition for an actuator, comprising: