JP3189582B2 - Piezoelectric ceramic composition for actuator - 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, and more particularly, to a piezoelectric ceramic composition which can be advantageously used in a piezoelectric element such as an actuator.

[0002]

2. Description of the Related Art Research on piezoelectric ceramic compositions has been conducted for a long time, and products using such piezoelectric ceramic compositions are widely used in various fields. Products using such piezoelectric ceramic compositions include, for example, 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,
2. Description of the Related Art Piezoelectric actuators utilize displacement and force generated through a piezoelectric phenomenon as a mechanical drive source, and are one of the things that have recently attracted attention in the field of mechatronics. Since this piezoelectric actuator is a solid-state element utilizing the piezoelectric effect, it consumes less power, has a faster response speed, and has a larger displacement compared to a conventional electromagnetic actuator having a configuration in which a coil is wound around a magnetic material. It has excellent features such as low heat generation, small size and weight.

[0003] Various types of piezoelectric ceramic compositions are known as those which can be used for the piezoelectric element as described above. For example, many piezoelectric ceramic compositions have been known, starting from the technique of adding a simple oxide to PZT-based ceramics described in Japanese Patent No. 275421 issued in 1960. U.S. Pat. No. 2,911,370 discloses that PZT-based ceramics are added with elements such as niobium (Nb), tantalum (Ta), and rare earth metals, or a part of Pb is converted into strontium (S).
It teaches to increase the piezoelectric constant and dielectric constant of the resulting composition by substituting it with an element of an alkaline earth metal such as r) or calcium (Ca). JP-A-62-298192 teaches a piezoelectric ceramic composition having a basic composition of Pb (Zr _x Ti _y ) O ₃ as a piezoelectric ceramic composition used for an actuator element, and this composition is used as a material for an actuator. It reports that it has a usable piezoelectric strain constant and extremely low dielectric loss.

Further, Japanese Patent Application Laid-Open No. 4-260662 discloses a 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), and teaches a piezoelectric ceramic composition having a high piezoelectric property and a particularly high Curie temperature, which is suitable for an actuator.

[0005] This composition has a three-point bending strength of 75 MPa. When the composition is subjected to a repeated driving test at 100 ° C. and a voltage of 0 to 800 V, cracks occur. this is,
This is because the strength is insufficient and domain switching is likely to occur in a repeated driving test.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks of the conventional piezoelectric material and to provide a piezoelectric ceramic composition for an actuator having high piezoelectric characteristics, particularly high Curie temperature, and high strength. Is what you do.

[0007]

Means for Solving the Problems] The piezoelectric ceramic composition of the present invention, the 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) in O ₃ (the above equation, P is Pr, N
d, at least one of Sm, and N is In,
Fe is at least one or more and M is S
at least one of b and Nb, 0.002 ≦ a ≦ 0.010, 0.005 ≦ b ≦ 0.020, 0.010 ≦ c
≦ 0.025, 0.050 ≦ d ≦ 0.150, 0.540 ≦ x ≦ 0.560,
0.002 ≦ y ≦ 0.005 and 0.005 ≦ z ≦ 0.030).

Furthermore, the piezoelectric ceramic composition of the present invention, the composition represented by the following _{formula: Pb (1 + e) -abcd} La a P b Ba c Sr d (Zr x T
i _1-xyz N _y M _z ) O ₃ (where P is at least one of Pr, Nd and Sm, and N is at least one of In and Fe)
And M is at least one of Sb and Nb, 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, 0.54
0 ≦ x ≦ 0.560, 0.002 ≦ y ≦ 0.005, 0.005 ≦ z ≦ 0.
030).

[0009]

The piezoelectric ceramic composition of the present invention comprises a conventional piezoelectric ceramic set.
The product, ie the formula, Pb_1-abBa _aSr_b(Zr_1-xyTi_xzIn
_zSb_y) O_ThreeIn the composition represented by, a part of the Pb component
Is at least one of La, Pr, Nd, and Sm
And at the same time. With this substitution,
The crystal structure of the composition to be refined and the strength greatly 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, excess 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 the Means for Solving the Problems The piezoelectric ceramic composition of the present invention can be used particularly for a piezoelectric actuator of an automobile and also for other piezoelectric elements. For example, a piezoelectric actuator may be formed by using a known method, for example, by bonding two thin plates of a piezoelectric material to form a bimorph structure, or by stacking tens to hundreds of thin plates of a piezoelectric material, and using one of them. It can be manufactured by alternately laminating 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 an 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 the lower limit, there is no effect of miniaturization, and if it exceeds the upper limit, the effect of miniaturization is saturated and the electrical properties of the composition are deteriorated.

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 properties will decrease, 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 out of this range, the electrical characteristics will be degraded. 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%, and In, Fe
The amount of N is at least one or more of 0.002 ≦ y ≦
0.005, ie 0.2-0.5 mol%, and S
The amount of M which is at least one of b and Nb is 0.00
5 ≦ z ≦ 0.030, that is, 0.5 to 3 mol%. By being within these ranges, the crystal structure of the composition becomes finer, the strength is greatly improved, and the Curie temperature is improved.

[0015]

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

[0016] Example _{1 Pb 1-abcd La a Pr} b Ba c Sr d (Zr x Ti
In _{1-xyz In y Sb z)} O 3 represented by formula, 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 , Zr such that b becomes the value 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 further, z = 0.002, 0.
In ₂ O ₃ was weighed to give 003 and 0.005 moles and these were wet mixed in a ball mill for 40 hours.
Next, 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) was added as a binder, and a diameter of 20 mm and a thickness of 1 mm were applied at a molding pressure of 1000 kg / cm ^2.
Into a disk. This was sintered at 1200 ° C. for 2 hours to produce piezoelectric element pellets having different Pr substitution amounts.

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

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
(3 point bending strength with a span of 10 mm) was measured. Table 1 shows the results.

[0020]

[Table 1]

As is clear from this table, when the substitution amount of Pr is 1.0 mol%, that is, when b = 0.01, the strength (σ _3b ) is obtained.
And Curie temperature (Tc) were both maximum. The Pr substitution amount at which the strength and the Curie temperature are simultaneously improved is 0.005.
≦ b ≦ 0.02. For comparison, a piezoelectric pellet was produced by substituting only Pr with the amount of La added being 0, that is, a = 0, and the strength and Curie temperature were measured. Table 2 shows the results.

[0022]

[Table 2]

In this sample, although the strength was slightly improved, the Curie temperature was lowered. Further, as a result of replacing the amount of Pr with 0, that is, b = 0, and replacing only with La,
The effect of improving the strength and Curie temperature of the obtained sample was hardly obtained. Furthermore, even if it replaced with Nd or Sm instead of Pr, the improvement of intensity | strength and Curie temperature was obtained in the same range as Pr.

The compositions of the present invention shown in Table 1 (Pr substitution amount,
b = 0.5-2.0) The piezoelectric pellets manufactured according to the following conditions were repeatedly subjected to a driving test. Repetitive driving 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, the Pr substitution amount, b = 0, 0.3, 2.3, and
With the composition of 2.5 and the conventional material, 40% of samples cracked under the same test conditions.

[0025] Example _{2 Pb 1-abcd La a Pr} b Ba c Sr d (Zr x Ti
_1-xyz In _y Sb _z) in the represented formula in _{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 became the value shown in Table 3 below, and its characteristics were measured. Table 3 shows the results.

[0026]

[Table 3]

The electric characteristics Kp and the strength σ _3b were maximum when the substitution amount of Sb was 1 mol%, that is, when z = 0.01. The amount of Sb replacement at which the electrical properties and strength are simultaneously improved is
0.005 ≦ z ≦ 0.03. In addition, even when substitution was made with Nb instead of Sb, the electrical characteristics and strength were improved within the same range as Sb.

[0028] Example _{3 Pb 1-abcd La a Pr} b Ba c Sr d (Zr x Ti
_1-xyz In _y Sb _z) in the represented formula in _{O 3, a = 0.005, b} = 0.01, c = 0.016, d = 0.11, x
= 0.55, z = 0.01, and a piezoelectric pellet was manufactured in the same manner as in Example 1 so that y became the value shown in Table 4 below, and its characteristics were measured. Table 4 shows the results.

[0029]

[Table 4]

The electric characteristics Kp and the strength σ _3b were maximum when the substitution amount of In was 0.3 mol%, that is, when z = 0.003. The In substitution amount at which the electrical properties and strength are simultaneously improved is 0.002 ≦ z ≦ 0.005. In addition, even when substituted by Fe instead of In, the electrical characteristics and strength were improved within the same range as In.

[0031] Example _{4 Pb (1 + e) -abcd} La a P b Ba c Sr d (Zr x T
i _1-xyz N _y M _z ) In the composition formula represented by O ₃ ,
a = 0.005, b = 0.01, c = 0.016, d = 0.11, x = 0.
55, y = 0.003, z = 0.01, and a piezoelectric pellet was manufactured in the same manner as in Example 1 so that e became a value shown in Table 5 below, and its characteristics were measured. Table 5 shows the results.

[0032]

[Table 5]

As is apparent from this table, the amount of PbO is increased by 1 mol% to 5 mol%, that is, by increasing the amount of PbO by 0.1 mol%.
By setting 01 ≦ e ≦ 0.05, the strength of the piezoelectric pellet is improved. Further, even when the firing temperature is set to 1100 to 1200 ° C, the same characteristics as those conventionally obtained at the firing temperature of 1200 ° C are obtained.

[0034]

The piezoelectric porcelain composition of the present invention has a fine crystal structure, is significantly improved in strength, and has a higher Curie temperature than conventional piezoelectric porcelain compositions. . Further, by increasing the amount of Pb, the firing temperature can be lowered and the strength can be improved.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/42-35/49 CA (STN) REGISTRY (STN)

Claims (2)

(57) [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) in O ₃ (the above equation, P is Pr, N
d, at least one of Sm, and N is In,
Fe is at least one or more and M is S
at least one of b and Nb, 0.002 ≦ a ≦ 0.010, 0.005 ≦ 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). 2. A composition represented by the following _{formula: Pb (1 + e) -abcd} La a P b Ba c Sr d (Zr x T
i _1-xyz N _y M _z ) O ₃ (where P is at least one of Pr, Nd and Sm, and N is at least one of In and Fe)
And M is at least one of Sb and Nb, 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, 0.54
0 ≦ x ≦ 0.560, 0.002 ≦ y ≦ 0.005, 0.005 ≦ z ≦ 0.
030). A piezoelectric ceramic composition for an actuator, comprising: