JP3259321B2 - 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 for an actuator, and more particularly, to a piezoelectric ceramic composition having a large piezoelectric strain constant, a high Curie temperature, and a low dielectric constant. The present invention relates to a piezoelectric ceramic composition.

[0002]

2. Description of the Related Art An actuator is a device which uses a piezoelectric inverse effect, that is, a function of converting electric energy to mechanical energy, and which generates a micron or micron-under micro displacement by applying a voltage, and which is a buzzer. Precision control of sound or flow rate of pumps, valves, etc., auto tracking and auto focus of VTR heads, accurate positioning of micron-under mechanical cutting tools, and application development to micro positioning devices for semiconductor manufacturing etc. In recent years, it has been progressing rapidly.

Conventionally, as a piezoelectric material for an actuator, a lead zirconate titanate ceramic composition (PZ) has been used.
T) is known to have excellent piezoelectric properties, and various improvements have been made depending on the intended use.

For example, a part of lead zirconate titanate is
A method of substituting with a divalent ion such as Sr ²⁺ or a trivalent ion such as Bi ³⁺ , Pb (Ni _1/2 W _1/2 ) O ₃ ,
Pb (Co _1/3 Nb _2/3 ) O ₃ , Pb (Ni _1/3
The properties of piezoelectric materials for PZT-based actuators have been improved by a method of synthesizing a solid solution with a complex perovskite compound such as Nb _2/3 ) O ₃ .

Incidentally, there are unimorph type, bimorph type and laminated type piezoelectric actuator elements for controlling minute displacement with a precision of micron or micron under. The required characteristics are a high piezoelectric strain constant and a high piezoelectric strain constant. Having the Curie temperature together, that is, for example, the transverse mode piezoelectric strain constant d ₃₁ and the Curie temperature Tc
Is the following value. (1) d ₃₁ > 300 × 10 ⁻¹² m / v, Tc> 150 ° C. (2) d ₃₁ > 250 × 10 ⁻¹² m / v, Tc> 250 ° C.

[0006]

However, in general, a material having a high piezoelectric strain constant such that d ₃₁ exceeds 300 × 10 ⁻¹² m / v has a Curie temperature (Tc) of about 100 ° C. As a result, the upper limit of the operating temperature of the element is limited to 50 to 60 ° C., which limits the practical application of the element. In addition, the dielectric constant ε ₃₃ ^T / ε ₀ exceeds 5000, and when driving at a high frequency, the impedance is reduced, heat is easily generated, and a large-capacity drive power source is required.

On the other hand, a material having a high Curie temperature (Tc) has a problem that the piezoelectric strain constant (d ₃₁ ) is low and a high voltage is required for driving the element.

For these reasons, the above (1) and (2)
The piezoelectric distortion constant of the high transverse mode (d
₃₁ ) and a high Curie temperature (Tc), and a low dielectric constant (eg, ε ₃₃ ^T / ε ₀ <5000).
There is a demand for the development of a material having both of these.

The present invention has been made in view of the above circumstances, and has a high electromechanical coupling coefficient, a high piezoelectric strain constant, a low dielectric constant, and a high Curie temperature, and is extremely useful as an actuator for various piezoelectric materials. An object is to provide a piezoelectric ceramic composition.

[0010]

According to a first aspect of the present invention, there is provided a piezoelectric ceramic composition for an actuator, comprising a ceramic composition represented by the following general formula (I) as a main component and a sub-component as a sub-component.
Sb is converted to Sb ₂ O ₅ with respect to the main component to form a triple.
% Or less . _{Pb (1-xm) La X} A m (Zr y Ti 1-y) 1-x / 4 O 3 ... (I) ( where, in the general formula (I), 0 <x ≦ 0.07,0.40
≦ y ≦ 0.65, 0 <m ≦ 0.15, A = Ba and / or Ca)

[0011] Actuator piezoelectric ceramic composition according to claim (2), in claim (1), Sb and N b as an auxiliary component, relative to the main component, _Sb 2 _{O 5} and N
It is characterized by containing 3 % by weight or less in terms of b ₂ O ₅ .

In addition, Ta is further contained as an auxiliary component.
In the following, Sb,
The Sb ₂ O ₅ , Nb ₂ O ₅ , and Ta ₂ O ₅ conversion values of Nb and Ta are simply referred to as “Sb ₂ O ₅ addition amount” and “Nb
₂ O ₅ amount ", referred to as" _Ta 2 _{O 5} added amount ".

That is, the present inventors have studied in detail the composition of a piezoelectric ceramic composition for an actuator in order to solve the above-mentioned problems, and as a result, the composition represented by the general formula (I) as a main component, Furthermore, Sb below a specific amount , or
Has found that a composition containing Sb and Nb , or further Ta, is a ceramic composition having a combination of a high electromechanical coupling coefficient, a high piezoelectric strain constant, a low dielectric constant and a high Curie temperature, The present invention has been completed.

Hereinafter, the present invention will be described in more detail. The ceramic composition of the present invention has both a high piezoelectric constant, a low dielectric constant, and a high Curie temperature. In particular, in the general formula (I), the perovskite crystal in the range of 0.03 ≦ x ≦ 0.06 In the vicinity of the phase boundary (MPB = morphotropic phase boundary), the transverse mode piezoelectric strain constant (d ₃₁ ) is 300 × 10 ⁻¹² m / v.
, The dielectric constant (ε ₃₃ ^T / ε ₀ ) is as low as less than 5000, and the Curie temperature (Tc) is as high as 150 ° C. or more. , Very suitable.

In particular, in the general formula (I),
of~ The composition having the composition of
₃₁) Is 350 × 10^-12exceeds m / v and
Temperature (Tc) is 200 ° C. or higher, and dielectric
Rate (ε₃₃ ^T/ ε₀) Is less than 5000
It is an excellent material for tutors. x = 0.06, y = 0.58, A = Ba, m = 0.01, Sb₂O₅Addition amount = 0.15% by weight (Examples described later)1)  x = 0.035, y = 0.53, A = Ba, m = 0.10, Sb₂O₅Addition amount = 0.40% by weight (Examples described later)3)  x = 0.05, y = 0.57, A = Ca, m = 0.01, Sb₂O₅Addition amount = 0.60% by weight (Examples described later)4)

Also, the following Is the transverse mode piezoelectric strain
Constant (d₃₁) Is 250 × 10^-12over m / v and
The Curie temperature exceeds 250 ° C
Very high displacement material that can be used in cold environments
Material.  x = 0.02, y = 0.52, A = Ba, m = 0.02, Nb₂O₅Addition amount = 1.0 wt%, Sb₂O₅Addition amount = 1.0% by weight (Examples described later)6)

Here, a material having an La content x of more than 7 mol% is not suitable as a material for a piezoelectric actuator because the Curie temperature (Tc) is lower than 150 ° C. (Comparative Examples 5, 6, and 7 described later). . Ba and / or Ca content m
Exceeds 15 mol%, the Curie temperature (Tc) is lower than 150 ° C., and thus is not suitable as a piezoelectric actuator material (Comparative Examples 8 and 9 described later). Those having a Zr content y of less than 40 mol% and those having a Zr content of more than 65 mol% are larger than the phase boundary of the perovskite crystal and have a Zr / Zr
Since the Ti composition ratio is shifted, the transverse mode piezoelectric strain constant (d
₃₁ ) is reduced and therefore excluded.

Further, Sb ₂ O ₅ for the main component , or
Those in which the added amount of Sb ₂ O ₅ and Nb ₂ O ₅ and / or Ta ₂ O ₅ exceeds 3.0% by weight (Comparative Examples 1, 2 and
The method 3) is not suitable because the pyrochlore phase is mixed in the sintered body and the piezoelectric strain constant is reduced.

The ceramic composition of the present invention is prepared, for example, by weighing oxide raw materials of the respective constituent elements so as to have a predetermined composition, performing wet mixing and calcining with a ball mill or the like, and then pulverizing the obtained powder. It can be obtained by sintering at 1100 ° C to 1300 ° C. In an embodiment described later, S
Although Sb ₂ O ₅ is used as the b source, it goes without saying that Sb ₂ O ₃ may be used.

[0020]

The following examples, reference examples and comparative examples are given below.
The present invention will be described more specifically, but the present invention is not limited by the following examples unless it exceeds the gist.

Examples 1 to6, Comparative Examples 1 to12  PbO, La as a high-purity oxide raw material with a purity of 99.9% or more
₂O₅, TiO₂, ZrO₂, Sb₂O₅, Nb
₂O₅, Ta₂O₅And BaCO₃Or CaCO₃
Is weighed to a predetermined ratio, and then wet for 24 hours using a ball mill.
Formula mixing was performed. After the mixture is dried and molded, 900 ° C
Calcined for 2 hours, then crushed in a mortar,
Again for 24 hours. Rubber obtained powder
After isostatic pressing by a press method,
Baking at 0 ° C. Then, the obtained sintered body is sliced
After processing into a disk shape and a rod shape using a
Screen paste paste and bake electrodes at 550 ℃
went. The polarization process is performed at a silicon oxide temperature of 80 to 110 ° C.
Electric field strength 2.0-3.0 kV / mm, time 5
20 minutes, after one day, vector impedance
1 kHz by the resonance-anti-resonance method using a
The dielectric constant at z (ε₃₃ ^T/ ε₀) Dielectric loss at 1 kHz
Loss (tan δ), electromechanical coupling coefficient in transverse mode
(K₃₁), Transverse mode piezoelectric strain constant (d₃₁) Piezoelectric
Physical properties were measured. Also, the temperature characteristics of the relative permittivity were measured,
The Curie temperature (Tc) was determined from the relative permittivity maximum.
The results are shown in Tables 1 and 2.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

As described above in detail, the piezoelectric ceramic composition for an actuator of the present invention has a high electromechanical coupling coefficient, a high piezoelectric strain constant, a low dielectric constant, and a high Curie temperature. It can be used effectively as In particular, the piezoelectric ceramic composition for an actuator of the present invention has a large piezoelectric strain constant and a high Curie temperature, so that the operating temperature range of the element is wide,
It is extremely useful as a material for piezoelectric actuators,
Its contribution to industrial use is extremely large.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-52-28699 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 41/187 C04B 35/00

Claims (2)

(57) [Claims] During 1. A following general formula _{(I) Pb (1-xm} ) La X A m (Zr y Ti 1-y) 1-x / 4 O 3 ... (I) ( where formula (I), 0 <x ≦ 0.07, 0.40
≦ y ≦ 0.65, 0 <m ≦ 0.15, as a main component a ceramic composition represented by A = Ba and / or Ca), a subcomponent
Sb is converted to Sb ₂ O ₅ with respect to the main component to obtain 3
A piezoelectric ceramic composition for an actuator containing up to 10% by weight . 2. The method of claim 1, Sb as the sub-component
And Nb with respect to the main component, Sb ₂ O ₅ and Nb ₂
In terms of O ₅ actuator containing 3 wt% or less piezoceramic composition.