JPH0672717A - Piezoelectric electrostrictive material - Google Patents

Abstract

PURPOSE:To increase the distortion amt. by substituting a part of the atoms in the B site of an oxide having a composition shown by a specified formula and having a perovskite crystal structure for other atoms. CONSTITUTION:The oxides of Pb, Ba, Zr, Sn and Ti are mixed in a specified ratio and calcined to obtain the calcined body having a composition shown by formula I (0.01<=a<=0.03, 0.2<=b<=0.6, 0.01<=x and 0.04<=(2/3)x+y<=0.075) or formula III (0.01<=c<=0.05, and Q is B, Mg, V, Cr, Mn, Fe, Co, Ni, Cu, Ge, Mo, etc.). The metallic Q to be substituted is added by 1-5 atomic % based on the total of Zr, Sn and Ti, mixed and sintered to obtain a piezoelectric electrostrictive material in which the ratio of the lattice constants c/a is controlled to 0.993 and having a large distortion amt. Besides, Pb(M1/2, R1/2)O3 (M is Mg, Mn and Co, and R is Te and W) is added to the oxide of formula I in the ratio of (1-K)/K to obtain a piezoelectric electrostrictive material of the formula II (0.01<=K<=0.05).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric electrostrictive material suitable for an actuator used for positioning in precision machine tools, flow control valves, braking devices for automobiles, etc.
In particular, the present invention relates to a piezoelectric electrostrictive material which gives a sufficiently large amount of strain even in a temperature region higher than room temperature and has a small amount of phase transition electric field shift at high temperatures.

[0002]

2. Description of the Related Art A substance having a property of causing mechanical strain when an electric field is applied is generally called a piezoelectric material or a piezoelectric electrostrictive material, and a bimorph or a piezoelectric material is used as an electromechanical conversion element. Widely used in ignition devices, ultrasonic transducers, piezoelectric buzzers, ceramic filters, etc.

Generally, when an electric field is applied to a piezoelectric material, its crystal structure changes, and it exhibits a maximum strain amount (electromechanical coupling constant) at its crystal transformation point. Since the crystal transformation point varies depending on each piezoelectric material, an appropriate piezoelectric material is selected and used according to the target operating temperature.

As such a piezoelectric material, BaTiO ₃ ,
Pb (Zr, Ti) O ₃ (generally called PZT), LiNbO
₃ , LiTaO _{3 and the} like are known.

By the way, PZT widely used as a piezoelectric material has a strain amount (ΔL / L) of about 1.5 × 10 ⁻³ , but a larger strain amount, for example, a strain amount of about 3.0 × 10 ⁻³ or more. If it is attempted to be obtained, there is a problem in that the strain generated when an electric field is applied becomes anisotropic and stress concentrates on the grain boundaries in the PZT, leading to fracture.

On the other hand, in PZT, part of Zr is replaced with Nb and Sn.
In substituted PNZST material (e.g. Pb _{0. 99} Nb _0.02 [(Zr _0.6
Sn _0.4 ) _0.94 Ti _0.06 ] _0.98 O ₃ ) has been reported to produce large strains without causing damage ("Applied Physics", Vol. 54, No. 6 (1985), pages 591-595). . This is because the PNZST material has an electric field strength of 30 as shown schematically in FIG.
When an electric field of about KV / cm is applied, first the antiferroelectric phase
This is because the phase transition from (a) to the ferroelectric phase (b) causes a large isotropic expansion, and a piezoelectric phenomenon occurs after the phase transition, which causes extension (distortion) in the electric field application direction. The strain in the direction of electric field application, which is obtained by both the expansion due to this phase transition ((a) → (b)) and the strain due to voltage application, is about twice as large as the strain of ordinary PZT piezoelectric electrostrictive materials. is there. In this respect, the PNZST material having the above-mentioned composition is very promising as a piezoelectric electrostrictive material for actuators. However, since it has a large electric field hysteresis, it has not been put to practical use as an actuator material.

As a piezoelectric electrostrictive material which eliminates the above drawbacks and gives a large amount of strain and has a small hysteresis / strain, Japanese Patent Laid-Open No. 3-174787 discloses Pb _1-x-0.5a Ba _x Nb _a {(Zr
_1-b Sn _b ) _1-y Ti _y } _1-a O ₃ (however, 0.01a ≦ 0.0
3, 0.2 ≦ b ≦ 0.6, 0.01 ≦ x, and 0.04 ≦ (2/3) x +
A piezoelectric electrostrictive material having a composition represented by y ≦ 0.075) is disclosed.

However, according to the research by the present inventor,
The above-mentioned piezoelectric electrostrictive material can give a large amount of strain at room temperature, but is in a temperature range higher than room temperature (room temperature to 15
The amount of strain in the region of 0 ° C.) is small. Further, when the temperature rises, the phase transition electric field shifts to the high electric field side.

Therefore, an object of the present invention is to provide a piezoelectric electrostrictive material which exhibits the same characteristics as those at room temperature even in a temperature range higher than room temperature.

[0010]

[Means for Solving the Problems] In order to achieve the above object, Pb
As a result of earnest research on the piezoelectric electrostrictive material composed of a -Ba-Nb-Zr-Sn-Ti-based oxide, the present inventor has found that the larger the lattice strain of the oxide forming the piezoelectric electrostrictive material is, c
It was discovered that the smaller the / a), the smaller the reduction in strain amount at high temperature. Therefore, Pb _1-x-0.5a Ba _x Nb _a {(Zr _1-b Sn
_b ) _1-y Ti _y } _{1-a In the} perovskite type oxide having a composition represented by O ₃ , if a part of a specific metal element in the oxide is replaced with another metal element, the lattice constant of Ratio c /
It has been discovered that a can be set to a specific value or less, so that a strain amount equivalent to that at room temperature can be given even at a high temperature of about 150 ° C, and the shift amount of the phase transition electric field can be reduced. did. The present invention is based on the above findings.

That is, the first piezoelectric electrostrictive material of the present invention is
The following general formula: Pb _1-x-0.5a Ba _x Nb _a {(Zr _1-b Sn _b ) _1-y Ti _y } _1-a O
₃ (However, 0.01 ≦ a ≦ 0.03, 0.2 ≦ b ≦ 0.6, 0.01 ≦
x, and 0.04 ≦ (2/3) x + y ≦ 0.075), in a perovskite type oxide having a composition in which some of the B site atoms in the crystal are replaced with other metal atoms, The ratio c / a of the constants is 0.993 or less.

The second piezoelectric electrostrictive material of the present invention has the following general formula: Pb _1-x-0.5a Ba _x Nb _a [{(Zr _1-b Sn _b ) _1-y T
i _y } _1-a ] _1-K (M _1/2 R _1/2 ) _K O ₃ (where M is Mg, Mn or Co, R is Te, or W
And 0.01 ≦ a ≦ 0.03, 0.2 ≦ b ≦ 0.6, 0.01 ≦ x,
0.04 ≦ (2/3) x + y ≦ 0.075, and 0.01 ≦ k ≦ 0.05).

The present invention is described in detail below. The first piezoelectric electrostrictive material of the present invention has the general formula: Pb _1-x-0.5a Ba _x Nb _a {(Zr _1-b Sn _b ) _1-y Ti _y } _1-a O ₃ ... ( 1) (In the formula (1), 0.01 ≦ a ≦ 0.03, 0.2 ≦ b ≦ 0.6,
0.01≤x and 0.04≤ (2/3) x + y≤0.075) A part of the metal atom in the oxide having the composition represented by the formula is replaced with another metal atom. The oxide represented by the formula (1) has a perovskite type crystal structure, but some of the atoms occupying a specific site in the perovskite type crystal structure are replaced with other metal atoms. The metal atom to be substituted, the metal atom to be substituted, and the amount thereof will be described in detail later.

As described above, the first piezoelectric electrostrictive material of the present invention has the composition of the above formula (1) as a basic composition, and a part of the metal atoms in this basic composition is replaced with another metal atom. It was obtained by doing.

The second piezoelectric electrostrictive material of the present invention has the general formula: Pb _1-x-0.5a Ba _x Nb _a [{(Zr _1-b Sn _b ) _1-y Ti _y } _1-a ] _1-K (M _1/2 R _1/2 ) _K O ₃ (2) (In the formula (2), M is Mg, Mn, or Co, and R is T
e or W, 0.01 ≦ a ≦ 0.03, 0.2 ≦ b ≦ 0.6,
0.01 ≦ x, 0.04 ≦ (2/3) x + y ≦ 0.075, and 0.01 ≦ k
≤0.05).

The above formula (2) is represented by [Pb _1-x-0.5a Ba _x Nb _a {(Zr _1-b Sn _b ) _1-y Ti _y } _1-a O ₃ ] _1-K [Pb (M It can be rewritten as _1/2 R _1/2 ) O ₃ ] _K ... (2) ′. As can be seen from equation (1) and (2) ', the second piezoelectric electrostrictive material of the present invention is directed to speak basic composition of the formula (1), to the basic composition, Pb (M _1/2 R
_{It can be said that 1/2} ) O ₃ (M is Mg, Mn, or Co and R is Te or W) is added in a specific amount.

As described above, in the present invention, (a) a specific metal atom in an oxide having a basic composition is replaced with another metal atom, or (b) a specific oxide is added to the basic composition. As a result, the high temperature characteristics of the piezoelectric electrostrictive material made of an oxide having a basic composition (composition represented by the formula (1)) are improved.

Before describing the first and second piezoelectric electrostrictive materials of the present invention, the basic composition will be described first. Basic composition Pb _1-x-0.5a Ba _x Nb _a {(Zr _1-b Sn _b ) _1-y Ti _y } _1-a O
The content a of ₃ Nb is in the range of 0.01 to 0.03. When Nb is less than 0.01, the phase transition does not occur unless a high electric field is applied to the piezoelectric electrostrictive material. If the amount exceeds 0.03, the phase transition from the ferroelectric phase to the antiferroelectric phase does not occur even if the electric field is removed, which is a defect. Preferred Nb content a is 0.015 to 0.02
It is 5.

Next, the Sn content b is in the range of 0.2 to 0.6. Accordingly, the Zr content (1-b) is 0.4 to 0.8.
It becomes the range of. When Sn is less than 0.2 (Zr exceeds 0.8), the phase transition from the ferroelectric phase to the antiferroelectric phase does not occur even if the electric field is removed, which is a defect. In addition, the amount of Sn exceeding 0.6 (Zr
Is less than 0.4), no phase transition occurs unless a high electric field is applied. The preferable Sn content b is 0.25 to 0.45, and the preferable Zr content (1-b) is 0.55 to 0.75.

When a part of Pb is replaced by Ba, the amount of strain increases and the hysteresis decreases (the value of hysteresis / strain decreases). This is considered to be due to the following three reasons. That is, (a) substitution of part of Pb with Ba expands the lattice constant of the crystal, and the strain amount increases accordingly. Especially when the lattice constant of the a-axis is 4.120 angstroms or more, the strain amount is 3 ×
10 ^-3 or more. (b) By introducing Ba, BaZrO ₃ having a non-ferroelectric composition is partially formed. At this time, Ba randomly enters the piezoelectric electrostrictive material, so that BaZrO ₃ is locally nonuniformly formed in the piezoelectric electrostrictive material. (c) The formation of BaZrO _{3 having} a non-ferroelectric composition locally hinders the phase transition between the antiferroelectric phase and the ferroelectric phase.

Since the formation sites of BaZrO ₃ are randomly arranged in this manner, the strength of the electric field causing the phase transition is not constant. That is, the strength of the electric field that causes the phase transition varies depending on the proportion of the BaZrO ₃ formed, and the phase transition occurs even in a weak electric field in a portion where BaZrO ₃ is small, but a relatively large electric field must be applied in a portion where BaZrO ₃ is large. No phase transition occurs. Therefore, the phase transition is diffused in the piezoelectric electrostrictive material as a whole, and the phase transition occurs continuously within a certain electric field strength. As a result, the amount of strain of the piezoelectric electrostrictive material tends to change gently with respect to the strength of the electric field, and becomes smaller than the hysteresis of the conventional PNZST material (the hysteresis curve becomes slim).

By replacing a part of Pb with Ba, the hysteresis / strain of the piezoelectric electrostrictive material is reduced. In order to obtain this effect, it is necessary to introduce 0.01 or more of Ba into the piezoelectric electrostrictive material instead of Pb. However, the addition of Ba has the effect of destabilizing the antiferroelectric phase, so if Ba is added in an amount exceeding a certain amount, the phase transition from the ferroelectric phase to the antiferroelectric phase does not occur even if the electric field is removed. . Since the amount of Ba correlates with the amount y of Ti as described later, its upper limit is also determined by the relationship with y.

In a piezoelectric electrostrictive material having a basic composition,
Hysteresis decreases as Ti is reduced. However, as the amount of Ti decreases, the ferroelectric phase becomes unstable, and the phase transition from the antiferroelectric phase to the ferroelectric phase may stop unless a high electric field is applied. It becomes necessary to increase the amount x of x. On the other hand, the antiferroelectric phase becomes unstable as the amount of Ti increases,
Even if the electric field is removed, it will not return to the antiferroelectric phase, so it is necessary to decrease the amount x of Ba. Thus, Ti
The quantity y is correlated with the Ba quantity x.

The relationship between the amount of Ba x and the amount of Ti y is expressed by the following equation. 0.04 ≦ (2/3) x + y ≦ 0.075

FIG. 2 shows the amount of Ba x and the amount of Ti y in the basic composition.
It is a graph which shows the range which can be taken. Ba composition x
And Ti amount y are straight lines l ₁ , l ₂ , l _{3 of} this graph, respectively.
And within the area surrounded by the x-axis (but not including the x-axis). The reasons for limiting this area will be described below. Straight line l ₁ (x = 0.01): In order to reduce hysteresis / distortion, the Ba amount x needs to be 0.01 or more. Above the x-axis (y> 0): The basic composition contains Ti. Linear l _2: This is y = - (2/3) is a straight line showing the x + 0.075. In the region above this, the antiferroelectric phase becomes unstable due to excessive amounts of Ba and Ti, and even if the electric field is removed, the antiferroelectric phase does not return to the antiferroelectric phase. Therefore, the area should be a straight line l ₂ or less. Linear l _3: This is y = - (2/3) is a straight line showing the x + 0.04. In the region below this, the ferroelectric phase becomes unstable due to an excessive amount of Ba and Ti, and no phase transition occurs unless a high electric field is applied. Therefore, the area should be a straight line l ₃ or more.

For the above reason, the amounts of Ba and Ti in the basic composition are in the region shown in FIG. 2, that is, x = 0.01, (2/3) x
+ Y = 0.04, (2/3) x + y = 0.075 and in the region bounded by the x-axis (but not including the x-axis). The preferred range is 0.03 ≦ x ≦ 0.05, y> 0, 0.045 ≦ (2/3) x + y
≦ 0.07.

First Piezoelectric Electrostrictive Material The oxide having the above-mentioned basic composition (composition represented by the formula (1)) has a perovskite type crystal structure, but the first piezoelectric electrostrictive material of the present invention is B in this perovskite type crystal structure
A part of the metal atom of the site is replaced with another metal atom.

In the oxide of the perovskite type crystal structure having the composition represented by the formula (1), the metal elements entering the B site are Zr, Sn and Ti, but some of the metal atoms entering the B site are Substitution with other metal atoms shown below. Therefore, the first piezoelectric electrostrictive material has the following formula: Pb _1-x-0.5a Ba _x [Nb _a {(Zr _1-b Sn _b ) _1-y Ti _y } _1-ac Q _c ] O ₃ It can be expressed by (3). Metals substituting Zr, Sn, and Ti (formula
As Q) in (3), B, Mg, V, Cr, Mn, Fe,
Co, Ni, Cu, Ge, Mo, Sb, Te, Hf, Ta, W and the like can be mentioned.

The amount of metal Q substituting for Zr, Sn and Ti is Zr,
It is preferably 1 to 5 atomic% of the total number of Sn and Ti. That is, in the formula (3), 0.01 ≦ c ≦ 0.05. By substituting the B-site atoms so as to fall within the above range, the value of the lattice constant ratio c / a can be 0.993 or less, and a good strain amount can be obtained even at high temperature. In addition,
If the lattice constant ratio c / a exceeds 0.993, the amount of strain at high temperatures becomes small.

The first piezoelectric electrostrictive material can be obtained by weighing and mixing each metal oxide so as to satisfy the above-mentioned formula (3), and sintering the obtained mixture. In addition, each metal oxide is weighed in advance so as to have a basic composition to produce a temporary sintered body, and a metal or an oxide thereof which replaces an element in the basic composition is added to the temporary sintered body. It can also be manufactured by (crushing) and mixing and re-sintering.

The second piezoelectric electrostrictive material second piezoelectric electrostrictive material, the oxide represented by the basic composition described above, further _{Pb (M 1/2 R 1/2} ) O 3 ( where, M Is M
g, Mn, or Co, and R is Te or W) and is represented by the formula (2) or formula (2) ′ shown above.

In the second piezoelectric electrostrictive material, the basic composition and
The ratio with Pb (M _1/2 R _1/2 ) O ₃ is (1-k): k, but since 0.01 ≦ k ≦ 0.05, the oxide represented by the basic composition and Pb (M ₁ Mixing ratio with _{/ 3} N _2/3 ) O ₃ is 0.99: 0.01
It becomes ~ 0.95: 0.05. The value of k is less than 0.01 (Pb (M _1/2 R
_(1/2 ) O ₃ is small), the effect of adding Pb (M _1/2 R _1/2 ) O ₃ does not appear, and the decrease in strain amount in the high temperature region cannot be suppressed. On the other hand, when the value of k exceeds 0.05 (a large amount of Pb (M _1/2 R _1/2 ) O ₃ is mixed), the phase transition due to the application of an electric field does not occur ((a) in FIG. 1).
(Because the change from (b) to (b) does not occur), only the piezoelectric strain is obtained, and the obtained strain amount becomes small. The preferred value of k is 0.01
~ 0.03.

When the value of k is limited to the above range, the ratio c of lattice constants in the oxide forming the second piezoelectric electrostrictive material is c.
/ A becomes 0.993 or less.

The second piezoelectric electrostrictive material can be obtained by weighing and mixing each metal oxide so as to satisfy the above-mentioned formula (2), and sintering the obtained mixture. In addition, each metal oxide is weighed in advance so as to have a basic composition to produce a temporary sintered body, and Pb (M
It is also possible to manufacture by adding (milling) and mixing the oxide represented by _1/2 R _1/2 ) O ₃ and sintering again.

[0035]

According to the research conducted by the present inventors, the piezoelectric electrostrictive material made of the oxide represented by the formula (1) gives good strain characteristics at room temperature and exhibits small (hysteresis / strain). , The amount of strain becomes smaller at a temperature higher than room temperature,
Further, the phase transition electric field shifts to the high electric field side.

Therefore, in the piezoelectric electrostrictive material having the basic composition represented by the formula (1), (a) Zr, Sn, and Ti in the basic composition
Of the complex oxide (piezoelectric strain material) obtained by substituting a part of the compound with another metal element, or (b) adding a specific amount of a specific oxide to the oxide having this basic composition. The ratio c / a of the lattice constants in) is set to a specific value (0.993) or less.

When the lattice constant ratio c / a is small, the lattice strain in the crystal of the oxide forming the piezoelectric electrostrictive material is large. The larger the lattice strain, the stronger the covalent bond,
Crystallization isotropic (c / a approaches 1) due to temperature rise is suppressed, and as a result, reduction in strain amount at high temperatures can be prevented.

Further, at this time, the shift of the phase transition electric field at high temperature becomes small because the antiferroelectric phase is stabilized at high temperature and the phase boundary with the ferroelectric phase becomes vertical to the temperature.

[0039]

The present invention will be described in more detail by the following examples. PbO as an essential component of Examples 1-5 and Comparative Examples 1-6 The starting _{material, BaCO 3, Nb 2 O 5} , Zr
O ₂ , SnO ₂ and TiO _2, and MnO as a raw material of choice,
CoO, TeO ₂ , MgO, NiO, WO ₃ , Ta ₂ O ₅ , Al ₂ O
_{Using 3} , Ga ₂ O ₃ or CdO, each oxide was weighed so as to have the composition shown below, and mixed in a ball mill for 24 hours.

Example 1: Pb _0.96 Ba _0.03 [Nb _0.02 {(Zr _0.7 Sn _0.3 ) _0.98 Ti _0.02 }
_{0.98] 0.99 (Mn 1/2 Te 1/2} ) 0.01 O 3 Example 2: Pb _0.96 Ba _{0.03 [Nb 0.02 {(Zr 0.7 Sn 0.3} ) 0.97 Ti 0.03}
_{0.98] 0.98 (Co 1/2 Te 1/2} ) 0.02 O 3 Example 3: Pb _0.97 Ba _{0.03 [Nb 0.02 {(Zr 0.7 Sn 0.3} ) 0.97 Ti 0.03}
_0.97 Mg _0.01 ] O ₃ Example 4: Pb _0.96 Ba _0.03 [Nb _0.02 {(Zr _0.7 Sn _0.3 ) _0.97 Ti _0.03 }
_{0.98] 0.99 (Co 1/2 Te 1/2} ) 0.01 O 3 Example 5: Pb _0.965 Ba _{0.03 [Nb 0.02 {(Zr 0.7 Sn 0.3} ) 0.97 T
i _0.03 } _0.97 Cd _0.01 O ₃ Comparative Example 1: Pb _0.97 Ba _0.03 [Nb _0.02 {(Zr _0.7 Sn _0.3 ) _0.97 Ti _0.03 }
_0.98 ] O ₃ Comparative Example 2: Pb _0.97 Ba _0.03 [Nb _0.02 {(Zr _0.7 Sn _0.3 ) _0.98 Ti _0.02 }
_{0.98] 0.98 (Ni 1/2 W 1/2} ) 0.02 O 3 Comparative Example 3: Pb _0.97 Ba _{0.03 [Nb 0.02 {(Zr 0.7 Sn 0.3} ) 0.976 Ti
_0.024 } _0.98 ] _0.98 Mg _0.01 (Ni _1/2 W _1/2 ) _0.01 O ₃ Comparative Example 4: Pb _0.96 Ba _0.03 [Nb _0.02 {(Zr _0.7 Sn _0.3 ) _0.984 Ti
_0.016 } _0.98 ] _0.97 (Co _1/3 Ta _2/3 ) _0.03 O ₃ Comparative Example 5: Pb _0.965 Ba _0.03 [Nb _0.02 {(Zr _0.7 Sn _0.3 ) _0.97 T
i _0.03 } _0.97 Al _0.01 O ₃ Comparative Example 6: Pb _0.965 Ba _0.03 [Nb _0.02 {(Zr _0.7 Sn _0.3 ) _0.97 T
i _0.03 } _0.97 Ga _0.01 ] O ₃

The obtained mixture was molded with a pressure of 1000 kg / cm ² and sintered at 1300 ° C. for 2 hours to obtain a sintered body (piezoelectric electrostrictive material) having a thickness of 0.3 mm.

Electrode plates made of gold were formed on both sides of the above sintered body (piezoelectric electrostrictive material). Apply a voltage between the electrodes and
The amount of strain at 30 ° C. was measured. The results are shown in FIG.
In the figure, the horizontal axis is c of the sintered body (piezoelectric electrostrictive material)
The value of / a is taken.

Further, with respect to the piezoelectric electrostrictive materials (sintered bodies) of Examples 1 and 2 and Comparative Example 1, the strain amount was measured by changing the temperature from room temperature to 150 ° C. The result is shown in FIG. The values of c / a in the oxides of each example are shown in Table 1 below.

[0044]

[0045]Example 6 By the same method as in Example 1, the composition has the following formula: [Pb_0.97Ba_0.03Nb_0.02{(Zr_0.7Sn_0.3)_0.97Ti_0.03}_0.98O₃]_1-K(Pb (Co _1/2 Te_1/2) O₃]_K・ ・ ・ Represented by (4), multiple piezoelectric electrostrictive materials with k value less than 0.10.
Made

The strain amount at 130 ° C. of this piezoelectric electrostrictive material was measured in the same manner as in Example 1. The results are shown in Figure 5.
Shown in.

FIG. 5 also shows the amount of strain at 130 ° C. of the piezoelectric electrostrictive material of Comparative Example 1 (corresponding to k = 0 in the above formula (4)).

As can be seen from FIG. 5, the value of k is 0.01 to 0.
In the range of 05, the piezoelectric electrostrictive material shows a large strain amount.

Examples 7-9 and Comparative Example 7 The following composition formula: [Pb _0.97 Ba _0.03 Nb _0.02 {(Zr _0.7 Sn _0.3 ) _0.97 T
i _0.03 } _0.98 O ₃ ] _0.99 [Pb (Mn _1/2 Te _1/2 ) O ₃ ]
_0.01 (Example 7), [Pb _0.97 Ba _0.03 Nb _0.02 {(Zr _0.7 Sn _0.3 ) _0.97 T
i _0.03 } _0.98 O ₃ ] _0.98 [Pb (Co _1/2 Te _1/2 ) O ₃ ]
_0.02 (Example 8), [Pb _0.97 Ba _0.03 Nb _0.02 {(Zr _0.7 Sn _0.3 ) _0.97 T
i _0.03 } _0.98 O ₃ ] _0.95 [Pb (Co _1/2 W _1/2 ) O ₃ ]
_0.05 (Example 9), and [Pb _0.97 Ba _0.03 Nb _0.02 {(Zr _0.7 Sn _0.3 ) _0.97 T
i _0.03 } _0.98 O ₃ ] _0.98 [Pb (Fe _1/2 Ta _1/2 ) O ₃ ]
Four types of piezoelectric electrostrictive materials represented by _0.02 (Comparative Example 7) were manufactured in the same manner as in Example 1.

With respect to the above four types of piezoelectric electrostrictive materials, the amount of strain at 130 ° C. was measured by the same method as in Example 1.
The measurement results (strain amount at 130 ° C.) are shown in Table 2 together with the value of c / a in each piezoelectric electrostrictive material. For reference, each value of Comparative Example 1 is also shown in Table 2.

[0051]

With respect to the piezoelectric electrostrictive materials of Examples 7 to 9 and the piezoelectric electrostrictive material of Comparative Example 1, the phase transition electric field (E _RT ) at room temperature (25 ° C.) and the phase transition electric field (E _RT ) at 130 ° C. ₁₃₀ ) was measured to determine E _RT / E ₁₃₀ . Results are shown in FIG.

As can be seen from FIG. 6, the E _RT / E ₁₃₀ value of the piezoelectric electrostrictive material according to the present invention is closer to 1 than the E _RT / E ₁₃₀ value of the piezoelectric electrostrictive material of Comparative Example 1. That is, Comparative Example 1
The amount of shift of the phase transition electric field at a high temperature (130 ° C.) is smaller than that of the piezoelectric electrostrictive material of (1).

[0054]

As described above in detail, the piezoelectric electrostrictive material of the present invention gives a large strain amount in a temperature range from room temperature to about 150 ° C. Further, the shift amount of the phase transition electric field at that time is not large.

The piezoelectric electrostrictive material according to the present invention is suitable as a material for various actuators requiring a large amount of displacement, and can be favorably used even in a high temperature environment.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the occurrence of two-stage strain when an electric field is applied to a PNZST material.

FIG. 2 Ba amount (x) in the basic composition of the piezoelectric electrostrictive material
3 is a graph showing a region in which the Ti amount (y) can be taken.

FIG. 3 is a graph showing the relationship between the lattice constant c / a of the piezoelectric electrostrictive materials of Examples 1 to 5 and Comparative Examples 1 to 6 and the strain amount at 130 ° C.

FIG. 4 is a graph showing strain amounts of the piezoelectric electrostrictive materials of Examples 1 and 2 and Comparative Example 1 in a temperature range from room temperature to 150 ° C.

FIG. 5 is a graph showing the degree of change in strain amount when the amount of oxide added to the basic composition (value of k in formula (4)) is changed in Example 6, and Comparative Example 1 The strain amount at 130 ° C. of the piezoelectric electrostrictive material is also shown together.

6 is a ratio (E _RT / E ₁₃₀ ) of a phase transition electric field (E _RT ) at room temperature of the piezoelectric electrostrictive materials of Examples 7 to 9 and Comparative Example 1 to a phase transition electric field (E ₁₃₀ ) at 130 ° C. It is a graph which shows.

Claims (2)

[Claims] 1. The following general formula: Pb _1-x-0.5a Ba _x Nb _a {(Zr _1-b Sn _b ) _1-y Ti _y } _1-a O
₃ (However, 0.01 ≦ a ≦ 0.03, 0.2 ≦ b ≦ 0.6, 0.01 ≦
x, and 0.04 ≤ (2/3) x + y ≤ 0.075), wherein a part of the B site atoms of the oxide having a perovskite type crystal structure is replaced by another metal atom, A piezoelectric electrostrictive material having a constant ratio c / a of 0.993 or less. 2. The following general formula: Pb _1-x-0.5a Ba _x Nb _a [{(Zr _1-b Sn _b ) _1-y T
i _y } _1-a ] _1-K (M _1/2 R _1/2 ) _K O ₃ (where M is Mg, Mn or Co, R is Te, or W
And 0.01 ≦ a ≦ 0.03, 0.2 ≦ b ≦ 0.6, 0.01 ≦ x,
A piezoelectric electrostrictive material having a composition represented by 0.04 ≦ (2/3) x + y ≦ 0.075 and 0.01 ≦ k ≦ 0.05.