JP2002220280A - Piezoelectric ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic whose piezoelectricity is improved. SOLUTION: The ceramic contains a rhombohedral perovskite-type compound such as (Na0.5Bi0.5)TiO3, etc., a tetragonal perovskite-type compound such as BaTiO3, (K0.5Bi0.5)TiO3, etc., and an orthorhombic perovskite-type compound such as NaNbO3, KNbO3, CaTiO3, etc. Its piezoelectricity is improved by 3 types of compounds with different crystal structures. These 3 types can be dissolved each other to form a solid solution or undissolved. A compositional ratio of these, where the rhombohedral, tetragonal, and orthorhombic perovskite- type compounds are assumed to be a, b, and c, respectively, is preferably within a range satisfying the following equations: a+b+c=1, 0.40<a<=0.99, 0<b<=0.40, and 0<c<0.20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an actuator,
The present invention relates to a piezoelectric ceramic widely used in a field such as a sensor or a resonator.

[0002]

2. Description of the Related Art Piezoelectric materials generate distortion (conversion of electrical energy to mechanical energy) when an electric field is applied from the outside, and generate electric charges on the surface when mechanical stress is applied from the outside (mechanical). Energy conversion into electric energy), and has been widely used in various fields in recent years. For example, a piezoelectric material such as lead zirconate titanate (Pb (Zr, Ti) O ₃ ; PZT) generates a strain that is approximately proportional to the applied voltage on the order of 1 × 10 ⁻¹⁰ m / V. It is excellent for fine position adjustment and the like, and is also used for fine adjustment of an optical system. Conversely, piezoelectric materials are used as sensors to read small forces and deformations, since the amount of charge generated is proportional to the applied stress or the amount of deformation due to it. . Furthermore, since a piezoelectric material has excellent responsiveness, it is possible to excite the piezoelectric material itself or an elastic body in a bonding relationship with the piezoelectric material to cause resonance by applying an AC electric field. They are also used as transformers, ultrasonic motors and the like.

Most of the piezoelectric materials currently put into practical use are solid-solution systems (PZT-based) composed of PbZrO ₃ (PZ) -PbTiO ₃ (PT). The reason is that the crystallographic phase boundary between rhombohedral PZ and tetragonal PT (M.
P. B. This is because excellent piezoelectric characteristics can be obtained by using a composition in the vicinity. A variety of PZT-based piezoelectric materials that meet various needs by adding various subcomponents or additives have been widely developed. For example, mechanical quality factor (Qm) large piezoelectric constant (d ₃₃₎ is in place is small, from those large displacement is used, such as an actuator for position adjustment sought direct way to use the piezoelectric constant (d ₃₃ ) Has a large mechanical quality factor (Qm) instead of a small value, and there are various types that are suitable for use in alternating current applications, such as ultrasonic generating elements such as ultrasonic motors.

Further, there is one which is put into practical use as a piezoelectric material other than PZT system, it also magnesium niobate (Pb (Mg, Nb) O 3; PMN) and lead-based perovskite such as main Most of them are solid solutions.

However, these lead-based piezoelectric materials are mainly composed of highly volatile lead oxide (PbO) even at low temperatures.
In a large amount of about 60 to 70% by mass. For example,
In PZT or PMN, about 2/3 by mass ratio is lead oxide. Therefore, when manufacturing these piezoelectric materials, an extremely large amount of lead oxide volatilizes and diffuses into the atmosphere at an industrial level in a firing step for porcelain and a heat treatment step for a single crystal product such as a melting step. Would. Although it is possible to recover lead oxide released during the manufacturing stage, it is difficult at present to recover lead oxide contained in piezoelectric products marketed as industrial products, and these are widely used in the environment. If it is released to the public, there is a concern that lead may be eluted by acid rain. Therefore, as the application fields of piezoelectric ceramics and single crystals expand in the future and the amount of use increases, the problem of lead-free becomes a very important issue.

[0006]

SUMMARY OF THE INVENTION A pressure containing no lead
As the electric material, for example, barium titanate (BaTiO
_Three) Or bismuth layered ferroelectrics are known
You. However, barium titanate has a Curie point of 120 ° C.
And above that temperature, the piezoelectricity disappears
Consider applications such as soldering or automotive applications
And impractical. On the other hand, bismuth layered ferroelectrics
Has a Curie point of 400 ° C or more, and has thermal stability
Excellent, but with high crystal anisotropy,
It is necessary to orient spontaneous polarization by zing etc.
There is a problem in the point. Also, if you completely eliminate the lead content,
It is difficult to obtain large piezoelectricity.

Further, recently, as a new material, research on a sodium bismuth titanate-based material has been conducted. For example, Japanese Patent Publication No. Hei 4-60073 and Japanese Patent Application Laid-Open No. H11-180769 disclose materials containing sodium bismuth titanate and barium titanate, and Japanese Patent Application Laid-Open No. H11-171643 discloses a material containing bismuth titanate. A material comprising sodium and potassium bismuth titanate is disclosed. However, this bismuth sodium titanate-based material has not yet obtained sufficient piezoelectric properties as compared with a lead-based piezoelectric material, and there has been a demand for improved piezoelectric properties.

The present invention has been made in view of the above problems, and has as its object to show excellent piezoelectric characteristics, reduce pollution,
An object of the present invention is to provide a piezoelectric ceramic which is excellent from the environmental and ecological point of view.

[0009]

The piezoelectric ceramic according to the present invention comprises a rhombohedral perovskite structure compound, a tetragonal perovskite structure compound, and an orthorhombic perovskite structure compound.

Another piezoelectric ceramic according to the present invention contains a solid solution containing a rhombohedral perovskite structure compound, a tetragonal perovskite structure compound, and an orthorhombic perovskite structure compound.

In these piezoelectric ceramics according to the present invention, the piezoelectric characteristics are improved by three kinds of compounds having different crystal structures. In addition, it is preferable that the content of lead (Pb) is 1% by mass or less from the viewpoints of low pollution, environmental friendliness and ecological aspects.

Further, as shown in the chemical formula 1, the composition ratios a, b and c of these compounds are a + b + c =
1,0.40 <a ≦ 0.99,0 <b ≦ 0.40,0 <
It is preferable that each of the values satisfies c <0.20, and 0.50 <a ≦ 0.99, 0 <b ≦ 0.3
It is more preferable that the value satisfies 0, 0 <c <0.20.

Further, the composition ratio of the compound and the B of the compound
The value obtained by adding the product of the composition of the element located at the A site to the element located at the site with respect to the three kinds of compounds is within a range of 0.9 or more and 1.0 or less as shown in Expression 1. It is preferred that

Still another piezoelectric ceramic according to the present invention comprises a first oxide containing sodium bismuth titanate, at least one second oxide selected from the group consisting of potassium bismuth titanate and barium titanate, and niobium. And at least one tertiary oxide selected from the group consisting of sodium citrate, potassium niobate and calcium titanate.

Still another piezoelectric ceramic according to the present invention comprises a first oxide containing sodium bismuth titanate, at least one second oxide selected from the group consisting of potassium bismuth titanate and barium titanate, and niobium. It contains a solid solution containing at least one tertiary oxide selected from the group consisting of sodium citrate, potassium niobate and calcium titanate.

In these piezoelectric ceramics according to the present invention, the first
The oxide, the second oxide, and the third oxide improve the piezoelectric characteristics.

The composition ratios a, b, and c of these oxides are, as shown in Chemical Formula 2, a + b + c =
1,0.40 <a ≦ 0.99,0 <b ≦ 0.40,0 <
It is preferable that each of the values satisfies c <0.20, and 0.50 <a ≦ 0.99, 0 <b ≦ 0.3
It is more preferable that the value satisfies 0, 0 <c <0.20.

Further, as shown in Expression 2, the composition ratio a of the first oxide and the first oxide
The product of the composition ratio x of the element, the product of the composition ratio b of the second oxide and the composition ratio y of the first element of the second oxide to the second element of the second oxide, and the composition ratio c of the third oxide It is preferable that a value obtained by adding the product of the composition ratio of the third oxide first element to the third oxide second element z be in the range of 0.9 or more and 1.0 or less.

[0019]

Embodiments of the present invention will be described below in detail.

A piezoelectric ceramic according to one embodiment of the present invention comprises:
It contains a rhombohedral perovskite structure compound, a tetragonal (Tetragonal) perovskite structure compound, and an orthorhombic (Orthorhombic) perovskite structure compound. Alternatively, a solid solution containing a rhombohedral perovskite structure compound, a tetragonal perovskite structure compound, and an orthorhombic perovskite structure compound is contained. That is, it contains three types of compounds having different crystal structures, which may or may not be completely dissolved.

Thus, in this piezoelectric ceramic, a crystallographic phase boundary (MPB) is formed at least in part, and the piezoelectric characteristics are improved. Specifically, the electromechanical coupling coefficient is improved and the dielectric constant is improved as compared with the one-component system or the two-component system, and as a result, the displacement is improved.

The rhombohedral perovskite structure compound includes, for example, a first oxide containing sodium bismuth titanate. The first oxide is composed of a first element of the first oxide located at the A site of the perovskite structure, a second element of the first oxide located at the B site of the perovskite structure, and oxygen. It is represented by Chemical Formula 3.

[0023]

## STR1 A1 _x A 2 O ₃ formula, A1 represents a first element first oxide, A2 represents a second element first oxide. x is 1 if it has a stoichiometric composition, but it may deviate from the stoichiometric composition. If it is 1 or less, it is preferable because sinterability can be improved and higher piezoelectric characteristics can be obtained. . The oxygen composition is determined from the stoichiometric composition, and may deviate from the stoichiometric composition.

As the first element of the first oxide, sodium (Na) and bismuth (Bi) correspond to sodium bismuth titanate. The composition ratio between sodium and bismuth in sodium bismuth titanate is 1: 1 in molar ratio if it is a stoichiometric composition, but may deviate from the stoichiometric composition. As the first oxide second element, titanium (Ti) corresponds to sodium bismuth titanate.

The rhombohedral perovskite structure compound has 1
It may be composed of different kinds of compounds, but may be composed of plural kinds of compounds. When it is composed of a plurality of types of compounds, they may or may not form a solid solution.

The tetragonal perovskite structure compound includes, for example, at least one type of second oxide selected from the group including potassium bismuth titanate and barium titanate. The second oxide is composed of a first element of the second oxide located at the A site of the perovskite structure, a second element of the second oxide located at the B site of the perovskite structure, and oxygen. It is represented by Chemical Formula 4.

[0027]

Embedded image B1 _y B2O ₃ formula, B1 represents a first element second oxide, B2 represents a second oxide second element. Although y is 1 if it is a stoichiometric composition, it may deviate from the stoichiometric composition. The oxygen composition is determined from the stoichiometric composition, and may deviate from the stoichiometric composition.

As the first element of the second oxide, potassium (K) and bismuth correspond to potassium bismuth titanate, and barium (Ba) corresponds to barium titanate. The composition ratio of potassium to bismuth in potassium bismuth titanate is 1: 1 in molar ratio as long as it is a stoichiometric composition, but may deviate from the stoichiometric composition.
As the second element of the second oxide, titanium corresponds to both potassium bismuth titanate and barium titanate.

The tetragonal perovskite structure compound may be composed of one kind of compound like the rhombohedral perovskite structure compound, or may be composed of plural kinds of compounds. When it is composed of a plurality of types of compounds, they may or may not form a solid solution.
It should be noted that a larger displacement can be obtained by including potassium bismuth titanate as the tetragonal perovskite structure compound, and a larger displacement can be obtained by including potassium bismuth titanate and barium titanate. It is preferable because an amount can be obtained.

As the orthorhombic perovskite structure compound, for example, at least one of the group containing sodium niobate, potassium niobate and calcium titanate is used.
Species of third oxides. The third oxide is composed of a first element of the third oxide located at the A site of the perovskite structure, a second element of the third oxide located at the B site of the perovskite structure, and oxygen. Formula 5

[0031]

Embedded image C1 _z C2O ₃ formula, C1 represents the first element third oxide, C2 represents the second element third oxide. z is 1 if it has a stoichiometric composition, but may deviate from the stoichiometric composition. The oxygen composition is determined from the stoichiometric composition, and may deviate from the stoichiometric composition.

As the third element of the third oxide, sodium corresponds to sodium niobate, potassium corresponds to potassium niobate, and calcium (Ca) corresponds to calcium titanate. As the third oxide second element, niobium corresponds to sodium niobate and potassium niobate, and titanium corresponds to calcium titanate.

Like the rhombohedral perovskite structure compound, the orthorhombic perovskite structure compound may be constituted by one kind of compound, or may be constituted by plural kinds of compounds. When it is composed of a plurality of types of compounds, they may or may not form a solid solution.

The composition ratio of these rhombohedral perovskite structure compound, tetragonal perovskite structure compound and orthorhombic perovskite structure compound, for example, the composition of the first oxide, the second oxide and the third oxide The ratio is preferably within the range shown in Chemical formula 6 in molar ratio. If the content of the tetragonal perovskite structure compound and the orthorhombic perovskite structure compound is too large, the piezoelectric properties are reduced,
If the amount is too small, sufficient effects due to the inclusion of three types of compounds having different crystal structures cannot be obtained.

[0035]

In the formula, A is a rhombohedral perovskite structure compound (for example, a first oxide), B is a tetragonal perovskite structure compound (for example, a second oxide), and C is an orthorhombic perovskite structure compound. (For example, a third oxide). a, b
And c are a + b + c = 1, 0.40 <a ≦ 0.9
9,0 <b ≦ 0.40 and 0 <c <0.20, respectively.

Here, the composition ratio is a value in the entire piezoelectric ceramic including a solid solution and a non-solid solution. In the chemical formula 6, b is in the range of less than 0.40, further in the range of 0.35 or less, and more preferably in the range of 0.1 to 0.5.
A value within the range of 30 or less is more preferable. Also, c
Is more preferably within a range of 0.15 or less. This is because a larger displacement can be obtained within these ranges.

Depending on the type of the rhombohedral perovskite structure compound, the tetragonal perovskite structure compound and the orthorhombic perovskite structure compound, the optimum range of the composition ratio may be different. For example, when the tetragonal perovskite structure compound is composed of barium titanate, better displacement can be obtained when the values of b and c in Chemical Formula 6 are smaller than in the case where potassium bismuth titanate is included. . In that case, in Chemical Formula 6,
a, b and c are a + b + c = 1, 0.7 <a ≦ 0.
99,0 <b ≦ 0.15, 0 <c <0.15, or a + b + c = 1, 0 <b, 0
It is more preferable that <c, 0 <b + c <0.2.

The composition ratio of the rhombohedral perovskite structure compound, tetragonal perovskite structure compound and orthorhombic perovskite structure compound, and the composition ratio of the element located at the A site to the element located at the B site of these compounds ( (Element located at the A site / element located at the B site) preferably has the relationship shown in Formula 3.

[0039]

0.9 ≦ ax + by + cz ≦ 1.0 where a, b and c are, as shown in Chemical formula 6, a rhombohedral perovskite structure compound, a tetragonal perovskite structure compound and an orthorhombic system Each composition ratio is represented by a molar ratio with the perovskite structure compound. x, y and z
Are, for example, as shown in Chemical Formulas 3, 4 and 5, in order, the elements located at the B site in the rhombohedral perovskite structure compound, the tetragonal perovskite structure compound, and the orthorhombic perovskite structure compound, respectively. 1
Represents the composition ratio by the molar ratio of the element located at the A site, that is, the composition ratio by the molar ratio of the element located at the A site to the element located at the B site.

That is, for example, when the first oxide, the second oxide, and the third oxide are included, the composition ratio a of the first oxide and the first oxide The product of the composition ratio x of one element, the product of the composition ratio b of the second oxide and the composition ratio y of the second oxide first element to the second oxide second element,
And the sum of the product of the composition ratio c of the third oxide and the composition ratio z of the first element of the third oxide to the second element of the third oxide is in the range of 0.9 to 1.0. Preferably, there is. As described in Chemical formula 3, when the ratio is 1.0 or less, high sinterability and excellent piezoelectric characteristics can be obtained, and when the ratio is less than 0.9, the piezoelectric characteristics decrease. is there.

The piezoelectric ceramic may contain lead, but its content is preferably 1% by mass or less, and more preferably it contains no lead. It minimizes the volatilization of lead during firing and the release of lead into the environment after it has been distributed and disposed of as a piezoelectric component in the market, reducing pollution, environmental friendliness and ecological aspects. This is because it is preferable. The average grain size of the crystal grains of the piezoelectric ceramic is, for example, 0.5 μm to 20 μm.

The piezoelectric ceramic having such a configuration can be manufactured, for example, as follows.

First, as a starting material, bismuth oxide (B
i_TwoO_Three), Sodium carbonate (Na _TwoCO_Three) 、 Carbonated
Lium (K_TwoCO_Three), Barium carbonate (BaCO_Three),
Calcium carbonate (CaCO_Three), Titanium oxide (Ti
O_Two) And niobium oxide (Nb)_TwoO_Five)
Prepared as necessary and dried it sufficiently at 100 ° C or more
Then, it is weighed according to the desired composition. In addition, starting materials
May be replaced with oxides such as carbonates or oxalates.
May be used to form an oxide upon firing.
Instead of oxides or other materials that become oxides by firing
May be used.

Next, for example, the weighed starting materials are placed in an organic solvent or water for 5 hours to 20 hours by a ball mill or the like.
After sufficiently mixing the mixture, the mixture is sufficiently dried, press-molded, and calcined at 750 to 900 ° C. for about 1 to 3 hours. Subsequently, for example, the calcined product is pulverized in an organic solvent or water for 10 hours to 30 hours by a ball mill or the like, dried again, and granulated by adding a binder. After granulation, for example, the granulated powder is subjected to 100 MPa to 100 MPa using a uniaxial press molding machine or a hydrostatic molding machine (CIP).
It is press-formed under a load of 400 MPa to form a pellet.

After being formed into pellets, for example, the molded body is heat-treated at 400 ° C. to 800 ° C. for about 2 hours to 4 hours to volatilize the binder, and then main-baked at 950 ° C. to 1300 ° C. for about 2 hours to 4 hours. . The rate of temperature rise and the rate of temperature decrease during the main firing are, for example, about 50 ° C./hour to about 300 ° C./hour. After the main firing, the obtained sintered body is polished as necessary to provide electrodes. After that, 25 ℃ -10
Polarization is performed by applying an electric field of 5 MV / m to 10 MV / m in silicone oil at 0 ° C. for about 5 minutes to 1 hour. Thereby, the piezoelectric ceramic described above is obtained.

As described above, according to this embodiment, the rhombohedral perovskite structure compound such as the first oxide and the second oxide are used.
Since a tetragonal perovskite structure compound such as an oxide and an orthorhombic perovskite structure compound such as a third oxide are contained, or a solid solution containing these is contained, a one-component system or The electromechanical coupling coefficient can be improved as compared with the two-component system,
The dielectric constant can also be improved, and as a result, the amount of displacement can be improved.

Therefore, it is possible to increase the possibility of using a piezoelectric ceramic which does not contain lead or has a low lead content. In other words, it is possible to minimize the volatilization of lead during firing and the release of lead into the environment after being distributed and disposed of as a piezoelectric component on the market, and to reduce pollution, environmental and ecological aspects. Therefore, it is possible to utilize a piezoelectric ceramic which is extremely excellent.

In particular, as shown in Chemical formula 6, the composition ratios a, b and c of the rhombohedral perovskite structure compound, the tetragonal perovskite structure compound and the orthorhombic perovskite structure compound are represented by the molar ratios A + b + c = 1,0.4
0 <a ≦ 0.99, 0 <b ≦ 0.40, 0 <c <0.2
If the values are within the ranges satisfying 0, respectively, the piezoelectric characteristics can be further improved.

Further, if b in Chemical Formula 6 is set to a value within a range of less than 0.40, further within a range of 0.35 or less, further within a range of 0.30 or less, or if c is 0 .1
By setting the value to a value within the range of 5 or less, a larger displacement can be obtained.

Further, as shown in Equation 3, the product of the composition ratio of the compound and the composition ratio of the element located at the A site to the element located at the B site of the compound was added for the three types of compounds. If the value is in the range of 0.9 or more and 1.0 or less, or the composition ratio a of the first oxide and the composition ratio of the first oxide first element to the first oxide second element x, the product of the composition ratio b of the second oxide and the composition ratio y of the first element of the second oxide to the second element of the second oxide,
And the sum of the product of the composition ratio c of the third oxide and the composition ratio z of the first element of the third oxide to the second element of the third oxide is in the range of 0.9 to 1.0. By doing so, the sinterability can be improved and the piezoelectric characteristics can be further improved.

In addition, when the tetragonal perovskite structure compound contains potassium bismuth titanate and further contains potassium bismuth titanate and barium titanate, a larger displacement can be obtained. .

[0052]

EXAMPLES Further, specific examples of the present invention will be described.

(Examples 1-1 to 1-16) First, rhombohedral
Oxide (Na) which is a perovskite-based compound
_0.5Bi_{0. Five}) TiO_Three, Tetragonal perovskite structure
The second oxide BaTiO, which is a compound _Three, And orthorhombic
Third oxide NaNbO, which is a perovskite structure compound
_ThreeStarting materials for bismuth oxide powder, sodium carbonate
Powder, barium carbonate powder, titanium oxide powder and oxidation
Prepare niobium powder and dry it sufficiently above 100 ° C
Later, they were weighed. The mixing ratio of the starting materials is
The composition ratios a, b, and c according to the molar ratios after firing shown in the table are as follows.
In Examples 1-1 to 1-16, as shown in FIG.
Changed.

[0054]

Embedded image

[0055]

[Table 1]

Next, the weighed starting materials were mixed in acetone using a zirconia ball by a ball mill for about 15 hours, dried sufficiently, pressed and formed at 900 ° C.
For about 2 hours. Subsequently, the calcined product was pulverized in acetone for about 15 hours by a ball mill, then dried again, and polyvinyl alcohol (PV) was used as a binder.
A) Granulation was performed by adding an aqueous solution. Thereafter, the granulated powder was temporarily molded by applying a load of 100 MPa using a uniaxial press molding machine, and further subjected to a load of 400 MPa using a CIP to obtain a diameter of 1 mm.
It was formed into a disk-shaped pellet having a thickness of 7 mm and a thickness of 1 mm. After the molding, the molded body was heat-treated at 700 ° C. for about 3 hours to volatilize the binder, and was sintered at 1100 ° C. to 1300 ° C. for 2 hours. The heating rate and the cooling rate during the main firing were both 200 ° C./hour.

After the main firing, the obtained fired body was polished into a parallel plate having a thickness of 0.4 mm, and silver paste was baked on both surfaces thereof at 650 ° C. to form electrodes. After that, 10MV /
The polarization process was performed by applying an electric field of m for 15 minutes. Thus, the piezoelectric ceramics of Examples 1-1 to 1-16 were obtained.

With respect to the obtained piezoelectric ceramics of Examples 1-1 to 1-16, the relative dielectric constant εd, the electromechanical coupling coefficient kr in the spreading direction, and the displacement amount when a voltage pulse of 3 MV / m was applied were measured. did. At that time, the measurement of the relative permittivity εd is L
CR meter (HP4284 manufactured by Hewlett-Packard Company)
A), the measurement of the electromechanical coupling coefficient kr is performed using an impedance analyzer (HP manufactured by Hewlett-Packard Company).
4194A) and a desktop computer with an automatic measuring device by a resonance anti-resonance method. The displacement was measured by controlling the eddy current type non-contact displacement meter, amplifier, oscillator, multimeter and the like with a desktop computer and applying a voltage in silicon oil. Table 1 shows the results.

Further, Comparative Examples 1-1 to 1-1 with respect to the present embodiment.
-6, except that the mixing ratio of the starting materials was changed so that the composition ratios a, b and c according to the molar ratio shown in Chemical Formula 7 become as shown in Table 1. A piezoelectric ceramic was produced under the following conditions. Also in Comparative Examples 1-1 to 1-6, the relative dielectric constant ｄd, the electromechanical coupling coefficient kr, and the amount of displacement when a voltage pulse of 3 MV / m was applied were measured in the same manner as in this example. The results are also shown in Table 1.

In Comparative Example 1-1, only the rhombohedral perovskite structure compound was used. In Comparative Example 1-2, only the rhombohedral perovskite structure compound and the orthorhombic perovskite structure compound were used. Comparative Examples 1-3 to 1 -6 is a case where only a rhombohedral perovskite structure compound and a tetragonal perovskite structure compound are included. Among them, Comparative Example 1-1 is a comparative example with respect to Examples 1-1 to 1-16, and Comparative Example 1-2 is Examples 1-3, 1-8, 1-11, and Examples 1-3.
Comparative Example 1-15, Comparative Example 1-3 is Example 1-1.
Comparative Examples 1 to 5 and Comparative Examples 1-4 are Examples 1-6.
Comparative Examples 1 to 5 and Comparative Examples 1-5 are Examples 1-9.
Comparative Examples 1 to 6 and Comparative Examples 1 to 6
13 to 1-16 correspond to comparative examples.

As shown in Table 1, according to the present embodiment,
A large amount of displacement was obtained compared to the comparative example. That is, the first oxide (Na _0.5 Bi _0.5 ) TiO ₃ , which is a rhombohedral perovskite structure compound, the second oxide BaTiO ₃ , which is a tetragonal perovskite structure compound, and the first oxide (which is a rhombic perovskite structure compound) It has been found that the piezoelectric properties can be improved by including trioxide NaNbO ₃ or by including a solid solution thereof.

Also, from the results of Examples 1-1 to 1-16, when the value of the composition ratio b of the tetragonal perovskite structure compound or the composition ratio c of the orthorhombic perovskite structure compound is increased, the displacement amount increases. After showing the maximum value, there is a tendency to decrease, and b is 0.15 or less and c is 0.1
It was also found that when the value was less than 5, or when b + c was less than 0.20, the piezoelectric characteristics could be further improved.

(Examples 2-1 to 2-26) Example 2-1
In ~ 2 to 26, potassium carbonate powder was prepared as a starting material instead of barium carbonate powder, and as shown in Chemical formula 8,
Second oxide B which is a tetragonal perovskite structure compound
except that instead of the ATiO ₃ to _{(K 0.5 Bi 0.5) TiO 3} , to produce a piezoelectric ceramic in the same conditions as in Example 1-1 to 1-16. The mixing ratio of the starting materials was changed in Examples 2-1 to 2-26 so that the composition ratios a, b, and c based on the molar ratio after firing shown in Chemical formula 8 were as shown in Table 2. Was.

[0064]

Embedded image

[0065]

[Table 2]

Further, Comparative Examples 2-1 to 2 with respect to the present embodiment
-7, except that the mixing ratio of the starting materials was changed so that the composition ratios a, b and c according to the molar ratio shown in Chemical formula 8 become as shown in Table 3. A piezoelectric ceramic was produced under the following conditions. Also for Examples 2-1 to 2-26 and Comparative examples 2-1 to 2-7, the relative dielectric constant ｄd, the electromechanical coupling coefficient kr, and the
The amount of displacement when a voltage pulse of MV / m was applied was measured. The results are shown in Tables 2 and 3.

[0067]

[Table 3]

Comparative Example 2-1 was constructed so as to contain only the rhombohedral perovskite structure compound and the orthorhombic perovskite structure compound, while Comparative Examples 2-2 to 2-7 were constructed so as to contain the rhombohedral perovskite structure compound. This is the case where only the compound and the tetragonal perovskite structure compound are included. Also, in Table 3, the results of Comparative Example 1-1 configured to include only the rhombohedral perovskite structure compound and the results of Comparative Example 1-1 including only the rhombohedral perovskite structure compound and the orthorhombic perovskite structure compound are shown. The results of the configured Comparative Example 1-2 are also shown.

Among them, Comparative Example 1-1 was prepared according to Examples 2-1 to 2-2.
Comparative Example 1-2, Comparative Example 1-2 is Example 2-
Comparative examples for 3, 2-8, 2-13, 2-18, and 2-23, and Comparative example 2-1 are Examples 2-5, 2-10, and 2-1.
Comparative Examples for 5,2-20 and 2-25, Comparative Example 2-2
Are comparative examples for Examples 2-1 to 2-5 and Comparative Example 2-3.
Are comparative examples for Examples 2-6 to 2-10, Comparative Example 2-
4 is a comparative example for Examples 2-11 to 2-15, Comparative Example 2-5 is a comparative example for Examples 2-16 to 2-20, and Comparative Example 2-6 is a comparative example for Examples 2-21 to 2-25. Comparative Examples and Comparative Examples 2-7 correspond to Comparative Examples with respect to Example 2-26.

As shown in Tables 2 and 3, according to the present example, the relative dielectric constant εd was larger than that of the comparative example.
Could be obtained. Examples 2-1 to 2-4, 2
-6 to 2-9, 2-11 to 2-14, 2-16 to 2-1
According to 9, 22-21 to 24, and 2-26, a larger displacement amount could be obtained as compared with the comparative example. In Examples 2-5, 2-10, 2-15, 2-20, and 2-25, good displacement could not be obtained, but a larger value was obtained for the relative permittivity εd. So
If the sinterability is improved by optimizing the sintering temperature or adding a sintering aid, and the electromechanical coupling coefficient kr is improved, a large value may be obtained for the displacement amount.

That is, tetragonal perovskite structuring
As the second oxide which is a compound (K_{0. Five}Bi_0.5) TiO
_ThreeAs in Examples 1-1 to 1-16.
In addition, it was found that the piezoelectric characteristics can be improved.

From the results of Examples 2-1 to 2-26, when the value of the composition ratio b of the tetragonal perovskite structure compound or the composition ratio c of the orthorhombic perovskite structure compound is increased, the displacement amount increases. After showing the maximum value, there is a tendency to decrease, and b is 0.40 or less and c is 0.2
It was also found that when the value is less than 0, the piezoelectric characteristics can be further improved. Further, b is less than 0.40, 0.35 or less, 0.3
It was also found that if the value was set to 0 or less, or if c was set to 0.15 or less, the piezoelectric characteristics could be further improved.

(Embodiments 3-1 to 3-4) Embodiments 3-1 to 3-1
In 3-4, potassium carbonate powder was further prepared as a starting material, and as shown in Chemical formula 9, BaTiO ₃ and (K) were used as the second oxide, which is a tetragonal perovskite structure compound.
_A piezoelectric ceramic was produced under the same conditions as in Examples 1-1 to 1-16, except that _0.5 Pie _0.5 ) TiO ₃ was included. The compounding ratios of the starting materials were determined in Examples 3-1 to 3-4 so that the composition ratios a, b1, b2, and c according to the molar ratio after firing shown in Chemical formula 9 were as shown in Table 4. Changed.

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[0075]

[Table 4]

In Examples 3-1 to 3-4, the relative permittivity εd, the electromechanical coupling coefficient kr, and the displacement amount when a voltage pulse of 3 MV / m were applied were determined in the same manner as in Example 1-1. It was measured. The results are shown in Examples 1-7, 2-7,
Table 4 shows the results of 2-17, 2-22, and 2-26.

As shown in Table 4, Example 3-1 is more effective than Examples 1-7 and 2-7, and Example 3-2 is more effective than Example 2
-17, Example 3-3 is more than Example 2-22,
In Example 3-4, a larger displacement could be obtained than in Example 2-26. That is, BaTiO is used as the second oxide which is a tetragonal perovskite structure compound.
₃ and (K _0.5 Bi _0.5 ) TiO ₃ , it was found that the piezoelectric characteristics could be further improved. Also,
The amount of displacement increases as the content of potassium bismuth titanate increases, shows a maximum value, and then tends to decrease. The composition ratio of the tetragonal perovskite structure compound b1 +
b2 is 0.40 or less, further 0.35 or less, furthermore, 0.
It was also found that when the ratio was 30 or less, the piezoelectric characteristics could be further improved.

(Examples 4-1 to 4-3) Examples 4-1 to 4-1
In 4-3, the composition ratio x of the first oxide first element to the first oxide second element shown in Chemical formula 10, the composition ratio y of the second oxide first element to the second oxide second element, and And under the same conditions as in Example 1-7, except that the starting materials were blended such that the composition ratio z of the third oxide first element to the third oxide second element was as shown in Table 5. A piezoelectric ceramic was manufactured. A, b and c are a = 0.9, b
= 0.05, c = 0.05, x, y and z were the same, and x = y = z. That is, ax + by + cz shown in Expression 3 has the same value as x, y, and z.

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[0080]

[Table 5]

In Examples 4-1 to 4-3, the relative dielectric constant εd, the electromechanical coupling coefficient kr, and the displacement amount when a voltage pulse of 3 MV / m were applied were determined in the same manner as in Example 1-7. It was measured. The results are shown in Table 5 together with the results of Example 1-7.

As shown in Table 5, Examples 4-1 to 4-
According to No. 3, a larger displacement amount could be obtained as compared with Example 1-7. That is, as shown in Expression 3, the product of the composition ratio a of the first oxide and the composition ratio x of the first element of the first oxide to the second element of the first oxide, and the composition ratio b of the second oxide And the product of the composition ratio y of the second oxide first element with respect to the second oxide second element, and the composition ratio c of the third oxide and the third oxide first element with respect to the third oxide second element When the value obtained by adding the products of the composition ratios z is in the range of 0.9 or more and 1.0 or less, the sinterability can be improved, and
It has been found that the piezoelectric characteristics can be improved.

Although some examples have been specifically described in the above embodiment, other rhombohedral perovskite structure compounds, other tetragonal perovskite structure compounds, or other orthorhombic perovskite structure compounds can be used. Even when a compound is included, the same result as in the above example can be obtained.

As described above, the present invention has been described with reference to the embodiments and examples. However, the present invention is not limited to the above embodiments and examples, and can be variously modified. For example, in the above embodiments and examples, the first oxide is described as the rhombohedral perovskite structure compound, the second oxide is described as the tetragonal perovskite structure compound, and the orthorhombic system is described. Although the third oxide has been described as a perovskite structure compound, other compounds may be included as long as they have these crystal structures.

In the above embodiment and examples,
Although the first oxide, the second oxide, and the third oxide have been specifically described with reference to examples, the first oxide, the second oxide, and the third oxide may include other oxides.

Further, in the above embodiment, the first oxide,
The crystal structures of the second oxide and the third oxide have been described. However, if an oxide having the above-described composition is contained or a solid solution containing these is contained, it is not necessary to discuss these crystal structures. Rather, it is included in the present invention.

In addition, in the above embodiments and examples, only the case where the rhombohedral perovskite structure compound, the tetragonal perovskite structure compound and the orthorhombic perovskite structure compound are included has been described. And other compounds having other crystal structures.

The present invention further relates to a compound having an impurity or another crystal structure, other than the elements constituting the rhombohedral perovskite structure compound, tetragonal perovskite structure compound and orthorhombic perovskite structure compound. May be included as a constituent element. Such elements include, for example, strontium (Sr), magnesium (Mg), lithium (Li), zirconium (Z
r), hafnium (Hf), tantalum (Ta) and rare earth elements.

[0089]

As described above, according to the piezoelectric ceramic according to any one of claims 1 to 12, a rhombohedral perovskite structure compound, a tetragonal perovskite structure compound, and an orthorhombic perovskite are obtained. Because it contains a structural compound or contains a solid solution containing them, or contains a first oxide, a second oxide, and a third oxide, or contains a solid solution containing these As a result, the electromechanical coupling coefficient can be improved as compared with the one-component system or the two-component system, and the dielectric constant can be improved. As a result, the displacement can be improved. Therefore, it is possible to increase the possibility of using piezoelectric ceramics that do not contain lead or have a low lead content. In other words, it is possible to minimize the volatilization of lead during firing and the release of lead into the environment after being distributed and disposed of as a piezoelectric component on the market, and to reduce pollution, environmental and ecological aspects. Therefore, it is possible to utilize a piezoelectric ceramic which is extremely excellent.

In particular, according to the piezoelectric ceramic according to any one of claims 4 to 6 or 10 to 12, as shown in Chemical formula 1 or Chemical formula 2, their composition ratios a, b and c are a + b + c = 1, 0.40 <a ≦
Since the values are within the ranges respectively satisfying 0.99, 0 <b ≦ 0.40 and 0 <c <0.20, higher piezoelectric characteristics can be obtained.

According to the piezoelectric ceramic according to claim 6 or claim 12, as shown in the formula 1, the composition ratio of the compound and the element located at the A site relative to the element located at the B site of the compound. The sum of the products with the composition ratios of the three compounds is in the range of 0.9 or more and 1.0 or less, or as shown in Expression 2,
The product of the composition ratio a of the oxide and the composition ratio x of the first element of the first oxide to the second element of the first oxide, and the composition ratio b of the second oxide
And the product of the composition ratio y of the second oxide first element with respect to the second oxide second element, and the composition ratio c of the third oxide and the third oxide first element with respect to the third oxide second element Since the value obtained by adding the product of the composition ratio z is in the range of 0.9 or more and 1.0 or less, sinterability can be improved and piezoelectric characteristics can be further improved.

[Procedure amendment]

[Submission date] August 21, 2001 (2001.8.2
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0054

[Correction method] Change

[Correction contents]

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[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0058

[Correction method] Change

[Correction contents]

With respect to the obtained piezoelectric ceramics of Examples 1-1 to 1-16, the relative dielectric constant εd, the electromechanical coupling coefficient kr in the spreading direction, and the displacement amount when a voltage pulse of 3 MV / m was applied were measured. did. At that time, the measurement of the relative permittivity εd is L
CR meter (HP428 manufactured by Hewlett -Packard Company)
4A), and the measurement of the electromechanical coupling coefficient kr was performed by a resonance anti-resonance method using an automatic analyzer using an impedance analyzer (HP4194A manufactured by Hewlett -Packard Company) and a desktop computer. The displacement is measured by controlling a non-contact eddy current displacement meter, amplifier, oscillator, multimeter, etc. with a desktop computer.
The test was performed by applying a voltage in silicone oil. Table 1 shows the results.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0061

[Correction method] Change

[Correction contents]

As shown in Table 1, according to the present embodiment,
A large amount of displacement was obtained compared to the comparative example. That is, the first oxide (Na _0.5 Bi _0.5 ) TiO ₃ , which is a rhombohedral perovskite structure compound, the second oxide BaTiO ₃ , which is a tetragonal perovskite structure compound, and the first oxide (which is a rhombic perovskite structure compound) 3 to include the oxides NaNbO _3, or if to contain solid solutions thereof, could be improved a pressure conductive properties.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0071

[Correction method] Change

[Correction contents]

That is, (K _0.5 Bi _0.5 ) TiO 2 is used as the second oxide which is a tetragonal perovskite structure compound.
Also it includes a ₃ in the same manner as in Example 1-1 to 1-16 was found to be improved pressure conductive properties.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshiko Gokita 1-13-1 Nihonbashi, Chuo-ku, Tokyo FDT term in TDK Corporation (reference) 4G031 AA01 AA06 AA11 AA14 AA35 BA10 CA01

Claims (12)

[Claims] 1. A piezoelectric ceramic comprising a rhombohedral perovskite structure compound, a tetragonal perovskite structure compound, and an orthorhombic perovskite structure compound. 2. A piezoelectric ceramic comprising a solid solution containing a rhombohedral perovskite structure compound, a tetragonal perovskite structure compound, and an orthorhombic perovskite structure compound. 3. The piezoelectric ceramic according to claim 1, wherein the content of lead (Pb) is 1% by mass or less. 4. The composition ratio of the rhombohedral perovskite structure compound, the tetragonal perovskite structure compound, and the orthorhombic perovskite structure compound is within the range shown in Chemical Formula 1 in terms of molar ratio. 2. The method according to claim 1, wherein
A piezoelectric ceramic according to claim 3. Embedded image aA + bB + cC (where A represents a rhombohedral perovskite structure compound, B represents a tetragonal perovskite structure compound, and C represents an orthorhombic perovskite structure compound. A, b and c, respectively.
Are a + b + c = 1, 0.40 <a ≦ 0.99, 0 <b
≦ 0.40, 0 <c <0.20. ) 5. In the above formula 1, a, b and c are:
a + b + c = 1, 0.50 <a ≦ 0.99, 0 <b ≦
5. The piezoelectric ceramic according to claim 4, wherein the values are in a range satisfying 0.30, 0 <c <0.20, respectively. 6. The composition ratio of the rhombohedral perovskite structure compound, the tetragonal perovskite structure compound and the orthorhombic perovskite structure compound, and the compound is located at the A site relative to the element located at the B site. The piezoelectric ceramic according to any one of claims 1 to 5, wherein the composition ratio of the element has a relationship shown in Expression 1. 0.9 ≦ ax + by + cz ≦ 1.0 (where a, b and c are molar ratios of the rhombohedral perovskite structure compound, the tetragonal perovskite structure compound and the orthorhombic perovskite structure compound) A represents a rhombohedral perovskite structure compound, b represents a tetragonal perovskite structure compound, and c represents an orthorhombic perovskite structure compound.
y and z are the composition ratios of the rhombohedral perovskite structure compound, the tetragonal perovskite structure compound, and the orthorhombic perovskite structure compound, respectively, in terms of the molar ratio of the element located at the A site to the element located at the B site. Represent. ) 7. A first composition comprising sodium bismuth titanate.
An oxide; at least one second oxide of the group comprising potassium bismuth titanate and barium titanate; and at least one second oxide of the group comprising sodium niobate, potassium niobate and calcium titanate. A piezoelectric ceramic comprising: three oxides. 8. A first composition comprising sodium bismuth titanate.
An oxide; at least one second oxide of the group comprising potassium bismuth titanate and barium titanate; and at least one second oxide of the group comprising sodium niobate, potassium niobate and calcium titanate. A piezoelectric ceramic comprising a solid solution containing three oxides. 9. The piezoelectric ceramic according to claim 7, wherein the second oxide contains potassium bismuth titanate or barium titanate. 10. The composition ratio of the first oxide, the second oxide, and the third oxide in a molar ratio within a range shown in Chemical formula 2. The piezoelectric ceramic according to claim 9. AA + bB + cC (where A represents the first oxide, B represents the second oxide, and C represents the third oxide. A, b and c represent a + b + c =
1,0.40 <a ≦ 0.99,0 <b ≦ 0.40,0 <
This is a value within a range that satisfies c <0.20. ) 11. The method according to claim 2, wherein a, b and c
Are a + b + c = 1, 0.50 <a ≦ 0.99, 0 <b
The piezoelectric ceramic according to claim 10, wherein the values are within a range satisfying ≤ 0.30 and 0 <c <0.20, respectively. 12. The method according to claim 1, wherein the first oxide is sodium (N
a) a first oxide first element containing at least one member of the group containing a) and bismuth (Bi), a first oxide second element containing titanium (Ti), and oxygen (O); The second oxide includes a second oxide first element including at least one of a group including potassium (K), bismuth, and barium (Ba); a second oxide second element including titanium; Oxygen, and the third oxide is a third oxide first element containing at least one of a group containing sodium, potassium and calcium (Ca), and at least one of a group containing niobium and titanium. A third oxide second element containing at least one element and oxygen; a composition ratio of the first oxide, the second oxide, and the third oxide; Composition ratio of first element of oxide, second element of second oxide The composition ratio of the first element of the second oxide to the first element and the composition ratio of the first element of the third oxide to the second element of the third oxide have the relationship shown in Expression 2. The piezoelectric ceramic according to claim 11. 0.9 ≦ ax + by + cz ≦ 1.0 (where a, b, and c are composition ratios by a molar ratio of the first oxide, the second oxide, and the third oxide, and a is 1 represents an oxide, b represents a second oxide, c represents a third oxide, x represents a composition ratio of the first oxide / first element to a molar ratio of the first oxide / second element to y, and y represents the second oxide. 2 oxide second
The composition ratio based on the molar ratio of the first element of the second oxide to the element, and z represents the composition ratio based on the molar ratio of the first element of the third oxide to the second element of the third oxide. )