JP2001181034A - Piezoelectric ceramic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric ceramics composition excellent in piezoelectric characteristics, capable of remarkably improving mechanical strength and further enabling low-temperature sintering. SOLUTION: This piezoelectric ceramic composition is obtained by adding a prescribed amount of at least one kind of metal or metal oxide selected from Pd, Nb2O5, Fe2O3, Sb2O3, V2O5, WO3, PbSiO3, Ta2O5, Cr2O3 and SiO2 as an additive to an oxide composition consisting essentially of a lead-containing perovskite type oxide and represented by the basic compositional formula: Pb(1-a)[(Mg1/3Nb2/3)xTiyZrz]O3 or (Pb(1-a-α)Mα)[(Mg1/3Nb2/3)xTiyZrz]O3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric ceramic set.
Regarding the composition, in particular, the basic composition formula Pb_(1-a)[(Mg_1/3N
b_2/3)_xTi_yZr_z] O_Three Or (Pb_{(1-a- α )}M_α)
[(Mg_1/3Nb _2/3)_xTi_yZr_z] O_ThreeOxidation represented by
Ceramics in which a specific metal or oxide is added to the composition
Mic composition.

[0002]

2. Description of the Related Art Piezoelectric materials made of ferroelectric ceramics are used in various applications such as piezoelectric filters, piezoelectric transformers, ultrasonic vibrators, piezoelectric sounding bodies, piezoelectric actuators, and piezoelectric buzzers. Conventionally, the most frequently used piezoelectric materials include lead, titanium, and zirconium, and a lead zirconate titanate-based composition having a crystal structure called perovskite type, PbZrO ₃ —PbTi
O ₃ , which is a sintered body (ceramic) of fine particles usually called PZT.
Pb (Mg _1/3 Nb _2/3 ) O is added to PZT so that the piezoelectric characteristics can be changed greatly according to the composition compared to plain.
Numerous piezoelectric ceramic compositions to which a composite perovskite such as ₃ (hereinafter referred to as PMN) is added as a third component have been developed and used in many fields.

[0003] Since the properties or the degree required for such piezoelectric ceramic compositions vary greatly depending on the technical field in which they are used and the specific applications, there have been many improvements in the art. I have. For example, Japanese Patent Publication No. Sho 44-17103 discloses PZT with PM
N-added composition, that is, Pb (Mg _1/3 Nb _2/3 )
In O ₃ -PbZrO ₃ -PbTiO ₃ system ternary composition, a part of Pb Sr, Ba or ferroelectric ceramic composition was replaced by Ca is disclosed. This porcelain composition aims to increase the electromechanical coupling coefficient and the dielectric constant by replacing a part of Pb with Sr, Ba or Ca. In addition, Japanese Patent Publication 4-785
No. 82 discloses a ferroelectric porcelain composition described in JP-B-44-17103, in which the composition ratio of Pb is smaller than the stoichiometric amount by a certain amount. The porcelain composition described in Japanese Patent Publication No. 4-78582 is not sufficient in view of the fact that the porcelain composition described in Japanese Patent Publication No. 44-17103 is still insufficient in terms of the electromechanical coupling coefficient and the dielectric constant. It is a proposed one. These prior art porcelain compositions are called PZT-PMN type piezoelectric bodies and are piezoelectric porcelain compositions having a perovskite type crystal structure as a main constituent phase, and have a high dielectric constant or relative permittivity and high electromechanical coupling. It is characterized by having a coefficient,
Both places emphasis on improving the piezoelectric properties.

However, in recent years, for example, the development of piezoelectric actuators for controlling minute displacements on the order of submicrons, which are used in hard disk drive heads for personal computers, has attracted attention. Ultra-thin layers are required, and accordingly, practically enough piezoelectric materials are required to have sufficient mechanical strength. The above-mentioned conventional PZT-PMN type piezoelectric material has excellent piezoelectric properties, but has a problem that the mechanical strength is not always sufficient. Therefore, the PZT-PMN type piezoelectric material is required to be miniaturized and thinned. When it is used, it has a defect that defects such as cracks and chips are generated when it is processed into an element, and cracks are generated due to an external stress due to its property close to its structural material. Further, when driving the element, when a large voltage is applied to obtain a large amount of displacement, there is also a disadvantage that the displacement itself may lead to destruction due to insufficient mechanical strength. Furthermore, the piezoelectric element must not degrade with time in terms of mechanical strength. If the piezoelectric material does not meet these requirements, the reliability of the product will be significantly impaired.

[0005]

When a piezoelectric material is used as an actuator for controlling displacement, it is necessary to increase a piezoelectric constant d indicating an elongation with respect to a unit applied voltage. In general, there is a relation d∝k√ε between the piezoelectric constant d and the electromechanical coupling coefficient k and the relative permittivity ε. To increase the piezoelectric constant d, the electromechanical coupling coefficient k and the specific The dielectric constant ε must be increased. On the other hand, piezoelectric actuator elements and the like that control minute displacement are often processed as small-shaped elements having a very thin thickness, and therefore have a large mechanical strength against stress in the thickness direction, that is, a large resistance. Fold strength is required. Therefore, while maintaining good piezoelectric characteristics without impairing the excellent piezoelectric characteristics of the conventional PZT-PMN type piezoelectric material,
In addition, there is a strong demand for the development of a piezoelectric ceramic composition having a mechanical strength sufficient to meet the requirements for miniaturization and thinning of the element. The porcelain composition described in JP-B-44-17103 has a high sintering temperature and requires a sintering temperature of 1250 ° C. or higher, and the porcelain composition described in JP-B-4-78582 also has a sintering temperature of 1200-1200. Since the firing temperature is as high as 1300 ° C., which is very disadvantageous for industrial production, it is desired to realize a piezoelectric ceramic composition that can be fired at a low temperature.

[0006] In view of the above, it is a main object of the present invention to provide a piezoelectric ceramic composition that solves the above problems. More specifically, the electromechanical coupling coefficient and the relative dielectric constant are large, and therefore, the piezoelectric constant is large, the piezoelectric characteristics are excellent, and the mechanical strength, especially the bending strength, is improved, and the ultra-miniaturization and ultra-thin layer are realized. It is an object of the present invention to provide a piezoelectric ceramic composition that meets the requirements of (1). Furthermore, it is an object of the present invention to provide a piezoelectric ceramic composition which enables firing at a low temperature and is very advantageous for industrial production.

[0007]

Means for Solving the Problems The present inventors have studied the composition of a conventional PZT-PMN type piezoelectric ceramic composition in order to solve the above-mentioned problems, and as a result, determined that a specific additive was added in a specific amount. By adding, without lowering excellent piezoelectric properties, mechanical strength is sufficiently improved,
In addition, they have found that low-temperature sintering can be performed, and have completed the present invention.

More specifically, in order to achieve the above object,
The present invention is based on a perovskite oxide containing lead as a main component.
And the basic composition formula: Pb_(1-a)[(Mg_1/3Nb_2/3)_xTi_yZr_z] O_Three (Where a, x, y, and z are the following conditions: 0 ≦ a ≦ 0.05, 0.01 ≦ x ≦ 0.40, 0.30 ≦ y ≦ 0.50, 0.20 ≦ z ≦ 0.55, an atomic ratio satisfying x + y + z = 1)
Pd, Nb as additives to the composition_TwoO_Five, F
e_TwoO_Three, Sb_TwoO_Three, V_TwoO_Five, WO_Three, PbSiO_Three, Ta
_TwoO_FiveAnd Cr_TwoO_ThreeAt least one type of gold selected from
Metal or oxide in an amount of 0.05 to 1.0% by weight, or Si
O _TwoFrom 0.005 to 0.1% by weight, or SiO_TwoAnd few
At least one kind of the above metals or oxides in a total of 0.05
5 to 1.1% by weight of a piezoelectric ceramic.
Composition. Further, the present invention relates to a perov containing lead.
The main composition formula of which is a skiite type oxide: (Pb_{(1-a- α )}M_α) [(Mg_1/3Nb_2/3)_xTi_yZr
_z] O_Three Where M is selected from Sr, Ca, Ba and La
Α represents 0 <α ≦ 0.1.
And a, x, y, z are the following conditions: 0 ≦ a ≦ 0.05, 0.01 ≦ x ≦ 0.40, 0.30 ≦ y ≦ 0.50, 0.20 ≦ z ≦ 0.55, an atomic ratio satisfying x + y + z = 1)
Pd, Nb as additives to the composition_TwoO_Five, F
e_TwoO_Three, Sb_TwoO_Three, V_TwoO_Five, WO_Three, PbSiO_Three, Ta
_TwoO_FiveAnd Cr_TwoO_ThreeAt least one type of gold selected from
Metal or oxide in an amount of 0.05 to 1.0% by weight, or Si
O _TwoFrom 0.005 to 0.1% by weight, or SiO_TwoAnd few
At least one kind of the above metals or oxides in a total of 0.05
5 to 1.1% by weight of a piezoelectric ceramic.
Composition.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The piezoceramic composition of the present invention is obtained by adding Pd, Nb ₂ O ₅ ,
Fe ₂ O ₃ , Sb ₂ O ₃ , V ₂ O ₅ , WO ₃ , PbSiO ₃ , T
It is characterized in that an additive selected from a ₂ O ₅ , Cr ₂ O ₃ and SiO ₂ is added in a specific amount described later.

First, the basic composition formula of the present invention will be described. The composition ratio (A / B) of the elements present at the so-called A site and B site of the perovskite structure greatly affects the dielectric constant and mechanical strength of the piezoelectric ceramic composition, and furthermore, the sinterability. In the present invention, the amount of the A-site component may be less than the stoichiometric amount in addition to the stoichiometric amount. When the amount of the A-site component is smaller than the stoichiometric amount, it is preferable in that the mechanical strength of the piezoelectric ceramic composition, in particular, the bending strength can be improved. In the present invention, the atomic ratio a for the A-site component is a
Is within the range of 0 ≦ a ≦ 0.05, whereby high strength can be imparted to the piezoelectric ceramic composition. When the atomic ratio a is less than 0, the degree of improvement in the dielectric constant is reduced. In addition, the crystal grain size after sintering becomes 2 μm or more, and the strength is reduced accordingly, so that the object of the present invention cannot be achieved. If the atomic ratio a exceeds 0.05, the sinterability of the piezoelectric ceramic composition is reduced, and a high sintering temperature is required, which is not suitable for practical use. In order to improve the dielectric constant, strength and sinterability in a well-balanced manner, it is more preferable that the atomic ratio a is in the range of 0.01 ≦ a ≦ 0.03.

The present invention relates to the case where the so-called A site of the perovskite structure is Pb alone in the basic composition;
In some cases, part of Pb may be replaced with another element. In the latter case, the element (M) for partially substituting Pb includes Sr, Ca, Ba and La, and at least one element selected from these elements is used. When a part of Pb is replaced with these elements (M), the effect of improving the dielectric constant of the piezoelectric ceramic composition can be obtained. The dielectric constant increases as the substitution amount of M increases, but if the substitution amount is too large, the effect of increasing the dielectric constant decreases, and furthermore, the sinterability of the piezoelectric ceramic composition decreases, resulting in high firing. A sintering temperature is required. Also, M
Is too large, the Curie temperature is lowered, and the heat resistance of the piezoelectric ceramic composition is greatly deteriorated, which is not preferable in practical use. From this viewpoint, the atomic ratio α of M is 0 <α
≦ 0.1, preferably 0.01 ≦ α ≦
0.1, particularly preferably 0.02 ≦ α ≦ 0.05.

The dielectric constant increases as the atomic ratio x of (Mg _1/3 Nb _2/3 ) in the piezoelectric ceramic composition of the present invention increases, but when it exceeds 0.40, the Nb raw material is expensive. Therefore, it is not suitable for industrial mass production. On the other hand, when the atomic ratio x is less than 0.01, the dielectric constant and the electromechanical coupling coefficient of the piezoelectric ceramic composition are low, and the required piezoelectric characteristics cannot be obtained. In addition, Ti and Zr
Has a large effect on the dielectric constant and electromechanical coupling coefficient of the piezoelectric ceramic composition, and is particularly preferably near the morphotropic phase boundary (MPB).
Accordingly, the piezoelectric ceramic composition of the present invention has a high dielectric constant and a high electromechanical coupling coefficient, and can provide a piezoelectric ceramic composition having excellent basic piezoelectric characteristics. The atomic ratio x, y, z in the product is 0.01 ≦ x ≦ 0.4
0, 0.30 ≦ y ≦ 0.50, 0.20 ≦ z ≦ 0.55
(However, it is necessary that x + y + z = 1).
In particular, when the application of the piezoelectric ceramic composition requires particularly high dielectric constant and electromechanical coupling coefficient, the atomic ratio ranges are 0.1 ≦ x ≦ 0.3, 0.35 ≦ y ≦ 0. .
45, 0.30 ≦ z ≦ 0.40 (where x + y + z =
1) is preferable.

In the present invention, Pd, Nb ₂ O ₅ , Fe ₂ O ₃ , Sb ₂ O ₃ , V ₂ are added to the perovskite-type oxide composition represented by the above basic composition formula as additives.
It is characterized by adding a metal or oxide selected from O ₅ , WO ₃ , PbSiO ₃ , Ta ₂ O ₅ , Cr ₂ O ₃ and SiO ₂ . By adding these specific additives in specific amounts, the mechanical strength can be significantly improved while maintaining good piezoelectric properties of the piezoelectric ceramic composition. _{Pd, Nb 2 O 5, Fe} 2 O 3, Sb 2 O 3, V 2 O 5, W
When using at least one metal or oxide selected from O ₃ , PbSiO ₃ , Ta ₂ O ₅ and Cr ₂ O ₃ , the weight is based on the weight of the oxide composition represented by the above basic composition formula. , 0.05 to 1.0% by weight, while when SiO ₂ is used, 0.005 to 1.0% by weight.
It is preferable to add 0.1% by weight. These additives are
They may be added alone or, if necessary, in combination of two or more. Additives other than SiO ₂ Pd, N
_{b 2 O 5, Fe 2 O} 3, Sb 2 O 3, V 2 O 5, WO 3, PbS
When two or more of iO ₃ , Ta ₂ O ₅ and Cr ₂ O ₃ are used in combination, the total amount of addition is 0.05-1.
It is preferably 0% by weight. In addition, SiO ₂ and P
d, Nb ₂ O ₅ , Fe ₂ O ₃ , Sb ₂ O ₃ , V ₂ O ₅ , WO ₃ ,
When using in combination with at least one of PbSiO ₃ , Ta ₂ O ₅ and Cr ₂ O ₃ , the total added amount is preferably 0.055 to 1.1% by weight. P
d, Nb ₂ O ₅ , Fe ₂ O ₃ , Sb ₂ O ₃ , V ₂ O ₅ , WO ₃ ,
The amount of PbSiO ₃ , Ta ₂ O ₅ or Cr ₂ O ₃ is 0.05
If the amount of SiO ₂ is less than 0.005% by weight, the technical effect as an additive is not recognized, while Pd, Nb ₂ O ₅ , Fe ₂ O ₃ , Sb ₂ O ₃ , V ₂
When the amount of O ₅ , WO ₃ , PbSiO ₃ , Ta ₂ O ₅ or Cr ₂ O ₃ exceeds 1.0% by weight, and when the amount of SiO ₂ exceeds 0.1% by weight, the dielectric constant and electromechanical coupling The coefficient decreases.

The piezoelectric ceramic composition of the present invention is preferably produced by the method described below. As a starting material, it is preferable to use an oxide composed of elements constituting the piezoelectric ceramic composition of the present invention, but if necessary, use a compound such as carbonate which can be converted into a desired oxide by firing. Can also. These raw materials are weighed so as to have a predetermined ratio, and are wet-mixed using a ball mill or the like. The additive of the present invention may be added at the time of wet mixing, or may be added after calcination described below. As the slurry medium used in the wet mixing, it is desirable to use water or an alcohol such as ethanol alone or a mixed medium of water and alcohol.

After thoroughly mixing the starting materials, about 800 to
The calcined product is calcined at 1000 ° C. for about 1 to 3 hours to obtain a slurry, which is wet-ground using a ball mill or the like.
As the slurry medium at this time, as described above,
It is desirable to use water or an alcohol such as ethanol alone or a mixed medium of water and alcohol. The wet pulverization at this time is preferably performed until the average particle size of the pulverized particles of the calcined product becomes about 0.5 to 2.0 μm.

After the wet pulverization, the powder of the calcined product is dried, and a small amount of water or a suitable binder, for example, 0.5 to 8% by weight is added to the dried product, and the dried product is 98 to 392 MPa (1 to 4 MPa).
(a converted value of ton / cm ² ) under pressure to obtain a molded body. In addition, as a molding method, an extrusion molding method,
Other molding methods commonly used in the art can be utilized. As the binder here, for example,
What melt | dissolved polyvinyl alcohol in water can be used.

Next, the thus obtained molded body is fired to obtain a piezoelectric ceramic. The sintering temperature may be lower than the conventional one, and can be preferably selected from the range of about 1060 to 1200 ° C. The firing time is preferably about 1 to 4 hours. The sintering may be performed in the air, and in some cases, may be performed in an atmosphere having a higher oxygen partial pressure than in the air or in a pure oxygen atmosphere. As described above, the piezoelectric ceramic of the present invention can be manufactured through the steps of wet mixing, calcination, wet pulverization, molding, and firing.

[0018]

The present invention will be described below in detail with reference to examples.
I do.Examples 1 to 45 and Comparative Examples 1 to 11 In the following examples, PbO, TiO_Two, ZrO_Two, Mg
O, Nb_TwoO_Five, SrCO _Three, CaCO_Three, BaCO_Three, L
a_TwoO_Three, Pd, SiO_Two, PbSiO_Three, Fe_TwoO_Three, WO
_Three, Ta_TwoO_Five, Sb_TwoO_Three, V_TwoO_Five, And Cr_TwoO_ThreeFrom
Selected and used. These starting materials have an average particle size of about 1
５5 μm. Table 1 shows the final composition of the starting material powder.
Formulated to give the composition shown, wet using a ball mill
Mixed. Water is used as the slurry medium during wet mixing
Was. Next, the mixture was calcined at 900 ° C. for 2 hours,
The obtained calcined product is cooled until the average particle size becomes 1.5 μm.
It was wet-ground with a ball mill. In the case of wet grinding, slurry
-Water was used as the medium. Dry the resulting slurry
Thereafter, 6% by weight of water was added to the powdery dried product, and the pressure was 39.
2MPa (400kgf / cm^TwoUniaxial pressurization)
Molding and then 392 MPa (4 ton / cm^TwoExchange
Cold-isostatic pressing at a pressure of (calculated value) 17 mm in diameter and height
A 20 mm cylindrical molded product was obtained. Each obtained in this way
The molded body is fired in the air at the temperature shown in Table 1 for 2 hours.
Then, a sample of the piezoelectric ceramic of the present invention was obtained.

The density of these piezoelectric ceramics was measured by the Archimedes method. Table 1 shows the measurement results.
Shown in Each of the piezoelectric ceramic samples obtained above was sliced to a thickness of 0.1 mm using a slicing and lapping machine.
After processing into a 6mm disk-shaped sample, A
g paste was applied and baked at 650 ° C. for 10 minutes. Next, a polarization treatment was performed on the thus treated disc by applying an electric field of 3 kv / mm in silicone oil at 120 ° C. for 15 minutes to obtain a measurement sample. For each sample subjected to the polarization treatment, the relative permittivity εd and the electromechanical coupling coefficient kr of the radial vibration were measured using an impedance analyzer HP4194A (manufactured by YHP).
Was measured. These relative dielectric constants and electromechanical coupling coefficients were determined according to EMAS-6100. Table 1 shows the results.

Next, in order to conduct a strength test, the piezoelectric ceramic obtained above was separately sliced, wrapped, and diced to 2.0 mm long and 4.0 mm wide.
A sample having a size of 0.6 mm and a thickness of 0.6 mm was prepared.
This sample was subjected to a flexural strength test using a digital load tester according to JIS (R1601) using a three-point bending measurement method. The measurement condition was 2.0 m between fulcrums.
m, and the load speed was 0.5 mm / min. Table 1 shows the results.
Shown in

[Table 1]

As can be seen from Table 1, the piezoelectric ceramic of the present invention was excellent in relative dielectric constant εd, electromechanical coupling coefficient kr, and bending strength.

[0022]

According to the piezoelectric ceramic composition of the present invention, by selecting and adding the above-mentioned specific additives, the relative dielectric constant .di-elect cons.d is large, the piezoelectric constant d is large, and the piezoelectric characteristics are excellent. The electromechanical coupling coefficient kr and the flexural strength are both high, and the mechanical strength is excellent. The present invention is a piezoelectric ceramic which maintains the excellent piezoelectric properties of the prior art and has significantly improved mechanical strength. A composition can be provided. In addition, it is possible to fire at a lower temperature than the piezoelectric ceramic composition of the prior art, which is industrially very advantageous.

Since the piezoelectric ceramic composition of the present invention is particularly excellent in strength, even when it is used particularly for a small or thin actuator, defects such as cracking and chipping occur, and even when driving, High reliability without breakage. In particular, it can be said that the present invention fulfills an extremely high industrial significance in a technical field such as a hard disk drive head of a computer, which requires ultra-miniaturization and ultra-thin layers.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenji Horino 1-13-1 Nihombashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Masaru Nanao 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK In-house (72) Inventor Shogo Murosawa 1-13-1 Nihombashi, Chuo-ku, Tokyo BA10

Claims (3)

[Claims] A perovskite oxide containing lead as a main component
And the basic composition formula: Pb_(1-a)[(Mg_1/3Nb_2/3)_xTi_yZr_z] O_Three (Where a, x, y, and z are the following conditions: 0 ≦ a ≦ 0.05, 0.01 ≦ x ≦ 0.40, 0.30 ≦ y ≦ 0.50, 0.20 ≦ z ≦ 0.55, which is an atomic ratio satisfying x + y + z = 1).
d, Nb_TwoO_Five, Fe_TwoO_Three, Sb_TwoO_Three, V_TwoO_Five, WO_Three,
PbSiO_Three, Ta_TwoO_FiveAnd Cr_TwoO_ThreeSelected from
0.05 to 1.0 at least one metal or oxide
% By weight, or SiO _TwoFrom 0.005 to 0.1% by weight,
Or SiO_TwoAnd at least one of said metals or oxidation
And a total of 0.055 to 1.1% by weight
A piezoelectric ceramic composition characterized by the following: 2. Main component is a perovskite oxide containing lead.
And the basic composition formula: (Pb_{(1-a- α )}M_α) [(Mg_1/3Nb_2/3)_xTi_yZr
_z] O_Three Where M is selected from Sr, Ca, Ba and La
Α represents 0 <α ≦ 0.1.
And a, x, y, z are the following conditions: 0 ≦ a ≦ 0.05, 0.01 ≦ x ≦ 0.40, 0.30 ≦ y ≦ 0.50, 0.20 ≦ z ≦ 0.55, which is an atomic ratio satisfying x + y + z = 1).
d, Nb_TwoO_Five, Fe_TwoO_Three, Sb_TwoO_Three, V_TwoO_Five, WO_Three,
PbSiO_Three, Ta_TwoO_FiveAnd Cr_TwoO_ThreeSelected from
0.05 to 1.0 at least one metal or oxide
% By weight, or SiO _TwoFrom 0.005 to 0.1% by weight,
Or SiO_TwoAnd at least one of said metals or oxidation
And a total of 0.055 to 1.1% by weight
A piezoelectric ceramic composition characterized by the following: 3. The piezoelectric ceramic composition according to claim 2, wherein α is 0.01 ≦ α ≦ 0.1.