JP2005132704A - Piezoelectric ceramic and piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic and a piezoelectric element which can improve piezoelectric characteristics and mechanical strength. <P>SOLUTION: The piezoelectric ceramic mainly consists of Pb<SB>a</SB>[(Zn<SB>1/3</SB>Nb<SB>2/3</SB>)<SB>x</SB>Ti<SB>y</SB>Zr<SB>z</SB>]O<SB>3</SB>(wherein, a, x, y and z satisfy following inequalities: 0.96≤a≤1.03; x+y+z=1; 0.05≤x≤0.40; 0.1≤y≤0.5; and 0.2≤z≤0.6) and contains W of 0.05 to 3 mass% per a main component in terms of WO<SB>3</SB>as a first sub-component. As for the main component, a portion of Pb may be substituted with at least one kind of Sr, Ba and Ca. Further, the piezoelectric ceramic may contain at least one kind of Ta, Sb and Nb of 0.2 to 1.0 mass% per the main component in terms of their oxides as a second sub-component. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a piezoelectric ceramic and a piezoelectric element suitable for actuators, piezoelectric buzzers, sounding bodies, sensors, and the like.

  2. Description of the Related Art Conventionally, there is an actuator that uses a displacement generated by a piezoelectric effect as a mechanical drive source. In particular, multilayer actuators in which a piezoelectric layer and internal electrodes are laminated have lower power consumption and heat generation than electromagnetic actuators, have good responsiveness, and can be reduced in size and weight. Is used in various fields such as needle selection control of textile knitting machines.

Piezoelectric ceramics used in these actuators are required to have a large piezoelectric characteristic, particularly a piezoelectric strain constant. Examples of piezoelectric ceramics that can obtain a large piezoelectric strain constant include lead titanate (PbTiO ₃ ; PT), lead zirconate (PbZrO ₃ ; PZ), and zinc niobate (Pb (Zn _1/3 Nb _2/3). ) O ₃ ) ternary system (see Patent Document 1 and Patent Document 2), or a part of its lead (Pb) is replaced with strontium (Sr), barium (Ba), calcium (Ca), etc. (See Patent Literature 3, Patent Literature 4 and Patent Literature 5).
Japanese Examined Patent Publication No. 44-17344 JP 2001-181035 A Japanese Patent Publication No. 45-39977 JP 61-129888 A JP 2001-181036 A

  However, in recent years, there has been a problem that the piezoelectric element has been miniaturized and thinned, and thereby the mechanical strength of the element has been lowered, and the possibility of breakage during manufacturing and driving has increased. In particular, an actuator for controlling a minute position of a head of a hard disk drive has a problem that its strength is partially weak because of its complicated shape. Therefore, there is a need for a piezoelectric ceramic with higher mechanical strength in order to prevent a decrease in manufacturing yield and a decrease in product reliability. In addition, in order to reduce the size and thickness of the piezoelectric element, development of a piezoelectric ceramic having a larger generated displacement is also required.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a piezoelectric ceramic and a piezoelectric element capable of improving piezoelectric characteristics and mechanical strength.

（化１において、ａ，ｘ，ｙ，ｚは、０．９６≦ａ≦１．０３、ｘ＋ｙ＋ｚ＝１、０．０５≦ｘ≦０．４０、０．１≦ｙ≦０．５、０．２≦ｚ≦０．６をそれぞれ満たす範囲内の値である。） The first piezoelectric ceramic according to the present invention, with respect to 1 represented by the composition, tungsten (W) oxide (WO ₃₎ Conversion to the following 3.00% by weight 0.05% by weight or more It is contained within the range.

(In the chemical formula 1, a, x, y and z are 0.96 ≦ a ≦ 1.03, x + y + z = 1, 0.05 ≦ x ≦ 0.40, 0.1 ≦ y ≦ 0.5, 0. (It is a value within the range satisfying 2 ≦ z ≦ 0.6.)

（化２において、ａ，ｂ，ｘ，ｙ，ｚは、０．９６≦ａ≦１．０３、０＜ｂ＜ａ、ｘ＋ｙ＋ｚ＝１、０．０５≦ｘ≦０．４０、０．１≦ｙ≦０．５、０．２≦ｚ≦０．６をそれぞれ満たす範囲内の値である。Ｍｅは、ストロンチウム（Ｓｒ），バリウム（Ｂａ）およびカルシウム（Ｃａ）からなる群のうちの少なくとも１種を表す。） In the second piezoelectric ceramic according to the present invention, tungsten is converted to an oxide (WO ₃ ) with respect to the composition represented by Chemical Formula 2 within a range of 0.05% by mass or more and 3.00% by mass or less. It contains.

(In the chemical formula 2, a, b, x, y, and z are 0.96 ≦ a ≦ 1.03, 0 <b <a, x + y + z = 1, 0.05 ≦ x ≦ 0.40, 0.1 ≦ y ≦ 0.5 and 0.2 ≦ z ≦ 0.6, Me is at least one of the group consisting of strontium (Sr), barium (Ba), and calcium (Ca). Represents a species.)

In these piezoelectric ceramics according to the present invention, at least one member selected from the group consisting of tantalum (Ta), antimony (Sb) and niobium (Nb) is oxidized with respect to the composition represented by chemical formula 1 or chemical formula 2. It is preferable to contain in the range of 0.2 mass% or more and 1.0 mass% or less in total in terms of products (Ta ₂ O ₅ , Sb ₂ O ₃ , Nb ₂ O ₅ ).

  The piezoelectric element according to the present invention uses the piezoelectric ceramic according to the present invention.

  According to the piezoelectric ceramic of the present invention, since the predetermined amount of tungsten is contained in the composition represented by chemical formula 1 or chemical formula 2, the piezoelectric characteristics and mechanical strength can be improved. Therefore, if the piezoelectric ceramic of the present invention is used, the piezoelectric element can be reduced in size and thickness, and the manufacturing yield and product reliability can be improved even if the piezoelectric element is reduced in size and thickness.

  In particular, in the piezoelectric ceramic according to the present invention, if a composition represented by Chemical Formula 2 in which a part of lead is substituted with at least one selected from the group consisting of strontium, barium and calcium is included, the piezoelectric characteristics and The mechanical strength can be further improved.

  In addition to tungsten, if a predetermined amount of at least one member selected from the group consisting of tantalum, antimony and niobium is contained, the mechanical strength can be further improved.

  Hereinafter, embodiments of the present invention will be described in detail.

  The piezoelectric ceramic according to one embodiment of the present invention contains a composition represented by Chemical Formula 3 or Chemical Formula 4 as a main component.

化３において、ａ，ｘ，ｙ，ｚは、０．９６≦ａ≦１．０３、ｘ＋ｙ＋ｚ＝１、０．０５≦ｘ≦０．４０、０．１≦ｙ≦０．５、０．２≦ｚ≦０．６をそれぞれ満たす範囲内の値である。酸素の組成は化学量論的に求めたものであり、化学量論組成からずれていてもよい。

In the chemical formula 3, a, x, y, z are 0.96 ≦ a ≦ 1.03, x + y + z = 1, 0.05 ≦ x ≦ 0.40, 0.1 ≦ y ≦ 0.5, 0.2 It is a value within a range satisfying ≦ z ≦ 0.6. The composition of oxygen is determined stoichiometrically and may deviate from the stoichiometric composition.

化４において、ａ，ｂ，ｘ，ｙ，ｚは、０．９６≦ａ≦１．０３、０＜ｂ＜ａ、ｘ＋ｙ＋ｚ＝１、０．０５≦ｘ≦０．４０、０．１≦ｙ≦０．５、０．２≦ｚ≦０．６をそれぞれ満たす範囲内の値である。Ｍｅは、ストロンチウム，バリウムおよびカルシウムからなる群のうちの少なくとも１種を表す。酸素の組成は化学量論的に求めたものであり、化学量論組成からずれていてもよい。

In Formula 4, a, b, x, y, and z are 0.96 ≦ a ≦ 1.03, 0 <b <a, x + y + z = 1, 0.05 ≦ x ≦ 0.40, 0.1 ≦ y. It is a value within a range satisfying ≦ 0.5 and 0.2 ≦ z ≦ 0.6. Me represents at least one selected from the group consisting of strontium, barium and calcium. The composition of oxygen is determined stoichiometrically and may deviate from the stoichiometric composition.

  The composition represented by Chemical Formula 3 or Chemical Formula 4 has a perovskite structure, and lead, strontium, barium and calcium are located at the A site of the so-called perovskite structure, and zinc (Zn), niobium, titanium (Ti) and Zirconium (Zr) is located at the B site of the so-called perovskite structure.

  The composition represented by the chemical formula 4 is obtained by substituting a part of lead in the composition represented by the chemical formula 3 with at least one selected from the group consisting of strontium, barium, and calcium. It is intended to improve the mechanical strength.

The composition a of lead in chemical formula 3 or the composition a of lead and at least one member selected from the group consisting of strontium, barium and calcium in chemical formula 4 is an element located at a so-called B site, that is, [(Zn _1/3 Nb _2/3) is a composition ratio of the element that is located in a so-called a-site in the case of the 1 the composition of _x Ti _y Zr _z]. The reason why a is 0.96 or more and 1.03 or less is that high piezoelectric characteristics can be obtained within this range.

  In Formula 4, b, that is, the substitution amount of at least one member selected from the group consisting of strontium, barium and calcium is preferably 0.01 or more and 0.10 or less. If it is less than 0.01, the effect of improving the piezoelectric characteristics and the mechanical strength cannot be sufficiently obtained, and if it exceeds 0.10, the sinterability is lowered, and thereby the piezoelectric characteristics are also lowered. Because.

Zinc and niobium (Zn _1/3 Nb _2/3 ) in Chemical Formula 3 or Chemical Formula 4 are for improving piezoelectric characteristics. The reason why the composition x is 0.05 or more is that sufficient piezoelectric characteristics cannot be obtained if the composition x is less than 0.05. In addition, if the composition x is 0.40 or less, if it exceeds 0.40, a large amount of expensive niobium oxide must be used, resulting in an increase in manufacturing cost and a decrease in piezoelectric strain constant. Because.

  The titanium composition y in chemical formula 3 or chemical formula 4 is 0.1 or more and 0.5 or less, and the zirconium composition z is 0.2 or more and 0.6 or less in the vicinity of the morphotropic phase boundary (MPB) within this range. This is because a high piezoelectric characteristic can be obtained.

The piezoelectric ceramic also contains tungsten as the first subcomponent. This first subcomponent is for improving the piezoelectric characteristics and mechanical strength, and for controlling the heat shrinkage during sintering. The content of tungsten as the first subcomponent is in the range of 0.05% by mass to 3.00% by mass in terms of oxide (WO ₃ ) with respect to the composition shown in Chemical Formula 3 or Chemical Formula 4. It is preferably within the range, more preferably within the range of 0.10% by mass to 2.00% by mass, and even more preferably within the range of 0.30% by mass to 1.00% by mass. If the amount is less than 0.05% by mass, a sufficient effect cannot be obtained, and if it exceeds 3.00% by mass, the piezoelectric characteristics and the mechanical strength are deteriorated. Tungsten as the first subcomponent is dissolved in the main component composition, and is located at a so-called B site where titanium and zirconium can exist.

The piezoelectric ceramic preferably further contains at least one selected from the group consisting of tantalum, antimony and niobium as the second subcomponent. This is because the piezoelectric properties and mechanical strength can be further improved by adding in addition to the first subcomponent. The content of the second subcomponent is 0.2 in total in terms of oxide (Ta ₂ O ₅ , Sb ₂ O ₃ , Nb ₂ O ₅ ) with respect to the composition shown in chemical formula 3 or chemical formula 4. It is preferable to be in the range of not less than mass% and not more than 1.0 mass%. If the amount is less than 0.2% by mass, the effect of the addition cannot be sufficiently obtained. If the amount exceeds 1.0% by mass, the sinterability is lowered and the piezoelectric characteristics are lowered. The second subcomponent is also dissolved in the main component composition in the same manner as the first subcomponent, and is located at a so-called B site where titanium and zirconium can exist.

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

First, for example, lead oxide (PbO) powder, zinc oxide (ZnO) powder, niobium oxide (Nb ₂ O ₅ ) powder, titanium oxide (TiO ₂ ) powder, and zirconium oxide (ZrO ₂ ) powder are used as the main component raw materials. At the same time, at least one member selected from the group consisting of strontium carbonate (SrCO ₃ ) powder, barium carbonate (BaCO ₃ ) powder and calcium carbonate (CaCO ₃ ) powder is prepared as necessary.

In addition, for example, tungsten oxide (WO ₃ ) powder is prepared as a raw material for the first subcomponent, and for example, tantalum oxide (Ta ₂ O ₅ ) powder, antimony oxide is used as a second subcomponent raw material as necessary. At least one selected from the group consisting of (Sb ₂ O ₃ ) powder and niobium oxide powder is prepared. The raw materials for these main component, first subcomponent, and second subcomponent may be those that become oxides upon firing, such as carbonates, oxalates, or hydroxides, instead of oxides. Further, instead of carbonates, oxides or other substances that become oxides upon firing may be used.

  Next, after sufficiently drying these raw materials, the final composition is weighed so as to be in the above-described range, and the raw material of the main component, the first subcomponent raw material, and the second subcomponent raw material as necessary are ball milled. Then, the mixture is thoroughly mixed in an organic solvent or in water and dried, and calcined at 700 to 950 ° C. for 1 to 4 hours. Subsequently, for example, the calcined material is sufficiently pulverized in an organic solvent or water by a ball mill or the like, dried, and then granulated by adding a binder such as polyvinyl alcohol, and then a uniaxial press molding machine or a hydrostatic pressure molding machine. (CIP) or the like is used for press molding. After molding, for example, the molded body is preferably fired in an air atmosphere at 1000 ° C. to 1200 ° C. for 1 hour to 4 hours. Note that the firing atmosphere may be such that the oxygen partial pressure is higher than that in the air or in pure oxygen. After firing, the obtained sintered body is polished as necessary, provided with a polarization electrode, and subjected to polarization treatment by applying an electric field in heated silicone oil. After that, the above-mentioned piezoelectric ceramic is obtained by removing the electrode for polarization.

  Such a piezoelectric ceramic is preferably used as a material for a piezoelectric element such as an actuator, a piezoelectric buzzer, a sounding body, and a sensor, particularly as a material for an actuator.

  FIG. 1 shows a configuration example of a piezoelectric element using a piezoelectric ceramic according to the present embodiment. The piezoelectric element includes a laminated body 10 in which a plurality of internal electrodes 12 are inserted between a plurality of piezoelectric layers 11 made of the piezoelectric ceramic according to the present embodiment, for example. The thickness per layer of the piezoelectric layer 11 is, for example, about 1 μm to 100 μm, and the piezoelectric layers 11 at both ends may be formed thicker than the piezoelectric layer 11 sandwiched between the internal electrodes 12.

  The internal electrode 12 contains a conductive material. Although the conductive material is not particularly limited, for example, at least one selected from the group consisting of silver (Ag), gold (Au), platinum and palladium, or an alloy thereof is preferable. The internal electrode 12 may contain about 0.1% by mass or less of various trace components such as phosphorus (P) in addition to these conductive materials.

  For example, the internal electrodes 12 are alternately extended in opposite directions, and a pair of terminal electrodes 21 and 22 electrically connected to the internal electrode 12 are provided in the extending direction. The terminal electrodes 21 and 22 may be formed, for example, by sputtering a metal such as gold, or may be formed by baking a terminal electrode paste. The terminal electrode paste includes, for example, a conductive material, a glass frit, and a vehicle. The conductive material includes, for example, at least one selected from the group consisting of silver, gold, copper, nickel, palladium, and platinum. Those are preferred. Examples of the vehicle include an organic vehicle and an aqueous vehicle. The organic vehicle is obtained by dissolving a binder in an organic solvent, and the aqueous vehicle is obtained by dissolving a water-soluble binder and a dispersant in water. The thicknesses of the terminal electrodes 21 and 22 are appropriately determined according to the application and the like, but are usually about 10 μm to 50 μm.

  This piezoelectric element can be manufactured as follows, for example. First, a pre-fired powder is formed in the same manner as in the piezoelectric ceramic manufacturing method described above, and a vehicle is added thereto and kneaded to prepare a piezoelectric layer paste. Next, the above-described conductive material for forming the internal electrode 12 or various oxides, organometallic compounds, resinates, or the like that become the above-described conductive material after firing are kneaded with a vehicle to prepare an internal electrode paste. Note that additives such as a dispersant, a plasticizer, a dielectric material, and an insulator material may be added to the internal electrode paste as necessary.

  Subsequently, using these piezoelectric layer paste and internal electrode paste, a green chip which is a precursor of the laminate 10 is manufactured by, for example, a printing method or a sheet method. After that, a binder removal process is performed, and the laminate 10 is formed by firing.

  After the laminated body 10 is formed, terminal polishing is performed by, for example, barrel polishing or sand blasting and sputtering of a metal such as gold, or printing or transferring a terminal electrode paste produced in the same manner as the internal electrode paste. Then, terminal electrodes 21 and 22 are formed by baking. Thereby, the piezoelectric element shown in FIG. 1 is obtained.

  As described above, according to the present embodiment, the composition represented by Chemical Formula 3 or Chemical Formula 4 is used as the main component, and a predetermined amount of tungsten is contained as the first subcomponent. Can be improved. Therefore, the piezoelectric element can be further reduced in size and thickness, and the manufacturing yield and product reliability can be improved even if the piezoelectric element is reduced in size and thickness.

  Moreover, if a composition represented by the chemical formula 4 in which a part of lead is substituted with at least one selected from the group consisting of strontium, barium and calcium, the piezoelectric characteristics and the mechanical strength are further improved. be able to.

  Furthermore, if a predetermined amount of at least one selected from the group consisting of tantalum, antimony and niobium is contained as the second subcomponent, the mechanical strength can be further improved.

  Furthermore, specific examples of the present invention will be described.

(Examples 1-1 to 1-7)
A piezoelectric ceramic containing the composition shown in Chemical Formula 5 as a main component and tungsten as the first subcomponent was produced. First, lead oxide powder, strontium carbonate powder, titanium oxide powder, zirconium oxide powder, zinc oxide powder and niobium oxide powder were prepared as raw materials of the main components, and weighed so as to have the composition shown in Chemical formula 5. In addition, tungsten oxide powder is prepared as a raw material for the first subcomponent, and the ratio of the main component converted to oxide (WO ₃ ) is changed as shown in Table 1 in Examples 1-1 to 1-7. Weighed.

  Next, these raw materials were wet-mixed for 16 hours using a ball mill and then calcined at 700 ° C. to 900 ° C. for 2 hours in the air. Subsequently, the calcined product was wet pulverized for 16 hours using a ball mill and dried, and then granulated by adding polyvinyl alcohol as a binder. The diameter was 17 mm and the thickness was about 245 MPa using a uniaxial press molding machine. Molded into a 1 mm disk. After molding, the binder was volatilized by heat treatment, and then calcined at 1150 ° C. for 2 to 4 hours in the air. After that, the obtained sintered body was formed into a disk shape having a thickness of 0.6 mm by slicing and lapping, and silver paste was printed on both sides and baked at 650 ° C., and 3 kV / mm in 120 ° C. silicone oil. An electric field was applied for 15 minutes to perform polarization treatment. This obtained the piezoelectric ceramic of Examples 1-1 to 1-7.

  The obtained piezoelectric ceramics of Examples 1-1 to 1-7 were allowed to stand for 24 hours, and then the electromechanical coupling coefficient kr and the relative dielectric constant εr of radial vibration were measured. For these measurements, an impedance analyzer (HP4194A manufactured by Hewlett-Packard Company) was used, and the frequency when measuring the relative dielectric constant εr was 1 kHz.

  Further, a square plate of 2 mm × 4 mm × 0.6 mm was cut out from the sintered body before printing the electrode, and the bending strength was measured by a three-point bending measurement method. The measurement conditions were a distance between fulcrums of 2.0 mm and a load speed of 0.5 mm / min. The results are shown in Table 1 and FIGS.

As Comparative Example 1-1 for this example, a piezoelectric ceramic was manufactured in the same manner as in Examples 1-1 to 1-7, except that tungsten oxide was not added. Moreover, as Comparative Example 1-2 with respect to the present Example, Examples 1-1 to 1- 1 except that the addition amount of tungsten oxide was set to 4% by mass with respect to the main component converted to oxide (WO ₃ ). A piezoelectric ceramic was produced in the same manner as in FIG. For Comparative Examples 1-1 and 1-2, similarly to Examples 1-1 to 1-7, the electromechanical coupling coefficient kr, the relative dielectric constant εr, and the bending strength of radial vibration were measured. The results are shown in Table 1 and FIGS.

  As shown in Table 1 and FIGS. 2 and 3, according to Examples 1-1 to 1-7, high values of 28.2 or higher for kr × √εr and 80 MPa or higher for bending strength were obtained. It was. In contrast, Comparative Example 1-1 containing no tungsten and Comparative Example 1-2 containing a large amount of tungsten were both inadequate values lower than these.

That is, tungsten is converted into an oxide (WO ₃ ) with respect to the main component within a range of 0.05% by mass or more and 3.00% by mass or less, more preferably 0.10% by mass or more and 2.00% by mass. It has been found that the piezoelectric characteristics and mechanical strength can be improved by containing within the following range, more preferably within the range of 0.30 mass% or more and 1.00 mass% or less.

(Examples 2-1 to 2-3)
In the same manner as in Examples 1-1 to 1-7, in Example 2-1, the composition shown in Chemical Formula 6 was the main component, and in Example 2-2, the composition shown in Chemical Formula 7 was the main component, In Example 2-3, a piezoelectric ceramic containing the composition shown in Chemical Formula 8 as the main component and tungsten as the first subcomponent was produced. At that time, barium carbonate powder was used as a raw material for barium, and calcium carbonate powder was used as a raw material for calcium. In Examples 2-1 to 2-3, the content of tungsten was set to 0.5% by mass with respect to the main component converted to oxide (WO ₃ ).

  Further, as Comparative Examples 2-1 to 2-3 for Examples 2-1 to 2-3, piezoelectric ceramics were produced in the same manner as in Examples 2-1 to 2-3, except that tungsten was not added. Of these, Comparative Example 2-1 corresponds to Example 2-1, Comparative Example 2-2 corresponds to Example 2-2, and Comparative Example 2-3 corresponds to Example 2-3.

  Regarding Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-3, the electromechanical coupling coefficient kr and the relative dielectric constant of radial vibration were also the same as in Examples 1-1 to 1-7. εr and bending strength were measured. The results are shown in Tables 2-4.

  As shown in Tables 2 to 4, according to Examples 2-1 to 2-3, similarly to Examples 1-1 to 1-7, kr × √εr is 28.2 or more, bending strength On the other hand, while a high value of 80 MPa or more was obtained, in Comparative Examples 2-1 to 2-3 not containing tungsten, all were insufficient values smaller than these.

  That is, in the case where the composition shown in Chemical Formula 6, Chemical Formula 7 or Chemical Formula 8 is included as the main component, as in the case where the composition shown in Chemical Formula 5 is included, if a predetermined amount of tungsten is contained, the piezoelectricity It has been found that properties and mechanical strength can be improved.

  Table 5 compares Example 1-4 shown in Table 1 with Examples 2-1 to 2-3 shown in Tables 2 to 4. As can be seen from Table 5, Examples 1-4, 2-2, and 2-3 in which a part of lead is replaced with strontium, barium, or calcium are more kr than those in Examples 2-1 that are not substituted. Large values were obtained for both x√εr and bending strength. That is, it was found that the piezoelectric characteristics and mechanical strength can be further improved by replacing a part of lead with strontium, barium or calcium.

(Examples 3-1 to 3-4)
In the same manner as in Examples 1-1 to 1-7, a piezoelectric ceramic containing the composition shown in Chemical Formula 9 as a main component, containing tungsten as the first subcomponent, and containing tantalum, antimony or niobium as the second subcomponent. Was made. Content of tungsten is a ratio with respect to the main component converted into an oxide (WO ₃ ). Examples 3-1, 3-3, 3-4 are 0.5% by mass, and Example 3-2 is 2% by mass. It was. The second subcomponent is tantalum in Examples 3-1 and 3-2, antimony in Example 3-3, and niobium in Example 3-4. These raw materials are tantalum oxide powder, antimony oxide powder, and niobium oxide powder. Was used. The content of the second subcomponent is 0 as a ratio to the main component in terms of oxide (Ta ₂ O ₅ , Sb ₂ O ₃ , Nb ₂ O ₅ ) in any of Examples 3-1 to 3-4. .2% by mass.

  Further, as Comparative Examples 3-1 to 3-3 for Examples 3-1 to 3-4, piezoelectric ceramics were manufactured in the same manner as in Examples 3-1 to 3-4, except that tungsten was not added. Of these, Comparative Example 3-1 corresponds to Examples 3-1 and 3-2, Comparative Example 3-2 corresponds to Example 3-3, and Comparative Example 3-3 corresponds to Example 3-4. ing.

  For Examples 3-1 to 3-4 and Comparative Examples 3-1 to 3-3, the electromechanical coupling coefficient kr and the relative dielectric constant of radial vibration were also the same as in Examples 1-1 to 1-7. εr and bending strength were measured. The results are shown in Tables 6-8.

  As shown in Tables 6 to 8, according to Examples 3-1 to 3-4, similarly to Examples 1-1 to 1-7, kr × √εr is 28.2 or more, bending strength A high value of 80 MPa or more was obtained. On the other hand, in Comparative Example 2-1, which did not contain tungsten, a high value was obtained in the same manner, but was lower than in Examples 3-1 and 3-2. In Comparative Examples 2-2 and 2-3, kr × √εr was lower than 28.2 and the bending strength was 80 MPa or more, but was lower than those in Examples 3-3 and 3-4. .

  Further, Table 9 shows a comparison between Example 1-4 shown in Table 1 and Examples 3-1, 3-3, 3-4 shown in Tables 6-8. As can be seen from Table 9, the examples 3-1, 3-3 and 3-4 to which the second subcomponent was added had a greater bending resistance than the examples 1-4 to which the second subcomponent was not added. The strength could be obtained. Moreover, according to Example 3-1, in which tantalum was added as the second subcomponent, a higher value was obtained for kr × √εr.

  That is, it was found that the mechanical strength could be further improved by including tungsten and at least one member selected from the group consisting of tantalum, antimony and niobium. This is considered to be due to a synergistic effect of the first subcomponent and the second subcomponent.

(Examples 4-1 and 4-2)
In the same manner as in Examples 1-1 to 1-7, in Example 4-1, the composition shown in Chemical formula 10 was the main component, and in Example 4-2, the composition shown in Chemical formula 11 was the main component, A piezoelectric ceramic containing tungsten as the first subcomponent and tantalum as the second subcomponent was produced. At that time, barium carbonate powder was used as the barium raw material, calcium carbonate powder was used as the calcium raw material, and tantalum oxide powder was used as the tantalum raw material. In Examples 4-1 and 4-2, the content of tungsten is 0.5% by mass with respect to the main component in terms of oxide (WO ₃ ), and the content of tantalum is oxide (Ta ₂ O _5). ) 0.2% by mass relative to the main component.

  Further, as Comparative Examples 4-1 and 4-2 with respect to Examples 4-1 and 4-2, piezoelectric ceramics were manufactured in the same manner as in Examples 4-1 and 4-2, except that tungsten was not added. Of these, Comparative Example 4-1 corresponds to Example 4-1 and Comparative Example 4-2 corresponds to Example 4-2.

  For Examples 4-1 and 4-2 and Comparative Examples 4-1 and 4-2, the electromechanical coupling coefficient kr and the relative dielectric constant of radial vibration were the same as in Examples 1-1 to 1-7. εr and bending strength were measured. The results are shown in Tables 10 and 11.

  As shown in Tables 10 and 11, in all of Examples 4-1 and 4-2 and Comparative Examples 4-1 and 4-2, kr × √εr is 28.2 or more, and bending strength is Although a high value of 80 MPa or more was obtained, Examples 4-1 and 4-2 containing tungsten had a larger value.

  Table 12 compares Example 2-2 shown in Table 3 with Example 4-1 shown in Table 10, and Example 2-3 shown in Table 4 and Example 11 shown in Table 11. A comparison with Example 4-2 is shown. As can be seen from Table 12, in Examples 4-1 and 4-2 to which the second subcomponent is added, kr × √εr is higher than those in Examples 2-2 and 2-3 in which the second subcomponent is not added. Both the bending strength and the bending strength were high.

  That is, when the composition shown in Chemical Formula 10 or Chemical Formula 11 is included as the main component, as in the case where the composition shown in Chemical Formula 9 is included, at least one of the group consisting of tungsten, tantalum, antimony and niobium is included. It has been found that the mechanical strength can be further improved by including one kind.

(Example 5)
The piezoelectric ceramic of Example 3-1, that is, containing the composition shown in Chemical formula 9 as a main component and containing 0.5% by mass of tungsten as a main component in terms of oxide (WO ₃ ) and oxidizing tantalum. A laminated piezoelectric element as shown in FIG. 1 was produced using a piezoelectric ceramic containing 0.2% by mass with respect to the main component converted into a product (Ta ₂ O ₅ ). The thickness of the piezoelectric layer 11 sandwiched between the internal electrodes 12 was 15 μm, the number of laminated layers was 10, and the vertical and horizontal dimensions were 4 mm × 2 mm. A silver / palladium alloy was used for the internal electrode 12, and the firing temperature was 1150 ° C. In addition, after firing the end face of the element, the end face of the element was flat-polished using a grinding wheel, and the appearance was checked for occurrence of chipping and the like. Table 13 shows the defective product ratio in 100 pieces. Further, a driving voltage of 30 V was applied to the obtained piezoelectric element, and the amount of displacement was examined. The results are also shown in Table 13.

  As Comparative Example 5 with respect to Example 5, a piezoelectric element was fabricated in the same manner as in Example 5 except that tungsten and tantalum were not added. In Comparative Example 5 as well as in Example 5, the defective rate in 100 pieces and the displacement amount when a drive voltage of 30 V was applied were examined. The results are also shown in Table 13.

  As shown in Table 13, according to Example 5, the defective product rate could be reduced as compared with Comparative Example 5. Moreover, the displacement amount could be increased. That is, it was confirmed that the piezoelectric characteristics and mechanical strength of the element can be improved by containing a predetermined amount of tungsten.

  In the above-described examples, specific examples have been given. However, similar results can be obtained as long as the composition of the main component and subcomponents is within the range described in the above-described embodiment. Can be obtained.

  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 various modifications can be made. For example, in the above-described embodiment and examples, a case where the main component shown in Chemical Formula 3 or Chemical Formula 4, tungsten, and, if necessary, at least one member selected from the group consisting of tantalum, antimony, and ob is contained. Although described, in addition to these, other components may be included. In that case, the other components may or may not dissolve in the main component.

  In the above-described embodiment, the multilayer piezoelectric element has been described. However, the present invention can be similarly applied to a piezoelectric element having another structure such as a single plate type.

  It can be widely used in the fields of actuators, piezoelectric buzzers, sounding bodies and sensors.

It is sectional drawing showing the example of 1 structure of the piezoelectric element using the piezoelectric ceramic which concerns on one embodiment of this invention. It is a characteristic view showing the relationship between the content of tungsten and kr × √εr. It is a characteristic view showing the relationship between content of tungsten and bending strength.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Laminated body, 11 ... Piezoelectric layer, 12 ... Internal electrode, 21, 22 ... Terminal electrode.

Claims (5)

With respect to the composition represented by Chemical Formula 1, tungsten (W) is contained in the range of 0.05% by mass or more and 3.00% by mass or less in terms of oxide (WO ₃ ). Piezoelectric ceramic.

(In the chemical formula 1, a, x, y and z are 0.96 ≦ a ≦ 1.03, x + y + z = 1, 0.05 ≦ x ≦ 0.40, 0.1 ≦ y ≦ 0.5, 0. (It is a value within the range satisfying 2 ≦ z ≦ 0.6.) With respect to the composition represented by Chemical Formula 2, tungsten (W) is contained in the range of 0.05% by mass or more and 3.00% by mass or less in terms of oxide (WO ₃ ). Piezoelectric ceramic.

(In the chemical formula 2, a, b, x, y, and z are 0.96 ≦ a ≦ 1.03, 0 <b <a, x + y + z = 1, 0.05 ≦ x ≦ 0.40, 0.1 ≦ y ≦ 0.5 and 0.2 ≦ z ≦ 0.6, Me is at least one of the group consisting of strontium (Sr), barium (Ba), and calcium (Ca). Represents a species.) For the composition, at least one selected from the group consisting of tantalum (Ta), antimony (Sb), and niobium (Nb) is used as an oxide (Ta ₂ O ₅ , Sb ₂ O ₃ , Nb ₂ O ₅ ). The piezoelectric ceramic according to claim 1, wherein the piezoelectric ceramic is contained in a range of 0.2% by mass or more and 1.0% by mass or less in total.   A piezoelectric element using the piezoelectric ceramic according to any one of claims 1 to 3.   5. The piezoelectric element according to claim 4, comprising a plurality of piezoelectric layers made of the piezoelectric ceramics and a plurality of internal electrodes inserted between the piezoelectric layers.

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