JP2008169113A - Piezoelectric ceramic composition and piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic composition which is lead-free, has high piezoelectric characteristics and high dielectric characteristics, and is excellent, especially, in at least one of piezoelectric d<SB>31</SB>constant, dielectric constant, dielectric loss, and Curie temperature Tc; to provide a method for producing the same; and to provide a piezoelectric element using the piezoelectric ceramic composition. <P>SOLUTION: The piezoelectric ceramic composition mainly consists of a compound represented by general formula: (Li<SB>x</SB>(K<SB>1-y</SB>Na<SB>y</SB>)<SB>1-x</SB>)<SB>a</SB>(Nb<SB>1-z-w</SB>Ta<SB>z</SB>Sb<SB>w</SB>)<SB>b</SB>O<SB>3</SB>, (wherein x, y, z, w, a, and b are in the ranges: 0<x≤0.2, 0.05≤y≤1, 0<z≤0.4, 0<w≤0.2, a≥0.95 and b≤1.05, respectively). This composition contains, as an additive element, Ag. The content of the additive is 0.001 to 0.15 mol per mol of the compound represented by formula. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a piezoelectric ceramic composition containing no lead in the composition, and a piezoelectric element having the piezoelectric ceramic composition.

Conventionally, as a piezoelectric ceramic composition, lead-containing PZT (PbTiO ₃ —PbZrO ₃ )
Component porcelain has been used. This is because the PZT exhibits a large piezoelectricity and has a high mechanical quality factor, and can easily produce materials having various characteristics required for each application such as a sensor, an actuator, and a filter.
In addition, since the PZT has a high relative dielectric constant, it can also be used as a capacitor or the like.

However, the piezoelectric ceramic composition made of PZT has excellent characteristics, but contains lead as a constituent element, so that harmful lead is eluted from industrial waste of products containing PZT, resulting in environmental pollution. There was a risk of causing. The recent increase in awareness of environmental problems has made it difficult to manufacture products that can cause environmental pollution such as PZT. Therefore, development of a piezoelectric ceramic composition that does not contain lead in the composition is required, and a piezoelectric ceramic composition represented by the general formula (K _1-x Na _x ) NbO ₃ (where 0 <x <1) ( Non-patent document 1) has attracted attention.

However, the piezoelectric ceramic composition represented by the general formula (K _1-x Na _x ) NbO ₃ (where 0 <x <1) has a piezoelectric d ₃₁ constant, an electromechanical coupling coefficient Kp, a piezoelectric g ₃₁ constant, There was a problem that the piezoelectric characteristics such as the mechanical quality factor Qm were low. Therefore, for example, piezoelectric actuators, piezoelectric filters, piezoelectric vibrators, piezoelectric transformers, piezoelectric ultrasonic motors, piezoelectric gyro sensors, knock sensors, yaw rate sensors, airbag sensors, back sonars, corner sonars, which require high piezoelectric d ₃₁ constants, It has been difficult to apply to piezoelectric elements such as piezoelectric buzzers, piezoelectric speakers, and piezoelectric igniters.

In addition, the piezoelectric ceramic composition represented by the above general formula has a problem that it is difficult to apply to a dielectric element such as a capacitor because the dielectric properties such as relative dielectric constant ε _33T / ε ₀ and dielectric loss tan δ are low. there were.
“Journal of the American Ceramic Society”, USA, 1962, Vol. 45, no. 5, p. 209

The present invention has been made in view of such conventional problems, and does not contain lead, and has high piezoelectric characteristics and dielectric characteristics. In particular, the piezoelectric d ₃₁ constant, the relative permittivity, the dielectric loss, and the Curie temperature Tc. It is an object of the present invention to provide a piezoelectric ceramic composition excellent in any one or more, and a piezoelectric element using the piezoelectric ceramic composition.

A first aspect of the present invention is represented by the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3, and x, y, z, w, a and b are compositions of 0 <x ≦ 0.2, 0.05 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2, 0.95 ≦ a, b ≦ 1.05, respectively. A piezoelectric ceramic composition mainly composed of a compound in a range,
The piezoelectric ceramic composition contains Ag as an additive element,
Content of the said additional element exists in the piezoelectric ceramic composition characterized by being 0.001 mol-0.15 mol with respect to 1 mol of compounds represented by the said general formula (Claim 1).

Next, the effects of the present invention will be described.
The piezoelectric ceramic composition of the present invention does not contain lead in its composition.
Therefore, the piezoelectric ceramic composition is safe because harmful lead does not flow out from the waste or the like to the natural world.

The piezoelectric ceramic composition contains a compound represented by the above general formula, and x, y, z, and w in the general formula are in the above ranges, respectively.
Therefore, the piezoelectric ceramic composition has piezoelectric characteristics such as piezoelectric d ₃₁ constant, electromechanical coupling coefficient Kp, piezoelectric g ₃₁ constant, dielectric characteristics such as dielectric constant ε _33T / ε ₀ , dielectric loss tan δ, and Curie temperature Tc. Is excellent.
Note that does not contain the additive element, a composition represented by the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3 Hereinafter, it is referred to as “basic composition” as appropriate.

Furthermore, the piezoelectric ceramic composition contains Ag in the range of the above content as an additive element in addition to the compound having the basic composition represented by the above general formula. Therefore, the piezoelectric ceramic composition of the present invention includes any one or more of the piezoelectric d ₃₁ constant, the piezoelectric g ₃₁ constant, the electromechanical coupling coefficient Kp, the relative dielectric constant ε _33T / ε ₀ , the dielectric loss tan δ, and the Curie temperature Tc. These characteristics are further improved, and even better than the piezoelectric ceramic composition represented by the above general formula and not containing the additive element.
In the piezoelectric ceramic composition, the additive element may be contained by substitution addition to the compound represented by the general formula, and may be externally added to the compound represented by the general formula. May be contained.

Thus, since the piezoelectric ceramic composition of the present invention does not contain lead, it is safe for the environment and has excellent piezoelectric characteristics, and can be used as a high-performance piezoelectric element.
The piezoelectric ceramic composition is excellent in dielectric properties such as dielectric constant and dielectric loss in addition to the piezoelectric properties. Therefore, it can be used as a high-performance dielectric element. That is, the piezoelectric ceramic composition in the first invention is a concept including not only a piezoelectric ceramic composition having piezoelectric characteristics but also a dielectric ceramic composition having dielectric characteristics.

  According to a second aspect of the present invention, there is provided a piezoelectric element comprising the piezoelectric ceramic composition according to the first aspect of the present invention.

The piezoelectric element of the second invention has the piezoelectric ceramic composition of the first invention (Invention 1). Therefore, the piezoelectric element does not contain lead and is safe for the environment.
In addition, the piezoelectric element can use the property of the piezoelectric ceramic composition, such as the piezoelectric d ₃₁ constant, that is excellent in piezoelectric characteristics. Therefore, the piezoelectric element can be used as a highly sensitive piezoelectric sensor element, a piezoelectric vibrator having high electromechanical energy conversion efficiency, an actuator element, and the like.

In the first invention, the compound represented by the general formula {Li _x (K _{1 -y} Na _y ) _{1 -x} } _a (Nb _{1 -zw} Ta _z Sb _w ) _b O ₃ is x, y, The ranges of z and w are 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, and 0 <w ≦ 0.2, respectively.
Here, in the case of x> 0.2, z> 0.4, w> 0.2, z = 0, or w = 0, the piezoelectric characteristics such as the piezoelectric d ₃₁ constant and the dielectric characteristics are reduced, and the desired There is a possibility that a piezoelectric ceramic composition having the above characteristics cannot be obtained.
In the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) compound represented by _b O _3, the range of y is, 0 ≦ y ≦ 0.85 is more preferable, and 0.05 ≦ y ≦ 0.75 is still more preferable. In these cases, the piezoelectric d ₃₁ constant and the electromechanical coupling coefficient Kp of the piezoelectric ceramic composition can be further improved. Still more preferably, 0.05 ≦ y <0.75 is satisfied, 0.35 ≦ y ≦ 0.65 is further preferable, and 0.35 ≦ y <0.65 is more preferable. Most preferably, 0.42 ≦ y ≦ 0.60.

As described above, the piezoelectric ceramic composition contains a compound having a perovskite structure (ABO ₃ ) as a main component. In the present invention, the elemental configuration of the A site in the perovskite structure (ABO ₃ ) corresponds to K, Na or K, Na, and Li, and the elemental configuration of the B site corresponds to Nb, Ta, and Sb. In the composition formula of the perovskite structure, when the stoichiometric ratio is 1: 1 for the atoms constituting the A site and the B site, a complete perovskite structure is obtained. In particular, K, Na, Li, and Sb are volatilized by several percent, specifically about 3% in the firing step, etc., or all constituent elements are several percent in the mixed pulverization or granulation step, specifically, May vary by about 3%. That is, variation from the stoichiometric composition may occur due to variations in the manufacturing method.

  As a response to such composition fluctuations in the manufacturing process, by intentionally changing the composition ratio, the composition ratio of the piezoelectric ceramic composition after firing is ± several%, more specifically ± 3-5. % Can be varied. This is also the case with, for example, conventional zirconate titanate (PZT), and the mixing ratio is adjusted in consideration of lead evaporation during firing and zirconia balls from the grinding media. be able to.

In the piezoelectric ceramic composition of the present invention, even if the composition ratio is intentionally changed as described above, electrical characteristics such as piezoelectric characteristics do not change greatly.
Therefore, in the present invention, the compound represented by the above general formula {Li _x (K _{1 -y} Na _y ) _{1 -x} } _a (Nb _{1 -zw} Ta _z Sb _w ) _b O ₃ has a perovskite structure. When the composition formula ABO ₃ is applied, the composition ratio of the A site atom and the B site atom can be shifted to about ± 5 mol% with respect to 1: 1. In order to reduce the number of lattice defects in the formed crystal and obtain high electrical characteristics, the composition is preferably up to about ± 3%.
That is, the compound represented by the above general formula as the main component of the piezoelectric ceramic composition is [Li _x (K _{1 -y} Na _y ) _1-x ] _a (Nb _{1 -zw} Ta _z Sb _w ) _b O ₃ (0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2, 0.95 ≦ a, b ≦ 1.05) . As described above, in the above formula, the ranges of a and b are preferably 0.97 ≦ a and b ≦ 1.03.

Also that the scope of x in the above general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3 is 0 <x ≦ 0.2 Is preferred.
In this case, since Li is an essential component, the piezoelectric ceramic composition can be fired more easily during its production, further improves the piezoelectric characteristics, and further increases the Curie temperature Tc. Can do. This is because by making Li an essential component within the above range, the firing temperature is lowered, and Li serves as a firing aid and enables firing with fewer voids.

The value of x in the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3 can be the x = 0.
In this case, the general formula is represented by _{(K 1-y Na y)} a (Nb 1-zw Ta z Sb w) b O 3. In this case, when producing the piezoelectric ceramic composition, since the raw material does not include a compound containing the lightest Li, such as LiCO ₃ , the raw materials are mixed and the piezoelectric ceramic is mixed. When producing the composition, variation in characteristics due to segregation of the raw material powder can be reduced. In this case, a high relative dielectric constant and a relatively large piezoelectric g constant can be realized.

  In the first invention, the piezoelectric ceramic composition contains Ag as an additive element, and the content of the additive element is 0.001 mol with respect to 1 mol of the compound represented by the general formula. ~ 0.15 mol.

When the content is less than 0.001 mol or exceeds 0.15 mol, the piezoelectric d ₃₁ constant or the like of the piezoelectric ceramic composition decreases, and a piezoelectric ceramic composition having desired piezoelectric characteristics can be obtained. It may not be possible.
Note that the content of the additive element is the number of moles of Ag.

Also, the additional element of the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3 compound represented by Li, K, Na , Nb, Ta, Sb, in a form in which at least a part of the piezoelectric ceramic composition is substituted with Ag, or in the state of a compound such as Ag or an oxide or a perovskite structure compound containing Ag. The form which exists in a grain boundary can be taken.

In particular, with respect to a metal element that can be +1 or +2 such as Ag, Pd, or Au, at least a part of Li, K, and Na in the compound represented by the above general formula can be substituted. On the other hand, for metal elements that can be +3 to +6 valence, such as Pd, Ru, Rh, Re, Os, Ir, and Pt, at least a part of Nb, Ta, and Sb of the compound represented by the above general formula is substituted. Can also be arranged. And, by taking such a substitutional solid solution form, characteristics such as the piezoelectric d ₃₁ constant can be further improved.

Next, the piezoelectric d ₃₁ constant of the piezoelectric ceramic composition is represented by the above general formula and is preferably larger than the piezoelectric d ₃₁ constant of the piezoelectric ceramic composition not containing the additive element.
If the piezoelectric d ₃₁ constant of a piezoelectric ceramic composition (hereinafter referred to as a basic piezoelectric ceramic composition) that is represented by the above general formula and does not contain the additive element is larger, the effect of the additive element is sufficiently obtained. Piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyro sensor, knock sensor, yaw rate sensor, airbag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric ignition Application to a piezoelectric element such as a vessel becomes easier.

The above-mentioned “greater than the piezoelectric d ₃₁ constant of the piezoelectric ceramic composition represented by the above general formula and not containing the additive element” means that the piezoelectric d ₃₁ constant of the piezoelectric ceramic composition containing the additive element is This means that it is larger than the basic piezoelectric ceramic composition having the basic composition of this piezoelectric ceramic composition and not containing the above-mentioned additive elements, and the electromechanical coupling coefficient Kp and piezoelectric g ₃₁ constant described later. The same applies to the relative permittivity, the dielectric loss, and the Curie temperature Tc.

Next, the electromechanical coupling coefficient Kp of the piezoelectric ceramic composition is represented by the above general formula and is preferably larger than the electromechanical coupling coefficient Kp of the piezoelectric ceramic composition not containing the additive element.
When the electromechanical coupling coefficient Kp of the piezoelectric ceramic composition (basic piezoelectric ceramic composition) which is represented by the above general formula and does not contain the additive element is larger, the effect of the additive element can be sufficiently obtained. Piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyro sensor, knock sensor, yaw rate sensor, airbag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric igniter, etc. Application to the piezoelectric element becomes easier.

Next, the piezoelectric g ₃₁ constant of the piezoelectric ceramic composition is represented by the above general formula and is preferably larger than the piezoelectric g ₃₁ constant of the piezoelectric ceramic composition not containing the additive element.
When the piezoelectric g ₃₁ constant of the piezoelectric ceramic composition (basic piezoelectric ceramic composition) which is represented by the above general formula and does not contain the additive element is larger, the effect of the additive element can be sufficiently obtained. , Piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyro sensor, knock sensor, yaw rate sensor, airbag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric igniter, etc. Application to a piezoelectric element becomes easier.

Next, the relative dielectric constant of the piezoelectric ceramic composition is represented by the above general formula and is preferably larger than the relative dielectric constant of the piezoelectric ceramic composition not containing the additive element.
When the relative dielectric constant of the piezoelectric ceramic composition (basic piezoelectric ceramic composition) which is represented by the above general formula and does not contain the additive element is larger, the effect of the additive element can be sufficiently obtained. Application to a dielectric element such as a capacitor becomes easier.

Next, the dielectric loss of the piezoelectric ceramic composition is represented by the above general formula, and is preferably smaller than the dielectric loss of the piezoelectric ceramic composition not containing the additive element.
When the dielectric loss of the piezoelectric ceramic composition (basic piezoelectric ceramic composition) represented by the above general formula and not containing the additive element is smaller than that of the additive element, the effect of the additive element can be sufficiently obtained. Application to a dielectric element such as the above becomes easier.

Next, the Curie temperature Tc of the piezoelectric ceramic composition is represented by the above general formula and is preferably larger than the Curie temperature Tc of the piezoelectric ceramic composition not containing the additive element.
When the temperature is higher than the Curie temperature of the piezoelectric ceramic composition (basic piezoelectric ceramic composition) which is represented by the above general formula and does not contain the additive element, the effect of the additive element can be sufficiently obtained. Use in a high temperature environment exceeding 100 ° C. such as the vicinity of an automobile engine becomes easier.

Next, the piezoelectric ceramic composition preferably has a piezoelectric d ₃₁ constant of 30 pm / V or more (claim 2).
In this case, taking advantage of the high piezoelectric d ₃₁ constant of 30 pm / V or more, the piezoelectric ceramic composition can be used as a piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyro sensor, knock sensor. , Yaw rate sensor, airbag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric igniter and the like.
When the piezoelectric d ₃₁ constant is less than 30 pm / V, the piezoelectric element may not be used as a piezoelectric element having sufficient characteristics for practical use.

The piezoelectric d ₃₁ constant is more preferably 40 pm / V or more in order to obtain more sensitive piezoelectric sensor characteristics or greater piezoelectric actuator characteristics. More preferably, it is 80 pm / V or more. Even more preferably, it is 100 pm / V or more.

Next, the piezoelectric ceramic composition preferably has an electromechanical coupling coefficient Kp of 0.30 or more.
In this case, utilizing the high electromechanical coupling coefficient Kp of 0.30 or more, the piezoelectric ceramic composition can be converted into a piezoelectric actuator, a piezoelectric filter, a piezoelectric vibrator, a piezoelectric transformer, excellent in conversion efficiency between mechanical energy and electrical energy, It can be used as a piezoelectric ultrasonic motor, piezoelectric gyro sensor, knock sensor, yaw rate sensor, airbag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric igniter and the like.

When the electromechanical coupling coefficient Kp is less than 0.30, the piezoelectric ceramic composition may not be used for a piezoelectric element that requires excellent conversion efficiency between the mechanical energy and the electrical energy. .
Further, in order to obtain a further excellent conversion efficiency between mechanical energy and electrical energy, the electromechanical coupling coefficient Kp is more preferably 0.34 or more. More preferably, 0.4 or more is good. Still more preferably, 0.5 or more is good.

Next, the piezoelectric ceramic composition preferably has a piezoelectric g ₃₁ constant of 7 × 10 ⁻³ Vm / N or more.
In this case, the piezoelectric ceramic composition is used as a piezoelectric transformer, an ultrasonic motor element, a sensor element or the like having an excellent step-up ratio by utilizing the high piezoelectric g ₃₁ constant of 7 × 10 ⁻³ Vm / N or more. be able to.

When the piezoelectric g ₃₁ constant is less than 7 × 10 ⁻³ Vm / N, the piezoelectric ceramic composition may not be used for a piezoelectric element that requires an excellent step-up ratio.
In order to obtain a further excellent boost ratio, the piezoelectric g ₃₁ constant is more preferably 8 × 10 ⁻³ Vm / N or more.

Next, the piezoelectric ceramic composition preferably has a relative dielectric constant of 400 or more.
In this case, the piezoelectric ceramic composition can be used as a dielectric element such as a capacitor having a large electrostatic capacity by utilizing a high relative dielectric constant of 400 or more.

When the relative dielectric constant is less than 400, the capacitance decreases, and the piezoelectric ceramic composition may not be used as a dielectric element such as a capacitor.
The relative dielectric constant is preferably 430 or more. More preferably, 600 or more is good.

Next, the piezoelectric ceramic composition preferably has a dielectric loss of 0.09 or less.
In this case, taking advantage of the low dielectric loss of 0.09 or less, the piezoelectric ceramic composition is used as a dielectric element such as a capacitor, piezoelectric actuator, piezoelectric filter, piezoelectric vibrator, piezoelectric transformer, piezoelectric ultrasonic motor, piezoelectric gyro sensor. , Knock sensor, yaw rate sensor, airbag sensor, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric igniter and the like.

  When the dielectric loss exceeds 0.09, the piezoelectric ceramic composition may not be used as a dielectric element such as the capacitor, a piezoelectric transformer element, an ultrasonic motor element or the like. Therefore, more preferably, the dielectric loss is 0.035 or less. More preferably, 0.025 or less is good.

Next, the piezoelectric ceramic composition preferably has a Curie temperature Tc of 200 ° C. or higher.
In this case, utilizing the high Curie temperature Tc of 200 ° C. or higher, the piezoelectric ceramic composition can be used in a high temperature environment exceeding 100 ° C., for example, in the vicinity of an automobile engine.
When the Curie temperature Tc is less than 200 ° C., the piezoelectric ceramic composition decreases in characteristics such as the piezoelectric d ₃₁ constant and the electromechanical coupling coefficient Kp when the piezoelectric ceramic composition is used in a high temperature place such as in the vicinity of an automobile engine. There is a risk. Therefore, more preferably, the Curie temperature Tc is preferably 250 ° C. or higher.

Next, the piezoelectric ceramic composition preferably has a piezoelectric d ₃₁ constant of 30 pm / V or higher and a Curie temperature Tc of 200 ° C. or higher.
In this case, the piezoelectric ceramic composition can be used as a highly sensitive sensor element, ultrasonic motor element, actuator element, piezoelectric transformer element, piezoelectric vibrator, etc. in a high temperature environment exceeding 100 ° C. .
In order to obtain more sensitive piezoelectric sensor characteristics or greater piezoelectric actuator characteristics, the piezoelectric d ₃₁ constant is preferably 40 pm / V or more. More preferably, it is 80 pm / V or more. Even more preferably, the piezoelectric d ₃₁ constant is 100 pm / V or more.
The Curie temperature Tc is more preferably 250 ° C. or higher.

Next, the piezoelectric ceramic composition preferably has a piezoelectric g ₃₁ constant of 7 × 10 ⁻³ Vm / N or more and a Curie temperature Tc of 200 ° C. or more.
In this case, the piezoelectric ceramic composition can be used as a piezoelectric transformer, an ultrasonic motor element, a sensor element or the like having an excellent step-up ratio in a high temperature environment exceeding 100 ° C.
In order to obtain a further excellent boost ratio, the piezoelectric g ₃₁ constant is more preferably 8 × 10 ⁻³ Vm / N or more.
The Curie temperature Tc is more preferably 250 ° C. or higher.

Next, the piezoelectric ceramic composition preferably has an electromechanical coupling coefficient Kp of 0.3 or more and a Curie temperature Tc of 200 ° C. or more.
In this case, the piezoelectric ceramic composition is excellent in the conversion efficiency of mechanical energy and electrical energy in a high temperature environment exceeding 100 ° C., piezoelectric actuator element, piezoelectric vibrator, sensor element, piezoelectric transformer element, ultrasonic wave It can be used as a motor element or the like.
Further, in order to obtain a further excellent conversion efficiency between mechanical energy and electrical energy, the electromechanical coupling coefficient Kp is more preferably 0.34 or more. More preferably, 0.4 or more is good.
The Curie temperature Tc is more preferably 250 ° C. or higher.

Next, the piezoelectric ceramic composition preferably has a dielectric loss of 0.09 or less and a Curie temperature Tc of 200 ° C. or more.
In this case, the piezoelectric ceramic composition can be used as a dielectric element such as a capacitor, a piezoelectric transformer element, an ultrasonic motor element, a sensor element or the like in a high temperature environment exceeding 100 ° C.
The dielectric loss is more preferably 0.035 or less. More preferably, 0.02 or less is good.
The Curie temperature Tc is more preferably 250 ° C. or higher.

Next, the piezoelectric ceramic composition preferably has a piezoelectric d ₃₁ constant of 30 pm / V or more, an electromechanical coupling coefficient Kp of 0.3 or more, and a Curie temperature Tc of 200 ° C. or more. 7).
In this case, the piezoelectric ceramic composition can be used in a high temperature environment exceeding 100 ° C., and can be excellent in sensitivity and conversion efficiency between mechanical energy and electric energy.
In order to obtain more sensitive piezoelectric sensor characteristics or greater piezoelectric actuator characteristics, the piezoelectric d ₃₁ constant is more preferably 40 pm / V or more. The electromechanical coupling coefficient Kp is more preferably 0.34 or more.

Moreover, the piezoelectric ceramic composition is represented by, for example, the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3, and x, y , Z, w, a, b are 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2, 0.95 ≦ a, b ≦ 1. A compound having a composition range of 05 and an additive containing Ag are mixed and fired so that the amount of Ag element is 0.001 mol to 0.15 mol with respect to 1 mol of the compound represented by the above general formula. can do. At this time, the above Ag may be added to the compound represented by the above general formula, or may be added externally. Further, in the piezoelectric ceramic composition obtained after the firing, as a result of the addition of the additive, any one or more of Li, K, Na, Nb, Ta, and Sb of the compound represented by the above general formula At least a part of the above is contained by substitution of Ag, or is contained in the grain or grain boundary in the piezoelectric ceramic composition as Ag or an oxide or perovskite structure compound containing the same. In the present specification, “containing an additive” has the above-mentioned meaning.
The piezoelectric ceramic composition includes, for example, a compound containing Li, a compound containing Na, a compound containing K, a compound containing Nb, a compound containing Ta, and a compound containing Sb. preparative, expressed in after firing the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3, and x, y, z, w, a , B are in the composition range of 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2, 0.95 ≦ a, b ≦ 1.05, respectively. Mixing at a stoichiometric ratio so that it becomes a compound, or at a stoichiometric ratio considering substitution with Ag contained in the following additive, and further, the additive containing Ag is represented by the above general formula. It is manufactured by mixing and baking the above Ag element amount to 0.001 mol to 0.15 mol with respect to 1 mol of the compound. Rukoto can.
At this time, a compound containing Li, a compound containing Na, a compound containing K, a compound containing Nb, a compound containing Ta, a compound containing Sb, and the above additive , Any of Li, Na, K, Nb, Ta, and Sb in the compound represented by the above general formula when mixed at a stoichiometric ratio considering substitution with Ag contained in the additive At least a part of the one or more kinds can be positively replaced with Ag contained in the additive.
The above-mentioned “mixing at a stoichiometric ratio considering substitution with Ag contained in the additive” means that, for example, when Li of the compound represented by the above general formula is substituted with Ag of the additive, The amount of the compound containing Li is reduced, and the additive is added and mixed by the reduced amount. As a whole, the general formula {Li _x (K _1-y Na _y ) _1-x } _a ( Nb _{1 -zw} Ta _z Sb _w ) _b O ₃ can be realized by mixing at a stoichiometric ratio such that the compound represented by the compound is synthesized. When replacing with other atoms such as K, Na, Nb, Ta, and Sb in the above general formula, the amount of the compound containing these is reduced, and an additive containing the metal element to be replaced is added accordingly. Etc. can be realized. For example, when adding replacing Ag is as _{{Li x (K 1-y} Na y) 1-xu Ag u} a (Nb 1-zw Ta z Sb w) b O 3.
On the other hand, in the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3 compound to become such stoichiometric ratio expressed after firing Then, a compound containing Li, a compound containing Na, a compound containing K, a compound containing Nb, a compound containing Ta, and a compound containing Sb are mixed together. By further mixing the additive and firing it, a piezoelectric ceramic composition containing the additive as the Ag, an oxide containing the additive, or a perovskite structure compound can be positively produced.
Examples of the additive include Ag or a compound containing the same.
As a result of the addition of the additive, Ag contained in the additive is added as an additive element after the calcination by the general formula {Li _x (K _{1 -y} Na _y ) _{1 -x} } _a (Nb _{1 -zw} Ta _z Sb _w ) Li of _b O ₃ compound represented by, by substituting K, Na, Nb, Ta, and at least a portion of Sb, which may be contained in the piezoelectric porcelain composition. Further, the metal element or an oxide containing the metal element or a compound such as a perovskite structure compound may be contained in the grain or grain boundary in the piezoelectric ceramic composition.

Examples of the lithium-containing compound include Li ₂ CO ₃ , Li ₂ O, LiNO ₃ , and LiOH. Examples of the compound containing sodium include Na ₂ CO ₃ , NaHCO ₃ , and NaNO ₃ .

Examples of the compound containing potassium include K ₂ CO ₃ , KNO ₃ , KNbO ₃ , and KTaO ₃ . Examples of the compound containing niobium include Nb ₂ O ₅ , Nb ₂ O ₃ , and NbO ₂ . Examples of the compound containing tantalum include Ta ₂ O ₅ . Examples of the compound containing antimony include Sb ₂ O ₅ , Sb ₂ O ₃ , and Sb ₂ O ₄ .

Next, Li ₂ CO ₃ as the compound containing Li, Na ₂ CO ₃ as the compound containing Na, K ₂ CO ₃ as the compound containing K, and Nb as the compound containing Nb Nb ₂ O ₅ , Ta ₂ O ₅ as the compound containing Ta, Sb ₂ O ₅ or Sb ₂ O ₃ as the compound containing Sb, PdO ₂ , Ag ₂ O as the additive , Au, Au ₂ O, Ru ₂ O, RhO, Re ₂ O ₅ , OsO ₂ , IrO ₂ , and PtO ₂ are preferably used.
In this case, the piezoelectric ceramic composition can be easily produced.

  Next, in the second aspect (invention 8), examples of the piezoelectric element include a piezoelectric actuator, a piezoelectric filter, a piezoelectric vibrator, a piezoelectric transformer, a piezoelectric ultrasonic motor, a piezoelectric gyro sensor, a knock sensor, a yaw rate sensor, There are airbag sensors, back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric igniter and so on.

  Next, examples of the dielectric element include a capacitor and a multilayer capacitor.

(Example 1)
Next, the piezoelectric ceramic composition concerning the Example of this invention is demonstrated.
In this example, the piezoelectric ceramic composition is manufactured and its characteristics are measured.
The piezoelectric ceramic composition of this example is represented by the general formula {Li _x (K _1−y Na _y ) _1−x } (Nb _1−zw Ta _z Sb _w ) O ₃ and x, y, z, w Are piezoelectric ceramic compositions mainly composed of compounds in the composition ranges of 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, and 0 <w ≦ 0.2. The piezoelectric ceramic composition contains at least one metal element selected from Pd, Ag, Au, Ru, Rh, Re, Os, Ir, and Pt as an additive element. And the sum total of content of the said additional element is 0.001 mol-0.15 mol with respect to 1 mol of compounds represented by the said general formula.

The method for producing a piezoelectric ceramic composition of this example includes a compound containing Li, a compound containing Na, a compound containing K, a compound containing Nb, a compound containing Ta, and Sb. a compound which is represented after firing by a general formula _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sbw) O 3, and x, y, z, w, respectively 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2. An additive containing any one or more metal elements selected from Ag, Au, Ru, Rh, Re, Os, Ir, and Pt is mixed and fired.

Hereafter, it demonstrates in detail about the manufacturing method of the piezoelectric ceramic composition of this example.
First, as a raw material of the basic composition of a piezoelectric ceramic composition, high purity Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Sb ₂ O ₅ having a purity of 99% or more. , And PdO ₂ , Ag ₂ O, Au, RuO ₂ , Re ₂ O ₇ , IrO ₂ , and PtO ₂ as the additives were prepared.

Among these raw materials, Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Sb ₂ O ₅ are represented by the above general formula {Li _x (K _1-y Na _{y ) 1-x} (Nb 1} -zw Ta z Sb w) at _{O 3, x, y, z} , w , respectively x = 0.04, y = 0.5, z = 0.1, w = 0. The stoichiometric ratio is 04, that is, the stoichiometric ratio is such that the above general formula is {Li _0.04 (K _0.5 Na _0.5 ) _0.96 } (Nb _0.86 Ta _0.1 Sb _0.04 ) O ₃ , PdO ₂ , Ag ₂ O, Au, RuO ₂ , Re ₂ O ₇ , IrO ₂ , or PtO ₂ as the above additives were blended to obtain seven types of blends.

The compounding amount of the additive relative to the blended compound is expected to be obtained by _{{Li 0.04 (K 0.5 Na 0.5} ) 0.96} (Nb 0.86 Ta 0.1 Sb 0.04) O 3 1mol at the stoichiometric ratio PdO ₂ , Ag ₂ O, Au, RuO ₂ , Re ₂ O ₇ , IrO _2, or PtO ₂ as the additive are 0.01 mol, 0.005 mol, 0.01 mol, 0.01 mol, 0.005 mol, respectively. , 0.01 mol, 0.01 mol. That is, 0.01 mol of the metal element contained in each additive was mixed.
And each said compound was mixed in acetone with the ball mill for 24 hours, respectively, and the mixture was produced.

Next, each mixture was calcined at 750 ° C. for 5 hours, and then each calcined mixture was ground in a ball mill for 24 hours. Subsequently, polyvinyl butyral was added as a binder and granulated.
Each granulated powder is pressure-molded into a disk shape having a diameter of 13 mm and a thickness of 2 mm at a pressure of ² ton / cm ² , and the resulting molded body is fired at a temperature of 1000 to 1300 ° C. for 1 hour. Was made. In addition, the specific calcination temperature at this time selected the temperature from which the calcination body of the maximum density is obtained by baking for 1 hour among the temperature range of said 1000 degreeC-1300 degreeC. At this time, all the fired bodies were densified to a relative density of 98% or more.

Next, both surfaces of each fired body were subjected to parallel polishing and circular polishing, and then gold electrodes were provided on both surfaces of the disk sample by sputtering. And the direct-current voltage of 1-5 kV / mm was applied between electrodes for 10 minutes in 100 degreeC silicone oil, and it polarized in the thickness direction, and was set as the piezoelectric ceramic composition.
In this way, seven types of piezoelectric ceramic compositions (samples E1 to E7) were produced. Table 1 shows the mixing ratio of raw materials and additives in each sample. Each sample in Table 1 was prepared by a method of externally adding each metal element in the additive.

In addition, as a method different from the manufacturing method of this example, a compound represented by the above {Li _0.04 (K _0.5 Na _0.5 ) _0.96 } (Nb _0.86 Ta _0.1 Sb _0.04 ) O ₃ was prepared by firing, and this was pulverized. The piezoelectric ceramic composition similar to the samples E1 to E7 can be produced by mixing with the additive and then performing calcination, granulation, molding, and firing in the same manner as the production method of this example.

In addition, in the samples E1 to E7 of this example, PdO ₂ , Ag ₂ O, Au, RuO ₂ , Re ₂ O ₇ , IrO ₂ or PtO ₂ as the above-mentioned additives are partly intact or basic. A compound such as a perovskite structure compound is formed with any one or more of the constituent elements Li, Na, K, Nb, Ta, and Sb, and in the form, in the grain boundary or grain boundary of each piezoelectric ceramic composition And a part thereof is at least one of Li, K, Na, Nb, Ta, and Sb of the compound represented by {Li _0.04 (K _0.5 Na _0.5 ) _0.96 } (Nb _0.86 Ta _0.1 Sb _0.04 ) O _3. It is considered that the Pd, Ag, Au, Ru, Re, Ir, or Pt atoms in each additive are included in the parts in a substituted state. In particular, a metal element that can be +1 or +2 such as Ag, Pd, or Au is easily replaced with at least part of Li, K, and Na in the above compound. In addition, metal elements that can be +3 to +6 valence such as Pd, Ru, Rh, Re, Os, Ir, and Pt are easily replaced with at least part of Nb, Ta, and Sb of the above compound.

Next, in this example, in order to clarify the excellent characteristics of the piezoelectric ceramic composition, comparative products (sample C1 and sample C2) were produced as follows.
First, high purity Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , and Sb ₂ O ₅ having a purity of 99% or more were prepared as comparative materials.

Among these raw materials, K ₂ CO ₃ , Na ₂ CO ₃ , and Nb ₂ O ₅ are converted into the above general formula {Li _x (K _{1 -y} Na _y ) _{1 -x} } (Nb _{1 -zw} Ta _z Sb _w ) O. ₃ , the stoichiometric ratio such that x = z = w = 0 and y = 0.5, that is, the stoichiometric ratio such that the general formula is (K _0.5 Na _0.5 ) NbO ₃ And mixed in acetone for 24 hours by a ball mill to obtain a mixture.
This mixture was calcined, granulated, molded, fired and polarized in the same manner as the above samples E1 to E7, and a piezoelectric ceramic composition (sample C1) as a comparative product was produced.
Sample C1 is a piezoelectric ceramic composition containing (K _0.5 Na _0.5 ) NbO ₃ .

Next, the sample C2 is produced as follows.
First, the raw materials Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , and Sb ₂ O ₅ prepared above are subjected to the above general formula {Li _x ( K _1−y Na _y ) _1−x } (Nb _1−zw Ta _z Sb _w ) O ₃ , x = 0.04, y = 0.5, z = 0.1, and w = 0.04 Stoichiometric ratio, that is, a stoichiometric ratio such that the above general formula becomes a compound represented by {Li _0.04 (K _0.5 Na _0.5 ) _0.96 } (Nb _0.86 Ta _0.1 Sb _0.04 ) O ₃ , The mixture was mixed in acetone by a ball mill for 24 hours to obtain a mixture.

This mixture was calcined, granulated, molded, fired and polarized in the same manner as in the above samples E1 to E7 to produce a piezoelectric ceramic composition (sample C2) as a comparative product.
Sample C2 contains the compound {Li _0.04 (K _0.5 Na _0.5 ) _0.96 } (Nb _0.86 Ta _0.1 Sb _0.04 ) O ₃ as the main component, as in the above samples E1 to E7, but contains the above-mentioned additional elements. It is a piezoelectric ceramic composition that is not used.
Table 1 shows the composition ratio of the sample C1 and the sample C2.

Next, for the samples E1 to E7, the sample C1, and the sample C2, the piezoelectric d ₃₁ constant, the electromechanical coupling coefficient Kp, the piezoelectric g ₃₁ constant, the relative dielectric constant ε _33T / ε ₀ , the dielectric loss tan δ, and the Curie temperature Tc are set. Each was measured.

The piezoelectric d ₃₁ constant, the piezoelectric g ₃₁ constant, and the electromechanical coupling coefficient Kp were measured by a resonance-antiresonance method using an impedance analyzer (Precision Impedance Analyzer 4294A manufactured by Agilent).
The dielectric loss tan δ and relative dielectric constant ε _33T / ε ₀ were measured at a measurement frequency of 1 kHz using the same impedance analyzer as described above.
The Curie temperature Tc was defined as the Curie temperature Tc that is the temperature at which the relative dielectric constant ε _33T / ε ₀ is the highest.
The results are shown in Table 2.

As can be seen from Table 2, the above-mentioned conventional piezoelectric ceramic composition is the same as the above-described conventional piezoelectric ceramic composition in _{terms of} its piezoelectric d ₃₁ constant, electromechanical coupling coefficient Kp, relative dielectric constant ε _33T / ε ₀ , and dielectric loss tan δ. The sample C1 had characteristics superior to those of the sample C1.
Further, the samples E1 to E7 have a piezoelectric d ₃₁ constant, an electromechanical coupling coefficient Kp, a piezoelectric g ₃₁ constant, a relative dielectric constant ε _33T / ε ₀ , a dielectric loss tan δ, and a Curie temperature Tc, even when compared with the sample C2. In this case, it had the same or better characteristics.
In particular, for the piezoelectric d ₃₁ constant, the total number of electrical solutions Kp, and the relative dielectric constant ε _33T / ε ₀ , most of the samples E1 to E7 are superior to the samples C1 and C2, and the dielectric loss tan δ is All of the samples E1 to E7 were superior to the samples C1 and C2.

Here, focusing on the piezoelectric d ₃₁ constant, as known from Table 2, the piezoelectric d ₃₁ constant of the sample E2 has the highest value of 122.4pm / V.

When a charge detection type circuit or a current detection type circuit is used, the piezoelectric d ₃₁ constant is generally
It is proportional to the output voltage of a piezoelectric sensor such as an acceleration sensor, a weight sensor, an impact sensor, or a knock sensor. From this point of view, a piezoelectric ceramic composition having a higher piezoelectric d ₃₁ constant can produce a sensor element having a larger charge sensor output. And it can be said that it is preferable to have a piezoelectric d ₃₁ constant of at least 30 pm / V or more in order to produce a sensor element having characteristics equal to or higher than that of the sample C1 as a comparative product. Furthermore, in order to increase the signal-to-noise ratio (SN ratio) and the output voltage to produce a highly sensitive sensor element, the piezoelectric d ₃₁ constant is preferably 80 pm / V or more. More preferably, it is 100 pm / V or more.

When used as an actuator, the piezoelectric d ₃₁ constant is generally proportional to the generated strain or displacement of the piezoelectric actuator. From this point of view, a piezoelectric ceramic composition having a higher piezoelectric d ₃₁ constant can produce an actuator element having a larger generated strain or displacement. It can be said that it is preferable to have a piezoelectric d ₃₁ constant of at least 30 pm / V or more in order to produce an actuator element having characteristics equal to or higher than those of a comparative product. More preferably, it is 40 pm / V or more. In order to manufacture an actuator with a larger displacement, the piezoelectric d ₃₁ constant is preferably 80 pm / V or more. More preferably, it is 100 pm / V or more.

  Further, paying attention to the electromechanical coupling coefficient Kp, as is known from Table 2, the electromechanical coupling coefficient Kp of the sample E2 showed the highest value of 0.531.

  In general, the electromechanical coupling coefficient Kp is proportional to the electromechanical energy conversion efficiency of a piezoelectric transformer element, an ultrasonic motor element, an actuator element, or an ultrasonic transducer. From this point of view, a piezoelectric transformer element, an ultrasonic motor element, an actuator element, or an ultrasonic transducer having a higher electromechanical energy conversion efficiency can be produced with a piezoelectric ceramic composition having a higher electromechanical coupling coefficient Kp. In order to manufacture a piezoelectric transformer element, an ultrasonic motor element, an actuator element, or an ultrasonic vibrator having characteristics equivalent to or better than those of the comparative sample C1, an electromechanical coupling coefficient Kp of at least 0.3 or more is required. It can be said that it is preferable. More preferably 0.34 or more. More preferably, 0.4 or more is good. Furthermore, 0.5 or more is more preferable.

Further, when paying attention to the Curie temperature Tc, the Curie temperatures Tc of the samples E1 to E7 all take a high value of 200 ° C. or higher. Therefore, the piezoelectric ceramic composition (samples E1 to E7) of this example is a sensor component or actuator component for high temperature such as a knock sensor that can be used stably for a long time even in a high temperature part such as the vicinity of an automobile engine. It can be used as an ultrasonic motor component.
In addition, the Curie temperature Tc is preferably 200 ° C. or higher in order to use the sensor component, the actuator component, the ultrasonic motor component and the like for the high temperature stably for a long time. More preferably, the temperature is 250 ° C. or higher.

Further, paying attention to the piezoelectric g ₃₁ constant, as known from Table 2, the piezoelectric g ₃₁ constant of Sample E7 showed the highest value of 8.94 × 10 ^-3 Vm / N.

The piezoelectric g ₃₁ constant is proportional to the output voltage of a piezoelectric sensor, a piezoelectric transformer element, an ultrasonic motor element, or the like, like the piezoelectric d ₃₁ constant. Therefore, a piezoelectric ceramic composition having a higher piezoelectric g ₃₁ constant can produce a sensor having a larger voltage sensor output. And it can be said that it is preferable to have a piezoelectric g ₃₁ constant of at least 7 × 10 ⁻³ Vm / N or more in order to produce a sensor having characteristics equal to or higher than those of the comparative product. More preferably, 8 × 10 ⁻³ Vm / N or more is preferable.

Moreover, focusing on the dielectric constant ε _33T / ε _0, the relative dielectric constant ε _33T / ε ₀ of the sample E1~E7 takes the very high value of 1300 or more.

The relative dielectric constant ε _33T / ε ₀ is generally proportional to the capacitance of a capacitor such as a multilayer capacitor component. From this point of view, a piezoelectric ceramic composition having a higher relative dielectric constant can produce a capacitor having a larger capacitance. In order to produce a capacitor, it can be said that it is preferable to have a relative dielectric constant of at least 400 or more. More preferably, 430 or more is good. More preferably, 600 or more are good.

  When attention is paid to the dielectric loss tan δ, the dielectric loss tan δ of the samples E1 to E7 has a very low value of 0.023 or less.

  The dielectric loss is proportional to the thermal energy lost when an AC voltage is applied to a component such as a capacitor component, a piezoelectric ultrasonic motor, a piezoelectric actuator, or a piezoelectric transformer. From this point of view, the piezoelectric ceramic composition having a smaller dielectric loss can produce a capacitor with less energy loss and a piezoelectric ultrasonic motor, piezoelectric actuator, and piezoelectric transformer with less heat generation. And in order to produce the said components with little energy loss, it is preferable to have a dielectric loss of 0.09 or less. More preferably, 0.035 or less is good. More preferably, it is 0.025 or less.

  As described above, the piezoelectric ceramic composition (samples E1 to E7) of this example does not contain lead in the composition and has excellent piezoelectric characteristics and dielectric characteristics as described above. Therefore, it can be used for high-performance piezoelectric elements and dielectric elements that are safe to the environment.

(Example 2)
In this example, in order to determine the critical range of the content of the additive, the general formula {Li _x (K _1−y Na _y ) _1−x } (Nb _1−zw Ta _z Sb _w ) O ₃ This is an example in which Ag ₂ O as the additive is contained in the compound represented by changing the amount thereof.

First, as a raw material of the piezoelectric ceramic composition, high-purity Li ₂ CO ₃ having a purity of 99% or more, Na ₂ CO ₃ , K ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Sb ₂ O ₅ , and the above Ag ₂ O as an additive was prepared.
Among these raw materials, Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Sb
_{In the} above general formula {Li _x (K _{1 -y} Na _y ) _{1 -x} } (Nb _{1 -zw} Ta _z Sb _w ) O ₃ after firing ₂ O ₅ , x, y, z and w are each x = 0. .04, y = 0.5, z = 0.1, w = 0.06 and blended in a stoichiometric ratio, and Ag ₂ O as an additive is added in various amounts. 16 kinds of blends were obtained by blending.

As for the compounding amount of Ag ₂ O, the compound {Li _0.04 (K _0.5 Na _0.5 ) _0.96 } (Nb _0.84 Ta _0.1 Sb _0.06 ) O ₃ 1 mol expected to be obtained after calcining with the above stoichiometric ratio. In contrast, 0.0005 mol to 0.25 mol of Ag ₂ O as the additive was blended. That is, Ag was added in an amount of 0.001 to 0.5 mol.
And each said compound was mixed in acetone with the ball mill for 24 hours, respectively, and the mixture was produced.

  Next, in the same manner as Sample E1 to Sample E7 in Example 1, each mixture was calcined, granulated, molded, fired, polarized, and 16 types of piezoelectric ceramic compositions were prepared. X1 to sample X16. Table 3 shows the mixing ratio of raw materials and additives in each sample.

In the samples X1 to X16 obtained here, Ag ₂ O as the additive is partly as it is or is composed of Li, Na, K, Nb, Ta, and Sb which are constituent elements of the basic composition. A compound such as a perovskite structure compound is formed with any one or more, and is included in the grain or grain boundary of each piezoelectric ceramic composition in that form, and a part thereof is the above {Li _0.04 (K _0.5 Na _0.5 ) _0.96 } (Nb _0.84 Ta _0.1 Sb _0.06 ) O ₃ is considered to be contained in a state in which Ag in Ag ₂ O is substituted for at least part of Li, K, and Na in the compound represented by O ₃ . In particular, when the addition amount of Ag ₂ O exceeds 0.1 mol with respect to 1 mol of the compound represented by {Li _0.04 (K _0.5 Na _0.5 ) _0.96 } (Nb _0.84 Ta _0.1 Sb _0.06 ) O ₃ , that is, When the content of the metal element Ag exceeds 0.2 mol, Ag ₂ O as the additive precipitates in the form of a compound containing Ag or / and Ag ₂ O or Ag at the grain boundary of the piezoelectric ceramic composition. It becomes easy.
In this example, for the purpose of clarifying the effect when Ag is added, K and Na in the compound represented by {Li _0.04 (K _0.5 Na _0.5 ) _0.96 } (Nb _0.84 Ta _0.1 Sb _0.06 ) O ₃ are used. On the other hand, each sample was prepared by an addition method in which Ag was substituted and added. That is, for example, in the sample X8, the composition was {Li _0.04 (K _0.5 Na _0.5 ) _0.86 Ag _1.0 } (Nb _0.84 Ta _0.1 Sb _0.06 ) O ₃ .

Further, in this embodiment, to clarify the effects of Ag ₂ O formulation, were prepared samples containing no Ag ₂ O serving as the additive.
Specifically, high-purity Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , and Sb ₂ O ₅ having a purity of 99% or more are prepared. The raw materials were mixed at a stoichiometric ratio such that after firing, a compound represented by Li _0.04 (K _0.5 Na _0.5 ) _0.96 } (Nb _0.84 Ta _0.1 Sb _0.06 ) O ₃ was used. Mixing for a time gave a mixture. Subsequently, this mixture was calcined, granulated, molded, fired and polarized in the same manner as Sample E1 to Sample E7 of Example 1 to obtain a piezoelectric ceramic composition (Sample Y1). Table 3 shows the composition ratio of the sample Y1.

Next, for the samples X1 to X16 and the sample Y1, the piezoelectric d ₃₁ constant, the electromechanical coupling coefficient Kp, the piezoelectric g ₃₁ constant, the relative dielectric constant ε _33T / ε ₀ , the dielectric loss tan δ, and the Curie temperature Tc Each was measured in the same manner as in 1. The results are shown in Table 4. In Table 4, the results of the sample C1 produced in Example 1 are also shown for comparison.

As known from Table 4, all of the samples X1 to X9 had higher piezoelectric d ₃₁ constants and relative dielectric constants ε _33T / ε ₀ than those of the samples Y1 and C1. Further, the dielectric loss tan δ was also smaller and superior to those of the sample Y1 and the sample C1.
That is, as known from Tables 3 and 4, the additive amount of Ag ₂ O as an additive is 0.001 mol to 0 in terms of the content of additive element Ag with respect to 1 mol of the compound represented by the above general formula. When it is .15 mol, it can be seen that the piezoelectric ceramic composition is particularly excellent in piezoelectric d ₃₁ constant, relative dielectric constant ε _33T / ε ₀ , and dielectric loss tan δ.
Moreover, as known by Table 4, the sample X1~X9, the electromechanical coupling factor Kp,圧電g ₃₁ constant, and also in the Curie temperature Tc, exhibited excellent characteristics comparable with sample Y1.

On the other hand, when the amount of addition of Ag ₂ O as an additive is more than 0.15 mol in terms of the additive element Ag, samples X10 to X16, including the piezoelectric d ₃₁ constant, the electromechanical coupling coefficient The values of Kp, piezoelectric g ₃₁ constant, relative dielectric constant ε _33T / ε ₀ , dielectric loss tan δ, and Curie temperature Tc were lower than those of sample Y1.

  Thus, according to this example, it can be seen that when the content of the additive element is 0.001 mol to 0.15 mol, the characteristics of the piezoelectric ceramic composition are remarkably improved. Although not shown in the table, the same results as in this example were obtained for other metal elements.

  Further, in this example, although not specifically shown, it has been confirmed that the improvement of characteristics by the additive element may be substitutional addition or external addition. In addition, the main component of the piezoelectric ceramic composition used in this example is only one composition of the selectable composition, and it has been confirmed that the characteristics are improved in the other compositions as well.

Claims (8)

It is represented by the general formula _{{Li x (K 1-y} Na y) 1-x} a (Nb 1-zw Ta z Sb w) b O 3, and x, y, z, w, a, b are respectively 0 <X ≦ 0.2, 0.05 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2, 0.95 ≦ a, b ≦ 1.05 A piezoelectric ceramic composition comprising:
The piezoelectric ceramic composition contains Ag as an additive element,
The piezoelectric ceramic composition, wherein the content of the additive element is 0.001 mol to 0.15 mol with respect to 1 mol of the compound represented by the general formula. The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition has a piezoelectric d ₃₁ constant of 30 pm / V or more. 3. The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition has a piezoelectric g ₃₁ constant of 7 × 10 ⁻³ Vm / N or more.   The piezoelectric ceramic composition according to any one of claims 1 to 3, wherein the piezoelectric ceramic composition has a Curie temperature Tc of 200 ° C or higher. 2. The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition has a piezoelectric d ₃₁ constant of 30 pm / V or more and a Curie temperature Tc of 200 ° C. or more. 2. The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition has a piezoelectric g ₃₁ constant of 7 × 10 ⁻³ Vm / N and a Curie temperature Tc of 200 ° C. or more. 2. The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric d ₃₁ constant is 30 pm / V or more, the electromechanical coupling coefficient Kp is 0.3 or more, and the Curie temperature Tc is 200 ° C. or more. Piezoelectric ceramic composition.   A piezoelectric element comprising the piezoelectric ceramic composition according to claim 1.