JP2004300012A - Piezoelectric ceramic composition, its production method, piezoelectric element, and dielectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead-free piezoelectric ceramic composition which can be fired under ordinary pressure, and has one or more properties more excellent than those of the conventional one among the properties characteristic of a piezoelectric ceramic composition such as a piezoelectric d<SB>31</SB>constant. <P>SOLUTION: The piezoelectric ceramic composition is expressed by general formula of äLi<SB>x</SB>(K<SB>1-y</SB>Na<SB>y</SB>)<SB>1-x</SB>}(Nb<SB>1-z-w</SB>Ta<SB>z</SB>Sb<SB>w</SB>)O<SB>3</SB>, and also, x, y, z, w lie in the compositional ranges of 0≤x≤0.2, 0≤y≤1, 0<z≤0.4, and 0<w≤0.2, respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a piezoelectric ceramic composition containing no lead in the composition, a method for producing the same, and a piezoelectric element and a dielectric element using the piezoelectric ceramic composition as a material.

Conventionally, a PZT (PbTiO ₃ -PbZrO ₃ ) component-based ceramic containing lead has been used as a piezoelectric ceramic composition. The above-mentioned PZT exhibits large piezoelectricity and has a high mechanical quality factor with excellent long-term stability, and can easily produce materials with various characteristics required for various applications such as sensors, actuators, and filters. Because you can.
Further, since the PZT has a high relative permittivity, it can be used as a capacitor or the like.

However, while the piezoelectric ceramic composition comprising PZT has excellent characteristics, it contains lead as a constituent element, so that harmful lead is eluted from industrial waste of products containing PZT, resulting in environmental pollution. Could be caused. And, increasing awareness of environmental issues in recent years has made it difficult to manufacture products that can cause environmental pollution, such as PZT. Therefore, the development of a piezoelectric ceramic composition containing no lead in its composition has been required, and a piezoelectric ceramic composition (non-leading) represented by the general formula (K _1-x Na _x ) NbO ₃ (where 0 <x <1) (Patent Document 1)).

However, the piezoelectric ceramic composition represented by the above general formula (K _1-x Na _x ) NbO ₃ (where 0 <x <1) is difficult to be fired, so that hot press firing must be performed. For this reason, there has been a problem that the manufacturing cost is increased.
Furthermore, the piezoelectric ceramic composition represented by the above general formula, the piezoelectric d ₃₁ constant, the characteristics such as electromechanical coupling factor Kp and the Curie temperature Tc has a problem that low. Therefore, for example, high piezoelectric constant d ₃₁ constant, a piezoelectric actuator that requires an electromechanical coupling factor Kp, piezoelectric filters, piezoelectric transducers, piezoelectric transformers, piezoelectric ultrasonic motor, a piezoelectric gyro sensors, knock sensors, yaw rate sensors, airbag sensors , Back sonar, corner sonar, piezoelectric buzzer, piezoelectric speaker, piezoelectric igniter, etc., it was difficult to apply to piezoelectric elements. Further, since the Curie temperature Tc is low, there is a problem that the piezoelectric characteristics in a high temperature environment deteriorate.
"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, does not contain lead, it can be fired at atmospheric pressure, at least one of the piezoelectric ceramic composition of the specific properties such as piezoelectric d ₃₁ constant It is an object of the present invention to provide a piezoelectric ceramic composition and a method of manufacturing the same, and a piezoelectric element and a dielectric element using the piezoelectric ceramic composition.

The first invention of the general formula represented by _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3, and x, y, z, w, respectively 0 <X ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2 The piezoelectric ceramic composition is characterized in that it is in the composition range (claim 1).

The piezoelectric ceramic composition of the first invention, as represented by the general formula _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3, Does not contain lead in the composition.
Therefore, the piezoelectric ceramic composition is safe because harmful lead does not flow out to nature from waste of the piezoelectric ceramic composition and the like.

In the piezoelectric ceramic composition, x, y, z, and w in the above general formula are each in the above range. Therefore, the piezoelectric ceramic composition is excellent in at least one of 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. It will be.

  In the piezoelectric ceramic composition, the range of z in the above general formula is 0 <z ≦ 0.4, and the range of w is 0 <w ≦ 0.2, and contains Ta and Sb as essential components. ing. Therefore, the piezoelectric ceramic composition is easily densified during firing, and can be sufficiently densified by firing under normal pressure. This is because by using Ta and Sb as essential components within the above range, the firing temperature is lowered, and Ta and Sb serve as a firing aid, enabling firing with few pores. . Therefore, the piezoelectric ceramic composition can be easily and inexpensively manufactured without the need for hot press baking as in the related art. Further, the stability of the dielectric loss tan δ of the piezoelectric ceramic composition can be improved.

As described above, the piezoelectric ceramic composition is safe for the environment, can be fired at normal pressure, and can be used as a material for a high-performance piezoelectric element or dielectric element.
The piezoelectric ceramic composition according to the first aspect of the invention is a concept including not only a ceramic composition having piezoelectric characteristics but also a dielectric ceramic composition having dielectric characteristics.

The second invention of the general formula represented by _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3, and x, y, z, w, respectively 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2 A powder comprising a piezoelectric ceramic composition having a composition range of 0.2 is molded and fired. (Claim 17).

A compact formed using the powder of the piezoelectric ceramic composition can be fired under normal pressure. Therefore, sintering can be performed easily and at low cost. The piezoelectric ceramic composition obtained after the calcination does not contain lead, and has excellent piezoelectric ceramic composition-specific characteristics such as a piezoelectric d ₃₁ constant. Therefore, it can be used as a material for a high-performance piezoelectric element or dielectric element.

  A third invention relates to a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, and a compound containing tantalum. A method for producing a piezoelectric ceramic composition, characterized in that a piezoelectric ceramic composition according to any one of claims 1 to 16 is obtained by mixing and baking a compound containing antimony. Claim 18).

In the third invention, as described above, a compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, and antimony Mix and bake with the compound contained.
Thereby, the piezoelectric ceramic composition of the first invention can be easily obtained.

Further, during the firing, the piezoelectric ceramic composition can be fired under normal pressure. The piezoelectric ceramic composition obtained after the calcination does not contain lead, and has excellent piezoelectric ceramic composition-specific characteristics such as a piezoelectric d ₃₁ constant. Therefore, it can be used as a material for a high-performance piezoelectric element or dielectric element.

  A fourth invention resides in a piezoelectric element having a piezoelectric body made of the piezoelectric ceramic composition of the first invention (claim 20).

The piezoelectric element according to the fourth aspect has a piezoelectric body made of the piezoelectric ceramic composition according to the first aspect (claim 1). Therefore, the piezoelectric element does not contain lead and is environmentally safe.
Further, the piezoelectric element includes the above piezoelectric ceramic composition, can be used as it is the property of the piezoelectric ceramic composition of the specific properties such as piezoelectric d ₃₁ constant is excellent. Therefore, the piezoelectric element can be used as an excellent piezoelectric element such as a piezoelectric sensor element having high sensitivity, a piezoelectric vibrator having high electromechanical energy conversion efficiency, and an actuator element.

  A fifth invention resides in a dielectric element having a dielectric made of the piezoelectric ceramic composition of the first invention (claim 21).

  The dielectric element according to the fifth aspect has a dielectric made of the piezoelectric ceramic composition according to the first aspect (claim 1). Therefore, the dielectric element does not contain lead and is environmentally safe. In addition, the dielectric element can utilize the property of the piezoelectric ceramic composition, which is excellent in any one or more of characteristics such as relative dielectric constant, dielectric loss, and long-term stability of dielectric loss, as it is. Therefore, it can be used as an excellent dielectric element such as a capacitor having a large capacitance.

In the present invention, the piezoelectric ceramic composition 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 in the composition ranges of 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, and 0 <w ≦ 0.2, respectively.
Here, when x> 0.2, z> 0.4, w> 0.2, z = 0, or w = 0, the characteristics peculiar to the piezoelectric ceramic composition such as the piezoelectric d ₃₁ constant are not obtained. There is a possibility that the piezoelectric ceramic composition having desired characteristics may not be obtained.

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 element configuration of the A site in the perovskite structure (ABO ₃ ) corresponds to K, Na or K, Na, and Li, and the element configuration of the B site corresponds to Nb, Ta, and Sb. In the composition formula of the perovskite structure, when the stoichiometric ratio of the atoms constituting the A site and the atoms constituting the B site is 1: 1, a complete perovskite structure is obtained. In particular, K, Na, Li, and Sb are volatilized by several%, specifically, about 3% in a firing step or the like, and all constituent elements are mixed by several% in a mixing pulverization or granulation step, and specifically, It may fluctuate by about 3%. That is, the stoichiometric composition may fluctuate due to variations in the manufacturing method.

  In order to cope with such compositional fluctuations in the manufacturing process, the compositional ratio of the piezoelectric ceramic composition after firing is increased by ± several%, more specifically ± 3 to 5 by intentionally changing the composition ratio. %. This is the same for, for example, the conventional zirconate titanate (PZT), and the mixing ratio is adjusted in consideration of the evaporation of lead during firing and the incorporation of zirconia from zirconia balls as grinding media. be able to.

In the piezoelectric ceramic composition of the present invention, electrical characteristics such as piezoelectric characteristics do not significantly change even if the composition ratio is intentionally changed as described above.
Accordingly, in the present invention, the general formula _{Li x (K 1-y Na} y) 1-x} (Nb 1-zw Ta z Sb w) compound represented by O _3, this a perovskite structure formula When applied to ABO ₃ , the composition ratio of A-site atoms and B-site atoms can be shifted to about ± 5 mol% with respect to 1: 1. In order to reduce lattice defects in the formed crystal and obtain high electrical characteristics, the composition is preferably up to about ± 3%.
That is, the general compound of formula as the main component of the piezoelectric ceramic _{composition, [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) Including. Further, as described above, in the above equation, the range of a and b is preferably 0.97 ≦ a, b ≦ 1.03.

Similarly, the general formula _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3, it is preferable that z + w ≦ 0.37.
In this case, it is possible to further improve the unique properties to the piezoelectric ceramic composition such as the piezoelectric d ₃₁ constant.

  The piezoelectric ceramic composition has piezoelectricity and dielectric properties, and can be used as both a piezoelectric substance and a dielectric substance. Specifically, 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, piezoelectric buzzers, piezoelectric speakers, It can be used as a piezoelectric igniter or the like.

In the first aspect (claim 1), the general formula _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) range of x O ₃ is 0 < It is preferable that x ≦ 0.2 (claim 2).
In this case, since Li is an essential component, the piezoelectric ceramic composition can easily produce a fired body at the time of firing, further improve the piezoelectric characteristics, and further raise the Curie temperature. be able to. This is because by making Li an essential component within the above range, the firing temperature is reduced, and Li plays a role of a firing aid, enabling firing with few voids.

Then, the value of the general formula _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3 of x may be a x = 0 (claim 3).
In this case, the general formula is represented by _{(K 1-y Na y)} (Nb 1-zw Ta z Sb w) O 3. In this case, when preparing the piezoelectric ceramic composition, since the raw material does not include a compound containing lightest Li, such as Li ₂ CO ₃ , the raw materials are mixed and mixed. When producing a piezoelectric ceramic composition, it is possible to reduce variation in characteristics due to segregation of raw material powder. In this case, a high relative dielectric constant and a relatively large piezoelectric g constant can be realized.

Similarly, the general formula _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) range of the y in O ₃ is preferably 0 <y ≦ 1. (Claim 4)
In this case, the piezoelectric g ₃₁ constant of the piezoelectric ceramic composition can be further improved. The range of y is more preferably 0 ≦ y ≦ 0.85, and even more preferably 0.05 ≦ y ≦ 0.75. In these cases, the piezoelectric d ₃₁ constant and electromechanical coupling factor Kp of the piezoelectric ceramic composition can be further improved. Still more preferably, 0.05 ≦ y <0.75, more preferably 0.35 ≦ y ≦ 0.65, and even more preferably 0.35 ≦ y <0.65. Most preferably, 0.42 ≦ y ≦ 0.60 is good.

In the general formula, the value of y can be set to y = 0 (claim 5).
In this case, the general formula is expressed by _{{(Li x K) 1-} x} (Nb 1-zw Ta z Sb w) O 3. In this case, the piezoelectric ceramic composition does not contain Na, so that the dielectric loss of the piezoelectric ceramic composition and the long-term stability of the dielectric loss can be improved.

Next, the piezoelectric ceramic composition is preferably a piezoelectric d ₃₁ constant is 30 Pm/V more (Claim 6).
In this case, by utilizing the high piezoelectric d ₃₁ constant called the 30 Pm/V above, the piezoelectric ceramic composition having high sensitivity piezoelectric actuator, a piezoelectric filter, a piezoelectric vibrator, a piezoelectric transformer, piezoelectric ultrasonic motor, a piezoelectric gyroscope , Knock sensors, yaw rate sensors, airbag sensors, back sonars, corner sonars, piezoelectric buzzers, piezoelectric speakers, piezoelectric igniters, and the like.

When the piezoelectric d ₃₁ constant is less than 30 Pm/V, it may not be available to the piezoelectric element which requires excellent sensitivity the piezoelectric ceramic composition.
In order to obtain an excellent piezoelectric sensor characteristic or a larger piezoelectric actuator characteristics of more sensitive, and more preferably the piezoelectric d ₃₁ constant is 40 Pm/V more. More preferably, it is 80 pm / V or more. More preferably, the piezoelectric d ₃₁ constant is preferably 100 pm / V or more.

Next, the piezoelectric ceramic composition preferably has a piezoelectric g ₃₁ constant of 7 × 10 ⁻³ Vm / N or more (claim 7).
In this case, the piezoelectric ceramic composition is used as a piezoelectric transformer, an ultrasonic motor element, a sensor element, and 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.

If 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 requiring an excellent boost ratio.
Further, in order to obtain a more excellent step-up ratio, the piezoelectric g ₃₁ constant is more preferably 10 × 10 ⁻³ Vm / N or more.

Next, the piezoelectric ceramic composition preferably has an electromechanical coupling coefficient Kp of 0.3 or more.
In this case, the piezoelectric ceramic composition, a piezoelectric actuator, a piezoelectric filter, a piezoelectric vibrator, and a piezoelectric transformer having excellent conversion efficiency between mechanical energy and electric energy are utilized by utilizing the high electromechanical coupling coefficient Kp of 0.3 or more. 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.

If the electromechanical coupling coefficient Kp is less than 0.3, the piezoelectric ceramic composition may not be able to be used for a piezoelectric element requiring excellent conversion efficiency between the mechanical energy and the electric energy. .
In order to obtain a more excellent conversion efficiency between mechanical energy and electric energy, the electromechanical coupling coefficient Kp is more preferably 0.34 or more. More preferably, it is 0.4 or more. More preferably, the electromechanical coupling coefficient Kp is 0.5 or more.

Next, the piezoelectric ceramic composition preferably has a dielectric loss of 0.09 or less (claim 9).
In this case, taking advantage of a low dielectric loss of 0.09 or less, the piezoelectric ceramic composition is used to convert the piezoelectric ceramic composition into a dielectric element such as a capacitor, a piezoelectric actuator, a piezoelectric filter, a piezoelectric vibrator, a piezoelectric transformer, a piezoelectric ultrasonic motor, and a piezoelectric gyro sensor. , Knock sensors, yaw rate sensors, airbag sensors, back sonars, corner sonars, piezoelectric buzzers, piezoelectric speakers, and piezoelectric igniters.

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

Next, the piezoelectric ceramic composition preferably has a relative dielectric constant of 400 or more (claim 10).
In this case, the piezoelectric ceramic composition can be used as a dielectric element such as a capacitor having a large capacitance by utilizing the high relative dielectric constant of 400 or more.
If the relative dielectric constant is less than 400, the capacitance may decrease, and the piezoelectric ceramic composition may not be used as a dielectric element such as a capacitor.
Further, the relative dielectric constant is more preferably 430 or more. More preferably, it is 600 or more.

Next, the piezoelectric ceramic composition preferably has a Curie temperature Tc of 200 ° C. or higher (Claim 11).
In this case, by utilizing the high Curie temperature Tc of 200 ° C. or more, the piezoelectric ceramic composition can be used in a high temperature environment exceeding 100 ° C., for example, near an engine of an automobile.
When the Curie temperature Tc is lower than 200 ° C., when the piezoelectric ceramic composition is used in a high temperature place, for example, near the engine of an automobile, its properties such as a piezoelectric d ₃₁ constant and an electromechanical coupling coefficient Kp are deteriorated. There is a possibility that.
Further, 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 and a Curie temperature Tc of 200 ° C. or more (claim 12).
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, and the like under a high temperature environment exceeding 100 ° C. .
In order to obtain an excellent piezoelectric sensor characteristic or a larger piezoelectric actuator characteristics of more sensitive, it is preferable that the piezoelectric d ₃₁ constant is 40 Pm/V more. More preferably, it is 80 pm / V or more. More preferably, the piezoelectric d ₃₁ constant is preferably 100 pm / V or more.
Further, 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 mVm / N or more and a Curie temperature Tc of 200 ° C. or more (claim 13).
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 under a high temperature environment exceeding 100 ° C.
Further, in order to obtain a more excellent step-up ratio, the piezoelectric g ₃₁ constant is more preferably 10 × 10 ⁻³ Vm / N or more.
Further, the Curie temperature Tc is more preferably 250 ° C. or higher.

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

Next, it is preferable that the piezoelectric ceramic composition 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, and the like under a high temperature environment exceeding 100 ° C.
More preferably, the dielectric loss is 0.035 or less.
Further, 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. 16).
In this case, the piezoelectric ceramic composition can be used in a high-temperature environment exceeding 100 ° C., and can have excellent sensitivity and conversion efficiency between mechanical energy and electric energy.
Further, more excellent piezoelectric sensor characteristics of sensitivity, or to obtain a larger piezoelectric actuator characteristics, it is more preferable that the piezoelectric d ₃₁ constant is 40 Pm/V more. Further, the electromechanical coupling coefficient Kp is more preferably 0.34 or more.

In the third invention (claim 18), the compound containing lithium includes, for example, Li ₂ CO ₃ , Li ₂ O, LiNO ₃ , and LiOH. The sodium-containing compounds 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 , KTaO _{3 and the} like. The compound comprising the above-mentioned niobium, there is for example _{Nb 2 O 5, Nb 2 O} 3, NbO 2 , and the like. Examples of the tantalum-containing compound include Ta ₂ O ₅ . The compound comprising the above antimony, there are for example _{Sb 2 O 5, Sb 2 O} 3, Sb 2 O 4 or the like.

Next, the compound containing lithium is Li ₂ CO ₃ , the compound containing sodium is Na ₂ CO ₃ , the compound containing potassium is K ₂ CO ₃ , and the compound containing niobium is Is Nb ₂ O ₅ , the compound containing tantalum is Ta ₂ O ₅ , and the compound containing antimony is Sb ₂ O ₅ or Sb ₂ O _3. Preferred (claim 19).
In this case, the piezoelectric ceramic composition can be easily produced.

  Next, in the fourth invention (claim 20), as the piezoelectric element, for example, 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 sonars, corner sonars, piezoelectric buzzers, piezoelectric speakers, and piezoelectric igniters.

  Next, in the fifth invention (claim 21), examples of the dielectric element include a capacitor and a multilayer capacitor.

(Example)
Next, a piezoelectric ceramic composition according to an example of the present invention will be described.
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 in the composition ranges of 0 ≦ x ≦ 0.2, 0 ≦ y ≦ 1, 0 <z ≦ 0.4, and 0 <w ≦ 0.2, respectively.

Hereinafter, a method for producing the piezoelectric ceramic composition of the present example will be described.
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 raw materials of the piezoelectric ceramic composition. .
In these materials the general formula _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3, x, y, z, w is 0 ≦ x ≦ 0. They were mixed at a stoichiometric ratio such that 2,0 ≦ y ≦ 1, 0 <z ≦ 0.4, and 0 <w ≦ 0.2.

Here, as shown in Tables 1 to 6, which will be described later, x is x = 0, 0.01, 0.02, 0.03, 0.04, 0.06, 0.08, 0.10, 0.15 and 0.20 were set.
As y, y = 0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.42, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.58, 0.6, 0.70, 0. 75, 0.8, and 1.0.
Further, z is such that z = 0.002, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.30. I made it.
In addition, w is set to be 0.02, 0.04, 0.05, 0.06, 0.07, 0.1, and 0.2.
Then, the raw materials mixed so as to have the respective stoichiometric compositions were mixed in acetone by a ball mill for 24 hours to prepare a mixture.

Next, this mixture was calcined at 750 ° C. for 5 hours, and the calcined mixture was ground by a ball mill for 24 hours. Subsequently, polyvinyl butyral was added as a binder and granulated.
The granulated powder was pressed at a pressure of ² ton / cm ² into a disk having a diameter of 18 mm and a thickness of 1 mm, and the formed body was fired at 1000 to 1300 ° C. for 1 hour to produce a fired body. . The firing temperature at this time was selected to be a temperature at which the maximum density was obtained between 1000 ° C and 1300 ° C. Further, all of the fired bodies were densified to a relative density of 98% or more.

Next, both surfaces of each fired body after firing were polished in parallel and circularly polished, and then gold electrodes were provided on both surfaces of the disk sample by sputtering. Then, a DC voltage of 1 to 5 kV / mm was applied between the electrodes in a silicone oil at 100 ° C. for 10 minutes to polarize in the thickness direction to obtain a piezoelectric ceramic composition.
Thus, piezoelectric ceramic compositions (samples 1 to 182) having 182 stoichiometric compositions were prepared. Tables 1 to 6 show the chemical composition ratio of each sample.

In this example, comparative products 1 to 5 were prepared as follows in order to clarify the excellent characteristics of the piezoelectric ceramic composition.
First, high-purity K ₂ CO ₃ , Na ₂ CO _3, and Nb ₂ O ₅ having a purity of 99% or more were prepared as raw materials of the comparative product 1.
These raw materials were mixed at a stoichiometric ratio such that the general formula (K _0.5 Na _0.5 ) NbO ₃ was obtained, and mixed in a ball mill for 24 hours in acetone to obtain a mixture.
This mixture was calcined, granulated, molded, fired, and polarized in the same manner as in Samples 1 to 182, to obtain Comparative Product 1.

In addition, high purity Li ₂ CO ₃ , K ₂ CO ₃ , Na 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, and comparative products 2, 3, 4, and as 5, in the _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) composition formula, respectively x = 0.22, y = 0.50, z = 0.45, w = 0.22, and x = 0.22, y = 0.50, z = 0.10, w = 0.02, and x = 0.02, y = 0.50, z = Samples satisfying 0.45, w = 0.02, x = 0.02, y = 0.50, z = 0.10, and w = 0.22 were produced by the same method.
Table 6 shows the chemical composition ratios of Comparative Products 1 to 5.

Next, the piezoelectric d ₃₁ constant, the piezoelectric g ₃₁ constant, the electromechanical coupling coefficient Kp, the Curie temperature Tc, the relative permittivity _{33 33T} / ε ₀ , and the dielectric loss tan δ were measured for the samples 1 to 182 and the comparative products 1 to 5. did.

Here the piezoelectric d ₃₁ constant, the piezoelectric g ₃₁ constant and electromechanical coupling factor Kp, the resonance using an impedance analyzer - was measured by anti-resonance method.
The dielectric loss and relative permittivity were measured at a measurement frequency of 1 kHz using an impedance analyzer.
The Curie temperature Tc is the temperature at which the relative dielectric constant is the highest, which is the Curie temperature Tc.
Tables 7 to 12 show the results.

  The samples 2, 4, 5, 8, 15, 16, 31 to 34, 40, 41, 48, 49, 71, 72, 74, 75, 79, 80, 81, 88 to 90, 103, 104, Long-term stability of dielectric loss was measured for 107, 110, 112, 115, 118, 119, 123 to 129, 133, 134, 136 to 140, 143, 145, 151, 152 and Comparative product 1.

As a method for measuring the long-term stability of the dielectric loss, first, the dielectric loss tan δ of the polarized sample and the comparative product 1 is measured at a measurement frequency of 1 kHz using an impedance analyzer in the same manner as described above. The initial value was tan δ. Furthermore, the dielectric loss tanδ after 50 days, 100 days, or 200 days from the polarization was measured and compared with the value of the initial tanδ to evaluate the long-term stability of the dielectric loss.
Tables 13 and 14 show the results.

As can be seen from Tables 6 to 12, Samples 1 to 13, 15 to 20, 25 to 28, 31 to 37, 39 to 44, 46 to 52, 55 to 59, 67, 71 to 85, 87 to 92, 97 ９９99, 103〜154, 156〜159, 162２〜182 showed higher piezoelectric d ₃₁ constants than Comparative Example 1.
Here, the sample 155～ sample 180 in Table 12, in the general formula _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3, x, z and w Are fixed and the value of y is changed to show various piezoelectric characteristics and dielectric characteristics. In Sample 155～ sample 180 to reveal a change in the piezoelectric d ₃₁ constant when changing the value of y, for values of the piezoelectric d ₃₁ constant when the y = 0.5 (Sample 158), the sample The ratio of each piezoelectric d ₃₁ constant value of 155 to 180 is shown as d ₃₁ ratio.

  In addition, as is known from Tables 6 to 12, samples 1 to 5, 7 to 12, 15 to 20, 25 to 28, 31 to 36, 39 to 44, 47 to 51, 56 to 58, 71 to 78, 80 to 84, 88 to 90, 103 to 154, 157 to 159, and 164 to 179 showed higher electromechanical coupling coefficients Kp than Comparative Product 1.

Further, Samples 1 to 159 and Samples 162 to 182 exhibited a high relative dielectric constant of 430 or more, and were superior to Comparative Product 1.
Samples 1 to 5, 7 to 12, 16 to 20, 31 to 34, 40 to 42, 47 to 50, 58, 65, 71 to 77, 80 to 82, 103 to 111, 115, 118 to 130, 134 , 136-139, 158, 160-161, 165-166, 168-169, 171, 173, 175 and samples 179-180 exhibited high piezoelectric g ₃₁ constants of 7.0 × 10 ⁻³ or more.

Samples 1 to 22, 24 to 54, 58 to 62, 70 to 86, 89 to 94, 101 to 180 exhibited high Curie temperatures Tc of 200 ° C. or higher.
Further, Samples 1 to 22, 24 to 26, 31 to 35, 39 to 74, 76 to 94, and 96 to 182 exhibited a low dielectric loss tan δ of 0.09 or less.

  Further, as known from Tables 13 and 14, the dielectric loss of each sample did not increase significantly after 50 days, 100 days, or 200 days, and was excellent in stability. On the other hand, the dielectric loss of the comparative product 1 increased by three times the initial tan δ after 50 days and more than 6 times after 100 days. After 200 days, the initial tan δ increased to nearly seven times, and there was a problem in stability.

Here, focusing on the piezoelectric d ₃₁ constant, as known from Table 1 to Table 12, x = 0.04, y = 0.54, z = 0.1 and w = 0.06, (Sample 175) At that time, the piezoelectric d ₃₁ constant showed the highest value of 132.4 pm / V.

Moreover, as known from Table 6 and Table 12, in the general formula _{Li x (K 1-y Na} y) 1-x} (Nb 1-zw Ta z Sb w) O 3, by changing the value of y It can be seen that when the piezoelectric ceramic composition is manufactured, the piezoelectric d ₃₁ constant changes significantly.
Accordingly, for easy understanding of the relationship of y values and the piezoelectric d ₃₁ constant in the above general formula, shows the results of the piezoelectric d ₃₁ constant in the table 12 in FIG. 1. 1, the horizontal axis represents the value of y in the above general formula, the vertical axis shows the piezoelectric d ₃₁ constant.

As can be understood from FIG. 1, in order to realize a high piezoelectric d ₃₁ constant called 40 pm / V or more, the general formula _{Li x (K 1-y Na} y) 1-x} (Nb 1-zw Ta z Sb w It can be seen that it is preferable that the value of y in O _{3 be} 0.05 ≦ y <0.75. Further, when the range of the value of y is 0.35 ≦ y ≦ 0.65, a higher piezoelectric d ₃₁ constant of 80 pm / V or more can be realized. Further, when the range of the value of y is 0.42 ≦ y ≦ 0.60, a higher piezoelectric d ₃₁ constant exceeding 100 pm / V can be realized. However, this preferable range of the value of y changes when the values of x, z, and w in the above general formula change.

In the case of using the charge detection type circuit or a current detection type circuit is generally the piezoelectric d ₃₁ constant, the acceleration sensor, weighting sensor, is proportional to the output voltage of the piezoelectric type sensor, such as an impact sensor and the knock sensor. Viewed from that point, it is possible to piezoelectric d ₃₁ constant make a big sensor element of the charge sensor output higher piezoelectric ceramic composition. Then, in making a sensor element having a comparative product 1 equivalent or more properties, it would be preferable to have a piezoelectric d ₃₁ constant over at least 30 pm/V. To generate a highly sensitive sensor element is further enhanced signal-to-noise ratio (SN ratio) and the output voltage, the piezoelectric d ₃₁ constant good not less than 80 pm/V. More preferably, it is 100 pm / V or more.

When used as actuators, generally the piezoelectric d ₃₁ constant is proportional to the generated distortion or displacement of the piezoelectric actuator. Viewed from that point, it is possible to piezoelectric d ₃₁ constant make a big actuator element of higher piezoelectric ceramic composition generates distortion or displacement. And making the actuator element having a comparative product 1 equivalent or more properties, it would be preferable to have a piezoelectric d ₃₁ constant over at least 30 pm/V. More preferably, it is 40 pm / V or more. To further prepare the large actuator displacement amount, the piezoelectric d ₃₁ constant good not less than 80 pm/V. More preferably, it is 100 pm / V or more.

  Focusing on the electromechanical coupling coefficient Kp, as can be seen from Tables 1 to 12, when x = 0, y = 0.5, z = 0.002, and w = 0.04 (sample 31), The electromechanical coupling coefficient Kp showed the highest value of 0.623.

  Generally, 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 vibrator. From that point, a piezoelectric ceramic composition having a higher electromechanical coupling coefficient Kp can produce a piezoelectric transformer element, an ultrasonic motor element, an actuator element, or an ultrasonic transducer having higher electromechanical energy conversion efficiency. In order to produce a piezoelectric transformer element, an ultrasonic motor element, an actuator element, or an ultrasonic vibrator having characteristics equal to or higher than that of the comparative product 1, the electromechanical coupling coefficient Kp must be at least 0.3 or more. It is preferable. More preferably, it is 0.34 or more. More preferably, it is 0.4 or more. Further, it is more preferably 0.5 or more.

In addition, focusing on the Curie temperature Tc, the Curie temperature Tc of the piezoelectric ceramic compositions of the samples 1 to 22, 24 to 54, 58 to 62, 70 to 86, 89 to 94, 101 to 180 is as high as 200 ° C. or more. Has taken. Therefore, the piezoelectric ceramic composition of the present example in the above composition range can be used for a high temperature sensor component such as a knock sensor that can be stably used for a long time even in a high temperature portion such as the vicinity of an engine of an automobile, an actuator component, It can be used as an ultrasonic motor part or the like.
In order to use the sensor component, actuator component, ultrasonic motor component, etc. for high temperature more stably for a long time, the Curie temperature Tc is preferably 200 ° C. or more. More preferably, the temperature is 250 ° C. or higher.

Moreover, focusing on the piezoelectric g ₃₁ constant, as known from Table 1 to Table 12, x = 0, y = 0.5, z = 0.002, and w = 0.04 when (Sample 31), piezoelectric The g ₃₁ constant showed the highest value of 16.2 × 10 ⁻³ Vm / N.

The piezoelectric g ₃₁ constant is proportional to the output voltage of the piezoelectric sensor, the piezoelectric transformer element, the ultrasonic motor element and the like, like the piezoelectric d ₃₁ constant. Therefore, it is possible to make a large sensor voltage sensor output as the piezoelectric g ₃₁ constant high piezoelectric ceramic composition. In order to manufacture a sensor having characteristics equal to or higher than that of the comparative product 1, 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. More preferably, it is 10 × 10 ⁻³ Vm / N or more.

Moreover, focusing on the dielectric constant ε _33T / ε _0, the relative dielectric constant ε _33T / ε ₀ of the sample 1 to 159 and the sample 162 to 182 takes the high value of 430 or more.

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

  Focusing on the dielectric loss tan δ, the dielectric loss tan δ of the samples 1 to 22, 24 to 26, 31 to 35, 39 to 74, 76 to 94, and 96 to 182 has a low value of 0.09 or less. .

  The above-mentioned dielectric loss is proportional to the heat energy lost by applying an AC voltage to components such as a capacitor such as a capacitor component, a piezoelectric ultrasonic motor, a piezoelectric actuator, and a piezoelectric transformer. From this point of view, a piezoelectric ceramic composition having a smaller dielectric loss can produce a capacitor having a smaller energy loss and a piezoelectric ultrasonic motor, a piezoelectric actuator, and a piezoelectric transformer having a smaller heat generation. In order to produce the above-described component having a small energy loss, the component preferably has a dielectric loss of 0.09 or less. More preferably, it is 0.035 or less.

Focusing on the long-term stability of the dielectric loss, as shown in Tables 13 and 14, z = 0.002, that is, a sample having a very small Ta content, has a large dielectric loss when left in the air for a long time. Disadvantage. On the other hand, in the sample where z> 0.002 and w ≠ 0, the change in the dielectric loss is small even when the sample is left in the atmosphere for a long time, and the value of the dielectric loss is kept at a small value of 0.09 or less. Thus, in the general formula the general formula shown in the present invention _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) O 3, 0 ≦ x ≦ 0.2, The dielectric loss tan δ of the piezoelectric ceramic composition of this example in the composition ranges of 0 ≦ y ≦ 0.1, 0 <z ≦ 0.4, and 0 <w ≦ 0.2 has long-term stability.

As shown in Table 12, Comparative Examples 2, 3, and 5, which are not included in the composition range of the piezoelectric ceramic composition of the present invention, have piezoelectric d ₃₁ constants of 0.5, 9.81, and 13.31 pm / respectively. V was found to be a low value. In addition, Comparative Example 4 has a piezoelectric d ₃₁ constant of 42.62 pm / V, but has a low Curie temperature of 117 ° C. and requires a Curie temperature of 200 ° C. or higher, and thus cannot be used as an automobile part.

According to the embodiment, explanation diagram showing the relationship of the general formula _{{Li x (K 1-y} Na y) 1-x} (Nb 1-zw Ta z Sb w) value of y in the O ₃ and the piezoelectric d ₃₁ constant .

Claims (21)

It 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 respectively 0 ≦ x ≦ 0.2 , 0 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2.   2. The piezoelectric ceramic composition according to claim 1, wherein the range of x in the general formula is 0 <x ≦ 0.2.   2. The piezoelectric ceramic composition according to claim 1, wherein the value of x in the general formula is x = 0.   The piezoelectric ceramic composition according to any one of claims 1 to 3, wherein the range of y in the general formula is 0 <y ≦ 1.   The piezoelectric ceramic composition according to any one of claims 1 to 3, wherein the value of y in the general formula is y = 0. In any one of claims 1 to 5, the piezoelectric ceramic composition, the piezoelectric porcelain composition, wherein the piezoelectric d ₃₁ constant is 30 Pm/V more. The piezoelectric ceramic composition according to any one of claims 1 to 6, 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 7, wherein the piezoelectric ceramic composition has an electromechanical coupling coefficient Kp of 0.3 or more.   The piezoelectric ceramic composition according to any one of claims 1 to 8, wherein the piezoelectric ceramic composition has a dielectric loss of 0.09 or less.   The piezoelectric ceramic composition according to any one of claims 1 to 9, wherein the piezoelectric ceramic composition has a relative dielectric constant of 400 or more.   The piezoelectric ceramic composition according to any one of claims 1 to 10, wherein the piezoelectric ceramic composition has a Curie temperature Tc of 200 ° C or higher. In any one of claims 1 to 5, the piezoelectric ceramic composition, the piezoelectric porcelain composition, wherein the piezoelectric d ₃₁ constant is at 30 Pm/V or more and the Curie temperature Tc is 200 ° C. or higher. 6. The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition has a piezoelectric g ₃₁ constant of 7 × 10 ⁻³ mVm / N or more and a Curie temperature Tc of 200 ° C. or more. Piezoelectric ceramic composition.   The piezoelectric ceramic composition according to any one of claims 1 to 5, wherein the piezoelectric ceramic composition has an electromechanical coupling coefficient Kp of 0.3 or more and a Curie temperature Tc of 200 ° C or more. .   The piezoelectric ceramic composition according to any one of claims 1 to 5, wherein the piezoelectric ceramic composition has a dielectric loss of 0.09 or less and a Curie temperature Tc of 200C or more. In any one of claims 1 to 5, the piezoelectric ceramic composition in the piezoelectric d ₃₁ constant 30 Pm/V above, and in electromechanical coupling coefficient Kp is 0.3 or more, and the Curie temperature Tc is 200 ° C. A piezoelectric ceramic composition characterized by the above. It 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 respectively 0 ≦ x ≦ 0.2 , 0 ≦ y ≦ 1, 0 <z ≦ 0.4, 0 <w ≦ 0.2 A powder comprising the piezoelectric ceramic composition in the composition ranges of: Production method.   A compound containing lithium, a compound containing sodium, a compound containing potassium, a compound containing niobium, a compound containing tantalum, and a compound containing antimony A method for producing a piezoelectric ceramic composition, comprising obtaining the piezoelectric ceramic composition according to any one of claims 1 to 16 by mixing and firing the compound. 19. The method according to claim 18, wherein the compound containing lithium is Li ₂ CO ₃ , the compound containing sodium is Na ₂ CO ₃ , the compound containing potassium is K ₂ CO ₃ , and niobium is used. Is Nb ₂ O ₅ , the compound containing tantalum is Ta ₂ O ₅ , and the compound containing antimony is Sb ₂ O ₅ or Sb ₂ O _3. A method for producing a piezoelectric ceramic composition, which is characterized in that:   A piezoelectric element comprising a piezoelectric body made of the piezoelectric ceramic composition according to claim 1. A dielectric element comprising a dielectric comprising the piezoelectric ceramic composition according to any one of claims 1 to 16.

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