KR102020605B1 - Lead-free piezoelectric ceramic ternary compositions with high strains - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a semi-structured lead-free piezoelectric ceramic composition having a high strain rate, wherein SrTiO ₃ has a perovskite crystal structure and has (Bi, Na) TiO ₃ as a matrix, the addition (Bi, Na) TiO ₃ - on the SrTiO ₃ based solid solution, a part of the (Bi, Na) TiO ₃ is characterized in that the substituted CaTiO _3.
Also Fe lobe has a Sky agent crystal structure, as a main component Bi, Na, Ti, containing O (Bi, Na) A by a matrix of TiO _3, the addition of _{SrTiO 3 (Bi, Na) TiO} 3 - SrTiO 3 based on a portion of the solid solution (Bi, Na) TiO ₃ is characterized in that substituted by BiAlO _3.

Description

Lead-free piezoelectric ceramic composition with high strain rate {LEAD-FREE PIEZOELECTRIC CERAMIC TERNARY COMPOSITIONS WITH HIGH STRAINS}

The present invention relates to a ternary lead-free piezoelectric ceramic composition having a high strain rate, and more particularly, to a lead-free piezoelectric ceramic composition having no lead and excellent electric field induction deformation characteristics.

Piezoelectric ceramics are piezoelectric materials made of ceramics that can exchange mechanical vibrations and alternating electric fields. They generate voltage when pressure is applied and mechanical deformation when an external electric field is applied. It is a device that happens. In other words, it is a material capable of converting mechanical vibration energy into electrical energy and electrical energy into mechanical vibration energy.

Piezoelectric ceramics play an important role in the field of precise microcontrol, such as in the electronics industry, especially in the mechatronics sector. Pb (Zr, Ti) O ₃ (PZT) flexible piezoceramic materials have excellent piezoelectric properties, low cost, and are well-known in the manufacturing process technology, and have a wide range of applications with various sensors and actuators. Actuator refers to a device that changes physical state by changing electrical signals, such as switches or lamps.

On the other hand, PZT-based flexible piezoceramic materials currently have a problem that 50% or more of lead is contained in weight ratio. Lead is widely known as a heavy metal that causes environmental problems and is harmful to humans. Recently, the use of lead-containing materials is regulated around the world, but PZT piezoelectric materials are excluded from the regulation because no lead-free materials have been developed.

Lead-free piezoelectric ceramics based on (Bi, Na) TiO ₃ (hereinafter BNT) are harmless to humans and have a perovskite structure of ABO ₃ perovskite structure, similar to PZT-based lead-based piezoelectric ceramics. Rhombohedral) It has a crystal structure, Ti ^{4 +} is located on B-site, and Bi ^{3 +} and Na ^{1 +} elements are mixed in half on A-site, resulting in a bivalent element.

These materials are causing the electrical polarization in the Z-axis direction of the electrical field externally applied (Electric Field) Ti ^{+ 4} ions in the B-site by the crystal structure, resulting in variations in results of the mechanical polarization. In addition, BNT-based materials have the same shape as the relaxed ferroelectric because there are two elements in the A-site. Due to the low dielectric constant values, most dielectrics are insignificant for practical applications, and crystallographically without crystallographic centers in the unit lattice shows piezoelectric properties only when they are single crystals, but polarized by external electric fields In the case of ferroelectric material, which can change the direction of, the piezoelectric effect can be realized through a post-treatment process called polarization even in the form of polycrystals.

Here, the piezoelectric characteristics are shown to be directly proportional to the polarization value according to the external electric field. In the case of the electric field induced strain, the piezoelectric property only expands regardless of the direction of the electric field. The expansion or contraction is possible and the degree of deformation is large enough for practical applications. Therefore, most industrial piezoelectric applications are using polarized ferroelectric materials.

Recently, research is being conducted to develop a lead-free piezoceramic material having excellent piezoelectric properties.

An object of the present invention is to provide a ternary lead-free piezoelectric ceramic composition having a high electric field induction strain.

In order to solve the above technical problem, the present invention has a perovskite crystal structure, and SrTiO ₃ is added based on (Bi, Na) TiO ₃ including Bi, Na, Ti, and O as a main component. Bi, Na) TiO ₃ - part of the SrTiO ₃ based on the solid solution (Bi, Na) TiO ₃ is characterized in that the substituted CaTiO _3.

In addition, the lead-free piezoelectric ceramic is _{(1-xy) Bi 1/} 2 Na 1/2 TiO 3 - xSrTiO 3 - yCaTiO 3 ( wherein x is 0.22≤x≤0.30, wherein y is 0 <y≤0.04 Im) such as It is characterized by having a composition.

In addition, the lead-free piezoelectric ceramics are characterized by having a normalized strain (S _max / E _max ) of 290 to 610 pm / V in an electric field of 4 kV / mm.

Also Fe lobe has a Sky agent crystal structure, as a main component Bi, Na, Ti, containing O (Bi, Na) A by a matrix of TiO _3, the addition of _{SrTiO 3 (Bi, Na) TiO} 3 - SrTiO 3 based on a portion of the solid solution (Bi, Na) TiO ₃ is characterized in that substituted by BiAlO _3.

In addition, the lead-free piezoelectric ceramics _{(1-xz) Bi 1/} 2 Na 1/2 TiO 3 - xSrTiO 3 - zBiAlO 3 ( wherein x is 0.21≤x≤0.30, wherein z is 0 <z≤0.03 Im) such as It is characterized by having a composition.

In addition, the lead-free piezoelectric ceramics are characterized by having a normalized strain (S _max / E _max ) of 200 to 670 pm / V in an electric field of 4 kV / mm.

In addition, it is characterized in that the actuator containing the lead-free piezoelectric ceramics.

In addition, _{Bi 1/2 Na 1/2} TiO 3 - SrTiO 3 - CaTiO 3 Wet mixing the oxide powder of Bi, Na, Sr, Ti, Ca constituting the composition, calcining the mixed powder, wet milling the calcined powder, pressurized to form a molded body and sintered the molded body comprising, wherein the sintered body is _{(1-xy) Bi 1/} 2 Na 1/2 TiO 3 - xSrTiO 3 - yCaTiO 3 ( wherein x is 0.22≤x≤0.30, wherein y is 0 <y≤0.04 Im ) Having a composition.

In addition, _{Bi 1/2 Na 1/2} TiO 3 - SrTiO 3 - BiAlO 3 Wet mixing oxide powders of Bi, Na, Sr, Ti, and Al, calcination of the mixed powder, wet pulverizing the calcined powder, and then pressing to form a compact and sintering the compact comprising, wherein the sintered body _{(1-xz) Bi 1/} 2 Na 1/2 TiO 3 - xSrTiO 3 - zBiAlO 3 ( wherein x is 0.21≤x≤0.30, wherein z is 0 <z≤0.03 Im ) Having a composition.

Referring to the effect of the high strain-free Samsung system based piezoelectric ceramic composition according to the embodiments of the present invention.

The present invention can provide a piezoelectric ceramic material of bismuth (Bi) system, unlike Pb (Zr, Ti) O ₃ (hereinafter PZT) of lead (Pb) system which is harmful to the human body and causes environmental pollution.

In addition, it provides lead-free piezoceramic materials with high field induction strain, which can be applied to piezoelectric actuators.

However, the effect that can be achieved by the high strain-free Samsung system lead-free piezoelectric ceramic composition according to the embodiments of the present invention is not limited to those mentioned above, and other effects not mentioned are belong to the present invention from the following description It will be clearly understood by those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, included as part of the detailed description in order to provide a thorough understanding of the present invention, provide examples of the present invention and together with the description, describe the technical idea of the present invention.
1 is _{(1-xy) Bi 1/} 2 Na 1/2 TiO 3 according to the invention of yCaTiO ₃ (wherein x is 0.22≤x≤0.30, wherein y is 0 <y≤0.04 Im) - xSrTiO ₃ It is a flowchart which shows the lead-free piezoelectric ceramics manufacturing method with respect to a composition.
Figure 2 is (1-xz) according to the present invention, _{Bi 1/2 Na 1/2} TiO 3 - xSrTiO 3 - zBiAlO 3 (Where x is 0.21 ≦ x ≦ 0.30, and z is 0 <z ≦ 0.03), which is a flowchart showing a method for producing a lead-free piezoelectric ceramic.
Figure 3 is one embodiment according to the example _{(1-xy) Bi 1/} 2 Na 1/2 TiO 3 of the present invention - xSrTiO ₃ - yCaTiO ₃ (wherein x is 0.22≤x≤0.30, wherein y is 0 <y≤ It is a graph showing the electric field organic deformation characteristic curve of the lead-free piezoceramic material for the composition of 0.04).
Figure 4 is one embodiment according to the example _{(1-xz) Bi 1/} 2 Na 1/2 TiO 3 of the present invention - xSrTiO ₃ - zBiAlO ₃ (wherein x is 0.21≤x≤0.30, wherein z is 0 <z≤ It is a graph showing the electric field organic deformation characteristic curve of lead-free piezoceramic material for the composition of 0.03).
5 is a graph showing electric field organic deformation characteristic curves of lead-free piezoelectric ceramic materials with respect to the composition of Preparation Example 31.

The terms or words used in this specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way. Based on the principle that it can, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only one of the most preferred embodiments of the present invention, and do not represent all of the technical idea of the present invention, which can be replaced at the time of the present application It should be understood that there may be various equivalents and variations. Hereinafter, a high-strain samsung-based piezoelectric ceramic composition according to an embodiment of the present invention will be described in detail.

1 is _{(1-xy) Bi 1/} 2 Na 1/2 TiO 3 according to the invention of yCaTiO ₃ (wherein x is 0.22≤x≤0.30, wherein y is 0 <y≤0.04 Im) - xSrTiO ₃ is a flow chart illustrating a lead-free piezoelectric ceramic manufacturing method for the composition, 2 is a Bi _{1 (1-xz)} according to the invention _{/ 2 Na 1/2 TiO 3} - xSrTiO 3 - zBiAlO 3 (Where x is 0.21 ≦ x ≦ 0.30, and z is 0 <z ≦ 0.03), which is a flowchart showing a method for producing a lead-free piezoelectric ceramic.

A lead-free piezoelectric ceramic according to an embodiment of the present invention has a perovskite crystal structure, and SrTiO ₃ is added based on (Bi, Na) TiO ₃ including Bi, Na, Ti, and O as a main component. the (Bi, Na) TiO ₃ - characterized by having on the SrTiO ₃ based solid solution portion of the (Bi, Na) TiO ₃ is substituted with a CaTiO _3, the composition of formula (I).

[Formula 1]

_{(1-xy) Bi 1/} 2 Na 1/2 TiO 3 - xSrTiO 3 - yCaTiO 3

Where x is 0.22 ≦ x ≦ 0.30 and y is 0 <y ≦ 0.04)

A lead-free piezoelectric ceramic according to another embodiment has a perovskite crystal structure, and SrTiO ₃ is added based on (Bi, Na) TiO ₃ including Bi, Na, Ti, and O as a main component. Bi, Na) TiO ₃ - on the SrTiO ₃ based solid solution (part of Bi, Na) TiO ₃ is substituted with a BiAlO _3, characterized by having the composition of formula (2).

[Formula 2]

_{(1-xz) Bi 1/} 2 Na 1/2 TiO 3 - xSrTiO 3 - zBiAlO 3

Where x is 0.21 ≦ x ≦ 0.30 and z is 0 <z ≦ 0.03)

1 and 2, the method of manufacturing the lead-free piezoelectric ceramics will be described in detail as follows.

For the production of lead-free piezoelectric ceramic according to the formula (1), of a normal purity is used as industrial water _{Bi 1/2 Na 1/2} TiO 3 - SrTiO 3 - CaTiO 3 Oxide powder of Bi, Na, Sr, Ti, Ca constituting the composition, that is, using the ceramic powder, such as Bi ₂ O ₃ , Na ₂ CO ₃ , TiO ₂ , SrCO ₃ , CaCO ₃ , ZrO ₂ to satisfy the formula Basis weight (weighing) to have a composition to be wet mixed in a ball milling (ball milling) process for 48 hours (S100).

Then, the mixture is dried in a dough state and then calcined for about 2 hours at about 850 (calcine) in order to cause a solid phase chemical reaction (S110). The calcined ceramic composition is wet milled and assembled, and then molded by a compression molding method using a press (S120). When molding, a mold having a diameter of 12 mm may be formed at a pressure of about 100 MPa (S130). The shaped body may be sintered in an electric furnace for about 1175 to 2 hours to produce a plate-shaped specimen.

Method for producing a lead-free piezoelectric ceramic according to the formula (2) is _{Bi 1/2 Na 1/2} TiO 3 - SrTiO 3 - BiAlO 3 Oxide powder of Bi, Na, Sr, Ti, Al constituting the composition, that is, using the ceramic powder of Bi ₂ O ₃ , Na ₂ CO ₃ , TiO ₂ , SrCO ₃ , ZrO ₂ , Al ₂ O ₃ To have a composition that satisfies the basis weight (weighing) and wet mixing for 24 hours in a ball milling (ball milling) process (S200). Steps S210, S220, and S230 are the same as the above-described steps S110, S120, and S130.

Table 1 shows an example of the production of lead-free piezoelectric ceramics manufactured by the above method and satisfying the general formulas (1) and (2).

Preparation Examples 1 to 18 of formula _{(1-xy) Bi 1/} 2 Na 1/2 TiO 3 - xSrTiO 3 - yCaTiO 3 Will showing a lead-free piezoelectric ceramic having a structure, Production Example 19 to 33 is a formula (2) is _{(1-xz) Bi 1/} 2 Na 1/2 TiO 3 - xSrTiO 3 - zBiAlO 3 A lead-free piezoceramic having a structure is shown.

In Chemical Formula 1, x was changed to 0.22, 0.24, 0.26, 0.28, and 0.30, and y was changed to 0, 0.01, 0.02, 0.03, and 0.04 to prepare lead-free piezoelectric ceramics. In Chemical Formula 2, x was changed to 0.21, 0.22, 0.23, 0.24 and 0.25, and z was changed to 0, 0.01, 0.02, and 0.03 to prepare lead-free piezoelectric ceramics.

Figure 3 is one embodiment according to the example _{(1-xy) Bi 1/} 2 Na 1/2 TiO 3 of the present invention - xSrTiO ₃ - yCaTiO ₃ (wherein x is 0.22≤x≤0.30, wherein y is 0 <y≤ 0.04 Im) is a graph showing the electroluminescent organic modified characteristic curve of a lead-free piezoelectric ceramic material of the composition, Fig. 4 (1-xz) according to one embodiment of the present invention _{Bi 1/2 Na 1/2} TiO 3 - xSrTiO ₃ -zBiAlO ₃ (Where x is 0.21 ≦ x ≦ 0.30, and z is 0 <z ≦ 0.03). It is a graph showing an electric field organic deformation characteristic curve of a lead-free piezoceramic material.

Compositions having various compositions as shown in Table 1 were synthesized by a solid phase reaction method and then sintered at high temperature to evaluate dielectric and piezoelectric properties.

Specifically, in order to polarize the sintered body produced by the manufacturing method according to the present invention, the thickness was processed to about 1.0 mm, and then the silver electrodes were applied and subdivided on both sides by a printing coating method to form electrodes. The field strain was measured using a linear variable differential transducer (LVDT) while applying high voltage to both sides of the specimen.

S _max / E _max were calculated through the measured field induction strain curves shown in FIGS. 3 and 4, and are shown in Tables 2 and 3. Table 2 shows the field organic deformation characteristics satisfying the composition of Formula 1.

Production Example 1, Production Example 2, Production Example 5, Production Example 10, and Production Example 15 are compositions having a y value of 0 and which do not have the technical features of the present invention.

The lead-free piezoelectric ceramics satisfying the composition of Formula 1 according to the present invention may have a normalized strain (S _max / E _max ) of 290 to 610 pm / V at an electric field of 4 kV / mm.

Electroluminescent organic deformation characteristic _{(1-xy) Bi 1/} 2 Na 1/2 TiO 3 - xSrTiO 3 - the value if at yCaTiO ₃ the value of x increased with 0.22, 0.24, 0.26, 0.28, but greater than 0.28 is Decreases. As the value of y increases to 0, 0.01, 0.02, 0.03, and 0.04, the field organic deformation characteristic decreases.

The largest value (603 pm / V) was shown by the manufacture example 11 which x value is 0.28 and y value is 0.01.

Table 3 shows the field organic deformation characteristics satisfying the composition of formula (2).

Production Example 25, Production Example 30, and Production Example 33 are compositions having a z value of 0 and which do not have the technical features of the present invention.

The lead-free piezoelectric ceramics satisfying the composition of Chemical Formula 2 according to the present invention may have a 200 to 670 pm / V normalized strain (S _max / E _max ) at an electric field of 4 kV / mm.

Electroluminescent organic deformation characteristic _{(1-xz) Bi 1/} 2 Na 1/2 TiO 3 - xSrTiO 3 - in zBiAlO ₃ the value of x increased with the 0.21, 0.22, 0.23, but if larger than 0.23 and the value is reduced . The value of z increased as 0.01, 0.02, and 0.03 when the value of x was 0.21. However, when x was 0.22, z showed the largest value at 0.02. Also, when x was 0.23, z was the largest value at 0.01.

The largest value (662 pm / V) was shown in the manufacture example 31 which x value is 0.25 and z value is 0.01.

Ferroelectric _{(1-x) Bi 1/} 2 Na 1/2 TiO 3 is tetragonal solid solution at x = 0.16 to 0.20 region to form a feature myeonjeong phase boundary region. In this phase boundary region, piezoelectric properties are superior to those in the composition outside the region, but the field organic deformation characteristics S _max / E _max are 250 pm / V or less, and are practically insufficient.

However, by employing a perovskite compound such as CaTiO ₃ , BiAlO ₃ and the like, it is possible to obtain excellent field organic deformation characteristics over 250 pm / V, which is a practical range. The material thus obtained does not contain lead, which is harmful to the human body, unlike conventional PZT. On the other hand, the actuator according to another embodiment of the present invention may include a lead-free piezoelectric ceramics according to an embodiment of the present invention.

5 is a graph showing electric field organic deformation characteristic curves of lead-free piezoelectric ceramic materials with respect to the composition of Preparation Example 31.

Preparation shown in the Table 2, calculated from a plot of 5 Example 31, that is, four in kV / mm electric field _{(1-xz) Bi 1/} 2 Na 1/2 TiO 3 - xSrTiO 3 - x is 0.25 in zBiAlO ₃ z It can be seen that the electric field organic strain (pm / V) was the highest at 662 pm / V when is 0.01.

While the exemplary embodiments of the present invention have been described in detail above, those skilled in the art will appreciate that various modifications can be made to the above-described embodiments without departing from the scope of the present invention. . Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

Claims (9)

Has a perovskite crystal structure,
Wherein a SrTiO ₃ based solid solution, a part of the _{(Bi, Na) TiO 3 -} Bi, Na, Ti, containing O (Bi, Na) A by a matrix of TiO _3, the addition of _{SrTiO 3 (Bi, Na) TiO} 3 It is characterized in that substituted with CaTiO ₃ , characterized in that having a composition of the formula (1), lead-free piezoelectric ceramics.
[Formula 1]
(1-xy) Bi _1/2 Na _1/2 TiO ₃ -xSrTiO ₃ -yCaTiO ₃
Where x is 0.22 ≦ x ≦ 0.30 and y is 0 <y ≦ 0.04)
delete The method of claim 1,
The lead-free piezoelectric ceramics have a 290 to 610 pm / V normalized strain (S _max / E _max ) in the electric field of 4 kV / mm lead-free piezoelectric ceramics.
Has a perovskite crystal structure,
Wherein a SrTiO ₃ based solid solution, a part of the _{(Bi, Na) TiO 3 -} Bi, Na, Ti, containing O (Bi, Na) A by a matrix of TiO _3, the addition of _{SrTiO 3 (Bi, Na) TiO} 3 It is characterized in that substituted with BiAlO ₃ , characterized in that having a composition of the formula (2), lead-free piezoelectric ceramics.
[Formula 2]
(1-xz) Bi _1/2 Na _1/2 TiO ₃ -xSrTiO ₃ -zBiAlO ₃
Where x is 0.21 ≦ x ≦ 0.30 and z is 0 <z ≦ 0.03)
delete The method of claim 4, wherein
The lead-free piezoelectric ceramics are lead-free piezoelectric ceramics having a normalized strain (S _max / E _max ) of 200 to 670 pm / V in an electric field of 4 kV / mm.
An actuator comprising the lead-free piezoelectric ceramic of any one of claims 1, 3, 4 and 6.
Wet mixing oxide powders of Bi, Na, Sr, Ti, and Ca constituting Bi _1/2 Na _1/2 TiO ₃ -SrTiO ₃ -CaTiO ₃ ;
Calcining the mixed powder;
Wet grinding the calcined powder and then pressing to form a compact; And
Sintering the molded body to form a sintered body;
The sintered body is a lead-free piezoelectric ceramics manufacturing method characterized in that it has a composition of the formula (1).
[Formula 1]
(1-xy) Bi _1/2 Na _1/2 TiO ₃ -xSrTiO ₃ -yCaTiO ₃
Where x is 0.22 ≦ x ≦ 0.30 and y is 0 <y ≦ 0.04)
Wet mixing oxide powders of Bi, Na, Sr, Ti, and Al forming Bi _1/2 Na _1/2 TiO ₃ -SrTiO ₃ -BiAlO ₃ ;
Calcining the mixed powder;
Wet grinding the calcined powder and then pressing to form a compact; And
Sintering the molded body to form a sintered body;
The sintered body has a composition of the following formula (2) lead-free piezoelectric ceramics manufacturing method.
[Formula 2]
(1-xz) Bi _1/2 Na _1/2 TiO ₃ -xSrTiO ₃ -zBiAlO ₃
Where x is 0.21 ≦ x ≦ 0.30 and z is 0 <z ≦ 0.03)

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