KR102808599B1 - POLYCRYSTALLINE PIEZOELECTRIC MATERIAL COMPRISING PLATE―LIKE BaTiO3 TEMPLATE, AND METHOD OF FABRICATING THE SAME - Google Patents

Abstract

According to the present invention, by aligning crystal grains of a polycrystalline piezoelectric material in one direction, a polycrystalline piezoelectric material having a domain alignment structure similar to a single crystal is provided, thereby providing a piezoelectric material having piezoelectric properties close to single-crystal piezoelectric ceramics and mechanical properties much superior to those of a single crystal. In particular, in this process, by substituting Bi ³⁺ with Sm ³⁺ in a BiScO ₃ -PbTiO ₃ piezoelectric ceramic, a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ was designed, and x was controlled to be 0.02 to 0.04, thereby substituting Bi ³⁺ with Sm ³⁺ , thereby improving the piezoelectric properties and maintaining the Curie temperature (Tc) without significantly decreasing. It is expected that such a piezoelectric ceramic according to the present invention can be used in high-temperature actuators or transducers.

Description

Polycrystalline piezoelectric material using plate-like BaTiO3 template and method of fabricating the same {POLYCRYSTALLINE PIEZOELECTRIC MATERIAL COMPRISING PLATE―LIKE BaTiO3 TEMPLATE, AND METHOD OF FABRICATING THE SAME}

The present invention relates to a high-temperature piezoelectric ceramic composition having a high Curie temperature (Tc) and excellent piezoelectric properties, and a method for producing the same.

In order to manufacture a piezoelectric material with improved piezoelectric properties of the present invention, the crystal orientation of polycrystalline 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ (BSS-PT) is controlled using a BaTiO ₃ seed layer.

Piezoelectric materials are divided into single-crystal piezoelectric materials and polycrystalline piezoelectric materials. Single-crystal piezoelectric materials have the problem that it takes a lot of time and money to grow and produce the crystal.

In the case of polycrystalline piezoelectric materials, the cost is much lower than that of single crystals, but in the case of polycrystals, there is a problem of poor piezoelectric properties because the crystal direction of each grain is not aligned in one direction.

Therefore, if a method for manufacturing polycrystalline piezoelectric materials can be used to align crystal grains in one direction as much as possible while producing polycrystalline piezoelectric materials, thereby creating a domain-aligned structure similar to that of a single crystal, it would be a very effective technology.

In addition, the present invention relates to a method for manufacturing a piezoelectric ceramic having a high Curie temperature (Tc) and improved piezoelectric properties, while making a polycrystalline piezoelectric material by using a method for manufacturing a polycrystalline piezoelectric material to align crystal grains in one direction as much as possible to create a domain-aligned structure similar to a single crystal, and also discloses a piezoelectric ceramic having a high Curie temperature (Tc) and improved piezoelectric properties, manufactured by this manufacturing method. BiScO ₃ -PbTiO ₃ piezoelectric ceramics, known as high-temperature piezoelectric ceramics due to their high Curie temperature, are widely used as high-temperature piezoelectric ceramics. At this time, a piezoelectric ceramic that further improves the piezoelectric properties of BiScO ₃ -PbTiO ₃ piezoelectric ceramics while at the same time not lowering the Curie temperature would be very promising in the market. To this end, the present invention aims to propose a piezoelectric ceramic having excellent piezoelectric properties by designing a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ by replacing Bi ³⁺ with Sm ³⁺ in a _BiScO 3 -PbTiO ₃ piezoelectric ceramic.

Patent Registration No. 10-2308852 (September 28, 2021)

The present invention provides a piezoelectric ceramic having a high Curie temperature (Tc) and improved piezoelectric properties, and a method for manufacturing the same. In the present invention, by replacing Bi ³⁺ with Sm ³⁺ in a BiScO ₃ -PbTiO ₃ piezoelectric ceramic, a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ is designed to provide a piezoelectric ceramic having excellent piezoelectric properties, and at the same time, by aligning crystal grains of the polycrystalline piezoelectric material in one direction, a polycrystalline piezoelectric material having a domain-aligned structure similar to a single crystal is provided.

Specifically, the present invention provides a polycrystalline _0.36 (Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} (BSS-PT) using a _BaTiO3 seed layer to manufacture a piezoelectric material with improved piezoelectric properties. We want to control the decision orientation.

A method for manufacturing polycrystalline 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ using a BaTiO ₃ seed layer according to one embodiment of the present invention comprises the steps of: preparing a slurry including a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ and performing ball milling; adding a plurality of BaTiO ₃ seed layers to the slurry; manufacturing a template sheet using the slurry using a tape casting process; and sintering the template sheet, wherein the polycrystalline 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ is aligned along a crystal direction of the BaTiO ₃ seed layer by the BaTiO ₃ seed layer, and x is 0.02 to 0.04.

Ball milling of the above slurry is carried out in an ethanol solvent for 4 to 24 hours.

The step of adding a BaTiO ₃ seed layer to the above slurry is performed by adding a BaTiO ₃ seed layer to the above slurry and mixing for 12 to 24 hours under an ethanol solvent.

The above BaTiO ₃ seed layer is in the form of a thin film sheet.

The above BaTiO ₃ seed layers have the same crystal orientation.

In the step of manufacturing a template sheet using the above slurry using a tape casting process, the height of the blade of the tape casting device is controlled so that the BaTiO ₃ seed layer in the form of a thin film is arranged within the template sheet so that all of the seed layers have the same crystal orientation.

The height of the above blade is controlled to be higher than the thickness perpendicular to the plane of the BaTiO ₃ seed layer.

The step of sintering the above template sheet is performed at a temperature of 1100 to 1200°C for 2 to 10 hours.

The step of sintering the above template sheet is performed at 1150°C for 10 hours.

In the step of adding a plurality of BaTiO ₃ seed layers to the above slurry, the BaTiO ₃ seed layers are added in an amount of more than 0 and less than or equal to 2 vol%. The BaTiO ₃ seed layers are added in an amount of 1 vol%.

The powder having the composition of 0.36(Bi _{( 1-x)} Sm _x )ScO ₃ -0.64PbTiO ₃ above is obtained through the steps of: designing a ^powder having the composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO 3 by replacing Bi ₃₊ with Sm ³⁺ in the composition of 0.36BiScO 3 -0.64PbTiO ₃ ; mixing the powder through a first ball milling; performing a calcination step after the mixing step; performing a second ball milling step after the calcination; and drying.

In the above 0.36BiScO ₃ -0.64PbTiO ₃ composition, Bi ³⁺ is replaced with Sm ³⁺ to design a powder composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ , and the first ball milling is mixed. Bi ₂ O ₃ powder, Sm ₂ O ₃ powder, Sc ₂ O ₃ powder, PbO powder, and TiO ₂ powder are mixed according to the composition formula, and mixed through ball milling with ethanol for 24 hours.

The above calcining step is performed at 750 to 800°C for 2 to 4 hours.

The above calcination step is performed at 775°C for 4 hours.

The second ball milling step after the above calcination is performed with ethanol for 48 hours.

A polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3 piezoelectric} material using a BaTiO3 _seed layer has crystal orientation and a Curie temperature of 400°C or higher. The _BaTiO3 seed layer may be added in an amount of more than 0 vol% and less than or equal to 2 vol%, and the _BaTiO3 seed layer may be added in an amount of 0.1 vol%.

According to the present invention, by aligning crystal grains of a polycrystalline piezoelectric material in one direction, a polycrystalline piezoelectric material having a domain alignment structure similar to a single crystal is provided, thereby providing a piezoelectric material having piezoelectric properties close to single-crystal piezoelectric ceramics and mechanical properties much superior to those of a single crystal. In particular, in this process, by substituting Bi ³⁺ with Sm ³⁺ in a BiScO ₃ -PbTiO ₃ piezoelectric ceramic, a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ was designed, and x was controlled to be 0.02 to 0.04, thereby substituting Bi ³⁺ with Sm ³⁺ , thereby improving the piezoelectric properties and maintaining the Curie temperature (Tc) without significantly decreasing. It is expected that such a piezoelectric ceramic according to the present invention can be used in high-temperature actuators or transducers.

FIG. 1 illustrates a flow chart of a method for controlling crystal orientation of polycrystalline BSS-PT using a BaTiO ₃ seed layer according to one embodiment of the present invention.
Figure 2 illustrates a flow chart of steps for preparing _a powder having a composition of 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} .
Figure 3 illustrates an overall process diagram according to the manufacturing method of the present invention.
Figure 4 shows the change in thickness of the template sheet according to the relationship regarding the height of the blade.
Figure 5 is a graph of the piezoelectric properties of a piezoelectric composition manufactured according to Example 2.
Figure 6 is 0.36BSS-0.64PT - It shows the change in piezoelectric properties according to sintering temperature in a piezoelectric composition manufactured with 1 vol% BaTiO ₃ .
Figures 7 and 8 are 0.36BSS-0.64PT - This is a graph of the piezoelectric properties of a piezoelectric composition manufactured with x vol% BaTiO ₃ (sintering temperature was 1150℃ for 10 hours) and shows the change in piezoelectric properties according to the content of BaTiO ₃ .
Various embodiments are now described with reference to the drawings, wherein like reference numerals are used throughout the drawings to refer to like elements. For purposes of explanation, various descriptions are set forth herein to provide an understanding of the invention. It will be apparent, however, that such embodiments may be practiced without these specific descriptions. In other instances, well-known structures and devices are shown in block diagram form to facilitate the description of the embodiments.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention can be modified in various ways and can have various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention. In describing each drawing, similar reference numerals were used for similar components.

The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprises" or "has" and the like are intended to specify the presence of a feature, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, steps, operations, components, parts, or combinations thereof.

The present invention relates to a piezoelectric material with improved piezoelectric properties, and to manufacture the piezoelectric material with improved piezoelectric properties of the present invention, the crystal orientation of polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} (BSS-PT) _is controlled using a _BaTiO3 seed layer. According to the present invention, by aligning crystal grains of the polycrystalline piezoelectric material in one direction, a polycrystalline piezoelectric material having a domain alignment structure similar to that of a single crystal is provided, thereby providing a piezoelectric material having piezoelectric properties close to those of a single crystal piezoelectric ceramic and mechanical properties much superior to those of a single crystal.

The characteristic value of a piezoelectric material is determined by the chemical composition, which is an intrinsic characteristic, but can also vary greatly by the structure of the crystal grains or the structure of the piezoelectric domain. Accordingly, research on improving the characteristic value using grain engineering or domain engineering technology was conducted in the present invention. The technology of the present invention is a groundbreaking technology that can improve the piezoelectric properties by 1.5 to 2 times compared to existing polycrystalline piezoelectric materials by creating a domain alignment structure similar to a single crystal by aligning the crystal grains of the polycrystalline piezoelectric material in one direction.

FIG. 1 illustrates a flow chart of a method for controlling crystal orientation of polycrystalline BSS-PT using a BaTiO ₃ seed layer according to one embodiment of the present invention.

A method for manufacturing polycrystalline 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ using a BaTiO ₃ seed layer according to one embodiment of the present invention includes the steps of: preparing a slurry including a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ and performing ball milling (S 110); adding a plurality of BaTiO ₃ seed layers to the slurry (S 120); producing a template sheet using the slurry using a tape casting process (S 130); and sintering the template sheet (S 140).

In step S 110, a slurry containing powders with a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ is prepared and ball milling is performed. The ball milling of the slurry is performed in an ethanol solvent for 4 to 24 hours. Ball milling is typically performed using zirconia balls of various sizes, but is not limited thereto.

In step S 110, a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ is prepared. Figure 2 illustrates a flow chart of the steps for preparing a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ .

The step of preparing a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ includes a step of designing a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ by replacing Bi ³⁺ with Sm ³⁺ in the composition of 0.36BiScO ₃ -0.64PbTiO ₃ and mixing the powder through a first ball milling (S 210); a step of performing a calcination after the mixing step (S 220); a step of performing a second ball milling after the calcination (S 230); and a step of drying (S 240).

In step S 210, the powder composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ is designed by replacing Bi ³⁺ with Sm ³⁺ in the 0.36BiScO ₃ -0.64PbTiO ₃ composition, and is mixed through the first ball milling. This is done by mixing Bi ₂ O ₃ powder, Sm ₂ O ₃ powder, Sc ₂ O ₃ powder, PbO powder, and TiO ₂ powder according to the composition formula. The powders are poured into a polyethylene bottle together with ethanol, and then mixed and ground using zirconia ball media with various diameters for 24 hours. The mixing is performed through ball milling for 24 hours. In this case, the molar ratio x can be controlled in the composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ , and x is controlled to 0.02 to 0.04, and most preferably 0.03 as described later. In this case, it can be seen that the optimal ratio is such that the piezoelectric properties are improved while Tc is maintained, and this will be further explained in Example 1 described later. Since both Bi ³⁺ and Sm ³⁺ are trivalent ions, they can be controlled in terms of content by the relationship as described above, and as Bi ³⁺ decreases, Sm ³⁺ is added. In the present invention, since Bi is substituted with Sm, the ABO ₃ perovskite structure is maintained.

In step S 220, the powder mixed in step S 210 is calcined. The calcination step is performed by completely drying the ethanol, placing the dried powder in an alumina crucible, and heating at 750 to 800°C for about 2 to 4 hours, and the temperature rising condition for calcination is 5°C/min. The optimal condition for calcination is to perform calcination at 775°C for about 4 hours. Through this calcination step, the powder is manufactured using a solid-state diffusion reaction. In addition, it can be seen that it is the most optimal temperature because no secondary phase appears at 775°C in particular.

In step S 230, the calcined powder is subjected to secondary ball milling after calcination. The calcined powder is crushed to make the particle size smaller, and then the powder is injected into a polyethylene bottle together with ethanol, and ball milling is performed using zirconia ball media of various sizes. The ball milling step is performed for 48 hours.

At step S 240, the powder is dried in an oven at about 90°C for about 12 hours after ball milling.

In step S 120, a plurality of BaTiO ₃ seed layers are added to the slurry. The BaTiO ₃ seed layers are added to the slurry and mixed under an ethanol solvent for 12 to 24 hours. The BaTiO ₃ seed layers are in the form of thin film sheets, which are manufactured separately. The plurality of BaTiO ₃ seed layers added in step S 120 have the same crystal orientation. In the step of adding a plurality of BaTiO ₃ seed layers to the slurry, the BaTiO ₃ seed layers are added in an amount of more than 0 and less than or equal to 2 vol%, and more preferably, the BaTiO ₃ seed layers are added in an amount of 1 vol%.

In step S 130, a template sheet is produced using a tape casting process. As shown in Fig. 3, a template sheet is produced using a tape casting process using a slurry. By controlling the height of the blade of the tape casting device, the BaTiO ₃ seed layers in a thin film form are arranged within the template sheet so that they all have the same crystal orientation. In this case, the height of the blade is controlled to be higher than the thickness perpendicular to the plane of the BaTiO ₃ seed layer. By controlling in this way, the BaTiO ₃ seed layers can be arranged so that they all have the same orientation when they exit the blade and exit flatly, which can be confirmed in Fig. 3.

Specifically, the height of the blade is determined by the following relationship:

ΔP, H, μ, t, and U represent the pressure in the reservoir, blade gap, slurry density, blade thickness, and carrier velocity, respectively.

Figure 4 illustrates the change in thickness of the template sheet according to the relationship regarding the height of the blade. Specifically, as can be seen in Figure 4, A value of 3 or less is desirable, meaning that the blade height is less than three times the seed size.

For example, a piezoelectric slurry with uniformly dispersed BT seeds is applied to a carrier film at a certain thickness by a doctor blade and passes through a drying oven divided into four sections of 0℃, 25℃, 45℃, and 60℃ to volatilize various organic substances, and then is manufactured into a roll shape at the end of the equipment. In order for the BT seeds to align in one direction as they pass through the doctor blade and manufacture a uniform piezoelectric sheet, it is essential to adjust the doctor blade gap. If the blade gap is too narrow, defects such as line-shaped stains are likely to occur in the sheet, and if it is too wide, the seeds are not properly aligned in one direction even when they pass through the blade. Therefore, for example, when using BT seeds with a size of about 10 ㎛, casting is performed by setting the gap of the doctor blade to a range of about 20 to 30 ㎛, which is 2 to 3 times the seed size. In this tape casting process, the variable Π representing the ratio between the pressure driving force and the slurry driving force is expressed as the equation above. According to this formula, uniformly aligned sheets can be finally obtained by controlling the carrier speed under constant pressure and slurry conditions.

In step S 140, the template sheet is sintered. The step of sintering the template sheet is performed at a temperature of 1100 to 1200°C for 2 to 10 hours, and preferably at 1150°C for 10 hours.

_{Polycrystalline} 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} (BSS-PT) using _BaTiO3 seed layer according to this embodiment of the present invention Polycrystalline 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ (BSS-PT) manufactured by using a method for controlling the crystal orientation of a BaTiO ₃ seed layer is aligned along the crystal direction of the BaTiO ₃ seed layer. That is, the polycrystalline 0.36(Bi _{( 1-x) Sm x} ) _{ScO 3 -0.64PbTiO 3} (BSS-PT) piezoelectric material including _a BaTiO ₃ seed layer manufactured by the method of the present invention has crystal orientation.

_{Polycrystalline} 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} (BSS-PT) including a _BaTiO3 seed layer according to one embodiment of the present invention In piezoelectric materials, in polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} (BSS-PT) _, x is 0.02 to 0.04, and preferably x is 0.03.

In addition, in the polycrystalline BiScO ₃ -PbTiO ₃ piezoelectric material including a BaTiO ₃ seed layer according to one embodiment of the present invention, BaTiO ₃ is contained in an amount of more than 0 vol% and less than or equal to 2 vol%, and preferably, BaTiO ₃ is contained in an amount of 1 vol%.

_{Polycrystalline} 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} (BSS-PT) comprising a _BaTiO3 seed layer having crystal orientation, manufactured according to the method of the present invention Piezoelectric materials have crystal orientation and exhibit a high Tc Curie temperature of 400℃ or higher. These piezoelectric materials can be used in applications exhibiting various piezoelectric properties, such as ultrasonic transducers.

Below, the contents of the present invention will be further described with specific examples.

In Example 1, a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ was prepared.

In this experiment, in the BiScO ₃ -PbTiO ₃ binary system, the MPB composition of 0.36BiScO ₃ -0.64PbTiO ₃ was designed by replacing Bi ³⁺ with Sm ³⁺ at 0, 1, 2, 3, 4, and 5 mol%. The composition was 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05).

A general solid-state synthesis method was used to synthesize the powder, _and the raw materials used were _Bi2O3 (Kojundo Chemical, 99.99%, Japan), _Sm2O3 (Kojundo Chemical, 99.9%, Japan), _Sc2O3 (Kojundo Chemical, 99.9%, Japan), _PbO (Kojundo Chemical, 99.99%, _TiO2 (Sigma-Aldrich, 99.9%, Germany). _The raw material _powders were weighed according to the molecular weight of the composition formula 0.36(Bi _(1-x) Sm _x ) _ScO3 -0.64PbTiO3 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) and placed in a polyethylene bottle. Then, ethanol (Daejung Chemical & Metal, 99.9%, Korea) and zirconia balls (ф = 1 mm, 3 mm, 5 mm, 10 mm) were additionally added and mixed and ground through primary ball milling for 24 hours, and then dried in a 90 ^o C oven. The dried powder was placed in a sealed alumina crucible and calcined at 775 ^o C for 4 hours at a heating rate of 5 ^o C per minute. In the case of calcination, calcination was performed at a heating rate of 5 o C per minute at 750 to 800 ° C, and 775 ° C, a temperature at which a secondary phase does not appear, was selected as the appropriate calcination temperature. In order to make the calcined powder have a particle size of about 0.5 μm, it was placed in a polyethylene bottle together with ethanol and zirconia balls and subjected to secondary ball milling for 48 hours. About 4 hours before the completion of the ball milling, 0.5 wt% of binder was added, and the ball milling was completed, and it was dried in a drying oven at 90 ° C for about 12 hours. x is 0.02 to 0.04 It was desirable, and most preferably, x was 0.03.

In Example 2, a piezoelectric thick-film element was manufactured by adding a BaTiO ₃ seed layer to a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO ₃ -0.64PbTiO ₃ . x was preferably controlled to 0.02 to 0.04, and most preferably, x was controlled to 0.03.

To prepare BSS-PT piezoelectric slurry, ethanol (Daejung, 99.9%, Korea), toluene (Daejung, 99.5%, Korea), dibutylphthalate (Daejung, 99.9%, Korea), polyvinyl butyral (BM-SZ, Sekisui, Japan), a dispersant (BYK-111, BYK-chemie GmbH, Germany) and BSS-PT piezoelectric ceramic powder were mixed at an optimal ratio and placed into a polyethylene bottle with zirconia balls (ф 3 mm, 5 mm, 10 mm), followed by mixing and grinding for 24 hours. After mixing, the slurry was filtered out using a mesh to remove the balls and sieved evenly.

The BaTiO ₃ (BT) platelets selected as seed material were weighed at 0, 1, 2, 4, and 8 vol%, and then ethanol and a dispersant were added to each vial, dispersed in a sonicator for 3 minutes, and then added to the slurry. The slurry containing BT was defoamed for 20 minutes to remove residual air bubbles, and then stabilized and dispersed BT through an aging process at 15 rpm for 3 hours. A general tape casting process was used to manufacture BSS-PT thick film sheets templated with BT seeds. After setting the height of the doctor blade to approximately 100 μm, the tape casting process was performed at a speed of 0.5 m/min to manufacture thick film sheets with a thickness of approximately 35 μm. The manufactured thick film sheets were laminated using a laminator at 60°C and 15 MPa to a thickness of approximately 1.5 mm, and then pressed using WIP (warm isostatic pressing) at 65°C and 25 MPa for 20 minutes. The laminated sheets were cut to 10 mm x 10 mm using a blade cutter, and then burnt out to volatilize the binder in an air atmosphere at 300°C for 2 hours and then at 600°C for 2 hours. The burnt-out devices were sufficiently muffled with powders of the same composition and then sintered at various temperatures (1100°C to 1200°C) for 10 hours in an O ₂ atmosphere of 800 sccm. At this time, the sintering was performed at a rate of 1°C per minute. The sintered thick film specimens had their surfaces polished flat, and then Ag electrodes were applied to both sides using a screen mask, and then they were fired at 700°C for 10 minutes. Polarization was performed in an oil bath at 90°C with an electric field of 4.5 kV/mm for 20 minutes.

Figure 5 is a graph of piezoelectric properties of a piezoelectric composition manufactured according to Example 2. Figure 5 is 0.36BSS-0.64PT - A graph of the piezoelectric properties of a piezoelectric composition manufactured with x vol% BaTiO ₃ (sintering temperature: 1150℃ for 10 hours), showing the change in piezoelectric properties according to the content of BaTiO ₃ .

As shown in Fig. 5, it was confirmed that the piezoelectric properties were very good when the content of BaTiO ₃ was more than 0 and less than 2 vol%, preferably 1 vol%.

d ₃₃ (piezoelectric displacement coefficient) refers to the size of the charge generated when a constant stress is applied or the strain generated when a constant electric field is applied, k _p (electromechanical coupling factor) refers to the conversion efficiency from mechanical energy to electrical energy or from electrical energy to mechanical energy, g ₃₃ (piezoelectric voltage coefficient) refers to the size of the voltage generated when a constant stress is applied, and Q _m (mechanical quality factor) refers to a measure of energy loss during the electromechanical conversion process.

Figure 6 is 0.36BSS-0.64PT - The piezoelectric properties change according to the sintering temperature in a piezoelectric composition manufactured with 1 vol% BaTiO _3. As shown in Fig. 6, it was found that the piezoelectric properties were the best at a sintering temperature of 1100 to 1200°C, preferably 1150°C.

Figures 7 and 8 are 0.36BSS-0.64PT - A piezoelectric characteristic graph of a piezoelectric composition manufactured with x vol% BaTiO ₃ (sintering temperature was 1150℃ for 10 hours) showing the change in piezoelectric characteristics according to the content of BaTiO _3. Fig. 7 shows a PE hysteresis graph and Fig. 8 shows an SE curve.

The BaTiO ₃ -templated 0.36(Bi _1-x Sm _x )ScO ₃ -0.64PbTiO ₃ thick film synthesized through Example 2 had relatively high orientation, and it was confirmed that the 1 vol% BT-templated 0.36(Bi _1-x Sm _x )ScO ₃ -0.64PbTiO ₃ thick film exhibited the best ferroelectric and piezoelectric properties. A large strain (0.44%), d ₃₃ ^* (978 pm/V) and high T _c (above 411℃) could be obtained.

Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims (23)

A step of preparing a slurry including _powders having a composition of 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} and performing ball milling;
A step of adding a plurality of BaTiO ₃ seed layers to the above slurry;
A step of producing a template sheet using the above slurry using a tape casting process; and
Comprising a step of sintering the above template sheet,
Polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} is _aligned along the crystal direction of the BaTiO3 _seed layer by the _BaTiO3 seed layer.
The above x is 0.03,
The step of sintering the above template sheet is performed at a temperature of 1100 to 1200°C for 2 to 10 hours.
In the step of adding a plurality of BaTiO ₃ seed layers to the above slurry, the BaTiO ₃ seed layers are added in an amount of more than 0 and less than 2 vol%.
Method for _{manufacturing} polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} using _BaTiO3 seed layer.
delete delete In paragraph 1,
The above BaTiO ₃ seed layer is in the form of a thin film sheet,
Method for _{manufacturing} polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} using _BaTiO3 seed layer.
delete In paragraph 1,
In the step of producing a template sheet using the above slurry using a tape casting process,
By controlling the height of the blade of the tape casting device, the BaTiO ₃ seed layer in the form of a thin film is arranged within the template sheet so that all of the seed layers have the same crystal orientation.
Method for _{manufacturing} polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} using _BaTiO3 seed layer.
In paragraph 6,
The height of the above blade is controlled to be higher than the thickness perpendicular to the plane of the BaTiO ₃ seed layer.
Method for _{manufacturing} polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} using _BaTiO3 seed layer.
delete In paragraph 1,
The step of sintering the above template sheet is performed at 1150°C for 10 hours.
Method for _{manufacturing} polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} using _BaTiO3 seed layer.
delete In paragraph 1,
The above BaTiO ₃ seed layer is added at 1 vol%.
Method for _{manufacturing} polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} using _BaTiO3 seed layer.
delete In paragraph 1,
The powder having the composition of 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3 is}
A step of designing a powder having a composition of 0.36(Bi _(1-x) Sm _x )ScO 3 -0.64PbTiO ₃ by substituting Bi ³⁺ with Sm ³⁺ in the composition of 0.36BiScO ₃ -0.64PbTiO _{3 ,} and mixing it through the first ball milling;
A calcining step after the above mixing step;
A step of performing secondary ball milling after the above calcination; and
Obtained through the drying step,
Method for _{manufacturing} polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} using _BaTiO3 seed layer.
delete In Article 13,
The above calcining step is performed at 750 to 800°C for 2 to 4 hours.
Method for _{manufacturing} polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} using _BaTiO3 seed layer.
In Article 13,
The above calcination step is performed at 775°C for 4 hours.
Method for _{manufacturing} polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3} using _BaTiO3 seed layer.
delete Manufactured according to the method of any one of claims 1, 4, 6, 7, 9, 11, 13, 15 and 16,
It has a decision orientation,
The Curie temperature is over 400℃,
The above x is 0.03,
The above BaTiO ₃ seed layer is added in an amount of more than 0 and less than 2 vol%.
Polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3 piezoelectric} material using _BaTiO3 seed layer.
delete delete delete In Article 18,
The above BaTiO ₃ seed layer is added at 0.1 vol%.
Polycrystalline 0.36(Bi _{(1-x) Smx} ) _{ScO3-0.64PbTiO3 piezoelectric} material using _BaTiO3 seed layer.
delete

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