KR102308852B1 - BiScO3-PbTiO3 PIEZOELECTRIC MATERIAL COMPRISING BaTiO3 SEED LAYERS, AND METHOD OF FABRICATING THE SAME - Google Patents

Abstract

The present invention relates to a piezoelectric material having improved piezoelectric properties. In order to manufacture a piezoelectric material having improved piezoelectric properties of the present invention, crystalline orientation of a polycrystalline BiScO_3-PbTiO_3 using a BaTiO_3 seed layer is controlled. According to the present invention, crystal grains of the polycrystalline piezoelectric material are aligned in one direction to provide a polycrystalline piezoelectric material having a domain alignment structure similar to mono crystal, thereby providing a piezoelectric material having piezoelectric properties similar to that of mono crystal piezoelectric ceramics and excellent intensity compared to that of the mono crystal in the aspect of mechanical properties.

Description

Polycrystalline BiScO3-PbTiO3 piezoelectric material including BaTiO3 seed layer and manufacturing method thereof

The present invention relates to a piezoelectric material with improved piezoelectric properties.

In order to manufacture a piezoelectric material with improved piezoelectric properties of the present invention, the crystal orientation of polycrystalline BiScO ₃ -PbTiO _{3 using a BaTiO 3 seed layer is controlled.}

Since its inception by the discovery of the piezoelectric effect in 1880 in France Tourmaline (toutmalin) history of piezoelectric material, which was first applied to underwater ultrasonic detector, by developing a BaTiO ₃ in the United States in 1947 became finally applications of piezoelectric ceramics is significantly wider. _{Since then, PbTiO 3} (PT), Pb(Zr, Ti)O ₃ (PZT)-based ceramics with excellent piezoelectric properties have been developed, and the application of piezoelectric materials has been greatly expanded. , and has been applied to a wide range of fields such as measuring instruments.

The piezoelectric material includes a single crystal piezoelectric material and a polycrystalline piezoelectric material. In the case of a single crystal piezoelectric material, there is a problem in that crystal growth and production takes a lot of time and money.

In the case of a polycrystalline piezoelectric material, the cost is much lower than that of a single crystal, but in the case of a polycrystalline piezoelectric material, the crystal direction of each grain is not aligned in one direction, so there is a problem in that the piezoelectric properties are deteriorated.

Therefore, it would be a very effective technique if a domain-aligned structure similar to a single crystal could be created by maximally aligning the grains in one direction while making the polycrystalline piezoelectric material using the method of manufacturing the polycrystalline piezoelectric material.

An object of the present invention is to provide a polycrystalline piezoelectric material having a domain alignment structure similar to that of a single crystal by aligning crystal grains of the polycrystalline piezoelectric material in one direction.

Specifically, the present invention is to control the crystal orientation of _{polycrystalline BiScO 3} -PbTiO _{3 using a BaTiO 3} seed layer in order to manufacture a piezoelectric material with improved piezoelectric properties.

According to an embodiment of the present invention, a method for controlling crystal orientation of polycrystalline BiScO ₃ -PbTiO _{3 using a BaTiO 3 seed layer includes: preparing a slurry including a BiScO 3} -PbTiO ₃ base material powder 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 a step of sintering the template sheet, by BaTiO ₃ seed layer has polycrystalline BiScO ₃ -PbTiO ₃ are aligned along the crystal orientation of the seed BaTiO ₃ layer.

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

Adding BaTiO ₃ to the seed layer on the slurry, the addition of BaTiO ₃ to the seed layer and the slurry is mixed for 12 to 24 hours under an ethanol solvent.

The BaTiO ₃ seed layer is in the form of a thin film sheet, and the BaTiO ₃ seed layer has the same crystal orientation.

In the step of manufacturing the template sheet using the slurry using the tape casting process, the height of the blade of the tape casting apparatus is controlled _{to ensure that all of the BaTiO 3} seed layers in the form of a thin film have the same crystal orientation within the template sheet. are placed The height of the blade is controlled to be higher than the thickness perpendicular to the plane of _{the BaTiO 3 seed layer.}

The step of sintering the template sheet is performed at a temperature of 950 to 1150° C. for 2 to 10 hours. The step of sintering the template sheet is performed at 1000° C. for 10 hours.

In the step of adding a plurality of BaTiO ₃ seed layer to the slurry, the BaTiO ₃ seed layer is added to or less than 0 1 wt%, and preferably is added at a 0.3 to 1 wt%, more preferably from 0.5 wt% is added with

The BiScO ₃ -PbTiO ₃ base material powder is calcined at 660°C to 725°C.

The polycrystalline BiScO ₃ -PbTiO _{3 piezoelectric material including the BaTiO 3} seed layer prepared by the method of controlling the crystal orientation of _{polycrystalline BiScO 3} -PbTiO ₃ using the BaTiO ₃ seed layer of the present invention has crystal orientation, and the Curie temperature is above 400°C.

The polycrystalline BiScO ₃ -PbTiO ₃ is represented by xBiScO ₃ -(1-x)PbTiO ₃ , wherein x satisfies 0.3≤x≤0.4, preferably 0.34≤x≤0.38, and most preferably x is It is 0.36.

The BaTiO ₃ is contained in an amount greater than 0 and 1 wt% or less, preferably in an amount of 0.3 to 1 wt%, and most preferably in an amount of 0.5 wt%.

According to the present invention, by aligning the crystal grains of the polycrystalline piezoelectric material in one direction to provide a polycrystalline piezoelectric material having a domain alignment structure similar to that of a single crystal, a piezoelectric material with piezoelectric properties close to that of single crystal piezoelectric ceramics and mechanical properties with much superior strength than single crystals. to provide.

1 is a flowchart illustrating a method for controlling crystal orientation of polycrystalline BiScO ₃ -PbTiO _{3 using a BaTiO 3} seed layer according to an embodiment of the present invention.
Figure 2 shows the overall process diagram according to the manufacturing method of the present invention.
Figure 3 shows the appearance of the change in the thickness of the template sheet according to the relational expression regarding the height of the blade.
FIG. 4 shows a process of manufacturing a laminate body by laminating a polycrystalline BiScO ₃ -PbTiO _{3 piezoelectric material including a BaTiO 3} seed layer prepared according to an embodiment of the present invention.
5 shows the slurry batch conditions used in Example 1 of the present invention.
6 is a graph showing the piezoelectric properties of the piezoelectric composition prepared according to Example 1 of the present invention.
7 shows a microstructure schematic diagram of a single crystal piezoelectric ceramic, a polycrystalline grain oriented piezoelectric ceramic of the present invention, and a general polycrystalline piezoelectric ceramic.
8 shows XRD data after synthesizing _{the BiScO 3} -PbTiO ₃ base material powder while varying the calcination temperature conditions.
9a to 9c are SEM images of sintering the _{BiScO 3} -PbTiO _{3 base material powder at different calcination temperatures.}
10 is an enlarged image of the image of FIG. 9B.
11 is a graph of observing the piezoelectric properties when _{the BiScO 3} -PbTiO ₃ base material powder having different calcination temperatures is sintered.
BRIEF DESCRIPTION OF THE DRAWINGS Various embodiments are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In this specification for purposes of explanation, various descriptions are presented to provide an understanding of the present invention. However, it is apparent that these embodiments may be practiced without these specific descriptions. In other instances, well-known structures and devices are presented in block diagram form in order to facilitate describing the embodiments.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Since the present invention can have various changes and can have various forms, 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 the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. In describing each figure, like reference numerals have been used for like elements.

The terms used in the present application are used only to describe specific embodiments and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, step, operation, component, part, or combination thereof described in the specification is present, and includes one or more other features or steps. , it should be understood that it does not preclude the possibility of the existence or addition of , operation, components, parts, or combinations thereof.

The present invention relates to a piezoelectric material with improved piezoelectric properties.

In order to manufacture a piezoelectric material with improved piezoelectric properties of the present invention, the crystal orientation of polycrystalline BiScO ₃ -PbTiO _{3 using a BaTiO 3 seed layer is controlled.}

According to the present invention, by aligning the crystal grains of the polycrystalline piezoelectric material in one direction to provide a polycrystalline piezoelectric material having a domain alignment structure similar to that of a single crystal, a piezoelectric material with piezoelectric properties close to that of single crystal piezoelectric ceramics and mechanical properties with much superior strength than single crystals. to provide.

The characteristic value of the piezoelectric material is determined by the chemical composition, which is an intrinsic characteristic, but may also vary greatly depending on the structure of the crystal grain or the structure of the piezoelectric domain. Accordingly, a study on improving the characteristic value using a grain engineering or domain engineering technique was made in the present invention.

The technology of the present invention is an innovative technology that can improve the piezoelectric properties by 1.5 to 2 times or more compared to the existing polycrystalline piezoelectric material by aligning the crystal grains of the polycrystalline piezoelectric material in one direction to create a domain-aligned structure similar to a single crystal.

In addition, since the piezoelectric material produced in this way is polycrystalline like general bulk ceramic materials, its strength is far superior to that of the fragile piezoelectric single crystal, and the piezoelectric performance shows characteristics similar to that of single crystal. At the same time, it has the advantage of being able to replace it. 7 shows a microstructure schematic diagram of a single crystal piezoelectric ceramic after poling, a polycrystalline grain oriented piezoelectric ceramic of the present invention, and a general polycrystalline piezoelectric ceramic.

1 is a flowchart illustrating a method for controlling crystal orientation of polycrystalline BiScO ₃ -PbTiO _{3 using a BaTiO 3} seed layer according to an embodiment of the present invention. Figure 2 shows the overall process diagram according to the manufacturing method of the present invention.

As shown in FIG. 1 , the method for controlling the crystal orientation of polycrystalline BiScO ₃ -PbTiO _{3 using a BaTiO 3} seed layer according to an embodiment of the present invention _{includes preparing a slurry including a BiScO 3} -PbTiO ₃ base material powder and ball milling. performing (S 110); adding a plurality of BaTiO ₃ seed layers to the slurry (S 120); manufacturing a template sheet using the slurry using a tape casting process (S 130); and sintering the template sheet (S 140).

In step S 110, BiScO ₃ -PbTiO ₃ A slurry including a base material powder is prepared and ball milling is performed. Ball milling of the slurry is carried out in ethanol solvent for 4 to 24 hours. It is common to perform ball milling using zirconia balls of various sizes, but is not limited thereto.

In step S 120, a plurality of BaTiO ₃ seed layers are added to the slurry. A BaTiO ₃ seed layer is added to the slurry and mixed for 12 to 24 hours under an ethanol solvent. The BaTiO ₃ seed layer is in the form of a thin film sheet and is manufactured separately. Preparation of the BaTiO ₃ seed layer, etc. will be described in detail in the following examples.

On the other hand, a plurality of BaTiO ₃ seed layers added in step S 120 are used having the same crystal orientation.

BaTiO ₃ seed layer in the step of adding a plurality of BaTiO ₃ seed layer to the slurry is added to or less than 0 1 wt%, BaTiO ₃ seed layer and more preferably is added at from 0.3 to 1 wt%, and most preferably The BaTiO ₃ seed layer is added at 0.5 wt%. This part will be described in more detail in the following examples.

In step S 130 , a template sheet is manufactured using a tape casting process for the slurry. As shown in FIG. 2 , a template sheet is manufactured using the slurry 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 has the same crystal orientation within the template sheet. are placed 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 this control, when the BaTiO ₃ seed layer exits the blade, it is arranged so that it is all flat and oriented in the same direction so that it can exit, which can be confirmed in FIG. 2 .

Specifically, the height of the blade is determined by the following relational expression.

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

값은 3 이하인 것이 바람직한데, 그 의미는 블레이드의 높이가 씨드 크기의 3배 이하임을 의미한다.Figure 3 shows the appearance of the change in the thickness of the template sheet according to the relational expression regarding the height of the blade. Specifically, as can be seen in Figure 3,

A value of 3 or less is preferred, meaning that the blade height is not more than 3 times the seed size.

For example, a piezoelectric slurry in which BT seeds are uniformly dispersed is coated on a carrier film with a constant thickness by a doctor blade and passed through a drying furnace divided into a total of 4 sections of 0°C, 25°C, 45°C, and 60°C to pass through various organic materials. After volatilizing, it is produced in the form of a roll at the end of the equipment. In order for the BT seeds to align in one direction past the doctor blade to produce a uniform piezoelectric sheet, the doctor blade gap adjustment is essential. If the blade gap is too narrow, defects such as line-shaped spots on the sheet are likely to occur, and if the blade gap is too wide, the seeds will not align properly in one direction even if they pass the blade. Therefore, for example, when using a BT seed with a size of about 10 μm, set the gap of the doctor blade in the range of about 20 to 30 μm, which is 2 to 3 times the size of the seed, and cast. The variable Π representing the ratio between the pressure driving force and the slurry driving force in this tape casting process is expressed as the above equation. According to this formula, a uniformly aligned sheet can be finally obtained by adjusting 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 950 to 1150° C. for 2 to 10 hours, preferably at 1000° C. for 10 hours.

This invention example in BaTiO ₃ seed layer of polycrystalline BiScO ₃ -PbTiO ₃ polycrystalline BiScO prepared using the method of controlling the crystal orientation of the _third accordance with the -PbTiO ₃ is BaTiO ₃ BiScO polycrystalline seed layer by ₃ -PbTiO ₃ is aligned along the crystal direction of the _{BaTiO 3 seed layer.} That is, the polycrystalline BiScO ₃ -PbTiO _{3 piezoelectric material including the BaTiO 3} seed layer prepared by the method of the present invention has crystal orientation.

In the polycrystalline BiScO ₃ -PbTiO _{3 piezoelectric material including the BaTiO 3} seed layer according to an embodiment of the present invention, the polycrystalline BiScO ₃ -PbTiO ₃ is represented by xBiScO ₃ -(1-x)PbTiO ₃ , and x is 0.34≤x ≤0.38. Preferably x is 0.36.

In addition, in the polycrystalline BiScO ₃ -PbTiO ₃ piezoelectric material _{including the BaTiO 3} seed layer according to an embodiment of the present invention _{, BaTiO 3} is contained in an amount greater than 0 and 1 wt% or less, preferably BaTiO ₃ is 0.3 to 1 wt% and, most preferably, BaTiO ₃ is contained in 0.5 wt%. This will be further described in the following examples.

The polycrystalline BiScO ₃ -PbTiO ₃ piezoelectric material prepared according to the method of the present invention _{and including a BaTiO 3} seed layer having crystal orientation can be used for applications exhibiting various piezoelectric properties such as ultrasonic transducers. FIG. 4 shows a process of manufacturing a laminate body by laminating a polycrystalline BiScO ₃ -PbTiO _{3 piezoelectric material including a BaTiO 3} seed layer prepared according to an embodiment of the present invention.

Hereinafter, the content of the present invention will be further described along with specific examples.

The first used slurry batch conditions are shown in FIG. 5 . 5 shows the slurry batch conditions used in Example 1 of the present invention.

1) Synthesis of plate-shaped Bi ₄ Ti ₃ O ₁₂ (BiT)

Molten Salt Synthesis was used to synthesize the Bi ₄ Ti ₃ O _{12 template particles.} The raw materials used were Bi ₂ O ₃ (purity 99.99%, Kojundo Chemical Laboratory, Japan), TiO ₂ (purity 99.9%, Sigma-Aldrich, USA), NaCl (purity 99.5%, Sigma-Aldrich, USA). First, Bi ₂ O ₃ and TiO ₂ were weighed according to the molecular weight, and NaCl was put into a polyethylene bottle at a weight ratio of 1:1 to powder. Then, ethanol (purity 99.5%, Samchun Pure Chemical, Korea) and zirconia balls (Φ = 3 mm, 5 mm, 10 mm) were additionally added, pulverized and mixed for 24 hours, and then dried in an oven at 120 °C. The dried powder was placed in a sealed alumina crucible, heated at a rate of 5°C per minute, maintained at 1100°C for 2 hours, and then cooled naturally. After the synthesis of Bi ₄ Ti ₃ O ₁₂ , the salt was washed with distilled water heated to 80 °C. Washing was carried out using AgNO ₃ solution until no salt was detected.

2) Synthesis of plate-shaped BaTiO ₃ (BT)

In order to synthesize the plate-shaped BaTiO ₃ , a TMC (Topochemical Microcrystal Conversion) method was used. The raw materials used were BaCO ₃ (purtiy 99.95%, Kojundo Chemical Laboratory, Japan), HNO ₃ (purity 70%, Daejung Chemical and metals, Korea). The BiT template particles and BaCO ₃ prepared above were weighed according to the molecular weight, and NaCl was added to the powder and weight ratio of 1:1 with ethanol in a polyethylene bottle. In order to maintain the plate shape of the BiT template particles, the mixture was mixed for 24 hours without adding zirconia balls, and then dried in an oven at 120 °C. The dried powder was placed in an alumina crucible, heated at a rate of 5 °C per minute, maintained at 1020 °C for 3 hours, and then cooled naturally. After the heat treatment, BaTiO ₃ was washed with distilled water at 80 °C _{using AgNO 3} solution until no salt was detected. _{And after washing residual Bi 2} O ₃ and BaCO ₃ with 6M HNO ₃ aqueous solution, the remaining acid was washed again with distilled water at 80 °C.

3) 0.36BiScO ₃ -0.64PBTiO ₃ Ceramic powder manufacturing

0.36BiScO ₃ -0.64PbTiO _{3 A} solid-state reaction method was used to prepare ceramic powder. The raw materials used were Bi ₂ O ₃ (99.99%, Kojundo Chemical Laboratory, Japan), Sc ₂ O ₃ (purity 99.9%, Kojundo Chemical Laboratory, Japan), PbO (purity 99.9%, Sigma-Aldrich, USA), TiO ₂ (purity 99.9%, Sigma-Aldrich, USA). Bi ₂ O _3, Sc ₂ O ₃ , PbO, TiO ₂ were weighed according to the molecular weight, and ethanol and zirconia balls (Φ= 1 mm, 3 mm, 5 mm, 10 mm) were put together in a polyethylene bottle for 24 hours. After grinding and mixing, it was dried in an oven at 120 °C. The dried powder was placed in a sealed alumina crucible, heated at a rate of 5°C per minute, maintained at 700°C for 4 hours, and then cooled naturally. After the calcined powder was put into a polyethylene bottle, zirconia balls ((Φ = 1 mm, 3 mm, 5 mm, 10 mm) and ethanol were put and pulverized for 48 hours, and then dried in an oven at 120°C. The powder was sieved through a sieve (150 μm).

4) 0.36BiScO ₃ -0.64PBTiO ₃ -x wt % BaTiO ₃ Piezoelectric thick film device manufacturing

0.36BiScO ₃ -0.64PBTiO ₃ -x wt % BaTiO ₃ A tape casting process generally used for manufacturing a piezoelectric thick film device was used. To prepare a slurry for tape casting, BS-PT ceramic powder, ethanol (purity 99.5%, Samchun Pure Chemical, Korea), toluene (purity 99.5%, Samchun Pure Chemical, Korea), polyvinyl butyral (BM-SZ, Sekisui, Japan) ), dibutyl phthalate (purity 99.0%, Daejung Chemical, Korea) and a dispersant (BYK-111, BYK-Chemie GmbH, Germany) were mixed in an optimal ratio. The mixed slurry was put into a polyethylene bottle, and after pulverizing and mixing with zirconia balls (Φ=3 mm, 5 mm, 10 mm, 15 mm) for 24 hours, the mixed slurry was uniformly distributed using a mesh. sifted vigorously. Then, using a vacuum degassing machine, bubbles were removed from the inside of the slurry at a vacuum degree of ~760 mmHg for 20 minutes. Plate-shaped BT 0, 0.5, 1, 2, 4, 8 wt %, ethanol and a dispersant were put in a vial, dispersed with a sonicator, and then added to the prepared slurry. The BT-added slurry was aged at about 10 rpm for 4 hours. A green sheet with a thickness of about 30 μm was prepared from the aged slurry using a tape casting equipment (TCA-2000, Techgen, Korea) with a doctor blade. An electrode to be used as an external electrode was screen-printed on the produced green sheet, and Ag-Pd paste (WT-SPD30-A, Winner Technology, Korea) was used for the simultaneous firing of the electrode. A total of 11 green sheets were laminated using a laminator (Keko, Slovenia) at 60° C. under a pressure of 13 MPa, and electrodes were positioned at the top and bottom of the thick film device. Then, warm isostatic pressing (WIP) was performed at 65° C. for 20 minutes at a pressure of 20 MPa, and the WIP-completed piezoelectric thick film device was cut to 1 cm x 1 cm to complete device fabrication. The fabricated device was heated to 300 °C at 2 °C per minute and held for 1 hour, then heated to 600 °C at 2 °C per minute and held for 1 hour, then heated to 1000 °C at 2 °C per minute and maintained for 10 hours, and then maintained at 850 °C at 2 °C per minute. After cooling, natural cooling was performed. The sintered piezoelectric thick film device was subjected to air poling for 10 minutes at room temperature with an electric field of 3.5 kV/mm.

When synthesizing using the method of Example 1, BiScO ₃ -PbTiO ₃ Physical properties according to the synthesis temperature of the base material powder were confirmed.

BiScO ₃ -PbTiO _{3 The} base material powder is calcined to confirm phase synthesis, and then ball milling is performed as in the step of Example 1, followed by sintering.

8 shows XRD data after synthesizing _{the BiScO 3} -PbTiO ₃ base material powder while varying the calcination temperature conditions.

As shown in FIG. 8 , it was confirmed that a secondary phase such _{as Bi 12} PbO ₁₉ as shown in a rectangular display was formed at a temperature of 660° C. to 725° C. where the calcination temperature was low. Calcination was carried out for 4 hours while changing the temperature to 660 °C to 825 °C.

9a to 9c are SEM images of sintering the _{BiScO 3} -PbTiO _{3 base material powder at different calcination temperatures.} Sintering was carried out at 1000° C. for 2 hours, and the specimen was sintered in the form of a disk. All secondary phases disappeared by sintering at 1000° C. and perovskite crystals were formed. At this time, FIG. 9a is sintered using the base material powder calcined at 660°C, FIG. 9b is sintered using the base material powder calcined at 700°C, and FIG. 9c is sintered using the base material powder calcined at 750°C. As can be seen in FIGS. 9a to 9c , when sintering using the base material powder calcined in the temperature range of 660 ° C to 725 ° C, which is the range of the calcination temperature of the present invention, the calcination temperature is higher using the base material powder of 750 ° C. It was confirmed that the grain size was larger than that of the sintered one. That is, it was confirmed that the grain growth was better. The reason is that when the image of FIG. 9b is enlarged as shown in FIG. 10, it can be confirmed that a liquid phase is formed between the grains and the grains as shown by the arrow, and this liquid phase is calcined at 660 ° C. to 725 ° C. It is caused by the melting of the secondary phase of the calcined base material powder in the temperature range, and BiScO ₃ -PbTiO ₃ grains are further grown during sintering by this liquid phase. Therefore, from these results, it was found that BiScO ₃ -PbTiO _{3 affects the growth of BiScO 3} -PbTiO ₃ grains according to the calcination temperature conditions (660° C. to 725° C.) of the base material powder, and eventually affects the physical properties of the piezoelectric material. , which can be confirmed from the piezoelectric characteristic graph of FIG. 11 .

Looking at the graph of FIG. 11 _{, d 33} and k _{p, which} are important piezoelectric property factors when using the base powder calcined under the calcination temperature condition (660° C. to 725° C.) of the _{BiScO 3} -PbTiO ₃ base powder, are low despite the low calcination temperature was found to be high. This is a very important result confirming that the base material powder having a low calcination temperature can exhibit higher piezoelectric properties, and it can be seen that the calcination temperature condition is a very significant condition. 11, a more preferable calcination temperature is 680°C to 725°C, and most preferably 700°C.

6 is a graph showing the piezoelectric properties of the piezoelectric composition prepared according to Example 1 of the present invention. As a graph for 0.36BiScO ₃ -0.64PBTiO ₃ -x wt % BaTiO ₃ (ball mill 4 hours, calcination temperature at 700° C. for 4 hours, sintering temperature at 1100° C. for 10 hours), piezoelectricity according to the content of _{BaTiO 3} indicates a change in characteristics.

As shown in FIG. 6 , it _{was confirmed that the piezoelectric properties were very well exhibited when the content of BaTiO 3} was greater than 0 and 1 wt% or less, preferably 0.3 to 1 wt%, and more preferably 0.5 wt%. In FIG. 6, d ₃₃ (piezoelectric displacement coefficient) means the magnitude of the amount of charge generated when a constant stress is applied or the strain generated when a constant electric field is applied, and k _p (electromechanical coupling coefficient) is from mechanical energy to electrical energy. means the conversion efficiency of or the conversion efficiency from electrical energy to mechanical energy, g ₃₃ (piezoelectric voltage coefficient) means the magnitude of the voltage generated when a certain stress is applied, and Q _m (mechanical quality factor) is the electric machine It refers to the measure of energy loss in the conversion process, and d ₃₃ (piezoelectric displacement coefficient) refers to the magnitude of the electric charge generated when a constant stress is applied or the strain generated when a constant electric field is applied.

Combining the contents of Examples 2 and 3, the present invention uses the base material powder calcined at 660 ° C. to 725 ° C. under the conditions of the calcination temperature of the base material powder in using the _{BiScO 3} -PbTiO _{3 base material powder.} After preparing the slurry and performing ball milling, a plurality of BaTiO ₃ seed layers are added thereto, and a template sheet is manufactured and sintered. In this case, the BaTiO ₃ content is preferably controlled to be greater than 0 and less than 1 wt% do.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the following claims. You will understand that you can.

Claims (21)

BiScO ₃ -PbTiO ₃ Preparing a slurry including a base material powder 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;
BaTiO ₃ seed layer on the polycrystalline BiScO ₃ -PbTiO ₃ by the aligned along the crystal orientation of the seed layer BaTiO _3,
The BaTiO ₃ seed layer in the step of adding a plurality of BaTiO ₃ seed layer to the slurry is added in at least 0.3wt% less than 0.5 wt%,
The BiScO ₃ -PbTiO ₃ base material powder uses a powder calcined at 660 ℃ to 725 ℃,
In the step of manufacturing the template sheet using the slurry using the tape casting process, the height of the blade of the tape casting apparatus is controlled _{to ensure that all of the BaTiO 3} seed layers in the form of a thin film have the same crystal orientation in the template sheet. and the height of the blade is controlled to be higher than the thickness perpendicular to the plane of _{the BaTiO 3 seed layer,}
Method for controlling crystal orientation of polycrystalline BiScO ₃ -PbTiO ₃ using a BaTiO _{3 seed layer.}
delete The method of claim 1,
The step of adding a _{BaTiO 3} seed layer to the slurry,
_{A BaTiO 3} seed layer is added to the slurry and mixed for 12 to 24 hours under an ethanol solvent,
Method for controlling crystal orientation of polycrystalline BiScO ₃ -PbTiO ₃ using a BaTiO _{3 seed layer.}
delete delete delete delete delete delete delete delete delete delete Prepared according to the method of claim 1 or 3,
has crystal orientation,
The Curie temperature is 400°C or higher,
Polycrystalline BiScO ₃ -PbTiO ₃ piezoelectric material with BaTiO _{3 seed layer.}
15. The method of claim 14,
The polycrystalline BiScO ₃ -PbTiO ₃ is represented by xBiScO ₃ -(1-x)PbTiO ₃ ,
Wherein x satisfies 0.3≤x≤0.4,
Polycrystalline BiScO ₃ -PbTiO ₃ piezoelectric material with BaTiO _{3 seed layer.}
delete 16. The method of claim 15,
wherein x is 0.36;
Polycrystalline BiScO ₃ -PbTiO ₃ piezoelectric material with BaTiO _{3 seed layer.}
delete delete delete A polycrystalline BiScO ₃ -PbTiO ₃ piezoelectric material _{including a BaTiO 3} seed layer, which is prepared according to the method of claim 1 or 3, has crystal orientation, and has a Curie temperature of 400° C. or higher,
ultrasonic transducer.

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